Outer-sphere charge transfer in ion pairs with hydridic, carbanionic, sulfidic and peroxidic anions as electron donors―spectroscopy and photochemistry

摘要

Ionic transition metal complexes are well known to participate in optical outer-sphere charge transfer (OSCT) of ion pairs which consist of oxidizing cations and reducing anions. Frequently, simple anions such as iodide or oxalate have been used as electron donors. Unfortunately, many important anions such as H~-, C_6H_5~-, S~(2-) and O_2~(2-) are not suitable owing to their strong nucleophilicity. However, this nucleophilicity can be attenuated if these anions are replaced by appropriate derivatives including BH_3CN~- as hydridic, B(C_6H_5)_4~- as carbanionic, PO_3S~(3-) as sulfidic and BO_3~- as peroxidic donors. A variety of ion pairs which contain such anions and cationic transition metal complexes or organic cations are characterized by OSCT absorptions in their electronic spectra. Many ion pairs of this type are photoactive upon OSCT excitation.