Thermodynamic Stability of Heterodimetallic [LnLn′] Complexes: Synthesis and DFT Studies

The solid‐state and solution configurations of the heterodimetallic complexes (Hpy)[LaEr(HL)3(NO3)(py)(H2O)] (1), (Hpy)[CeEr(HL)3(NO3)(py)(H2O)] (2), (Hpy)[CeGd(HL)3(NO3)(py)(H2O)] (3), (Hpy)[PrSm(HL)3(NO3)(py)(H2O)] (4), and (Hpy)2[LaYb(HL)3(NO3)(H2O)](NO3) (5), in which H3L is 6‐(3‐oxo‐3‐(2‐hydroxyphenyl)propionyl)pyridine‐2‐carboxylic acid and py is pyridine, were analyzed experimentally and by using DFT calculations. Complexes 3, 4, and 5 are described here for the first time, and were analyzed by using single‐crystal X‐ray diffraction and mass spectrometry. The theoretical study was also extended to the [LaCe] and [LaLu] analogues. The results are consistent with a remarkable selectivity of the metal distribution within the molecule in the solid state, enhanced by the size difference between the different ions. This selectivity was reduced in solution, particularly for ions with the most similar radii. This unique entry into 4f–4f′′ heterometallic chemistry establishes for the first time the difference between the selectivity in solution and that in the solid state, as a result of changes to the coordination that follow the dissociation of terminal ligands upon dissolution of the complexes. Dilanthanide complexes: The solid‐state and solution configurations of a range of heterodimetallic lanthanide complexes (see figure) have been investigated by using experimental techniques and DFT calculations. These complexes show a remarkable selectivity for the metal distribution in the solid state, which was enhanced as the size difference between the metal ions increased, but this effect was reduced in solution, particularly for ions of similar size.