A number of compounds including thiobarbituric acid derivative‐based acceptor unit and diverse donor moieties along with two types of π‐conjugated bridges have been constructed to aid in the design of the superior nonlinear optical (NLO) materials. The effect of varying the donor and bridge parts of this donor‐bridge‐acceptor system was analyzed in terms of structural and opto‐electronic parameters such as bond length alternation and ultraviolet‐visible absorption spectra. Various functionals with aug‐cc‐pVDZ basis set including B3LYP, PBE0, PBE38, BMK, CAM‐B3LYP, and ωB97XD were employed to calculate the static and dynamic first‐hyperpolarizabilities, and also the linear polarizabilities. Furthermore, the variation of the static first‐hyperpolarizabilities has been explained satisfactorily in the light of the sum‐over‐states method and two‐level model. The comprehensive study indicates that the coplanar compound D‐5 with the low electronic absorption energy, strongest oscillator strength paired with the largest ground, and excited state dipole moment difference generates a dramatical increase in its static and dynamic first‐hyperpolarizabilities, which would be the most worthwhile target for development as the NLO‐phores.

中文翻译：

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硫代巴比妥酸衍生物基供体-π-受体非线性光学基团的高第一超极化率：取代基和共轭桥效应的多种理论研究

已经构造了许多化合物，包括基于硫代巴比妥酸衍生物的受体单元和不同的供体部分，以及两种类型的π共轭桥，以帮助设计优异的非线性光学（NLO）材料。根据结构和光电参数，如键长交替和紫外可见吸收光谱，分析了改变该供体桥受体系统供体和桥部分的影响。使用具有aug-cc-pVDZ基础集的各种功能（包括B3LYP，PBE0，PBE38，BMK，CAM-B3LYP和ωB97XD）来计算静态和动态第一超极化率，以及线性极化率。此外，静态和超极化率的变化已根据求和状态法和两级模型得到了令人满意的解释。全面的研究表明，共平面化合物D-5具有低电子吸收能，最强的振荡器强度和最大的地面，并且激发态偶极矩差会极大地增加其静态和动态第一超极化率，这将是NLO-phores是最值得发展的目标。