Experimental and theoretical evidence of unsupported Ag-Ag interactions in complexes with triazine-based ligands. Subtle effects of the symmetry of the triazine substituents

The synthesis of several dimeric silver compounds containing bis(pyrazol-1-yl)-6-(R)-s-triazine or bis(3,5-dimethylpyrazol-1-yl)-6-(R)-s-triazine ligands and coordinated triflate is described. The structures of two of the compounds have been determined by X-ray diffraction. Both derivatives show ligand-unsupported argentophilic contacts and different supramolecular interactions such as pi-pi stacking, CH-pi or anion-pi interactions. Hydrogen bonds are also established between the monomers. The relative orientation of the two monomers, which is mainly influenced by the formation of hydrogen bonds, reflects the symmetry of the R substituent of the triazine ring. Theoretical DFT calculations and Natural Bond Order (NBO) analysis of the two dimers further support the existence of the argentophilic interactions. Differences between the optimized and real structures can be mainly attributed to the underestimation of the pi-pi stacking interaction in the DFT studies.