Synthesis, Characterization, and Antibacterial Evaluation of Heteroleptic Oxytetracycline-Salicylaldehyde Complexes

A new series of mixed ligand complexes of Cd(II) and Mo(V) were successfully synthesized by refluxing the mixture solution of oxytetracycline hydrochloride (OTC.HCl) with an aqueous and alcoholic solution of metal (M = Cd(II) and Mo(V)) salts and an alcoholic solution of salicylaldehyde (Sal). The complexes were characterized by modern analytical and spectral methods such as elemental microanalysis, pH, conductivity, surface tension, viscosity, melting point, and spectral methods such as FT-IR, NMR, electronic absorption, SEM, and mass spectrometry. Conductivity measurements of the complexes revealed their electrolytic nature. The kinetic and thermal stabilities were investigated using thermogravimetric and differential thermal analysis techniques. Thermodynamic and kinetic parameters such as E∗, ΔH∗, ΔS∗, and ΔG∗ were calculated from TG curves using the Coats–Redfern method. Geometry optimization of the proposed structure of the complexes was achieved by running MM2 calculations in a Gaussian-supported CS ChemOffice 3D Pro.12.0 version software. The final optimized geometrical energies for respective Cd-OTC/Sal and Mo-OTC/Sal complexes were found to be 923.1740 and 899.3184 kcal/mol. The electronic absorption spectral study revealed a tetrahedral geometry for the Cd-OTC/Sal complex and octahedral geometry for the Mo-OTC/Sal complex. The antibacterial sensitivity of the complexes was evaluated against three bacterial pathogens such as S. aureus, E. coli, and P. mirabilis using the modified Kirby–Bauer paper disc diffusion method. The antibacterial study revealed significant growth inhibitory action of the complexes.

Unsymmetrical Schiff Base Functionalized as Monobasic Tridentate Ligand on Complexation with Some Transition Metal Ions

Cu(II), Co(II), Ni(II) and Mn(II) complexes of Schiff base derived from 2-aminophenol and pyrrole-2- carbaldehyde have been prepared. The complexes are formed by coordination of N and O atoms of the ligand. Their structures were characterized by physico-chemical and spectroscopic methods. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a tetrahedral/ square planar geometry. The bio-efficacy of the ligand and their complexes has been examined against the growth of bacteriain vitroto evaluate their anti-microbial potential.

Photochemistry of 3-alkoxychromones I — Photocyclisation of 6-chloro-3-alkoxy-2-(furan-3-yl)-4H-chromen-4-ones

3-Alkoxy/allyloxy-6-chloro-2-(furan-3-yl)-4H-chromen-4-ones yield angular tetracyclic products involving the 2-furyl group on photoirradiation through the intermediacy of 1,4-biradicals. The nature of the 3-alkoxy/allyloxy group influenced the photoproduct distribution. The stereochemical dispositions of the products have been established using the J/Φ relationship and were corroborated by MM2 calculations.

Conformational analysis of acetylcholine and related choline esters

The crystal structures of carbamoylcholine [2-(carbamoyloxy)-N,N,N-trimethylethanaminium] chloride, bromide and iodide, methoxycarbonylcholine [2-(methoxycarbonyloxy)-N,N,N-trimethylethanaminium] iodide, acetylcholine [2-(acetyloxy)-N,N,N-trimethylethanaminium] chloride and succinylcholine { 2,2′-[(1,4-dioxo-1,4-butanediyl)bis(oxy)]bis(N,N,N-trimethylethanaminium)} iodide have been redetermined at 105 K in order to obtain detailed and accurate information on the geometry of choline esters and to elucidate the conformationally dependent changes of geometry. The conformational flexibility and the preferred conformations are elucidated based on results obtained from X-ray crystallographic studies and molecular mechanics (MM2) calculations. The usefulness of molecular mechanics calculations for quaternary ammonium ions is discussed.