Novel water soluble and amphiphilic titanium(IV) phthalocyanines and their electrochemical studies

Synthetic Metals 196 (2014) 48–55

Contents lists available at ScienceDirect

Synthetic Metals journal homepage: www.elsevier.com/locate/synmet

Novel water soluble and amphiphilic titanium(IV) phthalocyanines and their electrochemical studies Zekeriya Bıyıklıo˘glu ∗ Department of Chemistry, Faculty of Science, Karadeniz Technical University, 61080, Trabzon, Turkey

a r t i c l e

i n f o

Article history: Received 13 January 2014 Received in revised form 12 May 2014 Accepted 21 July 2014 Keywords: Phthalocyanine Amphiphilic Titanium Synthesis Electropolymerization Cyclic voltammetry

a b s t r a c t The synthesis of novel titanium phthalocyanines 3a and 5a bearing [2-(2-{2-[3-(dimethylamino) phenoxy]ethoxy}ethoxy)ethoxy] and [2-(2-{2-[3-(diethylamino)phenoxy]ethoxy}ethoxy)ethoxy] substituents was achieved by cyclotetramerization of phthalonitrile derivatives 3 and 5 with Ti(OBu)4 in the presence of DBU in pentanol. Electrochemical studies of the titanium phthalocyanines 3a and 5a was investigated with cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Electrochemical studies reveal that dimethylamino and diethylamino groups on the substituents of the complexes cause electropolymerization of the complexes on the working electrode during the oxidation reactions. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Phthalocyanines show very important properties in modern technology with applications in fields [1,2] including: as solar cell [3], chemical sensors [4,5], dyes and pigments [6], non-linear optics [7,8], liquid crystals [9], gas sensors [10], catalysts [11], semiconductors [12], light emitting diodes [13], optical data storage [14], photodynamic therapy (PDT) [15–18]. For such applications, the solubility of phthalocyanines in organic solvents and water is very important. For this reason, to increase the solubility of phthalocyanines, various substituents such as alkyl, aryloxy, alkoxy, phenoxy, macrocyclic, crown ethers [19–24] are introduced at the periphery of the phthalocyanine ring. Moreover, polyethylene oxide derivatives are amphiphilic functional compound which can increases the solubility of phthalocyanines [25–28]. Metallophthalocyanine complexes are important compounds in electrochemical technologies, such as electrocatalytic [29,30] electrochromic [31] applications. Particularly titanium phthalocyanines are becoming an important class of compounds because of their different oxidation states [32–35]. However the related studies for the electrochemical properties of titanium phthalocyanines are still rare in the literature [36,37]. For these reasons, in this paper we aimed to synthesis, characterization and modify working electrodes with electropolymerization of the phthalocyanines

∗ Tel.: +90 462 377 36 64; fax: +90 462 325 31 96. E-mail address: zekeriya [email protected] http://dx.doi.org/10.1016/j.synthmet.2014.07.013 0379-6779/© 2014 Elsevier B.V. All rights reserved.

bearing electropolymerizable dimethylamino and diethylamino substituents. 2. Experimental The used materials, equipments and the electrochemical measurements were supplied as supplementary information. 2.1. Synthesis 2.1.1. 4-[2-(2-{2-[3(Dimethylamino)phenoxy]ethoxy}ethoxy)ethoxy]phthalonitrile (3) 2-(2-{2-[3-(Dimethylamino)phenoxy]ethoxy}ethoxy)ethanol 1 (2 g, 7.43 mmol), 4-nitrophthalonitrile (1.28 g, 7.43 mmol) and K2 CO3 (3.08 g, 22.29 mmol) in dry DMF (17 ml) were stirred at 60 ◦ C for 4 days under an nitrogen atmosphere. Then, reaction mixture was poured into water. The aqueous phase was extracted with chloroform (3 × 120 ml). The combined extracts were dried over anhydrous MgSO4 and then filtered. Solvent was evaporated and the crude product was purified by column chromatography with basic alumina as column material and CHCl3 as eluent. Yield: 1.49 g (51%). IR (KBr Tablet), /cm−1 : 3082 (Ar H), 2917–2875 (Alif. C H), 2229 (C≡N), 1686, 1598, 1574, 1501, 1449, 1354, 1321, 1293, 1253, 1242, 1168, 1125, 1099, 1065, 999, 966, 876, 827, 753, 733, 687, 620, 523. 1 H-NMR (CDCl3 ), (ı:ppm): 7.57 (d, 1H, Ar H), 7.16–7.02 (m, 3H, Ar H), 6.25–6.14 (m, 3H, Ar H), 4.05 (m, 4H, CH2 O), 3.78 (m, 4H, CH2 O), 3.68 (m, 4H, CH2 O), 2.83 (s,

