ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL INVESTIGATIONS OF [(TPTP)M(V)L(2)]CL-) WHERE TPTP IS THE DIANION OF TETRA-P-TOLYLPORPHYRIN, M=P OR SB, AND L=CL- OR OCH3-(()

The electrochemical and spectroelectrochemical properties of [(TpTP)M( V)(L)(2)]Cl-+(-) in dichloromethane are presented where M = P or Sb, L = OCH3- or Cl-, and TpTP is the dianion of tetra-p-tolylporphyrin. Al l four porphyrins undergo two one-electron reductions on the cyclic vo ltammetry time scale to give initially porphyrin rr anion radicals and dianions. The singly and doubly reduced products of [(TpTP)MV(OCH3)(2 )]Cl-+(-) are relatively stable, but this is not the case for the two [(TpTP)M(V)Cl(2)]Cl-+(-) complexes, both of which undergo a series of chemical reactions following electron transfer. The coupled electroche mical/chemical reactions lead to a low-valent M(III) complex in the ca se of the bis(chloro) Sb(V) derivative and to numerous decomposition p roducts, including the free base porphyrin, in the case of the bis(chl oro) P(V) porphyrin. UV-visible spectroelectrochemical and EPR data su ggest that the four investigated porphyrins all undergo an internal ch arge transfer from the electrogenerated porphyrine anion radical to th e Sb(V) or P(V) porphyrin center. The EPR spectrum of singly reduced [ (TpTP)(SbCl2)-Cl-V]Cl-+(-) at 123 K in CH2Cl2 has a signal centered at g = 2.018 and exhibits hyperfine splitting due to interaction between the metal and the unpaired electron on the porphyrin macrocycle. The three other singly reduced porphyrins display a specturm with broad is otropic signals centered at g similar to 2.00 and a spectral line widt h which increases with temperature, also supporting an internal charge transfer mechanism.