Synthesis and characterization of coordination polymers of a carboxylato cyclophane with metal [Zn(II) and Cd(II)]-2,2′-bipyridines

Abstract

N,N′,N′′,N′′′-Tetrakis(3-carboxy-propionyl)-1,6,20,25-tetraaza-[6.1.6.1] paracyclophane, H 4cp has been complexed with metal (Zn(II) and Cd(II)) 2,2 ′ -bipyridyls. The resulting complexes of the composition [{Zn(2,2 ′-bpy)} 2(cp)] n ·4H 2O 1 and [{Cd(2,2 ′-bpy)} 2(cp)] n ·5H 2O 2 (2,2 ′-bpy = 2,2 ′-bipyridine) have been characterized using spectroscopic (IR, solid state UV–Vis), elemental analysis and single-crystal X-ray diffraction measurements. In these complexes the cyclophane coordinates in different modes, and in complex 2, Cd(II) is hepta-coordinated. However, under harsh reaction conditions (using excess nitric acid and a longer reaction time) debranching of the cyclophane is observed in the reaction of Zn(2,2 ′-bpy)(NO 3) 2 with H 4cp, and a complex of the composition [Zn(2,2 ′-bpy)(Suc)] n 3 (suc = succinate) is isolated. Using non-covalent interactions, complexes 1 and 2 provide 3D supramolecular structures, whereas an infinite 1D chain structure is observed for complex 3. The thermal and photoluminescence properties of the complexes have also been studied.