- Email: [email protected]
RETRACTED: Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative
Author’s Accepted Manuscript Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative Masoumeh Orojloo, Saeid Amani www.elsevier.com/locate/talanta
PII: DOI: Reference:
S0039-9140(16)30467-2 http://dx.doi.org/10.1016/j.talanta.2016.06.042 TAL16672
To appear in: Talanta Received date: 24 December 2015 Revised date: 18 June 2016 Accepted date: 20 June 2016 Cite this article as: Masoumeh Orojloo and Saeid Amani, Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative, Talanta, http://dx.doi.org/10.1016/j.talanta.2016.06.042 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative Masoumeh Orojlooa and Saeid Amania,* a
Department of Chemistry, Faculty of Sciences, Arak University, Dr. Beheshti Avenue, Arak
38156-8-8349, Iran. *
Corresponding author. Email: [email protected]
ABSTRACT A new chromogenic receptor, 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol, has been designed and synthesized for quantitative and low-cost detection of various biological anions and cations. The dye was characterized by elemental analyses, infrared, UV-visible spectroscopy, and NMR spectroscopy. Upon the addition of F− and H2PO4− to the solution of chemosensor in DMSO, the dramatic naked eye detectable color changes were observed from yellow to red and orange with a limit of detection (LOD) of 1.66⤬10-6 mol.L−1 and 1.24 ⤬10-6 mol.L−1
at room temperature, respectively. The
chemosensor showed visual changes towards cations, such as Al3+, Cu2+, Fe3+, and Cr3+, in DMSO/water (9:1). The detection limit of receptor L for the analysis of Al3+ ion was calculated to be 3.02 ⤬10-6 mol.L−1. The anion recognition property of the receptor via proton transfer was monitored by UV-visible titration and 1HNMR spectroscopy. The binding constant (Ka) and stoichiometry of the host–guest complexes formed were determined by the Benesi–Hildebrand (B–H) plot and Job’s method, respectively.
Keywords: Chemosensor; Schiff-base receptors; Naked-eye detection of F¯, H2PO4¯ and Al3+ 1. Introduction
Ions have essential effects in nature; however, in excess, they can be dangerous for living systems and the environment. For example, aluminum (III) ion is found abundantly in nature, such as in drinking water contamination, and can be toxic to humans in excessive amounts. Many symptoms of aluminum toxicity mimic those of Alzheimer’s disease, Parkinson’s disease, and osteoporosis [1,2]. Copper ion, which plays a very important role in living systems (tyrosinase, ferroxidase, and many others), is poisonous to living cells. The presence of free copper ion can cause blood hemolysis, or kidney and liver damage [2–4]. Furthermore, it is an environment pollutant that causes concern in industry and agriculture [5–9]. Fluoride ion is a component of toothpastes. In high amounts, it is toxic and produces dental fluorosis [10,11]. Molecular receptors have received great attention in the last two decades, possibly because of the great importance of the complexation of cations and anions in areas such as chemistry, biology, pharmaceutics, environment, and industry [12–23]. Molecular receptors allow quick and selective ion recognition. The synthesis of chemosensors for the recognition of harmful and toxic ions is very important challenge, nowadays [24–33]. Cation receptors have been studied extensively, whereas anion receptors have received less attention. The rationales of the challenge that developing reliable sensing methods for anions represents include (1) anions are larger than cations with the same electronic configuration and, therefore, have a lower charge-to-radius (surface) ratio, a feature that makes the electrostatic binding of anions to receptors less effective; [34] (2) anions have a wide range of geometries and are often present in the most stable forms, resulting in higher complexity in the design and preparation of receptors; and (3) anions are pH sensitive because they can absorb protons at low pH to become neutral molecules. Therefore, to obtain the desired selectivity, a combination of electrostatic attraction and hydrogen bonding, and a suitable framework onto which these structural components can be assembled need to be taken into consideration when designing artificial anionic hosts [35].
Chemosensors are based on molecules that can bind selectively and reversibly with an anion or a cation [36]. However, most of these are designed to rely on the same principles, namely, that the functional moiety is covalently (binding site-signaling subunit approach) [37–41] or non-covalently (displacement approach) [42] linked to the signal moiety (e.g. chromogene, electrochemical group, fluorescent group). Schiff bases are common organic structures which can be easily synthesized through a one-step synthetic procedure [43]. The ionochromic behavior of Schiff bases and the interaction with a wide range of metal ions have been well documented [44]. Schiff bases containing salicyaldimine based ligands can be used in the development of cost-effective chemosensors because they show significant color changes of the solution and maxima of the absorption bond when they interact with anions and cations [45–46]. Recently, we reported aneasy and applicable method for the preparation [47] and use of low cost chemosensors based on Schiff bases for the selective detection of some toxic metal ions and anions [48,49]. Herein, we report for the first time novel colorimetric studies on cation and anion sensing by chromogenic azo-azomethine receptor (L) possessing a phenolic OH group and binds F− and H2PO4− (anion binding site). The position of azomethine (-CH=N) group in this Schiff base allows it to act as a ligand to adsorb cations (cation binding site). The behavior of this new Schiff base towards anions and cations was investigated by NMR spectroscopy and UV-visible spectroscopy in DMSO and a mixture of water/DMSO solutions. As expected, the sensor (L) could act as convenient, colorimetric, and ‘naked eye’ indicator for application as a chemosensor for biological anions and cations (Scheme 1).
1.
Experimental
1.1. Materials and Equipments
All chemicals were purchased from Sigma-Aldrich and Merck and used without further purification. Fourier transform infrared (FT-IR) spectra were recorded as pressed KBr discs using a Unicom Galaxy Series FT-IR 5000 spectrophotometer in the region of 400–4000 cm−1. Melting points were determined on an Electrothermal 9200 apparatus. Determination of C, N, and H composition was undertaken using an Elemental Analysis System, GmbH Vario EL III. Electronic spectral measurements were carried out using Optizen 3220 UV spectrophotometer in the range of 200–900 nm. NMR spectra were recorded on a Bruker AV 300 MHz and Bruker Avance III 400 MHz spectrometers.
1.2.
Synthesis of 1-(3-Formyl-4-hydroxyphenylazo)-2,4-dichlorobenzene
A mixture of 2,4-dichloroaniline (6.48 g, 40 mmol) in hydro-chloric acid (36 ml) and water (16 ml) was heated to 80 oC to form a solution. The clear solution was poured into an ice/water mixture and diazotized at 0–5 oC with sodium nitrite (2.8 g, 40 mmol) in water (10 ml). The cold diazonium solution was added to a solution of salicylaldehyde (4.88 g, 40 mmol) in water (75 ml) containing sodium carbonate (14.8 g, 40 mmol) and sodium hydroxide (1.6 g, 40 mmol) over the course of 30 min at 0 oC. The reaction mixture was first stirred for 1 h at 0 oC and then stirred for 2 h at room temperature. The product was collected by vacuum filtration and washed with NaCl solution (100 ml, 10 %). Coupling of the diazonium reagent to the salicylaldehyde occurred at the position para to the hydroxyl group. The diazo compound was dried at room temperature. Yellow solid; yield: 88%; m. p. 121– 123 oC. 1H NMR (DMSO– d6, 300 MHz, ppm); δ: 7.29 (d, 1H, J = 8.84 Hz), 8.09 (dd, 1H, J= 8.84 Hz and 2.16 Hz), 7.55 (d, 1H, J = 8.76 Hz), 7.68 (d, 1H, J =8.76 Hz), 7.89 (s, 1H), 8.19 (d, 1H, J =2.16 Hz), 10.37 (s, 1H), 11.88 (br, 1H). IR (KBr, cm-1); 1666 (CHO), 1620 (C=C), 1575 (phenol ring), 1483 (N=N), 1286 (C–O). Anal. Calcd. For C13H8Cl2N2O2: C, 52.91; N,
9.49; H, 2.73%. Found: C, 52.70; N, 9.42; H, 2.66%. λmax (nm) (ε(M-1.cm-1)): 260 (29950), 356 (49260) and 465 (11853) in DMSO.
1.3. Synthesis of Sensor L: 4-((2,4-Dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol A solution of 3-amino-1-propanol (0.15 g, 2 mmol) in absolute ethanol (EtOH; 10 ml) was added to a stirring solution of azo-coupled precursor (0.59 g, 2 mmol) in absolute EtOH (60 ml) during a period of 10 min at 70–80 oC, and a few drops of trifluoroacetic acid were added as catalyst. The mixture was heated in a water bath for 5 h under reflux. The product was filtered, and the obtained precipitate was washed with hot EtOH. The resultant product was dried at room temperature. Purple solid; yield: 86%; m. p. 110–112 oC. 1H NMR (DMSO– d6, 400 MHz, ppm); δ: 10.26 (s, 1H), 8.68 (s, 1H), 8.02 (d, 1H, J= 2.8 Hz), 7.90 (dd, 1H, J= 9.4 Hz and 2.8 Hz), 7.80 (d, 1H, J= 2.4 Hz), 7.65 (d, 1H, J= 8.8Hz), 7.50 (dd, 1H, J= 8.8 Hz and 2.4 Hz), 6.74 (d, 1H, J= 9.4 Hz), 4.73 (br, 1H), 3.73 (t, 2H, J= 6.4 Hz), 3.51 (t, 2H, J= 6 Hz), 1.84 (m, 2H). IR (KBr, cm-1); 1645 (C=N), 1614 (C=C), 1575 (phenol ring), 1456 (N=N), 1284 (C–O). Anal. Calcd. For C16H15Cl2N3O2: C, 54.56; N, 11.93; H, 4.29%. Found: C, 55.62; N, 12.16; H, 4.10%. λmax (nm) (ε(M-1.cm-1)): 255 (12175), 265(12325), 400 (23225) and 435 (20225) in DMSO.
2.
Results and Discussion
2.1. Synthesis and Characterization A new asymmetrical azo-Schiff base receptor (L) has been synthesized via the condensation reaction of an azo-coupled precursor with 3-amino-1-propanolin ethanol in good yield. All resultant products were characterized using standard spectroscopic techniques (Figs S1 and
S2, Supplementary Material). The total absence of the ν(C=O) band at 1666 cm−1 in the infrared spectrum of the prepared dye (reactant aldehyde) together with the appearance of a new ν(C=N) band at 1645 cm−1 (product L) clearly indicated that a new Schiff base compound had formed. In the 1H NMR spectrum of the receptor L, the singlet resonance at 10.26 ppm can be attributed to the phenolic proton, whereas the singlet signal at 8.68 ppm was assigned to the imine proton [50]. Furthermore, results of the C, H, and N elemental analyses are in agreement with the molecular formula.