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55

6H, CH3 ). 13 C-NMR (CDCl3 ), (ı:ppm): 162.18, 159.98, 151.97, 135.47, 129.98, 120.05, 119.80, 117.11, 116.30, 115.83, 106.96, 105.92, 102.07, 99.58, 71.02, 70.91, 70.06, 69.36, 68.90, 67.31, 40.68. Elemental analysis calcd. (%) for C22 H25 N3 O4 : C 66.82, H 6.37, N 10.63%; found: C 66.96, H 6.52, N 10.36. MS (ESI), (m/z): 396 [M + H]+ .

49

precipitate the product. The precipitate was filtered and dried in vacuo. Finally, purification was achieved using column chromatography with basic alumina as column material and CHCl3 as eluent. Yield: 0.125 g (61%). IR (KBr tablet) max /cm−1 : 3077 (Ar-H), 2923-2869 (Aliph. C-H), 1604, 1572, 1497, 1485, 1447, 1398, 1338, 1281, 1235, 1114, 1059, 998, 957, 822, 746, 686. 1 H-NMR. (CDCl3 ), ((:ppm): 7.72 (m, 4H, Ar H), 7.10 (m, 8H, Ar H), 6.33-6.31 (m, 16H, Ar H), 4.23 (m, 16H, CH2 O), 4.03 (m, 16H, CH2 O), 2.87 (s, 24H, CH3 ). 13 C-NMR. (CDCl3 ), ((:ppm): 161.57, 159.85, 151.88, 138.64, 129.80, 129.67, 124.56, 120.32, 120.23, 108.65, 105.90, 105.60, 102.07, 99.88, 71.18, 71.15, 71.07, 71.02, 70.07, 67.27, 40.55. UV–vis (DMF): max , nm (log ε): 331 (4.81), 638 (4.45), 705 (4.98). Elemental analysis calcd. (%) for C88 H100 N12 O17 Ti: C 64.23, H 6.12, N 10.21%; found: C 64.40, H 6.33, N 9.97. MALDI-TOF-MS m/z: 1645 [M]+ .

2.1.2. 4-[2-(2-{2-[3(Diethylamino)phenoxy]ethoxy}ethoxy)ethoxy]phthalonitrile (5) Synthesized similarly to 3 from 4. Yield: 1.5 g (53%). IR (KBr tablet), /cm−1 : 3082 (Ar H), 2969–2873 (Alif. C H), 2230 (C≡N), 1610, 1570, 1501, 1452, 1395, 1375, 1356, 1322, 1291, 1255, 1217, 1177, 1142, 1098, 1026, 968, 880, 835, 755, 688, 524. 1 H-NMR (CDCl3 ), (ı:ppm): 7.55 (d, 1H, Ar H), 7.17–6.98 (m, 3H, Ar H), 6.19–6.08 (m, 3H, Ar H), 4.05 (m, 4H, CH2 O), 3.75–3.64 (m, 8H, CH2 O), 3.22 (m, 4H, CH2 N), 1.05 (m, 6H, CH3 ). 13 C-NMR (CDCl3 ), (ı:ppm): 162.16, 160.24, 149.16, 135.47, 130.14, 120.06, 119.81, 117.02, 116.21, 115.76, 106.94, 105.24, 100.82, 98.80, 70.98, 70.85, 70.03, 69.33, 68.89, 67.22, 44.52, 12.88. Elemental analysis calcd. (%) for C24 H29 N3 O4 : C 68.06, H 6.90, N 9.92%; found: C 68.18, H 7.08, N 9.75. MS (ESI), (m/z): 424 [M + H]+ .

