Photoluminescence of tris(2,2′-bipyridine)ruthenium(II) ions intercalated in layered niobates and titanates: Effect of interlayer structure on host-guest and guest-guest interactions

Intercalation compounds of layered niobates and titanates with tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺, bpy = 2,2′-bipyridine) ions were synthesized and their photoluminescent behavior was investigated. K₄Nb₆O₁₇, HTiNbO₅, and H₂Ti₄O₉ were used as the host. Ru(bpy)₃²⁺ ions were intercalated by displacement of pre-intercalated alkylammonium ions or direct reaction and were densely present in the interlayer spaces. Luminescence lifetimes of the intercalated Ru(bpy)₃²⁺ ions showed concentration quenching of the emission. The guest displacement technique yielded some intercalation compounds where alkylammonium ions were co-intercalated with Ru(bpy)₃²⁺ ions, and the co-intercalated photoinactive ions suppressed the concentration quenching to some extent. Ru(bpy)₃²⁺ ions were distorted and in close contact with the host lattices in the interlayer spaces of the samples whose interlayer spacing was small. Luminescence decay of these intercalation compounds was fast, suggesting that the emission of the intercalated Ru(bpy)₃²⁺ ions was quenched by the host lattices.