Hidden Heterometallic Interaction Emerges from Resonant Inelastic X-ray Scattering in Luminescent Tb–Pt Molecules

Theoretical calculations are typically utilized for examining intermetallic interactions. However, to validate theory, experimental confirmation of the existence of these interactions is necessary. We synthesized new heterometallic Ln–Pt complexes, NEt4{[Pt(PhSAc)4]Ln[(PhSAc)4Pt]}·2DMF (Ln: lanthanoid = Gd (1), Tb (2), Dy (3), PhSAc = benzothioacetate, NEt4 = tetraethylammonium), in which both diamagnetic Pt(II) ions interact with the central Ln(III) ion. Typically, these interactions are not detected, because the distance between Ln and Pt atoms (~3.6 Å) is much larger than the covalent radius (~3.3 Å) and ionic radius (~3.10 Å). Pt-LIII resonant inelastic X-ray scattering (RIXS) analysis was conducted to experimentally confirm the unique influence of the hidden Ln–Pt interaction on the luminescence of the Tb–Pt molecule, where the interaction induced emission properties in the Tb and Pt ions, with high quantum yield (59%). Quantum theory of atoms in molecules (QTAIM) analysis was also used to confirm the experimental results. RIXS analysis allowed the identification of several distinctive characteristics of the coordination environment, including the existence of heterometallic interactions, that affected the observed luminescence.