Nouvelle publication de l’équipe CIEl : « One-dimensional Thiocyanato-Bridged Fe(II) Spin Crossover Cooperative Polymer With Unusual FeN5S Coordination Sphere. »
Nebbali K., Mekuimemba C. D., Charles C., Yefsah S., Chastanet G., Mota A. J., Colacio E., Triki S.
Inorg. Chem. 2018, 57, 12338-12346 – DOI : 10.1021/acs.inorgchem.8b02061
We present here a novel example of spin crossover phenomenon on a Fe(II) one-dimensional chain with unusual N5S coordination sphere. The [{Fe(tpc-OMe)(NCS)(μ-NCS)}n] (1) compound was prepared using the tridentate tpc-OMe ligand (tpc-OMe = tris(2-pyridyl)methoxymethane), FeCl2.4H2O and the KSCN salt. Crystallographic investigations revealed that the Fe(II) ions are connected by a single bridging NCS- ligand (m-kN:kS-SCN coordination mode) to afford a zig-zag neutral chain running along the [010] direction, in which the thiocyanato bridging groups adopt a cis head-to-tail configuration. The (N5S) metal environment arises from one kS-SCN and two kN-NCS ligands, and from three pyridine of the fac-tpc-OMe tripodal ligand. This compound presents a unique extension of Fe(II) binuclear complexes into linear chains built on similar tripodal ligands and bridging thiocyanate anions. Compound 1 shows a spin crossover (SCO) behavior which has been evidenced by magnetic, calorimetric and structural investigations, revealing a shrarp cooperative spin transition with a transition temperature of ca. 199 K. Temperature scan rate studies revealed a very narrow hysteresis loop (~1K wide). Photoswitching of this compound was also performed, evidencing a very fast relaxation process at low temperature. Among other factors, the linearity of the N-bound terminal thiocyanato ligand appears as the main structural characteristic at the origin of the presence of the SCO transition in compound 1 and in the two others Fe(II) previous systems involving thiocyanato-bridges.