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The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes
Accepted Manuscript Research paper The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes Pinar Sen, S. Zeki Yildiz PII: DOI: Reference:
S0020-1693(16)30614-4 http://dx.doi.org/10.1016/j.ica.2017.02.030 ICA 17456
To appear in:
Inorganica Chimica Acta
Received Date: Revised Date: Accepted Date:
27 September 2016 22 February 2017 24 February 2017
Please cite this article as: P. Sen, S.Z. Yildiz, The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes, Inorganica Chimica Acta (2017), doi: http:// dx.doi.org/10.1016/j.ica.2017.02.030
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The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes
Pinar Sena, S. Zeki Yildiza* a
Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, 54187, Sakarya, Turkey
Abstract This study covers the functional complexes of tetrakis [4-(salicyhydrazone)phenoxy)] phthalocyaninato cobalt (II) (5) which was the macro molecular Schiff base ligand and synthesized through a multistep reaction sequence starting first with the cyclotetramerization of 4-[4-(1,3-Dioxolan-2-yl)phenoxy]-phthalonitrile (2). Then, the de-protection of tetra acetal groups of Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninato cobalt (II) (3) to the aldehyde
functionality
in
acetic
formylphenoxy)phthalocyaninato
acid/FeCl3
cobalt(II)
(4)
system and
to
then
yield its
the
Tetrakis(4-
condensation
with
salicylhydrazide gave to 5. Finally, CoPc-bis(salicyhydrazone)phenoxy)manganese (III) (6), CoPc-bis(salicyhydrazone) phenoxy)cobalt(III) (7) and CoPc-bis (salicyhydrazone)phenoxy) nickel(II) (8) were synthesized using with the related MnCl2.4H2O, CoCl2.6H2O, Ni(CH3COO)2 salt in basic conditions in DMF. FT-IR, UV-Vis, MS spectra and elemental analysis were applied to characterize to prepared compounds. The bleaching performances of the prepared phthalocyanine compounds (3-8) were examined by the degradation of Morin as the hydrophilic dye which characterized the wine stains on the fabrics. Progress of the degradations in the catalysts (3-8)/H2O2 combination in basic aqueous solution conditions was investigated by using online spectrophotometric method (OSM). It was found that the prepared catalysts showed better bleaching performance at 25 °C than to that of tetraacetylethylenediamine (TAED) bleach activator commercially used in powder detergent formulations.
Keywords: Synthesis, metalo phtalocyanine, Schiff base, metal complex, bleach catalyst. *Corresponding Author, E-mail address: [email protected], Fax: +90 (264) 295 68 25
1. Introduction Phthalocyanines (Pcs) as synthetic porphyrin analogues are considered
for excellent
functional materials and attractive molecular building blocks due to their unique optical, physicochemical, electronic, catalytic and structural properties [1-2]. Because of having potential applications, they have been studied extensively in many areas such as material science, non-linear optics and liquid crystals [3]. One of the attractive targets in phthalocyanine chemistry is the generation of new functional molecular materials for catalytic applications, as well. Metallo-Pcs which contain redox active metals having wide range of oxidation states are preferred as the oxidation catalysts [4]. Metallophthalocyanines (MPcs) can be tuned for the targeted catalytic aim by changing the central metal ion. For the oxidation of olefins, alcohols, aromatics and some other compounds, MPcs received considerable attention as potential catalysts having exceptional catalytic properties [5]. Especially, cobaltphthalocyanines have been employed in oxidation reactions because of their high catalytic activities [6, 7]. Introducing additional functional groups onto the phthalocyanine skeleton are also of great importance for the development of further chemical reactions on Pc macrocycles in order to increase the functionalities and reach the desired properties [8-10]. Phthalocyanines containing reactive functional groups such as crown ethers, macrocyclic amines and other chelating moieties, having rich electron-donor atoms to coordinate metal ions have been interesting target for the chemists for desiging new molecular materials [11]. Several different approaches in designing polynucleating phthalocyanines have emerged. In a recent study, Schiff base moieties and its Zn complexes attached to the phthalocyanine core were prepared starting from an amine substituted Zn phthalocyanine and the fluorescence properties of the prepared complexes have been examined [12].
Schiff base chemistry is a versatile tool in organic synthesis, and especially have played an important role in the development of coordination chemistry because of forming complexes with most transition metals. In our strategy for the design of multi metallic systems involving the Schiff base metal complexes as substituents attached to metallo-phthalocyanine compounds, aldehyde substituted CoPc was used as the precursor. The prepared CoPcs and their Schiff base metal complex substituted multi metallic derivatives were examined as bleach catalysts to activate H2O2 at lower temperatures. The bleach catalysts are actually oxidation catalysts. Oxidation reactions are of great importance in the chemical industry. Hydrogen peroxide is used as potent oxidant frequently [13]. Based on bleach catalyst, hydrogen peroxide may play a major role for the pulp and paper production, waste water treatment and laundry for industrial and domestic applications [14]. Bleach processes carry out through oxidative mechanisms by the degradation of chromophores in to the water-soluble products. The oxidative bleach provides a two-step cleaning effect in laundry applications. The first step which can be called as conversion is the disappearance of the color of stains due to the oxidation of the π-system, than the second one is degradation step which provides to removal of the stains from the surface as the water soluble products. So far, several novel transition metal complexes of salen, saltren, terpyridine-type ligands and triazole derivatives possessing significant potential in activation of hydrogen peroxide have been synthesized as bleach catalysts and tested [15]. These results promoted us to develop new transition-metal catalyst candidates containing phthalocyanine molecules for laundry bleaching applications. In our study, a series of Co-phthalocyanine complexes having two substituted Schiff base Mn(III), Co(III) and Ni(II) complexes directly linked through oxygen bridges to the phthalocyanine core were synthesized and characterized as the new bleach catalysts class. We examined the performance of the prepared catalysts on bleach oxidation at room temperature in the presence
of H2O2 by online spectrophotometric method [16]. In the recent studies performed by our group, the zinc-phthalocyanines having two Co(III), Mn(III) and Fe(III) complexes directly linked through oxygen bridges to the core were synthesized and examined for the purpose [17, 18]. To our knowledge, no such molecule having complex moiety as the substituent on CoPc ring has been obtained and used as bleach catalyst, so far.
2. Experimental 2.1. Chemicals and instruments The following chemicals were obtained from Sigma-Aldrich; Methanol (MeOH), ethanol (EtOH), diethylether, MnCl2.4H2O, Co(CH3COO)2, CoCl2.6H2O, NiCl2, FeCl3, LiCl, Morin hydrate,
potassium
hydroxide
(KOH),
1,8-Diazabicyclo[5.4.0]undec-7-ene
(DBU),
Tetrahydrofuran (THF), Chloroform (CHCl3), Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO) and Dimethylacetamide (DMAc). Hydrogen peroxide was used as industrial grade (50%). All other reagents and solvents were reagent grade quality and obtained from commercial suppliers. All solvents were stored over molecular sieves (4A°) after they dried and purified as described by Perrin and Armarego [19]. Oxygen free inert atmosphere was supplied by argon through dual-bank vacuum-gas manifold system. Deionized water was generated from MILLIPORE ultra-pure water supply system. ThinLayer chromatography (TLC) was performed using silica gel 60-HF254 as an adsorbent. Melting points (m.p.) were determined using a Barnstad-Electrotermel 9200 apparatus and are uncorrected. Electronic spectra were recorded on a Shimadzu UV-2600 Pc-spectrophotometer with quartz cell of 1 cm. Infrared spectra were recorded on a Perkin Elmer Spectrum two FTIR spectrophotometer equipped with Perkin Elmer UATR-TWO diamond ATR and corrected by applying the atr-correction function of Perkin Elmer Spectrum software. For Maldi-TOF spectra, the experiments were carried out using a Bruker microTOF (Germany) in Gebze
Institute of Technology. The compounds were ionized in the positive electro-spray ionization ion source (ESI+) of the mass-spectrometer. The elemental compositions of the samples were analyzed by an element analyzer (Flash 2000, Thermo Scientific). Compounds 6–8 were digested using HNO3 at 170 °C for 1 h. The manganese, cobalt and nickel contents of 6–8 in the digested mixture were determined using an external standard with a Spectro Arcos inductively coupled plasma optical emission spectroscopy (ICP-OES) instrument (Spectro, Kleve, Germany).
2.2. Synthesis 2.2.1 4-[4-(1,3-Dioxolan-2-yl)phenoxy]-phthalonitrile (2) The preparation of 1 has been performed in two steps. 4-nitrophthalonitrile was reacted at first with p-hydroxybenzaldehyde to give the 4-(4-formylphenoxy)phthalonitrile within 96% yield [20]. In the second step, the 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile was obtained for the protecting of aldehyde group with ethylene glycol by applying the our published literature procedure [21]. The obtained spectroscopic data are accordance with the literature [22].
2.2.2 Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninato cobalt (II) (3) In a standard schlenk tube, 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (0.270 gr, 0.92 mmol) (1), Co(CH3COO)2 (0.082 gr, 0.46 mmol) and DBU (couple drops) was dissolved in npentanol (2.5 mL). The reaction mixture was purged by argon at room temperature and heated up to 140 °C for 12h. After cooling to room temperature, the reaction mixture was precipitated by adding methanol/water (15:15 v/v). The precipitated was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Further purification of the phthalocyanine
was performed by size exclusion chromatography on Bio-beads gel (SX-1). The crude product was put onto the column and eluted with CHCl3 and the collected phases were concentrated on a rotary evaporator and re-precipitated with methanol. The desired pure CoPc (3) was obtained as a green solid. Yield 0.250 g, 88%. m.p> 250 °C. FT-IR (UATR-TWOTM) ν max/cm-1 : 3060 (Ar, C-H), 2949, 2882 (Alip, C-H), 1601, 1505 (C=C), 1469-1386 (C-C), 1227 (Ar-O-Ar), 1078, 1014, 941,825. UV–Vis (DMF): λmax (nm) (log ε) 665 (4.66), 604 (4.12), 459 (3.83), 330 (4.65). MS (MALDI-TOF): m/z 1228.56 [M]+. Anal. Calc. for C68H48CoN8O12 (%): C, 66.50; H, 3.94; N, 9.12; O,15.63; Found (%): C, 66.24; H, 4.02; N, 8.97.
2.2.3. Tetrakis(4-formylphenoxy)phthalocyaninato cobalt(II) (4) The cleavage reaction of 3 (225 mg, 0.183 mmol) was performed in acetic acid ( ̴ 5 mL) / FeCl3 (catalytic amount) system using THF (5 mL) to solve the phthalocyanine before adding cleavage regents. The reaction solution was stirred at room temperature for 1d. The resulting mixture was precipitated with water and the precipitate was collected by centrifugation. The crude product was washed several times with ethanol and water to remove any unwanted organic impurity and acidic residue and then it was dried under vacuum. Further purification of the prepared phthalocyanine was performed by size exclusion chromatography on Biobeads gel (SX-1) using CHCl3 as the eluent. The desired pure product 4 was collected by the re-precipitation with methanol after rotary evaporation of the collected organic eluent phases as blue-green solid. Yield 150 mg, 58 %. m.p > 250 °C. FT-IR (UATR-TWO™) ν max/cm-1: 3182-3060 (Ar, C-H), 2846-2734 (O=C-H), 1693 (-C=O), 1592-1501 (C=C), 1467-1384 (CC), 1226 (Ar-O-Ar), 1153, 1088, 828.UV–Vis (DMF): λmax (nm) (log ε) 662 (4.63), 601 (4.04), 458 (3.45), 329 (4.64). MS (MALDI-TOF): m/z 1341 [M+Matrix+2Na+H2O]+. Anal.
