SYNTHESIS, STRUCTURE, LUMINESCENCE, AND RAMAN-DETERMINED EXCITED-STATE DISTORTIONS OF A TRINUCLEAR GOLD(I) PHOSPHINE THIOLATE COMPLEX

The synthesis, crystal structure and spectroscopic properties of a new luminescent trinuclear gold complex, bis(triethylphosphine)gold(I) [m u-(1,1-dicyanoethylene-2,2-dithiolato-1 kappa S:2 kappa S')][mu-(1,1-d icyanoethylene-2,2-dithilato-2 kappa S2:3 kappa S')] (triethylphosphin e-1 kappa P)(triethylphosphine-3 kappa P)triaurate(I), 1, are reported . The structure contains a linear array of three gold atoms, the centr al gold on an inversion center. 1 crystallizes in the P2(1)/n space gr oup with a = 13.681(1) Angstrom, b = 11.433(1) Angstrom, c = 15.608(1) Angstrom, beta = 106.93(1)degrees, V = 2335.4(3) Angstrom(3), and Z = 2. The luminescence spectrum is centered at 19 600 cm(-1) and display s poorly resolved vibronic structure with a spacing of 470 cm(-1), cha racteristic of a normal mode primarily Au-S in character. The transiti on is assigned to a dithiolate to gold charge transfer. The vibrationa l frequencies and intensities obtained from the preresonance Raman spe ctra are used to calculate the distortions the molecule undergoes when excited to its emissive charge transfer excited state. The largest di stortions are along the C=C normal mode centered on the dithiolate lig and and along the Au-S stretching coordinate. These distortions assist in making the charge transfer assignment as dithiolate to gold. The a nalysis of the emission spectrum and the preresonance Raman spectrum u sing the time-dependent theory of electronic spectroscopy is discussed .