Dimeric Cycloparaphenylenes with a Rigid Aromatic Linker.

Dimeric cycloparaphenylene (CPP) architectures with well-defined flipping motion are constructed taking advantage of an efficient cyclocondensation reaction. Variable-temperature nuclear magnetic resonance (VT-NMR) analyses and theoretical calculations indicate rapid interconversion of cis and trans conformers at room temperature, while energetically favorable trans conformer exists at low temperature with the metastable cis conformer hidden. The trihexylsilylethynyl-substituted dimer exhibits bright emission in solution at 616 nm with quantum yield up to 80 %, representing the brightest CPP-based emitter beyond 600 nm. A 1:2 host-guest complex of the dimer and C60 is established with negative cooperativity, demonstrating the first example of 1:2 complex from CPP derivatives.