Dimethyl-substituted bis(benzimidazole) (Me(2)BBZ) is a novel macrocyclic ligand that possesses an intrinsic nonplanarity. To examine how metal-ion binding affects the magnitude of this nonplanarity, we have determined the structures of a periodic series of Me(2)BBZ complexes bound to Mn(II), Fe(II), Co(II), Ni(II), and Cu(II). These studies demonstrate that the extent of ligand ruffling and metal doming is indeed influenced by the nature of the metal. Concomitant with the periodic decrease of the ionic radii of the encapsulated divalent metal ion, a decrease in the magnitude of both the ligand nonplanarity and the metal out-of-the-plane distance is observed. For the metal out-of-the-plane distance, this correlation persists until the metal finally moves into the mean ligand plane. For the nonplanar distortion, the extent of the nonplanarity decreases to a limiting value that is intrinsic to the Me(2)BBZ ligand due to steric factors. These observations indicate that the relative sizes of the metal ion and the Me(2)BBZ ligand cavity have profound effects on the structural features of the metal-ligand complex.