Research on Multifunctional Properties Coupled with Photon and Spin for Transition-Metal Complexes

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Transition metal complexes with dィイD14ィエD1-dィイD17ィエD1 configuration have a possibility of spin transition between an low-spin state and a high spin state. Particularly, in the case of mixed-valence complexes whose spin states lie in the spin-crossover region, new types of conjugated phenomena due to spin and charge are expected. From this viewpoint, we have synthesized the mixed valence complex, [(n-CィイD23ィエD2HィイD27ィエD2)ィイD24ィエD2N][FeィイD1IIィエD1FeィイD1IIIィエD1(dto)ィイD23ィエD2](dto = CィイD22ィエD2OィイD22ィエD2SィイD22ィエD2), and have investigated the magnetic properties by means of magnetic susceptibility, magnetization, ESR and ィイD157ィエD1Fe Mossbauer spectroscopy. From the measurements of magnetic susceptibility and magnetization as a function of temperature, [(n-CィイD23ィエD2HィイD27ィエD2)ィイD24ィエD2N][FeィイD1IIィエD1FeィイD1IIIィエD1(dto)ィイD23ィエD2] was found to show the ferromagnetic transition at 6 K and to show the reversible charge transfer phase transition at about 120 K. Moreover, we have investigated the spin transition of [Fe(NHィイD22ィエD2trz)ィイD23ィエD2](RSOィイD23ィエD2)22HィイD22ィエD2O. In the case of [Fe(NHィイD22ィエD2trz)ィイD23ィエD2](CィイD2nィエD2HィイD22n+1ィエD2SOィイD23ィエD2)ィイD22ィエD22HィイD22ィエD2O(n=1-9), the transition temperature becomes higher by about 80 K with increasing the length of alkyl chain of the counter anion, and then it saturated at n > 5. The even-odd effect was observed in the hysteresis width.In the case of three-dimensional mixed-valence system CsィイD22ィエD2AuィイD22ィエD2XィイD26ィエD2, we have discovered a photo-induced Au valence transition for CsィイD22ィエD2AuィイD22ィエD2BrィイD26ィエD2 under high pressure.