Two vanillin derivatives, 4-hydroxy-3-methoxybenzaldehyde nicotinoylhydrazone (L 1 ) and 4-hydroxy-3-methoxybenzaldehyde salicyloylhydrazone (L 2 ), were synthesized. The two flexible ligands have been employed to assemble with Pb(II), Cu(II), or Co(II) ion, leading to the formation of five coordination polymers varying from zero-to three-dimensional structures. Complex [Pb 2 (L 1 ) 2 (NO 3 ) 2 ] 3 3H 2 O (1) features a novel 3D diamond-like coordination network based on binuclear units as binodes and hydrazone ligands, L 1 , as linkers. However, complex Pb 2 (L 1 ) 2 (OAc) 2 (H 2 O) 2 (2) presents a 1D doublestrand chain structure. Two factors, the second ligand (acid ligand) and different coordination ability of water molecules, are investigated to further explore its relationship with the resultant crystalline architectures in complexes 1 and 2. The donor atoms in the two lead(II) complexes 1 and 2 can cluster to one side leaving an "open" coordination site to accommodate the stereochemically active 6s 2 lone pair. Complex Cu(L 2 ) 2 (3) shows a 1D double-strand chain structure. There is an extended onedimensional structure in complex [Co 3þ (L 2 ) 2 (C 5 H 5 N) 2 ] 3 ClO 4 (4), while [Co 2þ (L 2 ) 2 (C 5 H 5 N) 2 ] 3 2CH 3 OH 3 H 2 O (5) displays a discrete structure.