Two dinuclear lanthanide complexes based on a salicylamide imine multidentate ligand: Synthesis, structure and NIR emission properties

Abstract Two dinuclear lanthanide complexes, [Er 2 (HL) 2 (NO 3 ) 4 ]∙2CH 3 CN∙CH 3 OH( 1 ) and [Yb 2 (HL) 2 (NO 3 ) 4 ]∙3CH 3 CN∙CH 3 OH ( 2 ) based on a salicylamide imine multidentate ligand, H 3 L = 1-(2-hydroxy-benzamido)-2-(3-hydroxy-naphthaleneamino)-ethane, were prepared and well characterized by elemental analysis, IR spectra, thermogravimetric analysis as well as X-ray diffraction analysis. Single crystal X-ray diffraction shows that the two phenol oxygen atom bridged dinuclear compounds are isomorphous where two deprotoned HL 2– ligands possess the same coordination mode with the naphtol and amide oxygen atom coordinating to one Er(III) ion and phenol oxygen atom from salicylamide bridging two Er(III) ions. Photophysical studies indicates that 1 and 2 exhibit near-infrared emissions characteristic of Er(III) and Yb(III) ions and these effective sensitizations are approved by DFT calculation. The results presented herein indicate that the deprotoned HL 2– not only offers a good protection for Er(III) and Yb(III) ions but also exhibits a good antennae effect with respect to Er(III) and Yb(III) ions as a result of efficient ligand to metal energy transfer.