Molecular Electrostatic Potential Surface Map Research Articles

Crystallographic and theoretical analysis of a spirohydantoin derivative: 3-(4‑tert-butylbenzoyl)-1,3-diazaspiro[4.5]decane-2,4‑dione

Providing structural information on drug-like compounds is a significant step in efforts to develop innovative drugs with balanced solubility, cell permeability and target binding. In this paper, a new cyclohexane-5-spirohydantoin tethered with a 4‑tert-butylbenzoyl group was synthesized and its crystal structure was determined using the single crystal X-ray diffraction. The Hirshfeld surface analysis was used to gain a preliminary insight into the proportion and nature of the intermolecular interactions in the crystal structure, while their quantitative description is further presented in terms of a systematic analysis of dimeric motifs representing different recognition modes. A combination of N–H∙∙∙O and C(sp3)–H∙∙∙O hydrogen bonds, C(sp3)–H∙∙∙π, lone-pair∙∙∙π and π∙∙∙π stacking interactions links the molecules into a bilayer having two carbonyl O atoms exposed to the exterior. Further stacking of the bilayers occurs through C(sp3)–H∙∙∙O hydrogen bonds involving these O atoms as acceptors, C(sp3)–H∙∙∙π and π∙∙∙π stacking interactions between the phenyl groups. The molecular electrostatic potential surface map reveals that the carbonyl O atoms of the hydantoin ring and the phenyl ring are electrophilic centers, while the N1–H1 group is a nucleophilic center. The calculated HOMO and LUMO energies were used to semiquantitatively estimate the global reactivity descriptors suggesting the soft nature of the molecule.

Isolation and identification of active ingredients and biological activity of Dioscorea nipponica Makino

This study reported the isolation and identification of bioactive compounds from Dioscorea nipponica Makino, a plant used in traditional medicine for various ailments. Nine compounds were isolated, including a new compound named as diosniposide E, which was elucidated by analyzing its 1H-NMR, 13C-NMR, DEPT, COSY, HMBC and MS data and comparing them with data available in literature. The other eight compounds were identified as known compounds. Theoretical calculations of energy and the generation of a molecular electrostatic potential surface map were employed to assess the antioxidant capacity of nine compounds, the calculation results exhibited that compounds 5 and 6 had strong antioxidant capacities. To further evaluate the antioxidant activities of the investigated compounds, the DPPH and ABTS assays were conducted. The results from the DPPH scavenging activity test revealed that compounds 4–6 exhibited enhanced scavenging activities compared to L-ascorbic acid, while displaying similar efficacy to trolox. Moreover, the ABTS scavenging activities of compounds 4–6 were found to surpass those of L-ascorbic acid and trolox. In terms of α-glucosidase inhibition, compounds 3 and 4 displayed remarkable inhibitory activities that surpassed the effects of acarbose. Additionally, compound 2 exhibited potent anticholinesterase activities, outperforming donepezil. This research provides insights into the potential bioactive compounds present in Dioscoreanipponica Makino and may contribute to its use in traditional medicine.

Synthesis, Characterization, Antioxidant and DFT Studies of Some Novel Schiff Base Compounds

A new Schiff base compound and its derivative, 3-cyclopropyl-4-(4-nitrofuran-1-yl)methyleneamino-4,5-dihydro-1[Formula: see text]-1,2,4-triazol-5-one (3-CNM) and 1-acetly-3-cyclopropyl-4-(4-nitrofuran-1-yl)methyleneamino-4,5-dihydro-1[Formula: see text]-1,2,4-triazol-5-one (1-ACNM), were synthesized. The structures of compounds were characterized by [Formula: see text]C-NMR, 1H-NMR and FT-IR spectroscopy techniques. The antioxidant capacities of the molecules were investigated by different methods (metal chelation, DPPH and reducing power). Some quantum chemical calculations are performed on the B3LYP, B3PW91, MPW1PW91 functionals with the 6-311++G(d,p) level basis set of the density functional theory (DFT). Using the optimized structures of Schiff bases, the frontier molecular orbital, the theoretical spectroscopic and the nonlinear optic (NLO) analysis, the molecular electrostatic potential (MEP) surface, the thermodynamic parameters, the dipole moment, the molecular geometric properties and the total energy were calculated. The calculation results showed that the 3-CNM compound can be used as a suitable and good nonlinear optical compound. In addition, electronegative and electropositive atoms were determined from the MEP surface map. The difference between ([Formula: see text]) the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) energies was calculated as 3.3[Formula: see text]eV and 3.4[Formula: see text]eV for 3-CNM and 1-ACNM, respectively, and these values express the chemical stability of the molecule and the orbital interactions. This work is important because it includes the synthesis of two new molecules and theoretical calculations that support their experimental properties. It can also provide significant benefits in terms of synthesis of similar Schiff base compounds and their calculated electronic, geometric and thermodynamic properties.

