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A study of the exchange interaction through phenolato, oximato and oxamidato bridges in MnIICuII dimers. Crystal structure of [Cu(salen)Mn(hfa)2]

1993; Elsevier BV; Volume: 213; Issue: 1-2 Linguagem: Inglês

10.1016/s0020-1693(00)83836-0

1873-3255

Rafael Ruiz‐García, Francesc Lloret, Miguel Julve, Juan Faus, M. Carmen Muñoz, Xavier Soláns,

Lanthanide and Transition Metal Complexes

Three new heterodinuclear CuIIMnII complexes of formula [Cu(salen)Mn(hfa)2] (1), [Cu(pdmg)Mn(phen)2](ClO4)2·2.5H2O (2) and [Cu(apox)Mn(bpy)2](ClO4]2·0.5H2O (3) (salen=N,N′-ethylenebis(salicylideneiminate), hfa=hexafluoroacetylacetonate, pdmg=3,9-dimethyl-4,8-diazaundeca-3,8-diene-2,10-dione dioximate, phen=1,10- phenanthroline, apox=N,N′-bis(3-aminopropyl)oxamidate and bipy=2,2′-bipyridyl) have been synthesized. The crystal and molecular structure of 1 has been determined by X-ray diffraction methods. It crystallizes in the triclinic system, space group P1 with cell constants a=15.584(4), b=12.039(3), c=9.470(2) Å, α=113.83(2), β=107.17(3), γ=84.28(3)°; V=1552(1) Å3, D (calc., Z=2)=1.708 g cm−3, Mr=798.89, F(000)=792, λ (Mo Kα)=0.71069 Å, μ=12.63 cm−1 and T=298 K. A total of 3129 reflections was collected over the range 2≤θ≤25; of these, 2584 (independent and with I≥2.5σ(I)) were used in the structural analysis. The final value of R and Rw residuals was 0.069. The structure of 1 is made up of neutral [Cu(salen)Mn(hfa)2] units. Imine-nitrogen and phenolate-oxygen atoms from salen are bound to the copper atom forming a four-folding surrounding slightly deviating from planarity whereas six oxygen atoms (two from salen and four from the two hfa ligands) define a distorted octahedral environment around the manganese atom. The CuO2Mn bridging network is bent, the dihedral angle being 14.6°. The magnetic properties of 1–3 have been investigated in the 4.2–300 K temperature range. They correspond to what is expected for an antiferromagnetically coupled CuIIMnII pair with SCu=1/2 and SMn=5/2 local spins. Based on the spin Hamiltonian Ĥ−JŜCu·ŜMn, the coupling constant J was evaluated as −22.4, −50.3 and −24.5 cm−1 for 1–3, respectively. The larger value of |J| for 2 confirms the great efficiency of the oximate bridge to transmit the electronic effects between metal centers separated by more than 3.5 Å.