Curcumin, the primary natural dye from the spice turmeric, has been of recent interest due to its possible health benefits as an antioxidant and possible anti cancer and anti Alzheimer's properties.   Limited solubility and instability in water are of primary importance when considering curcumin's possible uses as a pharmaceutical.  DFT computations were carried out using B3LYP and MO6 density functionals and the SMD solvent model for water.  TDDFT computations were carried out on geometries optimized in water as described by the SMD solvent model.  It is found that M06 with the 3-21G* basis set and SMD solvent model gives accurate λ<sub>max</sub>  values though the larger 6-31+G* basis set is needed for accurate description of the trianionic protonation state.  The 6-31+G* basis set is also needed for accurate computation of pKa values.  The particle-in-a-box model gives unexpectedly good agreement with computational λ<sub>max</sub> values when delocalization of phenolic lone pair electrons are appropriately considered in the different protonation states and  box lengths from optimized geometries are used.  This gives a simple model of how the electronic structure of curcumin is influenced by protonation state and is in good agreement with both computation and experiment.

Study of the protonation states of the curcumin molecule and their visible absorption spectra in aqueous solution using M06, SMD, and TDDFT and compared to experiment

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.