Spectroscopic characterization and electronic structure analysis of Linagliptin by DFT method

Abstract

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.