Optical non-linear properties of the [MXY] neutral mixed-ligand dithiolenes (M=Ni, Pd, Pt; X=R(2)timdt, dmit, mnt; Y=R(2)timdt, dmit, mnt; X=AY). The role of coordinated metal, substituents and of high lying excited states

The second-order response of the [MXY] (M = Ni, Pd, Pt; X = R(2)timdt (monoanion of 1,3-dialkyl imidazolidine-2,4,5-trithione), dmit (2-thioxo-1,3-dithiole-4,5-dithiolate), mnt (maleonitriledithiolate); Y = R(2)timdt, dmit, mut; X not equal Y) neutral mixed-ligand dithiolenes has been investigated within the TD-DFT approach. Scalar relativistic contributions have been considered on both optimized geometry and hyperpolarizability using the zero-order regular approximation (ZORA). All beta tensor components have been calculated off-resonance at 4.48, 3.50 and 2.50 mum. A small HOMO-LUMO energy gap and the presence of a heavy metal make the [Pt(H(2)timdt)(dmit)] response the largest one among the analyzed ones. In particular, the static beta(vec) value is -40.3(x 10(-30) esu). (C) 2003 Elsevier Science B.V. All rights reserved.