Spin-state-associated ligand distortion and complex solution equilibrium for a pair of Fe(II) pyridyl-imidazoline complexes

Two new Fe(II) complexes with different Fe:pyridyl-imidazoline ratios are reported, which show unique structures depending on their spin states. In methanolic solutions, the species are in equilibrium as observed from spectroscopic studies. Spin-state switching between 1 and 2 in solution is a result of ligand exchange.