Non-covalent interactions and spectroscopic study of chalcone derivative 1-(4-chlorophenyl)-3-(5-methylfuran-2-yl) prop-2-en-1-one

Flavonoids are an object of continuously growing interest because of their simple structure and abundance in nature. Among flavonoids; chalcone derivatives have been identified as very useful compounds, showing a variety of bioactivity and nonlinear optical activity. A combined experimental and theoretical study of a newly synthesized heterocyclic chalcone derivative chemically named as 1-(4-chlorophenyl)-3-(5-methylfuran-2-yl) prop-2-en-1-one (CPMFP) has been characterized using FT-IR, FT-Raman and UV–Vis spectroscopy 113and their experimental results were analyzed in the light of theoretical results obtained by density functional method. The comparison of experimental and calculated UV–Vis absorption spectrum, HOMO-LUMO energy gap and related parameters describing the electronic transitions has been discussed. The first order hyperpolarizability has been calculated using the finite field approach which shows the feeble nonlinear optical behavior of the title compound. The natural bond orbital (NBO) analysis has revealed the bonding-antibonding interactions present in the title compound. The possible sites for the electrophilic/nucleophilic attack have been predicted through the molecular electrostatic potential surface map. In addition to this, a complete quantum theory of atom in molecule (QTAIM) and multi-wavefunction (Multiwfn) analysis of monomer and dimer models of CPMFP has been performed which showed the strength and type of inter/intra molecular interactions present in the title compound.

Experimental and theoretical DFT (B3LYP, X3LYP, CAM-B3LYP and M06-2X) study on electronic structure, spectral features, hydrogen bonding and solvent effects of 4-methylthiadiazole-5-carboxylic acid

ABSTRACTDetailed structural, electronic and spectroscopic study of 4-methylthiadiazole-5-carboxylic acid, one of the simplest 1,2,3-thiadiazole derivatives has been performed using density functional theory at four different functionals (B3LYP, X3LYP, CAM-B3LYP and M06-2X). The two possible conformers and their dimeric forms have been investigated for the stability and hence for the calculation of molecular properties of the title compound. Vibrational analysis has been performed with the help of experimental FT-IR and FT-Raman spectra. NBO analysis has been performed to estimate the N–H—O=C hydrogen bond strength and to evaluate the intra and inter molecular charge transfer in the system. Intermolecular hydrogen-bond strength has also been computed using Atoms in Molecules (AIM) theory. To visualise spatial domain, key sites of electron transitions and electron density difference between ground as well as excited states, and their 2D and 3D plots have been computed. Solvent effect on the intermolecular hydrogen bonding have also been investigated using solvents of different polarities. Non-linear optical properties, molecular electrostatic potential surface map (MESP), thermodynamic potentials at different temperatures have also been computed and plotted.

