What is it about?

Understanding if hydration can change the preferential orientation of chromophores may be of key relevance for designing hybrid functional materials for solar energy harvesting. To unravel the role of water, we have studied the cationic dye methylacridine inside the monodimensional channels of Zeolite L. Such dye is small enough to have a large freedom of movement inside the host; for this reason, it is very difficult to deduce experimentally the orientation of the molecule with respect to the zeolite channel axis. In this work, we determined the exact orientation of the dye and the influence of water by modeling the methylacridine-zeolite L composite at both dry and wet conditions.

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Why is it important?

For the first time, the anisotropic orientation of a small cationic dye inside a zeolite channel is unambiguously determined and understood. We found that the most stable orientation is mainly determined by electrostatic interactions and can be tuned by water. More specifically, the finding that inside the zeolite the dye is hydrogen bonded neither to water nor to framework oxygens - hence, it is hydrophobically solvated by water molecules - is quite remarkable. This means that the environment of the chromophore inside the zeolite is similar to that in liquid water, thus explaining the experimental observation of similar electronic properties for this dye in water and in the hydrated composite.


We understood some important working principles of dye-zeolite functional materials, which could be very useful for future progress in applications. For example, our work supports the appealing hypothesis that a good choice of the solvent can greatly improve the opto-electronic properties of dye-zeolite composites. On the whole, the molecular-level knowledge of these materials attained in this work may help to extend their applications into exciting new areas.

Gloria Tabacchi
university of insubria

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This page is a summary of: Host–Guest Interactions and Orientation of Dyes in the One-Dimensional Channels of Zeolite L, Langmuir, July 2013, American Chemical Society (ACS),
DOI: 10.1021/la400579w.
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