title: 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(O(2))(2)(H(2)O)](-) or [OV(O(2))(2)(HOD)](-) or [OV(O(2))(2)(D(2)O)](-) (bpV) have been explored by a combination of multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, heteronuclear single quantum coherence (HSQC) and variable temperature NMR in a 0.15 mol L(-1) NaCl D(2)O 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(O(2))(2)LL'](-) (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-NH(2)-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 NH(4)[OV(O(2))(2)(pprd)]·2H(2)O 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-NH(2)-pprd, 2-Et-pprd, or Isomer A in solution for 6'-Me-pprd.
authors.affiliation: Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan Province, School of Chemistry and Chemical Engineering Hunan University of Science and Technology, Xiangtan, China.
authors.forename: Xian-Yong
authors.initials: XY
authors.lastname: Yu
authors.forename: Ping-Gui
authors.initials: PG
authors.lastname: Yi
authors.forename: Dan-Hong
authors.initials: DH
authors.lastname: Ji
authors.forename: Bi-Rong
authors.initials: BR
authors.lastname: Zeng
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Li
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
mesh_terms: D006860:Hydrogen Bonding; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D012996:Solutions; D014638:Vanadates / Q000737:chemistry*
chemical_list: C574069:4-(pyridin-2-yl)pyrimidine; D008024:Ligands; D009942:Organometallic Compounds; D010545:Peroxides; D011725:Pyridines; D011743:Pyrimidines; D012996:Solutions; C091767:diperoxovanadate; D014638:Vanadates