The spectroscopic and electronic characterization of the molecule Linagliptin (LGP), one of the most important type-2 diabetes drugs, has been studied by the quantum mechanical method. The optimized molecular structure, electronic properties, dipole moment, rotational constants and important thermodynamic parameters of LGP molecule have been computed using HF (Hartree-Fock) and DFT (density functional theory) methods with 6-311++G (d,p) basis set. Spectroscopic properties such as FT-IR, Raman and absorption spectra are calculated in different solvents by the TD-DFT method and compared with the experimental data. The various types of intra-molecular interactions such as conjugative, hyper conjugative and other structural effects are analyzed from natural bonds orbitals of LGP. The relationship between linear polarizability and refractive index is used to describe the polarization behaviour of LGP in different solvents. The electronic charge density at different positions and reactivity descriptors of LGP are used in identifying the site of drug interaction. The various intra-molecular interactions are explained in terms of HOMO and LUMO energies. Mulliken charges and thermodynamic properties of LGP are also discussed.

中文翻译：

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利格列汀的 DFT 光谱表征和电子结构分析

利格列汀 (LGP) 是最重要的 2 型糖尿病药物之一，其光谱和电子特性已通过量子力学方法进行了研究。使用 HF (Hartree-Fock) 和 DFT (密度泛函理论) 方法以 6-311++G (d,p) 计算了优化的分子结构、电子特性、偶极矩、旋转常数和重要的热力学参数基组。通过TD-DFT方法计算了不同溶剂中的FT-IR、拉曼和吸收光谱等光谱特性，并与实验数据进行了比较。从 LGP 的自然键轨道分析了各种类型的分子内相互作用，例如共轭、超共轭和其他结构效应。线性极化率和折射率之间的关系用于描述导光板在不同溶剂中的极化行为。LGP不同位置的电荷密度和反应性描述符用于识别药物相互作用的部位。各种分子内相互作用用 HOMO 和 LUMO 能量来解释。还讨论了 LGP 的 Mulliken 电荷和热力学性质。