Structural, electronic and magnetic properties of Cu(ii) complexes of 2-substituted tropones bearing a ferrocenyl group at 5-position

Abstract

Heterotrinuclear Fe(II)-Cu(II)-Fe(II) complexes [Cu(FcTropOMe)(2)(H(2)O)(2)](OTf)(2) (FcTropOMe = 5-ferrocenyl-2-methoxytropone) (1), [Cu(FcTropNEt(2))(2)](OTf)(2) (FcTropNEt(2) = 2-(N,N-diethylamino)-5-ferrocenyltropone) (2) and [Cu(FcTropNEt)(2)] (FcTropNEt = 2-(N-ethylamino)-5-ferrocenyltroponate) (3) were synthesized. In addition, a hexafluorophosphate salt of heterotrinuclear Fe(III)-Cu(II)-Fe(III) complex [Cu(FcTropNEt)(2)](2+) (3(2+)) was successfully obtained as single crystals by electrochemical oxidation of 3. By comparing the X-ray structures and absorption spectra of dicationic complexes 1 and 2, the 2-(diethylamino)tropone ligand was found to induce a greater intramolecular charge transfer (CT) from ferrocenyl to tropone-Cu(II) moieties than the 2-methoxytropone ligand. On the other hand, 3(2+) showed a broad CT band in the near-infrared (NIR) region similar to 2, which can be assigned to a transition from troponato-Cu(II) to ferrocenium moieties. As for the magnetic properties of 3(2+)(PF(6)(-))(2), measurements of temperature dependence of magnetic susceptibility and ESR on the solid state and in solution revealed the presence of a strong ferromagnetic interaction (J(Fe-Cu) = +12.0 cm(-1)) between the low spin Fe(III) ion with S = 1/2 and Cu(II) ion with S = 1/2 despite a long distance pathway via the aminotroponato and cyclopentadienyl moieties. DFT calculations supported this intramolecular ferromagnetism, which is induced by a spin polarization mechanism through the pi-spacers.

A clothes-peg-shaped binucleartrans-bis(2-aminotroponato)palladium(II) complex bearing pentamethylene spacers

“…A variety of 2-aminotroponate complexes, ML 2 and MLX (L is 2-aminotroponate), with metal centres such as Ni II (Jenkins & Brookhart, 2004), Ca II (Datta et al, 2007), Ti IV (Mazzeo et al, 2005), Al III (Pappalardo et al, 2004), Zn II (Meyer et al, 2006;Jin et al, 2010), Au I (Meiners et al, 2007), Rh I (Steyl, 2007) and Cu II (Mori et al, 2005;Nishinaga et al, 2010;Steyl et al, 2010), have been extensively studied for the development of functional materials that exhibit catalytic activity for molecular transformation, luminescence, magnetic properties and liquid-crystalline behaviour.…”

Crystal structure of 2-(methylamino)tropone

“…The ligands of importance in this study and future work, namely 2-(alkylamino)tropones and aminotroponimines, are N,O and N,N 0 bidentate, monoanionic ligands containing a ten -electron backbone (Roesky, 2000). The -conjugated backbone is characteristic of these ligands (Nishinaga et al, 2010). Considering the above-mentioned characteristics, tropolone could be considered analogous to the O-donor 2 -O,O 0 acetylacetonate ligand (acac-O,O 0 ).…”

Long-Range Intramolecular Electronic Communication in a Trinuclear Ruthenium Tropolonate Complex

“…In the former view, Htrop and its derivatives have been mainly investigated in terms of the antioxidant properties such as the inhibition of various oxidases. − In the latter sense, Htrop derivatives have attracted attention as a framework for organic redox systems, − ever since Nozoe proposed tropoquinone (cyclohepta-3,6-diene-1,2,5-trione) as an oxidized form of 5-hydroxytropolone . The redox chemistry of metal tropolonate complexes has been also investigated, − including the study of Htrop derivatives as redox-active ligands, − while ruthenium tropolonate complexes have not been fully investigated. Even a basic cyclic voltammetry (CV) study of [Ru­(trop) 3 ] ( 1 ) had not been reported until our recent report .…”