Chiral macrocyclic lanthanide complexes derived from (R)-2,2′-diamino-1,1′-binaphthyl: X-ray crystal structure and luminescence studies

Abstract

The template condensation of (R)-2,2′-diamino-1,1′-binaphthyl and 2,6-diformylpyridine in the presence of lanthanide(III) nitrates was used to obtain new Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Yb(III) complexes of the chiral hexaaza Schiff base macrocycle L. The complexes have been characterised on the basis of ESI MS spectrometry, NMR spectroscopy and elemental analyses. The X-ray crystal structure of Eu(III) complex reveals highly twisted helical conformation of the macrocycle L. The 10-coordinate Eu(III) ion is coordinated by all six nitrogen atoms of the macrocycle and two additional bidentate nitrate anions. Emission and excitation spectra as well as luminescence decay time measurements (at 295 and 77 K) were used to characterize the photophysical properties of the Eu(III), Gd(III) and Yb(III) complexes in the solid-state. Energy transfer from ligand to the Eu(III) and Yb(III) ions has been demonstrated and thermally activated back energy transfer processes have been analyzed.