Syntheses and characterization of various supramolecular compounds from the self-assembly of nickel(II) hexaaza macrocyclic complex with carboxylic acid derivatives

Abstract

The supramolecular compounds [Ni(C16H38N6)(2,7-NDC)] (1), [Ni(C16H38N6)(H2O)2] [Ni(C16H38N6)(1,3,5-BTC)2] (2), and [Ni(C16H38N6)(nicotinate)2] (3) were prepared via self-assembly of a nickel(II) azamacrocyclic complex containing butyl pendant groups, [Ni(C16H38N6)(ClO4)2], with 2,7-naphthalenedicarboxylic acid (2,7-NDC), 1,3,5-benzenetricarboxylic acid (1,3,5-BTC), and nicotinic acid, respectively. These compounds were characterized by elemental analysis, infrared spectroscopy, magnetic measurement and single crystal X-ray diffraction. In 1, the nickel(II) azamacrocyclic complex links two 2,7-NDC2− ligand at the axial position and each 2,7-NDC2− ligand binds two adjacent nickel(II) azamacrocylic units with syn–syn and syn–anti orientations to form a zigzag 1-D chain structure. The zigzag 1-D chain tends to interact via offset face-to-face π–π interactions with adjacent 1-D chains, which leads to a 2-D supramolecular network. Compound 1 exhibits very weak antiferromagnetic interactions through the bridged 2,7-NDC2− ligand within the 1-D zigzag chains (g=2.11 and J/κB=−0.29cm−1). Compound 2 consists of two nickel(II) azamacrocyclic cation units and one nickel(II) azamacrocylic anion unit. Each nickel(II) ion in the cation and anion units is coordinated with four nitrogen atoms of the azamacrocyclic ligand in the equatorial plane, and two oxygen atoms from the water molecules or BTC3− ligands at the axial positions, to display a distorted octahedral geometry. The cation and anion units form intermolecular hydrogen bonds, giving rise to a 3-D supramolecular structure. In 3, the coordination environment around the nickel(II) ion has a distorted octahedral geometry via coordination with four nitrogen atoms of the azamacrocyclic ligand in the equatorial plane, and two nicotinate anions at the axial positions and intramolecular hydrogen bonding interactions between the amine groups and nicotinate anions stabilize the molecular structure.