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通过光谱或电化学理解化合物HOMO-LUMO能量差的规律与误区

王仕鑫1, 王泽1, 荣中天2, 李朝阳3, 张韶光3   

  1. 1 清华大学探微书院, 北京 100084;
    2 清华大学致理书院, 北京 100084;
    3 清华大学化学系, 生命有机磷化学及化学生物学教育部重点实验室, 北京 100084
  • 收稿日期:2026-04-30 录用日期:2026-06-24
  • 通讯作者: 张韶光 E-mail:sgzhang@tsinghua.edu.cn Shaoguang Zhang
  • 基金资助:
    国家自然科学基金(22571176)；清华大学本科教育教学改革项目

Understanding the patterns and misconceptions of HOMO-LUMO energy differences in compounds through spectroscopy or electrochemistry

Shixin Wang1, Ze Wang1, Zhongtian Rong2, Zhaoyang Li3, Shaoguang Zhang3   

  1. 1 Tanwei College, Tsinghua University, Beijing 100084, China;
    2 Zhili College, Tsinghua University, Beijing 100084, China;
    3 Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, China
  • Received:2026-04-30 Accepted:2026-06-24
  • Contact: Shaoguang Zhang E-mail:sgzhang@tsinghua.edu.cn

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摘要： 本文系统探讨了通过光谱和电化学方法近似测定化合物HOMO (最高电子占据轨道)-LUMO(最低电子未占据轨道)能隙的规律与常见误区。HOMO-LUMO能隙作为理论概念无法直接通过实验获得，而常用的紫外-可见光谱和循环伏安法所得数据实为光学能隙或基本能隙的近似值，二者与HOMO-LUMO能隙存在本质区别。文中分析了这些方法的理论基础及局限性，强调了电子-空穴结合能、轨道弛豫及溶剂效应等因素对能隙测量的影响，指出直接将实验数据等同于HOMO-LUMO能隙的不严谨性，并呼吁在研究与教学中准确理解不同能隙的物理意义，以提升数据解读的科学性与精确性。

关键词: HOMO-LUMO能隙, 光学能隙, 基本能隙, 紫外-可见光谱, 循环伏安法

Abstract: This paper systematically examines the patterns and common misconceptions associated with the estimation of the HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap in compounds using spectroscopic and electrochemical methods. The HOMO-LUMO gap, as a theoretical concept, cannot be directly obtained through experimental measurements. Commonly employed techniques, such as UV-Vis spectroscopy and cyclic voltammetry, yield data that serve as approximations of the optical gap or the fundamental gap, both of which are fundamentally distinct from the true HOMO-LUMO gap. This analysis explores the theoretical foundations and inherent limitations of these methods, highlighting the significant influence of factors such as exciton binding energy, orbital relaxation, and solvent effects on the measured values. It emphasizes the lack of rigor in directly equating experimental data with the HOMO-LUMO gap and calls for a precise understanding of the distinct physical meanings of these different energy gaps in both research and educational contexts, thereby enhancing the scientific accuracy and reliability of data interpretation.

Key words: HOMO-LUMO gap, Optical gap, Fundamental gap, UV-Vis spectroscopy, Cyclic voltammetry