Ab initio Hartree–Fock and density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one

Abstract

a b s t r a c tIn the present work, the conformational analysis of 3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)-benzo[d]thiazol-2(3H)-one molecule (abbreviated as 3MOT) was performed by using ab initio HartreeFock (HF) method with 3-21G as the basis set to find the most stable form of 3MOT. Seven staggered stable conformers were observed on the torsional potential energy surfaces. It is shown that 3MOT_1 conformer (D1 = 68.1°, D2 = 73.4°, D3 = À177.4°and D4 = À79.9°) is the most stable form which has chair conformation with the methyl group linked to nitrogen in the axial position. The geometrical parameters, vibrational frequencies and IR intensities of 3MOT were calculated by DFT(B3LYP) method using 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-311G(d), 6-311+G(d), 6-311G(d,p) and 6-311++G(d,p) basis sets for the lowest energy conformer. The solid-state FT-IR spectra was recorded and compared with scaled frequency values. Many normal vibrational bands have been observed to be mixed because of the lacking of symmetry. Determination of the relative weight contribution of each vibrational mode of the observed frequencies indicates the reliability and precision of the spectral analysis. The observed and calculated vibrational frequencies are found to be in good agreement.

Spectroscopic Investigation (FT-IR, FT-Raman, NMR and UV-Vis),Conformational Stability, NBO and Thermodynamic Analysis of 1-(2-Methoxyphenyl) Piperazine and 1-(2-Chlorophenyl) Piperazine by DFT Approach

“…The calculated values for the same vibration are at 2880, 2830, 2780 and 2750 cm -1 . These values match well with the literature [57][58][59][60][61].…”

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“…The increase in conjugation, generally, leads to the intensification of infrared bands. The conjugation and the influence of intermolecular hydrogen bonding result in the lowering of the stretching wavenumbers of C=O vibration (Sıdır et al, 2010). Frequencies of C=O stretching for a DFT method vibrations are in good agreement with the experimental results.…”

Synthesis, Solvatochromic Studies, DFT Calculations, Characterization, and In Silico Molecular Docking Studies of Azo Dyes of 3‐Methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine

“…The distribution of positive or negative charges on each atom in a molecule is an important application of quantum mechanical calculations and it is very significant in explaining the position of the donor and acceptor pairs [48,49] . Each atomic charge on the specific atom affects the molecular polarizability, dipole moment, electronic structure, acidity‐basicity behavior of the atom, as well as properties of the molecular system and also with the help of calculated Mulliken charges, we evaluate the reactive site of the azo molecules [50,51] . The Mulliken atomic charge of the azo compounds ( A 1 –A 4 ) was determined at the B3LYP method of the basic unit 6‐311++G (d, p) and the variance of atomic charge on each different atom in the azo compound ( A 1 –A 4 ) were displayed in Figure 5.…”

“…[48,49] Each atomic charge on the specific atom affects the molecular polarizability, dipole moment, electronic structure, acidity-basicity behavior of the atom, as well as properties of the molecular system and also with the help of calculated Mulliken charges, we evaluate the reactive site of the azo molecules. [50,51] The Mulliken atomic charge of the azo compounds (A 1 -A 4 ) was determined at the B3LYP method of the basic unit 6-311 + + G (d, p) and the variance of atomic charge on each different atom in the azo compound (A 1 -A 4 ) were displayed in Figure 5. And also, the acquisition of the atomic charge on the individual atom is given in Supplementary Table S2.…”