π-Conjugation Engineering in New Ladder-Type Pyrazinoquinoxaline-Based Chromophores: A Route to High-Performance NLO Materials With Ultradeep HOMO Levels

IF 2 3区 化学 Q3 CHEMISTRY, PHYSICAL
Hejing Sun
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引用次数: 0

Abstract

In this study, a series of novel chromophores featuring pyrazinoquinoxaline (PQ)-type variant conjugated bridges and powerful push-pull effects was designed and systematically investigated. These PQ chromophores possess unique ladder-type D-πD-A, D-πAD-A, and D-πA-A configurations, first proposed and explored in the nonlinear optical (NLO) field. A comprehensive investigation of core properties, including aromaticity, static hyperpolarizability, dipole moments, excited-state properties, stability, 2D second-order nonlinear response spectra, and structure–property relationships was conducted through multiple advanced analytical methodologies. The structure of PQ conjugated bridges, acceptor strength, and dielectric surrounding were found to exert significant impacts on the hyperpolarizabilities and dipole moments of new PQ chromophores. Intriguingly, in contrast to traditional polyene-bridged chromophores, PQ-type systems exhibit a V-shaped hyperpolarizability curve with increasing pyrazine rings on the conjugated bridge, accompanied by enhanced transition dipole moment squared, elevated polarity, a sharp decline in HOMO energy levels, and diminished aromaticity. The crucial states governing hyperpolarizability in PQ-type chromophores are S3 or S4 state. The number of pyrazine rings on the PQ-type bridge determines the key factors influencing hyperpolarizability. DN-PQ0-AS1 and DN-PQ6-AS1 exhibit remarkable hyperpolarizabilities and dipole moments in chloroform and acetonitrile, resulting in outstanding molecular hyperpolarizabilities. Significantly, DN-PQ6-AS1 and DN-PQ5-AS1 exhibit ultra-deep HOMO energy levels of −8.26 eV and −8.16 eV respectively, indicating that these chromophores possess exceptional oxidation resistance, chemical stability, and air stability. This directly solves the urgent problem of insufficient stability in the processing and polarization of NLO materials. The unique D-πAD-A, D-πD-A, and D-πA-A configurations in this system contain donor-acceptor pairs with various lengths and strengths, resulting in multilevel and multiscale characteristics of electronic transitions and charge transfers. These structural features critically influence hyperpolarizability density and 2D NLO responses. Several PQ chromophores exhibit excellent EOPE/OR performance (exceeding 1 × 10−22 esu). Notably, DN-PQ4-AS1 shows exceptional SHG response values (1.902 × 10−23 esu). This mechanistic understanding of novel PQ conjugate systems provides innovative design strategies for developing multifunctional high-performance NLO materials.

Abstract Image

新型阶梯型吡嗪喹啉基发色团的π共轭工程:一条获得超深HOMO能级高性能NLO材料的途径
本研究设计了一系列具有吡嗪喹啉(pyrazinoquinoxaline, PQ)型变异共轭桥和强推拉效应的新型发色团,并对其进行了系统研究。这些PQ发色团具有独特的阶梯型D-π - D- a、D-π - a -π - a和D-π - a构型,首次在非线性光学(NLO)领域被提出和探索。通过多种先进的分析方法,对核心性质进行了全面的研究,包括芳香性、静态超极化性、偶极矩、激发态性质、稳定性、二维二阶非线性响应谱和结构-性质关系。发现PQ共轭桥结构、受体强度和介电环境对新PQ发色团的超极化率和偶极矩有显著影响。有趣的是,与传统的多烯桥接发色团相比,pq型体系呈现出v型超极化曲线,共轭桥上的吡嘧啶环增加,过渡偶极矩平方增强,极性升高,HOMO能级急剧下降,芳香性减弱。控制pq型发色团超极化率的关键态是S3或S4态。pq型桥上的吡嗪环数决定了影响超极化率的关键因素。DN-PQ0-AS1和DN-PQ6-AS1在氯仿和乙腈中表现出显著的超极化性和偶极矩,导致分子具有显著的超极化性。值得注意的是,DN-PQ6-AS1和DN-PQ5-AS1分别表现出−8.26 eV和−8.16 eV的超深HOMO能级,表明这些发色团具有优异的抗氧化性、化学稳定性和空气稳定性。这直接解决了NLO材料在加工和极化过程中稳定性不足的迫切问题。该体系独特的D-πA-πD-A、D-πD-A和D-π -a构型包含了不同长度和强度的供体-受体对,从而产生了电子跃迁和电荷转移的多能级、多尺度特征。这些结构特征严重影响超极化密度和二维NLO响应。几种PQ发色团表现出优异的EOPE/OR性能(超过1 × 10−22 esu)。值得注意的是,DN-PQ4-AS1显示出异常的SHG响应值(1.902 × 10−23 esu)。这种对新型PQ共轭系统的机理理解为开发多功能高性能NLO材料提供了创新的设计策略。
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来源期刊
International Journal of Quantum Chemistry
International Journal of Quantum Chemistry 化学-数学跨学科应用
CiteScore
4.70
自引率
4.50%
发文量
185
审稿时长
2 months
期刊介绍: Since its first formulation quantum chemistry has provided the conceptual and terminological framework necessary to understand atoms, molecules and the condensed matter. Over the past decades synergistic advances in the methodological developments, software and hardware have transformed quantum chemistry in a truly interdisciplinary science that has expanded beyond its traditional core of molecular sciences to fields as diverse as chemistry and catalysis, biophysics, nanotechnology and material science.
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