Effects of different directions and intensities of external electric fields on the dissociation and excitation characteristics of meta‑bromine-nitrobenzene and 5‑bromine-2-fluoro-nitrobenzene molecules

IF 2.4 3区化学 Q4 CHEMISTRY, PHYSICAL

Chemical Physics Pub Date : 2025-08-11 DOI:10.1016/j.chemphys.2025.112892

Chen Qin , Yi Li , Min Zhang , Jianxin Liu , Jinquan Chen

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Abstract

This study investigates the dissociation and excitation properties of meta-bromonitrobenzene (mBNB) and 5-bromo-2-fluoronitrobenzene (5Br2FNB) under different orientation (CBr or CN bond axis) and intensity (0–0.035 a.u.) external electric fields (EEFs) using density functional theory at B3LYP/6-31+G(d,p) and ωB97XD/def2-TZVP levels. Results show that EEFs along the CBr direction induce CBr bond elongation, electron redistribution from NO₂ to Br, increased dipole moment, and weakened molecular stability. CBr bond dissociation occurs at EEF strengths >0.030 a.u., accompanied by a transition of the S₀ → S₁ excitation from n → π* localized excitation to Rydberg excitation with π → p_x feature. In contrast, EEFs along the CN direction shorten CBr bond, without promoting dissociation. The S₀ → S₁ excitation under CN EEFs shifts from n → π* localized excitation to π → π* charge transfer. Fluorine substitution in 5Br2FNB exhibits limited influence on dissociation or excitation compared to mBNB. These findings demonstrate that directionally applied EEFs effectively modulate molecular stability and dissociation pathways, with CBr-oriented EEFs facilitating environmentally relevant Br elimination.

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不同方向和强度的外电场对间溴-硝基苯和5 -溴-2-氟-硝基苯分子解离和激发特性的影响

本文利用密度泛函理论研究了间溴基硝基苯（mBNB）和5-溴-2-氟硝基苯（5Br2FNB）在不同取向（CBr或CN键轴）和强度（0-0.035 a.u）外电场下B3LYP/6-31+G（d,p）和ωB97XD/def2-TZVP水平下的解离和激发特性。结果表明：沿CBr方向电激能诱导CBr键延伸，电子从NO2向Br重分布，偶极矩增大，分子稳定性减弱；在EEF强度为>；0.030 a.u.时，CBr键发生解离，并伴有S0→S1激发由n→π*局域激发向具有π→px特征的Rydberg激发的转变。相反，沿CN方向的电场缩短了CBr键，但不促进解离。CN EEFs下的S0→S1激发由n→π*局域激发转变为π→π*电荷转移。与mBNB相比，5Br2FNB中的氟取代对离解或激发的影响有限。这些研究结果表明，定向应用的EEFs有效地调节了分子稳定性和解离途径，其中cbr导向的EEFs促进了环境相关的Br消除。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Chemical Physics 化学-物理：原子、分子和化学物理

CiteScore

4.60

自引率

4.30%

发文量

278

审稿时长

39 days

期刊介绍： Chemical Physics publishes experimental and theoretical papers on all aspects of chemical physics. In this journal, experiments are related to theory, and in turn theoretical papers are related to present or future experiments. Subjects covered include: spectroscopy and molecular structure, interacting systems, relaxation phenomena, biological systems, materials, fundamental problems in molecular reactivity, molecular quantum theory and statistical mechanics. Computational chemistry studies of routine character are not appropriate for this journal.