Structural, spectral, and electrochemical investigations of para-tolyl-substituted oligogermanes

The synthesis of four new oligogermanes containing para-tolyl-substituents has been achieved via the hydrogermolysis reaction, including the digermane Tol(3)GeGePh(3), the trigermanes Tol(3)GeGePh(2)GeTol(3) and Tol(3)GeGeTol(2)GeTol(3), and the tetragermane Tol(3)GeGePh(2)GePh(2)GeTol(3) (Tol = p-CH(3)C(6)H(4)). These four oligogermanes have been structurally characterized and their structures have been compared with those of their per-phenyl-substituted analogs. The digermane Tol3GeGePh3 exhibits an unusually short Ge-Ge bond distance of 2.408(1) angstrom. The four para-tolyl-substituted oligogermanes have also been characterized by UV/visible spectroscopy and cyclic voltammetry. The expected red shift in the absorbance maximum with increasing catenation was observed for this series of compounds. Their cyclic voltammograms each contain n - 1 irreversible oxidation waves (n the number of Ge atoms), which is atypical since oligogermanes generally exhibit only one irreversible oxidation wave regardless of the degree of catenation. (C) 2010 Elsevier B.V. All rights reserved.