Synthesis, characterization and DFT calculations of a novel hexanuclear silver(I) cluster-complex containing 4-ethyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazol-3-thione as a result from the cyclization of 2-pyridinformamide N-4-ethylthiosemicarbazone

Reaction of 2-pyridine N-4 ethylthiosemicarbazone, HAm4E, with AgNO3 leads to the hexanuclear compound [Ag(E124tazt)]6 (1) (HE124tazt = 4-ethyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazol-3-thione), the result of an oxidative cyclization of the starting thiosemicarbazone. All Ag atoms of [Ag(E124tazt)]6 are bridged through the six S atoms of the deprotonated E124tazt ligand to form two bridged Ag3S3 rings. Each silver atom exhibits a trigonal planar coordination geometry bonded to two thiolate S atoms and one N atom from the bidentate E124tazt ligand. The Ag⋯Ag distances are much shorter than the van der Waals’ radius sum for silver(I), suggesting binding interactions between the silver atoms, which were confirmed by means of DFT calculations. The X-ray single-crystal structural analysis reveals the arrangement of 1 as a two-dimensional (2D) network via π–π stacking interactions. Preliminary luminescence measurements have been carried out.

A new hexanuclear silver triazol-3-thiolato complex, 1, was synthesized and fully characterized, including X-ray crystal structure determination, that show the stabilization of the whole structure by π–π stacking interactions. DFT calculations reveal that three of the MOs with Ag atomic orbital contributions clearly show d-d-σ-bonding. Luminescence experiments show an unusual fluorescence emission with two components, suggesting weak coupled relaxation channels.Figure optionsDownload as PowerPoint slide