Synthesis, characterization, density functional theory studies and antibacterial activity of a new Schiff base dioxomolybdenum(VI) complex with tryptophan as epoxidation catalyst

A cis-dioxomolybdenum(VI) complex was prepared with MoO2(acac)(2) and a Schiff base ligand (2-((2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid) derived from salicylaldehyde and l-tryptophan in ethanol and designated as [MoO2(Sal-Tryp)(EtOH)]. It was characterized using several techniques including thermogravimetric and elemental analyses and mass, Fourier transform infrared and UV-visible spectroscopies. Theoretical calculations were performed using density functional theory for studying the molecular structure. An in vitro antibacterial activity evaluation showed that [MoO2(Sal-Tryp)EtOH] complex exhibits good inhibitory effects against Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria in comparison to standard antibacterial drugs. It was also found that [MoO2(Sal-Tryp)EtOH] complex successfully catalyses the epoxidation of cyclooctene, norbornene, cyclohexene, styrene, -methylstyrene and trans-stilbene, with 45-100% conversions and 64-100% selectivities. Based on the obtained results, the heterogeneity and reusability of the catalyst seem promising.