2.2. Electronic Absorption Spectra The electronic absorption spectrum of the receptor L (4×10−5 mol.L−1) in DMSO displayed a band in the 260–270 nm wavelength that was assigned to the excitation of the π electrons of the aromatic system. The second band observed in the wavelength range of 390–405 nm could be due to the π→π* transition of azo and azomethine chromophores. The less intense shoulder located in the wavelength range of 430–465 nm was due to an intra-molecular charge transfer transition within the whole molecule of the receptor (L) [51–52]. 2.2.1.
Solvent Effect on the Electronic Spectra
The absorption spectra of receptor L in various solvents are shown in Fig. 1. It has been proved that the electron transitions of azo–azomethine compounds depend strongly on the nature of the media [46]. To assess the solvatochromic effect, the electronic absorption spectra of L (4⤬10−5 mol.L−1) in some organic solvents with different polarities were recorded at room temperature. As expected, the influence of solvents on the prepared dyes increased in the order of DMSO > DMF > CH3CN > THF > methanol > CHCl3 > dioxane. It appeared that the absorption band at 435–450 nm generally showed a hypsochromic shift (negative solvatochromism) as the polarity of the solvent increased, implying a reduction in the dipole moment upon electron excitation. The other band at 365–400 nm showed a bathochromic shift (positive solvatochromism) upon increasing solvent polarity. This positive
solvatochromism may be due to the effect of dipole moment changes of the excited state and/or changes in the hydrogen bonding strength in polar solvents [46,47]. The resulting values are summarized in Table 1.
2.2.2.
Spectroscopic Studies of Sensor L for Anion Sensing in Organic Media
At first, the chemosensing characteristics of receptor L were detected visually. Then, absorption spectral studies were performed on sensor L (4⤬10−5 mol.L−1) in DMSO upon addition of 5 equiv. of typical anions (5⤬10−4 mol.L−1) such as F−, Cl−, Br−, NO3−, HSO4− and H2PO4− as their tetrabutylammonium salts to demonstrate the selectivity of sensor L as a colorimetric sensor. As shown in Fig. 2, only F− and H2PO4− ions could induce the sensor to form a clear red shift near 115 nm and 105 nm with a distinct red and orange color change, respectively, whereas the other anions had no influence on the absorption spectra and color change (Fig. S3). Sensor L (4⤬10−5 mol.L−1) in DMSO had a yellow color with an absorption maximum at 400 nm. Upon addition of 5 equiv. of F− in organic solution, an obvious red shift up to 115 nm (from 400 to 515 nm) appeared immediately, and a color change of the solution from yellow to red was observed. As shown in Fig. 3, with incrementally added amounts of fluoride ions, the absorption band at 400 nm progressively decreased, and a new band centered at 515 nm gradually formed with a clear isosbestic point at 460 nm. Moreover, the conclusive stoichiometric ratio between L and F− was determined to be 1:2 with the help of Job’s plot experiments [53]. The binding constant of complexation was calculated using the Benesi–Hildebrand method [54] (Fig. S4). The calibration curve at 515 nm (plotting of absorbance versus concentration of complex (L plus F−) showed two different steps. By separation of these steps, a linear relationship appeared for each step with different slope, verifying that L interacts with F− in a 1:2 stoichiometric ratio. There are three proposed
proofs for this kind of behavior: (1) in the first step, increasing the added amounts of fluoride ions causes hydrogen bonding to form between alcoholic O–H and F−, followed by hydrogen bonding formation between phenolic O–H and F− in the next step; (2) another logic explanation of this phenomenon is that sensor L interacts with F− by hydrogen bonding in the first step, and deprotonation during the addition of fluoride ions occurs in the second step; [55] (3) the analysis showed that the titration curves were consistent with the formation of two complexes, namely 1:1 and 1:2 (L:F− ) [56]. The binding constants K1 and K2 of the sequential equilibrium were obtained from the Benesi–Hildebrand method (Fig. S4) and are given in Table 2. Correspondingly, upon addition of 5 equiv. of H2PO4− in DMSO to the solution of sensor L, an evident red shift near 105 nm (from 400 to 505 nm) appeared instantly, and a color change of the solution from yellow to orange was observed. As shown in Fig. 4, with incremental additions of H2PO4− ions to the solution of the sensor, the intensity of the absorption band at 400 nm gradually decreased and a new absorption band centered at 505 nm progressively formed, causing an isosbestic point at 455 nm. By using Job’s method, the stoichiometric ratio between receptor L and F− or H2PO4− was determined to be 1:2. The structure of F− and H2PO4− complexes with receptor L are shown in Scheme 2. The binding constants of the sequential equilibria analyzed using the Benesi–Hildebrand equation are given in Table 2 and Fig. S5. The results detailed above prove that sensor L in DMSO could be used as a highly selective colorimetric sensor for fluoride and H2PO4− ions in organic solution with conspicuous color and spectral changes.
2.2.3.
Competition Study for Anions
The preferential selectivity of L as a colorimetric chemosensor for the detection of F− was studied in the presence of various competing anions (Fig. S6). For the F− competition test, the receptor (L) was treated with 4 equiv. of F− in the presence of 4 equiv. of other anions [57].
As illustrated in Fig. 5, no interference was observed in the detection of F− in the presence of other anions. A similar competition test (detailed above) for H2PO4− was performed with 4 equiv. of H2PO4− in the presence of 4 equiv. of other anions (Fig. S7). Notably, with the exception of F− the presence of other interfering anions had no effect on the absorbance spectra. In the competition of F− and H2PO4− however, the fluoride anion is the winner fragment, as shown in Fig. 6. This result implies that L could be an excellent sensor for selectively detecting F− in the presence of the competing anions studied. Furthermore, to check the influence of water on the binding property, two distilled water titration experiments of L containing 3 equiv. of F− and H2PO4− were carried out (Fig. S8). Almost identical results were obtained, indicating that water affected the binding interaction of receptor L with F− and H2PO4−.
2.2.4.
Absorption Spectra for Cation Sensing
The recognition ability of receptor L (4⤬10−5 mol.L−1) by naked-eye colorimetric experiments for Cu2+, Cr3+ , Al3+, and Fe3+ as their chloride salts (5⤬1−4 mol.L−1) in DMSO/water 9:1 was investigated. The receptor (L) showed color changes from yellow to green, light green, colorless, and light bronze in the presence of Cu2+, Cr3+ , Al3+, and Fe3+, respectively. Whereas other metal chloride ions i.e. Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, and Pb2+ caused no significant change in color (Fig. 7). Upon incremental addition of Al3+, Cu2+ , Cr3+ and Fe3+ to L, the peak at 460 nm gradually decreased and a new band for each metal ion appeared in the range of 360-370 nm with a hypsochromic shift, whereas other metal ions caused no apparent change in absorption spectra (Fig. 7). The length of the alkyl unit with a hydroxyl group is very important becausethe receptor must act as a chelate ligand to absorb the cations. The geometry of the complex has a great effect on the positions of π→π* or n→π* transitions [58]. With progressive additions of Al3+ to L, a new absorption band at 360
nm appeared and the peak at 460 nm gradually decreased (Fig. 8). Moreover, upon incremental addition of Cu2+ to L, the peak at 460 nm gradually decreased and a new band at 365 nm appeared with a hypsochromic shift. Upon successive additions of Cr3+ and Fe3+, similar changes in the L spectrum were observed (Fig. S9). Distinct isosbestic points at 385 nm for Cu2+ and Fe3+ and at 380 nm for Al3+ and Cr3+ were apparent, which indicated the formation of only one active complex with the receptor. It isnotable that many of these metal cations only in DMSO had no influence on the absorption spectra and distinct color change (Fig. S10). The results of the Job’s plot analysis forbinding between L and Al3+ showed a 2:1 stoichiometry (Fig. 9). The proposed structure of the receptor (L) and Al3+ is shown in Scheme 3. Correspondingly, the 2:1 binding stoichiometry for L with Cu2+, Cr3+, and Fe3+ cations was also substantiated by Job’s plot experiments (Fig. S11). Assuming a 2:1(L: metal ion) complex formation, the binding constant (Ka) was calculated on the basis of the titration curves of sensor L with the above-named cations using the Benesi–Hildebrand method (Fig. S12), and the resulting values are summarized in Table 3. Furthermore, the detection limit of receptor L for the analysis of Al3+, Cr3+, Cu2+, and Fe3+ was determined through standard deviations and linear fittings [59]. By plotting the absorbance changes as a function of concentration, the detection limits of L for the mentioned cations were calculated, and the resulting values are summarized in Table 3.
2.2.5.
Competition Study for Cations
The selectivity towards Al3+ was further clarified by the competitive binding experiment. To perform this, the receptor L (4⤬10-5 mol.L−1) was treated with Al3+ in the presence of 10 equiv of other competing metal ions in DMSO/H2O (9:1, v/v). As illustrated in Fig. 10 except for Cr3+, Fe3+ and Cu2+, other background metal ions had no conspicuous interference with
the detection of Al3+ ions at 360 nm. So, the chemosensor L has revealed a good practical ability to recognize Al3+ in the aqueous solution.
3.3 1
1
H NMR Titration of Sensor L with F−
H NMR spectroscopy is usually considered an imperative characterization technique to
present direct evidence in favor of ion–receptor complexation [60].
In this study, the
interaction of the receptor with tetrabutylammonium fluoride (TBAF) through 1H NMR studies in CDCl3 was investigated. Before the addition of anion, in the 1H NMR spectrum of the receptor (Fig. 11), the two observed singlet resonances at 10.26 and 8.68 ppm can be attributed to the phenolic proton and imine proton, respectively. After adding 2 equiv. of fluoride ions, the resonance at 10.26 ppm corresponding to the phenolic proton disappeared. In addition, a broad peak at 4.73 ppm in the free receptor was attributed to the disappearance of alcoholic OH due to deprotonation with F¯ (Fig. 12). This demonstrates that the interaction of anions through the phenolic and alcoholic OH had been occurred. With the continuous addition of fluoride ions, a new signal appeared at 15.92 ppm, indicating the formation of HF2− in the 1H NMR spectrum [48, 49, 55]. The aromatic protons Hd, He, Hc, and Hf shifted up-field, which suggests that the negative charges developed from the deprotonation of L by F¯ were delocalized through the whole receptor molecule. [61] As seen in Fig. 12, upon addition of TBAF to the solution of receptor, several resonances appear in the aliphatic section in the range of 1–4 ppm, corresponding to the protons of tetrabutylammonium salts.
