Studies On Extraction And Complexation Behavior Of Novel N,O-Hybrid Phenanthroline Derived Ligands Towards F-block Elements

Although the carbon reduction policy has been proposed in China,the growth of the national economy is closely related to the consumption of energy.Currently,a energy with low carbon emission is urgently demanded to meet the rapid economic development.Nuclear energy,a safe,stable and low-carbon energy,is quiet suitable for this need.The construction of a closed-loop nuclear energy cycle system has been implemented to recover and dispose of the spent nuclear fuel safely and effectively.The’Partitioning&Transmutation’ strategy is the most effective technique to dispose the long-periodic radioactive nuclides in high-level radioactive waste.In this process,the separation of trivalent lanthanides and actinides plays key roles to ensure the transmutation efficiency.In this project,we designed and synthesized three types of preorganized N,O-hybrid phenanthroline ligands,N,N-diethyl-N,N-dimethyl-1,10phenanthroline-2,9-diamide(Et-Ph-DAPhen),2,9-diethylphenylphosphoryl-1,10phenanthroline(Et-Ph-BPPhen)and diethyl((1,10-phenanthroline)-2,9-diyl)diphenyl hypophosphite(Et-Ph-PIPhen).The extraction and complexation properties of them with trivalent lanthanides and actinides were investigated.The relevant results are as followed:(1)The amide ligand(Et-Ph-DAPhen)had a very significant separation ability to Am(Ⅲ)but the extraction property was not well.And two complexes with the ligand/Ln(Ⅲ)ratio of 2:1 and 1:1 were formed in the complexation of Et-Ph-DAPhen with both La(Ⅲ)and Eu(Ⅲ),while only 1:1 complex of Et-Ph-DAPhen with Lu(Ⅲ)was formed.The log β values of Et-Ph-DAPhen decreased gradually with the lanthanide contraction and a fluorescence quenching effect was shown in the titration of Eu(Ⅲ)with Et-Ph-DAPhen.The single-crystal structures with Ligand/La(NO3)3 of 2:1 and 1:1,Ligand/Eu(NO3)3 of 1:1 and Ligand/Lu(NO3)3 of 1:1 were obtained.(2)The extraction ability of phosphine oxide ligands(Et-Ph-BPPhen)was great but this ligand had almost no separation ability of Am(Ⅲ)towards Eu(Ⅲ).Only 1:1 complex was formed when complexing with La(Ⅲ),while two complexes with ligand/Ln(Ⅲ)ratios of 2:1 and 1:1 were formed in complexation of Et-Ph-BPPhen with both Lu(Ⅲ)and Eu(Ⅲ).The log β values of Et-Ph-BPPhen gradually increased with the lanthanide contraction and a fluorescence enhancement effect was shown in the titration of Eu(Ⅲ)with Et-Ph-BPPhen.1:1 single-crystal structures of Et-Ph-BPPhen with all La(NO3)3,Eu(NO3)3 and Lu(NO3)3 were cultivated.(3)The extraction ability of Et-Ph-PIPhen obtained by inserting ester O atoms to Et-Ph-BPPhen was further improved,and the separation performance was also increased.The formation trend of complex species,the change of log β values with lanthanide contraction and the fluorescence effect of Et-Ph-PIPhen was found.1:1 single-crystal structures of Et-Ph-PIPhen with both La(NO3)3 and Eu(NO3)3 were acquired.The coordination cavities of the three ligands decreased with the lanthanide contraction and the average bond lengths of Eu-OL were consistent with the extraction results and the first-order log β values of Eu(Ⅲ).In this study,the extraction and complexation properties of the three types of ligands with the same substituent groups were systematacially compared and the feasibility of modifying the electron density of O donor atoms on the N,O-hybrid phenanthroline ligands was verified.