Silver N-heterocyclic carbene complexes bearing fluorinated benzyl group: Synthesis, characterization, crystal structure, computational studies, and inhibitory properties against some metabolic enzymes

Abstract

A series of the silver N-heterocyclic carbene (NHC) complexes have been synthesized from the reactions between benzimidazolium salts bearing fluorinated benzyl group and Ag2O via the deprotonation method. All Ag(I)NHC complexes were characterized by known spectroscopic techniques (H-1 nuclear magnetic resonance [NMR], C-13 NMR, and Fourier transform infrared [FT-IR]) and elemental analysis. The molecular structures of the two complexes were unambiguously elucidated through single-crystal X-ray diffraction analysis. Namely, X-ray studies show that the coordination geometry around the Ag(I) atom in the case of complex 2c is revealed to be almost linear with C-Ag-Cl angle, whereas in complex 2e, it appears as a nonlinear structure. The inhibitory profiles of these new complexes are investigated on some metabolic enzymes. Representatively, the most potent complex against human carbonic anhydrase isoenzymes I and II (hCAs I and II), 2d, was 1.8 times more potent than standard inhibitor acetazolamide against hCAs I and II. On the other hand, complexes 2c and 2b as most potent compounds against both cholinesterase enzymes was around 5 and 1.6 times more potent than tacrine against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively. The most active alpha-glucosidase inhibitor 2d had similar activity to acarbose as a standard inhibitor. Furthermore, it confirms its in vitro studies as a result of molecular docking studies for each enzyme with (i) binding energy and inhibition constant values and (ii) the definition of the best conformation and nonbonding interactions of the related complexes (2b, 2c, and 2d) against the different target proteins.