3.4.
pH Effect
To check the pH effect on the host–guest binding affinity, the absorption band of receptor L at 515 nm attributed to the formation of the L–anion complex under different pH conditions was examined. As seen in Fig. 13, the absorbance versus pH plot showed a rapid growth in
the pH range of 3–12, and the color of the L–F¯ complex changed from light yellow to red. The result showed that receptor L is a sensitive sensor with respect to pH and could be applied in physiological systems. As seen in Fig. 13, the absorption of L–F¯ complex is the same as the absorption of the complex at pH= 12; this means that the fluoride ions act as a base in the receptor (L) solution.
4. Conclusion Compound L proved to be a colorimetric fluoride (F−), di-hydrogen phosphate (H2PO4−), and aluminum(III) sensor. This new chromogenic receptor shows selective coloration for the above-named ions. The sensor showed a color change upon the addition of fluoride or dihydrogen phosphate ion with a substantial red shift. No significant color change was observed upon the addition of other anions i.e. Cl−, Br−, NO3−, and HSO4− in DMSO. The binding constants of receptor L with fluoride or di-hydrogen phosphate ions showed that the electrostatic interaction between OH groups of the receptor and anions had occurred. The easy-to-prepare test kit based on the receptor system provides a convenient and reliable detection of fluoride (F−), di-hydrogen phosphate (H2PO4−), and aluminum (III) ions in everyday applications.
5. Acknowledgments The authors would like to thank the Research Council of Arak University for financial support of this research.
6. References
[1] A. Ghorai, J. Mondal Chandra, G.K. Patra, A reversible fluorescent-colorimetric iminopyridylbis-Schiff base sensor for expeditious detection of Al3+ and HSO3− in aqueous media, Dalton Trans. 44 (2015) 13261-13271. [2] A. Barba-Bon,A.M. Costero, S. Gil, M. Parra, J.R. Soto, A new selective fluorogenic probe for trivalent cations, Chem. Commun. 48 (2012) 3000–3002. [3] G. Nordberg, Handbook on the Toxicology of Metals, Academic Press: New York, 2007, pp: 529-600. [4] S.K. Sahoo, D. Sharma, R.K. Bera, G. Crisponi, J.F. Callan, Iron (III) selectivemolecular and supramolecular fluorescent probes, Chem. Soc. Rev. 41 (2012) 7195-7227. [5] E.C. Theil, D.J. Goss, Living with iron (and Oxygen): Questions and answers about iron homeostasis, Chem. Rev. 109 (2009) 4568-4579. [6] H. Arakawa, R. Ahmad, M. Naoni, H-A.Tajmir-Riahi, A comparative study of calf thymus DNA binding to Cr(III) and Cr(VI) ions. Evidence for the guanine N-7-chromiumphosphate chelate formation, J. Biol. Chem. 275(2000) 10150-10153. [7] H. Wu, H., Zhou, J. Wang, L. Zhao, C. Duan, Dansyl-based fluorescent chemosensors for selective responses of Cr(III), New J. Chem. 33 (2009) 653-658. [8] V. Geraldes, M. Mihalma, M.N. Pinho, A. Aril, H. Ozqunoy, B.O. Bitlishi, O. Savi, O. Environmental Contamination and Toxicology, Pol. J. Environ. Stud. 18 (2009) 353-357. [9] O.F.H. Cobos, J.F.A. Londono, L.C. Garcia, Diseno de un biofiltropara reducer el indice de contaminacionporcromogenerado en lasindustrias del curtido de cueros, Dyna Rev. Fac. Nac. Minas. 160 (2009) 107-119. [10] A.K. Susheela, M. Bhatnagar, K. Vig, N.K. Mondal, Excess fluoride ingestion and thyroid hormone derangements in children living in Delhi, India, Fluoride 38 (2005) 98-108.
[11] Y. Ding, Y. Gao, H. Sun, H. Han, W. Wang, X. Ji, X. Liu, D. Sun, Developmental Fluoride neurotoxicity: A systematic review and meta-analysis, J. Hazard. Mater. 186 (2011) 1942-1946. [12] A.J. Atwood, J.E.D. Davies, D.D. Macnicol, F. Vogtle, Comprehensive Supramolecular Chemistry, Pergamon Press: New York, 1996. [13] P.J. Cragg, Supramolecular Chemistry from Biological Inspiration to Biomedical Applications, Springer, Science + Business Media, 2010. [14] R. Martinez-Manez, F. Sancenon, Fluorogenic and chromogenic chemosensors and reagents for anions, Chem. Rev. 103 (2003) 4419-4476. [15] P.A. Gale, Anion and ion-pair receptor chemistry: highlights from 2000 and 2001, Coord. Chem. Rev. 240 (2003) 191-221. [16] J.W. Steed, Coordination and organometallic compounds as anion receptors and sensors, Chem. Soc. Rev. 38 (2009) 506-519. [17] S. Kubik, Cyclopeptide derived synthetic receptors in: artificial receptors for chemical sensors, Chem. Soc. Rev. 39 (2010) 3648-3663. [18] L.A. Joyce, H.S. Shabbir, E.V. Anslyn, The uses of supramolecular chemistry in synthetic methodology development: Examples of anion and neutral molecular recognition, Chem. Soc. Rev. 39 (2010) 3621-3632. [19] C. Caltagirone, P.A. Gale, 2-Aminoindole based anion receptors, Chem. Soc. Rev. 38 (2009) 520-563. [20] P.A. Gale, S.E. Garcia-Garrido, J. Garric, Anion receptors based on organic frameworks: highlights from 2005 and 2006, Chem. Soc. Rev. 37 (2008) 151-190. [21] M. Vazquez, L. Fabbrizzi, A.Taglietti, R.M. Pedrido, A.M. Gonzalez-Noya, M.R. Bermejo, A colorimetric approach to anion sensing: A selective chemosensor of fluoride
ions, in which color is generated by anion-enhanced π delocalization, Angew. Chem. Int. Ed. 43(2004) 1962-1965. [22] P.A. Gale, R. Quesada, Anion coordination and anion-templated assembly: Highlights from 2002 to 2004, Coord. Chem. Rev. 250 (2006) 3219-3244. [23] T. Gunnlaugsson, M. Glynn, G.M. Tocci, P.E. Kruger, F.M. Pfeffer, Supplementary material (ESI) for organic and biomolecular chemistry, Coord. Chem. Rev. 250 (2006) 30943117. [24] B.A. Moyer, L.H. Delmau, C.J. Fowler, A. Ruas, D.A. Bostick, J.L. Sessler, E. Katayeu, G.D. Pantos, J.M. Llinares, M.A. Hossain, S.O. Kang, K. Bowman-James, Supramolecular chemistry of environmentally relevant anions, Advances in Inorg. Chem. 59 (2006) 175-204. [25] H. Luecke, F.A. Quiocho, High specificity of a phosphate-transport protein determined by hydrogen-bonds, Nature 347 (1990) 402-406. [26] J.J. He, F.A. Quiocho,A nonconservative serine to cysteine mutation in the sulfatebinding protein, a transport receptor, Science 251(1991) 1479-1481. [27] E.V. Anslyn, J. Smith, D.M. Kneeland, K. Ariga, F.Y. Chu, Strategies for phosphodiester complexation and cleavage, Supramol. Chem. 1 (1993) 201-208. [28] J.E. McKee, H.W. Wolf, Water Quality Criteria, Second Ed., California State Water Quality, Control Board: Sacramento, CA., 1993. [29] V.K. Saluja, P.Saluja, G. Hundal, M.S. Hundal, N. Singh, D.O. Jang, Benzthiazolebased multifunctional chemosensor: fluorescent recognition of Fe3+ and chromogenic recognition of HS O 4 − , Tetrahedron 69 (2013) 1606-1610. [30] N.R. Song, J.H. Moon, J. Choi, E.J. Jun, Y. Kim, S-J. Kim, J.Y. Lee, J. Yoon, Cyclic benzobisimidazolium derivative for the selective fluorescent recognition of HSO4− via a combination of C–H hydrogen bonds and charge interactions, Chem. Sci. 4 (2013) 17651771.
[31] P. Kaur, H. Kaur, K. Singh, A ‘turn-off’ emission based chemosensor for HSO4− – formation of a hydrogen-bonded complex, Analyst 138 (2013) 425-428. [32] S.T.Yang, D.J. Liao, S.J. Chen, C.H. Hu, A-T.Wu, A fluorescence enhancement-based sensor for hydrogen sulfate ion, Analyst 137 (2012) 1553-1555. [33] D. Sarkar, A.K. Pramanik, T.K. Mondal, Coumarin based dual switching fluorescent ‘turn-on’ chemosensor for selective detection of Zn
2+
and HSO4−: an experimental and
theoretical study, RSC Adv. 4 (2014) 25341-25347. [34] U. Fegade, S.K. Sahoo, A. Singh, P. Mahulikar, S. Attarde, N. Sing, A. Kuwar, A selective and discriminating noncyclic receptor for HSO4− ion recognition, RSC Adv. 4 (2014) 15288-15292. [35] P.F. Schmidtchen, M. Berger, Artificial organic host molecules for anions, Chem. Rev. 97 (1997) 1609-1645. [36] C.R. Bondy, P.A. Gale, S.J. Loeb, Metal-organic anion receptors: arranging urea hydrogenbond donors to encapsulate sulfate ions, J. Am. Chem. Soc. 126 (2004) 5030-5031. [37] G. Ambrosi, C. Battelli, M. Formica, V.Fusi, L. Giorgi, M.
Micheloni, R.
Pontellini, L. Prodi, Two polyaminophenolic fluorescent chemosensors for H+ and Zn(II). Spectroscopic behaviour of free ligands and of their dinuclearZn(II) complexes, New J. Chem. 33 (20009) 171-180. [38] A.M.L. Nickel, F. Seker, B.P. Ziemert, A.B. Ellis, Imprinted poly(acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence, Chem. Mater. 13 (2001) 1391-1397. [39] R. Martınez-Manez, F. Sancenon, Fluorogenic and chromogenic chemosensors and reagents for anions, Chem. Rev. 103 (2003) 4419-4476.
