title: Tetracopper Assembly Complexes Comprised of One Dimetallic Core and Two Monometallic Auxiliaries: Intramolecular Electron-Transfer Relevant to Multicopper Oxidases.
abstract: Two tetracopper assembly complexes, comprised of one dimetallic di(3-iminomethylsalicylato)dicopper(II) core and two monometallic copper(II) auxiliaries attached to the imino nitrogens of the dinuclear core through an alkane chain, have been prepared. [Cu(4)(L(1))](PF(6))(4).2CH(3)CN.3H(2)O (1) has di(2-pyridylmethyl)aminecopper(II) as the monometallic auxiliary, and [Cu(4)(L(2))](ClO(4))(4).CH(3)OH (2) has 1,4,8,11-tetraazacyclotetradecanecopper(II) as the auxiliary. Assembly 1 in acetonitrile shows a two-electron reduction at -0.08 V (vs SCE) followed by a one-electron reduction at -0.42 V. Together with EPR studies for electrolyzed solutions, it is shown that the two monometallic auxiliaries are reduced at -0.08 V, followed by an intramolecular electron transfer from one of the reduced auxiliaries to the dimetallic core and by the second reduction at the resulting monometallic Cu(II) center at -0.42 V: {Cu(II)-Cu(2)(II,II)-Cu(II)}/{Cu(I)-Cu(2)(II,II)-Cu(I)} --> {Cu(I)-Cu(2)(I,II)-Cu(II)}/{Cu(I)-Cu(2)(I,II)-Cu(I)}. The CV of 2 in DMSO shows two couples at -0.68 and -0.99 V attributable to the stepwise reductions: {Cu(II)-Cu(2)(II,II)-Cu(II)}/{Cu(II)-Cu(2)(I,II)-Cu(II)}/{Cu(I)-Cu(2)(I,II)-Cu(II)}. Assembly 1 is reduced with ascorbic acid to the {Cu(I)-Cu(2)(I,II)-Cu(I)} species, whereas 2 is not reduced with ascorbic acid. The relevance of the intramolecular electron transfer observed for 1 to multicopper oxidases is discussed.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashiku, Fukuoka 812, Japan, Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K., and Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Yamanaka
authors.forename: Hisashi
authors.initials: H
authors.lastname: Okawa
authors.forename: Ken-ichiro
authors.lastname: Motoda Ki
authors.forename: Masami
authors.initials: M
authors.lastname: Yonemura
authors.forename: David E.
authors.initials: DE
authors.lastname: Fenton
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Ebadi
authors.forename: A. B. P.
authors.initials: AB
authors.lastname: Lever