Effect of axially bound anions on the electroreduction of tin(IV) porphyrins in tetrahydrofuran

Abstract

The spectroscopic characterization and electrochemistry of SnL(X)₂ is presented where L is the dianion of tetra-p-tolylporphyrin or tetra-m-tolylporphyrin and X is ClO₄^–, Br^–, Cl^–, F^–, or OH^–. In all cases, electroreduction leads to porphyrin π anion radicals and dianions which were characterized in tetrahydrofuran by spectroelectrochemistry and e.s.r. spectroscopy. Dissociation of one ClO₄^– ion from SnL(ClO₄)₂ occurs before electroreduction of the complex but no dissociation is observed either before or after electroreduction of SnL(F)₂ or SnL(OH)₂. In contrast, one Br^– ion dissociates after the first electron addition to SnL(Br)₂ while one Cl^– ion dissociates from SnL(Cl)₂ after the second electroreduction of this complex.