Naito T, Karasudani T, Ohara K, Takano T, Takahashi Y, Inabe T, Furukawa K, Nakamura T.
Adv Mater. 2012 Dec 4;24(46):6153-7.
Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama 790-8577, Japan. [email protected]
An organic insulating crystal reversibly becomes a magnetic conductor under UV irradiation. The rapid and qualitative change in the physical properties is wavelength selective and explained by charge transfer between donor and photochemically active acceptor molecules. The photochemical redox reaction in the crystal produces a partially filled band and localized spins simultaneously.
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Attempting to develop photosensitive molecular magnetic conductors, we examined the physical properties of a charge-transfer salt between a nickel-dithiolene complex (Molecule A) and methyl viologen (Molecule B). Even though the compound has many features in common with ordinary molecular insulating crystals, we have found that it possesses metallic properties under UV irradiation with localized spins. In addition, the calculated band structure indicates an unprecedented narrow band width under dark, which is a similar feature with the High-TC superconductors before doping. This band structure is consistent with or supported by the electrical conductivity, magnetic susceptibility and electron spin resonance measurements. UV irradiation corresponds to simultaneous “carrier and local spin doping” in this material, and it behaves like a Kondo system under UV irradiation. Thus the compound is a common diamagnetic insulator under dark, however, under irradiation it becomes a rare example of a molecular counterpart of naturally occurring transition metallic elements.