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Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes
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SYSNO ASEP 0428492 Druh ASEP J - Článek v odborném periodiku Zařazení RIV J - Článek v odborném periodiku Poddruh J Článek ve WOS Název Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes Tvůrce(i) Schweinfurth, D. (DE)
Rechkemmer, Y. (DE)
Hohloch, S. (DE)
Deibel, N. (DE)
Peremykin, I. (DE)
Fiedler, Jan (UFCH-W) RID, ORCID
Marx, R. (DE)
Neugebauer, P. (DE)
van Slageren, J. (DE)
Sarkar, B. (DE)Zdroj.dok. Chemistry - A European Journal. - : Wiley - ISSN 0947-6539
Roč. 20, č. 12 (2014), s. 3475-3486Poč.str. 12 s. Jazyk dok. eng - angličtina Země vyd. DE - Německo Klíč. slova bridging ligands ; mixed-valent compounds ; non-innocent ligands Vědní obor RIV CF - Fyzikální chemie a teoretická chemie CEP GA203/09/0705 GA ČR - Grantová agentura ČR Institucionální podpora UFCH-W - RVO:61388955 UT WOS 000332747400030 EID SCOPUS 84896388055 DOI 10.1002/chem.201302858 Anotace The complexes [{(tmpa)Co(II) }2 (mu-L(1) )(2-) ](2+) (1(2+) ) and [{(tmpa)Co(II) }2 (mu-L(2) )(2-) ](2+) (2(2+) ), with tmpa=tris(2-pyridylmethyl)amine, H2 L(1) =2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, and H2 L(2) =2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone, were synthesized and characterized. Structural analysis of 2(2+) revealed a distorted octahedral coordination around the cobalt centers, and cobalt-ligand bond lengths that match with high-spin Co(II) centers. Superconducting quantum interference device (SQUID) magnetometric studies on 1(2+) and 2(2+) are consistent with the presence of two weakly exchange-coupled high-spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 1(2+) and ferromagnetic for 2(2+) . Both complexes exhibit several one-electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near-IR spectroelectrochemistry. For 1(2+) , it was possible to chemically isolate the pure forms of both the one-electron oxidized mixed-valent 1(3+) and the two-electron oxidized isovalent 1(4+) forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin-state of the molecule. In contrast to 2(2+) , for 1(4+) the metal-ligand distances and the distances within the quinonoid ligand point to the existence of two low-spin Co(III) centers, thus showing the innocence of the quintessential non-innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two-electron oxidation, which confirms the change in spin state associated with the electron-transfer steps. Pracoviště Ústav fyzikální chemie J.Heyrovského Kontakt Michaela Knapová, michaela.knapova@jh-inst.cas.cz, Tel.: 266 053 196 Rok sběru 2015
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