Density functional study on the structural conformations and intramolecular charge transfer from the vibrational spectra of the anticancer drug combretastatin‐A2

Abstract

Combretastatin-A2 (CA2), a potential anticancer drug in advanced preclinical development, is extracted from the medicinal plant Combretum caffrum. The NIR-FT Raman and FT-IR spectral studies of the molecule were carried out and ab initio calculations performed at the B3LYP/6-31G(d) level to derive the equilibrium geometry as well as the vibrational wavenumbers and intensities of the spectral bands. The vibrational analysis showed that the molecule has a similar geometry as that of cis-stilbene, and has undergone steric repulsion resulting in twisting of the phenyl ring with respect to the ethylenic plane. Vibrational analysis was used to investigate the lowering of the stretching modes, and enhancement of infrared band intensities of the C-H stretching modes of Me2 may be attributed to the electronic effects caused by back-donation and induction from the oxygen atom. Analysis of phenyl ring modes shows that the CA2 stretching mode 8 and the aromatic C-H in-planebending mode are equally active as strong bands in both IR and Raman spectra, which can be interpreted as the evidence of intramolecular charge transfer (ICT) between the OH and OCH 3 groups via conjugated ring path and is responsible for bioactivity of the molecule.

HOMO-LUMO, NBO and Vibrational analysis of Sitagliptin by using DFT calculations and Experimental Study (FT-IR, FTRaman and UV-Visible Spectroscopies)

“…The energy gap between HOMO and LUMO is a critical parameter in describing molecular electrical transport properties [28]. In recent times the energy gap between HOMO and LUMO were used to prove the bioactivity from intermolecular charge transfer [62][63]. In this present study, the 3D structure of the HOMO and LUMO for the title molecule are shown in Fig.…”

Synthesis photophysical studies of some furfurylnitrones: high-ly selective chemosensors for Zn2+ and DFT studies

“…The frontier molecular orbital's play a pivotal role in the electrical and optical properties, as well as in chemical reactions, UV-vis and fluorescence spectra (Padmaja et al 2009;Tovar et al 2008). The contour surfaces of the FMO (Frontier Molecular Orbital's) for molecule 2 are drawn in Fig.S17.…”

Structure, electronic properties, NBO, NLO and chemi-cal reactivity of bis (1, 4-dithiafulvalene) derivatives: functional density theory study

“…The HOMO represents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron. Recently, the energy gap between HOMO and LUMO has been used to prove the bioactivity from intra-molecular charge transfer (ICT) (Padmaja et al 2009;Sagdinc et al 2009), and describes the chemical reactivity, optical polarizability, kinetic stability, and chemical softness-hardness of a molecule. The molecules having a small energy gap are known as soft and having a large energy gap are known as hard molecules.…”