Regioisomers of magnesium(II) phthalocyanine bearing menthol substituents - Synthesis, spectral, electrochemical and computational studies

Abstract

Three regioisomers of L-menthol-substituted magnesium(II) phthalocyanine were obtained and characterized. Nuclear magnetic resonance studies were used to unambiguously assign the regioisomers to be with C1, C2 and C4 symmetry, while D2 regioisomer was not isolated. Additionally, the crystal structure of the C1 isomer was determined. Maxima of the Q-band were observed in the range of 703–710 nm, quantum yields of fluorescence varied from 0.11 to 0.25, while quantum yields of singlet oxygen generation varied from 0.20 to 0.37. The phthalocyanine derivatives displayed, in the voltammetric study, two one-electron oxidations and two one-electron reductions, which were assigned to ring based one electron processes. DFT methods (B3LYP/6-31G) were used to calculate IR and UV–Vis spectra and optical band gap.