Radical scavenging efficacy of L-cysteine (L-Cys), glutathione (GSH) and thioctic acid (TA) in the presence of silver nanoparticles (AgNPs) were determined by 1,1-diphenyl 2-picryl hydrazil (DPPH), nitric oxide (NO) and hydroxyl (OH) radicals as spectrophotometric assay. The hydrogen peroxide (H₂O₂) scavenging efficacy has been determined by titration method. Ascorbic acid has been used as standard for all radical scavenging efficacies. In general, antioxidant activity decreases in the presence of AgNPs. The covalent interactions of thiols (-SH) were found to be a key factor for the decreases in scavenging activity. The effect of thiol concentrations has been discussed. The size and shape of the nanoparticles and AgNP-SR interactions have been characterized through Transmission Electron Microscopy (TEM) and Fourier Transform Infrared (FTIR) spectroscopy, respectively.

The present work demonstrates the single crystal X-ray and DFT analysis of $ [{(2,4-CH_{3})_{2}C_{6}H_{3}O}_{2}$PS_{2}HNEt_{3}]$ (1) and $ [{(3,4-CH_{3})_{2}$ $C_{6}H_{3}O}_{2}$ $PS_{2}HNEt_{3}]$ (2) along with computational analysis of $ [{(3,5-CH_{3})_{2}C_{6}H_{3}O}_{2} $PS_{2}HNEt_{3}]$ (3) by using density functional theory (DFT) in its hybrid form B3LYP method. Compounds1 and 2 crystallize in the orthorhombic space group Pbca and triclinic space groupP1,respectively andtheir X-ray analysis reveals that phosphorus atom is coordinated to the two S and two O atoms to form tetrahedralgeometry. The structure is stabilized by cation–anion N–H.... S hydrogen bonded interactions. The structuralparameters, vibrational bands and energy gaps of frontier orbitals (HOMO–LUMO) have been calculated.The calculated geometric and spectral results matched the experimental data with good agreement. Theoreticallycalculated frontier molecular orbitals (HOMO–LUMO) and their energies suggest that charge transferoccurs within the compounds.