Excited State Properties of Lanthanide(III) Complexes with a Nonadentate Bispidine Ligand.

Eu , Tb , Gd and Yb complexes of the nonadentate bispidine derivative L (bispidine=3,7-diazabicyclo[3.3.1]nonane) were successfully synthesized and their emission properties studied. The X-ray crystallography reveals full encapsulation by the nonadentate ligand L that enforces to all Ln cations a common highly symmetrical capped square antiprismatic (CSAPR) coordination geometry (pseudo C symmetry). The well-resolved identical emission spectra in solid state and in solution confirm equal structures in both media. As therefore expected, this results in long-lived excited states and high emission quantum yields ([Eu L ] , H O, 298 K, τ=1.51 ms, ϕ=0.35; [Tb L ] , H O, 298 K, τ=1.95 ms, ϕ=0.68). Together with the very high kinetic and thermodynamic stabilities, these complexes are a possible basis for interesting biological probes.