Synthesis, characterization, magnetic and theoretical studies on Fe(II) spin-crossover complex based on 4-cyclohexyl-1,2,4-triazole

4-cyclohexyl-1,2,4-triazole (4-C6trz) was synthesized and used as a ligand to prepare Fe(II) complex of the formula [FeII(4-C6trz)3](BF4)2<middle dot>4H2O. The complex was characterized spectroscopically, magnetically, and thermally. The characterization of the complex proved the polymeric nature of the complex and the triazole ligand acted as a bridging ligand. The prepared structure has the formula confirmed to be [FeII(4-C6trz)3](BF4)2<middle dot>4H2O. The chi T product of [FeII(4-C6trz)3](BF4)2<middle dot>4H2O was almost constant over 200 - 400 K, and the measured value (3.6 cm3mol-1K) is expected to be the paramagnetic high-spin Fe(II) complexes (S = 2). Density Functional Theory (DFT) calculations were conducted on [FeII(4-C6trz)3](BF4)2<middle dot>4H2O to rationalize the experimentally observed magnetic behavior measured using the magnetometer. The results predict that the 4-cyclohexyl-1,2,4-triazole (4-C6trz) ligand provides a pi-acceptor environment in the first coordination, which helps to show spin crossover transition with a transition temperature of 215 K.