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Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable Ferromagnetic Metal–Organic Wires

AuthorsPardo, Emilio; Ferrando-Soria, J.; Cañadillas-Delgado, Laura; Pasán, Jorge; Ruiz-Pérez, Catalina
Issue Date2010
CitationChemistry - A European Journal 16(43): 12838-12851 (2010)
AbstractDouble-stranded copper(II) string complexes of varying nuclearity, from di- to tetranuclear species, have been prepared by the CuII-mediated self-assembly of a novel family of linear homo- and heteropolytopic ligands that contain two outer oxamato and either zero (1 b), one (2 b), or two (3 b) inner oxamidato donor groups separated by rigid 2-methyl-1,3-phenylene spacers. The X-ray crystal structures of these CuIIn complexes (n=2 (1 d), 3 (2 d), and 4 (3 d)) show a linear array of metal atoms with an overall twisted coordination geometry for both the outer CuN2O2 and inner CuN4 chromophores. Two such nonplanar all-syn bridging ligands 1 b–3 b in an anti arrangement clamp around the metal centers with alternating M and P helical chiralities to afford an overall double meso-helicate-type architecture for 1 d–3 d. Variable-temperature (2.0–300 K) magnetic susceptibility and variable-field (0–5.0 T) magnetization measurements for 1 d–3 d show the occurrence of S=nSCu (n=2–4) high-spin ground states that arise from the moderate ferromagnetic coupling between the unpaired electrons of the linearly disposed CuII ions (SCu=1/2) through the two anti m-phenylenediamidate-type bridges (J values in the range of +15.0 to 16.8 cm−1). Density functional theory (DFT) calculations for 1 d–3 d evidence a sign alternation of the spin density in the meta-substituted phenylene spacers in agreement with a spin polarization exchange mechanism along the linear metal array with overall intermetallic distances between terminal metal centers in the range of 0.7–2.2 nm. Cyclic voltammetry (CV) and rotating-disk electrode (RDE) electrochemical measurements for 1 d–3 d show several reversible or quasireversible one- or two-electron steps that involve the consecutive metal-centered oxidation of the inner and outer CuII ions (SCu=1/2) to diamagnetic CuIII ones (SCu=0) at relatively low formal potentials (E values in the range of +0.14 to 0.25 V and of +0.43 to 0.67 V vs. SCE, respectively). Further developments may be envisaged for this family of oligo-m-phenyleneoxalamide copper(II) double mesocates as electroswitchable ferromagnetic ‘metal–organic wires’ (MOWs) on the basis of their unique ferromagnetic and multicenter redox behaviors.
Identifiersdoi: 10.1002/chem.201001737
issn: 0947-6539
e-issn: 1521-3765
Appears in Collections:(ICMA) Artículos
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