**Conflict of interest**

*Solvents, Ionic Liquids and Solvent Effects*

In a general view of absorption results, selected anthocyanidins in gas phase had absorption wavelength between 479.1 and 536.4 nm so, all selected molecules work in the visible part of the electromagnetic spectrum. Cyanidin works in the blue region and displays lower values calculated for wavelength. Malvidin has higher values while cyanidin presents a similar value. These results suggest that there is an effect caused by the small relative angle at B ring considering that these molecules are the simplest regarding their constituents. Addition of solvent shifts the absorption spectrum by increasing its wavelength by <5 nm in the case of water, ethanol, and methanol. For n-hexane solvent,

*Anthocyanidin excited state spectra from results using the TD-DFT scheme for gas phase and solvents water,* 

*ethane, n-hexane, and methane corresponding to: (a) cyanidin, (b) malvidin, and (c) peonidin.*

First excited state values using TDDFT to calculate absorption data are displayed in **Table 5** and absorption spectrum is shown in **Figure 5**. The visible and near-UV regions are the most important for photon-to-current conversion to obtain the microscopic information about the electronic transitions and their corresponding MO properties.

Ground state geometries were analyzed using a well-known theoretical methodology, and an analysis on their relative angles comparing dihedrals within individual rings provides insight into the different planarity characteristics between rings and establishes that functionalization with OCH3 is an important feature for the structural and energy gap differences. Molecular orbitals are analyzed and compared with our results from prior research for TiO2, the more widely used photocatalyst. These results mainly with MO analysis show that there is good compatibility between the semiconducting oxide and these pigments if they are to be used as dye sensitizers. Malvidin in its gas phase has a lower value for gap energy and with addition of solvents, gap energy increases in all cases but malvidin with n-hexane is the narrower. Conceptual DFT results show that cyanidin and malvidin may have good charge transfer. Furthermore, excited state data display the absorption capabilities of the selected pigments and confirm that cyanidin and malvidin, in that order, may

This work was financed by CONACyT (Mexican Science and Technology National Council) through 2015 CONACyT SEP-CB (Basic Science-Public

absorption spectrum shifts the wavelength by slightly more than 10 nm.

be the best choices for dye sensitization applications.

**200**

**Acknowledgements**

**5. Conclusions**

**Figure 5.**

Authors state that this research was completed without any conflicts of interest related with funding to develop the present work.