2.1.4. Titanium(IV) phthalocyanine (5a) Synthesized similarly to 3a from 5. Yield: 0.103 g (50%). IR (KBr tablet) (max /cm−1 : 3072 (Ar H), 2964–2869 (Aliph. C H), 1606, 1570, 1497, 1449, 1394, 1374, 1340, 1280, 1215, 1117, 1067, 1023, 960, 821, 748, 687. 1 H-NMR. (CDCl3 ), ((:ppm): 7.77 (m, 4H, Ar H), 7.10–7.08 (m, 8H, Ar H), 6.29–6.26 (m, 16H, Ar H), 4.27–4.22 (m, 24H, CH2 O), 4.03–4.00 (m, 24H, CH2 O), 3.29 (m, 16H, CH2 N), 1.12 (m, 24H, CH3 ). 13 C-NMR. (CDCl3 ), ((:ppm): 161.73, 160.14, 149.17, 138.95, 129.93, 129.84, 120.89, 120.55, 120.50, 108.69, 108.65, 105.25, 100.72, 99.09, 71.18, 71.04, 70.99, 70.08, 69.96, 67.20, 44.34, 12.62. UV–vis (DMF): max , nm (log ε): 322 (4.89), 637 (4.44), 705 (5.00). Elemental analysis calcd. (%) for

2.1.3. Titanium(IV) phthalocyanine (3a) A mixture of 4-[2-(2-{2-[3-(dimethylamino)phenoxy]ethoxy} ethoxy)ethoxy]phtha-lonitrile 3 (0.2 g, 0.5 mmol), Ti(OBu)4 (0.2 ml, 0.5 mmol), 5 drops of 1.8-diazabicyclo[5.4.0]undec-7-ene (DBU) in n-pentanol (2 ml) was refluxed with stirring for 12 h under N2 . After cooling to room temperature, 50 ml diethyl ether was added to

CN N

O

O O

OH

O2 N

1

CN

2

i CN

N

O

O O

O

CN

3

ii

RO

OR N N

O

N

Ti

N

N N

N N

3a

RO

R=

O

O

OR

O

N

Fig. 1. The synthesis of titanium phthalocyanine 3a. (i) K2 CO3 , N2 , DMF. (ii) n-pentanol, DBU, 160 ◦ C, titanium(IV)butoxide.

50

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55 CN N

O

O O

OH

O 2N

CN

2 i

4

CN

N

O

O O

O

CN

5

ii

RO

OR N N

O

N

Ti

N

N N

N N

5a

RO

R=

OR

O

O

O

N

Fig. 2. The synthesis of titanium phthalocyanine 5a. (i) K2 CO3 , N2 , DMF. (ii) n-pentanol, DBU, 160 ◦ C, titanium(IV)butoxide.

RO

+4

R'O

OR

OR'

N N N

N

O N

Ti

N

iii

N

N

O

O

O

O

N

R'=

O

O

O

N

3b

R'= O

OR'

R'O

3a

R=

4I

N OR

RO

O

N N

N

N

R=

N

Ti

N

N

O

N

O

O

5a Fig. 3. The synthesis of water soluble titanium phthalocyanines 3b and 5b. (iii) CHCl3 , CH3

O

N

5b I, room temperature.

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55

51

Fig. 4. MALDI-TOF mass spectrum of complex 3a.

Table 1 Voltammetric data of the complexes. All voltammetric data were given versus SCE. Complex TiOPc 3a

Polymerization waves a

E1/2 Ep (mV) a E1/2 b Ep (mV)

b

TiOPc 5a a b c d e f

– – – –

d

Reductions e

1.02 (0.62)

1.03d (0.66)e

−0.58 150 −0.57 90

−0.76c – −0.93 100

−0.94 160 −1.49c 110

−1.13f – – –

E1/2 values ((Epa + Epc )/2) were given versus SCE at 0.100 V s−1 scan rate. Ep = Epa − Epc . This process is assigned to TiIV OPc/TiIII OPc. Epa of first CV cycle. Epc of first CV cycle. This process is assigned to TiIII OPc/TiII OPc.

