Jezowski Sebastian R, Baer Ryan, Monaco Stephen, Mora-Perez Carlos A, Schatschneider Bohdan
Department of Chemistry, Murray State University, 42071, USA.
The Eberly Campus, The Pennsylvania State University-Fayette, 15471, USA.
Phys Chem Chem Phys. 2017 Feb 1;19(5):4093-4103. doi: 10.1039/c6cp07403k.
The drive to develop new organic materials for use in optoelectronic devices has created the need to understand the fundamental role functionalization plays concerning the electronic properties of conjugated molecules. Here density functional theory (DFT) is used to investigate how the HOMO-LUMO gaps of halogenobenzenes are affected as a function of substituent size, position, electronegativity, ionization potential, and polarizability. A detailed molecular orbital analysis is also provided. It is shown that the molecular static polarizability and ionization potential of the bound halogens are the primary physical descriptors governing the HOMO-LUMO gap within halogenobenzenes. Two secondary descriptors controlling the HOMO-LUMO gap in these materials are the aromaticity of the halogen substituted benzene rings (as monitored via the harmonic oscillator method of aromaticity index [HOMA]) and the reduced population of the halogen atomic orbitals in the frontier MOs (%X or %X). The molecular polarizability and aromaticity, as well as %X and %X, are shown to be a function of halogen electronegativity and size, as well as number and position on the ring. It is ultimately demonstrated that halogenobenzenes which are most polarizable and are either least aromatic and/or exhibit the smallest %X (or largest %X) values, have the smallest HOMO-LUMO gaps.
开发用于光电器件的新型有机材料的需求促使人们需要了解官能化对共轭分子电子性质所起的基本作用。在此，利用密度泛函理论（DFT）来研究卤代苯的最高占据分子轨道（HOMO）-最低未占分子轨道（LUMO）能隙如何随取代基大小、位置、电负性、电离势和极化率而变化。还提供了详细的分子轨道分析。结果表明，结合卤素的分子静态极化率和电离势是决定卤代苯中HOMO-LUMO能隙的主要物理描述符。控制这些材料中HOMO-LUMO能隙的两个次要描述符是卤素取代苯环的芳香性（通过芳香性指数的谐振子方法[HOMA]监测）以及前沿分子轨道中卤素原子轨道的电子占据减少量（%X或%X）。分子极化率和芳香性，以及%X和%X，被证明是卤素电负性和大小以及环上数量和位置的函数。最终证明，极化率最高且芳香性最低和/或%X（或%X）值最小的卤代苯具有最小的HOMO-LUMO能隙。
