A novel dodecanuclear manganese metalladiazamacrocycle was synthesized employing a new pentadentate ligand N-2-pentenoylsalicylhydrazide (H 3tpeshz) by supramolecular self-assembly. The backbone of this metal-organic assembly is a repeating unit of an M-N-N-M linkage that extends to complete a 36-membered cyclic structure involving 12 manganese(III) centers. Successive manganese centers are in a chemically different ⋯ ABABAB⋯-type environment while the chirality varies as ⋯ΛΛΔΔΛΛ⋯. The unique arrangement of manganese centers results in a highly puckered metalladiazamacrocycle with an S6-point group symmetry.