Chromophore Formation in Resorcinarene Solutions and the Visual Detection of Mono- and Oligosaccharides

The colorimetric properties of resorcinarene solutions had not been investigated since Baeyer's
initial synthesis. We recently reported that solutions containing resorcinarene macrocycles develop color
upon heating or standing. In the presence of saccharides, these solutions exhibit significant color changes
which are easily seen. We herein present strong evidence that the solution color is due to macrocycle ring
opening and oxidation. The optical responses to saccharides are due to complexation of the sugar with
the acyclic chromophores. We apply these mechanistic insights toward the challenging problem of the
visual detection of neutral oligosaccharides by simple chromogens. In addition, we also report the first
single-crystal X-ray crystal structure determination of a rarely observed “diamond” resorcinarene stereoisomer.