Electrochemical and spectral properties of hexacoordinate polypyridyl silicon complexes

Abstract

Various salts of tetracationic tris(2,2′-bipyridine)silicon(IV) and bis(2,2′;6′,2″-terpyridine)silicon(IV) were synthesized by reaction of SiI 4 with the appropriate ligand followed by metathesis reactions. The resulting salts exhibit multiple, chemically reversible one-electron reduction waves that are significantly shifted to less negative reduction potentials than the corresponding ruthenium analogs. The salts also exhibit anion dependent ion pair charge transfer bands throughout the visible spectrum. Weak, low energy emission is observed from Si(bipy) 3Br 4 and Si(terpy) 2Br 4 in the solid state at 77 K when the sample is excited in the ion pair charge transfer band.