Calc. for C60H32CoN8O8 (%) : C, 68.51; H, 3.07; N, 10.65; O,12.17; Found (%): C, 68.32; H, 3.29; N, 10.76.
2.2.4. Tetrakis [4-(salicyhydrazone)phenoxy)]phthalocyaninato cobalt(II) (5) A solution of salicylhydrazine (96 mg, 0.63 mmol) in dry THF (10 mL) was added to a solution of tetrakis[(4-formylphenoxy)-phthalocyaninato]cobalt(II) (4) (200 mg, 0.122 mmol) in THF (10 mL) and the mixture was heated up to 70 °C for 12h. After cooling to room temperature, the solvent was evaporated to 1/10 of the initial volume of the reaction mixture, and then it was precipitated by adding methanol/water (v/v: 1/1). The crude product was collected by filtration as green solid and washed successively with cold water, methanol and ethanol to remove the un-reacted starting materials and dried in vacuo. Yield 0.250 g, 82 %. m.p > 250 °C.FT-IR (UATR-TWO™) ν max/cm-1: 3209 (N-H), 3063-2168 (O-H…..N), 1643 (C=O), 1597 (C=N), 1552 (C=C), 1489-1350 (C-C), 1231 (Ar-O-Ar), 1161, 1093, 752.UV– Vis (DMF): λmax (nm) (log ε) 666 (4.59), 600 (4.14), 326 (5.09). MS (MALDI-TOF): m/z 1229
[M-(C14H11N2O2,
C7H5O2)]+ (in
supporting
information).
Anal.
Calc.
for
C88H56CoN16O12 (%) : C, 66.54; H, 3.55; N, 14.11; O,12.09; Found (%): C, 66.17; H, 3.82; N, 14.18.
2.2.5. Bis [bis (salicyhydrazone)phenoxy)manganese(III)]phthalocyaninatocobalt(II) (6) Compound 5 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, MnCl2.4H2O (18.43 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. Next, LiCl (4.38 mg, 0.103 mmol) was added and the suspension was heated at 100 oC again for 1 h with air bubble. The reaction mixture was precipitated by adding diethylether
(15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 35 mg, 64%. m.p. > 200°C. FT-IR (UATR-TWO™) ν max/cm-1: 3313 (Ar-OH), 3060 (Ar, C-H), 2953-2842 (AlipH C-H), 1649 (C=N), 1595-1520 (C=C), 1489-1385 (C-C), 1229 (Ar-O-Ar), 1092, 1057, 753. UV–Vis (DMF): λmax (nm) (log ε) 668 (3.66), 610 (2.95), 324 (3.97). MS (MALDI-TOF): m/z 1249 [M-(C14H10N2O3, C7H5NO2, 2Cl)]+ (in supporting information). Anal. Calc. C88H52Cl2CoMn2N16O12 (%) : C, 59.88; H, 2.97; N, 12.70; Cl, 4.02; O, 10.88; Co, 3.34; Mn, 6.22; Found (%): C, 59.38; H, 2.76; N, 12.32; Co, 3.02; Mn,6.82 (ICP-OES) .
2.2.6. Bis [bis (salicyhydrazone)phenoxy)cobalt(III)]phthalocyaninatocobalt(II) (7) Compound 5 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, CoCl2.4H2O (16.4 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. Next, LiCl (4.38 mg, 0.103 mmol) was added and the suspension was heated at 100 oC again for 1 h with air bubble. The reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 40 mg, 71%. m.p. > 200°C. FT-IR (UATR-TWOTM) ν max/cm-1: 3309 (Ar-OH), 3060 (Ar, C-H), 1650 (C=N), 1593-1522 (C=C), 1467-1327 (C-C), 1229 (Ar-O-Ar), 1158, 1092, 1056, 746. UV–Vis (DMF): λmax (nm) (log ε) 675 (3.62), 611 (3.08), 319 (3.8).MS (MALDI-TOF): m/z 1484 [M- C14H10N2O3, Cl]+, 1277.79 [M-2(C14H10N2O3), Cl+2Na] (in supporting information). Anal. Calc. for C88H52Cl2Co 3N16O12 (%) : C, 59.61; H, 2.96; N,
12.64; Cl, 4.00; O,10.83; Co, 9.97; Found (%): C, 59.14; H, 3.08; N, 12.38; Co, 9.68 (ICPOES)
2.2.7. Bis [bis (salicyhydrazone)phenoxy)nickel(II)]phthalocyaninatocobalt(II) (8) Compound 4 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, NiCl2 (8.9 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. The reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 38 mg, 72%. m.p. > 200°C. FT-IR (UATR-TWOTM) ν max/cm-1: 3322 (Ar-OH), 3061 (Ar, C-H), 1593 (C=N), 1521 (C=C), 1489-1365 (C-C), 1230 (Ar-O-Ar), 1161, 1093, 1055, 753. UV–Vis (DMF): λmax (nm) (log ε) 677 (3.88), 609 (3.6), 342 (4.35).MS (MALDI-TOF): m/z 1706.97 [M]+ (in supporting information). Anal. Calc. for C88H52CoN16Ni2O12 (%) : C, 62.11; H, 3.08; N, 13.17; O, 11.28; Co, 3.46; Ni, 6.90; Found (%): C, 61.86; H, 3.25; N, 12.92; Co, 3.22; Ni, 7.03.
2.3. Catalytic bleaching Bleaching process was performed by using online spectrophotometric method to monitor the oxidation of Morin dye [23]. The method used in this study enables in situ following the spectral changes and the determination of the amount of dye bleaching as percentage. Experiments were carried out in a reaction vessel. To the reaction vessel placed on magnetic stirrer was added the required amount of carbonate buffer solution (pH: 10.5), 80 mM morin,
10 µM catalyst and 10 mM hydrogen peroxide for each experiment, respectively. The temperature of solutions was maintained at 25 oC with programmable water bath. A peristaltic pump was used to transfer the solution mixture from the reaction vessel to the flow cell placed in the sample compartment of the UV–vis spectrophotometer. The initial absorbance of morin in buffer solution was measured, and bleaching of morin was followed as the decrease in absorbance at 411 nm. The bleaching reaction was initiated by adding H2O2 into the reaction mixture together with the catalyst. The continuous circulation of the mixture was provided between the reaction vessel and UV–Vis spectrophotometer by the peristaltic pump. The scanning-kinetic measurement program of the software was run to monitor the spectral changes with 5 min. intervals. The absorbance changes were determined by the measurements, and the bleaching percentage was graphed as a function of time. The amount of de-colorization of Morin was expressed as the dye bleaching percentage and calculated by the following Eq. (1) [16].
% =
(1)
Where, A0 and At are the absorbance of morin at time 0 and time t, respectively.
3. Results and discussion 3.1. Synthesis and spectroscopic characterization Scheme 1 shows the synthetic route for the precursor functional phthalocyanines 3 and 4. To be able to syntheses these phthalocyanines, the important starting material is 4-[4-(1,3Dioxolan-2-yl)phenoxy]-phthalonitrile (2) which has been prepared in two steps in this work.
Firstly, 4-nitrophthalonitrile was reacted with p-hydroxybenzaldehyde to give the 4-(4formylphenoxy)phthalonitrile (1) with 96% yield as reported in the literature [20]. For protecting the aldehyde group of 1, 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (2) was obtained in the second step . For this purpose, the literature procedure was slightly modified and catalytic amount of oxalic acid was used instead of p-toluene sulfonic acid [22].
Scheme 1.
The acetal substituted Pc derivative 3 was prepared from the cyclo tetramerization reaction of phthalonitrile 2 with corresponding anhydrous Co(II) salt and in the presence of DBU as a strong base to obtain CoPc 3 in n-pentanol. The purification of 3 was performed by size exclusion chromatography on Bio-beads gel (SX-1) by eluting chloroform. In order to perform the synthesis of the phthalocyanine 4 containing aldehyde functional group, the acetal groups at the peripheral position on phthalocyanine 3 were de-protected in acetic acid/FeCl3.6H2O system by mixing in THF as solvent to enhance the solubility. The
preparation of
salicylhydrazone
substituted
phthalocyanine
5
as
the
macromolecular Schiff base ligand was conducted in THF at reflux temperature by using phthalocyanine 4 and salicylhydrazine as the corresponding aldehyde and amine derivatives, respectively. The complexation of the salicylhdrazone groups on the periphery positions of phthalocyanine 5 to give trinuclear-Pcs was carried out with MnCl2.4H2O for 6, CoCl2.6H2O for 7 and Ni(CH3 COO)2 for 8 in DMF under basic condition as shown in scheme 2. After
completion of the reactions, LiCl was added to the reaction mixtures individually to complete
the manganese and cobalt site with Cl- anions. Oxidation of the Mn(II) and Co(II) to the Mn(III) and Co(III) was achieved by air bubbling.
Scheme 2.
