Intramolecular Dynamics of Asymmetric Lanthanide(III) Porphyrin Sandwich Complexes in Solution

Abstract

Temperature dependencies of the 1H NMR spectra of asymmetric double-decker complexes of DyH(oep)(tpp) (I) and LuH(oep)(tpp) (II), where tpp is tetraphenylporphyrin and oep is octaethylporphyrin, have been analyzed. The kinetic and thermodynamic parameters for intramolecular phenyl ring rotations have been determined. The rotation in (I) is characterized by k(298 K) = 11.4 s−1, ΔH‡ = 48.0±6.0 kJ mol−1, while in (II) the derived parameters are found to be k(298 K) = 14.0 s−1, ΔH‡ = 65.5±7.1 kJ mol−1. The possible reasons for the different characteristics of these complexes are discussed. The structural parameters calculated for I and YbH(oep)(tpp) (III), indicate close similarities between the complexes. Nevertheless, it appears that the principal values of the molar paramagnetic susceptibility tensor (χi) differ significantly in these complexes.