Coordination preference and magnetic properties of FeII assemblies with a bis-azole bearing 1,2,4-triazole and tetrazole

With a new bis-azole molecular fragment (Htt) bearing 1,2,4-triazole and tetrazole, a mononuclear complex [Fe(tt) 2(H 2O) 4]·2H 2O (1), a trinuclear complex [Fe 3(tt) 6(H 2O) 6]·2H 2O (2) and a 1D coordination polymer [Fe(tt)(Htt) 2]BF 4·2CH 3OH (3) were obtained by varying reaction conditions. Htt acts either as an anionic or neutral ligand depending upon the reaction medium and pH. Thermal variation of spin states of 1-3 were investigated in the range 77-300 K by 57Fe Mössbauer spectroscopy. 1 totally remains in high-spin state over the entire temperature range whereas no spin crossover was evidenced in 2. Nearly 1:1 high-spin and low-spin population ratio is found in 3, which remains constant over the entire temperature range investigated. © 2011 Springer Science+Business Media B.V