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(H_2O)(dipic)(μ-OH)]_2, with different coordination environment of Cr(III) ions

摘要

Treatment of a neutral aqueous solution of dipicolinic acid (dipicH _2), 3-amino-1H-1,2,4-triazole (atr) and CrCl_3· 6H_2O in the presence of AgNO_3 (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(H _2O)(dipic)(μ-OH)]_2·4H_2O (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(H _2O)(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(H_2O)(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.