[40] H.S. Jung, M. Park, D.Y. Han, E. Kim, C. Lee, S.Ham, SJ.S. Kim, Cu2+ ion-induced self-assembly of pyrenylquinoline with a pyrenylexcimer formation, Org. Lett. 11 (2009) 3378-3381. [41] Z.X. Li, L.F. Zhang, W.Y. Zhao, X.Y. Li, Y.K. Guo, M.M. Yu, Fluoranthenenorg based pyridine as fluorescent chemosensor for Fe3+, Inorg, Chem. Comm. 14 (2011) 656-1658. [42] J. Shao, H. Lin, H. Lin, A novel chromo- and fluorogenic dual responding H2PO4− receptor based on an azo derivative, Dyes Pig. 80 (2009) 259-263. [43] P. Vigato, S. Tamburini, L. Bertolo, The development of compartmental macrocyclic Schiff bases and related polyamine derivatives, Coordination Chemistry Reviews 251 (2007) 1311-1492. [44] A. Jiménez-Sánchez, N. Farfán, R. Santillan, Multiresponsive Photo-, Solvato-, Acido-, and Ionochromic Schiff Base Probe, The Journal of Physical Chemistry C, 119 (2015) 1381413826. [45] P.S. Nayab, M. Pulaganti, S.K. Chitta, A New Isoindoline Based Schiff Base Derivative as Cu (II) Chemosensor: Synthesis, Photophysical, DNA Binding and Molecular Docking Studies, Journal of Fluorescence 25 (2015) 1763-1773. [46] P.S. Nayab, M. Pulaganti, S.K. Chitta, M. Abid, R. Uddin, Evaluation of DNA Binding, Radicals Scavenging and Antimicrobial Studies of Newly Synthesized NSubstituted Naphthalimides: Spectroscopic and Molecular Docking Investigations, Journal of Fluorescence, 25 (2015) 1905-1920. [47] R. Arabahmadi, M. Orojloo, S. Amani, Azo Schiff bases as colorimetric and fluorescent sensors for recognition of F−, Cd2+ and Hg2+ ions, Anal. Methods 6 (2014) 7384-7393. [48] R. Arabahmadi, S. Amani, A new fluoride ion colorimetric sensor based on azo– azomethine receptors, Supra. Chem. 26 (2014) 321–328.
[49] R. Arabahmadi, S. Amani, Synthesis and studies of selective chemosensors for anions and cations byazo-containingsalicylaldimine-based receptors, J. Coord. Chem. 66 (2013) 218–226. [50] Z. Shaghaghi, Spectroscopic properties of some new azo–azomethine ligands in the presence of Cu2+, Pb2+, Hg2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 131 (2014) 67-71. [51] A.M. Khedra, M. Gaberb, R.M. Issaa, H. Erten, Synthesis and spectral studies of 5-[3(1, 2,4-triazolyl-azo]-2, 4-dihydroxybenzaldehyde (TA) and its Schiff bases with 1, 3diaminopropane (TAAP) and 1, 6-diaminohexane (TAAH). Their analytical application for spectrophotometric micro-determination of cobalt(II). Application in some radiochemical studies, Dyes Pig. 67 (2005) 117–126. [52] E. Ispir, The synthesis, characterization, electrochemical character, catalytic and antimicrobial activity of novel, azo-containing Schiff bases and their metal complexes, Dyes Pig. 82 (2009) 13–19. [53] W. Likussar, D.F. Boltz,Theory of continuous variations plots and a new method for spectrophotometric determination of extraction and formation constants, Anal. Chem. 43 (1971) 1265-1272. [54] H.A. Benesi, J.H. Hildebrand, A spectrophotometric investigation of the interaction of iodine with aromatic hydrocarbons, J. Am. Chem. Soc. 71 (1949) 2703–2707. [55] J. Nieboer, R. Haiges, W. Hillary, X. Yu, T. Richardet, H.P.A. Mercier, M. Gerken, Fluoride-ion acceptor properties of WSF4: Synthesis, characterization, and computational study of the WSF5– and W2S2F9– anions and
19
F NMR spectroscopic characterization of the
W2OSF9– anion, Inorg. Chem. 51 (2012) 6350–6359.
[56] J. Manojkuma, J. Nagendra-Babu, V. Bhalla, N. Sighathwal,Visible colorimetric sensor for fluoride ion based on o-phenylenediamine, Supra. Chem. 19 (2007) 511-516. [57] J. Xiong, L. Sun, Y. Liao, G.N.
Li, J.L. Zuo, X.Z. You, A new optical and
electrochemical sensor for fluoride ion, Tetrahedron Lett. 52 (2011) 6157-6161.
[58] H.W. Richardson, W.E. Hatfield, On the superexchange mechanism in polymeric, pyrazine-bridged copper(II) complexes, J. Am. Chem. Soc. 98 (1976) 835-839. [59] J. Miller, J.C. Miller,Statistics and Chemometrics for Analytical Chemistry, 6th Ed., Published by: Melih Bayar. 2014. [60] S. Chall, S.S. Mati, S. Konar, D.Singharoy, S. Chandra Bhattacharya, An efficient, Schiff-base derivative for selective fluorescence sensing of Zn2+ ions: Quantum chemical calculation appended by real sample application and cell imaging study, Org. Biomol. Chem. 12 (2014) 6447-6456. [61] S. Park, K. Hong, J. Hong, H. Kim, Azo dye-based latent colorimetric chemodosimeter for the selective detection of cyanides in aqueous buffer, Sens. Actuators, B 174 (2012)140– 144.
Table 1. Absorption spectral data of (L) in various organic solvents; λmax /nm (ε(M-1 cm-1)):
Receptor
L
DMSO 255 (12200) 265 (12300) 400 (23200) 435 (20200)
DMF 255 (22000) 270 (14000) 385 (21600) 440 (14200)
CH3CN
THF
270 (16700) 280 (8700) 365 (23600) 290 (8300) 380 (25000) 375 440 (12600) (20000) 440 (5400)
MeOH 270 (23200) 370 (32700) 385 (36600)
CHCl3
Dioxane
255 (14100) 280 (18800) 375 (38000) 445 (8300)
270 (16000) 365 (34500) 440 (5000)
Table 2. Data obtained from the UV-Vis spectra upon titration of receptor (L) with TBAF and TBAH2PO4 in DMSO.
Receptor, λmax(nm)
Receptor + anion
Complex, λmax(nm)
Bathochromic shift, ∆λmax(nm)
Isosbestic point, (nm)
Ka (M-1)
LOD(M)
L – F¯
400
515
115
460
K1=1.50⤬104 K2=0.2
1.66⤬10-6
L – H2PO4¯
400
505
105
455
K1=8.20⤬103 K2=1.53⤬102
1.24⤬10-6
Table 3. Data obtained from the UV-Vis spectra upon titration of receptor L (4⤬10-5 mol.L-1) with cations in 9:1 DMSO/water
Receptor, λmax (nm)
receptor + cations L –Cr+3 L –Fe+3 L –Cu+2 L –Al+3
Complex, λmax(nm)
460 460 460 460
360 360 365 360
Hypsochromic Isosbestic shift, ∆λmax(nm) point,(nm) -100 -100 -95 -100
380 385 385 380
Ka (M-1) 3.20 ⤬104 4.71 ⤬104 3.40 ⤬ 104 1.86 ⤬104
LOD (M) 2.28⤬10-6 1.99⤬10-6 2.95⤬10-6 3.02⤬10-6
Schemes, Tables and Figures:
HO Cl
N
OH EtOH
N
OH
reflux
Cl C O H
N
H 2N
N
C H
Cl
Cl
Scheme 1. Synthesis of sensor (L)
N
OH
Fig. 1The absorption spectra of (L) in organic solvents with different polarities
Fig. 2 UV–Vis absorption spectra of sensor L (4⤬10-5 mol.L-1 in DMSO) in the presence of 5 equiv. of different anions (5⤬10−4 mol.L-1), from left to right: free (L), H2PO4¯, F¯, Cl¯, Br¯,NO3¯, HSO4¯ (as their TBA salts).
Fig. 3 Absorption spectra changes of L (4⤬10-5 mol.L-1) after addition of increasing amounts of F¯ ions (0-5 equivalent) in DMSO at room temperature. Insets: above; Absorption at selected wavelengths versus the number of equivalents of F¯ added. Down; Job plot of L with F¯ at 515 nm
Fig. 4 Absorption spectra changes of L (4⤬10-5 mol.L-1) after addition of increasing amounts of H2PO4¯ ions (0-5equivalent) in DMSO at room temperature. Insets: Absorption at selected wavelengths versus the number of equivalents of H2PO4¯ added. Job's plot of L with H2PO4¯ at 505 nm
OH HO
P OH
Cl
Cl
N
C H
O OH
O N
O
N
P
OH
F H
OH
H
O
O
N Cl
N
Cl
Scheme 2. Proposed structure of F¯ and H2PO4¯ anions with receptor (L)
Fig. 5 Effect of competitive anions on the interaction between (L) and F¯
C H
F
N
O
Fig. 6 Effect of competitive anions on the interaction between (L) and H2PO4¯
Fig. 7 UV–Vis absorption spectra of sensor L (4 ⤬ 10-5 mol.L-1 in 9:1 DMSO/ water) in the presence of 3 equiv. of different cations, from left to right: free (L), Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Cd2+, Pb2+, Al3+.
Fig. 8 Absorption spectra changes of (L) (4⤬10-5 mol.L-1) after addition of increasing amounts of Al+3 ions (0-3 equivalent) in 9:1 DMSO/water at room temperature. Insets: above; Absorption at selected wavelengths versus the number of equivalents of cation added down; Benesi–Hildebrand plot of receptor (L) with Al+3 ions
Fig. 9 The Job's plot for 2:1 complex of sensor (L) with Al+3
H O O N Cl
Cl
N
C
N
N
Al
C
Cl N
Cl
N
O O
H
Scheme 3. Proposed structure of receptor (L) with Al(III) complex.
Fig. 10 Effect of competitive cations on the interaction between (L) and Al3+ ion
Fig. 111H NMR titration plot of sensor (L) with F¯ in CDCl3
Fig. 12 1H NMR titration plot of sensor L before (a) and after addition of 2 equivalent of TBAF (b) in CDCl3 (expand of aliphatic section)
Fig. 13 Effect of pH on the UV–Vis spectra of receptor (L) (2⤬10-5 mol.L-1) containing TBAF at 515 nm
Graphical Abstract: Receptor (L) proved to be a colorimetric fluoride (F−), di-hydrogen phosphate (H2PO4 − ) and aluminum (III) sensor. This new chromogenic receptor shows a selective coloration for the above ions. The sensor showed a color change upon addition of fluoride or di-hydrogen phosphate or aluminum(III) ions.
Highlights: 1) A new chromogenic receptor was designed for low cost detection of various biologically anions and cations. 2) A sensor for detecting Fluoride (F−), di-hydrogen phosphate (H2PO4−) and aluminum (III) ions. 3) The receptor is highly selective for Fluoride (F−) based on the interaction of F− and OH groups of the receptor (L). 4) Solution of the receptor is colored in DMSO and colorless when an aluminum (III) is added. 5) The binding constant (Ka) and stoichiometry of the host–guest complexes were
determined by the Benesi–Hildebrand (B–H) plot and Job's method.
