Syntheses, structures, and magnetic properties of two hexanuclear [5×1 + 1×1] lanthanide cocrystal complexes [Ln 5 (L) 4 (LH 2 ) 2 (tfa) 4 ]·[Ln(tfa) 4 ]·2CH 3 OH [Ln = Dy(1) and Tb(2)] derived from the polyhydroxy ligand 2-(hydroxymethyl)-6-carbaldehyde-4-methylphenol (LH 2 ) are reported. Compounds 1 and 2 crystallize in the triclinic system with space group P1. X-ray crystallography reveals that 1 and 2 are cocrystals comprising one cationic pentanuclear [Ln 5 (L) 4 (LH 2 ) 2 (tfa) 4 ] + unit and one anionic mononuclear [Ln(tfa) 4 ] – unit as well as two molecules of methanol as solvent of crystallization. Both complexes form a [2.2] spirocyclic topology fashioned core due to merging of two triangular geometries composed of Ln(III) ions through a common vertex. The central Ln(III) ion in the spirocyclic pentanuclear assembly is eight-coordinate with distorted square antiprism geometry. On the other hand, the peripheral eight-coordinate Ln(III) ions are in a distorted trigonal dodecahedron geometry. The comprehensive magnetic study reveals that compound 1 displays slow relaxation of magnetism. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim