Density functional dependence of molecular geometries in lanthanide(III) complexes relevant to bioanalytical and biomedical applications

► The performance of different density functionals to predict the geometries of LnIII complexes has been evaluated. ► Meta-GGA functionals and hybrid meta-GGA functional TPSSh perform better than hybrid GGA and GGA functionals. ► The use of large-core RECPs provides somewhat longer LnIII-donor distances than the SCRECP approach. ► Including solvent effects is important to obtain a more accurate description of the structures of LnIII complexes in solution.