H-type aggregation of functional metal ion sensing phthalocyanines: Synthesis, characterization and electrochemistry

By Bilgiçli, Ahmet T.; Yaraşir, M.N.; Kandaz, Mehmet & Rıza Özkaya, A.
Published in Polyhedron NULL 2010

Abstract

We report, in this study, the preparation and physical characterization of the peripherally functionalized ionophore ligand, 4,5-bis(6-hydroxyhexan-3ylthio)-1,2-dicyanobenzene (1) and its branched thioalcohol-substituted phthalocyanines, 2,3,7,8,12,13,17,18-octakis 6-hydroxyhexan-3-ylthio)-metal (II) or (III) phthalocyanines M Pc[SCH(C3H7)(C2H5OH)]8 M = Pb(II) (2), Zn(II) (3), Cu(II) (4), Co(II) (5) and Mn(III), X = Cl- (6) which can selectively bind soft-metal ions such as silver (I) and palladium (II). It was observed by means of UV–Vis absorption spectrophotometry that the aggregates formed lead to a low solubility of the phthalocyanines in protic solvents, such as low molecular alcohols. However, the addition of AgNO3 and Na2PdCl4 into a THF–MeOH solution of M Pc[SCH(C3H7)(C2H5OH)]8X M = Pb(II) (2), Zn(II) (3), Cu(II) (4), Co(II) (5) and Mn(III), X = Cl- (6) induced optical changes, which indicated the formation of twisted H-type dimers (blue shift, face-to-face fashion) of M Pc[SCH(C3H7)(C2H5OH)]8 complexes, bound by four PdCl2 and AgNO3 units in THF solution. Elemental analysis data, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS), FT-IR, 1H, 13C NMR, and UV–Vis spectral data were used as complementary techniques. Voltammetry and in situ spectroelectrochemistry of the complexes were performed on Pt in DMSO/TBAP. The first reduction and oxidation processes of 5 were found to be split due to the presence of facile equilibria between the species coordinated differently at axial positions. The Mn(III)Pc(-2)X- complex (6) displayed well-defined colour changes during its reduction processes. The redox behaviour of the Mn(III)Pc(-2)X- complex was observed to be affected significantly by the existence of oxygen in solution due to the formation of μ-oxo MnPc species, Mn(III)Pc–O–PcMn(III). This effect was clarified well by in situ spectroelectrochemical measurements.

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