- New ruthenium(II) heteroleptic complexes containing the 4-(2-pyridyl)pyrimidine ligand with amine and amino acid substituents
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New 4-(2-pyridyl)pyrimidines (L) have been synthesized in high yields by condensing enaminones with the appropriate carboxamidine or guanidine under basic conditions. These asymmetric bidentate diimine ligands coming from a one-step functionalization of amine and amino acid groups were complexed to ruthenium to obtain new heteroleptic complexes of type [Ru(bpy)2(L)]2+. The ligands and complexes have been characterized by usual analytical methods, and the crystallographic study of one complex has been performed. Their spectroscopic and electrochemical properties have been investigated. ZINDO Calculations show that in the MLCT excited state the electron is mainly localized on the pyridylpyrimidine ligand. On the basis of electrochemical data, the first reduction potential of the complexes has been assigned to the redox couple involving this ligand.
- Ait-Haddou, Hassan,Bejan, Elena,Daran, Jean-Claude,Balavoine, Gilbert G. A.,Berruyer-Penaud, Florence,Bonazzola, Lydia,Smaoui-Chaabouni, Henda,Amouyal, Edmond
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- Study of the coordination and solution structures for the interaction systems between diperoxidovanadate complexes and 4-(pyridin-2-yl)pyrimidine-like ligands
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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(O 2)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 D 2O 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)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. The Royal Society of Chemistry 2012.
- Yu, Xian-Yong,Yi, Ping-Gui,Ji, Dan-Hong,Zeng, Bi-Rong,Li, Xiao-Fang,Xu, Xin
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supporting information; experimental part
p. 3684 - 3694
(2012/05/07)
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