1D iron(II) spin crossover complexes with 1,2,4-triazol-4-yl-propanoic acid

Abstract

A series of 1D coordination polymers [Fe(patrz)3]X2·solv, (patrz = 1,2,4-triazol-4-yl-propanoic acid; X = BF\(_{4}^{-}\), ClO\(_{4}^{-}\), Cl − , NO\(_{3}^{-}\) and solv = MeOH or H2O) were precipitated from methanol. Their spin crossover properties were studied by temperature dependent SQUID magnetometry and 57Fe Mossbauer spectroscopy, both for solvated and desolvated complexes. Compounds show gradual incomplete spin crossover with distinct thermochromism, in particular [Fe(patrz)3](BF4)2·MeOH, for which only 27% of FeII ions are switched to the low-spin state at 77 K, as determined by a detailed 57Fe Mossbauer study. Other prominent features of this work are the interesting self assembly of 1D chain with exclusively triazole coordination from patrz ligand despite its ditopic nature and a hysteretic room temperature spin crossover in [Fe(patrz)3]Cl2.