Meso-tetrathienylporphyrins: Electrochemical and axial ligation properties

Article abstract of DOI:10.1016/S0009-2614(01)01189-7

5,10,15,20-Tetrakis(2^′- and 3^′-thienyl)porphyrins [H₂T(2^′-Thio)P and H₂T(3^′-Thio)P] and their metal [Zn(II) and Cu(II)] complexes were examined by electrochemical redox and axial ligation properties. A large anodic shift (100-150 mV) in reduction potentials was observed for MT(2^′-Thio)Ps relative to MTPPs or MT(3^′-Thio)Ps. MT(2^′-Thio)Ps exhibited unusual redox behaviour and follows the trend in oxidation; CuT(2^′-Thio)P>H₂T(2 ^′-Thio)P≥ZnT(2^′-Thio)P in contrast to their corresponding MTPPs, H₂TPP>CuTPP>ZnTPP. It is reflected in the enhanced equilibrium constants (60%) for the ligation of nitrogenous bases with ZnT(2^′-Thio)P when compared to ZnTPP. This is interpreted in terms of increased electron deficient nature of the ZnT(2^′-Thio)P in contrast to Zn(3^′-Thio)P or ZnTPP.