Synthesis, Photochemistry, and Electrochemistry of (P)Ge(R)2 and (P)Ge(R)X (P = TPP or OEP, R = CH3, CH2C6H5, or C6H5, and X = Cl-, OH-, or ClO4-)

Article abstract of DOI:10.1021/ja00259a019

The synthesis and characterization of (P)Ge(R)2 and (P)Ge(R)X, where P is the dianion of octaethylporphyrin (OEP) or the dianion of tetraphenylporphyrin (TPP), R is CH3, CH2C6H5, or C6H5, and X is ClO4^-, Cl^-, or OH^-, is described.Each complex was characterized by 1H NMR, IR, and UV-visible spectroscopy and electrochemistry.The investigated (P)Ge(R)2 complexes can be reduced and oxidized by up to two electrons.The reductions are reversible but a rapid cleavage of the germanium-carbon bond follows the initial electrooxidation.The final oxidation product after the abstraction of one electron from (P)Ge(R)2 was identified as (P)Ge(R)X, where X = ClO4^-, Cl^-, or OH^- depending on the solvent/supporting electrolyte system. (P)Ge(R)Cl could also be generated from (P)Ge(R)2 in solutions of degassed CHCl3 by illumination with visible light.Electrochemical oxidation of (OEP)Ge(C6H5)2, (OEP)Ge(C6H5)OH, and (OEP)Ge(C6H5)Cl gives the same final species which was spectroscopically and electrochemically identified as (OEP)Ge(C6H5)ClO4.Interestingly, (OEP)Ge(C6H5)ClO4 could be converted to (OEP)Ge(C6H5)OH by a one-electron electroreduction which was followed by reaction of the generated anion radical with trace H2O in solution.Finally, an overall scheme for the oxidation and reduction of (P)Ge(R)2 and (P)Ge(R)X porphyrins is presented.