Luminescent nido-Carborane-Diphosphine Anions [(PR2)2C2B9H10] (R = Ph, Pr). Modification of Their Luminescence Properties upon Formation of Three-Coordinate Gold(l) Complexes

The free nido-diphosphine anions [(PR2)2C2B9H10]~ (R = Ph, ʹPr) show luminescence properties whereas the closodiphosphines [(PR2)2C2B10H10] do not. Four families of three-coordinate complexes of stoichiometry [Au{(PR2)2C2B10H10}L]OTf (L = tertiary phosphine) and [Au{(PR2)2C2B9H10}L] have been studied in order to analyze the influence of the closo- or nido-nature of the diphosphine, the monophosphine coordinated to gold and the substituent at the diphosphine on the luminescence of the complexes. Only the nido-derivatives show luminescence. The maxima of the emissions are shifted to lower energies than those of the corresponding free nido-diphosphines. When the substituent at the diphosphine is phenyl, a new emission appears, which has been assigned as arising from a metal to ligand charge transfer [Au—Pi*(L)] excited state.