Study based on docking of antimicrobial activity and fluorescence behavior of ammonium salt of diisopropyl dithiophosphate, <i>O</i>,<i>O</i>′- diisopropanediyl <i>S</i>-(<i>N</i>-phthalimido methyl) and zinc diisopropyl dithiophosphates

The ammonium salt of diisopropyl dithiophosphate (A1), O,O′- diisopropanediyl S-(N-phthalimido methyl) dithiophosphate (L1) and zinc diisopropyl dithiophosphate (L2) were isolated in non-aqueous medium and well-characterized by UV–visible spectroscopy, infrared (IR) spectroscopy, NMR (1H, 13C and 31P) spectra and single-crystal X-ray diffraction analysis. The isopropyl group attached to the metal in compound L2 functions as the inter- and intra-chelating group which deviate slightly from planarity with the metal atoms. The central eight-membered ring possesses the “cradle” configuration. The fluorescence spectra of the three compounds A1, L1 and L2 were compared and it was observed that derivatives show excitation due to electron-donor and -acceptor groups. The intramolecular charge transfer (ICT) occurs from P = S to one of the C = O groups in the phthalimide ring and thiophosphate when these molecules are excited electronically in a polar solvent and, therefore, ICT state displays a fluorescence property. The molecular docking study was also carried out for the three compounds. Based on docking studies, a zinc-based metal complex of isopropyl dithiophosphate showed good antifungal activity whereas phthalimide-based isopropyl dithiophosphate derivative showed better antibacterial activity.