Two neutral mononuclear iron(II) complexes with different spin-crossover (SCO) properties, Fe(L1)(2)(SCN)(2) (1) and Fe(L2)(2)(SCN)(2) (2) (L1 = 2-(thiophen-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and L2 = 2-(thiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), were solvothermally synthesized. With the different substituted position in 1,10-phenanthroline derivatives, 1 exhibits gradual SCO around room temperature with T-1/2 = 280 K, while 2 displays abrupt SCO with 10 K hysteresis at T-1/2 down arrow = 210 K and T-1/2 up arrow = 220 K.