Chiral effects at the metal center in Fe(III) spin crossover coordination salts.

Evidence of chirality was observed at the Fe metal center in Fe(III) spin crossover coordination salts [Fe(qsal)Ni(dmit)] and [Fe(qsal)(TCNQ)] from X-ray absorption spectroscopy at the Fe 2pcore threshold. Based on the circularly polarized X-ray absorption data, the X-ray natural circular dichroism seen [Fe(qsal)Ni(dmit)] and [Fe(qsal)(TCNQ)] is far stronger than seen for [Fe(qsal)Cl] suggesting this natural circular dichroism signature is a ligand effect rather than a result of just a loss of octahedral symmetry on the Fe core. The larger the chiral effects in the Fe 2p core to bound X-ray absorption, the greater the perturbation of the Fe 2pto 2pspin-orbit splitting seen in the X-ray absorption spectra.