Spectroscopic characterization and Electronic structure of Linagliptin by DFT analysis method

Abstract

Linagliptin (LGP) is the one of the most important drug in type 2 diabetes. In this compound

to study on the spectroscopic and electronic behavior by the quantum mechanical method. The optimized molecular structure, electronic properties, dipole moment, rotational constants and important thermodynamic parameters of LGP molecule are computed and compared using HF (Hartree-Fock) and DFT( Density Functional  Theory )  methods with 6-311++G (d,p) basis sets. Spectroscopic characterization of experimental FT-IR and Raman frequencies are compared with the calculated scaled vibrational frequencies and also compared theoretical and experimental obtained wavelengths of maximum absorption (λmax) of LGP in different solvents of water, ethanol, and methanol are calculated by the TD-DFT method. The various types of intra-molecular interactions such as conjugative, hyper conjugative and other structural effects are analyzed in Natural bonds orbital of LGP. The relationship between linear polarizability (α) and refractive index (n) was used to describe the polarization behavior of LGP in a different solvent. 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 were explained in terms of HOMO and LUMO energies. Mulliken charges and thermodynamic properties of LGP are discussed.