The organic chelating and bridging ligands 9,10-phenanthrenedione-9-oxime (phenoxH) and 9,10-phenanthrenedione-9,10-dioxime (phendoxH(2)) were synthesized and subsequently employed for the first time in heterometallic 3d/4f-metal cluster chemistry. The general reaction between CuCl2 center dot 2H(2)O, LnCl(3)center dot 6H(2)O, phenoxH, and NEt3 in a 1:2:2:4 molar ratio, in a solvent mixture comprising MeCN and MeOH, afforded brown crystals of a new family of [Cu(3)LnCl(3)(phenox)(6)(MeOH)(3)] clusters (Ln = Gd (1), Tb (2), Dy (3)) that possess an unprecedented [Cu(3)Ln(mu-NO)(6)](3+) "propeller"-like core. Complexes 1-3 are the first {Cu(3)Ln} clusters in which the outer Cu-II and the central Ln(III) atoms are solely bridged by diatomic oximato bridges. The {Cu-N-O-Ln} bridging units are very distorted with torsion angles spanning the range 35.5 - 48.9 degrees and 25.2 - 55.6 degrees in 1 and 2, respectively. As a result, complexes 1-3 are antiferromagnetically coupled, in agreement with previously reported magneto structural criteria for oximato-bridged Cu/Ln complexes. The magnetic susceptibility data for all complexes were nicely fit to an isotropic spin Hamiltonian (for 1) or a Hamiltonian that accounts for the spin of the Cu-II atoms, the spin component of the Ln(III), the spin-orbit coupling (lambda), an axial ligand-field component around the Ln(III) atoms (Delta), and the Zeeman effect (for the anisotropic 2 and 3). The resulting fit parameters were J = -1.34 cm(-1) and g = 2.10 (1), J = -1.42 cm(-1), g(Cu), = 2.10, and Delta = -26.3 cm(-1) (2), and J = -1.70 cm(-1), g(Cu) = 2.05, and Delta = -38.1 cm(-1) (3). The reported fitting procedure, implemented in the PHI program, is here used for the first time. Even if this method is only valid in high-symmetry Ln environments, when it is properly used allows a very simple and efficient method to obtain the exchange parameters. In light of the negative anisotropy, compounds 2 and 3 were found to exhibit frequency-dependent tails of out-of-phase signals in the presence of a small external dc field, characteristic of the slow magnetization relaxation of a single-molecule magnet. By using the Kramers-ronig equations, the effective energy barriers (U-eff) were derived and reported as U-eff = 10.1 and 5.4 cm(-1) for 2 and 3, respectively.