Self-Assembly of Molecular Brick Wall and Molecular Honeycomb from Nickel(II) Macrocycle and 1,3,5-Benzenetricarboxylate: Guest-Dependent Host Structures

Abstract

Novel multidimensional supramolecular networks with brick wall and honeycomb structures, [Ni(C12H30N6O2)]3[C6H3(COO)3]2·18H2O (1) and [Ni(C12H30N6O2)]3[C6H3(COO)3]2·14H2O·2C5H5N (2), respectively, have been constructed by the self-assembly of S = 0 Ni(II) macrocyclic complex containing hydroxyl pendent chains and 1,3,5-benzenetricarboxylate (BTC3-). The host structures assembled are greatly affected even by the partial change of the guests. X-ray crystal structures indicate that each Ni(II) macrocycle binds two BTC3- in the trans position and each BTC3- coordinates three Ni(II) macrocyclic units via C1 symmetry in 1 and C3 symmetry in 2. The simplest cyclic motif of the two-dimensional (2-D) networks in 1 and 2 is a large ring consisting of six Ni(II) macrocyclic complexes and six BTC3- anions. The rings are extended to form a 2-D layer. The layers are stacked in parallel, separated by 8.850 Å in 1 and 8.973 Å in 2. They are interconnected by the hydrogen-bonding interactions between the hydroxyl pendants of the macrocycle in a layer and the secondary amines of the macrocycle located in the neighboring layers, which gives rise to the three-dimensional structures. The effective cavity size of 1 is ca. 6.7 × 13 Å and that of 2 ca. 11.4 × 11.4 Å. The cavities are filled with guest molecules. In 2, the pyridine guest experiences π−π interaction with the benzene ring of BTC3-. Variable-temperature (2−300 K) magnetic susceptibility measurements indicate that both 1 and 2 exhibit weak anti-ferromagnetic interactions between the S = 1 Ni(II) paramagnetic centers.