**1. Introduction**

Cyclodextrins (CDs) present oligosaccharides (between 973 and 2163 Da) composed from D-glucopyranose units (**Figure 1**) [1]. CDs are commonly classified as α-, β- and γ- CDs containing six, seven and eight glucopyranose units, respectively [2–4]. Cyclodextrins may include molecules whose size and polarity are compatible with their lipophilic interior cavity. The interaction forces participated in complexation are dipole-dipole interaction, electrostatic interaction, van der Waals interaction, dispersion forces, hydrophobic interaction, and conformational strain reduction [5, 6].

Complexation reactions involving cyclodextrins are important for two purposes: research investigations of the molecule interactions with cyclodextrin, and applied technologies (pharmaceutical chemistry, food, cosmetic, chemical synthesis and catalysis) [7–9]. It is important to note that the ability of cyclodextrins to bind guest molecules in their cavities has been used to affect the photochemical and photophysical properties of organic dyes, such as enhancement of fluorescence and

**Figure 1.** *Structures of α-, β- and γ- CDs.*

**Figure 2.** *Structure of dye DPO-β-CD complex.*

phosphorescence, intramolecular charge transfer, intermolecular hydrogen bonding, intramolecular excited proton transfer, intermolecular excimer/exciplex formation. [10–16].
