Computational study of organo-cesium complexes and the possibility of lanthanide/actinide ions substitution

Relativistic DFT calculations suggest that two organo-cesium complexes studied herein afford large HOMO-LUMO gaps of around 2.4 eV with the PBE xc-functional, which accounts for their stability. Energy decomposition studies suggest these two complexes are largely ionic with about 20% covalency. However, when the Cs⁺ ions are substituted by the isoelectronic La³⁺ and Th⁴⁺, their predicted ionicity decreases significantly. The significant increase in covalence indicates that employing Ugi reaction cascades that afford tetramic acid-based organo-cesium complexes may be extended to La³⁺ and Th⁴⁺ organometallics.