Investigating the Halochromic Properties of Azo Dyes in an Aqueous Environment by Using a Combined Experimental and Theoretical Approach

• DOI: 10.1002/chem.201103633
• Publication Date: 2012-05-21T15:16:17Z
• Authors: Thierry De Meyer; Karen Hemelsoet; Lien Van der Schu...; Ewald Pauwels; Karen De Clerck; Veronique Van Spe...
• Keywords: Methyl orange; Ultraviolet visible spectroscopy

The halochromism in solution of a prototypical example an azo dye, ethyl orange, was investigated by using combined theoretical and experimental approach. Experimental UV/Vis Raman spectroscopy pointed towards structural change the dye with changing pH value (in range 5-3). pH-sensitive behavior modeled through series ab initio computations on neutral various singly doubly protonated structures. For this purpose, contemporary DFT functionals (B3LYP, CAM-B3LYP, M06) were used combination implicit modeling water solvent environment. Static calculations successful assigning most-probable protonation site. However, to fully understand origin main absorption peaks, molecular dynamics simulation study environment time-dependent (TD-DFT) deduce average spectra that take into account flexibility explicit interactions surrounding molecules. This procedure allowed us achieve remarkable agreement between spectrum enabled unravel orange aqueous