Introducing Selenium in Single-Component Molecular Conductors Based on Nickel Bis(dithiolene) Complexes

Two selenated analogues of the all-sulfur single-component molecular conductor [Ni(Et-thiazdt)2] (Et-thiazdt = N-ethylthiazoline-2-thione-4,5-dithiolate) have been prepared from their precursor radical-anion complexes. Replacement thione by a selenone moiety gives neutral [Ni(Et-thiazSedt)2] complex. It adopts an unprecedented solid-state organization (for nickel complexes), with formation perfectly eclipsed dimers and very short intermolecular Se···Se contacts (81% van der Waals contact distance). Limited interactions between leads to large semiconducting gap low conductivity (?RT 1.7 × 10-5 S cm-1). On other hand, going dithiolene complex corresponding [Ni(Et-thiazds)2] diselenolene rise more conventional layered structure built out uniform stacks complexes, different, however, analogue [Ni(Et-thiazdt)2]. Band calculations show essentially 1D electronic band dispersion small HOMO-LUMO gap. Under high pressures (up 19 GPa), increases 4 orders magnitude activation energy is decreased 120 meV only 13 meV, abrupt change observed around 10 GPa, suggesting structural phase transition under pressure.