TY  - JOUR
AU  - Ferrando-Soria, J.
AU  - Cangussu, D.
AU  - Eslava, M.
AU  - Journaux, Y.
AU  - Lescouëzec, R.
AU  - Julve, M.
AU  - Lloret, F.
AU  - Pasán, J.
AU  - Ruiz-Pérez, C.
AU  - Lhotel, E.
AU  - Paulsen, C.
AU  - Pardo, E.
T1  - Rational enantioselective design of chiral heterobimetallic single-chain magnets: Synthesis, crystal structures and magnetic properties of oxamato-bridged MIICuII chains (M=Mn, Co)
LA  - eng
PY  - 2011
SP  - 12482
EP  - 12494
T2  - Chemistry - A European Journal
SN  - 1521-3765
VL  - 17
IS  - 44
PB  - Wiley-VCH Verlag
AB  - A new series of neutral oxamato-bridged MIICuII chiral chains of general formula [MCuLx(S)m(H 2O)n]·aS·bH2O [L 1=(M)-1,1′-binaphthalene-2,2′-bis(oxamate) with M=Mn (1 a) and Co (1 b); L2=(P)-1,1′-binaphthalene-2,2′- bis(oxamate) with M=Mn (2 a) and Co (2 b)] and the analogous racemic chains of formula [MCuL3(S)m(H2O)n] ·aS·bH2O [L3=1,1′-binaphthalene-2, 2′-bis(oxamate) with M=Mn (3 a) and Co (3 b)] have been prepared by reaction of the corresponding dianionic oxamatocopper(II) complex [Cu(L x)]2- with Mn2+ or Co2+ cations in either dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). Solid circular dichroism (CD) spectra of the bimetallic chain compounds were recorded to establish their chiral and enantiomeric nature. They exhibit maximum positive and negative Cotton effects, each pair of enantiomeric chains being non-superimposable mirror images. The crystal structures of the Mn IICuII (1 a-3 a) and the CoIICuII (1 b and 2 b) chain compounds were solved by single-crystal X-ray diffraction methods. Our attempts to obtain X-ray quality crystals of 3 b were unsuccessful. The values of the shortest interchain Mn⋯Mn and Co⋯Co distances are indicative of a good isolation of neighbouring chains in the crystal lattice, which is caused by the bulky aromatic ligand. Although all the Mn IICuII and CoIICuII chains exhibit ferrimagnetic behaviour (-JMnCu=18.9-26.6 cm-1 and -J CoCu=19.5-32.5 cm-1), only the enantiopure Co IICuII chains (1 b and 2 b) show slow magnetic relaxation at low temperatures (TB=0.6-1.8 K), which is a characteristic of single-chain magnets (SCMs) and is related to the magnetic anisotropy of the high-spin CoII ion. Analysis of the SCM behaviour of 1 b and 2 b, based on Glauber's theory for an Ising one-dimensional system, shows a thermally activated mechanism for the magnetic relaxation (Arrhenius law dependence). The energy barriers (Ea) to reverse the magnetisation direction are 8.2 (1 b) and 8.1 cm-1 (2 b), whereas the pre-exponential factor (τ0) is 1.9× 10-8 (1 b) and 6.0× 10 -9 s (2 b). Interestingly, the racemic CoIICuII chain analogue, 3 b, showed no evidence of SCM behaviour. Magnetic molecular materials: The reactions of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with manganese(II) and cobalt(II) ions lead to neutral oxamato-bridged heterobimetallic chiral chains (see figure), which, in the case of cobalt(II) ions, show slow relaxation of magnetisation, thus providing the first examples of "chiral single-chain magnets" (CSCMs). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DO  - 10.1002/chem.201101459
UR  - https://portalciencia.ull.es/documentos/5e3c364b29995246bbf5dda2
DP  - Dialnet - Portal de la Investigación
ER  -