Intercalation of 3X-pyridine with X = F, Cl, Br, I, in 2D ferrous nitroprusside. Thermal induced spin transition in Fe(3F-pyridine)2[Fe(CN)5NO]

• Published in: Journal of solid state chemistry Vol. 286; p. 121293
• Main Authors: Avila, Y., Crespo, P.M., Plasencia, Y., Mojica, H.R., Rodríguez-Hernández, J., Reguera, E.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.06.2020
• Subjects: Intercalation compounds; Layered ferrous nitroprusside; Spin crossover behavior; Thermal induced spin transition; Spin crossover behavior; Intercalation compounds; Thermal induced spin transition; Layered ferrous nitroprusside
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2020.121293

The series of 2D solids, Fe(3XPy)2[Fe(CN)5NO] with 3X ​= ​3-Fluoro, 3-Chloro, 3-Bromo, 3-Iodo and Py ​= ​Pyridine, was obtained by intercalation of the organic molecule (3XPy) between neighboring layers of 2D ferrous nitroprusside. The organic ligand was found coordinated to the axial positions for the iron atom linked at the equatorial N ends of the CN groups in the nitroprusside building block, [Fe(CN)5NO]. The axial CN and NO ligands remain unlinked and contribute to the solid stability through attractive dipole-dipole interactions. The formed hybrid solids preserve the 2D nature because no chemical bond is established between neighboring organic molecules in the interlayer region. For X ​= ​F, a thermal induced spin transition was observed, but not for the remaining derivatives. The nature of such behavior is discussed according to the recorded XRD, Raman and Mössbauer data and computational calculations. The spin crossover transition in Fe(3FPy)2[Fe(CN)5NO] is an incomplete process, a sample fraction of about 50% remains in paramagnetic state, even at 5 ​K. The spin transition is accompanied of an atypical small structural change, corresponding to a variation of 0.7% for the unit cell volume. Such behavior finds explanation in both, the bonding properties of the N end of the CN ligands in the nitroprusside pseudo-octahedral block, and in the intermolecular interactions in the interlayer region. Thermal induced spin crossover behavior for Fe(3F-pyridine)2[Fe(CN)5NO]. Such behavior was not observed for the analogues of Cl, Br, I, which was ascribed to the involved intermolecular interactions in the interlayer region. [Display omitted] •Thermal induced spin transition in a series of hybrid inorganic-organic 2D solids.•Intercalation of organic molecules in layered transition metal nitroprussides.•Spin crossover transition in 2D ferrous nitroprusside.•Effect of the intermolecular interactions on the spin crossover transition.•A combined Mössbauer, Raman, DSC and magnetic study of spin crossover transition.