PII: DOI: Reference:
S0039-9140(16)30467-2 http://dx.doi.org/10.1016/j.talanta.2016.06.042 TAL16672
To appear in: Talanta Received date: 24 December 2015 Revised date: 18 June 2016 Accepted date: 20 June 2016 Cite this article as: Masoumeh Orojloo and Saeid Amani, Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative, Talanta, http://dx.doi.org/10.1016/j.talanta.2016.06.042 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative Masoumeh Orojlooa and Saeid Amania,* a
Department of Chemistry, Faculty of Sciences, Arak University, Dr. Beheshti Avenue, Arak
38156-8-8349, Iran. *
Corresponding author. Email: [email protected]
ABSTRACT A new chromogenic receptor, 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol, has been designed and synthesized for quantitative and low-cost detection of various biological anions and cations. The dye was characterized by elemental analyses, infrared, UV-visible spectroscopy, and NMR spectroscopy. Upon the addition of F− and H2PO4− to the solution of chemosensor in DMSO, the dramatic naked eye detectable color changes were observed from yellow to red and orange with a limit of detection (LOD) of 1.66⤬10-6 mol.L−1 and 1.24 ⤬10-6 mol.L−1
at room temperature, respectively. The
chemosensor showed visual changes towards cations, such as Al3+, Cu2+, Fe3+, and Cr3+, in DMSO/water (9:1). The detection limit of receptor L for the analysis of Al3+ ion was calculated to be 3.02 ⤬10-6 mol.L−1. The anion recognition property of the receptor via proton transfer was monitored by UV-visible titration and 1HNMR spectroscopy. The binding constant (Ka) and stoichiometry of the host–guest complexes formed were determined by the Benesi–Hildebrand (B–H) plot and Job’s method, respectively.
Keywords: Chemosensor; Schiff-base receptors; Naked-eye detection of F¯, H2PO4¯ and Al3+ 1. Introduction
Ions have essential effects in nature; however, in excess, they can be dangerous for living systems and the environment. For example, aluminum (III) ion is found abundantly in nature, such as in drinking water contamination, and can be toxic to humans in excessive amounts. Many symptoms of aluminum toxicity mimic those of Alzheimer’s disease, Parkinson’s disease, and osteoporosis [1,2]. Copper ion, which plays a very important role in living systems (tyrosinase, ferroxidase, and many others), is poisonous to living cells. The presence of free copper ion can cause blood hemolysis, or kidney and liver damage [2–4]. Furthermore, it is an environment pollutant that causes concern in industry and agriculture [5–9]. Fluoride ion is a component of toothpastes. In high amounts, it is toxic and produces dental fluorosis [10,11]. Molecular receptors have received great attention in the last two decades, possibly because of the great importance of the complexation of cations and anions in areas such as chemistry, biology, pharmaceutics, environment, and industry [12–23]. Molecular receptors allow quick and selective ion recognition. The synthesis of chemosensors for the recognition of harmful and toxic ions is very important challenge, nowadays [24–33]. Cation receptors have been studied extensively, whereas anion receptors have received less attention. The rationales of the challenge that developing reliable sensing methods for anions represents include (1) anions are larger than cations with the same electronic configuration and, therefore, have a lower charge-to-radius (surface) ratio, a feature that makes the electrostatic binding of anions to receptors less effective; [34] (2) anions have a wide range of geometries and are often present in the most stable forms, resulting in higher complexity in the design and preparation of receptors; and (3) anions are pH sensitive because they can absorb protons at low pH to become neutral molecules. Therefore, to obtain the desired selectivity, a combination of electrostatic attraction and hydrogen bonding, and a suitable framework onto which these structural components can be assembled need to be taken into consideration when designing artificial anionic hosts [35].
Chemosensors are based on molecules that can bind selectively and reversibly with an anion or a cation [36]. However, most of these are designed to rely on the same principles, namely, that the functional moiety is covalently (binding site-signaling subunit approach) [37–41] or non-covalently (displacement approach) [42] linked to the signal moiety (e.g. chromogene, electrochemical group, fluorescent group). Schiff bases are common organic structures which can be easily synthesized through a one-step synthetic procedure [43]. The ionochromic behavior of Schiff bases and the interaction with a wide range of metal ions have been well documented [44]. Schiff bases containing salicyaldimine based ligands can be used in the development of cost-effective chemosensors because they show significant color changes of the solution and maxima of the absorption bond when they interact with anions and cations [45–46]. Recently, we reported aneasy and applicable method for the preparation [47] and use of low cost chemosensors based on Schiff bases for the selective detection of some toxic metal ions and anions [48,49]. Herein, we report for the first time novel colorimetric studies on cation and anion sensing by chromogenic azo-azomethine receptor (L) possessing a phenolic OH group and binds F− and H2PO4− (anion binding site). The position of azomethine (-CH=N) group in this Schiff base allows it to act as a ligand to adsorb cations (cation binding site). The behavior of this new Schiff base towards anions and cations was investigated by NMR spectroscopy and UV-visible spectroscopy in DMSO and a mixture of water/DMSO solutions. As expected, the sensor (L) could act as convenient, colorimetric, and ‘naked eye’ indicator for application as a chemosensor for biological anions and cations (Scheme 1).
1.
Experimental
1.1. Materials and Equipments
All chemicals were purchased from Sigma-Aldrich and Merck and used without further purification. Fourier transform infrared (FT-IR) spectra were recorded as pressed KBr discs using a Unicom Galaxy Series FT-IR 5000 spectrophotometer in the region of 400–4000 cm−1. Melting points were determined on an Electrothermal 9200 apparatus. Determination of C, N, and H composition was undertaken using an Elemental Analysis System, GmbH Vario EL III. Electronic spectral measurements were carried out using Optizen 3220 UV spectrophotometer in the range of 200–900 nm. NMR spectra were recorded on a Bruker AV 300 MHz and Bruker Avance III 400 MHz spectrometers.
1.2.
Synthesis of 1-(3-Formyl-4-hydroxyphenylazo)-2,4-dichlorobenzene
A mixture of 2,4-dichloroaniline (6.48 g, 40 mmol) in hydro-chloric acid (36 ml) and water (16 ml) was heated to 80 oC to form a solution. The clear solution was poured into an ice/water mixture and diazotized at 0–5 oC with sodium nitrite (2.8 g, 40 mmol) in water (10 ml). The cold diazonium solution was added to a solution of salicylaldehyde (4.88 g, 40 mmol) in water (75 ml) containing sodium carbonate (14.8 g, 40 mmol) and sodium hydroxide (1.6 g, 40 mmol) over the course of 30 min at 0 oC. The reaction mixture was first stirred for 1 h at 0 oC and then stirred for 2 h at room temperature. The product was collected by vacuum filtration and washed with NaCl solution (100 ml, 10 %). Coupling of the diazonium reagent to the salicylaldehyde occurred at the position para to the hydroxyl group. The diazo compound was dried at room temperature. Yellow solid; yield: 88%; m. p. 121– 123 oC. 1H NMR (DMSO– d6, 300 MHz, ppm); δ: 7.29 (d, 1H, J = 8.84 Hz), 8.09 (dd, 1H, J= 8.84 Hz and 2.16 Hz), 7.55 (d, 1H, J = 8.76 Hz), 7.68 (d, 1H, J =8.76 Hz), 7.89 (s, 1H), 8.19 (d, 1H, J =2.16 Hz), 10.37 (s, 1H), 11.88 (br, 1H). IR (KBr, cm-1); 1666 (CHO), 1620 (C=C), 1575 (phenol ring), 1483 (N=N), 1286 (C–O). Anal. Calcd. For C13H8Cl2N2O2: C, 52.91; N,
9.49; H, 2.73%. Found: C, 52.70; N, 9.42; H, 2.66%. λmax (nm) (ε(M-1.cm-1)): 260 (29950), 356 (49260) and 465 (11853) in DMSO.
1.3. Synthesis of Sensor L: 4-((2,4-Dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol A solution of 3-amino-1-propanol (0.15 g, 2 mmol) in absolute ethanol (EtOH; 10 ml) was added to a stirring solution of azo-coupled precursor (0.59 g, 2 mmol) in absolute EtOH (60 ml) during a period of 10 min at 70–80 oC, and a few drops of trifluoroacetic acid were added as catalyst. The mixture was heated in a water bath for 5 h under reflux. The product was filtered, and the obtained precipitate was washed with hot EtOH. The resultant product was dried at room temperature. Purple solid; yield: 86%; m. p. 110–112 oC. 1H NMR (DMSO– d6, 400 MHz, ppm); δ: 10.26 (s, 1H), 8.68 (s, 1H), 8.02 (d, 1H, J= 2.8 Hz), 7.90 (dd, 1H, J= 9.4 Hz and 2.8 Hz), 7.80 (d, 1H, J= 2.4 Hz), 7.65 (d, 1H, J= 8.8Hz), 7.50 (dd, 1H, J= 8.8 Hz and 2.4 Hz), 6.74 (d, 1H, J= 9.4 Hz), 4.73 (br, 1H), 3.73 (t, 2H, J= 6.4 Hz), 3.51 (t, 2H, J= 6 Hz), 1.84 (m, 2H). IR (KBr, cm-1); 1645 (C=N), 1614 (C=C), 1575 (phenol ring), 1456 (N=N), 1284 (C–O). Anal. Calcd. For C16H15Cl2N3O2: C, 54.56; N, 11.93; H, 4.29%. Found: C, 55.62; N, 12.16; H, 4.10%. λmax (nm) (ε(M-1.cm-1)): 255 (12175), 265(12325), 400 (23225) and 435 (20225) in DMSO.
2.
Results and Discussion
2.1. Synthesis and Characterization A new asymmetrical azo-Schiff base receptor (L) has been synthesized via the condensation reaction of an azo-coupled precursor with 3-amino-1-propanolin ethanol in good yield. All resultant products were characterized using standard spectroscopic techniques (Figs S1 and
S2, Supplementary Material). The total absence of the ν(C=O) band at 1666 cm−1 in the infrared spectrum of the prepared dye (reactant aldehyde) together with the appearance of a new ν(C=N) band at 1645 cm−1 (product L) clearly indicated that a new Schiff base compound had formed. In the 1H NMR spectrum of the receptor L, the singlet resonance at 10.26 ppm can be attributed to the phenolic proton, whereas the singlet signal at 8.68 ppm was assigned to the imine proton [50]. Furthermore, results of the C, H, and N elemental analyses are in agreement with the molecular formula.