Structural and vibrational analyses of new potential anticancer drug 2-(phenylmethyl)-2-azaspiro[5.11]heptadecane-1,3,7-trione

The establishment of the most stable structures of 2-(phenylmethyl)-2-azaspiro[5.11]heptadecane-1,3,7-trione, potential anticancer and antimicrobial drug has been investigated in this work. A detailed interpretation of experimental and calculated IR, UV and NMR spectra were reported. The equilibrium geometry, harmonic vibrational frequencies and electronic properties have been investigated with Density Functional Theory using B3LYP/6-311++G(d,p) method. The scaled theoretical wavenumber showed very good agreement with the experimental values. The charge transfer in the molecule was confirmed with NBO analysis. Ultraviolet–visible spectrum was calculated using TD-DFT method and compared with experimental spectrum. The calculated energy and oscillator strength well reproduce the experimental data. The molecular electrostatic potential surface map portrays potential binding sites of the title molecule.

Conformational search, spectral analysis and electronic properties of 5-(4-Pyridinyl)-1,3,4-thiadiazol-2-amine

Comprehensive investigation of molecular geometry and electronic structure of 5-(4-Pyridinyl)-1,3,4-thiadiazol-2-amine in ground as well as in the first excited state has been carried out. The stable conformers of the title compound have been determined from the 3D potential energy scan by varying selected dihedral angles, responsible for conformational flexibility. As the energy difference between the conformers was very small, the relative stability has been confirmed at potentially high-level G2MP2 method. The most stable structure was optimized with B3LYP and M06-2X functional using polarized triple-zeta 6-311++G(d,p), to obtain the ground state structure and calculation of vibrational wavenumbers. Experimental FT-IR and FT-Raman spectra were compared with theoretical spectral data. Dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface map have been calculated to get a better insight of the properties of title molecule. Frequency-dependent first hyperpolarizability β(−2ω;ω,ω) has also been evaluated to gauge the non-linear optical behavior of the title compound. Natural bond orbital (NBO) analysis has been done to study the stability of the compound arising from charge delocalization. UV–Vis spectrum, possible solvent-solute interaction and electronic properties such as frontier orbitals, band gap energies have been calculated by TD-DFT approach. 1H nuclear magnetic resonance chemical shifts of the title compound were calculated using the Gauge-Including Atomic Orbital (GIAO) method and compared with experimental data.

Quantum Chemical and Spectroscopic Investigations of (Ethyl 4 hydroxy-3-((E)-(pyren-1-ylimino)methyl)benzoate) by DFT Method

In the present work we have reported the optimized ground state geometry, harmonic vibrational frequencies, NMR chemical shifts, NBO analysis, and molecular electrostatic potential surface map of the title compound using DFT/B3LYP/6-311++G(2d, 2p) level of theory. We have compared our calculated results with the experimentally obtained values and found that both are in close agreement with each other. We have used the gauge-invariant atomic orbital (GIAO) approach to calculate the NMR (13C and 1H) chemical shifts using Gaussian 09 package. TD-DFT (time-dependent DFT) approach has been used to simulate the electronic spectra of the title compound in order to account for excited states. Other molecular properties such as HOMO-LUMO energies, NBO analysis, and PED distribution analysis have been studied and reported using DFT/B3LYP/6-311++G(2d, 2p) level of theory.

Molecular structure, vibrational and electronic properties of 4-Phenyl-3H-1,3-thiazol-2-ol using density functional theory and comparison of drug efficacy of keto and enol forms by QSAR analysis

4-Phenyl-3H-1,3-thiazol-2-ol can exist in two tautomeric forms – keto and enol. Comprehensive investigation of molecular geometry and electronic structure in ground as well as in the first excited state of 4-Phenyl-3H-1,3-thiazol-2-ol (enol) has been carried out. To determine lowest-energy molecular conformation of the title molecule, the selected torsion angles were varied in steps of 10° and molecular energy profile was calculated from −180° to +180°. Experimental FT-IR and FT-Raman spectra of title compound were compared with the spectral data obtained by DFT/B3LYP method. Dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface map have been calculated to get a better insight of the properties of title molecule. Natural bond orbital (NBO) analysis has been done to study the stability of the molecule arising from charge delocalization. UV–Vis spectrum of the title compound was also recorded and electronic properties such as frontier orbitals and band gap energies were calculated by TD-DFT approach. To compare the drug efficacy of enolic and keto forms, QSAR properties of both forms have also been computed and discussed.