Nuclear inelastic scattering of 1D polymeric Fe(II) complexes of 1,2,4-aminotriazole in their high-spin and low-spin state

The vibrational properties of Fe(II) 1D spin crossover polymers have been characterized by nuclear inelastic scattering (NIS). The complexes under study were the tosylate and perchlorate salts of ([Fe(4-amino-1,2,4-triazole)(3)](+2))(n) complexes. The complexes have LS (S = 0) marker bands in the range of 300-500 cm(-1), while the marker bands corresponding to the HS (S = 2) state are detected between 200 cm(-1) and 300 cm(-1), in line with the decreasing Fe-N bond strengths during the transition from LS to HS. Accompanying DFT calculations using the functional B3LYP and the basis set CEP-31G confirm these assignments.