Localization and Delocalization in a Mixed-Valence Dicopper Helicate

John C. Jeffery, Thomas Riis-Johannessen, Callum J. Anderson, Christopher J. Adams, Adam Robinson, Stephen P. Argent, Michael D. Ward, Craig R. Rice

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Abstract

The coordination chemistry of the tetradentate pyridyl-thiazole (py-tz) N-donor ligand 6,6′-bis(4-phenylthiazol-2-yl)-2,2′-bipyridine (L1) has been investigated. Reaction of L1 with equimolar copper(II) ions results in the formation of the single-stranded mononuclear complex [Cu(L1)(ClO4)2] (1), whereas reaction with copper(I) ions results in the double-stranded dinuclear helicate [Cu 2(L1)2][PF6]2 (2). Both complexes were characterized by X-ray crystallography, UV-vis spectroscopy, and electrospray ionization mass spectroscopy (as well as 1H NMR spectroscopy for diamagnetic 2). Complex 2 is redox-active and, upon one-electron oxidation, forms the stable tricationic mixed-valence helicate [Cu2(L1)2]3+ (3). This species can also be prepared in situ by combining [Cu(MeCN)4][BF4], [Cu-(H2O)6][BF4]2, and L1 in a 1:1:2 ratio in nitromethane. X-ray crystallographic analysis of 3 provides structural evidence for the presence of an internuclear Cu-Cu bond, with an even distribution of spin density across the two Cu centers. Room-temperature UV-vis spectroscopy is consistent with this finding; however, frozen-glass EPR spectroscopic investigations suggest solvatochromic behavior at 110 K, with the [Cu2]3+ core varying from localized to delocalized depending on the solvent polarity.

Original languageEnglish
Pages (from-to)2417-2426
Number of pages10
JournalInorganic Chemistry
Volume46
Issue number7
DOIs
Publication statusPublished - 2 Apr 2007

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Jeffery, J. C., Riis-Johannessen, T., Anderson, C. J., Adams, C. J., Robinson, A., Argent, S. P., ... Rice, C. R. (2007). Localization and Delocalization in a Mixed-Valence Dicopper Helicate. Inorganic Chemistry, 46(7), 2417-2426. https://doi.org/10.1021/ic061504m