Synthesis, crystal structure, magnetic and vibrational properties of formamidine-templated Co and Fe formates

Two novel Co and Fe formates, [NH2-CH-NH2][Co(HCOO)(3)] and [NH2-CH-NH2][Fe(HCOO)(3)], containing formamidinium cations [FMD+, NH2-CH+-NH2] have been prepared under solvothermal conditions. Crystal structure determination shows that these compounds are isostructural and crystallize in the orthorhombic structure, space group Pnna. The FMD+ cations, located in the cavities of the metal formate framework, form extensive N-H center dot center dot center dot O hydrogen bonding with the framework and they are ordered at room temperature. The divalent cations have octahedral geometry and are bridged by the formate ions in an anti-anti mode of coordination. A magnetic study revealed that these compounds are weak ferromagnets, with the critical temperatures of 13.0 K (Co) and 17.0 K (Fe). Based on IR and Raman data, an assignment of the observed modes has been proposed. (C) 2014 Elsevier Ltd. All rights reserved.