Theoretical and photoluminescence studies on the d10-s2 AuI-TlI interaction in extended unsupported chains

The reactions of solutions of TlPF6 and OPPh3 in tetrahydrofuran or acetone with NBu4[AuR2] (R C6Cl5 , C6F5) gave the new complexes [Au(C6Cl5)2]2[Tl(OPPh3)][Tl(OPPh3)(L)] (L THF (1), acetone (2)) and the previously reported [Tl(OPPh3)2]- [Au(C6F5)2] (3). The crystal structures of complexes 1 and 2 display extended unsupported chains with short intermolecular interactions between alternating gold( ) and thallium( ) centres. Moreover, the TlI centres show two different types of geometrical environments, such as pseudotetrahedral and distorted trigonal-bipyramidal, due to the presence of solvent molecules that act as ligands in the solid-state structure. Quasirelativistic and nonrelativistic ab initio calculations were performed to study the nature of the intermetallic AuI ± TlI interactions and are consistent with the presence of a high ionic contribution (80%) and dispersion-type (van der - Waals) interaction with a charge-transfer contribution (20%) when relativistic effects are taken into account. All complexes are luminescent in the solid state at room temperature and at 77 K. Complexes 1 and 2 show site-selective excitation, probably due to the different environments around the TlI centres. The DFT and time-dependent (TD)- DFT calculations are in agreement with the experimental excitation spectra for all complexes and confirm the siteselective excitation behaviour as a function of the TlI geometrical environment