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 (1 H and 13 C), 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.

New PEPPSI-Pd-NHC complexes bearing 4-hydroxyphenylethyl group: Synthesis, characterization, molecular docking, and bioactivity properties.

Five 4-hydroxyphenylethyl substituted pyridine enhanced, precatalyst, preparation, stabilization, and initiation-Pd-N-heterocyclic carbene (PEPPSI-Pd-NHC) complexes are synthesized in a straightforward way. All PEPPSI-Pd-NHC complexes were prepared by mixing 4-hydroxyphenylethyl substituted NHC precursors, palladium chloride, potassium carbonate, and potassium bromide in pyridine. All complexes were screened for human carbonic anhydrase I (hCA I) and hCA II, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glucosidase (α-Glu) inhibitory activities. The ChE inhibitory activities of the new PEPPSI-Pd-NHC complexes bearing the 4-hydroxyphenylethyl group (1a-e) against α-Glu, AChE, and BChE were determined by the Tao and Ellman methods. The results indicated that all the synthetic complexes exhibited potent inhibitory activities against all targets as compared to the standard inhibitors, revealed by IC50 values. The Ki values of the new PEPPSI-Pd-NHC complexes 1a-e for hCA I, hCA II, AChE, BChE, and α-Glu were obtained in the ranges of 18.98-32.65, 22.95-38.13, 3.67-11.65, 4.09-9.36, 186.92-287.45 µM, respectively. Among the synthesized complexes, the most potent complexes were 1c toward hCA I and II with Ki values 18.98 and 22.95 µM, and 1d toward AChE and BChE with Ki = 3.67 and 4.09 µM, respectively.