A linear correlation between energy of LMCT band and oxygenation reaction rate of a series of catecholatoiron(III) complexes: initial oxygen binding during intradiol catechol oxygenation.
The oxygen reactivity of catecholatoiron(III) complexes has been examined using a series of catecholate ligands as the substrate. All the complexes examined here, [Fe(III)(TPA)(R-Cat)]BPh(4) (1-9) (TPA: tris(pyridin-2-ylmethyl)amine; R-Cat: substituted catecholate ligand, R=3,5-(t)Bu(2) (1), 3,6-(t)Bu2 (2), 3,5-Me2 (3), 3,6-Me2 (4), 4-(t)Bu (5), 4-Me (6), H (7), 4-Cl (8) and 3-Cl (9)), exclusively afforded the intradiol cleaving products of the catecholate ligands upon exposure to O2. It was revealed that 1-7 can be categorized into two classes based on their electrochemical properties; i.e., the complexes having the dialkyl-substituted (group A) and the mono- or non-substituted (group B) catecholate ligands. In spite of their classification, these two groups show a linear correlation between the logarithm of the reaction rate constant with O2 and the energy of the catecholate-to-iron(III) LMCT band, although 2 shows a large negative deviation from the correlation line. Based on this LMCT-energy dependent reactivity of 1 and 3-9 as well as the very low reactivity of 2, we have discussed on the mechanisms of the reaction of [Fe(III)(TPA)(R-Cat)]BPh4 with O2.
Hitomi
Yutaka
Y
Department of Molecular Engineering, Kyoto University, Kyoto Daigaku Katsura, Nishikyo-ku, Kyoto 6158510, Japan.
Yoshida
Masato
M
Higuchi
Masakazu
M
Minami
Hisataka
H
Tanaka
Tsunehiro
T
Funabiki
Takuzo
T
D002396:Catechols / Q000737:chemistry*; D018360:Crystallography, X-Ray; D049308:Dioxygenases / Q000737:chemistry; D004563:Electrochemistry; D004735:Energy Transfer; D005290:Ferric Compounds / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*
D002396:Catechols; D005290:Ferric Compounds; D008024:Ligands; D009942:Organometallic Compounds; D049308:Dioxygenases; C034221:catechol; D010100:Oxygen