In situ generation of functionality in a reactive binicotinic-acid-based ligand for the design of multi-functional copper(II) complexes: syntheses, structures and properties

Under hydrothermal conditions, including tuning the reaction ratio and reaction temperature, three-dimensional (3D) porous {[Cu-3(hbpdc)(OH)(2)center dot H2O)]center dot 2H(2)O} (1), two-dimensional (2D) sheet {Cu-2(hbpdc)-(H2O)(2)}(n) (2), dinuclear [Cu(hbpdc)(0.5)center dot H2O)(2)] (3), dimer (Cu-2(mbpdc)(2)(py)(2)]center dot 9H(2)O (4), and mononuclear [Cu(hbpdcH(2))(H2O)(2)] (5) have been synthesized via in situ ligand transformation reaction, in which 3,3'-dimethoxy-2,2-bipyridine-6,6'-dicarboxylic acid (mbpdcH(2)) undergoes demethylation to 3,3'-dihydroxy-2,2' bipyridine-6,6'-dicarboxylic acid (hbpdcH(4)). The detailed coordination patterns of the hbpdcH(4) ligand have been revealed by single-crystal X-ray diffraction. The catalytic results demonstrate that polymers 1 and 2 can function as heterogeneous and reusable catalysts for the Strecker reaction of various imines. In addition, magnetic susceptibility measurements of complexes 1, 2 and 4 reveal antiferromagnetic coupling between the copper.II) ions. Complex 1 follows the Curie-Weiss law, while 2 and 4 obey the BleaneyBowers dinuclear model.