Eu(III)-Based Metallo-Supramolecular Polymer

Abstract

This chapter introduces synthesis and vapoluminescence of Eu(III)-based metallo-supramolecular polymer (polyEuL18) and synthesis and emission switching of Eu(III)/Fe(II)-based heterometallo-supramolecular polymer (polyEuFeL19). Unlike transition metal ions, lanthanide ions such as Eu(III) ions have 8–10 coordination sites. A new ditopic ligand is necessary to introduce such metal ions into a metallo-supramolecular polymer backbone. Section 11.1 shows synthetic procedure of bis(terpyridine) substituted with four carboxylic acids (L18), which has total ten coordination atoms. A Eu(III)-based metallo-supramolecular polymer (polyEuL18) is prepared by the 1:1 complexation of Eu(III) ions with L18. Section 11.2 describes vapoluminescence of the polymer. The polymer film exhibits bright-red emission under a UV lamp. The photoluminescence of the polyEuL18 film can be switched off and on by exposure to acidic or basic vapor. Such behavior is called vapoluminescence. Section 11.3 describes synthesis of Eu(III)/Fe(II)-based heterometallo-supramolecular polymer (polyEuFeL19) by the complexation of Eu(III), Fe(II), and L19. L19 is an asymmetrical ligand with a carboxylic acids-substituted terpyridine moiety and non-substituted terpyridine moiety. The intensity of the emission peaks is very low compared with that of polyEuL18 because of the energy transfer from Eu(III) to the Fe(II)-terpyridine moiety. Section 11.4 exhibits emission switching in polyEuFeL19, triggered by electrochemical redox between Fe(II) and Fe(III).