Design of Multichannel Osmium-Based Metalloreceptor for Anions and Cations by Taking Profit from Metal–Ligand Interaction and Construction of Molecular Keypad Lock and Memory Device

A polypyridylimidazole-based
bifunctional Os­(II) complex of the type [(bpy)2Os­(tpy-Hbzim-dipy)]­(ClO4)2 (1), where tpy-Hbzim-dipy = 4′-[4-(4,5-dipyridin-2-yl-1H-imidazol-2-yl)-phenyl]-2,2′;6′,2″-terpyridine
and bpy = 2,2′-bipyridine, has been synthesized and structurally
characterized for the construction of multifunctional logic devices.
After coordination of an [Os­(bpy)2]2+ unit to
one of the two bidentate chelating sites, the complex offers a terpyridine
motif for binding with cationic guests and an imidazole moiety for
interacting with selective anionic species. Consequently, the anion-
and cation-binding aspects of the metallorecptor were examined in
solution and in the solid state by different spectroscopic and electrochemical
methods. The complex behaves as a bifunctional sensor for F–, AcO–, CN–, Fe2+,
and Cu2+ ions in acetonitrile, whereas it is a highly selective
chromogenic chemosensor for only CN– and Fe2+ ions in water. Based on various output signals with a particular
set of anionic and cationic inputs, the complex mimics the functions
of two-input INHIBIT, OR, NOR, and XNOR logic gates, as well as three-input
NOR logic behavior. More importantly, the complicated functions of
a keypad lock and memory device were also nicely demonstrated by the
complex. Finally, density functional theory (DFT) and time-dependent
density functional theory (TD-DFT) calculations also provide a rationale
for properly understanding and interpreting the experimentally observed
results.