Spodium bonding to anticrown-Hg3 boosts phosphorescence of cyclometalated-PtII complexes

The moderately phosphorescent platinum(ii) complexes [Pt(ppy)(acac)] (1; ppyH = 2-phenylpyridine, acacH = acetylacetone), [Pt(ppy)(hd)] (2; hdH = heptanedione-3,5), [Pt(ppy)(tmhd)] (3; tmhdH = 2,2,6,6-tetramethylheptanedione-3,5), [Pt(dfppy)(acac)] (4; dfppyH = 2-(2′,4′-difluorophenyl)pyridine), and [Pt(dfppy)(tmhd)] (5) were precipitated on cocrystallization with anticrown Hg3(1,2-C6F4)3 (Hg3) to give HgII-PtII stacked heteroplanar architectures (1-3)·Hg3 and (4-5)·Hg3·Me2CO. Synchrotron X-ray diffraction studies of these cocrystals along with in-depth theoretical density functional theory (DFT; PBE0-D3BJ) calculations, employing a set of computational tools (QTAIM, ELF, IGMH, MEP, CDF, ETS-NOCV, and SAPT methods), allowed the recognition of the spodium bonds Hg⋯Pt and Hg⋯C (the former is significantly stronger than the latter) as the stacking-directing contacts. The major part (57%) of the total interaction energy between 3 and Hg3 (−32.9 kcal mol−1), as a model system, comes from Hg⋯Pt bonding. Heteroplanar stacking is mostly controlled by dispersion and electrostatic forces, but the dz(Pt) → σ*(Hg-C) charge transfer also provides a noticeable contribution; HgII functions as an electrophilic component of the Hg⋯Pt and Hg⋯C contacts. The spodium bond-driven supramolecular integration provides enhanced phosphorescence lifetimes and up to 6-fold solid-state quantum yield enhancement for all cocrystals compared to the parent PtII species. Appropriate DFT studies along with the analysis of calculated radiative and nonradiative decay rate constants indicate that the heteroplanar stacking reduces the population of the 3MC state, thus increasing the quantum yield. © 2023 The Royal Society of Chemistry.