Remarkable structural transformation of [Zn(tza)2] during recrystallization, syntheses and crystal structures of [M(tza)2] (M = Zn, Cd, Mn, Co; Htza = tetrazole-1-acetic acid)

The substitution reactions of M(CH3CH2CO2)(2) and Htza afford the crystalline precipitates-of [Cd(tza)(2)] (1), [Mn(tza)(2)] (2), [Co(tza)(2)] (3), and beta-[Zn(tza)(2)] (5). The recrystallization of 5 leads to the formation of alpha-[Zn(tza)(2)] (4). X-ray powder diffraction of 1-5 reveal that 1, 2, 3, and 5 are allomers, but 4 and 5 are isomers, revealing the unprecedented structural transformation during the process of recrystallization. Compounds 1-4 have been characterized by X-ray single-crystal crystallography, IR, and magnetism analysis. Structural analyses and comparison of 1-4 detail the structural evolution of from beta-[Zn(tza)(2)] (5) to alpha-[Zn(tza)(2)] (4) and possible driving force has been proposed. The interactions between the Mn-II ions of 2 have been observed as weakly antiferromagnetic.