Characterization of the products was carried out by the combination of spectroscopic methods including FT-IR, melting point, UV/Vis and Mass spectroscopy. All the spectral data are in accordance with the proposed structures. The formation of 2 can be recognized from the disappearance of C=O vibration at 1691 cm-1 and the aldehyde C–H vibrations at 2805–2764 cm-1 for compound 1 and the appearance of new absorption bands at 2959-2888 cm-1 and 1083 cm-1 belonging to the aliphatic –C–H and aliphatic –C–O–C– vibrations, respectively. Cyclotetramerization of the dinitrile derivative 2 to the acetal substituted Pc 3 was confirmed by the disappearance of the sharp –C≡N stretching vibration band at 2235 cm-1, as expected. The typical aliphatic –C–H vibrational bands at 2949-2882 cm-1 were assigned to C–H stretching of the acetal groups of 3. The sharp peak at 1693 cm-1 in the FT-IR spectrum of 4 belonging to the C=O stretching vibration is indicative for the cleavage reaction of 3 to the desired aldehyde substituted Pc 4. Furthermore, the peaks in the range of 2846-2734 cm-1 which are attributed as Fermi resonance prove the aldehyde formation, as well. Formation of Schiff base on the periphery of phthalocyanine 4 after treated with salicylhydrazide to give compound 5 was confirmed by the disappearance of the C=O stretching vibration of formyl groups and appearance of –C=N stretching vibration band at
1597 cm-1. However, the –C=O stretching vibration band of combined salicylhydrazone group appeared at 1643 cm-1 proves to keto form and is accordance with the published literature [24]. The N–H vibration of amide nitrogen appeared at 3209 cm-1. Typical O–H…N vibrations appeared as a large distorted band at the range of 3063-2168 cm-1 confirmed that the hydrogen bonding occurred between the –NH– and the phenolic –OH groups of the salicylhydrazone moieties. The FT-IR spectra of 6-8 were interpreted with the comparison of the spectrum of free ligand 5 in which the C=O vibration at 1643 cm-1 disappeared. This indicates that the keto oxygens in the hydrazine groups enolize and deprotonate during complexion with the corresponding metal ions in alkaline conditions. The C=N band at 1597 cm-1 belonging to the ligand molecule (5) shifted to 1649 cm-1 for 6 and 1650 cm-1 for 7, respectively. These upper shifts in the spectra of the complexes are due to chelate formation which makes the complexes more stable and the bonds of ligands located around metal ions stronger. This is also further confirmation for the coordination of the ligands through the azomethine nitrogen and enolate oxygen atoms [17]. The same imine band shifts to lower wavenumber to 1593 cm-1 with respect to free ligand for Ni(II)complex substituted phthalocyanine 8 upon coordination, as well. The 1H- NMR and 13C-NMR spectra of cobalt phthalocyanines 3-8 could not be taken due to the paramagnetic cobalt(II) center. The Mass spectra of 3-8 were obtained by the MALDI-TOF Mass spectrometer confirming the proposed structure. Many different MALDI matrices were tried to find an intense molecular ion peak and low fragmentation under the MALDI-MS conditions for this Pcs. The best matrix for Pc 3 was found to be Dithranol (DIT) with mainly molecular ion peak at m/z: 1228.56 [M]+ as the base peak of spectrum. For compound 4, α-cyano-4-
hydroxycinnamic acid (CHCA) was used to make the molecular ion peaks at m/z: 1240 [M+Matrix+Na]+ visible. In the mass spectrum of 5 obtained without using matrix, molecular ion peak was observed at around m/z: 1590 as a small peak. However, the base peak of the spectrum at m/z: 1229 was attributed to fragment ion peak calculated as [M-(C14H11N2O2, C7H5O2)] +. The observed other fragments were tabulated and given in supporting information in detail.
For the metal complex substituted Pcs (6-8),
sinapic acid (SA), α-cyano-4-
hydroxycinnamic acid (CHCA) and Dithranol (DIT) were used respectively, and the molecular ion peaks at m/z: MS (MALDI-TOF): m/z1249 [M-(C14H10N2O3, C7H5NO2, 2Cl)]+ for 6, 1484 [M-2(C7H5O2, Cl)+Na]+ for 7 and 1706.97 [M]+ for 8 were observed. The structural characterization of these resultant hydrazine complexes showed that the 1/2 ligand/metal ratio is most suitable stoichiometry gave corresponding stable chelate complexes. However, this case depends also on the conditions, such as metal ion, its concentration, the pH of the medium, and the nature of the hydrazone ligand [25]. It is known that in the prepared compounds, the Co (III), Mn (III) and Ni (II) ions at the center of the complexes in the periphery tend to bind co-ligands to the axial positions to reach the octahedral geometry. However, there are some crystallized molecular examples in the literature especially for Mn(III) and Co(III) ions in which the central metal ions have Penta dentate geometry, and these complexes are called as Jacobsen type catalysts [26]. In some cases, the coordinated small molecules such as water and solvents were ignored in the drawing of molecular structres, as well [27]. The elemental analysis results for the synthesized phthalocyanines (3-8) were consistent with the theoretical calculated values given in the experimental section. ICP-OES measurements were also done for the determination of the quantities of Co, Mn and Ni ions included in Pc structures 6–8. The theoretical percentage of cobalt by weight in 6 is 3.34, in 7 is 9.97 and in 8 is 3.46. The experimental results show that the percentages by weight of
cobalt ions are 3.02 for 6, 9.68 for 7 and 3.75 for 8. In a similar way, the theoretical percentage by weight of manganese content in 6 is 6.22 and nickel in 8 is 6.90. From the experiment, as the percentages by weight of Mn(II) and Ni(II) are obtained as 6.82 and 7.03, respectively. Thus, the ICP-OES measurements provide additional support to the proposed molecular structures of 6-8. The ground-state electronic spectroscopy is one of the most useful methods for the determination of structural properties of phthalocyanines. The absorption spectra of phthalocyanines give information about the symmetry of HOMO and LUMO orbitals, isomerization types and aggregation of the molecules. Generally, phthalocyanine compounds display two intense absorption bands in the electronic spectra. One of them is observed in the visible region of spectrum at around 600–700 nm (Q-band) and the other one is in the UV region at around 300–350 nm (B-band), and both of them are correlated to π–π* transitions. Phthalocyanine compounds also exhibit vibronic bands on the blue side of the Q-bands attributed to n–π* transitions [28]. The electronic spectra of the prepared phthalocyanines were recorded in three different solvents (DMAc, DMF and DMSO) to observe the relation between polarity and basicity of the solvents, and the aggregation tendencies were observed for complex 3-8 as seen in Fig. 1.
Fig. 1.
DMAc is the most basic solvent among the used ones and makes more ionic interaction. The solubility of the compounds 4, 6 and 7 increased in DMAc by the decreasing of π–π stacking with the pointed out ionic interaction (Fig. 1b, 1d, 1e). DMSO, which is a
strong coordinating solvent with a high donor number that is able to coordinate to most central metals of porphyrins and phthalocyanines through either the sulfur or the oxygen atoms, normally prevents aggregation [29]. Thus aggregation should be more diminished in DMSO. However, this is not the case in this work for all Pcs. This effect only observed in compounds 3 and 8 (Fig. 1a, 1f). All metalled phthalocyanine complexes 3-8 showed intense Q-absorption band at around 660-680 nm with
no
splitting on them which assigned
that it
was
metallophthalocyanine with the D4h symmetry as expected [30]. Intense Q band absorptions indicate clearly the presence of monomeric species in the solutions. High aggregation tendency of phthalocyanine compounds due to the interactions between their 18 π-electron systems often cause weak solubility, the appearance of broad bands and decrease in intensity as observed for compounds 5-8 (Fig. 1c, 1d, 1e, 1f) [31,32]. Beside of solvent types and the concentration of Pc solutions, the metal species carrying on the molecules have also great influence on the aggregation behavior [33]. For instance, due to the tendency of Ni(II) ion to form octahedral complexes, it was seen intense self-assemble in the spectrum of 8 at about 10-5 M concentration, especially in DMF and DMAc [34]. The Q band positions of the complexes vary conclusively when the solvent is changed. In general, the red shift of the Q band increases with the increase of refractive index of solvent [35]. DMSO has the highest refractive index (1.479) comparing with DMF and DMAc for justifying the more red-shift in the Q bands of the complexes (Fig.1a-f). In the λmax values of Q-bands in the electronic spectra of the prepared Pc compounds (3-8), clear differences could be easily observed. The Mn(III), Co(III) and Ni(II) complex substituted phthalocyanines (6-8) have much lower absorption maxima due to low solubility in organic solvents than mono-nuclear Pc compounds (3-5) as shown in Fig. 2.
Fig. 2.
3.2. Bleach performance In the modern detergent formulations is basically aimed to remove quite different kind of dirt and stains such as tea, coffee, red wine and fruit from the fabric types. The bleach processes containing the oxidation reactions of suitable oxidants with chromophore group are applied for the purposed stain removing. The first step is the disappearance of the color of a stain due to the oxidation of the π-system; the second one is the removal of the de-colored stains from the surface as water-soluble products. In Europe peroxide-based bleach systems in laundry application, sodium perborate or sodium per-carbonate as the hydrogen peroxide source are widely used. However, this process requires high energy consumption (above 60 °C) due to the kinetics of this oxidant. In order to solve these problems, bleach activators such as tetraacetylethylenediamine (TAED) and nonanoyloxybenzene sulfonate were developed and applied in laundry detergents [36]. These activators help to increase the bleach performance of hydrogen peroxide at 40 °C. However, scientific approaches have been trying to develop laundry bleaching systems at lower temperatures by means of decreasing washing temperatures. Transition metal complexes have been trying to apply as bleach catalysts to able to decrease the washing conditions almost to room temperatures, as well. For this purpose we have developed new kind of bleach catalysts. Unlike bleach activators, hydrogen peroxide-activating catalyst have many advantages in terms of stoichiometric quantities, reusability and environmental aspects. The procedure of bleaching experiments was derived from the published literatures as described previously for
phthalocyanine complexes [17, 18 and 37]. Morin dye belonging to polyphenolic chromophores of flavonoids was chosen as a model marker for wine stains and its bleaching was examined in solution conditions. The applied bleach process conditions and the colorless water soluble degradation products which were proposed in our recent study are presented in Scheme 3[17].
Scheme 3.
Catalytic reaction of CoPcs (3-5) may be assumed to be carried out by the coordination of the -
active oxidative intermediate (OOH ), which were generated from H2O2, to the central metal ion to form PcCo-OOH species, in a similar way to porphyrins-Fe(III) complexes [38]. The oxidation of Co(II) to Co(III) ions with axial ligand substitution reactions are dissociative with the formation of five-coordinate intermediates which are the main precursor for the catalytic reactions (Eq. 1) [39]. These intermediates are expected to be highly reactive, and the chemical equation can be written as follows (Eq. 2);
-
H2O2
+
-
H + OOH
PcCoII + HOOH
OH
-
H2O + OOH
[PcCoIII – OOH]
(Eq. 1) (Eq. 2)
The catalytic reactions of the complex substituents via Mn(III)Cl (6) and Co(III)Cl (7) centers carry out by occurring nucleophilic M(III)-OOH peroxo complex as illustrated for the central Co ion of the Pc molecules. For the Ni(II) complex substituted CoPc (8), Ni (II) ion has also tendency to form six coordinate octahedral complex, and the perhyroxyl anion may coordinate
weakly to Ni ion as anionic ligand which behaves likely for 6 and 7 complexes. This mechanism is proposed for attacking of the nucleophilic M(III)-peroxo complexes to the chromophores [40]. The bleaching activity of the prepared phthalocyanine complexes was examined, and the catalyst activities were determined in terms of de-coloration percentage of Morin, bleaching speed and the rate of chromophore destruction. The activity of H2O2 alone as oxidant and TAED used in detergent formulations as the bleach activator were measured as 100 fold of the prepared catalysts. The effect of oxidant (H2O2) with commercial TAED, mono nucleating Pc compounds (3-5), tri-nucleating Pc compounds (6-8) and without using catalyst on bleach performance were examined and the obtained results shown by the decrease in absorbance of Morin dye at 411 nm as seen in Fig. 3. When bleaching was started by the addition of hydrogen peroxide/catalyst combination, the decrease in absorbance at 411 nm gradually indicates the oxidative degradation of Morin by monitoring with online spectrophotometric changes in UV-Vis spectroscopy.
Fig. 3.
