Co-crystallising two functional complex molecules in a terpyridine embrace lattice†
Abstract
Two series of solid solutions based on the [Fe(bpp)2][BF4]2 (bpp = 2,6-di(pyrazol-1-yl)pyridine) spin-crossover lattice are described. Materials of formula [FeyNi1−y(bpp)2][BF4]2 (0.95 ≥ x ≥ 0.15) are all phase-pure. In contrast, [Fe(bpp)2]x[Ru(terpy)2]1−x[BF4]2 (0.95 ≥ x ≥ 0.28) crystallise as a mixture of the neat [Fe(bpp)2][BF4]2 (space group P21) and [Ru(terpy)2][BF4]2 (Cc) phases as x approaches 0.5, although there is no evidence of segregation of the iron and ruthenium centres between the two. Spin-crossover in [FeyNi1−y(bpp)2][BF4]2 shows a normal variation in T½, ΔH, ΔS and lattice elasticity with decreasing y, for an isomorphously doped material. However, T½ in [Fe(bpp)2]x[Ru(terpy)2]1−x[BF4]2 shows an unusual dependence on x, which decreases slightly for 1.00 ≥ x ≥ 0.57 but increases as x is reduced further. We attribute this anomaly to the change in structure of the solid solutions, from predominantly the P21 lattice when x ≥ 0.47 to the Cc lattice when x = 0.28. The ruthenium centres in those compounds retain their low-temperature fluorescence, albeit with strongly reduced emission intensities. An unusual dependence of ΔH and ΔS for the spin transition in [Fe(bpp)2][BF4]2 on the crystallisation
- This article is part of the themed collection: Crystal engineering in molecular magnetism