Issue 13, 2012

Study of the coordination and solution structures for the interaction systems between diperoxidovanadate complexes and 4-(pyridin-2-yl)pyrimidine-like ligands

Abstract

To understand the substitution effects of 4-(pyridin-2-yl)pyrimidine (pprd) on the coordination reaction equilibria, the interactions between a series of the pprd-like ligands and [OV(O2)2(H2O)] or [OV(O2)2(HOD)] or [OV(O2)2(D2O)] (bpV) have been explored by a combination of multinuclear (1H, 13C, and 51V) magnetic resonance, heteronuclear single quantum coherence (HSQC) and variable temperature NMR in a 0.15 mol L−1 NaCl D2O solution that mimics physiological conditions. The direct NMR data are reported for the first time. Competitive coordination interactions result in a series of new hepta-coordinated peroxidovanadate species [OV(O2)2LL′] (LL′ = pprd-like chelating ligands). The equilibrium constants for the products between bpV and the pprd-like ligands show that the relative affinity of the ligands is pprd ≈ 2-NH2-pprd > 2-Me-pprd > 2-Et-pprd > 4-(6-methylpyridin-2-yl)pyrimidine (abbr. 6′-Me-pprd). When the ligand is pprd, a pair of isomers (Isomer A and B) are observed in aqueous solution, which are attributed to the different types of coordination modes between the metal and the ligands, while the crystal structure of NH4[OV(O2)2(pprd)]·2H2O has the same coordination structure as Isomer A. For substituted pprd ligands, however, only one type of structure (Isomer A or B ) is observed in solution. These results demonstrate that, when the aromatic ring has a substitution group, both the steric effect (from the alkyl) and hydrogen bonding (from the amine) can affect the coordination reaction equilibrium to prevent the appearance of either Isomer B in solution for the ligands 2-Me-pprd, 2-NH2-pprd, 2-Et-pprd, or Isomer A in solution for 6′-Me-pprd.

Graphical abstract: Study of the coordination and solution structures for the interaction systems between diperoxidovanadate complexes and 4-(pyridin-2-yl)pyrimidine-like ligands

Supplementary files

Article information

Article type
Paper
Submitted
03 Dec 2011
Accepted
06 Jan 2012
First published
22 Feb 2012

Dalton Trans., 2012,41, 3684-3694

Study of the coordination and solution structures for the interaction systems between diperoxidovanadate complexes and 4-(pyridin-2-yl)pyrimidine-like ligands

X. Yu, P. Yi, D. Ji, B. Zeng, X. Li and X. Xu, Dalton Trans., 2012, 41, 3684 DOI: 10.1039/C2DT12334G

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