This study entails two parts: The first reports on the synthesis of a novel N-(2,4-dinitrobenzylidene)-3-chlorobenzenamine Schiff base and its analysis by ultraviolet–visible (UV–vis) spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy. The UV–vis measurements showed absorption between 264 and 304 nm. The experimental optical gap energy was obtained using the Tauc method, and was estimated to be around 3.1 eV. On the other hand, we calculated optical gap energy using the M06-2X level, which gave a value of 3.20 eV, proving to be very close to the experimental one. The second part of this study focused on the dipole moment, dynamic linear and dynamic nonlinear optical (NLO) properties of this new compound. Theoretical calculations using density functional theory (DFT) were used to optimize the geometry, and to calculate this compound's dynamic polarizability and dynamic first-order hyperpolarizability. For the polarizability, we studied the mean polarizability \( \left\langle \alpha \right\rangle \) and the polarizability anisotropy \(\Delta \alpha\). To elucidate the correlation between the molecular architecture of this Schiff base and the dynamic first hyperpolarizability, the dynamic behavior of the hyper-Rayleigh scattering (HRS) first hyperpolarizability \(\beta _{{{\text{HRS}}}}\), the dynamic electric field-induced second harmonic generation (EFISHG) \(\beta _{{//}}\), and the depolarization ratios (DR) were calculated and analyzed in detail. Moreover, a correlation of \(\beta _{{{\text{HRS}}}}\) with the optical band gap and between the \(\beta _{{{\text{HRS}}}}\) and \(\beta _{{//}}\) was found. Based on these results, we can conclude that the synthesized Schiff base is a good candidate for the design of organic NLO materials.

Graphic Abstract

中文翻译：

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新型 N-(2,4-二硝基亚苄基)-3-氯苯胺席夫碱的合成、表征、线性和 NLO 特性：结合实验和 DFT 计算

本研究包括两部分：关于新型 N-(2,4-二硝基亚苄基)-3-氯苯胺席夫碱的合成及其紫外-可见 (UV-vis) 光谱分析、¹ H 和¹³C 核磁共振 (NMR) 和红外 (IR) 光谱。UV-vis 测量显示在 264 和 304 nm 之间有吸收。使用 Tauc 方法获得实验光学间隙能量，估计约为 3.1 eV。另一方面，我们使用 M06-2X 能级计算了光学间隙能量，其值为 3.20 eV，证明与实验值非常接近。本研究的第二部分侧重于这种新化合物的偶极矩、动态线性和动态非线性光学 (NLO) 特性。使用密度泛函理论 (DFT) 的理论计算用于优化几何形状，并计算该化合物的动态极化率和动态一阶超极化率。对于极化率，我们研究了平均极化率\( \left\langle \alpha \right\rangle \)和极化率各向异性\(\Delta \alpha\)。为了阐明该席夫碱的分子结构与动态第一超极化率之间的相关性，超瑞利散射 (HRS) 第一超极化率的动态行为\(\beta _{{{\text{HRS}}}}\)、动态电场引起的二次谐波产生 (EFISHG) \(\beta _{{//}}\)和去极化率 ( DR ) 进行了详细计算和分析。此外，\(\beta _{{{\text{HRS}}}}\)与光学带隙的相关性以及\(\beta _{{{\text{HRS}}}}\)和\(\beta _{{//}}\)被找到。基于这些结果，我们可以得出结论，合成的席夫碱是设计有机 NLO 材料的良好候选者。

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