A 2D [Fe-II-bistetrazole] coordination polymer exhibiting spin-crossover properties

The reaction of 1,3-bis(tetrazol-1-yl)-2-propanol (btzpol) with Fe(BF4)(2) center dot 6H(2)O in acetonitrile yields the remarkable 2D coordination polymer [Fe-II(btzpol)(1.8)(btzpol-OBF3)(1.2)](BF4)(0.8) center dot (H2O)(0.8)(CH3CN) (1). This compound has been structurally characterized using an X-ray single-crystal synchrotron radiation source. The iron(11) centers are bridged by means of double btzpol bridges along the c direction, and by single btzpol bridges along the b direction. The reaction of part of the ligand with the counterion has forced the compound to crystallize in this extended two dimensional structure. The compound shows spin-transition properties, both induced by temperature and light, with T-1/2 = 112 K and T(LIESST) = 46 K, respectively. The relaxation of the metastable high-spin state created by irradiation is exponential, following an Arrhenius type behavior at high temperature, and dominated by a temperature independent tunneling process at lower temperatures. (c) 2006 Elsevier B.V. All rights reserved.