A molecular orbital study of C-H…Cl~-and N-H…Cl~-hydrogen bonds.Inferences on selected metal complexes and on protein C1C Cl~-channels

摘要

Hydrogen bond type interactions X-H…Y~-(X:C,N,O;Y:Cl)for systems that contain 1,3-imidazole(IM),1,3-pyrimidine(PYM),N-methylacetamide(MAA),methylammonium(MA),methylamine(MAB),l-hydroxy-4-methylbenzene(HMB),N-methylguanidinium(MGU),methanol(MeOH),have been investigated via the methods of density functional theory(DFT)at the B3LYP functional level and ab initio MP2,by using mostly the standard 6-31G~(**)and 6-31+G~(**)basis sets.The study helps in understanding structural aspects of at least Re/Ru-imidazole,Ru-pyrimidine and Ru-arene complexes and allows to evaluate the adduct formation energy(electronic),for species of the type M(IM)N-H-Cl~-,M(IM/PYM)C-H-Cl~-,whose upper limits are ca.-24 and-10 kcal at gas phase.Computed structural and energy parameters help also in evaluating the mechanism of extrusion of Cr~-anions in certain C1C Chloride channels from membrane proteins.The hydrogen bond formation energy for selected aminoacid residues with Cl~-ranges ca.-106 to-15 kcal mol~(-1).Owing to the predominance of CONH peptide bonds in every protein system,the formation of the C(=O)-N-H…C1~-hydrogen bond(DELTAE_(el)approx=-21 kcal)is often revealed in X-ray structures of protein…chloride adducts.