When the bleaching experiments were evaluated, it was determined that the Co(III)Clcomplex substituted CoPc (7) had the most efficient oxidative catalytic activity as a function of total bleaching percentage with 93.41% and bleaching complete time as 10 minutes (Fig. 3e). The obtained bleaching results of the prepared CoPc complexes were compared with commercial TAED. It was observed that the catalysts had more bleaching efficiency (Fig. 3h). However, it was also observed that the performance of peroxide bleaching is insufficient without using catalyst at ambient temperature alone (Fig. 3g).
In order to enhanced the catalytic activity of the mono metal CoPcs (3-5), we also prepared multi metal containing phthalocyanines 6-8 by introducing Mn(III), Co(III) and Ni(II) ions as the Schiff base complex substituents attached to the Co-phthalocyanine core via CoPc 5. For these catalysts called as trinuclear complexes were reached the higher bleaching activity compared to the mono-nuclear CoPcs (3-5). It has been have been observed that CoPc 7 carrying two Co(III)Cl-complex substituents is a more efficient catalyst than other three nuclear CoPc complexes (6, 8). Mn(III) complexes could exist as µ-oxo dimer forms under basic condition which is indispensable for the laundry applications. These Mn(III) species, which reduces the catalytic activities, have to cleavage before the formation of the active form of the catalysts [41]. The lowest activity was observed for CoPc 8 carrying two Ni(II)complex substituents among the studied trinuclear Pcs. Nickel is redox-inactive and the lack of catalytic activity is due to absence of Ni(III) [42] (Fig.3c). Differences in catalytic ability have been also attributed to the reversibly binding capacity of the octahedral metal complexes to perhydroxyl anion (HOO-) [43]. In the light of these results, the order of increasing the activity of the substituted metal ions is Co(III)>Mn(III)>Ni(II) due to the octahedral complex formation affinity of the central metal ions with their d orbital electron distributions order as d 6 > d 4> d8, respectively. Comparing of the catalytic activity of the all prepared CoPc derivatives, it was determined to be order of Co(III)Cl-complex substituted CoPc (7) > Mn(III)Cl-complex substituted CoPc (6) > Ni(II)-complex substituted CoPc (8) > CoPc 4> CoPc 3> CoPc 5 in terms of total bleaching percentage. The percentages of de-colorations for the prepared complexes were presented at Table 1. Morin de-coloration is monitored for about 45 minutes to characterize the length of a typical washing cycle for all the prepared complexes. It was determined from the disappearance of dye absorption at 411 nm that, 10 min. for 3 and 7, 25 min. for 4, 20 min. for 5, 25 min. for 6 and 30 min. for 8 were the adequate durations to rich the sufficient de-
coloration percentage (Table 1). Selected results are plotted as percentages against corresponding times (Fig. 4.) and all characteristic details are given in Table 1.
Fig. 4.
Table 1.
In the first 20 minutes of the experiment, prepared bleach catalysts reached the almost maximum bleaching effect (Fig. 5). This period can also offered as enough bleaching period for removing stains from textile in real laundry applications.
Fig. 5.
4. Conclusion As the conclusion, we observed that Co-Pc core had already some catalytic activity depending on the included peripheral substituents. Tetra acetal substituted Co-Pc 3 showed the fairly high bleach percentage and degradation rate. When the substituent converted to Schiff base unites (5) through aldehyde groups (4), the catalytic activity decreased gradually. The coordinating of the metals to the Schiff base-Co-Pc ligand (5) led to differences in catalytic activity, as well. The generation of perhydroxyl intermediate adduct (M–OOH) via the central transition metal ions influenced the rate of reaction and bleach percentage. Since,
Co(III) ion has the highest tendency to coordinate the axial perhydroxyl anion, compound 7 bearing three cobalt ions had the highest activity in terms of bleach rate and percentage. When compared to the commercial TAED and H2O2 alone, we obtained more effective bleaching as the bleach percentage in a short time. These results are important in terms of washing times. With this feature, bleach catalysts provide energy saving as well as costeffective when compared with the TAED.
Acknowledgement This work was supported by Ministry of Science, Industry and Technology of Turkey (SANTEZ project no. 0182.STZ.2013-1) and Research Fund of Sakarya University (project no. 2015-50-02-036).
References [1] K. Ishii, N. Kobayashi, in: K.M. Kadish, K.M. Smith, R. Guilard (Eds.), The Porphyrin Handbook, Vol. 16, Academic Press, New York, 2003, pp.1–40. [2] N.B. McKeown, Phthalocyanine materials synthesis, structure and function, Cambridge University Press, 1998. [3] C.C. Leznoff, A.B.P. Lever, Phthalocyanines: Properties and Applications, Vol. 1-4, VCH Publishers (LSK) Ltd., Cambridge, 1996. [4] I.Y. Skobelev, E.V. Kudrik, O.V. Zalomaeva, F. Albrieux, P. Afanasiev, O.A. Kholdeev, A.B. Sorokin, Chem. Commun. 49 (2013) 5577-5579. [5] A.B. Sorokin, Chem. Rev. 113 (2013) 8152-8191. [6] E.T. Saka, Z. Bıyıklıoglu, Journal Organomet. Chem. 745-746 (2013) 50-56. [7] B. Agboola, K.I. Ozoemena, T. Nyokong, J. Mol. Catal A 227 (2005) 209–216. [8] N. Ceylan, G. Gümrükçü, G. K. Karaoglan, A Gül, Synth. Met. 206 (2015) 55–60 [9] M. Kandaz, S.L.J. Michel, B.M. Hoffman, J. Porphyr. Phthalocya. 7 (2003) 700-7012. [10] S. Fouriaux, F. Armand, O. Araspin, A. Ruaudel-Teixier, E. M. Maya, P. Vazquez, T. Torres, J. Phys. Chem. 100(1996) 16984-16988. [12] G. Gümrükçü, G.K. Karaoglan, A. Erdogmus¸ A. Gül, U. Avcıata, Dyes Pigments 95 (2012) 280-289.
[13] G. Parshall, S.Ittel, Homogeneous Catalysis: The Applications and Chemistry of Catalysis by Soluble Transition Metal Complexes, Wiley, New York, 1994, pp.342. [14] J.I. Kroschwitz, M. Howe-Grant Kirk-Othmer, Encyclopedia of Chemical Technology, 4rd ed. Wiley: New York, 1991. [15] F. Bachmann, J. Dannacher, G. Schlinglof, M. Hazenkamp, G. Haensler, K. Hegetschweiler, U. Heinz, PCT Int. Appl., WO2003053986, Ciba Specialty Chemicals Holding Inc.: Switzerland, 2003, p. 57. [16] S. Tunç, O. Duman, T. Gürkan, Ind. Eng. Chem. Res. 52 (2013), 1414. [17] P. Sen, D.K. Simsek, S.Z. Yildiz, Appl. Organometal. Chem. 29 (2015) 509–516. [18] P. Sen, E. Yildirim, S.Z. Yildiz, Synth. Met. 215 (2016) 41–49. [19] D.D. Perrin, W.L.F. Armarego, D.R. Perrin,
Purification of Laboratory Chemicals,
seventh ed., Pergamon Press, New York, 2013. [20] P. Sen, G.Y. Atmaca, A. Erdogmus, N. Dege, H. Genç, Y. Atalay, S. Z. Yildiz, J Fluoresc 25 (2015) 1225–1234. [21] P. Sen, S.Z. Yildiz, Y. Atalay, N. Dege, G. Demirtas, J. Lumin. 149 (2014) 297–305. [22] D. Wöhrle, O. Tsaryova, A. Semioshkin, D. Gabel, O. Suvorova, J. Organomet. Chem. 747 (2013) 98-105. [23] T. Wieprecht, U. Heinz, J. Xia, G. Schlingloff, J. Dannacher, J. Surfactants Deterg. 7 (2004) 59-66. [24] L. Bo, S. Xuzhuo, C. Gongzhen, J.I. Zhenping, Chin. J. Chem. 27 (2009) 1312-1316. [25] G.F. de Sousa, C.A.L. Filgueiras, A. Abras, S.S. Al-Juaid, P.B. Hitchcock, J.F. Nixon, Inorg. Chim. Acta 218 (1994) 139. [26] M. T. Rispens, A. Meetsma, B. L. Feringa, Recl. Trav. Chim. Pays-Bas 113 (1994) 413– 415. [27] V. L. Pecoraro, W. M. Butler, Acta Cryst. C42 (1986) 1151-1154. [28] N. Kobayashi, Coord. Chem. Rev. 227 (2002) 129-152. [29] P. Tau, T. Nyokong, Dalton Trans. (2006) 4482–4490. [30] S.Z. Yildiz, M. Kucukislamoglu, M. Tuna, J. Organomet. Chem. 694 (2009) 4152-4161. [31] T. Nyokong, Coord. Chem. Rev. 251 (2007) 1707-1722. [32] I. Acar, Z. Biyiklioglu, M. Durmus, H. Kantekin, J. Organomet. Chem. 65 (2012) 708– 709. [33] K. Palewska, J. Sworakowski, J. Lipinski, Optical Materials 34 (2012) 1717–1724. [34] X.Y. Li, K.P.N. Dennis, Tetrahedron Lett. 42 (2001) 305–309. [35] H.R. Karaoglu, A. Koca, M.B. Koçak, Dyes Pigments 92 (2012) 1005-1017.
[36] G. Reinhardt, M. Loeffler, Tenside Surf. Det. 34 (1997) 404. [37] A.B. Sorokin, E.V. Kudrik, Catal. Today 159 (2011) 37. [38] W. Nam, H.J. Lee, S.-O. Oh, C. Kim, H.G. Jang, J. Inorg. Biochem. 80 (2000) 219–225. [39] M. Thamae, T. Nyokong, Polyhedron 21 (2002) 133–140. [40] A.B. Sorokin, S.D. Suzzoni-Dezard, D. Poullain, J.-P. Noe, B. Meunier, J. Am. Chem. Soc. 118 (1996) 7410. [41] N. Sehlotho, T. Nyokong, J. Mol. Catal. A:Chem209 (2004) 51–57. [42] T. Malinski, in: K.M. Kadish, K.M. Smith, R. Guilard (Eds.), Porphyrin Handbook Applications: Past, Present and Future, vol. 6, Academic Press, New York, 2000, p. 231, Chapter 44. [43] A.B.P. Lever, M.R. Hempstead, C.C. Leznoff, W. Liu, M. Melnik, W.A.Nevin, P. Seymour, Pure & Appl. Chem. 58 (1986) 1467—1476.
Table Captions Table 1. De-coloration of Morin under homogeneous conditions.
Table 1. Time for complete Catalyst
de-coloration (min) /
de-coloration %
de-coloration %
at the first 20 min.
at 45 min.
the percentage (%)*
*
3
10 (84,67)
87,5
88,06
4
25 (85,31)
80,1
89,81
5
20 (79,73)
79,73
83,88
6
25 (90,01)
85,51
91,87
7
10 (91.80)
92,84
93,41
8
30 (88,37)
76,74
91,4
H2O2 alone (noncatalytic)
No complete bleaching
3.2
5,26
TAED=Catx100
No complete bleaching
19,21
42,68
These values indicates the percentage of de-coloration at specified time.
