Solution Versus Solid-State Conformation of Group-12 Metal-Complexes of Active Aldehyde Derivatives of Thiamine (Journal article)

Louloudi, M./ Hadjiliadis, N./ Butler, I. S.

Molar conductances in water and dimethylformamide and C-13 NMR spectra in D2O and (CD3)2SO solutions and solid-state C-13 cross polarization magic angle spinning NMR spectra have been measured for the chloride salts of 2-(alpha-hydroxybenzyl)thiamine (hbt), 2-(alpha-hydroxycyclohexylmethyl)-thiamine (hcmt), their protonated forms [hbt]Cl.HCl and [hcmt]Cl.HCl and zwitterionic complexes of the type [M(hbt)Cl3] and [M(hcmt)Cl3] (M = Zn, Cd or Hg). The data affords good evidence for bonding of the metals to the N(1') atom of the pyrimidine moieties in the ligands, as well as of the S conformation of the ligands in solution. The small chemical shifts observed for the carbon atoms situated adjacent to the N(1') site [C(2'), C(6') and 2'-CH3] in the solid-state and solution C-13 NMR spectra of the complexes are attributed to the synergic interaction of metal complexation which causes a downfield shift and the accumulation of negative charge at the same position due to [MCl3]- which leads to an opposing upfield shift. The Hg-199 NMR spectra of [Hg(hbt)Cl3] and [Hg(hcmt)Cl3] in (CD3)2SO further substantiate these conclusions. Overall, the results strongly support earlier suggestions for the role of metal ions in the enzymatic action of thiamine.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: nuclear-magnetic-resonance,molecular-structure,crystal-structure,c-13 nmr,chloride hydrochloride,stereochemistry,mercury(ii),vitamin-b1,catalysis
ISSN: 0300-9246
Link: <Go to ISI>://A1992HQ62000011
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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