Color-tunable entangled coordination polymers based on long flexible bis(imidazole) ligands and phenylenediacetate

Six coordination polymers, namely, [Co-2(mpda)(2)(Hmpda)(bibp)]center dot H2O (1), [Pb(Hmpda)(bibp)Cl]center dot H2O (2), [Cd(mpda)(bibp)] (3), [Cd(ppda)(bibp)] (4), [Cd(opda)(bib)(0.5)(bipy)]center dot 2H(2)O (5), and [Zn(opda)(bib)] (6), where H(2)pda = phenylenediacetic acid, bibp = 4,4'-bis(imidazol-1-ylmethyl) biphenyl, bib = 1,4-bis(imidazol-1-ylmethyl)benzene, and bipy = 2,2'-bipyridine, have been synthesized using different metal salts with phenylenediacetic acid and bis(imidazole) ligands under hydrothermal conditions. Their structures have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD) analysis. Owing to the coordination geometry around the metal ions and the diverse coordination modes of the flexible ligands, the obtained complexes 1-6 display different types of entanglement. Complex 1 possesses an extended 2D polyrotaxane and polycatenane network based on 1D ringed ribbon-like chains. The 2D coordination layers of 2 and 4 are entangled to produce 2D -> 3D polythreaded architecture. Both 3 and 6 are composed of three-fold interpenetrating 3D diamond frameworks containing single chiral helical chains, whereas three 2D helical layers of 5 interpenetrate each other in an alternating arrangement of three-stranded right-and left-handed helices. Furthermore, the fluorescence emission color of complexes 2-6 could be tuned from dark blue to light blue and green.