A ruthenium complex containing a 1,9,10-anthyridine derivative, [Ru(L)(bpy)(2)](PF6)(2) ( [1] (PF6)(2); L = 1,13,14-triazadibenz[a,j]anthracene, bpy = 2,2'-bipyridyl), was synthesized. X-ray crystal structural analysis of [1](PF6)2 showed that L is coordinated to the Ru center as a bidentate ligand. When [1](PF6)(2) was dissolved in acetonitrile, a new complex incorporating one acetonitrile molecule, [Ru(L)(CH3CN)(bpy)(2)](PF6)(2) ([2] (PF6)(2)), was formed. X-ray crystallographic data revealed that, in [2](PF6)(2), L is coordinated to the Ru center in a monodentate fashion. The coordinated L in [2](PF6)(2) shows a unique haptotropic rearrangement in an acetonitrile solution.