Blue-Colored, Linear Rigid-Axle [2]Pseudorotaxanes: Metal-Binding Properties, Crystal Structures, and Blue/Red Dichroism

Abstract

Rare blue-colored [2]pseudorotaxanes based on the previously unexplored [N,N'-bis(4-pyridyl)-4,4'-bipyridinium](2+) axle and bis(1,5-naphtho)-32-crown-8 (BN32C8) or bis(1,5-naphtho)-38-crown-10 (BN38C10) wheels have been synthesized and characterized by UV-vis, (1)H NMR spectroscopy, and electrochemistry, and their metal-binding properties toward CdI(2) and HgCl(2) have been studied by optical absorption in solution and X-ray crystallography in the solid state. We report contrasting structures of the same metal and different wheels or the same wheel and different metals. We also show for the first time that a simple metal complex, such as Hg(2)Cl(6)(2-), can induce a blue/red linear dichroism by organizing the [2]pseudorotaxane units into a columnar arrangement in the crystal.