The reaction of Ln(hfac)3·2H2O and pyridine-N-oxide leads to isostructural dimers of formula [Ln(hfac)3(PyNO)]2 (with Ln =Eu, Gd, Tb, Dy).The Dy derivative shows a remarkable single-molecule magnet behaviour with complex hysteresis at 1.4 K.The dynamics of the magnetization features two relaxation regimes: a thermally activated one at high temperature (τ0=5.62 ± 0.4×10-11 s and △=167 ± 1 K) and a quantum tunneling regime at low temperature with a tunneling frequency of 0.42 Hz.The analysis of the Gd derivative evidences intradimer antiferromagnetic interactions(J=-0.034 ± 0.001 cm-1).Moreover the Eu, Tb and Dy derivatives are luminescent with quantum yield of 51, 53 and 0.1% respectively.The thermal investigation of[Dy(hfac)3(PyNO)]2 shows that the dimers can be sublimated intact, suggesting their possible exploit as active materials for surface confined nanostructures to be investigated by fluorimetry methods.