Preparation And Properties Of Multidentate Carboxylic Acid Based Rare Earth Complexes Based On Phenoxy (amine)

In this paper,three polycarboxylic ligands were synthesized by the reaction of 4-aminobenzoic acid and(R)-(+)-2-(4-hydroxyphenoxy)propionic acid,namely,N-(4-carboxyphenyl)iminodiacetic acid(H3L1),(R)-2-(4'-(4"-carboxybenzyloxy)phenoxy)propanoic acid(H2L2)and(R)-4-(4-(1-carboxyethoxy)phenoxy)-3-fluorobenzoic acid(H2L3).Based on three ligands and rare earth metals under hydrothermal conditions,four series of 24 polycarboxylate lanthanide coordination polymers have been synthesized,namely,[Ln(H3L1)(H2O)](1-4)(Ln=La,Ce,Pr,Nd),{[Ln(H3L1)(H2O)]·2H2O}n(5-12)(Ln=Sm,Eu,Gd,Tb,Dy,Ho,Er,Yb),{[Ln2(H2L2)3(H2O)3]·H2O·CH3CN}n(13-22)(Ln=La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Yb),[Ln2(H2L3)3](23,24)(Ln=Yb,Lu).Complexes 1-12 based on the ligand H3L1 feature 2D double layer structures.Complexes 1-4 and complexes 5-12 are isomorphic,respectively.The coordination modes of central metal changed from five connection of La-Nd to four connection of Sm-Yb.Therefore,two kinds of topological structures are formed with topological symbols of {48.62} and {43.63},respectively.Their thermal stability,fluorescence properties and magnetic properties are studied.Complexes 13-22 based on the ligand of H2L2 crystallize in the monoclinic space group P21 with a three-dimensional structure which can be simplified to a 3,4,5,6-c framework with a point symbol of {4·82}{44·62}2{46·64·84·10}{46·64}.The fluorescence properties of complexes 16,18 and 20 are studied.The fluorescence recognition of complex 20 toward nitrobenzene is carried out and the experimental results indicate that complex 20 is sensitive to identify nitrobenzene.Complexes 23 and 24 based on the ligand of H2L3 also show three-dimensional structure which can be simplified to a 4,4,6-c framework with a point symbol of({42·62·82}{43·63}2{47·68}2).The near infrared spectra of the complex 23 showed that complex 23 had the characteristic luminescence of Yb+3 ions.At the same time,we also measured the Circular dichroism spectra(CD),SHG and TGA of complexes 23 and 24.