Synthesis Of A Novel Schiff Base And Studies Of Its Catalytic And Ion Recognition Properties

In this article,five kinds of Salen-M(Ⅲ)catalysts were synthesized by coordinating the ketal Schiff base derivatives with five kinds of metal ions.In order to explore the optimum conditions for the copolymerization of CO2 and propylene oxide,the catalytic efficiency of five catalysts were compared by applying them in copolymerization of CO2 and propylene oxide.These polymers were characterized and their thermodynamic properties were investigated,which catalyzed by the five catalysts under the optimum conditions.In addition,the recognition properties of ketal Schiff bases and quaternary ammonium salts toward some common metal ions were also investigated.The detailed research contents are as follows:Firstly,p-hydroxyphenethyl alcohol was used as a raw material to synthesize a novel ketal Schiff base through methylation reaction,Friedel-Crafts reaction,hydrolysis reaction,substitution reaction and condensation reaction.Then,the quaternary ammonium salt derivative was prepared by modifying Schiff base with triethylamine and BF4-.At the same time,the structure of various intermediates,Schiff base and quaternary ammonium salts were characterized.The Salen-M(III)catalysts were formed via reaction of the ligand with five metal ions,such as Co3+,Cr3+,Fe3+,Mn3+ and Ni3+,at the same time,2,4-dinitrophenoxy was introduced as both the axial anion X-and the counter anion Y-.Under the same conditions,the five kinds of Salen-M(Ⅲ)catalysts were respectively applied in the copolymerization of CO2 and propylene oxide,and the influences on the polymerization were investigated by changing the polymerization conditions.The results show that Salen-Co(III)catalyst has the highest catalytic efficiency,which TON was 1125,and the molecular weight of the formed polymer was 101435,PDI of polymer was 1.15.And the reaction temperature was 30℃,CO2 pressure was 2MPa,the reaction time was 24h,which were the optimum reaction conditions for the polymerization.Under the optimum reaction conditions,the structure characterization and thermodynamic properties of the polymers preparing by five Salen-M(III)catalysts were studied.It was found that the thermodynamics of the polymer by Salen-Co(III)has the best performance,and the glass transition temperature(Tg)of the polymer was 46.19 ℃.UV-vis absorption,fluorescence emission spectroscopy and cyclic voltammetry(CV)were exploited to investigate salen ligand(L1)and its quaternary ammonium salt(L2)recognition toward various metal ions,including Na+,K+,Mg2+,Al3+,Zn2+,Ag+,Pb2+,Co2+,Li+,Ba2+,Ca2+,Cd2+,La3+,Cu2+ and Mn2+ ions.The results indicated that the sensor L1 and L2 exhibited highly selective and sensitive recognition for Zn2+ions.The binding stoichiometry ratio of L1-Zn2+/L2-Zn2+ were recognized as 4:1 by the method of Job’s plot.Meanwhile,this investigation was confirmed by 1H-NMR.