Structural characterization and reactivity of gamma-octamolybdate functionalized by proline.
The reaction of molybdate and dl-proline at pH 3.4 results in the formation of a Na(4)[Mo(8)O(26)(proO)(2)] x 22H(2)O complex (pro=proline) in which two proline ligands are attached to molybdenum(VI) ions via monodentate coordination of the carboxylate groups. The structure of the complex was determined by single crystal X-ray diffraction and by combination of (1)H, (13)C and (95)Mo NMR spectroscopy techniques in solution. The structure of the complex is strongly dependent on the pH. At native pH 3.4 the octamolybdate-type structure seems to be present in solution, but the increase of pH to 5.8 resulted in a rearrangement of the structure to a heptamolybdate-type structure. At physiological pH, the polyoxometalate framework was completely dissociated into the monomeric MoO(4)(2-) unit. The reactivity of the Na(4)[Mo(8)O(26)(proO)(2)] x 22H(2)O towards the hydrolysis of ATP was tested at different pH values. While in solution at pH 3.4 the hydrolysis proceeded to yield AMP (adenosine monophosphate) and ADP (adenosine diphosphate) in nearly equal amounts, reaction mixture at pH 5.8 gave ADP as the only product of hydrolysis after 24h of reaction. At neutral pH, the hydrolysis of ATP was slower, but it proceeded to yield 75% of ADP after 48 h of reaction.
Cartuyvels
Els
E
Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
Van Hecke
Kristof
K
Van Meervelt
Luc
L
Görller-Walrand
Christiane
C
Parac-Vogt
Tatjana N
TN
D000244:Adenosine Diphosphate / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008024:Ligands; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry* / Q000494:pharmacology*; D011392:Proline / Q000737:chemistry*
D008024:Ligands; C044659:molybdate; D000244:Adenosine Diphosphate; D008982:Molybdenum; D011392:Proline