Spin-crossover (SCO) iron(III) compounds, [Fe(qual-OMe)(2)]PF6 center dot acetone (1) and [Fe(qnal-OMe)(2)]BPh4 center dot 2MeOH (2) (qnal-OMe: 7-methoxy-1-[(8-quinolinylimino)methyl]-2-naphthalenol), were prepared and characterized by X-ray single-crystal structure analysis, temperature-dependent magnetic susceptibility, and Mossbauer spectroscopy measurements. The compounds exhibited SCO behavior with thermal hysteresis loop (T-1/2 up arrow = 202K, T-1/2 down arrow = 194K for 1 and T-1/2 up arrow = 304 K, T-1/2 down arrow = 194 K for 2). Moreover, the light-induced excited spin-state trapping (LIESST) effect was observed for the compounds when the samples were illuminated (1000 am) at 5K. We suggest that the introduction of a strong intermolecular interaction, such as pi-pi stacking, can play an important role in the observed dynamic phase transition.