Figure Captions
Scheme 1.Synthesis route for aldehyde functionalized pthalocyanines: (i) ethylene glycol, oxalic acid, toluene, reflux. (ii) n-pentanol, Co(CH3COO)2, DBU. (iii) THF, acetic acid, FeCl3.6H2O.
Scheme 2. Synthesis of Schiff base substituted CoPc (5) and its metal complexes: (i) salicylhydrazide, THF, reflux. (ii) DMF, KOH, MnCl2.4H2O for 6, CoCl2.6H2O for 7, NiCl2 for 8.
Fig. 1. Absorption spectra of the compound 3-8 in DMAc, DMF and DMSO. Concentration 1x10-5 mol.L-1. Fig. 2. Absorption spectra of the compound 3-8 in DMF. Concentration 1x10 -5 mol.L-1.
Scheme 3. Bleaching process condition of Morin.
Fig. 3. UV-Vis spectral changes of Morin for bleach experiments. Using with; a) complex 3, b) complex 4, c) complex 5, d) Mn(III)Cl-complex substituted CoPc (6), e) Co(III)Clcomplex substituted CoPc (7), f) Ni(II)-complex substituted CoPc (8), g) H2O2 without catalyst, h) commercial TAED-100 fold of prepared catalysts. Fig. 4. Time dependence of Morin oxidation under homogeneous conditions. (a) % decoloration. (b)The changes of absorbance at 411 nm. Fig. 5.Bleach performance comparison of the prepared complexes with TAED and H2O2 without using catalyst in the first 2 min.
Scheme 1.
Scheme 2.
Fig. 1.
0.6 0.5
Absorbance
Complex 3 Complex 4 Complex 5 Complex 6 Complex 7 Complex 8
in DMF
0.4 0.3 0.2 0.1 0 300
400
500
600
Wavelength (nm)
Fig. 2.
Scheme 3.
700
800
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h) Fig. 3. a), b), c), d), e), f), g) h).
(a)
(b) Fig. 4.
Fig. 5.
Investigation of oxidative bleaching performance of peripherally Schiff base substituted trinuclear cobalt-phthalocyanine complexes Pinar Sena, S. Zeki Yildiza* a
Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, 54187, Sakarya, Turkey
HO HO
OH
O OH OH O
Substrates OH
N
N
N
O
O
O
N N N
M
Co
N
N N
M
N N
O OH
N
N
O
O
O O
N
Products
N
N
HO
HO
Highlights
•
This study covers the functional complexes of the macro molecular Schiff base ligand.
•
The bleaching performances of the complexes were examined by the degradation of Morin.
•
Morin as hydrophilic dye characterizes the wine stains.
•
The degradation progress has been investigated using online spectrophotometric method.
•
The prepared catalysts showed better bleaching performance at 25 °C than TAED.
S0020-1693(16)30614-4 http://dx.doi.org/10.1016/j.ica.2017.02.030 ICA 17456
To appear in:
Inorganica Chimica Acta
Received Date: Revised Date: Accepted Date:
27 September 2016 22 February 2017 24 February 2017
Please cite this article as: P. Sen, S.Z. Yildiz, The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes, Inorganica Chimica Acta (2017), doi: http:// dx.doi.org/10.1016/j.ica.2017.02.030
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The investigation of oxidative bleaching performance of peripherally Schiff base substituted tri-nuclear cobalt-phthalocyanine complexes
Pinar Sena, S. Zeki Yildiza* a
Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, 54187, Sakarya, Turkey
Abstract This study covers the functional complexes of tetrakis [4-(salicyhydrazone)phenoxy)] phthalocyaninato cobalt (II) (5) which was the macro molecular Schiff base ligand and synthesized through a multistep reaction sequence starting first with the cyclotetramerization of 4-[4-(1,3-Dioxolan-2-yl)phenoxy]-phthalonitrile (2). Then, the de-protection of tetra acetal groups of Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninato cobalt (II) (3) to the aldehyde
functionality
in
acetic
formylphenoxy)phthalocyaninato
acid/FeCl3
cobalt(II)
(4)
system and
to
then
yield its
the
Tetrakis(4-
condensation
with
salicylhydrazide gave to 5. Finally, CoPc-bis(salicyhydrazone)phenoxy)manganese (III) (6), CoPc-bis(salicyhydrazone) phenoxy)cobalt(III) (7) and CoPc-bis (salicyhydrazone)phenoxy) nickel(II) (8) were synthesized using with the related MnCl2.4H2O, CoCl2.6H2O, Ni(CH3COO)2 salt in basic conditions in DMF. FT-IR, UV-Vis, MS spectra and elemental analysis were applied to characterize to prepared compounds. The bleaching performances of the prepared phthalocyanine compounds (3-8) were examined by the degradation of Morin as the hydrophilic dye which characterized the wine stains on the fabrics. Progress of the degradations in the catalysts (3-8)/H2O2 combination in basic aqueous solution conditions was investigated by using online spectrophotometric method (OSM). It was found that the prepared catalysts showed better bleaching performance at 25 °C than to that of tetraacetylethylenediamine (TAED) bleach activator commercially used in powder detergent formulations.
Keywords: Synthesis, metalo phtalocyanine, Schiff base, metal complex, bleach catalyst. *Corresponding Author, E-mail address: [email protected], Fax: +90 (264) 295 68 25
1. Introduction Phthalocyanines (Pcs) as synthetic porphyrin analogues are considered
for excellent
functional materials and attractive molecular building blocks due to their unique optical, physicochemical, electronic, catalytic and structural properties [1-2]. Because of having potential applications, they have been studied extensively in many areas such as material science, non-linear optics and liquid crystals [3]. One of the attractive targets in phthalocyanine chemistry is the generation of new functional molecular materials for catalytic applications, as well. Metallo-Pcs which contain redox active metals having wide range of oxidation states are preferred as the oxidation catalysts [4]. Metallophthalocyanines (MPcs) can be tuned for the targeted catalytic aim by changing the central metal ion. For the oxidation of olefins, alcohols, aromatics and some other compounds, MPcs received considerable attention as potential catalysts having exceptional catalytic properties [5]. Especially, cobaltphthalocyanines have been employed in oxidation reactions because of their high catalytic activities [6, 7]. Introducing additional functional groups onto the phthalocyanine skeleton are also of great importance for the development of further chemical reactions on Pc macrocycles in order to increase the functionalities and reach the desired properties [8-10]. Phthalocyanines containing reactive functional groups such as crown ethers, macrocyclic amines and other chelating moieties, having rich electron-donor atoms to coordinate metal ions have been interesting target for the chemists for desiging new molecular materials [11]. Several different approaches in designing polynucleating phthalocyanines have emerged. In a recent study, Schiff base moieties and its Zn complexes attached to the phthalocyanine core were prepared starting from an amine substituted Zn phthalocyanine and the fluorescence properties of the prepared complexes have been examined [12].
Schiff base chemistry is a versatile tool in organic synthesis, and especially have played an important role in the development of coordination chemistry because of forming complexes with most transition metals. In our strategy for the design of multi metallic systems involving the Schiff base metal complexes as substituents attached to metallo-phthalocyanine compounds, aldehyde substituted CoPc was used as the precursor. The prepared CoPcs and their Schiff base metal complex substituted multi metallic derivatives were examined as bleach catalysts to activate H2O2 at lower temperatures. The bleach catalysts are actually oxidation catalysts. Oxidation reactions are of great importance in the chemical industry. Hydrogen peroxide is used as potent oxidant frequently [13]. Based on bleach catalyst, hydrogen peroxide may play a major role for the pulp and paper production, waste water treatment and laundry for industrial and domestic applications [14]. Bleach processes carry out through oxidative mechanisms by the degradation of chromophores in to the water-soluble products. The oxidative bleach provides a two-step cleaning effect in laundry applications. The first step which can be called as conversion is the disappearance of the color of stains due to the oxidation of the π-system, than the second one is degradation step which provides to removal of the stains from the surface as the water soluble products. So far, several novel transition metal complexes of salen, saltren, terpyridine-type ligands and triazole derivatives possessing significant potential in activation of hydrogen peroxide have been synthesized as bleach catalysts and tested [15]. These results promoted us to develop new transition-metal catalyst candidates containing phthalocyanine molecules for laundry bleaching applications. In our study, a series of Co-phthalocyanine complexes having two substituted Schiff base Mn(III), Co(III) and Ni(II) complexes directly linked through oxygen bridges to the phthalocyanine core were synthesized and characterized as the new bleach catalysts class. We examined the performance of the prepared catalysts on bleach oxidation at room temperature in the presence
of H2O2 by online spectrophotometric method [16]. In the recent studies performed by our group, the zinc-phthalocyanines having two Co(III), Mn(III) and Fe(III) complexes directly linked through oxygen bridges to the core were synthesized and examined for the purpose [17, 18]. To our knowledge, no such molecule having complex moiety as the substituent on CoPc ring has been obtained and used as bleach catalyst, so far.
2. Experimental 2.1. Chemicals and instruments The following chemicals were obtained from Sigma-Aldrich; Methanol (MeOH), ethanol (EtOH), diethylether, MnCl2.4H2O, Co(CH3COO)2, CoCl2.6H2O, NiCl2, FeCl3, LiCl, Morin hydrate,
potassium
hydroxide
(KOH),
1,8-Diazabicyclo[5.4.0]undec-7-ene
(DBU),
Tetrahydrofuran (THF), Chloroform (CHCl3), Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO) and Dimethylacetamide (DMAc). Hydrogen peroxide was used as industrial grade (50%). All other reagents and solvents were reagent grade quality and obtained from commercial suppliers. All solvents were stored over molecular sieves (4A°) after they dried and purified as described by Perrin and Armarego [19]. Oxygen free inert atmosphere was supplied by argon through dual-bank vacuum-gas manifold system. Deionized water was generated from MILLIPORE ultra-pure water supply system. ThinLayer chromatography (TLC) was performed using silica gel 60-HF254 as an adsorbent. Melting points (m.p.) were determined using a Barnstad-Electrotermel 9200 apparatus and are uncorrected. Electronic spectra were recorded on a Shimadzu UV-2600 Pc-spectrophotometer with quartz cell of 1 cm. Infrared spectra were recorded on a Perkin Elmer Spectrum two FTIR spectrophotometer equipped with Perkin Elmer UATR-TWO diamond ATR and corrected by applying the atr-correction function of Perkin Elmer Spectrum software. For Maldi-TOF spectra, the experiments were carried out using a Bruker microTOF (Germany) in Gebze
Institute of Technology. The compounds were ionized in the positive electro-spray ionization ion source (ESI+) of the mass-spectrometer. The elemental compositions of the samples were analyzed by an element analyzer (Flash 2000, Thermo Scientific). Compounds 6–8 were digested using HNO3 at 170 °C for 1 h. The manganese, cobalt and nickel contents of 6–8 in the digested mixture were determined using an external standard with a Spectro Arcos inductively coupled plasma optical emission spectroscopy (ICP-OES) instrument (Spectro, Kleve, Germany).
