Luminescence Change by the Solvent of Crystallization, Solvent Reorganization, and Vapochromism of Neutral Dicyanoruthenium(II) Complex in the Solid State

The “solvent effect” on the solid-state luminescence of a neutral complex, [Ru(dbb)2(CN)2] (dbb = 4,4′-di-tert-butyl-2,2′-bipyridine), was presented. The crystals of this complex showed a variety of luminescence color from orange to dark-red, depending on the acceptor number of the solvent included in the crystal as a solvent of crystallization. The luminescence change was very similar to the solvatochromism in solution, which was attributed to the local donor−acceptor interaction between the CN group and the solvent molecules. The dynamic shift observed in the transient emission spectrum of the crystalline powder was accounted for by the solvent molecule reorganization. X-ray crystallography of [Ru(dbb)2(CN)2]·3(CH3)2CO showed the complex molecule having an approximate C2 symmetry and very weak interactions between the acetone molecules and the CN groups. A three-dimensional network constructed by acetone molecules was observed in the hydrophobic space consisting of t-butyl groups in dbb ligands. A thin film of the complex showed vapochromic behavior such that the luminescence changed depending on the solvent of crystallization. This suggests a capability for organic molecule discrimination using the complex in the solid state.