In this paper, the structural, electronic, non-linear optical (NLO) properties and vibrational frequencies of
4-(methoxycarbonyl)-phenylboronic acid have been examined theoretically using ab initio Hartree-Fock (HF) and Density Functional Theory (DFT/B3LYP) methods applying the standard 6-311++G(d,p) basis set. ¹H- and ¹³C NMR chemical shifts are calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the B3LYP/6-311++G(d,p) and HF/6-31G(d) levels of the theory. There are two conformers, cis-trans(ct) and trans-cis (tc) for title molecule. The energy difference between ct and tc conformers of studied molecule are of 0.126 kcal/mol with B3LYP/6-311++G(d,p) and 0.138 kcal/mol with HF/6-311++G(d,p), respectively. The conformer ct is more stable than the conformer tc. Also, the energy gap differences between the highest occupied and the lowest unoccupied molecular orbitals, dipole moment, polarizability and first static hyperpolarizability are calculated as a function of both dihedral angle (C3-C4-C7-O3), between methoxycarbonyl group (CH₃-O-CO-) and benzene ring, and dihedral angle (C2-C1-B-O1), between boronic acid group (-B(OH)₂) and benzene ring. In the change of the energy gap and polarizability depending on dihedral angles, it is shown that the polarizabilities follow inverse relationship the energy gaps.

中文翻译：

---

4-（甲氧羰基）-苯基硼酸的结构，振动，构象分析和非线性光学性质的理论研究

在本文中，
从头开始使用Hartree-Fock（HF）和密度泛函理论（DFT / B3LYP）从理论上研究了4-（甲氧基羰基）-苯基硼酸的结构，电子，非线性光学（NLO）特性和振动频率。）应用标准6-311 ++ G（d，p）基集的方法。¹ H-和¹³C NMR化学位移的计算方法是，直接使用标准的包括原子轨道（GIAO）方法的B3LYP / 6-311 ++ G（d，p）和HF / 6-31G（d）级理论。标题分子有两个构象体，顺式-反式（ct）和反式-顺式（tc）。被研究分子的ct和tc构象异构体之间的能量差在B3LYP / 6-311 ++ G（d，p）下为0.126 kcal / mol，在HF / 6-311 ++ G（d，p）下为0.138 kcal / mol ， 分别。构象子ct比构象子tc更稳定。同样，计算最大的未占据分子轨道与最低未占据分子轨道之间的能隙差，偶极矩，极化率和第一静态超极化率，这是甲氧基羰基（CH ₃）之间的两个二面角（C3-C4-C7-O3）的函数。-O-CO-）和苯环，以及硼酸基团（-B（OH）₂）和苯环之间的二面角（C2-C1-B-O1）。在取决于二面角的能隙和极化率的变化中，表明极化率遵循与能隙成反比的关系。