A Hybrid DFT Study on the Mechanism of the Electron Conductivity of Molecular Devices Composed of Metal and Carbonyl Compounds

Abstract

Density functional theory (DFT) calculation at the B3LYP/6-311++G(d,p) level has been applied to one of the high-performance molecular devices, magnesium–naphthalene tetracarboxylic dianhydlide (NTCDA) complex expressed by Mg₄NTCDA. The electronic state of the complex at the ground state is consisted of a slight ion-pair state expressed by (Mg₄)^δ+(NTCDA)^δ−. The magnitude of the charge transfer (CT) is estimated to be {\rm \delta = 0.56e.} The first and second excitation energies of free NTCDA were calculated to be 3.40 and 3.42 eV, respectively. By the interaction of NTCDA with the Mg atom, a new energy band is generated at low energy region: the excitation energies of Mg₄NTCDA are calculated to be 0.17 and 1.37 eV, respectively. These bands are assigned to a CT band. The mechanism of the electron conductivity was discussed on the basis of theoretical results.

Keywords:

• Naphthalene tetracarboxylic dianhydlide
• Density functional theory
• Charge-transfer band
• Perylenetetracarboxylic dianhydride

Acknowledgements

The authors are indebted to the Computer Center at the Institute for Molecular Science (IMS) for the use of the computing facilities. One of the authors (H.T.) also acknowledges a partial support from a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science ( JSPS).