ELECTROCHEMISTRY AND SPECTROSCOPY OF MAGNESIUM OCTAETHYLTETRAAZAPORPHYRIN AND MAGNESIUM OCTAKIS(METHYLTHIO)TETRAAZAPORPHYRIN

摘要

Electrochemical properties, absorption and magnetic circular dichroism (MCD) spectra are reported for two peripherally substituted tetraazaporphyrins (TAP). Data are described for magnesium octaethyltetraazaporphyrin (MgOETAP) and magnesium oc-takis(methylthio)tetraazaporphyrin (MgOMTTAP) in dichloromethane (DCM) and N,N-dimethylformamide (DMF) solutions. Differential pulse Voltammograms (DPV) and cyclic voltammograms (CV) measurements yielded epsilon(1/2) values of: +0.81 V forming the ring oxidized pi cation [MgOETAP(-1)](+), -0.70 V forming the ring reduced pi anion [MgOETAP(-3)](-) and -1.15 V forming the ring reduced pi dianion [MgOETAP(-4)](2-)) and E(1/2) values of 0.95 V forming the oxidized pi cation [MgOMTTAP(-1)](+), -0.68 V forming the ring reduced pi dianion [MgOMTTAP(-4)](2-) and -1.05 V forming the ring reduced pi dianion [MgOMTTAP(-4)](2-). Band deconvolution calculations, that couple the absorption and the MCD spectra, are reported for both compounds. The energies of the fitted bands are compared with experimental results for magnesium phthalocyanine reported by Ough et al. [E.A. Ough, T.N. Nyokong, K.A.M. Creber and M.J. Stillman, Inorg. Chem., 27 (1988) 2725]. Deconvolution analysis isolated an additional degenerate transition in the Q band region (700-500 nm), which has been assigned as a vibrational component of the Q band. Individual electronic transitions (assignments) are located at: 595 (Q(00)), 570 (Q(01)), 342 (B1), and 327 nm (B2) for MgOETAP and at: 663 (Q(00)), 611 (Q(02)), 374 (B1), 352 (B2), and 250 nm (L) for MgOMTTAP. [References: 45]