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