Cooperative high-temperature spin crossover accompanied by a highly anisotropic structural distortion

Il'ya A. Gural'skiy, Bohdan O. Golub, Sergii I. Shylin, Vadim Ksenofontov, Helena J. Shepherd, Paul R. Raithby, Wolfgang Tremel, Igor O. Fritsky

OAI: oai:purehost.bath.ac.uk:publications/8016cb60-fc56-4c42-80b8-078f845ab283 • DOI: https://doi.org/10.1002/ejic.201600406

Spin transitions are a spectacular example of molecular switching that can provoke extreme electronic and structural reorganizations in coordination compounds. A new 3D cyanoheterometallic framework, [Fe(pz)(Au(CN)₂)₂], has been synthesized in which a highly cooperative spin crossover has been observed at 367 and 349 K in heating and cooling modes, respectively. Mössbauer spectroscopy revealed a complete transition between the diamagnetic and paramagnetic states of the iron centres. The low-spin-to-high-spin transition induced a drastic structural distortion involving a large one-directional expansion (ca. 10.6%) and contraction (ca. 9.6%) of the lattice. Negative thermal expansion along the c axis was detected below and above the transition temperature.

Cooperative effects Iron magnetic properties metal-organic frameworks spin crossover