Novel Schiff bases derived from N-aryl maleimide derivatives as an effective antimicrobial agent: Theoretical and experimental approach.

A set of new Schiff bases of N-aryl 3- and 4-substituted maleimides has been prepared via condensation of N-aryl 3- and 4- substituted maleimides with p-toluene sulfonyl hydrazide in acidic medium at room temperature. The structures of synthesized compounds were characterized by IR, 1H NMR, 13C NMR, MS spectral data, and further confirmed by single-crystal x-ray crystallography for 5c. The computational study was carried out using Gaussian 09 software by using the B3LYP/6-311+G(d,p) basis set. Single-crystal study results showed much closeness with computational study results. These novel compounds were screened for their antimicrobial activity against two pathogenic bacteria such as Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC25923) and two pathogenic fungi such as Aspergillus niger (MCIM10231) and Candida albicans (MTCC6275). The investigation of antimicrobial screening data showed that the most of tested compounds are moderate to good microbial inhibitors.

Preparation of silver nanoparticles in the presence of polyoxometalates.

The mechanisms of reduction of silver ions and subsequently oxidation of silver atoms in the presence of polyoxometalates (POMs) are discussed. A step-by-step room temperature electron reduction of silver ions and its subsequent reactions has been used in this work to monitor oxidation of silver atoms and its clusters. The silver atoms can transfer electron to POMs is revealed by decrease in the yield of silver clusters and increase in their decay rates. The results of continuous γ-irradiation are compared using UV-visible (UV-Vis) absorption spectra, underlying the effect of silver atoms accumulation in the absence of POMs. Silver nanoparticles (Ag NPs) prepared by reduced silicotungstic acid (STA) were used as Raman substrate and also for antibacterial studies against panel of human pathogenic bacteria. The Ag NPs exhibited antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens evaluated by well diffusion assay. The inhibition zones were within the range of 10 to 14 mm. We have also explored the surface enhanced Raman scattering (SERS) activity of the Ag NPs substrates using 1.0 × 10-7 M solution of crystal violet (CV) as Raman probe molecule. It was possible to detect SERS spectral pattern of CV on Ag NPs substrate with a high signal-to-noise ratio. Both SERS and antibacterial studies show that this simple, low cost, and greener method for synthesizing Ag NPs may be valuable in future studies about SERS sensor development and bio-applications.