Tuning Au(I)···Tl(I) interactions via mixed thia- aza-macrocyclic ligands: effects on the structural and luminescence properties

Reaction of the heterometallic complexes [{Au(C6X5)2}Tl]n (X = Cl, F) with equimolecular amounts of the N,S-mixed-donor crown ethers [12]aneNS3 or [12]aneN2S2 affords the new Au(I)/Tl(I) derivatives [{Au(C6Cl5)2}{Tl(L)}2][Au(C6Cl5)2] [L = [12]aneNS3 (1), [12]aneN2S2 (2)], [{Au(C6F5)2}Tl([12]aneNS3)]2 (3), or [{Au(C6F5)2}Tl([12]aneN2S2)]n (4). These complexes display the same Au/Tl metal ratio, but different structural arrangements. While the chlorinated derivatives 1 and 2·2THF display an ionic structure, the crystal structure of 3 contains neutral tetranuclear Au2Tl2 units, and complex 4 displays a polymeric nature and is the only one that does not show unsupported Au···Tl interactions. The lack of this interaction is responsible for the absence of luminescence in this last case. The optical properties of 1 and 3 in the solid state have been studied experimentally and theoretically, concluding that their luminescence has its origin in the Au···Tl interactions, and this is also influenced by their number and strength. DFT and TD-DFT theoretical calculations on model systems of complexes 1, 3, and 4 have been carried out in order to confirm the origin of their luminescence or its absence, as well as to justify their emission energies in spite of their different solid state structures.