OA:W3012417436<\/a><\/p>\nAuthors:<\/h4>\n
Wen\u2010Yuan Hsieh<\/p>\n
Abstract:<\/h4>\n
Photosynthetic water oxidation to form dioxygen occurs using a manganese cluster in the oxygen evolving complex (OEC). The higher oxidation states (S3<\/sub> and S4<\/sub>) of the Mn cluster are still unclear. To examine the viability of a MnIV\/V2<\/sub>=O complex as a model for the S4<\/sub> state, [MnIII\/IV2<\/sub>(2-OHsalpn) 2<\/sub>]+ (2-OHsalpn = N,N’-bis(salicylimino)-1,3-diaminopropan-2-ol) was oxidized at -78°C by meta-chloroperoxobenzoic acid (m-CPBA) to form [MnV\/IV2<\/sub>=O(2-OHsalpn) 2<\/sub>]+. MnV=O reactivity was probed using a cyclohexene assay. Cyclohexene oxide was detected by GC-mass spectroscopy from the reaction of [MnIII\/IV 2<\/sub>(2-OHsalpn)2<\/sub>]+ with m-CPBA in the presence of cyclohexene. The reaction proceeded for 20 turnovers. CO2<\/sub>(g) was observed from the same reaction in the absence of cyclohexene. The kinetics of the reaction in the absence of cyclohexene was followed by stopped-flow UV-Visible, freeze-quench EPR and XANES spectroscopies. Rapid formation (30 ms after the reaction was initiated) of a radical species and a MnIV\/IV2<\/sub> complex were detected. The generated MnV=O reacts with the product (m-chlorobenzoate) to form a radical then liberates CO2<\/sub>(g). Parallel mode EPR spectra also detected a multiline signal, which is identified as a MnIV 4<\/sub> tetramer. The spectral features are very similar to the S1<\/sub> state; however, the smaller spectral width indicates that the MnIV 4<\/sub> model has a higher oxidation states than found in S 1<\/sub>. The proposed reaction mechanism suggests initial oxidation of Mn IV\/IV2<\/sub> to MnIV\/V2<\/sub>=O, which can oxidize benzoate forming an organic radical species and a MnIV\/IV 2<\/sub> complex. Alternatively the MnIV\/V2<\/sub>=O can rapidly comproportionate with a MnIII\/IV2<\/sub> species forming the MnIV4<\/sub> tetramer. Despite previous literature reports that treat the manganyl group solely as a two-electron, oxo transfer moiety, this work demonstrates for the first time that the manganyl group can competitively undergo single electron reduction reactions.<\/p>\n","protected":false},"excerpt":{"rendered":"DOI: OA:W3012417436 Authors: Wen\u2010Yuan Hsieh Abstract: Photosynthetic water oxidation to form dioxygen occurs using a manganese cluster in the oxygen evolving complex (OEC). The higher oxidation states (S3 and S4) of the Mn cluster are still unclear. To examine the viability of a MnIV\/V2=O complex as a model for the S4 state, [MnIII\/IV2(2-OHsalpn) 2]+ (2-OHsalpn […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-624","post","type-post","status-publish","format-standard","hentry","category-freeze-quench"],"_links":{"self":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/624","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=624"}],"version-history":[{"count":0,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/624\/revisions"}],"wp:attachment":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=624"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=624"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=624"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}