TY - JOUR
T1 - Functional metallomacrocycles and their polymers. 25. Kinetics and mechanism of the biomimetic oxidation of thiol by oxygen catalyzed by homogeneous (polycarboxyphthalocyaninato)metals
AU - Shirai, H.
AU - Tsuiki, H.
AU - Masuda, E.
AU - Koyama, T.
AU - Hanabusa, K.
AU - Kobayashi, N.
PY - 1991/1/1
Y1 - 1991/1/1
N2 - The oxidation of 2-mercaptoethanol (RSH) catalyzed by (polycarboxyphthalocyaninato)metal acid (M-papc, M = Fe(III), Co(II), Ni(II), Cu(II), pa = -(COOH)2, -(COOH)4, -(COOH)8) in the presence of molecular oxygen has been studied in aqueous homogeneous solution at pH 7.0 and at 25°C. The catalytic effects of M-papc have been determined the oxygen consumption in the reaction mixture with a Warburg respirometer. The central metal ions and the number of carboxylate ions on M-papc affected the catalytic activities for the aerobic oxidation of RSH. (Octacarboxyphthalocyaninato)iron(III) and -cobalt(II) are remarkably effective catalysts. (Dicarboxyphthalocyaninato)metals and Ni(II)- as well as Cu(II)-phthalocyanine derivatives are less effective catalysts. The kinetics of the aerobic oxidation catalyzed by (octacarboxyphthalocyaninato)iron(III) and -cobalt(II) have been characterized in terms of a bisubstrate Michaelis-Menten rate law (k5 = 600-800 min-1, at pH 7.0, 25°C). The rate law and spectral experiments indicate that the catalyzed reactions proceed via the formation of a ternary activated complex where RS- and O2 reversibly coordinate with the central metal on the phthalocyanine rings. The activation parameters were also determined for this reaction at pH 7.0 and at 25°C. The catalytic activities followed the order of Co(II)-oapc > Fe(III)-oapc > Co(II)-tapc = Fe(III)-tapc. Differences in catalytic ability have been explained in terms of the aggregation and spin state of metallophthalocyanine derivatives in aqueous solution at pH 7.0. The (tetracarboxyphthalocyaninato)cobalt(II) covalently bound to poly(2-vinylpyridine-co-styrene), despite of being a heterogeneous system, is a remarkably effective catalyst (k5 = 2210 min-1) because of polymer effects.
AB - The oxidation of 2-mercaptoethanol (RSH) catalyzed by (polycarboxyphthalocyaninato)metal acid (M-papc, M = Fe(III), Co(II), Ni(II), Cu(II), pa = -(COOH)2, -(COOH)4, -(COOH)8) in the presence of molecular oxygen has been studied in aqueous homogeneous solution at pH 7.0 and at 25°C. The catalytic effects of M-papc have been determined the oxygen consumption in the reaction mixture with a Warburg respirometer. The central metal ions and the number of carboxylate ions on M-papc affected the catalytic activities for the aerobic oxidation of RSH. (Octacarboxyphthalocyaninato)iron(III) and -cobalt(II) are remarkably effective catalysts. (Dicarboxyphthalocyaninato)metals and Ni(II)- as well as Cu(II)-phthalocyanine derivatives are less effective catalysts. The kinetics of the aerobic oxidation catalyzed by (octacarboxyphthalocyaninato)iron(III) and -cobalt(II) have been characterized in terms of a bisubstrate Michaelis-Menten rate law (k5 = 600-800 min-1, at pH 7.0, 25°C). The rate law and spectral experiments indicate that the catalyzed reactions proceed via the formation of a ternary activated complex where RS- and O2 reversibly coordinate with the central metal on the phthalocyanine rings. The activation parameters were also determined for this reaction at pH 7.0 and at 25°C. The catalytic activities followed the order of Co(II)-oapc > Fe(III)-oapc > Co(II)-tapc = Fe(III)-tapc. Differences in catalytic ability have been explained in terms of the aggregation and spin state of metallophthalocyanine derivatives in aqueous solution at pH 7.0. The (tetracarboxyphthalocyaninato)cobalt(II) covalently bound to poly(2-vinylpyridine-co-styrene), despite of being a heterogeneous system, is a remarkably effective catalyst (k5 = 2210 min-1) because of polymer effects.
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U2 - 10.1021/j100154a073
DO - 10.1021/j100154a073
M3 - Article
AN - SCOPUS:0001072390
VL - 95
SP - 417
EP - 423
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
SN - 0022-3654
IS - 1
ER -