2.2. Electronic Absorption Spectra The electronic absorption spectrum of the receptor L (4×10−5 mol.L−1) in DMSO displayed a band in the 260–270 nm wavelength that was assigned to the excitation of the π electrons of the aromatic system. The second band observed in the wavelength range of 390–405 nm could be due to the π→π* transition of azo and azomethine chromophores. The less intense shoulder located in the wavelength range of 430–465 nm was due to an intra-molecular charge transfer transition within the whole molecule of the receptor (L) [51–52]. 2.2.1.
Solvent Effect on the Electronic Spectra
The absorption spectra of receptor L in various solvents are shown in Fig. 1. It has been proved that the electron transitions of azo–azomethine compounds depend strongly on the nature of the media [46]. To assess the solvatochromic effect, the electronic absorption spectra of L (4⤬10−5 mol.L−1) in some organic solvents with different polarities were recorded at room temperature. As expected, the influence of solvents on the prepared dyes increased in the order of DMSO > DMF > CH3CN > THF > methanol > CHCl3 > dioxane. It appeared that the absorption band at 435–450 nm generally showed a hypsochromic shift (negative solvatochromism) as the polarity of the solvent increased, implying a reduction in the dipole moment upon electron excitation. The other band at 365–400 nm showed a bathochromic shift (positive solvatochromism) upon increasing solvent polarity. This positive
solvatochromism may be due to the effect of dipole moment changes of the excited state and/or changes in the hydrogen bonding strength in polar solvents [46,47]. The resulting values are summarized in Table 1.
2.2.2.
Spectroscopic Studies of Sensor L for Anion Sensing in Organic Media
At first, the chemosensing characteristics of receptor L were detected visually. Then, absorption spectral studies were performed on sensor L (4⤬10−5 mol.L−1) in DMSO upon addition of 5 equiv. of typical anions (5⤬10−4 mol.L−1) such as F−, Cl−, Br−, NO3−, HSO4− and H2PO4− as their tetrabutylammonium salts to demonstrate the selectivity of sensor L as a colorimetric sensor. As shown in Fig. 2, only F− and H2PO4− ions could induce the sensor to form a clear red shift near 115 nm and 105 nm with a distinct red and orange color change, respectively, whereas the other anions had no influence on the absorption spectra and color change (Fig. S3). Sensor L (4⤬10−5 mol.L−1) in DMSO had a yellow color with an absorption maximum at 400 nm. Upon addition of 5 equiv. of F− in organic solution, an obvious red shift up to 115 nm (from 400 to 515 nm) appeared immediately, and a color change of the solution from yellow to red was observed. As shown in Fig. 3, with incrementally added amounts of fluoride ions, the absorption band at 400 nm progressively decreased, and a new band centered at 515 nm gradually formed with a clear isosbestic point at 460 nm. Moreover, the conclusive stoichiometric ratio between L and F− was determined to be 1:2 with the help of Job’s plot experiments [53]. The binding constant of complexation was calculated using the Benesi–Hildebrand method [54] (Fig. S4). The calibration curve at 515 nm (plotting of absorbance versus concentration of complex (L plus F−) showed two different steps. By separation of these steps, a linear relationship appeared for each step with different slope, verifying that L interacts with F− in a 1:2 stoichiometric ratio. There are three proposed
proofs for this kind of behavior: (1) in the first step, increasing the added amounts of fluoride ions causes hydrogen bonding to form between alcoholic O–H and F−, followed by hydrogen bonding formation between phenolic O–H and F− in the next step; (2) another logic explanation of this phenomenon is that sensor L interacts with F− by hydrogen bonding in the first step, and deprotonation during the addition of fluoride ions occurs in the second step; [55] (3) the analysis showed that the titration curves were consistent with the formation of two complexes, namely 1:1 and 1:2 (L:F− ) [56]. The binding constants K1 and K2 of the sequential equilibrium were obtained from the Benesi–Hildebrand method (Fig. S4) and are given in Table 2. Correspondingly, upon addition of 5 equiv. of H2PO4− in DMSO to the solution of sensor L, an evident red shift near 105 nm (from 400 to 505 nm) appeared instantly, and a color change of the solution from yellow to orange was observed. As shown in Fig. 4, with incremental additions of H2PO4− ions to the solution of the sensor, the intensity of the absorption band at 400 nm gradually decreased and a new absorption band centered at 505 nm progressively formed, causing an isosbestic point at 455 nm. By using Job’s method, the stoichiometric ratio between receptor L and F− or H2PO4− was determined to be 1:2. The structure of F− and H2PO4− complexes with receptor L are shown in Scheme 2. The binding constants of the sequential equilibria analyzed using the Benesi–Hildebrand equation are given in Table 2 and Fig. S5. The results detailed above prove that sensor L in DMSO could be used as a highly selective colorimetric sensor for fluoride and H2PO4− ions in organic solution with conspicuous color and spectral changes.
2.2.3.
Competition Study for Anions
The preferential selectivity of L as a colorimetric chemosensor for the detection of F− was studied in the presence of various competing anions (Fig. S6). For the F− competition test, the receptor (L) was treated with 4 equiv. of F− in the presence of 4 equiv. of other anions [57].
As illustrated in Fig. 5, no interference was observed in the detection of F− in the presence of other anions. A similar competition test (detailed above) for H2PO4− was performed with 4 equiv. of H2PO4− in the presence of 4 equiv. of other anions (Fig. S7). Notably, with the exception of F− the presence of other interfering anions had no effect on the absorbance spectra. In the competition of F− and H2PO4− however, the fluoride anion is the winner fragment, as shown in Fig. 6. This result implies that L could be an excellent sensor for selectively detecting F− in the presence of the competing anions studied. Furthermore, to check the influence of water on the binding property, two distilled water titration experiments of L containing 3 equiv. of F− and H2PO4− were carried out (Fig. S8). Almost identical results were obtained, indicating that water affected the binding interaction of receptor L with F− and H2PO4−.
2.2.4.
Absorption Spectra for Cation Sensing
The recognition ability of receptor L (4⤬10−5 mol.L−1) by naked-eye colorimetric experiments for Cu2+, Cr3+ , Al3+, and Fe3+ as their chloride salts (5⤬1−4 mol.L−1) in DMSO/water 9:1 was investigated. The receptor (L) showed color changes from yellow to green, light green, colorless, and light bronze in the presence of Cu2+, Cr3+ , Al3+, and Fe3+, respectively. Whereas other metal chloride ions i.e. Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, and Pb2+ caused no significant change in color (Fig. 7). Upon incremental addition of Al3+, Cu2+ , Cr3+ and Fe3+ to L, the peak at 460 nm gradually decreased and a new band for each metal ion appeared in the range of 360-370 nm with a hypsochromic shift, whereas other metal ions caused no apparent change in absorption spectra (Fig. 7). The length of the alkyl unit with a hydroxyl group is very important becausethe receptor must act as a chelate ligand to absorb the cations. The geometry of the complex has a great effect on the positions of π→π* or n→π* transitions [58]. With progressive additions of Al3+ to L, a new absorption band at 360
nm appeared and the peak at 460 nm gradually decreased (Fig. 8). Moreover, upon incremental addition of Cu2+ to L, the peak at 460 nm gradually decreased and a new band at 365 nm appeared with a hypsochromic shift. Upon successive additions of Cr3+ and Fe3+, similar changes in the L spectrum were observed (Fig. S9). Distinct isosbestic points at 385 nm for Cu2+ and Fe3+ and at 380 nm for Al3+ and Cr3+ were apparent, which indicated the formation of only one active complex with the receptor. It isnotable that many of these metal cations only in DMSO had no influence on the absorption spectra and distinct color change (Fig. S10). The results of the Job’s plot analysis forbinding between L and Al3+ showed a 2:1 stoichiometry (Fig. 9). The proposed structure of the receptor (L) and Al3+ is shown in Scheme 3. Correspondingly, the 2:1 binding stoichiometry for L with Cu2+, Cr3+, and Fe3+ cations was also substantiated by Job’s plot experiments (Fig. S11). Assuming a 2:1(L: metal ion) complex formation, the binding constant (Ka) was calculated on the basis of the titration curves of sensor L with the above-named cations using the Benesi–Hildebrand method (Fig. S12), and the resulting values are summarized in Table 3. Furthermore, the detection limit of receptor L for the analysis of Al3+, Cr3+, Cu2+, and Fe3+ was determined through standard deviations and linear fittings [59]. By plotting the absorbance changes as a function of concentration, the detection limits of L for the mentioned cations were calculated, and the resulting values are summarized in Table 3.
2.2.5.
Competition Study for Cations
The selectivity towards Al3+ was further clarified by the competitive binding experiment. To perform this, the receptor L (4⤬10-5 mol.L−1) was treated with Al3+ in the presence of 10 equiv of other competing metal ions in DMSO/H2O (9:1, v/v). As illustrated in Fig. 10 except for Cr3+, Fe3+ and Cu2+, other background metal ions had no conspicuous interference with
the detection of Al3+ ions at 360 nm. So, the chemosensor L has revealed a good practical ability to recognize Al3+ in the aqueous solution.
3.3 1
1
H NMR Titration of Sensor L with F−
H NMR spectroscopy is usually considered an imperative characterization technique to
present direct evidence in favor of ion–receptor complexation [60].
In this study, the
interaction of the receptor with tetrabutylammonium fluoride (TBAF) through 1H NMR studies in CDCl3 was investigated. Before the addition of anion, in the 1H NMR spectrum of the receptor (Fig. 11), the two observed singlet resonances at 10.26 and 8.68 ppm can be attributed to the phenolic proton and imine proton, respectively. After adding 2 equiv. of fluoride ions, the resonance at 10.26 ppm corresponding to the phenolic proton disappeared. In addition, a broad peak at 4.73 ppm in the free receptor was attributed to the disappearance of alcoholic OH due to deprotonation with F¯ (Fig. 12). This demonstrates that the interaction of anions through the phenolic and alcoholic OH had been occurred. With the continuous addition of fluoride ions, a new signal appeared at 15.92 ppm, indicating the formation of HF2− in the 1H NMR spectrum [48, 49, 55]. The aromatic protons Hd, He, Hc, and Hf shifted up-field, which suggests that the negative charges developed from the deprotonation of L by F¯ were delocalized through the whole receptor molecule. [61] As seen in Fig. 12, upon addition of TBAF to the solution of receptor, several resonances appear in the aliphatic section in the range of 1–4 ppm, corresponding to the protons of tetrabutylammonium salts.
