Fluorescence spectra of Fe(II) spin crossover complexes with 2,6-bis(benzimidazole-2′-yl)pyridine Original Research Article

Temperature dependent fluorescence, excitation and absorption spectra of two spin crossover Fe(II) complexes with 2,6-bis(benzimidazole-2′-yl) pyridine, Febz-H2 (containing 2(ClO4−) as counter ions) and Febz-H (uncharged), have been observed. The origin of the unexpected observed fluorescence is discussed. Polarized absorption spectra in stretched polymer films are described and aid to the interpretation as well as extended PPP–MO calculations. The observed fluorescence spectra are not only the assignment of electronic transitions but also shown to be useful for the extraction of high-spin (HS) and low-spin (LS) contents in temperature dependent spin crossover systems.