Structurally different nickel(II) hexaaza macrocyclic complexes with the same btc2− anions (btc2−=1,2,4,5-benzenetetracarboxylic acid dianion)

Two novel complexes with the composition {[Ni(L)]·(btc2−)}n (1) {L=3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane; btc2−=1,2,4,5-benzenetetracarboxylic acid dianion} and [Ni(L)]·(btc2−)·(btc) (2) were obtained from the reaction between [Ni(L)Cl2] and btc (btc=1,2,4,5-benzenetetracarboxylic acid), and their structures were determined by analytical, spectroscopic, and X-ray diffraction methods. The orange complex 1 contains a 1D hydrogen bonded polymeric chain with nickel(II) macrocycles and bridging btc2− ligands. The nickel(II) coordination geometry in 1 is best described as a square-plane with four Ni–N bonds. The weak interactions between the nickel(II) ions and the oxygen atoms of the btc2− ligand are also found. The yellow complex 2 has a monomeric structure which is composed of a nickel(II) macrocycle, a counter anion btc2−, and a free acid btc (btc=1,2,4,5-benzenetetracarboxylic acid). The nickel(II) coordination geometry in 2 is square-planar, where the tetra-valent nickel(II) ion is completed with four nitrogen atoms from the macrocycle. In addition to the presence of counter anion btc2−, the free acid btc is also found in 2, which participates in abundant hydrogen-bonding interactions.