New palladium complexes with N-heterocyclic carbene and morpholine ligands: Synthesis, characterization, crystal structure, molecular docking, and biological activities

This work includes the synthesis of a new series of palladium-based complexes containing both morpholine and N-heterocyclic carbene (NHC) ligands. The new complexes were characterized using NMR (1H and 13C), FTIR spectroscopic, and elemental analysis techniques. The crystal structure of complex 1b was obtained by utilizing the single-crystal X-ray diffraction method. X-ray studies show that the coordination environment of palladium atom is completed by the carbene carbon atom of the NHC ligand, the nitrogen atom of the morpholine ring, and a pair of bromide ligand, resulting in the formation of slightly distorted square planar geometry. All complexes were determined for some metabolic enzyme activities. Results indicated that all the synthetic complexes exhibited powerful inhibitory actions against all aims as compared to the control molecules. Ki values of new morpholine-liganded complexes bearing 4-hydroxyphenylethyl group 1a-e for hCA I, hCA II, AChE, BChE, and α-glycosidase enzymes were obtained in the ranges 0.93–2.14, 1.01–2.03, 4.58–10.27, 7.02–13.75, and 73.86–102.65 µM, respectively. Designing of reported complexes is impacted by molecular docking study, and interaction with the current enzymes also proclaimed that compounds 1e (–12.25 kcal/mol for AChE and –11.63 kcal/mol for BChE), 1c (–10.77 kcal/mol and –9.26 kcal/mol for α-Gly and hCA II, respectively), and 1a (–8.31 kcal/mol for hCA I) are showing binding affinity and interaction from the synthesized five novel complexes.