3.4.
pH Effect
To check the pH effect on the host–guest binding affinity, the absorption band of receptor L at 515 nm attributed to the formation of the L–anion complex under different pH conditions was examined. As seen in Fig. 13, the absorbance versus pH plot showed a rapid growth in
the pH range of 3–12, and the color of the L–F¯ complex changed from light yellow to red. The result showed that receptor L is a sensitive sensor with respect to pH and could be applied in physiological systems. As seen in Fig. 13, the absorption of L–F¯ complex is the same as the absorption of the complex at pH= 12; this means that the fluoride ions act as a base in the receptor (L) solution.
4. Conclusion Compound L proved to be a colorimetric fluoride (F−), di-hydrogen phosphate (H2PO4−), and aluminum(III) sensor. This new chromogenic receptor shows selective coloration for the above-named ions. The sensor showed a color change upon the addition of fluoride or dihydrogen phosphate ion with a substantial red shift. No significant color change was observed upon the addition of other anions i.e. Cl−, Br−, NO3−, and HSO4− in DMSO. The binding constants of receptor L with fluoride or di-hydrogen phosphate ions showed that the electrostatic interaction between OH groups of the receptor and anions had occurred. The easy-to-prepare test kit based on the receptor system provides a convenient and reliable detection of fluoride (F−), di-hydrogen phosphate (H2PO4−), and aluminum (III) ions in everyday applications.
5. Acknowledgments The authors would like to thank the Research Council of Arak University for financial support of this research.
6. References
[1] A. Ghorai, J. Mondal Chandra, G.K. Patra, A reversible fluorescent-colorimetric iminopyridylbis-Schiff base sensor for expeditious detection of Al3+ and HSO3− in aqueous media, Dalton Trans. 44 (2015) 13261-13271. [2] A. Barba-Bon,A.M. Costero, S. Gil, M. Parra, J.R. Soto, A new selective fluorogenic probe for trivalent cations, Chem. Commun. 48 (2012) 3000–3002. [3] G. Nordberg, Handbook on the Toxicology of Metals, Academic Press: New York, 2007, pp: 529-600. [4] S.K. Sahoo, D. Sharma, R.K. Bera, G. Crisponi, J.F. Callan, Iron (III) selectivemolecular and supramolecular fluorescent probes, Chem. Soc. Rev. 41 (2012) 7195-7227. [5] E.C. Theil, D.J. Goss, Living with iron (and Oxygen): Questions and answers about iron homeostasis, Chem. Rev. 109 (2009) 4568-4579. [6] H. Arakawa, R. Ahmad, M. Naoni, H-A.Tajmir-Riahi, A comparative study of calf thymus DNA binding to Cr(III) and Cr(VI) ions. Evidence for the guanine N-7-chromiumphosphate chelate formation, J. Biol. Chem. 275(2000) 10150-10153. [7] H. Wu, H., Zhou, J. Wang, L. Zhao, C. Duan, Dansyl-based fluorescent chemosensors for selective responses of Cr(III), New J. Chem. 33 (2009) 653-658. [8] V. Geraldes, M. Mihalma, M.N. Pinho, A. Aril, H. Ozqunoy, B.O. Bitlishi, O. Savi, O. Environmental Contamination and Toxicology, Pol. J. Environ. Stud. 18 (2009) 353-357. [9] O.F.H. Cobos, J.F.A. Londono, L.C. Garcia, Diseno de un biofiltropara reducer el indice de contaminacionporcromogenerado en lasindustrias del curtido de cueros, Dyna Rev. Fac. Nac. Minas. 160 (2009) 107-119. [10] A.K. Susheela, M. Bhatnagar, K. Vig, N.K. Mondal, Excess fluoride ingestion and thyroid hormone derangements in children living in Delhi, India, Fluoride 38 (2005) 98-108.
[11] Y. Ding, Y. Gao, H. Sun, H. Han, W. Wang, X. Ji, X. Liu, D. Sun, Developmental Fluoride neurotoxicity: A systematic review and meta-analysis, J. Hazard. Mater. 186 (2011) 1942-1946. [12] A.J. Atwood, J.E.D. Davies, D.D. Macnicol, F. Vogtle, Comprehensive Supramolecular Chemistry, Pergamon Press: New York, 1996. [13] P.J. Cragg, Supramolecular Chemistry from Biological Inspiration to Biomedical Applications, Springer, Science + Business Media, 2010. [14] R. Martinez-Manez, F. Sancenon, Fluorogenic and chromogenic chemosensors and reagents for anions, Chem. Rev. 103 (2003) 4419-4476. [15] P.A. Gale, Anion and ion-pair receptor chemistry: highlights from 2000 and 2001, Coord. Chem. Rev. 240 (2003) 191-221. [16] J.W. Steed, Coordination and organometallic compounds as anion receptors and sensors, Chem. Soc. Rev. 38 (2009) 506-519. [17] S. Kubik, Cyclopeptide derived synthetic receptors in: artificial receptors for chemical sensors, Chem. Soc. Rev. 39 (2010) 3648-3663. [18] L.A. Joyce, H.S. Shabbir, E.V. Anslyn, The uses of supramolecular chemistry in synthetic methodology development: Examples of anion and neutral molecular recognition, Chem. Soc. Rev. 39 (2010) 3621-3632. [19] C. Caltagirone, P.A. Gale, 2-Aminoindole based anion receptors, Chem. Soc. Rev. 38 (2009) 520-563. [20] P.A. Gale, S.E. Garcia-Garrido, J. Garric, Anion receptors based on organic frameworks: highlights from 2005 and 2006, Chem. Soc. Rev. 37 (2008) 151-190. [21] M. Vazquez, L. Fabbrizzi, A.Taglietti, R.M. Pedrido, A.M. Gonzalez-Noya, M.R. Bermejo, A colorimetric approach to anion sensing: A selective chemosensor of fluoride
ions, in which color is generated by anion-enhanced π delocalization, Angew. Chem. Int. Ed. 43(2004) 1962-1965. [22] P.A. Gale, R. Quesada, Anion coordination and anion-templated assembly: Highlights from 2002 to 2004, Coord. Chem. Rev. 250 (2006) 3219-3244. [23] T. Gunnlaugsson, M. Glynn, G.M. Tocci, P.E. Kruger, F.M. Pfeffer, Supplementary material (ESI) for organic and biomolecular chemistry, Coord. Chem. Rev. 250 (2006) 30943117. [24] B.A. Moyer, L.H. Delmau, C.J. Fowler, A. Ruas, D.A. Bostick, J.L. Sessler, E. Katayeu, G.D. Pantos, J.M. Llinares, M.A. Hossain, S.O. Kang, K. Bowman-James, Supramolecular chemistry of environmentally relevant anions, Advances in Inorg. Chem. 59 (2006) 175-204. [25] H. Luecke, F.A. Quiocho, High specificity of a phosphate-transport protein determined by hydrogen-bonds, Nature 347 (1990) 402-406. [26] J.J. He, F.A. Quiocho,A nonconservative serine to cysteine mutation in the sulfatebinding protein, a transport receptor, Science 251(1991) 1479-1481. [27] E.V. Anslyn, J. Smith, D.M. Kneeland, K. Ariga, F.Y. Chu, Strategies for phosphodiester complexation and cleavage, Supramol. Chem. 1 (1993) 201-208. [28] J.E. McKee, H.W. Wolf, Water Quality Criteria, Second Ed., California State Water Quality, Control Board: Sacramento, CA., 1993. [29] V.K. Saluja, P.Saluja, G. Hundal, M.S. Hundal, N. Singh, D.O. Jang, Benzthiazolebased multifunctional chemosensor: fluorescent recognition of Fe3+ and chromogenic recognition of HS O 4 − , Tetrahedron 69 (2013) 1606-1610. [30] N.R. Song, J.H. Moon, J. Choi, E.J. Jun, Y. Kim, S-J. Kim, J.Y. Lee, J. Yoon, Cyclic benzobisimidazolium derivative for the selective fluorescent recognition of HSO4− via a combination of C–H hydrogen bonds and charge interactions, Chem. Sci. 4 (2013) 17651771.
[31] P. Kaur, H. Kaur, K. Singh, A ‘turn-off’ emission based chemosensor for HSO4− – formation of a hydrogen-bonded complex, Analyst 138 (2013) 425-428. [32] S.T.Yang, D.J. Liao, S.J. Chen, C.H. Hu, A-T.Wu, A fluorescence enhancement-based sensor for hydrogen sulfate ion, Analyst 137 (2012) 1553-1555. [33] D. Sarkar, A.K. Pramanik, T.K. Mondal, Coumarin based dual switching fluorescent ‘turn-on’ chemosensor for selective detection of Zn
2+
and HSO4−: an experimental and
theoretical study, RSC Adv. 4 (2014) 25341-25347. [34] U. Fegade, S.K. Sahoo, A. Singh, P. Mahulikar, S. Attarde, N. Sing, A. Kuwar, A selective and discriminating noncyclic receptor for HSO4− ion recognition, RSC Adv. 4 (2014) 15288-15292. [35] P.F. Schmidtchen, M. Berger, Artificial organic host molecules for anions, Chem. Rev. 97 (1997) 1609-1645. [36] C.R. Bondy, P.A. Gale, S.J. Loeb, Metal-organic anion receptors: arranging urea hydrogenbond donors to encapsulate sulfate ions, J. Am. Chem. Soc. 126 (2004) 5030-5031. [37] G. Ambrosi, C. Battelli, M. Formica, V.Fusi, L. Giorgi, M.
Micheloni, R.
Pontellini, L. Prodi, Two polyaminophenolic fluorescent chemosensors for H+ and Zn(II). Spectroscopic behaviour of free ligands and of their dinuclearZn(II) complexes, New J. Chem. 33 (20009) 171-180. [38] A.M.L. Nickel, F. Seker, B.P. Ziemert, A.B. Ellis, Imprinted poly(acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence, Chem. Mater. 13 (2001) 1391-1397. [39] R. Martınez-Manez, F. Sancenon, Fluorogenic and chromogenic chemosensors and reagents for anions, Chem. Rev. 103 (2003) 4419-4476.
