Negative Absorption Peaks in Ultraviolet-Visible Spectrum of Water

Theoretical and experimental studies of cephalexin adsorption on aluminium as a new alternative of removal from wastewater

Cephalexin (CPX) is an antibiotic widely used to treat many infections. CPX has become an emerging pollutant present in wastewater. On the other hand, it is well known that organic compounds can be adsorbed over metal surfaces when the metal is in active state such as when it is rusting. This work proposes an alternative for the elimination of CPX from wastewater, applying electrochemical principles using a conventional and cheap substrate, aluminium. The first part consisted of obtaining the active states of aluminium electrodes carrying out voltametric curves at different pH (4, 7 and 9) to find the particular condition of interaction between CPX and metal surface. The potential was used in the potentiostatic tests to set the activation potential of metal at different times. After the treatment, electrolyte solutions were analysed using UV-vis spectra, and the aluminium surfaces were studied by optical micrographs and X-ray diffraction. In addition, aluminium-CPX interactions were corroborated by quantum-chemical calculations and adsorption isotherms. All results indicate that it was possible for the CPX removal at basic pH conditions, where the molecule adsorption on the aluminium substrate occurs due to a strong electrostatic interaction.

Study of Interactions Between 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine and Human DNA by Theoretical, Spectroscopic and Viscometric measurements

From the last few years mode of interactions between drugs and DNA is an attractive research area as it bridges chemistry, molecular biology and medicinal science. Interactions between small heterocyclic molecules and human DNA is a noteworthy feature in pharmacology for investigation of drugs mechanism and designing of more effective and target specific drugs with fewer side effects. The present research work focuses on the theoretical investigations of 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine (SASA) by using Gaussian (16 W) software to predict optimized geometry, HOMO-LUMO gap, bond length, bond angle, dihedral angle, electronic and vibrational spectra. Possible reaction site observed in SASA was C_7, C₉ and C₁₈ as these atoms show maximum charge density. Later the interactions of SASA with human DNA was explored spectroscopic investigations and viscometric investigations at physiological buffers of pH of 4.7 (stomach pH) and 7.4 (blood pH) respectively. Maximum absorbance between SASA-DNA complex was observed in buffer solution of pH 3.4 at wavelength of 370 nm, whereas at 7.4 has maximim absorbance between. Spectroscopic results reflects the bathochromic and hyperchromic shift succeeding the addition of human DNA. During viscosity measurement, intercalation and electrostatic mode of interaction were detected at low and high concentration of drug in solution respectively. Increase in the value of rate constant was observed with the increase in concentration of drug. Larger values of rate constant were observed at pH 7.4 in comparison to pH 3.5. Rate constant, thermodynamic parameters and viscometric analysis prefers the intake of SASA via blood.

Computational Studies Followed by Effect of Solvent Polarity and Salts on HOMO-LUMO Gap of 7-Hydroxy Coumarine Notabally Reflected by Absorption and Emission Spectra

7-Hydroxycoumarin's FT-IR solid phase spectra were observed at 4000-400 cm^-1. The spectra were analyzed in aspects of significant approaches. DFT was used to optimize the structure of the compound and its structural properties. The molecular properties were also determined by the HF/3-21G level. The bond lengths and bond angles were obtained by the computational study of the optimized geometry. The vibrational frequencies were determined in all these approaches, which were then matched to experimental frequencies, yielding an excellent agreement between measured and estimated frequency ranges. The UV-visible spectrum of 7HC was obtained and the electronic characteristics HOMO and LUMO energies were monitored by the time-dependent TD-DFT method. The spectral behavior of 7-Hydroxycoumarin was studied using fluorescence spectroscopy in a wide range of polar and non-polar solvents. Solvatochromic effect was observed in both the fluorescence and absorption spectra. The structural properties, energies, IR intensities, absorption wavelengths, and harmonic vibrational frequencies were compared with the obtainable experimental information of the molecule.