Kamlesh Sharma

Synthesis, spectroscopic and physicochemical investigations of environmentally benign heterocyclic Schiff base derivatives as antibacterial agents on the bases of in vitro and density functional theory.

A series of Schiff bases were synthesized by the reaction of 4-dimethylamino-benzaldehyde and corresponding active amines under microwave irradiation. Results obtained from spectroscopic (FT-IR, (1)H NMR, (13)C NMR, GC-MS) and elemental analyses of synthesized compounds were in a very good agreement with their chemical structures. UV-Vis and fluorescence spectroscopy measurements provided that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including singlet absorption, extinction coefficient, Stokes shift, oscillator strength and dipole moment, were investigated in order to explore the analytical potential of synthesized compounds. The antibacterial activity of these compounds was first studied in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria. The minimum inhibitory concentration was then determined with the reference of standard drug tetracycline. The results displayed that compound 1 was better inhibitors of both types of the bacteria (Gram-positive and Gram-negative) than tetracycline. Based on the density functional theory calculations, LUMO and density of compounds (1-5) were calculated to support the antibacterial activities.

Synthesis of steroidal thiazolidinones as antibacterial agents based on the in vitro and quantum chemistry calculation

Steroidal thiazolidinone derivatives were prepared from the reaction of steroidal thiosemicarbazones with ethyl bromoacetate in dioxane. Steroidal thiosemicarbazones were prepared by reacting thiosemicarbazide with steroidal ketones. The structures of these compounds were elucidated by IR, 1HNMR, 13CNMR, and mass spectral study, and their purities were confirmed by elemental analyses. The antibacterial activities of these compounds were evaluated by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration of compounds were determined. The results showed that steroidal thiazolidinone derivatives are better in inhibiting growth as compared with steroidal thiosemicarbazone derivatives of both types of the bacteria. Compounds 7 and 8 are better antibacterial agents as compared with standard drug, Amoxicillin. Based on the quantum chemistry calculation at the DFT/6-31G* level, the frontier molecular orbitals and electrostatic potential of compounds 7 and 8 were also discussed.

One Pot Synthesis, Photophysical and X-ray Studies of Novel Highly Fluorescent Isoquinoline Derivatives with Higher Antibacterial Efficacy Based on the In-vitro and Density Functional Theory

AbstractSeries of cyano substituted isoquinoline dyes were synthesized by one-pot multicomponent reactions (MCRs) of aldehydes, malononitrile, 6-methoxy-1,2,3,4-tetrahydro-naphthalin-1-one and ammonium acetate. Results obtained from spectroscopic (FT-IR, 1H-NMR, 13C-NMR, EI-MS) and elemental analysis of synthesized compounds was in agreement with their chemical structures. Structure of the compound was further conformed by X-ray crystallographic. UV-vis and fluorescence spectroscopy measurements provided that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including electronic absorption, extenction coefficient, Stokes shift, oscillator strength transition dipole moment and fluorescence quantum yield were investigated in order to explore the analytical potential of synthesized compounds. The anti-bacterial activity of these compounds were first studied in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria. The minimum inhibitory concentration was then determined with the reference of standard drug chloramphenicol. The results displayed that compound 3 was better inhibitors of both types of the bacteria (Gram-positive and Gram-negative) than chloramphenicol. Furthermore, quantum chemistry calculations using DFT/6-31-G* level of theory confirm the results. Dipole moment and frontier molecular orbitals were also investigated. Graphical Abstractᅟ

Microwave Assisted Synthesis, Physicochemical, Photophysical, Single Crystal X-ray and DFT Studies of Novel Push–Pull Chromophores

Two push-pull chromophores were synthesized by knoevenagel condensation under microwave irradiation. The structure of synthesized chromophores were established by spectroscopic (FT-IR, 1H NMR, 13C NMR, EI-MS) and elemental analysis. Structure of the chromophores was further conformed by X-ray crystallographic. UV-Vis and fluorescence spectroscopy measurements provided that chromophores were good absorbent and fluorescent properties. Fluorescence polarity studies demonstrated that chromophores were sensitive to the polarity of the microenvironment provided by different solvents. Physicochemical parameters, including singlet absorption, extinction coefficient, stokes shift, oscillator strength, dipole moment and flurescence quantum yield were investigated in order to explore the analytical potential of the synthesized chromophores. In addition, the total energy, frontier molecular orbitals, hardness, electron affinity, ionization energy, electrostatic potential map were also studied computationally by using density functional theoretical method.