Supramolecular Architecture in Gold(I) and Gold(III) 2-Pyridineformamide Thiosemicarbazone Complexes by Secondary Interactions: Synthesis, Structures, and Luminescent Properties

Abstract

Reaction of the thiosemicarbazone ligands 2-pyridineformamide thiosemicarbazone (HAm4DH) or 2-pyridineformamide 3-hexamethyleneiminylthiosemicarbazone (HAm4hexim) with the gold(I) compound [AuCl(tdg)] (tdg = thiodiglycol = 2,2′-thiodiethanol) gives the complexes [Au(H2Am4DH)2]Cl3·H2O (1) and [Au(HAm4hexim)2]Cl (2). The room temperature oxidation of solutions of 2 in water/methanol leads to the crystallization of a gold(III) complex of formula [Au(Am4hexim)Cl]Cl·2H2O (3). Single-crystal X-ray diffraction analysis revealed that in compounds 1 and 2 gold(I) is linearly coordinated to sulfur atoms from two monodentate thiosemicarbazone molecules. Packing architectures and hydrogen bonding networks obtained using graph set notations are discussed for all complexes. Weak agostic interactions exist in both 1 [(N–H)···Au; H···Au = 2.70 and 2.82 Å] and 2 [(C–H)···Au; H···Au = 2.79 Å], and gold–gold contacts are present in the solid state in 1 (Au···Au = 3.83 Å) but not in 2 (Au···Au = 5.46 Å). The fluorescence of the ligands and complexes of gold(I) was studied. In addition, elemental analysis data and spectroscopic properties in the solid state and in solution are also described for complexes 1 and 2.