Coordination-driven chiral self-assembly: Synthesis, structures and vapor adsorption properties of Zn(II) and Ag(I) complexes derived from two helical pyridylamide ligands

Abstract

Four complexes were synthesized and characterized from two helical pyridylamide ligands. A view of the geometry of these complexes discloses the self-discriminating and self-recognition process in the coordination-driven chiral assembly. • Four new complexes derived from two helical pyridylamide ligands have been synthesized and characterized. • The crystal structures of the four complexes reveal the chiral self-assembly process in the coordination reaction. • Cyclic voltammetric measurements and methanol vapor adsorptions for the complexes are investigated. Two helical pyridylamide ligands N 2 ,N 6 -bis(2-(nicotinamido)phenyl)pyridine-2,6-dicarboxamide ( L 1 ) and N 2 ,N 6 -bis(2-(isonicotinamido)phenyl)pyridine-2,6-dicarboxamide ( L 2 ) have been designed and synthesized. Four complexes, namely, {[Zn( L 1 )I 2 ]‧2CH 3 OH‧H 2 O} n ( 1 ), [Ag 2 ( L 1 ) 2 ]‧(NO 3 ) 2 ( 2 ), {[Ag( L 2 )NO 3 ]‧H 2 O} n ( 3 ), and {[Ag( L 2 ) 2 ]‧2H 2 O} n ( 4 ) were obtained via the solvent evaporation method from the reaction of the ligands with Zn(II) or Ag(I) ions respectively. The two ligands together with four complexes were structurally determined by single-crystal X-ray diffraction and additionally characterized by infrared spectroscopy, element analysis and powder X-ray diffraction. The crystal structures reveal different chiral self-assembly processes in the reaction of the helical liands with Zn(II) or Ag(I) ions. Complexes 1 , 2 and 4 exhibit as a heterochiral coordination polymer or binuclear metallamacrocycle, while complex 3 exists as a homochiral coordination polymer. Besides, the structural differences between complexes 3 and 4 show that the reaction ratio of the ligand with metal ions has obvious influences on the coordination configuration. Furthermore, thermogravimetric analysis and methanol vapor adsorption properties of the synthesized complexes have been investigated, and cyclic voltammetric measurements of complexes 2 – 4 were carried out as well.