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 (dipicH(2)), 3-amino-1H-1,2,4-triazole (atr) and CrCl3 center dot 6H(2)O 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)center dot[Cr(H2O)(dipic)(mu-OH)](2)center dot 4H(2)O (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)(mu-OH)](2), and four co-crystallized water molecules. Silver(1) 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 0,N,O-tridentate dipicolinate ligands in anionic complex. Each chromium(III) ion in neutral dinuclear complex, [Cr(H2O)(dipic)(mu-OH)](2), is octahedrally coordinated by one 0,N,O-tridentate dipicolinate ligand, one water molecule and two bridging mu-OH ions in cis position. Thermal methods (TGA/DTA) confirm the number of co-crystallized water molecules in 1. (C) 2011 Elsevier Ltd. All rights reserved.