Study On Synthesis, Characterization And Catalysis Characterstics Of Rare-Earth Metal Complexes Upported By Anilido-lmine Ligands

PLA is biodegradable and biocompatible polymeric materials, it is used in the medicinal and biologic fields. Nowadays in the factory, people mainly get PLA though the ring-opening polymerization of LA. therefore fabricating catalyzer for the ring-opening polymerization of LA has attracted considerable interest in the catalytic area. However, the transition metals and late transition metal complexes as catalyzer have some disadvantages such as rigorous polymerization conditions, slow reactive speed and non-pure optic characters of polymers and some metal complexes are unhealthy for people. Recent research has found that rare earth elements are good for people's growth and rare earth complexes as cataylzer for the ring-opening polymerization of LA have many advantages for example:simply polymerization conditions, high reactive speed and quite pure optical characters of polymer so rare earth complexes have become the focus in the new catalyzer for the ring-opening polymerization of LA. In this thesis we have designed and synthesized a series of tridentate pincer ligands to form rare earth complexes, got their crystal structure and studied their catalytic capability for the ring-opening polymerization of LA.We synthesized three different N, N, N-tridentate pincer ligands with different groups in the phenyl ring and six different rare earth metal bis(alkyl)s. We determine their structure from 1H NMR. 13C NMR and element analysis and so on. From the research we found that rare earth metal complexes with 2.6-dimethyl and 2.6-diethylaniline group couldn't exist in the solvent. We analyzed the NMR spectrums of the stable complexes,and they showed an AB system for the Ln-CH2 methyleneprotons, indicating a Cs-symmetric structure in solution. We have grown four complexes crystals at-30℃and got their crystal date and determined their structures from X-Ray diffraction. And they are all Monoclinic P2(1)/n space group. All of the complexes are all solvent-free, five-coordinate monomers, even those of large lanthanide ions, such Sm3+ and Gd3+. The geometry at the metal centers is best described as distorted square pyramidal. In THF solution, we use the complexes which have got the crystal structures as catlyzer to study their reactive capability for the ring-opening polymerization of L-LA at different experimental conditions. In our experiments we mainly study how the sizes of different lanthanide ions, the function of promoter and the monomers' concentration affect the complexes for the ring-opening polymerization of L-LA. From the polymerizations date, we found that the polymerizations speed would be accelerated as the sizes of lanthanide ions increased, but the molecular weight distribution became wide; Although It is conducive to improve the rate of polymerization from adding promoter to the polymerization, the promoter could destroyed the complexes and made new derivant, so the complexes weren't the real cataylzer in this condition:when we decreased the monomers' concentration, we found the rate of polymerization would be reduced but the molecular weight distribution became narrow.