Section 3 Solvent Effects

*Solvents, Ionic Liquids and Solvent Effects*

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**1. Introduction**

**Chapter 10**

**Abstract**

Solvent Effects on Dye Sensitizers

Derived from Anthocyanidins for

Applications in Photocatalysis

*Diana Barraza-Jiménez, Azael Martínez-De la Cruz,* 

*Leticia Saucedo-Mendiola, Sandra Iliana Torres-Herrera,* 

*Adolfo Padilla Mendiola, Elva Marcela Coria Quiñones,* 

*and Manuel Alberto Flores-Hidalgo*

*Raúl Armando Olvera Corral, María Estela Frías-Zepeda* 

Anthocyanidins under the effects of solvents water, ethanol, n-hexane, and methanol are interesting due to their suitability as natural dyes for photocatalytic applications. In this chapter, DFT and TDDFT methodologies are used to study their electronic structure. The results displayed include HOMO, LUMO, HOMO-LUMO gap, chemical properties, and reorganization energies for the ground states, and excited state data are also displayed. Malvidin in gas phase has lower gap energy. After addition of solvents, gap energy increases in all cases but malvidin with n-hexane presents narrower gap. Conceptual DFT results show that cyanidin and malvidin may have good charge transfer. Cyanidin presented lower electron reorganization energy (*λe*) using solvent water; however, ethanol and methanol had similar values. TDDFT is used to calculate excited states, and absorption data show wavelength main peak between 479.1 and 536.4 nm. UV-Vis absorption spectra were generated and solvent effects on each molecule is discussed. Anthocyanidins work well in the visible region with the stronger peak at the green region. These pigments are good options for photocatalysis application and cyanidin and malvidin, in this

order, may be the best choices for dye sensitization applications.

**Keywords:** anthocyanidins, dyes, solvent effects, DSSC, TDDFT

Organic pigments have raised great interest in late years, may be driven by their potential in renewable energy applications which has been reinvigorated with the invention of dye-sensitized solar cells (DSSCs). Dye-sensitized solar cells (DSCs) are an attractive solar energy conversion technology and present advantages that include low cost of manufacture, ease of fabrication, and modifiable features such as color and transparency [1–5]. First DSSCs employed ruthenium (II)-based dyes in conjunction with iodide-based electrolytes to achieve an 11.9% solar-to-electric power conversion efficiency (PCE) [6]. A new generation of DSSCs based on naturally obtained **Chapter 10**
