Optical non-linear properties of the [MXY] neutral mixed-ligand dithiolenes (M=Ni, Pd, Pt; <f>X=R2timdt</f>, dmit, mnt; <f>Y=R2timdt</f>, dmit, mnt; <f>X≠Y</f>). The role of coordinated metal, substituents and of high lying excited states

The second-order response of the [MXY] (M= Ni, Pd, Pt; <f>X=R2timdt</f> (monoanion of 1,3-dialkyl imidazolidine-2,4,5-trithione), dmit (2-thioxo-1,3-dithiole-4,5-dithiolate), mnt (maleonitriledithiolate); <f>Y=R2timdt</f>, dmit, mnt; <f>X≠Y</f>) 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 <f>β</f> tensor components have been calculated off-resonance at 4.48, 3.50 and 2.50 μm. A small HOMO–LUMO energy gap and the presence of a heavy metal make the [<f>Pt(H2timdt)(dmit)</f>] response the largest one among the analyzed ones. In particular, the static <f>βvec</f> value is −40.3(<f>×10−30</f> esu). [Copyright &y& Elsevier]