C96 H116 N12 O17 Ti: C 65.59, H 6.65, N 9.56%; found: C 65.82, H 6.88, N 9.23. MALDI-TOF-MS m/z: 1757 [M]+ . 2.1.5. Quaternized water soluble titanium(IV) phthalocyanine (3b) Titanium(IV) phthalocyanine 5 (0.05 g, 0.03 mmol) was dissolved in 3.5 ml of CHCl3 and 3 ml iodomethane was added to this solution. This reaction mixture was stirred at room temperature for 4 days. The precipitate was filtered off, washed with chloroform, acetone and diethyl ether. Then, watersoluble ionic titanium(IV) phthalocyanine was dried in vacuo. Yield: 0.049 g (75%). IR (KBr tablet) (max /cm−1 : 3010 (Ar H), 2923–2870 (Aliph. C H), 1605, 1487, 1452, 1399, 1338, 1279, 1237, 1114, 1057, 956, 876, 828, 743, 685. UV–vis (DMF): max , nm (log ε): 330 (4.80), 638 (4.45), 705 (4.98). Elemental analysis calcd. (%) for C92 H112 N12 O17 TiI4 : C 49.92, H 5.10, N 7.59%; found: C 50.20, H 4.90, N 7.88. MALDI-TOF-MS m/z: 428 [M − 4I + 2]+4 . 2.1.6. Quaternized water soluble titanium(IV) phthalocyanine (5b) Synthesized similarly to 3b from 5. Yield: 0.05 g (77%). IR (KBr tablet) vmax /cm−1 : 3014 (Ar H), 2925–2867 (Aliph. C H), 1605, 1487, 1450, 1395, 1338, 1240, 1112, 1056, 956, 870, 825, 746, 690.

UV–vis (DMF): max , nm (log ε): 332 (5.08), 634 (4.41), 703 (4.98). Elemental analysis calcd. (%) for C100 H128 N12 O17 TiI4 : C 51.64, H 5.55, N 7.23%; found: C 51.90, H 5.27, N 7.56. MALDI-TOF-MS m/z: 456 [M − 4I + 2]+4 .

Fig. 5. UV–vis spectra of 3a, 3b, 5a and 5b in DMF.

52

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55

3. Results and discussion 3.1. Synthesis and characterization The synthesis of the titanium phthalocyanines are shown in Figs. 1–3. The synthetic procedure of the phthalonitrile derivatives 3 and 5 were carried out by using the procedure previously described [38,39]. Peripherally tetra-substituted titanium phthalocyanines 3a and 5a were synthesized by template cyclotetramerization of 3 and 5 with titanium(IV)butoxide and a base DBU at 160 ◦ C in n-pentanol. Water soluble titanium phthalocyanines 3b and 5b were synthesized from the reaction of corresponding titanium phthalocyanines 3a and 5a with the excess of methyl iodide in CHCl3 at room temperature for 4 days in the dark. In the IR spectrum of 3 and 5, the broad peak for the O H bands for compounds 1 and 4 disappeared and the characteristic vibrations of the C≡N peak appeared at 2229 and 2230 cm−1 , respectively. In 1 H NMR spectrum of 3 and 5, the disappearance of the OH peaks of 1 and 4, besides presence of additional aromatic protons indicated that nucleophilic aromatic nitro displacement was achieved. In the 13 C NMR spectrum of 3 and 5 indicated the presence of nitrile carbon atoms in 3 and 5 at (116.30, 115.83 ppm) for 3, (116.21, 115.76 ppm) for 5. The molecular ion peaks of 3 and 5 were found at m/z 396 [M + H]+ , 424 [M + H]+ , respectively. The IR spectra of titanium phthalocyanines 3a and 5a are very similar to each other. The sharp C≡N vibrations at 2229, 2230 cm−1 disappeared after formation of the titanium phthalocyanines 3a and 5a, respectively. No major changes in the IR spectra for 3b and 5b were observed after quaternization. The 1 H NMR spectrum of complexes 3a and 5a were consistent with tproposed structures.

