Trimeric perfluoro-ortho-phenylene mercury as a building block for supramolecular materials

Abstract

Trimeric perfluoro-ortho-phenylene mercury (1) constitutes one of the simplest trifunctional Lewis acidic hosts. Cooperative effects arising from the proximity of the mercury(II) centers, the electron-withdrawing properties of the backbone and the accessibility of the electrophilic sites leads to the facile complexation of neutral and electron rich substrates. The planarity of the structure as well as its overall polarizability compounded with relativistic effects at mercury also permits the occurrence of non-covalent interactions. The main objective of this dissertation was to explore the potential of 1 as a building block for supramolecular materials. Compound 1 was investigated using single crystal x-ray diffraction and was found to display a rich polymorphism. The electronic structure, probed by DFT methods, shows that the LUMO of 1 has a large contribution from the mercury 6p orbitals and features a large lobe protruding above and below the center of the trinuclear mercury core. Complexes in which two nitronyl nitroxide radicals (NIT-Ph = 2-(phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) coordinate to the trinuclear core of 1 above and below the Hg3 plane reveal that 1 does not significantly mediate magnetic interactions. The ability of 1 to complex π-basic molecules such as tetrathiafulvalene (TTF), toluene, o-xylene, m-xylene, p-xylene, mesitylene, biphenyl, naphthalene, acenaphthalene, anthracene, pyrene, triphenylene, perylene, and coronene was also investigated and show that 1 and arenes form extended binary stacks in which the two components alternate. The photoluminescence observed in some of these supramolecular complexes corresponds to the phosphorescence of the arene indicating a mercury heavy atom effect. Complexation of 1 in solution was observed with hexaalkoxytriphenylenes (HATn, n = 1, 6) by fluorescence and NMR spectroscopy. Finally, compound 1 forms electrophilic double sandwich structures with ferrocene and nickelocene in which a molecule of 1 caps each of the Cp ligands. The nickelocene adduct is stabilized towards oxidation, and the photophysical and magnetic properties indicate the occurrence of a mercury heavy atom effect.