Spin-Singlet Transition in the Magnetic Hybrid Compound from a Spin-Crossover Fe(III) Cation and pi-Radical Anion

摘要

To develop a new spin-crossover functional material, a magnetic hybrid compound [Fe(qsal)(2)][Ni(mnt)(2)] was designed and synthesized (Hqsal = N-(8-quinolyl)salicylaldimine, mnt = maleonitriledithiolate). The temperature dependence of magnetic susceptibility suggested the coexistence of the high-spin (HS) Fe(III) cation and pi-radical anion at room temperature and a magnetic transition below 100 K. The thermal variation of crystal structures revealed that strong pi-stacking interaction between the pi-ligand in the [Fe(qsal)(2)] cation and [Ni(mnt)(2)] anion induced the distortion of an Fe(III) coordination structure and the suppression of a dimerization of the [Ni(mnt)(2)] anion. Transfer integral calculations indicated that the magnetic transition below 100 K originated from a spin-singlet formation transformation in the [Ni(mnt)(2)] dimer. The magnetic relaxation of Mossbauer spectra and large thermal variation of a g-value in electron paramagnetic resonance spectra below the magnetic transition temperature implied the existence of a magnetic correlation between d-spin and pi-spin.