Photophysics of three-coordinate Au(I) complexes: Fundamentals and applications in molecular light-emitting diodes

INOR 927

Pankaj Sinha, ps0075@unt.edu1, Divya Kosuri, divya_kosuri@yahoo.com2, Nigel D. Shepherd2, Angela K. Wilson, akwilson@unt.edu1, and Mohammad A. Omary, omary@unt.edu1. (1) Department of Chemistry, University of North Texas, Denton, TX 76203-2115, (2) University of North Texas, Department of Materials Science and Engineering, Denton, TX 76203
Three-coordinate cationic [AuL3]+ and neutral L2Au(I)X complexes (where L = phosphine and X = halide) have been studied experimentally and computationally. These compounds exhibit bright emissions ranging from blue to red with short phosphorescence lifetimes ranging from 1-50 microseconds. The photophysical behavior of these complexes entails large Stokes' shifts (10000-18000 cm-1) and broad structureless emission profiles indicative of Au-centered phosphorescent emissions, as well as ligand-centered emissions observable at cryogenic temperatures. The fascinating photophysical properties of these compounds include sensitivity to the media, temperature, and morphology. DFT and ab initio calculations have identified the origin of the large Stokes' shift via full optimization of the phosphorescent triplet state as well as scan calculations for the triplet state distortion as a function of the multiple normal modes. It was found that the major distortion is rooted in a drastic structural distortion from a “Y-shape” in the singlet ground state toward and beyond a “T-shape” in the lowest-energy triplet excited state. Preliminary results will be presented to show the potential applicability of thin films of the neutral complexes as candidates for molecular light-emitting diodes.