Fig. 6. (a) CVs of TiOPc 3a. (b) SWV of TiOPc 3a.

The 13 C NMR spectrum of titanium phthalocyanines 3a and 5a showed typical chemical shifts for aliphatic protons between 71.18 and 40.55 ppm for 3a, 71.18–12.62 ppm for 5a aromatic protons between 161.57 and 99.88 ppm for 3a, 161.73–99.09 ppm for 5a. The structure of non-ionic and cationic titanium phthalocyanines 3a, 5a, 3b, 5b were confirmed using by MALDI-TOF mass spectrometry where molecular ion peaks at m/z = 1645 [M]+ (Fig. 4), 1757 [M]+ , 428 [M − 4I + 2]+4 and 456 [M − 4I + 2]+4 , respectively. The UV–vis spectra of titanium phthalocyanines and their cationic derivatives 3a, 5a, 3b, 5b in DMF at room temperature is shown in Fig. 5. The ground-state electronic absorption spectra of 3a, 5a, 3b, 5b in DMF show the Q band absorbtions at 705 nm for 3a, 5a, 3b 703 nm for 5b. The B bands of the titanium phthalocyanines appear in the UV region, at around 322–332 nm in DMF. 3.2. Electrochemical studies In order to define of electrochemistry of amphiphilic titanium phthalocyanines cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used. The reduction and oxidation potentials of amphiphilic titanium phthalocyanines are given in Table 1. Redox active metal center such as titanium increases the redox richness of the complex with extra electron transfer processes of the metal centers. Fig. 6 shows the CV and SWV responses of 3a recorded in DCM-TBAP electrolyte system on a Pt working electrode. TiOPc 3a shows different electrochemical behavior from TiOPc 5a. The cyclic voltammogram of Fig. 6a involves four reduction reactions. While two reduction reactions (R1 and R3 ) have expected peak currents, R2 and R4 reduction couples have small peak currents. These different peak currents may arise owing to the different number of transferred electrons and/or different rates of the electron transfer

Fig. 7. (a) CVs of TiOPc 5a. (b) SWV of TiOPc 5a.

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55

53

Fig. 9. The plot of square root of scan rate versus peak current for TiOPc 5a.

Fig. 8. (a) CV of complex 3a at various scan rates (ranging from 25 to 1000 mV s−1 ) on a Pt working electrode in DCM/TBAP. (b) CV of complex 5a at various scan rates (ranging from 25 to 1000 mV s−1 ) on a Pt working electrode in DCM/TBAP.

reactions. TiOPC complexes give metal based reduction reactions in addition to the phthalocyanine based processes [40,41]. These reduction processes labeled as R1 at −0.58 V, R2 at −0.76 V, R3 at −0.94 V and R4 at −1.13 V for complex 3a. SWV of the complex 3a illustrate these analyses results more clearly as shown in Fig. 6b. Fig. 7 shows the CV and SWV responses of TiOPc 5a in DCM/TBAP electrolyte system. The cyclic voltamogram of TiOPc 5a gives three one-electron reduction processes (Fig. 7a). It displays three reversible reduction reactions labeled as R1 (E1/2 = −0.57 V; Ep = 90 mV), R2 (E1/2 = −0.93 V; Ep = 100 mV) and

Fig. 10. Electropolymerized working electrode.

54

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55

intensity until the 15 cycle. These voltammetric behavior indicates electropolymerization of the complex 3a on the working electrode. As shown in Fig. 12 electropolymerized wave increases up to 3 CV cycle with a potential shift. After 3 CV cycles waves starts to decrease to 15. cycle with potential shift, exhibiting electropolymerization of the TiOPC 5a on the working electrode. Electropolymerization on the working electrode were seen clearly with naked eyes, which support the electropolymerization processes. 4. Conclusion

Fig. 11. Repetitive CVs of TiOPc 3a recorded at anodic potential windows of DCM/TBAP electrolyte system at 0.100 V s−1 scan rate on a Pt working electrode.

