PEPPSI type Pd(II)NHC complexes bearing chloro-/fluorobenzyl group: Synthesis, characterization, crystal structures, α-glycosidase and acetylcholinesterase inhibitory properties

Abstract

This work reported the synthesis of a new PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) type Pd(II)N-heterocyclic carbene (NHC) complexes bearing halo-benzyl (4-florobenzyl and 2-chloro-4-florobenzyl) group. These new complexes were synthesized from the florobenzyl / chlorofluorobenzyl substituted benzimidazolium salts, PdCl2 and pyridine. Characterizations of all the synthesized complexes were done using elemental analysis, 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The molecular and crystal structures of the new PEPPSI type Pd(II)NHC complexes were determined by single-crystal X-ray diffraction method. X-ray studies show that molecular structures of three complexes comprise a palladium(II) atom with a slightly distorted square-planar coordination environment. These synthesized salts were found to be effective inhibitors for the α-glycosidase, and acetylcholinesterase (AChE) enzyme with Ki values in the range of 27.36 ± 5.06–124.88 ± 18.05 µM for α-glycosidase, and 0.78 ± 0.11–4.34 ± 1.02 µM for AChE, respectively. The significant group of drugs currently utilized for the therapy of Alzheimer's disease (AD) is acetylcholinesterase/cholinesterase inhibitor compounds. The first cholinesterase inhibitor licensed for symptomatic therapy of AD was tacrine. Inhibition acts of α-glycosidase enzyme by inhibitors tend to slow the breakdown and release of sugar molecules into the bloodstream and can be utilized as therapeutic factors in the therapy of obesity and diabetes.