Homopolynuclear Tl^I and Heteropolynuclear Au^I–Tl^I Complexes with Organodiselone Ligands: Activation of Luminescence by Intermetallic Interactions

Abstract

Abstract The organodiselone ligands 1,1‐bis(3‐methyl‐4‐imidazolin‐2‐selone)methane ( L1 ) and 1,2‐bis(3‐methyl‐4‐imidazolin‐2‐selone)ethane ( L2 ) have been used for the synthesis of homopolynuclear Tl I [{Tl( L )}PF 6 ] n · ( m MeCN) n [ L = L1 , m = 1 ( 1 ); L = L2 , m = 0 ( 2 )] and discrete heteropolynuclear [Tl{Au(C 6 Cl 5 ) 2 }( L )] [L = L1 ( 3 ), L2 ( 4 )] complexes. The crystal structures of complexes 1 and 3 have been determined through X‐ray diffraction studies. Complex 1 consists of alternating thallium(I) centres and bidentate Se‐donor ligands that result in polymeric chains. The crystal structure of 3 is formed by [Tl( L1 )] + cations and [Au(C 6 Cl 5 ) 2 ] – anions joined together by an unsupported Au ··· Tl interaction. Compounds 3 and 4 are luminescent in the solid state at room temperature and at 77 K with lifetimes in the nanosecond range. DFT and time‐dependent (TD)‐DFT calculations have been carried out on different model systems including the free ligand L1 , a representative model of complex 1 and a model system of complex 3 . The character of the frontier molecular orbitals and the TD‐DFT prediction of the absorption spectra are used to explain the origin of the luminescence of complexes 3 and 4 as an admixture of metal–metal (Au–Tl)‐to‐ligand charge transfer (MMLCT) and intraligand (IL) transitions as observed experimentally.