Ground and excited states of [M(H(2)timdt)(2)] neutral dithiolenes (M = Ni, Pd, Pt; H(2)timdt = monoanion of imidazolidine-2,4,5-trithione): Description within TDDFT and scalar relativistic (ZORA) approaches

Nonrelativistic and relativistic time-dependent density functional calculations have been performed on the excited states of the [M(H(2)timdt)(2)] (M = Ni, Pd, Pt) compounds. These complexes are characterized by an absorption at about lambda = 1000 nm of rarely encountered intensity (is an element of approximate to 8000 M-1 cm(-1)) compared to those of similar compounds, attributed to a pi > pi* electronic transition between the HOMO and the LUMO. The comparison of the calculated spectra with the experimental data allows a possible assignment of the spectra. Our results confirm that, in all members of the series, the excited state at the lowest energy corresponds to a HOMO > LUMO excitation and indicate that a large number of the transitions have an intraligand character. No relevant direct relativistic effects can be observed on the pattern of the excited states and on energy differences between them as well. The main relativistic effect is due to the metal-sulfur bond contraction, which in contrast has considerable effect on the electronic structures.