Kiven Dinyuy Emmanuel, Nkungli Nyiang Kennet, Tasheh Stanley Numbonui, Ghogomu Julius Numbonui
Department of Chemistry, Faculty of Science, The University of Bamenda, P.O. Box 39, Bambili-Bamenda, Cameroon.
Department of Chemistry, Faculty of Science, University of Dschang, Research Unit of Noxious Chemistry and Environmental Engineering, P.O. Box 67, Dschang, Cameroon.
R Soc Open Sci. 2023 Jan 11;10(1):220430. doi: 10.1098/rsos.220430. eCollection 2023 Jan.
The nonlinear optical (NLO) properties of ethyl 4-[()-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB) and some of its derivatives are investigated herein using the density functional theory (DFT) and time-dependent (TD)-DFT methods. The density functionals B3LYP, CAM-B3LYP, M06-2X and B97XD, and basis sets 6-31 + G**, 6-311 + + G** and Def2-TZVPP have been used. From the results, EMAB and its substituted derivatives studied are promising candidates for NLO materials. In all cases, the static first and second hyperpolarizabilities (31.7-86.5 × 10 and 84.4-273 × 10 electrostatic units (esu), respectively) and the frequency-dependent NLO properties are found to be significantly larger (about 43-103 and 28-76 times greater) than those of the NLO prototypical molecule, -nitroaniline. Furthermore, the maximum absorption wavelengths of the molecules fall within the UV region of the electromagnetic spectrum. Relative to EMAB, the derivatives have shown improved transparency-nonlinearity trade-offs. Natural bond orbital (NBO) and density of states (DOS) analyses herein revealed effective charge transfer within the molecules studied, especially those with stronger electron donors than that in EMAB (methoxy group). Among the molecules studied, the derivative obtained by substituting EMAB's methoxy group with the pyrrolyl group was found to exhibit the best NLO properties. Conclusively, the NLO activities of EMAB can be significantly improved through the substitution of its methoxy group with stronger electron donors.
本文采用密度泛函理论（DFT）和含时（TD）-DFT方法研究了4-[（）-（2-羟基-4-甲氧基苯基）亚甲基氨基]苯甲酸乙酯（EMAB）及其一些衍生物的非线性光学（NLO）性质。使用了密度泛函B3LYP、CAM-B3LYP、M06-2X和B97XD以及基组6-31 + G**、6-311 + + G**和Def2-TZVPP。结果表明，所研究的EMAB及其取代衍生物是有前途的NLO材料候选物。在所有情况下，发现静态第一和第二超极化率（分别为31.7 - 86.5×10和84.4 - 273×10静电单位（esu））以及频率相关的NLO性质比NLO原型分子对硝基苯胺的相应性质显著更大（分别约大43 - 103倍和28 - 76倍）。此外，这些分子的最大吸收波长落在电磁光谱的紫外区域。相对于EMAB，衍生物表现出更好的透明度 - 非线性权衡。本文的自然键轨道（NBO）和态密度（DOS）分析揭示了所研究分子内的有效电荷转移，特别是那些具有比EMAB中更强电子供体（甲氧基）的分子。在所研究的分子中，发现用吡咯基取代EMAB的甲氧基得到的衍生物表现出最佳的NLO性质。总之，通过用更强的电子供体取代EMAB的甲氧基，可以显著提高其NLO活性。
