Blue chromonics

The red, violet, and blue pigments of flower petals are called anthocyanins, and are glycosides of various benzopyrilium cations. Delphinidin chloride 9.7, for example, is a blue pigment. Khellin 9.8 is a natural product which has found clinical application in the treatment of bronchial asthma and has been the starting point for the design of many totally synthetic chromones with improved biological properties. 

The pyrano[3,2-c]xanthen-7-one exhibits the two absorption bands associated with a heteroatom at a peri position of the benzopyran nucleus. Pyrano[2,3-a]xanthen-12-one 44, in which the fusion of the chromone ring is reversed, shows an intense single band blue-shifted some 14 nm relative to 2,2-diphenyl-2//-naphtho[l,2-6]pyran [Xmax 403, 482 nm (PhMe)]. Both isomers are readily degraded <01HCA117>. It is noteworthy that 44 could not be... 

Chromones show less intense fluorescence, e.g. vfsnagin (pale blue), khellin (yellow-brown). 

Ruslim C, Matsunaga D, Hashimoto M, Tamaki T, Ichimura K. 2003. Structural characteristics of the chromonic mesophases of C.I. Direct Blue 67. Langmuir 19 3686 3691. 

Luckhurst potential, dimers 816 luminance, guest-host effect 272 lutetium, phthalocyanine ligands 924 lyotropic blue phases, chromonics 998 lyotropic systems... 

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