In this study, amphiphilic and water soluble titanium(IV) phthalocyanines bearing electropolymerizable dimethylamino and diethylamino susbtituents were synthesized and their electrochemical properties were studied. Presence of dimethylamino and diethylamino groups on the peripheral positions of the titanium phthalocyanines supply electropolymerization of the complex on the working electrode which provide an excellent way for the modification of the electrodes with titanium phthalocyanines. Also, for preparation of composite electrode, electropolymerization is a desired property. Acknowledgement This study was supported by The Scientific & Technological Research Council of Turkey (TÜBI˙ TAK, project no: 111T963). References

Fig. 12. Repetitive CVs of TiOPc 5a recorded at anodic potential windows of DCM/TBAP electrolyte system at 0.100 V s−1 scan rate on a Pt working electrode.

R3 (E1/2 = −1.49 V; Ep = 110 mV). All electron transfer processes are both electrochemically and chemically reversible with respect to Ep values. On the other hand, SVWs of the TiOPc 5a clearly support these reversible characters of the processes, since these couples show symmetric cathodic peaks with the same peak currents (Fig. 7b). Also, the peak currents increased linearly with the square root of the scan rates for scan rates ranging from 25 to 1000 mV s−1 for these complexes 3a and 5a (Fig. 8a and b), respectively. This linearity was confirmed by the graphic of square root of scan rate versus peak current (Fig. 9 for TiOPc 5a). While TiOPc complexes 3a and 5a gave common reduction reactions during cathodic potential scans, they were electropolymerized on the working electrode (Fig. 10 for complex 3a) during the anodic potential scans. Electropolymerization processes are very important for the usage of the TiOPc complexes in different areas. Fig. 11 illustrates the repetitive CV scans with in the anodic potential windows of DCM/TBAP for complex 3a. During the first anodic CV cycle, anodic redox couple was recorded at 1.02 V and its cathodic couple was recorded at 0.62 V. During the second, third and fourth CV cycles, the anodic wave increases with a potential shift at 1.25 V. After this point, it decreases in current

