Nonplanar Donor–Acceptor Chiral Molecules with Large Second-Order Optical Nonlinearities: 1,1,4,4-Tetracyanobuta-1,3-diene Derivatives

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• 作者：Yanling Si ; Guochun Yang
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：February 13, 2014
• 年：2014
• 卷：118
• 期：6
• 页码：1094-1102
• 全文大小：448K
• ISSN：1520-5215

文摘

We have investigated the chiroptical, linear, and second-order nonlinear optical (NLO) properties of five 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivatives and elucidated structure鈥損roperty relationships from the micromechanism. The experimental UV鈥搗is absorption and circular dichroism (CD) spectra were well reproduced by our calculations at TDB3LYP/6-31+G* level of theory. The electron transition property and chiroptical origin have been assigned and analyzed. The results show that the studied compounds possess large molecular first hyperpolarizabilities, especially for compound 5 which has a value of 35 脳 10^鈥?0 esu, which is comparable with the measured value for highly 蟺-delocalized phenyliminomethyl ferrocene complex and about 200 times larger than the average first hyperpolarizability of the organic urea molecule. Despite the nonplanarity of these compounds, efficient intramolecular charge transfer (CT) from electron donor to electron acceptor moieties was observed, which plays the key role in determining the NLO response. The intramolecular charge transfer cooperativity was also probed. In view of the first hyperpolarizability values, intrinsic noncentrosymmetric electronic structure, and high stability, the studied compounds have the possibility to be excellent second-order NLO materials.