Structural Distortion Controlled Spin-Crossover Behavior

Two mononuclear isomorphous complexes Fe(L1)2(SCN)2 (1) and Fe(L2)2(SCN)2 (2) [L1 = 2-(pyridin-3-yl)-1H-imidazo[4,5-f]1,10-phenanthroline; L2 = 2-(pyridin-4-yl)-1H-imidazo[4,5-f]1,10-phenanthroline] were obtained based on 1,10-phenanthroline derivatives. Due to the different structural distortion in the coordination geometries, 1 exhibits gradual spin transition around room temperature (T1/2 = 315 K), while 2 displays a stable high-spin state.