Synthesis And Properties Of Metallo-supramolecular Polymers

The so-called supramolecular polymers formed based on the weak interactionbetween the monomers, have attracted much attention because of their excellentproperties such as novel structure, environmental responsiveness, catalytic, andbiological sensing etc. Terpyridine, as a building block, has a unique advantage inbuilding supramolecular polymers. In this paper,2,2’:6,’,2’’-terpyridine wasfunctionalized by coupled with different kinds of piperazine derivatives which hasdifferent electron donating ability on its4’ position to form a series of functionalizedterpyridine ligand derivatives with D-A structure. These ligands were complexed withZn²⁺and Cd²⁺to form complexes. A serious of study on ultraviolet-visible （UV-Vis）absorption spectra and fluorescence emission （FL） spectra was taken. Two A-D-Astructured ligands which have two terpyridine groups were synthesized based on thetheory of small molecular module complexes, then coordinated with transition metalions and metallo-supramolecular polymers were obtained. A systematicallycharacterization and ultraviolet-visible （UV-Vis） absorption spectra and fluorescenceemission （FL） spectra of polymers was taken.（1） Coupled with three piperazine derivatives which have different electrondonating ability, the terpyridine ligands with D-A structure were formed. Then theseligands were coordinated with Zn²⁺ and Cd²⁺ respectively and a series of complexeswas obtained. A series of study on ultraviolet-visible （UV-Vis） absorption spectra andfluorescence emission （FL） spectra was taken. The results show that the ligands with aD-A structures exhibit strong UV-vis peaks at about300nm and340nm, which assignto Ï€-Ï€*and intra-molecular charge transfer （ICT）, and fluorescent at about400nm,while the complexes absorb at about300nm and400nm and emit at above450nm. The solvent polarity influences the fluorescence heavily, as the solvent changes fromtoluene to methanol, the FL peak of L2, Zn（L2）₂and Cd（L2）₂red-shifted for about79nm,171nm and177nm respectively.（2） On the basic theory of D-A structure small complexes, two different A-D-Astructured ligands with terminal terpyridines were synthesized and coordinated withZn²⁺and Cd²⁺in NMP respectively. A series of study on ultraviolet-visible （UV-Vis）absorption spectra and fluorescence emission （FL） spectra was also taken. The resultshows that those coordination polymers with D-A structure absorbs at about300nmand400nm, which refers to Ï€-Ï€*and inter molecular current transfer （ICT）, andfluorescent at about400nm to500nm. The solvent polarity also has a great effect onthe coordination fluorescence of polymers, as the solvent changes from toluene tochloroform then to THF, the FL peaks shows up at413nm,446nm and500nmrespectively.