Conformational analysis, inter-molecular interactions, electronic properties and vibrational spectroscopic studies on <i>cis</i>-4-hydroxy-<i>d</i>-proline

<p>The present study deals with a non-native amino acid, <i>cis</i>-4-hydroxy-<i>d</i>-proline (CHDP) using density functional theory at B3LYP/6-31+G(d,p) level. The potential energy surface scan reveals the global minimum structure of CHDP along with two potential conformers. Highest occupied molecular orbital, lowest unoccupied molecular orbital, and molecular electrostatic potential surfaces are used to explain the chemical reactivity of title molecule. The atomic charge analysis has been carried out using Mulliken and natural population schemes. The equilibrium geometry of CHDP dimer has been obtained and inter-molecular interactions are explored using QTAIM and Natural bonding orbital analyses. Vibrational spectroscopic analysis has been performed on CHDP monomer and dimer at the same level of theory. Assignments to all vibrational modes up to 400 cm⁻¹ have been offered along with their potential energy distribution to the maximum possible accuracy. The calculated frequencies are scaled by an equation, rather than by a constant factor and then compared with experimental FT-IR frequencies obtained by KBr disc and Nujol mull techniques. A number of electronic and thermodynamic parameters have also been evaluated for CHDP monomer and dimer.</p

FT-IR, UV–visible, and NMR Spectral Analyses, Molecular Structure, and Properties of Nevadensin Revealed by Density Functional Theory and Molecular Docking

<p>Nevadensin 2-(4-methoxyphenyl)-5,7-dihydroxy-6,8-dimethoxy-4<i>H</i>-1-benzo-pyran-4-one] is a natural bioactive flavonoid compound that has the potential to become a novel “natural lead” in the field of drug discovery program. The molecular structure, vibrational frequencies, and corresponding vibrational assignment of nevadensin have been investigated experimentally and theoretically by employing the B3PW91/6–311++G(d,p) method. The fundamental vibrational wave numbers as well as their intensities were calculated, and a good correlation between experimental and scaled calculated wave numbers had been accomplished. The ultraviolet spectrum of the studied molecule was recorded in the region 200–500 nm, and the electronic properties were predicted by the time-dependent density functional theory approach. ¹H and ¹³C NMR spectra have been calculated by employing the gauge-independent atomic orbital method. Nevadensin has been reported to exhibit antimicrobial activities against both Gram-positive and Gram-negative bacteria and also against the fungal pathogens, highlighting the pharmacological importance of the molecule.</p