Structural, Optical, and Electrical Properties of One-Dimensional Bis(Dimethylglyoximato)nickel(II), Ni(dmg)2 at High Pressure

• Published in: Molecular crystals and liquid crystals (Philadelphia, Pa. : 2003) Pa. : 2003), 2006-12, Vol.460 (1), p.131-144
• Main Authors: Takeda, K., Hayashi, J., Shirotani, I., Fukuda, H., Yakushi, K.
• Format: Article
• Language: English
• Subjects: bis(dimethylglyoximato)nickel(II); electrical and optical properties; high pressure; synchrotron radiation; X-ray diffraction
• ISSN: 1542-1406; 1563-5287
• DOI: 10.1080/15421400600598412

By use of synchrotron radiation, powder X-ray diffraction of one-dimensional bis(dimethylglyoximato)nickel(II), Ni(dmg) 2 , has been studied at room temperature and at high pressure. The lattice constants with an orthorhombic structure for Ni(dmg) 2 monotonically decrease with increasing pressure up to 7.4 GPa; the linear compressibility of each axis is estimated. The magnitude of the linear compressibility increases in the order c > b > a in the low-pressure region. However, the lattice constant along the b-axis is smaller than that along the a-axis at pressures greater than 6 GPa. A Ni-Ni distance along the c-axis abruptly decreases from 3.255 Å at ambient pressure to 2.82 Å at 7.4 GPa. A bulk modulus of Ni(dmg) 2 is obtained from the volume versus pressure curve fitted by a Birch equation of state. The bulk modulus of this complex is very small, 8.0 GPa. Ni(dmg) 2 is a very compressible compound. The electrical and optical properties of Ni(dmg) 2 have been investigated at high pressures. The dπ-π* and 3d-4p bands shift to a lower energy region with increasing pressure. The absorption peak of the 3d-4p band is very sensitive to pressure. The resistivity of Ni(dmg) 2 decreases monotonically with increasing pressure up to 23 GPa. The lowest resistivity of this complex is about 50 Ω cm at around 23 GPa. These electrical and optical properties are closely related to the rapid shrinkage of the Ni-Ni distance with increasing pressure.