Understanding Photophysical Effects of Cucurbituril Encapsulation: A Model Study with Acridine Orange in the Gas Phase

Abstract

Encapsulation of dyes by cucurbituril macrocycles has proven profitable as a strategy to alter fluorescence characteristics in useful ways. Encapsulation generally results in longer fluorescence lifetimes, enhanced brightness, and solvatochromic effects not normally seen in the condensed phase. These effects have been attributed variously to both the removal of interactions with solvent molecules and to the confined environment of extremely low polarizability provided by the cucurbituril interior. It is difficult to disentangle these effects in solution. Here, we present results from gas-phase experiments designed to separate these effects, using cucurbit[7]uril (CB7), and the cationic dye acridine orange (AOH(+)) as a probe. Fluorescence properties of gaseous AOH(+) are compared with those of the gaseous AOH(+)-CB7 complex and with the properties of the dye and complex in aqueous solution. The dependence on the local environment of several spectroscopic properties is discussed, including the fluorescence excitation and emission maxima, the size of the Stokes shift, fluorescence lifetime and relative brightness. An understanding of the modulation of fluorescence properties by the local environment, such as that promoted by this work, will aid in the rational design of improved fluorophores and fluorescent sensors.

Photochemical behavior of biosupramolecular assemblies of photosensitizers, cucurbit[n]urils and albumins

“…However, there is no formation of a ternary complex with HSA. This is probably because unlike AO + , that protrudes out of the cavity of CB [7], 84,85 MB + is fully included in the cavity of CB [7] as previous studies suggest. 59,71 For MB + in the presence of CB [7], the photo-oxidation of HSA was lower compared to the sample in the absence of CB [7] (figure 5 inset).…”

Recent Progress in Gas Phase Cucurbit[n]uril Chemistry

“…Czar et al studied the encapsulation of cationic acridine orange (AOH + ) dyes by CB [7] in the gas phase to probe the influence of the removal of interactions with solvent molecules and the confined, low polarizability environment provided by CBs on the enhanced fluorescence lifetime and brightness of the dye. [12] Fluorescence properties of gaseous AOH + were compared with those of the gaseous AOH + -CB [7] complex and with the properties of the dye and complex in aqueous solution. In these four different micro-environments, an increased Stokes shift was observed with increasing polarizability.…”

Absorption and Emission Spectra of a Flexible Dye in Solution: A Computational Time-Dependent Approach

“…32,33 Several applications in recent years confirm the reliability and robustness of the GLOB and other related approaches. [34][35][36][37][38][39][40][41][42] Although the classical MD step can be performed also employing conventional periodic conditions in order to use standard codes (here GROMACS), NPBCs are more suitable for QM computations based on localized basis sets. Then the extraction of representative frames can be carried out following different schemes.…”