1,4-Bis(2′-pyridylethynyl)benzene as a ligand in heteronuclear gold–thallium complexes. Influence of the ancillary ligands on their optical properties

Abstract

The reaction of 1,4-bis(2′-pyridylethynyl)benzene (L) with [{Au(C₆X₅)₂}Tl]_n affords new heterometallic Au^I/Tl^I complexes with different stoichiometries, structural arrangements and optical properties depending on the halogens present in the aryl group. The chlorinated derivative [{Au(C₆Cl₅)₂}Tl(L)]_n (1) displays polymeric chains built thanks to unsupported Au⋯Tl interactions and bridging bidentate ligands between adjacent chains, while in the fluorinated species [{Au(C₆F₅)₂}₂Tl₂(L)₂]_n (2), also containing N-donor bridging ligands and Au⋯Tl contacts, polymerization occurs via Tl⋯C_aryl non-bonding interactions between neighbouring molecules. The optical properties of 1 and 2 have been studied experimentally and theoretically, concluding that the luminescence of 1 in the solid state has its origin in the Au⋯Tl interactions, and that the Tl⋯C_aryl interactions in 2 favour a non-radiative deactivation pathway that avoids luminescence. The strength of the non-bonding interactions present in 1 has also been theoretically studied at the HF and MP2 levels, revealing the metallophilic contact as the strongest one.