The combination of Ln^III ion (Gd^III or Dy^III) with two different indazole nitronyl nitroxide radicals results in four novel 2p–4f compounds, namely, [Ln(hfac)₃(5-IndazoleNIT)]₂ (Ln = Gd (1), Dy (2); hfac = hexafluoroacetylacetone; 5-IndazoleNIT = 5-(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl)-1H-Indazole) and [Ln(hfac)₃(6-IndazoleNIT)]₂ (Ln = Gd (3), Dy (4); 6-IndazoleNIT = 6-(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl)-1H-Indazole). Single crystal X-ray diffraction studies revealed that compounds 1–2 are binuclear isostructural complexes with local D_2d symmetry, in which each 5-IndazoleNIT molecule acts as a bridging ligand linking two Ln^III ions through the oxygen atom of its NO group and nitrogen atom of its indazole ring to form a cyclic four-spin system. Complexes 3–4 exhibit analogous binuclear cyclic four-spin systems, where the symmetry of central Ln^III ions is D_4d due to the change of location of the NO group in the indazole ring. In addition, compound 2 displays no out-of-phase alternating-current (ac) signal, whereas compound 4 exhibits obvious slow relaxation of magnetization, suggesting single-molecule magnet (SMM) behavior. The different magnetic relaxation behaviour between 2 and 4 is largely dependent on the ligand field of the central dysprosium ions.