Solution Versus Solid-State Conformation of Group-12 Metal-Complexes of Active Aldehyde Derivatives of Thiamine

 
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1992 (EN)
Solution Versus Solid-State Conformation of Group-12 Metal-Complexes of Active Aldehyde Derivatives of Thiamine (EN)

Louloudi, M. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Louloudi, M. (EN)

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. (EN)

nuclear-magnetic-resonance (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Journal of the Chemical Society-Dalton Transactions (EN)

English

1992

<Go to ISI>://A1992HQ62000011



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