A new family of [CuIILnIIIMV] heterotrimetallic complexes (Ln = La, Gd, Tb; M = Mo, W): model systems to probe exchange interactions and single-molecule magnet properties?

Dalton Transactions Pub Date: 2016-03-15 DOI: 10.1039/C6DT00614K

Abstract

Four isostructural trinuclear 3d–4f–4(5)d heterotrimetallic complexes, with the general formula [L2CuLn(H2O)5(μ-NC)M(CN)7], were obtained from the association of binuclear 3d–4f complexes and {MV(CN)8}3? metalloligands (M = Mo, Ln = La 1; M = W, Ln = La 2; M = Mo, Ln = Gd 3; M = Mo; Ln = Tb 4, where H2L2 = 1,2-ethanediylbis(2-iminomethylene-6-methoxy-phenol)). The metalloligand coordinates through a single-cyanido group at the apical position of the copper(II) ion belonging to the {CuIILnIII} binuclear complex. The analysis of the magnetic data for the La(III) derivatives (compounds 1 and 2), in the 1.85–300 K temperature range, shows a weak ferromagnetic exchange interaction between CuII and MoV/WV ions across the cyanido bridge (JCuM/kB = 3.6(6) K; g = 2.23(5) for 1 and JCuM/kB = 3.8(6) K, g = 2.21(5) for 2, with H = ?2JCuMSCu·SM). These results were used to simulate the magnetic properties of compound 3, using the isotropic spin Hamiltonian H = ?2JCuMoSCu·SMo ? 2JCuGdSCu·SGd. The resulting magnetic interaction between CuII and GdIII ions via the phenoxo-bridge was found to be weakly ferromagnetic (JCuGd/kB = +4.5(2) K with JCuMo/kB = +3.6(2) K, gGd = gCu = 2.00 and gMo = 1.98). The dc magnetic properties for compound 4 also show a predominant ferromagnetic interaction, while the ac magnetic measurements indicate the presence of the slow relaxation of the magnetization below 3.5 K.

Graphical abstract: A new family of [CuIILnIIIMV] heterotrimetallic complexes (Ln = La, Gd, Tb; M = Mo, W): model systems to probe exchange interactions and single-molecule magnet properties
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