Isomerization and redox tuning in 'Maya yellow' hybrids from flavonoid dyes plus palygorskite and kaolinite clays

The composition of the organic fraction of organic-inorganic hybrid materials prepared upon attachment of different natural, 'historical' flavonoid yellow dyes (zacatlaxcalli, fustic, marigold and cosmos) to palygorskite and kaolinite clays is described. Upon thermal treatment between 100 and 180 degrees C, significant isomerization and oxidation reactions occur thus resulting in the formation of polyfunctional materials potentially usable for therapeutic, catalytic and art purposes. The dye attachment to the clays would define a 'Maya chemistry' whose complexity could explain the versatile use of such materials in the pre-Columbian cultures. (C) 2014 Elsevier Inc. All rights reserved.