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

The second-order response of the [MXY] (M= Ni, Pd, Pt; X=R2timdt (monoanion of 1,3-dialkyl imidazolidine-2,4,5-trithione), dmit (2-thioxo-1,3-dithiole-4,5-dithiolate), mnt (maleonitriledithiolate); Y=R2timdt, dmit, mnt; X≠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 β 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 [Pt(H2timdt)(dmit)] response the largest one among the analyzed ones. In particular, the static βvec value is −40.3(×10−30 esu).