A unique example of a co-crystal of [Ag(atr)2][Cr(dipic)2] (dipic = dipicolinate; atr = 3-amino-1H-1,2,4-triazole) and dinuclear [Cr(H2O)(dipic)(μ-OH)]2, with different coordination environment of Cr(III) ions

Treatment of a neutral aqueous solution of dipicolinic acid (dipicH2), 3-amino-1H-1,2,4-triazole (atr) and CrCl3·6H2O in the presence of AgNO3 (in molar ratio 1:1:1:3) under hydrothermal condition led to the formation of a co-crystal of {[Ag(atr)2][Cr(dipic)2]}2·[Cr(H2O)(dipic)(μ-OH)]2·4H2O (1). Compound 1 was characterized by elemental analyses, IR and UV–Vis spectroscopy as well as X-ray diffraction studies. The structure consists of two [Ag(atr)2]+ cations, two [Cr(dipic)2]− anions, one co-crystallized neutral dinuclear chromium(III) complex, [Cr(H2O)(dipic)(μ-OH)]2, and four co-crystallized water molecules. Silver(I) ion in [Ag(atr)2]+ is coordinated by two monodentate 3-amino-1H-1,2,4-triazole ligands, bound via endocyclic nitrogen atoms, in a linear fashion. Chromium(III) ion is octahedrally coordinated by two O,N,O-tridentate dipicolinate ligands in anionic complex. Each chromium(III) ion in neutral dinuclear complex, [Cr(H2O)(dipic)(μ-OH)]2, is octahedrally coordinated by one O,N,O-tridentate dipicolinate ligand, one water molecule and two bridging μ-OH ions in cis position. Thermal methods (TGA/DTA) confirm the number of co-crystallized water molecules in 1.

A co-crystal of [Ag(atr)2][Cr(dipic)2] (dipic = dipicolinate; atr = 3-amino-1H-1,2,4-triazole) and dinuclear [Cr(H2O)(dipic)(μ-OH)]2, with different coordination environment of Cr(III) ions, was prepared and characterized by spectroscopic (IR and UV–Vis) and thermal methods, while its crystal structure was revealed by X-ray structural analysis.Figure optionsDownload as PowerPoint slideResearch highlights
► A co-crystal of [Ag(atr)2][Cr(dipic)2] and dinuclear [Cr(H2O)(dipic)(μ-OH)]2 prepared.
► Different coordination environment of Cr(III) ions in complex anion and neutral complex.
► Use of [Ag(atr)2]+ as a complex cation for the first time.
► Characterization by spectroscopic (IR and UV–Vis) and thermal methods.