Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (01): 120-124.doi: 10.3866/PKU.WHXB20091220


DFT Study on the Nonlinear Optical Properties of Bisimidazole and Bistriazole Benzenes and Their Derivatives

LIU Hai-Bo, QIU Yong-Qing, SUN Shi-Ling, SUN Xiao-Na, SU Zhong-Min   

  1. Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, P. R. China
  • Received:2009-06-22 Revised:2009-08-22 Published:2009-12-29
  • Contact: QIU Yong-Qing


The UB3LYP(B3LYP)/6-31+G** method of density functional theory (DFT) was employed to optimize the geometrical structures of bisimidazole and bistriazole benzenes and their derivatives. In addition, the nonlinear optical (NLO) coefficients of these systems were calculated with a finite field (FF) approach. Results show that the polarizability α and second hyperpolarizability γ values of all systems increase by introducing a donor NH2 or an acceptor NO2. For the diradical systems, the α and γ values of these systems with a donor are larger than those with an acceptor, which is opposite to the behavior of closed shell systems. By analyzing the effect of the diradical character and charge on the second hyperpolarizability, we demonstrate that the neutral molecule with intermediate diradical character exhibits a much larger γ value than the neutral closed shell molecule with a similar π conjugation property. The charged diradical systems with a donor and an acceptor exhibited larger γ values compared to the neutral diradical systems.

Key words: Diradical, Nonlinear optical coefficient, Radical character, Density functional theory


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