[40] H.S. Jung, M. Park, D.Y. Han, E. Kim, C. Lee, S.Ham, SJ.S. Kim, Cu2+ ion-induced self-assembly of pyrenylquinoline with a pyrenylexcimer formation, Org. Lett. 11 (2009) 3378-3381. [41] Z.X. Li, L.F. Zhang, W.Y. Zhao, X.Y. Li, Y.K. Guo, M.M. Yu, Fluoranthenenorg based pyridine as fluorescent chemosensor for Fe3+, Inorg, Chem. Comm. 14 (2011) 656-1658. [42] J. Shao, H. Lin, H. Lin, A novel chromo- and fluorogenic dual responding H2PO4− receptor based on an azo derivative, Dyes Pig. 80 (2009) 259-263. [43] P. Vigato, S. Tamburini, L. Bertolo, The development of compartmental macrocyclic Schiff bases and related polyamine derivatives, Coordination Chemistry Reviews 251 (2007) 1311-1492. [44] A. Jiménez-Sánchez, N. Farfán, R. Santillan, Multiresponsive Photo-, Solvato-, Acido-, and Ionochromic Schiff Base Probe, The Journal of Physical Chemistry C, 119 (2015) 1381413826. [45] P.S. Nayab, M. Pulaganti, S.K. Chitta, A New Isoindoline Based Schiff Base Derivative as Cu (II) Chemosensor: Synthesis, Photophysical, DNA Binding and Molecular Docking Studies, Journal of Fluorescence 25 (2015) 1763-1773. [46] P.S. Nayab, M. Pulaganti, S.K. Chitta, M. Abid, R. Uddin, Evaluation of DNA Binding, Radicals Scavenging and Antimicrobial Studies of Newly Synthesized NSubstituted Naphthalimides: Spectroscopic and Molecular Docking Investigations, Journal of Fluorescence, 25 (2015) 1905-1920. [47] R. Arabahmadi, M. Orojloo, S. Amani, Azo Schiff bases as colorimetric and fluorescent sensors for recognition of F−, Cd2+ and Hg2+ ions, Anal. Methods 6 (2014) 7384-7393. [48] R. Arabahmadi, S. Amani, A new fluoride ion colorimetric sensor based on azo– azomethine receptors, Supra. Chem. 26 (2014) 321–328.
[49] R. Arabahmadi, S. Amani, Synthesis and studies of selective chemosensors for anions and cations byazo-containingsalicylaldimine-based receptors, J. Coord. Chem. 66 (2013) 218–226. [50] Z. Shaghaghi, Spectroscopic properties of some new azo–azomethine ligands in the presence of Cu2+, Pb2+, Hg2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 131 (2014) 67-71. [51] A.M. Khedra, M. Gaberb, R.M. Issaa, H. Erten, Synthesis and spectral studies of 5-[3(1, 2,4-triazolyl-azo]-2, 4-dihydroxybenzaldehyde (TA) and its Schiff bases with 1, 3diaminopropane (TAAP) and 1, 6-diaminohexane (TAAH). Their analytical application for spectrophotometric micro-determination of cobalt(II). Application in some radiochemical studies, Dyes Pig. 67 (2005) 117–126. [52] E. Ispir, The synthesis, characterization, electrochemical character, catalytic and antimicrobial activity of novel, azo-containing Schiff bases and their metal complexes, Dyes Pig. 82 (2009) 13–19. [53] W. Likussar, D.F. Boltz,Theory of continuous variations plots and a new method for spectrophotometric determination of extraction and formation constants, Anal. Chem. 43 (1971) 1265-1272. [54] H.A. Benesi, J.H. Hildebrand, A spectrophotometric investigation of the interaction of iodine with aromatic hydrocarbons, J. Am. Chem. Soc. 71 (1949) 2703–2707. [55] J. Nieboer, R. Haiges, W. Hillary, X. Yu, T. Richardet, H.P.A. Mercier, M. Gerken, Fluoride-ion acceptor properties of WSF4: Synthesis, characterization, and computational study of the WSF5– and W2S2F9– anions and
19
F NMR spectroscopic characterization of the
W2OSF9– anion, Inorg. Chem. 51 (2012) 6350–6359.
[56] J. Manojkuma, J. Nagendra-Babu, V. Bhalla, N. Sighathwal,Visible colorimetric sensor for fluoride ion based on o-phenylenediamine, Supra. Chem. 19 (2007) 511-516. [57] J. Xiong, L. Sun, Y. Liao, G.N.
Li, J.L. Zuo, X.Z. You, A new optical and
electrochemical sensor for fluoride ion, Tetrahedron Lett. 52 (2011) 6157-6161.
[58] H.W. Richardson, W.E. Hatfield, On the superexchange mechanism in polymeric, pyrazine-bridged copper(II) complexes, J. Am. Chem. Soc. 98 (1976) 835-839. [59] J. Miller, J.C. Miller,Statistics and Chemometrics for Analytical Chemistry, 6th Ed., Published by: Melih Bayar. 2014. [60] S. Chall, S.S. Mati, S. Konar, D.Singharoy, S. Chandra Bhattacharya, An efficient, Schiff-base derivative for selective fluorescence sensing of Zn2+ ions: Quantum chemical calculation appended by real sample application and cell imaging study, Org. Biomol. Chem. 12 (2014) 6447-6456. [61] S. Park, K. Hong, J. Hong, H. Kim, Azo dye-based latent colorimetric chemodosimeter for the selective detection of cyanides in aqueous buffer, Sens. Actuators, B 174 (2012)140– 144.
Table 1. Absorption spectral data of (L) in various organic solvents; λmax /nm (ε(M-1 cm-1)):
Receptor
L
DMSO 255 (12200) 265 (12300) 400 (23200) 435 (20200)
DMF 255 (22000) 270 (14000) 385 (21600) 440 (14200)
CH3CN
THF
270 (16700) 280 (8700) 365 (23600) 290 (8300) 380 (25000) 375 440 (12600) (20000) 440 (5400)
MeOH 270 (23200) 370 (32700) 385 (36600)
CHCl3
Dioxane
255 (14100) 280 (18800) 375 (38000) 445 (8300)
270 (16000) 365 (34500) 440 (5000)
Table 2. Data obtained from the UV-Vis spectra upon titration of receptor (L) with TBAF and TBAH2PO4 in DMSO.
Receptor, λmax(nm)
Receptor + anion
Complex, λmax(nm)
Bathochromic shift, ∆λmax(nm)
Isosbestic point, (nm)
Ka (M-1)
LOD(M)
L – F¯
400
515
115
460
K1=1.50⤬104 K2=0.2
1.66⤬10-6
L – H2PO4¯
400
505
105
455
K1=8.20⤬103 K2=1.53⤬102
1.24⤬10-6
Table 3. Data obtained from the UV-Vis spectra upon titration of receptor L (4⤬10-5 mol.L-1) with cations in 9:1 DMSO/water
Receptor, λmax (nm)
receptor + cations L –Cr+3 L –Fe+3 L –Cu+2 L –Al+3
Complex, λmax(nm)
460 460 460 460
360 360 365 360
Hypsochromic Isosbestic shift, ∆λmax(nm) point,(nm) -100 -100 -95 -100
380 385 385 380
Ka (M-1) 3.20 ⤬104 4.71 ⤬104 3.40 ⤬ 104 1.86 ⤬104
LOD (M) 2.28⤬10-6 1.99⤬10-6 2.95⤬10-6 3.02⤬10-6
Schemes, Tables and Figures:
HO Cl
N
OH EtOH
N
OH
reflux
Cl C O H
N
H 2N
N
C H
Cl
Cl
Scheme 1. Synthesis of sensor (L)
N
OH
Fig. 1The absorption spectra of (L) in organic solvents with different polarities
Fig. 2 UV–Vis absorption spectra of sensor L (4⤬10-5 mol.L-1 in DMSO) in the presence of 5 equiv. of different anions (5⤬10−4 mol.L-1), from left to right: free (L), H2PO4¯, F¯, Cl¯, Br¯,NO3¯, HSO4¯ (as their TBA salts).
Fig. 3 Absorption spectra changes of L (4⤬10-5 mol.L-1) after addition of increasing amounts of F¯ ions (0-5 equivalent) in DMSO at room temperature. Insets: above; Absorption at selected wavelengths versus the number of equivalents of F¯ added. Down; Job plot of L with F¯ at 515 nm
Fig. 4 Absorption spectra changes of L (4⤬10-5 mol.L-1) after addition of increasing amounts of H2PO4¯ ions (0-5equivalent) in DMSO at room temperature. Insets: Absorption at selected wavelengths versus the number of equivalents of H2PO4¯ added. Job's plot of L with H2PO4¯ at 505 nm
OH HO
P OH
Cl
Cl
N
C H
O OH
O N
O
N
P
OH
F H
OH
H
O
O
N Cl
N
Cl
Scheme 2. Proposed structure of F¯ and H2PO4¯ anions with receptor (L)
Fig. 5 Effect of competitive anions on the interaction between (L) and F¯
C H
F
N
O
Fig. 6 Effect of competitive anions on the interaction between (L) and H2PO4¯
Fig. 7 UV–Vis absorption spectra of sensor L (4 ⤬ 10-5 mol.L-1 in 9:1 DMSO/ water) in the presence of 3 equiv. of different cations, from left to right: free (L), Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Cd2+, Pb2+, Al3+.
Fig. 8 Absorption spectra changes of (L) (4⤬10-5 mol.L-1) after addition of increasing amounts of Al+3 ions (0-3 equivalent) in 9:1 DMSO/water at room temperature. Insets: above; Absorption at selected wavelengths versus the number of equivalents of cation added down; Benesi–Hildebrand plot of receptor (L) with Al+3 ions
Fig. 9 The Job's plot for 2:1 complex of sensor (L) with Al+3
H O O N Cl
Cl
N
C
N
N
Al
C
Cl N
Cl
N
O O
H
Scheme 3. Proposed structure of receptor (L) with Al(III) complex.
Fig. 10 Effect of competitive cations on the interaction between (L) and Al3+ ion
Fig. 111H NMR titration plot of sensor (L) with F¯ in CDCl3
Fig. 12 1H NMR titration plot of sensor L before (a) and after addition of 2 equivalent of TBAF (b) in CDCl3 (expand of aliphatic section)
Fig. 13 Effect of pH on the UV–Vis spectra of receptor (L) (2⤬10-5 mol.L-1) containing TBAF at 515 nm
Graphical Abstract: Receptor (L) proved to be a colorimetric fluoride (F−), di-hydrogen phosphate (H2PO4 − ) and aluminum (III) sensor. This new chromogenic receptor shows a selective coloration for the above ions. The sensor showed a color change upon addition of fluoride or di-hydrogen phosphate or aluminum(III) ions.
Highlights: 1) A new chromogenic receptor was designed for low cost detection of various biologically anions and cations. 2) A sensor for detecting Fluoride (F−), di-hydrogen phosphate (H2PO4−) and aluminum (III) ions. 3) The receptor is highly selective for Fluoride (F−) based on the interaction of F− and OH groups of the receptor (L). 4) Solution of the receptor is colored in DMSO and colorless when an aluminum (III) is added. 5) The binding constant (Ka) and stoichiometry of the host–guest complexes were
determined by the Benesi–Hildebrand (B–H) plot and Job's method.