Supramolecular aggregation of yttrium thiocyanate with 4,4′-bipyridine

Abstract

The reaction of yttrium thiocyanate [Y(H₂O)₅(NCS)₃]·H₂O with 4,4′-bipyridine (bpy) was studied in various solvents. The complexes [Y(H₂O)₃EtOH(bpy)(NCS)₃]·bpy (1), {(μ-bpy)[Y(H₂O)₃(NCS)₃]₂}·3bpy·2(i-PrOH) (2), and [Hbpy]₂{(μ-bpy)[Y(H₂O)₃(NCS)₄]₂}·bpy (3) were isolated as the main phases (the former from ethanol, and the latter two from i-PrOH). Complex 3 formed also in MeCN and THF. Assemblies 1–3 were identified based on single-crystal and powder X-ray diffraction and IR spectroscopic data. Supramolecular aggregation in 1–3 occurs through OH⋯N(S) hydrogen bonds. Despite different compositions and arrangement of structural units, the crystal structures 1–3 are similar and consist of interpenetrating rectangular 3D networks. Thermal analysis showed that the decomposition of 1–3 occurs in a similar way. Coordinated water and alcohol molecules are eliminated at temperatures below 170 °C; at temperatures above 230 °C, the multistep elimination of bpy and decomposition of NCS take place. Photoluminescent characteristics of 1–3 provide evidence that bpy is involved in the energy transfer resulting in a long-wavelength shift of emission maxima.