[1] C.C. Leznoff, A.B.P. Lever, in: C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: Properties and Applications, 1–4, VCH Publishers, New York, NY, 1989–1996. [2] A. Erdogmus, M. Durmus, A.L. Ugur, O. Avciata, U. Avciata, T. Nyokong, Synth. Met. 160 (2010) 1868–1876. [3] Y. Yang, S.R. Forrest, Am. Chem. Soc. Nano 2 (2008) 1022–1032. [4] V. Parra, M. Bouvet, J. Brunet, M.L. Rodríguez-Méndez, J.A. Saja, Thin Solid Films 516 (2008) 9012–9019. [5] M. Bouvet, Anal. Bioanal. Chem. 384 (2006) 366–373. [6] D. Wöhrle, G. Schnurpfeil, S.G. Makarov, A. Kazarin, O.N. Suvorova, Macroheterocyc 5 (2012) 191–202. [7] A. Grund, A. Kaltbeitzel, A. Mathy, R. Schwarz, C. Bubeck, P. Vernmehren, M. Hanack, J. Phys. Chem. 96 (1992) 7450–7454. [8] D. Dini, M. Hanack, J. Porphyrins Phthalocyanines 8 (2004) 915–933. [9] F. Al-Hazmi, A.A. Al-Ghamdi, N. Al-Senany, F. Alnowaiser, F. Yakuphanoglu, Comp., B: Eng. 56 (2014) 15–19. [10] G. Guillaud, J. Simon, J.P. Germain, Coord. Chem. Rev. 180 (1998) 1433–1484. [11] N. Nombona, P. Tau, N. Sehlotho, T. Nyokong, Electrochim. Acta 53 (2008) 3139–3148. [12] D. Li, H. Wang, J. Kan, W. Lu, Y. Chen, J. Jiang, Org. Elect. Phy. Mat. Appl. 14 (2013) 2582–2589. [13] G. De la Torre, C.G. Claessens, T. Torres, Chem. Commun. 20 (2007) 2000–2015. [14] M. Moussavi, A. Cian, J. Fischer, R. Weiss, Inorg. Chem. 27 (1988) 1287–1291. [15] H. Ali, J.E. van Lier, Chem. Rev. 99 (1999) 2379–2450. [16] A.C. Tedesco, J.C.G. Rotta, C.N. Lunardi, Curr. Org. Chem. 7 (2003) 187–196. [17] S. Makhseed, M. McHacek, W. Alfadly, A. Tuhl, M. Vinodh, T. Simunek, V. Novakova, P. Kubat, E. Rudolf, P. Zimcik, Chem. Commun. 49 (2013) 11149–11151. [18] A. Moussaron, P. Arnoux, R. Vanderesse, E. Sibille, P. Chaimbault, C. Frochot, Tetrahedron 69 (2013) 10116–10122. [19] Z. Biyiklioglu, S.Z. Yıldız, H. Kantekin, J. Organomet. Chem. 695 (2010) 1729–1733. [20] Z. Biyiklioglu, H. Kantekin, Polyhedron 27 (2008) 1650–1654. [21] H. Kantekin, Z. Biyiklioglu, E. C¸elenk, Inorg. Chem. Commun. 11 (2008) 633–635. [22] S.W. Oliver, T.D. Smith, Heterocyclic 22 (1984) 2047–2052. [23] E. Hamuryudan, Z.A. Bayır, Ö. Bekaro˘glu, Dyes Pigm. 43 (1999) 77–81. [24] H.R.P. Karao˘glu, A. Gül, M.B. Koc¸ak, Dyes Pigm. 76 (2008) 231–235. [25] I. Gürol, V. Ahsen, J. Porphyrins Phthalocyanines 4 (2000) 620–625. [26] Z. Biyiklioglu, Synth. Met. 162 (2012) 26–34. [27] I˙ . Acar, Z. Biyiklioglu, M. Durmus¸, H. Kantekin, J. Organomet. Chem. 708–709 (2012) 65–74. [28] Z. Biyiklioglu, D. C¸akır, Spectrochim. Acta Mol. Biomol. Spect. 98 (2012) 178–182. [29] I. Balan, I.G. David, V. David, A.I. Stoica, C. Mihailciuc, I. Stamatin, A.A. Ciucu, J. Electroanal. Chem. 654 (2011) 8–12. [30] A. Koca, A. Kalkan, Z.A. Bayır, Electrochim. Acta 56 (2011) 5513–5525.

Z. Bıyıklıo˘glu / Synthetic Metals 196 (2014) 48–55 [31] [32] [33] [34] [35]

C.L. Lin, C.C. Lee, H. Ho, J. Electroanal. Chem. 524 (2002) 81–89. S.E. Maree, J. Porphyrins Phthalocyanines 9 (2005) 880–883. G. Mbambisa, P. Tau, E. Antunes, T. Nyokong, Polyhedron 26 (2007) 5355–5364. P. Tau, T. Nyokong, Dalton Trans. 32 (2006) 4482–4490. Y. Arslano˘glu, A.M. Sevim, E. Hamuryudan, A. Gül, Dyes Pigm. 68 (2006) 129–132. [36] F. Demir, A. Erdogmus, A. Koca, J. Electroanal. Chem. 703 (2013) 117–125.

[37] [38] [39] [40] [41]

55

W.F. Law, K.M. Lui, D.K.P. Ng, J. Mater. Chem. 7 (1997) 2063–2067. Z. Biyiklioglu, H. Kantekin, I. Acar, Inorg. Chem. Commun. 11 (2008) 1448–1451. Z. Biyiklioglu, H. Kantekin, Transition Met. Chem. 32 (2007) 851–856. P. Tau, T. Nyokong, Electrochim. Acta 52 (2007) 3641–3650. A. Erdogmus, A. Koca, A.L. Ugur, I. Erden, Synth. Met. 161 (2011) 1319–1329.