Spin-Crossover and Liquid Crystal Properties in 2D Cyanide-Bridged FeII−MI/II Metalorganic Frameworks

Novel two-dimensional heterometallic Fe(II)−M(NiII, PdII, PtII, AgI, and AuI) cyanide-bridged metalorganic frameworks exhibiting spin-crossover and liquid crystal properties, formulated as {FeL2[MI/II(CN)x]ysH2O, where L are the ligands 4-(4-alkoxyphenyl)pyridine, 4-(3,4-dialkoxyphenyl)pyridine, and 4-(3,4,5-trisalkoxyphenyl)pyridine, have been synthesized and characterized. The physical characterization has been carried out by means of EXAFS, X-ray powder diffraction, magnetic susceptibility, differential scanning measurements, and Mössbauer spectroscopy. The 2D Fe(II) metallomesogens undergo incomplete and continuous thermally induced spin transition at T1/2 ≈ 170 K and crystal-to-smectic transition above 370 K.