Synthesis, structural characterisation, photophysics, photochemistry and electrochemistry of nitrido- and trans-dioxorhenium(V) complexes with substituted dppe ligands (dppe=bis(diphenylphosphino)ethane)

A series of nitrido- and trans-dioxorhenium(V) complexes with substituted dppe ligands have been synthesised and characterised, and their photophysics and electrochemistry studied. The excited state chemistry of [Re(N)(dmppe)2(MeCN)]2+ has also been investigated. The structures of [Re(N)(dmppe)2Cl]+ and [Re(O)2(dmppe)2]+ have been determined by X-ray crystallography. The electronic absorption bands of the nitrido complexes at ca. 230–300 nm are assigned as intraligand and ligand-to-metal charge-transfer transitions [pπ(N3−)→dπ*(Re) and pπ(Cl−)→dπ*(Re)] and the weak absorption at ca. 360–480 nm as a (dxy)2→(dxy)1(dπ*)1 transition (dπ*=dxz, dyz). All these complexes display long-lived solid-state photoluminescence which is likely to be derived from the [(dxy)1(dπ*)1] triplet state. They also show emission in fluid solution. Bimolecular quenching has been studied for [Re(N)(dmppe)2(MeCN)]2+.