Effect of π-Conjugated Length of Bridging Ligand on the Optoelectronic Properties of Platinum(II) Dimers

We report a quantum-chemical study of the electronic and optical properties of several platinum(II) dimers, [Pt(pip2NCN)]2(L)2+ (pip2NCNH = 1,3-bis(piperidylmethyl)benzene, L represents the bridging ligands pyrazine, 4,4′-bipyridine, or trans-1,2-bis(4-pyridyl)ethylene). The theoretical calculations reveal that as the π-conjugated length of bridging ligand increases, the energies of HOMOs and LUMOs, bonding energy of Pt−Nbridge, and the largest absorption strength increase whereas the ionization potentials decrease. According to the inner reorganization energy and density of states, we presume the hole-transporting properties of these dimers is better than the electron-transporting, and their inner reorganization energies for hole transport are lower than that of 4,4′-bis(phenyl-m-tolylamino)biphenyl (TPD), a well-known hole-transporting material. These platinum(II) dimers, especially [Pt(pip2NCN)]2(bpe)2+, hold promise for use as a new kind of third-order nonlinear optical material, owing to their large ...