The miscibility and phase behavior of the mixed monolayer of Ru(dpphen)(3)(2+) (dpphen=4,7-diphenyl-1,10-phenanthroline) (abbreviated as Ru(II)), octadecyltrichlorosilane (OTS) and stearic acid (SA) at air/water interface had been investigated in detail. Two-dimensional density of Ru(II) could be easily adjusted by changing the mixing ratio of Ru(II)/SA/OTS. The mixed monolayer of Ru(II)/SA/OTS with different molar proportions had been deposited and characterized by low angle X-ray diffraction, UV-visible absorption spectra and photo-induced emission spectra. The possible structure of its resulting LB film was proposed based on the results of the pi-A isotherms and low angle X-ray diffraction. Photo-induced electron transfer and self quenching of Ru(II) in mixed LB films had been investigated in detail. (C) 2003 Elsevier B.V. All rights reserved.