pH-controlled assembly of two supramolecular architectures based on Cu(II)-metallacycle building blocks

Two novel copper(II) complexes Cu(Hip)2(H2O)2 (1) (H2ip = isophthalic acid) and Cu3(ipO)2(H2O)3 (2) (H3ipO = 2-hydroxy isophthalic acid) have been synthesized through hydrothermal reaction of copper(II) chloride, isophthalic acid, melamine and sodium hydroxide under different pH conditions. The diverse poduct structures show that the pH value of the reaction plays a key role in the hydroxylation of isophthalic acid. The single-crystal X-ray diffraction studies reveal that complex 1 features a 3D supramolecular framework constructed by hydrogen bonds connecting neutral subunits Cu2(Hip)4(H2O)4; whereas complex 2 is based on hexametallic macrocylic building blocks, which are further extended into 2D network through hydrogen-bonding interactions.