Computational Study of the Structure of a Sepiolite/Thioindigo Mayan Pigment

• Main Authors: Manuel Alvarado, Russell C. Chianelli, Roy M. Arrowood
• Format: Article
• Language: English
• Published: Hindawi Limited 2012-01-01
• Series: Bioinorganic Chemistry and Applications
• Online Access: http://dx.doi.org/10.1155/2012/672562

The interaction of thioindigo and the phyllosilicate clay sepiolite is investigated using density functional theory (DFT) and molecular orbital theory (MO). The best fit to experimental UV/Vis spectra occurs when a single thioindigo molecule attaches via Van der Waals forces to a tetrahedrally coordinated cation with an additional nearby tetrahedrally coordinated also present. The thioindigo molecule distorts from its planar structure, a behavior consistent with a color change. Due to the weak interaction between thioindigo and sepiolite we conclude that the thioindigo molecule must be trapped in a channel, an observation consistent with previous experimental studies. Future computational studies will look at the interaction of indigo with sepiolite.