Structures and electronic properties of the catecholatoiron complexes in relation to catechol dioxygenases: chlorocatecholatoiron complexes are compared to the 3,5-di-tert-butylcatecholatoiron complex in the solid state and in solution.
Chlorocatecholatoiron complexes, [Fe(TPA)(4Cl[bond]Cat)]BPh(4) and [Fe(TPA)(3Cl[bond]Cat)]BPh(4), (4Cl[bond]Cat and 3Cl[bond]Cat: 4- and 3-chlorocatecholates, respectively; TPA: tris(2-pyridylmethyl)amine) were isolated as intermediates for the oxygenative cleavage of chlorocatechols by nonheme iron complexes. Geometric structures of these complexes together with [Fe(TPA)(DTBC)]BPh(4) (DTBC: 3,5-di-tert-butylcatecholate) as reference were analyzed by X-ray absorption spectroscopy (EXAFS) in the solid state and in solution. Structure of the DTBC complex in the solid state was shown to be noticeably different from the other complexes as seen in the magnetic susceptibility and spectroscopic data. Electronic and magnetic properties of these complexes were studied by X-ray absorption (XANES), electronic (VIS) and ESR spectroscopies, and magnetic susceptibility. Electron transfer from the catecholate ligand to the Fe(III) center was indicated by the Fe[bond]K edge values in XANES spectra and by the LMCT bands in electronic spectra. Magnetic susceptibility and ESR data indicated that at low temperatures the complexes are in equilibrium between the low (S=1/2) and high-spin (S=5/2) ferric states with the latter component increasing with temperature. Remarkable differences between the spin states in solid and in solution were observed with the DTBC complex.
Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan. funabiki@scl.kyoto-u.ac.jp
Takuzo
T
Funabiki
Atsushi
A
Fukui
Yutaka
Y
Hitomi
Masakazu
M
Higuchi
Takashi
T
Yamamoto
Tsunehiro
T
Tanaka
Fumito
F
Tani
Yoshinori
Y
Naruta
D002396:Catechols / Q000737:chemistry*; D017606:Chlorine Compounds / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D058085:Iron Compounds / Q000737:chemistry*; D015394:Molecular Structure; D010105:Oxygenases / Q000737:chemistry*; D012996:Solutions; D013696:Temperature
D002396:Catechols; D017606:Chlorine Compounds; D058085:Iron Compounds; D012996:Solutions; D010105:Oxygenases