Syntheses and characterizations of four mixed-ligand hydrogen bonding supramolecular architectures with different structural motifs

The reactions of 4-aminobenzoic acid (4-abaH), 4,4′-bipyridine (4,4′-bipy) and transitional metal ions (ZnII, MnII and CuII) gave rise to four supramolecular architectures, namely, [(4-abaH)2(4,4′-bipy)] (1), {[Zn2(4,4′-bipy)2(4-aba)4] (H2O)5}n (2), {[Mn(4,4′-bipy)2(H2O)4] (4-aba)Br(H2O)3} (3) and {[Cu2(4,4′-bipy)3(H2O)2(4-aba)2](NO3)2(H2O)4}n (4). Their crystal structures were determined by X-ray diffraction and show different structural motifs. 1 is a one-dimensional hydrogen bonding ladder constructed by 4-abaH and 4,4′-bipy. In 2, 4,4′-bipy bridges Zn(4-aba)2 units forming a one-dimensional zigzag chain, which is extended into a three-dimensional framework by crystalline water molecules through hydrogen bonding interactions. Three-dimensional network of 3 is constructed by mononuclear [Mn(4,4′-bipy)2(H2O)4]2+ cations, neutral crystalline water molecules, and 4-aba and Br− anions through extensive hydrogen bonding and π–π interactions. However, one-dimensional ladder formed by 4,4′-bipy and Cu(4-aba) units in 4 is extended into a three-dimensional architecture through interpenetration of the lateral 4-aba arms into squares of the adjacent Cu–(4,4′-bipy) ladders and extensive hydrogen bonding interactions.