Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (10): 2215-2220.doi: 10.3866/PKU.WHXB201308141

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Nonlinear Optical Properties:Second Harmonic Generation for Aromatic Amino Acids

WEI Jing, CHENG Wen-Dan   

  1. Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China; University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2013-04-26 Revised:2013-08-05 Published:2013-09-26
  • Contact: CHENG Wen-Dan E-mail:cwd@fjirsm.ac.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21173225, 21101156) and Foundation of Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, China.

Abstract:

The geometrical structures of a series of neutral, protonated, and deprotonated aromatic amino acids (Phe, [Phe―H]-, PheH+, Tyr, [Tyr―H]-, TyrH+, Trp, [Trp―H]-, and TrpH+) were optimized using density functional theory (DFT)-B3LYP with a 6-31G* basis set. Based on the optimized structures, the excited state properties were studied using time-dependent DFT at the B3LYP/6-31G* level. We calculated the second-order polarizabilities for second harmonic generation with the sum-over-states method. We examined the origins of the nonlinear optical responses and determined the cause for the variation in the second-order polarizabilities. Our calculations show that the second-order polarizabilities for protonated, and deprotonated aromatic amino acids are much higher than those for the neutral aromatic amino acids, with the order Phe < PheH+ < [Phe―H]- and Tyr < TyrH+ < [Tyr―H]-. By analyzing their electronic origins, we find that charge transitions in the side chains (benzene, phenol, and indole) make the main contributions to the second-order polarizability for neutral aromatic amino acids. For protonated and deprotonated aromatic amino acids, π→π* charge transfers within indole rings, and charge transfers within amino groups and the carboxyl groups attached to alpha-carbon atoms make almost identical contributions to the second-order polarizability.

Key words: Aromatic amino acid, Second-order polarizability, Protonated and deprotonated molecules, Density functional theory, Sum-over-states method

MSC2000: 

  • O641