2.2. Synthesis 2.2.1 4-[4-(1,3-Dioxolan-2-yl)phenoxy]-phthalonitrile (2) The preparation of 1 has been performed in two steps. 4-nitrophthalonitrile was reacted at first with p-hydroxybenzaldehyde to give the 4-(4-formylphenoxy)phthalonitrile within 96% yield [20]. In the second step, the 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile was obtained for the protecting of aldehyde group with ethylene glycol by applying the our published literature procedure [21]. The obtained spectroscopic data are accordance with the literature [22].
2.2.2 Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninato cobalt (II) (3) In a standard schlenk tube, 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (0.270 gr, 0.92 mmol) (1), Co(CH3COO)2 (0.082 gr, 0.46 mmol) and DBU (couple drops) was dissolved in npentanol (2.5 mL). The reaction mixture was purged by argon at room temperature and heated up to 140 °C for 12h. After cooling to room temperature, the reaction mixture was precipitated by adding methanol/water (15:15 v/v). The precipitated was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Further purification of the phthalocyanine
was performed by size exclusion chromatography on Bio-beads gel (SX-1). The crude product was put onto the column and eluted with CHCl3 and the collected phases were concentrated on a rotary evaporator and re-precipitated with methanol. The desired pure CoPc (3) was obtained as a green solid. Yield 0.250 g, 88%. m.p> 250 °C. FT-IR (UATR-TWOTM) ν max/cm-1 : 3060 (Ar, C-H), 2949, 2882 (Alip, C-H), 1601, 1505 (C=C), 1469-1386 (C-C), 1227 (Ar-O-Ar), 1078, 1014, 941,825. UV–Vis (DMF): λmax (nm) (log ε) 665 (4.66), 604 (4.12), 459 (3.83), 330 (4.65). MS (MALDI-TOF): m/z 1228.56 [M]+. Anal. Calc. for C68H48CoN8O12 (%): C, 66.50; H, 3.94; N, 9.12; O,15.63; Found (%): C, 66.24; H, 4.02; N, 8.97.
2.2.3. Tetrakis(4-formylphenoxy)phthalocyaninato cobalt(II) (4) The cleavage reaction of 3 (225 mg, 0.183 mmol) was performed in acetic acid ( ̴ 5 mL) / FeCl3 (catalytic amount) system using THF (5 mL) to solve the phthalocyanine before adding cleavage regents. The reaction solution was stirred at room temperature for 1d. The resulting mixture was precipitated with water and the precipitate was collected by centrifugation. The crude product was washed several times with ethanol and water to remove any unwanted organic impurity and acidic residue and then it was dried under vacuum. Further purification of the prepared phthalocyanine was performed by size exclusion chromatography on Biobeads gel (SX-1) using CHCl3 as the eluent. The desired pure product 4 was collected by the re-precipitation with methanol after rotary evaporation of the collected organic eluent phases as blue-green solid. Yield 150 mg, 58 %. m.p > 250 °C. FT-IR (UATR-TWO™) ν max/cm-1: 3182-3060 (Ar, C-H), 2846-2734 (O=C-H), 1693 (-C=O), 1592-1501 (C=C), 1467-1384 (CC), 1226 (Ar-O-Ar), 1153, 1088, 828.UV–Vis (DMF): λmax (nm) (log ε) 662 (4.63), 601 (4.04), 458 (3.45), 329 (4.64). MS (MALDI-TOF): m/z 1341 [M+Matrix+2Na+H2O]+. Anal.
Calc. for C60H32CoN8O8 (%) : C, 68.51; H, 3.07; N, 10.65; O,12.17; Found (%): C, 68.32; H, 3.29; N, 10.76.
2.2.4. Tetrakis [4-(salicyhydrazone)phenoxy)]phthalocyaninato cobalt(II) (5) A solution of salicylhydrazine (96 mg, 0.63 mmol) in dry THF (10 mL) was added to a solution of tetrakis[(4-formylphenoxy)-phthalocyaninato]cobalt(II) (4) (200 mg, 0.122 mmol) in THF (10 mL) and the mixture was heated up to 70 °C for 12h. After cooling to room temperature, the solvent was evaporated to 1/10 of the initial volume of the reaction mixture, and then it was precipitated by adding methanol/water (v/v: 1/1). The crude product was collected by filtration as green solid and washed successively with cold water, methanol and ethanol to remove the un-reacted starting materials and dried in vacuo. Yield 0.250 g, 82 %. m.p > 250 °C.FT-IR (UATR-TWO™) ν max/cm-1: 3209 (N-H), 3063-2168 (O-H…..N), 1643 (C=O), 1597 (C=N), 1552 (C=C), 1489-1350 (C-C), 1231 (Ar-O-Ar), 1161, 1093, 752.UV– Vis (DMF): λmax (nm) (log ε) 666 (4.59), 600 (4.14), 326 (5.09). MS (MALDI-TOF): m/z 1229
[M-(C14H11N2O2,
C7H5O2)]+ (in
supporting
information).
Anal.
Calc.
for
C88H56CoN16O12 (%) : C, 66.54; H, 3.55; N, 14.11; O,12.09; Found (%): C, 66.17; H, 3.82; N, 14.18.
2.2.5. Bis [bis (salicyhydrazone)phenoxy)manganese(III)]phthalocyaninatocobalt(II) (6) Compound 5 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, MnCl2.4H2O (18.43 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. Next, LiCl (4.38 mg, 0.103 mmol) was added and the suspension was heated at 100 oC again for 1 h with air bubble. The reaction mixture was precipitated by adding diethylether
(15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 35 mg, 64%. m.p. > 200°C. FT-IR (UATR-TWO™) ν max/cm-1: 3313 (Ar-OH), 3060 (Ar, C-H), 2953-2842 (AlipH C-H), 1649 (C=N), 1595-1520 (C=C), 1489-1385 (C-C), 1229 (Ar-O-Ar), 1092, 1057, 753. UV–Vis (DMF): λmax (nm) (log ε) 668 (3.66), 610 (2.95), 324 (3.97). MS (MALDI-TOF): m/z 1249 [M-(C14H10N2O3, C7H5NO2, 2Cl)]+ (in supporting information). Anal. Calc. C88H52Cl2CoMn2N16O12 (%) : C, 59.88; H, 2.97; N, 12.70; Cl, 4.02; O, 10.88; Co, 3.34; Mn, 6.22; Found (%): C, 59.38; H, 2.76; N, 12.32; Co, 3.02; Mn,6.82 (ICP-OES) .
2.2.6. Bis [bis (salicyhydrazone)phenoxy)cobalt(III)]phthalocyaninatocobalt(II) (7) Compound 5 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, CoCl2.4H2O (16.4 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. Next, LiCl (4.38 mg, 0.103 mmol) was added and the suspension was heated at 100 oC again for 1 h with air bubble. The reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 40 mg, 71%. m.p. > 200°C. FT-IR (UATR-TWOTM) ν max/cm-1: 3309 (Ar-OH), 3060 (Ar, C-H), 1650 (C=N), 1593-1522 (C=C), 1467-1327 (C-C), 1229 (Ar-O-Ar), 1158, 1092, 1056, 746. UV–Vis (DMF): λmax (nm) (log ε) 675 (3.62), 611 (3.08), 319 (3.8).MS (MALDI-TOF): m/z 1484 [M- C14H10N2O3, Cl]+, 1277.79 [M-2(C14H10N2O3), Cl+2Na] (in supporting information). Anal. Calc. for C88H52Cl2Co 3N16O12 (%) : C, 59.61; H, 2.96; N,
12.64; Cl, 4.00; O,10.83; Co, 9.97; Found (%): C, 59.14; H, 3.08; N, 12.38; Co, 9.68 (ICPOES)
2.2.7. Bis [bis (salicyhydrazone)phenoxy)nickel(II)]phthalocyaninatocobalt(II) (8) Compound 4 (50 mg, 0.0313 mmol) and KOH (7.37 mg, 0.132 mmol) were added to dry DMF (10 mL). After stirring for 10 min under argon, NiCl2 (8.9 mg, 0.069 mmol) was added and the final mixture was heated at 100 oC for 8 h and then allowed to cool to room temperature under argon atmosphere. The progress of the reaction was monitored by TLC. The reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was collected by centrifugation, washed several times with ethanol and water to dissolve any unwanted organic impurity and any un-reacted metal salt and dried. Yield 38 mg, 72%. m.p. > 200°C. FT-IR (UATR-TWOTM) ν max/cm-1: 3322 (Ar-OH), 3061 (Ar, C-H), 1593 (C=N), 1521 (C=C), 1489-1365 (C-C), 1230 (Ar-O-Ar), 1161, 1093, 1055, 753. UV–Vis (DMF): λmax (nm) (log ε) 677 (3.88), 609 (3.6), 342 (4.35).MS (MALDI-TOF): m/z 1706.97 [M]+ (in supporting information). Anal. Calc. for C88H52CoN16Ni2O12 (%) : C, 62.11; H, 3.08; N, 13.17; O, 11.28; Co, 3.46; Ni, 6.90; Found (%): C, 61.86; H, 3.25; N, 12.92; Co, 3.22; Ni, 7.03.
2.3. Catalytic bleaching Bleaching process was performed by using online spectrophotometric method to monitor the oxidation of Morin dye [23]. The method used in this study enables in situ following the spectral changes and the determination of the amount of dye bleaching as percentage. Experiments were carried out in a reaction vessel. To the reaction vessel placed on magnetic stirrer was added the required amount of carbonate buffer solution (pH: 10.5), 80 mM morin,
10 µM catalyst and 10 mM hydrogen peroxide for each experiment, respectively. The temperature of solutions was maintained at 25 oC with programmable water bath. A peristaltic pump was used to transfer the solution mixture from the reaction vessel to the flow cell placed in the sample compartment of the UV–vis spectrophotometer. The initial absorbance of morin in buffer solution was measured, and bleaching of morin was followed as the decrease in absorbance at 411 nm. The bleaching reaction was initiated by adding H2O2 into the reaction mixture together with the catalyst. The continuous circulation of the mixture was provided between the reaction vessel and UV–Vis spectrophotometer by the peristaltic pump. The scanning-kinetic measurement program of the software was run to monitor the spectral changes with 5 min. intervals. The absorbance changes were determined by the measurements, and the bleaching percentage was graphed as a function of time. The amount of de-colorization of Morin was expressed as the dye bleaching percentage and calculated by the following Eq. (1) [16].
% =
(1)
Where, A0 and At are the absorbance of morin at time 0 and time t, respectively.
3. Results and discussion 3.1. Synthesis and spectroscopic characterization Scheme 1 shows the synthetic route for the precursor functional phthalocyanines 3 and 4. To be able to syntheses these phthalocyanines, the important starting material is 4-[4-(1,3Dioxolan-2-yl)phenoxy]-phthalonitrile (2) which has been prepared in two steps in this work.
