High-tech electronic, optics, and storage devices require organic compounds with nonlinear optical (NLO) properties. This study designed D-π-A based dyes with donor triphenylamine (TPA) and acceptor dicyanovinylene (DCV) species by structurally modifying π-conjugated linkers. Our density functional theory (DFT) computations analyzed the impact of structural variations on the nonlinear optical (NLO) response of newly designed dyes. The B3LYP/6-31G(d,p) level determined the quantic chemical insights: frontier molecular orbital (FMOs), natural bond orbitals (NBOs) and nonlinear optical (NLO) properties of the designed dyes (DPTM-1 to DPTM-12). UV-Vis analysis based on the TD-DFT/CAM-B3LYP/6-311+G(d,p) level explored the optoelectronic properties. DPTM-1 and DPTM-5 showed the highest red-shifted absorption band at 519 and 506 nm. NBO analysis shows that DPTM-1 to DPTM-12 dyes have positive values for all donors (D) and π-spacers but negative values for acceptors (A). The π-spacers act as a conveyer between donor and acceptor moieties; thus, electrons were transferred smoothly from D to A units, which resulted in a charge separation state. Our calculations show the extent of NLO response in terms of electronic transitions, polarizability and first hyperpolarizability (β) values. The highest value of βtotal was 110509.23 a.u. manifested in DPTM-6 due to 2,5-dimethyloxazole as a 2nd-π-linker, twice that of R (66275.95 a.u.). Also, DPTM-6 and DPTM-8 exhibit the lowest energy band gap of 2.06 and 2.04 eV, respectively. In short, all DPTM-1 to DPTM-12 dyes manifested maximum absorption, lowest energy band gap, greater charge transfer from donor to the acceptor and better first hyperpolarizability values as compared to the R and showed good NLO response. The present work represents new compounds with remarkable NLO properties and their applications in modern high-tech devices.

中文翻译：

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π-共轭连接体修饰三苯胺-二氰基亚乙烯基共存供体-π-受体结构的非线性光学性质探索

高科技电子、光学和存储设备需要具有非线性光学 (NLO) 特性的有机化合物。本研究通过对 π 共轭接头进行结构修饰，设计了具有供体三苯胺 (TPA) 和受体二氰亚乙烯基 (DCV) 物质的 D-π-A 染料。我们的密度泛函理论 (DFT) 计算分析了结构变化对新设计染料的非线性光学 (NLO) 响应的影响。B3LYP/6-31G(d,p) 水平确定了量子化学见解：设计染料（DPTM-1 到 DPTM-12）的前沿分子轨道 (FMO)、自然键轨道 (NBO) 和非线性光学 (NLO) 特性）。基于 TD-DFT/CAM-B3LYP/6-311+G(d,p) 水平的 UV-Vis 分析探索了光电特性。DPTM-1 和 DPTM-5 在 519 和 506 nm 处显示出最高的红移吸收带。NBO 分析表明，DPTM-1 到 DPTM-12 染料对所有供体 (D) 和 π-间隔基都具有正值，但对受体 (A) 具有负值。π-间隔区充当供体和受体部分之间的传送器；因此，电子从 D 单元顺利转移到 A 单元，导致电荷分离状态。我们的计算显示了 NLO 响应在电子跃迁、极化率和第一超极化率 (β) 值方面的程度。由于 2,5-二甲基恶唑作为 2nd-π-接头，βtotal 的最高值为 110509.23 au，是 R (66275.95 au) 的两倍。此外，DPTM-6 和 DPTM-8 的最低能带隙分别为 2.06 和 2.04 eV。总之，所有 DPTM-1 到 DPTM-12 染料都表现出最大吸收、最低能带隙、与 R 相比，从供体到受体的更多电荷转移和更好的第一超极化值，并显示出良好的 NLO 响应。目前的工作代表了具有显着 NLO 特性的新化合物及其在现代高科技设备中的应用。