Two types of assembly with the same carboxylate ligands, [Cu I I {OCO-2,6-(CH 3 CONH) 2 C 6 H 3 ) 2 (H 2 O) 2 ] nH 2 O (n = 1 (1), 4 (2)), and a common monomer unit, [Cu I I {OCO-2,6-(CH 3 CONH) 2 C 6 H 3 } 2 (H 2 O) 2 ], were synthesized; different hydrogen bond networks determined by X-ray analysis occur. While 2 has an infinite chain extended by intermolecular OH O hydrogen bonds, 1 has them between two molecules only. Their temperature-dependent magnetic susceptibilities (-2J = 6.04(2) cm - 1 (1) and 3.38(1) cm - 1 (2)) are related to the extent of the intermolecular hydrogen bond network. These results indicate that the formation of intermolecular hydrogen bonds changes the magnetic properties of materials.