Firstly, 4-nitrophthalonitrile was reacted with p-hydroxybenzaldehyde to give the 4-(4formylphenoxy)phthalonitrile (1) with 96% yield as reported in the literature [20]. For protecting the aldehyde group of 1, 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (2) was obtained in the second step . For this purpose, the literature procedure was slightly modified and catalytic amount of oxalic acid was used instead of p-toluene sulfonic acid [22].
Scheme 1.
The acetal substituted Pc derivative 3 was prepared from the cyclo tetramerization reaction of phthalonitrile 2 with corresponding anhydrous Co(II) salt and in the presence of DBU as a strong base to obtain CoPc 3 in n-pentanol. The purification of 3 was performed by size exclusion chromatography on Bio-beads gel (SX-1) by eluting chloroform. In order to perform the synthesis of the phthalocyanine 4 containing aldehyde functional group, the acetal groups at the peripheral position on phthalocyanine 3 were de-protected in acetic acid/FeCl3.6H2O system by mixing in THF as solvent to enhance the solubility. The
preparation of
salicylhydrazone
substituted
phthalocyanine
5
as
the
macromolecular Schiff base ligand was conducted in THF at reflux temperature by using phthalocyanine 4 and salicylhydrazine as the corresponding aldehyde and amine derivatives, respectively. The complexation of the salicylhdrazone groups on the periphery positions of phthalocyanine 5 to give trinuclear-Pcs was carried out with MnCl2.4H2O for 6, CoCl2.6H2O for 7 and Ni(CH3 COO)2 for 8 in DMF under basic condition as shown in scheme 2. After
completion of the reactions, LiCl was added to the reaction mixtures individually to complete
the manganese and cobalt site with Cl- anions. Oxidation of the Mn(II) and Co(II) to the Mn(III) and Co(III) was achieved by air bubbling.
Scheme 2.
Characterization of the products was carried out by the combination of spectroscopic methods including FT-IR, melting point, UV/Vis and Mass spectroscopy. All the spectral data are in accordance with the proposed structures. The formation of 2 can be recognized from the disappearance of C=O vibration at 1691 cm-1 and the aldehyde C–H vibrations at 2805–2764 cm-1 for compound 1 and the appearance of new absorption bands at 2959-2888 cm-1 and 1083 cm-1 belonging to the aliphatic –C–H and aliphatic –C–O–C– vibrations, respectively. Cyclotetramerization of the dinitrile derivative 2 to the acetal substituted Pc 3 was confirmed by the disappearance of the sharp –C≡N stretching vibration band at 2235 cm-1, as expected. The typical aliphatic –C–H vibrational bands at 2949-2882 cm-1 were assigned to C–H stretching of the acetal groups of 3. The sharp peak at 1693 cm-1 in the FT-IR spectrum of 4 belonging to the C=O stretching vibration is indicative for the cleavage reaction of 3 to the desired aldehyde substituted Pc 4. Furthermore, the peaks in the range of 2846-2734 cm-1 which are attributed as Fermi resonance prove the aldehyde formation, as well. Formation of Schiff base on the periphery of phthalocyanine 4 after treated with salicylhydrazide to give compound 5 was confirmed by the disappearance of the C=O stretching vibration of formyl groups and appearance of –C=N stretching vibration band at
1597 cm-1. However, the –C=O stretching vibration band of combined salicylhydrazone group appeared at 1643 cm-1 proves to keto form and is accordance with the published literature [24]. The N–H vibration of amide nitrogen appeared at 3209 cm-1. Typical O–H…N vibrations appeared as a large distorted band at the range of 3063-2168 cm-1 confirmed that the hydrogen bonding occurred between the –NH– and the phenolic –OH groups of the salicylhydrazone moieties. The FT-IR spectra of 6-8 were interpreted with the comparison of the spectrum of free ligand 5 in which the C=O vibration at 1643 cm-1 disappeared. This indicates that the keto oxygens in the hydrazine groups enolize and deprotonate during complexion with the corresponding metal ions in alkaline conditions. The C=N band at 1597 cm-1 belonging to the ligand molecule (5) shifted to 1649 cm-1 for 6 and 1650 cm-1 for 7, respectively. These upper shifts in the spectra of the complexes are due to chelate formation which makes the complexes more stable and the bonds of ligands located around metal ions stronger. This is also further confirmation for the coordination of the ligands through the azomethine nitrogen and enolate oxygen atoms [17]. The same imine band shifts to lower wavenumber to 1593 cm-1 with respect to free ligand for Ni(II)complex substituted phthalocyanine 8 upon coordination, as well. The 1H- NMR and 13C-NMR spectra of cobalt phthalocyanines 3-8 could not be taken due to the paramagnetic cobalt(II) center. The Mass spectra of 3-8 were obtained by the MALDI-TOF Mass spectrometer confirming the proposed structure. Many different MALDI matrices were tried to find an intense molecular ion peak and low fragmentation under the MALDI-MS conditions for this Pcs. The best matrix for Pc 3 was found to be Dithranol (DIT) with mainly molecular ion peak at m/z: 1228.56 [M]+ as the base peak of spectrum. For compound 4, α-cyano-4-
hydroxycinnamic acid (CHCA) was used to make the molecular ion peaks at m/z: 1240 [M+Matrix+Na]+ visible. In the mass spectrum of 5 obtained without using matrix, molecular ion peak was observed at around m/z: 1590 as a small peak. However, the base peak of the spectrum at m/z: 1229 was attributed to fragment ion peak calculated as [M-(C14H11N2O2, C7H5O2)] +. The observed other fragments were tabulated and given in supporting information in detail.
For the metal complex substituted Pcs (6-8),
sinapic acid (SA), α-cyano-4-
hydroxycinnamic acid (CHCA) and Dithranol (DIT) were used respectively, and the molecular ion peaks at m/z: MS (MALDI-TOF): m/z1249 [M-(C14H10N2O3, C7H5NO2, 2Cl)]+ for 6, 1484 [M-2(C7H5O2, Cl)+Na]+ for 7 and 1706.97 [M]+ for 8 were observed. The structural characterization of these resultant hydrazine complexes showed that the 1/2 ligand/metal ratio is most suitable stoichiometry gave corresponding stable chelate complexes. However, this case depends also on the conditions, such as metal ion, its concentration, the pH of the medium, and the nature of the hydrazone ligand [25]. It is known that in the prepared compounds, the Co (III), Mn (III) and Ni (II) ions at the center of the complexes in the periphery tend to bind co-ligands to the axial positions to reach the octahedral geometry. However, there are some crystallized molecular examples in the literature especially for Mn(III) and Co(III) ions in which the central metal ions have Penta dentate geometry, and these complexes are called as Jacobsen type catalysts [26]. In some cases, the coordinated small molecules such as water and solvents were ignored in the drawing of molecular structres, as well [27]. The elemental analysis results for the synthesized phthalocyanines (3-8) were consistent with the theoretical calculated values given in the experimental section. ICP-OES measurements were also done for the determination of the quantities of Co, Mn and Ni ions included in Pc structures 6–8. The theoretical percentage of cobalt by weight in 6 is 3.34, in 7 is 9.97 and in 8 is 3.46. The experimental results show that the percentages by weight of
cobalt ions are 3.02 for 6, 9.68 for 7 and 3.75 for 8. In a similar way, the theoretical percentage by weight of manganese content in 6 is 6.22 and nickel in 8 is 6.90. From the experiment, as the percentages by weight of Mn(II) and Ni(II) are obtained as 6.82 and 7.03, respectively. Thus, the ICP-OES measurements provide additional support to the proposed molecular structures of 6-8. The ground-state electronic spectroscopy is one of the most useful methods for the determination of structural properties of phthalocyanines. The absorption spectra of phthalocyanines give information about the symmetry of HOMO and LUMO orbitals, isomerization types and aggregation of the molecules. Generally, phthalocyanine compounds display two intense absorption bands in the electronic spectra. One of them is observed in the visible region of spectrum at around 600–700 nm (Q-band) and the other one is in the UV region at around 300–350 nm (B-band), and both of them are correlated to π–π* transitions. Phthalocyanine compounds also exhibit vibronic bands on the blue side of the Q-bands attributed to n–π* transitions [28]. The electronic spectra of the prepared phthalocyanines were recorded in three different solvents (DMAc, DMF and DMSO) to observe the relation between polarity and basicity of the solvents, and the aggregation tendencies were observed for complex 3-8 as seen in Fig. 1.
Fig. 1.
DMAc is the most basic solvent among the used ones and makes more ionic interaction. The solubility of the compounds 4, 6 and 7 increased in DMAc by the decreasing of π–π stacking with the pointed out ionic interaction (Fig. 1b, 1d, 1e). DMSO, which is a
strong coordinating solvent with a high donor number that is able to coordinate to most central metals of porphyrins and phthalocyanines through either the sulfur or the oxygen atoms, normally prevents aggregation [29]. Thus aggregation should be more diminished in DMSO. However, this is not the case in this work for all Pcs. This effect only observed in compounds 3 and 8 (Fig. 1a, 1f). All metalled phthalocyanine complexes 3-8 showed intense Q-absorption band at around 660-680 nm with
no
splitting on them which assigned
that it
was
metallophthalocyanine with the D4h symmetry as expected [30]. Intense Q band absorptions indicate clearly the presence of monomeric species in the solutions. High aggregation tendency of phthalocyanine compounds due to the interactions between their 18 π-electron systems often cause weak solubility, the appearance of broad bands and decrease in intensity as observed for compounds 5-8 (Fig. 1c, 1d, 1e, 1f) [31,32]. Beside of solvent types and the concentration of Pc solutions, the metal species carrying on the molecules have also great influence on the aggregation behavior [33]. For instance, due to the tendency of Ni(II) ion to form octahedral complexes, it was seen intense self-assemble in the spectrum of 8 at about 10-5 M concentration, especially in DMF and DMAc [34]. The Q band positions of the complexes vary conclusively when the solvent is changed. In general, the red shift of the Q band increases with the increase of refractive index of solvent [35]. DMSO has the highest refractive index (1.479) comparing with DMF and DMAc for justifying the more red-shift in the Q bands of the complexes (Fig.1a-f). In the λmax values of Q-bands in the electronic spectra of the prepared Pc compounds (3-8), clear differences could be easily observed. The Mn(III), Co(III) and Ni(II) complex substituted phthalocyanines (6-8) have much lower absorption maxima due to low solubility in organic solvents than mono-nuclear Pc compounds (3-5) as shown in Fig. 2.
Fig. 2.
3.2. Bleach performance In the modern detergent formulations is basically aimed to remove quite different kind of dirt and stains such as tea, coffee, red wine and fruit from the fabric types. The bleach processes containing the oxidation reactions of suitable oxidants with chromophore group are applied for the purposed stain removing. The first step is the disappearance of the color of a stain due to the oxidation of the π-system; the second one is the removal of the de-colored stains from the surface as water-soluble products. In Europe peroxide-based bleach systems in laundry application, sodium perborate or sodium per-carbonate as the hydrogen peroxide source are widely used. However, this process requires high energy consumption (above 60 °C) due to the kinetics of this oxidant. In order to solve these problems, bleach activators such as tetraacetylethylenediamine (TAED) and nonanoyloxybenzene sulfonate were developed and applied in laundry detergents [36]. These activators help to increase the bleach performance of hydrogen peroxide at 40 °C. However, scientific approaches have been trying to develop laundry bleaching systems at lower temperatures by means of decreasing washing temperatures. Transition metal complexes have been trying to apply as bleach catalysts to able to decrease the washing conditions almost to room temperatures, as well. For this purpose we have developed new kind of bleach catalysts. Unlike bleach activators, hydrogen peroxide-activating catalyst have many advantages in terms of stoichiometric quantities, reusability and environmental aspects. The procedure of bleaching experiments was derived from the published literatures as described previously for
phthalocyanine complexes [17, 18 and 37]. Morin dye belonging to polyphenolic chromophores of flavonoids was chosen as a model marker for wine stains and its bleaching was examined in solution conditions. The applied bleach process conditions and the colorless water soluble degradation products which were proposed in our recent study are presented in Scheme 3[17].
Scheme 3.
Catalytic reaction of CoPcs (3-5) may be assumed to be carried out by the coordination of the -
active oxidative intermediate (OOH ), which were generated from H2O2, to the central metal ion to form PcCo-OOH species, in a similar way to porphyrins-Fe(III) complexes [38]. The oxidation of Co(II) to Co(III) ions with axial ligand substitution reactions are dissociative with the formation of five-coordinate intermediates which are the main precursor for the catalytic reactions (Eq. 1) [39]. These intermediates are expected to be highly reactive, and the chemical equation can be written as follows (Eq. 2);
-
H2O2
+
-
H + OOH
PcCoII + HOOH
OH
-
H2O + OOH
[PcCoIII – OOH]
(Eq. 1) (Eq. 2)
The catalytic reactions of the complex substituents via Mn(III)Cl (6) and Co(III)Cl (7) centers carry out by occurring nucleophilic M(III)-OOH peroxo complex as illustrated for the central Co ion of the Pc molecules. For the Ni(II) complex substituted CoPc (8), Ni (II) ion has also tendency to form six coordinate octahedral complex, and the perhyroxyl anion may coordinate
weakly to Ni ion as anionic ligand which behaves likely for 6 and 7 complexes. This mechanism is proposed for attacking of the nucleophilic M(III)-peroxo complexes to the chromophores [40]. The bleaching activity of the prepared phthalocyanine complexes was examined, and the catalyst activities were determined in terms of de-coloration percentage of Morin, bleaching speed and the rate of chromophore destruction. The activity of H2O2 alone as oxidant and TAED used in detergent formulations as the bleach activator were measured as 100 fold of the prepared catalysts. The effect of oxidant (H2O2) with commercial TAED, mono nucleating Pc compounds (3-5), tri-nucleating Pc compounds (6-8) and without using catalyst on bleach performance were examined and the obtained results shown by the decrease in absorbance of Morin dye at 411 nm as seen in Fig. 3. When bleaching was started by the addition of hydrogen peroxide/catalyst combination, the decrease in absorbance at 411 nm gradually indicates the oxidative degradation of Morin by monitoring with online spectrophotometric changes in UV-Vis spectroscopy.
Fig. 3.
When the bleaching experiments were evaluated, it was determined that the Co(III)Clcomplex substituted CoPc (7) had the most efficient oxidative catalytic activity as a function of total bleaching percentage with 93.41% and bleaching complete time as 10 minutes (Fig. 3e). The obtained bleaching results of the prepared CoPc complexes were compared with commercial TAED. It was observed that the catalysts had more bleaching efficiency (Fig. 3h). However, it was also observed that the performance of peroxide bleaching is insufficient without using catalyst at ambient temperature alone (Fig. 3g).
In order to enhanced the catalytic activity of the mono metal CoPcs (3-5), we also prepared multi metal containing phthalocyanines 6-8 by introducing Mn(III), Co(III) and Ni(II) ions as the Schiff base complex substituents attached to the Co-phthalocyanine core via CoPc 5. For these catalysts called as trinuclear complexes were reached the higher bleaching activity compared to the mono-nuclear CoPcs (3-5). It has been have been observed that CoPc 7 carrying two Co(III)Cl-complex substituents is a more efficient catalyst than other three nuclear CoPc complexes (6, 8). Mn(III) complexes could exist as µ-oxo dimer forms under basic condition which is indispensable for the laundry applications. These Mn(III) species, which reduces the catalytic activities, have to cleavage before the formation of the active form of the catalysts [41]. The lowest activity was observed for CoPc 8 carrying two Ni(II)complex substituents among the studied trinuclear Pcs. Nickel is redox-inactive and the lack of catalytic activity is due to absence of Ni(III) [42] (Fig.3c). Differences in catalytic ability have been also attributed to the reversibly binding capacity of the octahedral metal complexes to perhydroxyl anion (HOO-) [43]. In the light of these results, the order of increasing the activity of the substituted metal ions is Co(III)>Mn(III)>Ni(II) due to the octahedral complex formation affinity of the central metal ions with their d orbital electron distributions order as d 6 > d 4> d8, respectively. Comparing of the catalytic activity of the all prepared CoPc derivatives, it was determined to be order of Co(III)Cl-complex substituted CoPc (7) > Mn(III)Cl-complex substituted CoPc (6) > Ni(II)-complex substituted CoPc (8) > CoPc 4> CoPc 3> CoPc 5 in terms of total bleaching percentage. The percentages of de-colorations for the prepared complexes were presented at Table 1. Morin de-coloration is monitored for about 45 minutes to characterize the length of a typical washing cycle for all the prepared complexes. It was determined from the disappearance of dye absorption at 411 nm that, 10 min. for 3 and 7, 25 min. for 4, 20 min. for 5, 25 min. for 6 and 30 min. for 8 were the adequate durations to rich the sufficient de-
coloration percentage (Table 1). Selected results are plotted as percentages against corresponding times (Fig. 4.) and all characteristic details are given in Table 1.
Fig. 4.
Table 1.
In the first 20 minutes of the experiment, prepared bleach catalysts reached the almost maximum bleaching effect (Fig. 5). This period can also offered as enough bleaching period for removing stains from textile in real laundry applications.
Fig. 5.
4. Conclusion As the conclusion, we observed that Co-Pc core had already some catalytic activity depending on the included peripheral substituents. Tetra acetal substituted Co-Pc 3 showed the fairly high bleach percentage and degradation rate. When the substituent converted to Schiff base unites (5) through aldehyde groups (4), the catalytic activity decreased gradually. The coordinating of the metals to the Schiff base-Co-Pc ligand (5) led to differences in catalytic activity, as well. The generation of perhydroxyl intermediate adduct (M–OOH) via the central transition metal ions influenced the rate of reaction and bleach percentage. Since,
Co(III) ion has the highest tendency to coordinate the axial perhydroxyl anion, compound 7 bearing three cobalt ions had the highest activity in terms of bleach rate and percentage. When compared to the commercial TAED and H2O2 alone, we obtained more effective bleaching as the bleach percentage in a short time. These results are important in terms of washing times. With this feature, bleach catalysts provide energy saving as well as costeffective when compared with the TAED.
Acknowledgement This work was supported by Ministry of Science, Industry and Technology of Turkey (SANTEZ project no. 0182.STZ.2013-1) and Research Fund of Sakarya University (project no. 2015-50-02-036).
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Table Captions Table 1. De-coloration of Morin under homogeneous conditions.
Table 1. Time for complete Catalyst
de-coloration (min) /
de-coloration %
de-coloration %
at the first 20 min.
at 45 min.
the percentage (%)*
*
3
10 (84,67)
87,5
88,06
4
25 (85,31)
80,1
89,81
5
20 (79,73)
79,73
83,88
6
25 (90,01)
85,51
91,87
7
10 (91.80)
92,84
93,41
8
30 (88,37)
76,74
91,4
H2O2 alone (noncatalytic)
No complete bleaching
3.2
5,26
TAED=Catx100
No complete bleaching
19,21
42,68
These values indicates the percentage of de-coloration at specified time.
Figure Captions
Scheme 1.Synthesis route for aldehyde functionalized pthalocyanines: (i) ethylene glycol, oxalic acid, toluene, reflux. (ii) n-pentanol, Co(CH3COO)2, DBU. (iii) THF, acetic acid, FeCl3.6H2O.
Scheme 2. Synthesis of Schiff base substituted CoPc (5) and its metal complexes: (i) salicylhydrazide, THF, reflux. (ii) DMF, KOH, MnCl2.4H2O for 6, CoCl2.6H2O for 7, NiCl2 for 8.
Fig. 1. Absorption spectra of the compound 3-8 in DMAc, DMF and DMSO. Concentration 1x10-5 mol.L-1. Fig. 2. Absorption spectra of the compound 3-8 in DMF. Concentration 1x10 -5 mol.L-1.
Scheme 3. Bleaching process condition of Morin.
Fig. 3. UV-Vis spectral changes of Morin for bleach experiments. Using with; a) complex 3, b) complex 4, c) complex 5, d) Mn(III)Cl-complex substituted CoPc (6), e) Co(III)Clcomplex substituted CoPc (7), f) Ni(II)-complex substituted CoPc (8), g) H2O2 without catalyst, h) commercial TAED-100 fold of prepared catalysts. Fig. 4. Time dependence of Morin oxidation under homogeneous conditions. (a) % decoloration. (b)The changes of absorbance at 411 nm. Fig. 5.Bleach performance comparison of the prepared complexes with TAED and H2O2 without using catalyst in the first 2 min.
Scheme 1.
Scheme 2.
Fig. 1.
0.6 0.5
Absorbance
Complex 3 Complex 4 Complex 5 Complex 6 Complex 7 Complex 8
in DMF
0.4 0.3 0.2 0.1 0 300
400
500
600
Wavelength (nm)
Fig. 2.
Scheme 3.
700
800
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h) Fig. 3. a), b), c), d), e), f), g) h).
(a)
(b) Fig. 4.
Fig. 5.
Investigation of oxidative bleaching performance of peripherally Schiff base substituted trinuclear cobalt-phthalocyanine complexes Pinar Sena, S. Zeki Yildiza* a
Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, 54187, Sakarya, Turkey
HO HO
OH
O OH OH O
Substrates OH
N
N
N
O
O
O
N N N
M
Co
N
N N
M
N N
O OH
N
N
O
O
O O
N
Products
N
N
HO
HO
Highlights
•
This study covers the functional complexes of the macro molecular Schiff base ligand.
•
The bleaching performances of the complexes were examined by the degradation of Morin.
•
Morin as hydrophilic dye characterizes the wine stains.
•
The degradation progress has been investigated using online spectrophotometric method.
•
The prepared catalysts showed better bleaching performance at 25 °C than TAED.