Zouaoui-Rabah Mourad, Hedidi Madani, Elhorri Abdelkader M, Mahdjoub-Araibi Hicham
Department of Preparatory Education in Science and Technology, National Polytechnic School of Oran Maurice Audin, Oran El M'naouer, Box B.P. 1523, Oran, Algeria.
Laboratory of Materials Chemistry Catalysis and Reactivity, Department of Chemistry, Faculty of Exact Sciences and Informatics, Hassiba BenBouali University of Chlef, Ouled Fares, P.O. Box 78 C, 02180, Chlef, Algeria.
J Mol Model. 2025 Apr 29;31(5):149. doi: 10.1007/s00894-025-06370-3.
This study explores the impact of fluorine substitution on the structural, electronic, and nonlinear optical (NLO) properties of metallic complexes featuring the tetraamine lithium (TALi⁺) motif. Twelve complexes were designed by combining TALi⁺ with anions (Li⁻, Na⁻, K⁻), forming three categories (TALi-Li, TALi-Na, TALi-K), and analyzed using quantum chemical calculations. The results reveal exceptionally high static and dynamic first hyperpolarizabilities (∆β × 10 esu), with the largest gap (834.69 × 10⁻⁰ esu) observed in the (TALi-K) series. Dynamic (β) values reached (~ 60 million × 10 esu) at 1064 nm, while second hyperpolarizabilities (γₐ) followed similar trends, though (TALi-K) complexes exhibited deviations in ranking. Notably, push-pull behavior was identified, with anions acting as donors and fluorinated ammonias as acceptors, bridged by (NH₃ ligands). Absorption maxima (600-900 nm) in both vacuum and solvent environments suggest tunable optoelectronic responses. Crucially, the (TALi-K) category demonstrated the highest nonlinear refractive indices (n₂), highlighting its potential for photonic applications such as optical switching. This work provides a roadmap for designing high-performance NLO materials through strategic anion selection and fluorination, advancing the development of functional materials for light-based technologies.
All calculations were performed using Gaussian 16 software. Molecular geometries were optimized at the B3LYP-D3/6-31 + + G(d,p) level in the gas phase without symmetry constraints for a series of tetraamine lithium complexes with various alkali metals (TAL-M). Nonlinear optical properties were extensively characterized through first hyperpolarizability (β) calculations using seven different functionals (CAM-B3LYP, LC-wPBE, LC-BLYP, M11, wB97X, HSEh1PBE, and M06-2X) as well as MP2 theory, all with the 6-31 + + G(d,p) basis set. Additional basis set dependence studies were conducted using CAM-B3LYP with eight different basis sets ranging from 6-31G(d,p) to augmented triple-zeta sets. Second harmonic generation properties were evaluated through (β) and γ calculations at the CAM-B3LYP/6-31 + + G(d,p) level. Electronic delocalization was analyzed via NBO calculations (E(2) energies) using the same theoretical approaches. Solvent effects were incorporated using the SMD model for solvation free energies (ΔG) and the CPCM model for TD-DFT calculations of absorption maxima (λ) and oscillator strengths at the TD-CAM-B3LYP/6-31 + + G(d,p) level. This multi-method approach ensures robust characterization of both molecular structures and NLO properties.
本研究探讨了氟取代对具有四胺锂（TALi⁺）基序的金属配合物的结构、电子和非线性光学（NLO）性质的影响。通过将TALi⁺与阴离子（Li⁻、Na⁻、K⁻）结合设计了12种配合物，形成三类（TALi-Li、TALi-Na、TALi-K），并使用量子化学计算进行分析。结果显示出极高的静态和动态第一超极化率（∆β×10 esu），在（TALi-K）系列中观察到最大差距（834.69×10⁻³⁰ esu）。在1064 nm处动态（β）值达到（约6000万×10 esu），而第二超极化率（γₐ）遵循类似趋势，不过（TALi-K）配合物在排名上出现偏差。值得注意的是，确定了推挽行为，阴离子作为供体，氟化氨作为受体，由（NH₃配体）桥连。在真空和溶剂环境中的吸收最大值（600 - 900 nm）表明具有可调谐的光电响应。至关重要的是，（TALi-K）类别表现出最高的非线性折射率（n₂），突出了其在光开关等光子应用中的潜力。这项工作为通过策略性阴离子选择和氟化设计高性能NLO材料提供了路线图，推动了基于光的技术的功能材料的发展。
所有计算均使用高斯16软件进行。在气相中，对一系列含有各种碱金属的四胺锂配合物（TAL-M），在B3LYP-D3/6-31++G(d,p)水平下优化分子几何结构，无对称性限制。通过使用七种不同泛函（CAM-B3LYP、LC-wPBE、LC-BLYP、M11、wB97X、HSEh1PBE和M06-2X）以及MP2理论进行第一超极化率（β）计算，全面表征非线性光学性质，所有计算均使用6-31++G(d,p)基组。使用CAM-B3LYP和从6-31G(d,p)到增强三重ζ集的八种不同基组进行了额外的基组依赖性研究。通过在CAM-B3LYP/6-31++G(d,p)水平下的（β）和γ计算评估二次谐波产生性质。使用相同的理论方法通过NBO计算（E(2)能量）分析电子离域。使用SMD模型计算溶剂化自由能（∆G），并使用CPCM模型在TD-CAM-B3LYP/6-31++G(d,p)水平下进行吸收最大值（λ）和振子强度的TD-DFT计算，纳入溶剂效应。这种多方法方法确保了对分子结构和NLO性质的稳健表征。
