A new series of neutral oxamato-bridged MIICuII chiral chains of general formula [MCuLx(S)m(H2O)n]⋅aS⋅bH2O [L1=(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(Lx)]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 MnIICuII (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 MnIICuII and CoIICuII chains exhibit ferrimagnetic behaviour (−JMnCu=18.9–26.6 cm−1 and −JCoCu=19.5–32.5 cm−1), only the enantiopure CoIICuII 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.
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