Synergistic σ/π-Hole Interactions Directing Supramolecular Assembly: Tellurium···Platinum Chalcogen Bonding Enhanced by π-Stacking

Abstract

This study investigates the synergistic effects of σ- and π-hole interactions in directing supramolecular assembly, focusing on unusual Te^II···Pt^II chalcogen bonding enhanced by π-stacking. Three novel cocrystals were synthesized and characterized, combining the dithiocarbamate complexes [Pt(ppy)(S₂CNC₆H₁₂)] and [Pt(ppy)(S₂CNC₄H₈)] (where ppyH = 2-phenylpyridine) with the tellurium(II)-based mixed σ/π-hole donors Te(C₅F₄N-4)₂ and Te(C₆F₄CF₃-4)₂. X-ray crystallography revealed a diverse array of noncovalent interactions, including two-center Te···Pt and three-center Te···(Pt,S) and Te···(Pt,C) chalcogen bonds, where the σ-Te^II-hole interacts directly with the d_z²-orbital of the positively charged platinum(II) ion. These unusual chalcogen bonds are significantly reinforced by π-stacking between the electron-deficient aromatic rings and platinum complex ligands. This combination of σ- and π-hole-based contacts leads to more robust and diverse supramolecular architectures compared to systems with isolated interactions. Theoretical calculations using QTAIM, NCIPlot, and NBO methods closely interrogated the interplay of these noncovalent forces highlighting the important role of electronic effects in controlling the balance between chalcogen bond and the π-stacking.