Striking solvent dependence of total emission and circularly polarised luminescence in coordinatively saturated chiral europium complexes: solvation significantly perturbs the ligand field

Examination of total emission and circularly polarised luminescence (CPL) spectra of three 9-coordinate Eu(iii) complexes with well-defined speciation shows that the ligand fields of these C-3 symmetric complexes are extremely sensitive to solvent polarity, even when solvent is not present in the first coordination sphere. The energies, intensities, and (for CPL) the sign of some transitions vary with solvent polarity. These observations are rationalised by analysis of the factors that control total and circularly polarised emission, and have important implications for design of responsive luminescent Ln(iii) probes.

Automated summary

The examination of total emission and circularly polarised luminescence (CPL) spectra of three 9-coordinate Eu(iii) complexes with well-defined speciation demonstrates that the ligand fields of these C-3 symmetric complexes are highly sensitive to solvent polarity, even if the solvent is not present in the first coordination sphere. The variations in energies, intensities, and sign of transitions with solvent polarity are rationalized through analysis of the factors influencing total and circularly polarised emission, with important implications for the design of responsive luminescent Ln(iii) probes.