A series of novel polymeric compounds of formula [M(btzb)3][ClO4]2 (MII = Fe, Ni or Cu) with btzb = 1,4-bis(tetrazol-1-yl)butane have been prepared and their physical properties investigated. The btzb ligand has been prepared and its crystal structure determined, together with a tentative crystal structure of the 3-D compound [Fe(btzb)3][ClO4]2. The model of the latter shows two symmetry-related, interpenetrating Fe–btzb networks in which the iron(II) ions approach each other as close as 8.3 and 9.1 Å. This supramolecular catenane undergoes a sharp thermal spin transition around 160 K with hysteresis (20 K) along with a pronounced thermochromic effect. The spin crossover behaviour has been followed by magnetic, DSC, optical spectroscopy and 57Fe Mössbauer spectroscopy measurements. Irradiation with green light at low temperature leads to population of the metastable high-spin state for the thermally active iron(II) ions. The nature of the spin crossover behaviour has been discussed in detail.
Affiliations
University of Mainz (Germany)Inorganic and Analytical Chemistry
van Koningsbruggen, P. J., Garcia, Y., Kooijman, H., Spek, A. L., Haasnoot, J. G., Kahn, O., Linares, J., Codjovi, E., & Varret, F. (2001). A new 3-D polymeric spin transition compound : [tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′)iron(II)] bis(perchlorate). Journal of the Chemical Society. Dalton Transactions, 4, 466-471. https://doi.org/10.1039/b008073j (Original work published 2001)