Wydział Chemii

Jerzy Lisowski

Maria Grzeszczuk

Lechosław Latos-Grażyński

1989

Inorganica Chimica Acta

161

153-163

10.1016/S0020-1693(00)83086-8

Naukowa

Angielski

Artykuł

Electrochemistry, NMR, ESR and UV-Vis spectroscopy of 21-thiatetra(p-tolyl)porphyrin (STpTPH) and respective copper(II) (21-tiatetra(p-tolyl)porphyrin) X Cu(STpTP)X (X=Cl⁻, Br⁻, HCO₃⁻, ClO₄⁻, PPh₃) complexes have been investigated.Monothiaporphyrin is an analogue of widely studied tetraphenylporphyrin, where one of the pyrrole rings has been replaced by a thiophene moiety. The impact of the replacement and the coordinating abilities of thiophene sulfur have been studied. STpTPH undergoes a two step proton addition in dichloromethane. Mono- and dication formations result in distorting the planar thiaporphyrin structure as confirmed by NMR and UV-Vis data. The electronic spectra of Cu(STpTP)X have a similar pattern to the monocation form but the pronounced dependence of the band positions on the ligand character has been established. An ESR spectrum pattern is typical for quasi-tetragonal Cu(II)systems. Parallel features show well resolved seven lines associated with coordination of three nearly equivalent nitrogens. The ESR parameters, particularly hyperfine coupling constant A, have been correlated with the geometry of Cu(II) porphyrins or porphyrin- like ligands. The influence of the axial ligand on the ESR parameters has also been discussed. Cyclic voltammetry studies show that Cu(STpTP)X exhibits a well defined Cu(II)/Cu(I) reduction (E_1/2= −0.14 ±0.03 V depending on the axial ligand), reported previously only for Cu(II) N-substituted porphyrins but not for Cu(II) porphyrins. The second reduction step results in demetalation. The physicochemcial properties of Cu(STpTP)X are considerably different from Cu(TTP) and closely resemble those of Cu(II) N-substituted porphyrin. Comparison between the electrochemical and spectroscopical properties has been discussed in terms of the general stability of a Cu(II)-axial ligand bond.

https://doi.org/10.1016/S0020-1693(00)83086-8

http://www.elsevier.com