Two neutral, isostructural, octanuclear, Ln^III complexes, [Ln₈(HL)₆(L)₂(μ₃-OH)₄(μ₂-OH)₂(H₂-O)₄].solv (Ln = Gd(III), (1^Gd) and Dy(III), (2^Dy) have been synthesized using Ln^III nitrate salts and a ovanillin-supported multi-dentate ligand, N’-(2-hydroxy-3-methoxy-5-nitrobenzylidene)-2-(hydroxyamino)propanehydrazide (H₃L) in the presence of tetramethyl ammonium hydroxide. The complexes were structurallycharacterized by single crystal X-ray diffraction studies. The complexes are held by the cumulativecoordination action of six [HL]^2-, two [L]^3- chelating ligands, H₂O and hydroxide ligands. Magnetostructuralanalysis of complexes 1^Gd and 2^Dy reveals the presence of intramolecular antiferromagneticinteractions between the Ln^III ions. Magneto-caloric effect was analysed for the complex 1^Gd which shows amaximum in the change of molar entropy (–ΔS_m) of magnitude 25.5 J kg^–1 K^–1 at T = 3 K and an applied fieldchange ΔB = 5 T.