Understanding The Structure-function Relation In Natural Dyes

Understanding the relation between the structure of a molecule and the function it may express is one of the main goals of chemical physics. Natural dyes, which differ by tiny chemical details or which operate in slightly different conditions may express a broad range of colors. The question arises as to which chemical, structural, and environmental features determine the color expressed by a specific molecule in specific environments. In order to answer this questions, we have developed a multi-scale protocol, based on time-dependent density functional theory, ab initio molecular dynamics [1], and advanced sampling techniques [2], to study the optical properties of complex molecular species in realistic conditions. We apply this protocol to the most abundant natural dyes, anthocyanins, and we show that the various colors observed at different pH conditions result from a balance of chemical and dynamical effects that can be exploited, together with co-pigmentation, to identify natural variants of the same molecule with custom-designed chromatic properties.
[1]. I. Timrov et al. J. Chem. Theory Compit. 2016, 12, 4423-4429.
[2]. M. Rosa et al. J. Chem. Theory Compit. 2016, 12, 4385-4389.
[3]. M. Rusishvili et al. in preparation.