A stable 1 : 1 : 1 inclusion complex of Ru(bpy)3-phenol (1), MV2+ and cucurbit[8]uril (CB[8]) is formed in aqueous solution. In the presence of triethanolamine (TEOA), a light-induced formation of unusual partner radical trimer 1–(MV+˙)2–CB[8] has been observed for the first time.