Three new heterodinuclear Cu IIMn II complexes of formula [Cu(salen)Mn(hfa) 2] ( 1), [Cu(pdmg)Mn(phen) 2](ClO 4) 2·2.5H 2O ( 2) and [Cu(apox)Mn(bpy) 2](ClO 4] 2·0.5H 2O ( 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 P 1 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) Å 3, D (calc., Z=2)=1.708 g cm −3, M r=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 R w 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 CuO 2Mn 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 Cu IIMn II pair with S Cu=1/2 and S Mn=5/2 local spins. Based on the spin Hamiltonian Ĥ− JŜ Cu·Ŝ Mn , 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.