Assembly of Binuclear, Tetranuclear, and Multinuclear Complexes from Pincer-Like Mononuclear Metallotectons: Structural Diversity Dependent on Precursors

Reactions of Cu­(II), Cd­(II), and Ni­(II) with a new tetradentate ligand N1,N3-bis­(1-(1H-benzimidazol-2-yl)­ethylidene)­propane-1,3-diamine (H2bbepd) afforded four mononuclear pincer-like complexes of [Cu­(H2bbepd)­(ClO4)]­·CH3OH·ClO4 (1), [Cd­(H2bbepd)­(CH3OH)­(ClO4)]­·CH3OH·ClO4 (2), [Ni­(H2bbepd)­(H2O)2]­·2ClO4 (3), and [Ni­(H2bbepd)­(NO3)2] (4), respectively. The labile small coordinated components (anions or solvent molecules) on the apical coordination site of metal ions in complexes 1–4 display three different modes, which can be substituted by 4,4′-bipyridine (bpy) to obtain four new multinuclear complexes of [Cu2(H2bbepd)2­(bpy)]2­·4ClO4 (5), [Cd4(H2bbepd)4­(bpy)3­(ClO4)2]­·6ClO4·(bpy)­·2CH3OH­·6H2O (6), {[Ni­(H2bbepd)­(bpy)]­·2ClO4­·CH3OH}n (7), and {[Ni (H2bbepd)­(bpy)]­·2NO3­·CH3OH­·H2O}n (8), respectively. Complex 5 is a binuclear dumbbell-like molecule, complex 6 is a rare example of discrete linear tetranuclear molecule, while complexes 7 and 8 are one-dimensional chains formed by an alternate arrangement of bpy molecules and mononuclear subunits. The differences in complexes 5–8 are largely dependent on the structure of the mononuclear precusors of complexes 1–4. All eight complexes are assembled into higher dimensional supramolecular frameworks by diverse nonconvalent interactions including unusual anion···π interactions between perchlorate and five-membered benzimidazole rings.