[Fe(abpt)2(NCSe)2] polymorph A: structural studies into the spin crossover behaviour

The spin crossover behaviour of [Fe(abpt)2(NCSe)2] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) polymorph A has been examined using single crystal X-ray diffraction and variable temperature UV-Vis transmission spectroscopy. The crystal structure of A is reported at sixteen temperatures between 30 and 375 K, all of which are in the monoclinic space group P21/n with Z’ = 0.5. Changes in the crystallographic cell parameters, bond lengths, distortion parameters and intra and intermolecular interactions between 375 K and 30 K are discussed. Continuous irradiation with a 670 nm, 5 mW CW laser at 30 K enabled a light induced excited spin state trapping (LIESST) metastable high spin structure, HS*, to be obtained.