Self-assembling novel phthalocyanines containing a rigid benzothiazole skeleton with a 1,4-benzene linker: Synthesis, spectroscopic and spectral properties, and photochemical/photophysical affinity

Abstract

A novel benzothiazole containing phthalonitrile derivative and its peripherally tetra substituted metal free (4), Ni(II) (5), Zn(II) (6), Cu(II) (7) and Ti(IV) (8) phthalocyanines have been synthesized. The novel compounds were characterized by elemental analysis, IR, UV–Vis, 1H NMR, 13C NMR and mass spectroscopy. Zn(II)Pc (6) showed monomeric behavior in THF up to 7×10−5moldm−3 concentration and in various solvents (pyridine, dichloromethane, DMF and DMSO) up to 4×10−5moldm−3 concentration. On the other hand, Cu(II)Pc (7) formed aggregates in THF at concentrations higher than 3.6×10−5moldm−3 and showed monomeric behavior in THF, DMF and DMSO at 2.4×10−5moldm−3. Furthermore, the photochemical and photophysical properties of the metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines were investigated in THF. All the investigated phthalocyanines showed similar fluorescence behavior in THF. The synthesized Ni(II) (5) and Cu(II) (7) phthalocyanines were not evaluated for this purpose because of the paramagnetic behavior of the central metals in the cavity of these complexes. Singlet oxygen generation properties of these phthalocyanine compounds were also investigated and the order of singlet oxygen quantum yields were found as: Zn(II) Pc (6)>Ti(IV) Pc (8)>unsubstituted Zn(II) Pc (ZnPc)>metal free Pc (4). The degradation of the studied compounds was studied under light irradiation and the oxotitanium (IV) phthalocyanine derivative was found to be very sensitive to light irradiation. The fluorescence quenching behavior of the studied novel peripherally tetra 4-(1,3-benzothiazol-2-yl)phenoxy substituted metal free (4), Zn(II) (6) and Ti(IV) (8) phthalocyanines by the addition of 1,4-benzoquinone was also studied.