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

<jats:title>Abstract</jats:title><jats:p>The organodiselone ligands 1,1‐bis(3‐methyl‐4‐imidazolin‐2‐selone)methane (<jats:bold>L1</jats:bold>) and 1,2‐bis(3‐methyl‐4‐imidazolin‐2‐selone)ethane (<jats:bold>L2</jats:bold>) have been used for the synthesis of homopolynuclear Tl<jats:sup>I</jats:sup> [{Tl(<jats:bold>L</jats:bold>)}PF<jats:sub>6</jats:sub>]<jats:italic><jats:sub>n</jats:sub></jats:italic><jats:bold>·</jats:bold>(<jats:italic>m</jats:italic>MeCN)<jats:italic><jats:sub>n</jats:sub></jats:italic> [<jats:bold>L</jats:bold> = <jats:bold>L1</jats:bold>, <jats:italic>m</jats:italic> = 1 (<jats:bold>1</jats:bold>); L = <jats:bold>L2</jats:bold>, <jats:italic>m</jats:italic> = 0 (<jats:bold>2</jats:bold>)] and discrete heteropolynuclear [Tl{Au(C<jats:sub>6</jats:sub>Cl<jats:sub>5</jats:sub>)<jats:sub>2</jats:sub>}(<jats:bold>L</jats:bold>)] [L = <jats:bold>L1</jats:bold> (<jats:bold>3</jats:bold>), <jats:bold>L2</jats:bold> (<jats:bold>4</jats:bold>)] complexes. The crystal structures of complexes <jats:bold>1</jats:bold> and <jats:bold>3</jats:bold> have been determined through X‐ray diffraction studies. Complex <jats:bold>1</jats:bold> consists of alternating thallium(I) centres and bidentate Se‐donor ligands that result in polymeric chains. The crystal structure of <jats:bold>3</jats:bold> is formed by [Tl(<jats:bold>L1</jats:bold>)]<jats:sup>+</jats:sup> cations and [Au(C<jats:sub>6</jats:sub>Cl<jats:sub>5</jats:sub>)<jats:sub>2</jats:sub>]<jats:sup>–</jats:sup> anions joined together by an unsupported Au<jats:bold>···</jats:bold>Tl interaction. Compounds <jats:bold>3</jats:bold> and <jats:bold>4</jats:bold> 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 <jats:bold>L1</jats:bold>, a representative model of complex <jats:bold>1</jats:bold> and a model system of complex <jats:bold>3</jats:bold>. 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 <jats:bold>3</jats:bold> and <jats:bold>4</jats:bold> as an admixture of metal–metal (Au–Tl)‐to‐ligand charge transfer (MMLCT) and intraligand (IL) transitions as observed experimentally.</jats:p>