H2O2-reactivity of copper(II) complexes supported by tris[(pyridin-2-yl)methyl]amine ligands with 6-phenyl substituents.
The structure and H(2)O(2)-reactivity of a series of copper(II) complexes supported by tris[(pyridin-2-yl)methyl]amine (TPA) derivatives having a phenyl group at the 6-position of pyridine donor group(s) [(6-phenylpyridin-2-yl)methyl]bis[(pyridin-2-yl)methyl]amine (Ph(1)TPA), bis[(6-phenylpyridin-2-yl)methyl][(pyridin-2-yl)methyl]amine (Ph(2)TPA), and tris[(6-phenylpyridin-2-yl)methyl]amine (Ph(3)TPA) have systematically been examined to get insights into the aromatic substituent (6-Ph) effects on the coordination chemistry of TPA ligand system. The X-ray crystallographic analyses have revealed that [Cu(II)(TPA)(CH(3)CN)](ClO(4))(2) (CuTPA) and [Cu(II)(Ph(3)TPA)(CH(3)CN)](ClO(4))(2) (3) exhibit a trigonal bipyramidal structure, whereas [Cu(II)(Ph(1)TPA)(CH(3)CN)](ClO(4))(2) (1) shows a slightly distorted square pyramidal structure and [Cu(II)(Ph(2)TPA)(CH(3)CN)](ClO(4))(2) (2) has an intermediate structure between trigonal bipyramidal and square pyramidal. On the other hand, the UV-vis and ESR data have suggested that all the copper(II) complexes have a similar trigonal bipyramidal structure in solution. The redox potentials of CuTPA, 1, 2, and 3 have been determined as E(1/2) = -0.34, -0.28, -0.16, and -0.04 mV vs Ag/AgNO(3), respectively, demonstrating that introduction of each 6-Ph group causes positive shift of E(1/2) about 0.1 V. Notable difference in H(2)O(2)-reactivity has been found among the copper(II) complexes. Namely, CuTPA and 1 afforded mononuclear copper(II)-hydroperoxo complexes CuTPA-OOH and 1-OOH, respectively, whereas complex 2 provided bis(mu-oxo)dicopper(III) complex 2-oxo. On the other hand, copper(II) complex 3 was reduced to the corresponding copper(I) complex 3(red). On the basis of the H(2)O(2)-reactivity together with the X-ray structures and the redox potentials of the copper(II) complexes, the substituent effects of 6-Ph are discussed in detail.
Kunishita
Atsushi
A
Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
Kubo
Minoru
M
Ishimaru
Hirohito
H
Ogura
Takashi
T
Sugimoto
Hideki
H
Itoh
Shinobu
S
D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D011336:Probability; D011725:Pyridines / Q000737:chemistry*; D013053:Spectrophotometry; D013755:Tetradecanoylphorbol Acetate / Q000737:chemistry
D008024:Ligands; D010636:Phenols; D011725:Pyridines; C519446:tris(2-methylpyridine)amine; D003300:Copper; D006861:Hydrogen Peroxide; D013755:Tetradecanoylphorbol Acetate