LUMINESCENT HETEROBIMETALLIC COMPLEXES - ELECTRONIC-STRUCTURE, SPECTROSCOPY, AND PHOTOCHEMISTRY OF [AUPT(DPPM)2(CN)2]CLO4 AND THE X-RAY CRYSTAL-STRUCTURE OF [AGPT(DPPM)2(CN)2(CF3SO3)]

The d10-d8 heterobimetallic complexes [AuPt(dppm)2(CN)2]ClO4 and [AgPt(dppm)2(CN)2(CF3SO3)] (dppm = bis(diphenylphosphino)methane) were prepared by literature methods. The X-ray crystal structure of [AgPt(dppm)2(CN)2(CF3SO3)] has been determined. Crystal data for [AgPt(dppm)2(CN)2(CF3SO3)]: monoclinic, space group P2(1) a = 10.453(2) angstrom, b = 16.372(4) angstrom, c = 14.846(6) angstrom, and beta = 92.17(2)degrees. The intramolecular Pt...Ag distance is 3.002(1) angstrom. The absorption spectra of [AuPt(dppm)2(CN)2]ClO4 and [AgPt(dppm)2(CN)2(CF3SO3)] exhibit intense 1(dsigma* --> psigma) transitions at 323 nm and 317 nm, respectively. The results of extended Huckel molecular orbital calculations suggested that the dsigma* orbital in each case is mainly composed of the Pt(5d(z)2) orbital. In acetonitrile and at room temperature, [AuPt(dppm)2(CN)2]ClO4 exhibits a broad emission (lifetime = 18 mus) at 570 nm. The emitting state has been suggested to be 3(ddelta*psigma). The effect of solvent on the emission properties has been investigated. The [AgPt(dppm)2(CN)2(CF3SO3)] complex shows metal-perturbed intraligand emission in glass solution at 77 K. The rate constants of quenching of the excited state of [AuPt(dppm)2(CN)2]+ by pyridinium acceptors have been treated by Marcus quadratic, Rehn-Weller, and Agmon-Levine equations and the excited state reduction potential of [AuPt(dppm)2(CN)2]+, [Au-Pt]2+ + e- --> [Au-Pt]+*, is estimated to be about -1.73 to -1.80 V vs SCE. The photoreactions of [AuPt(dppm)2(CN)2]+ with halocarbons were investigated by Stern-Volmer quenching, flash photolysis, and steady-state photolysis experiments. An electron transfer mechanism is suggested.