Polarizable chromophores for photonic applications: environmental and intermolecular interactions

Abstract

Polarizable chromophores are highly responsive to external perturbations, such as polar solvation and intermolecular interactions. The comprehension of the impact of the surrounding medium on the optical properties of polarizable dyes sets the basis for their exploitation in molecular materials and devices, acting as a tool to tailor the optoelectronic response according to the specific needs. In this Work we performed a joint computational and spectroscopic investigation on a selection of representative molecular and supramolecular systems, analysing and rationalizing in a coherent picture the effects promoted by: i) interactions with the solvent; ii) homomolecular interactions in aggregates (dimers, crystals, nanoassemblies); iii) intermolecular interactions in heterobichromophoric systems (dyads). The relationship between electronic and chemical structure of solvated chromophores was thoroughly examined, with emphasis on the description of solvatochromism, symmetry breaking and the development of suitable essential-state models. Aggregation effects were addressed at a theoretical and experimental level, relating the spectroscopic properties of aggregates to the supramolecular organization, the nature of the coupling, and aggregation conditions, providing guidelines for the exploitation of collective and cooperative behaviour to tune the properties through aggregation. Lastly, we performed the detailed characterization of a few calix[4]arene-based dyads undergoing energy and/or electron transfer, gaining more insights into the factors affecting the efficiency and dynamics of the processes, and also proposing an innovative functional application in molecular thermometry. This Thesis offers a contribution to the understanding of the interplay between the chemical structure and environmental and intermolecular contributions to the optical properties of polar and polarizable dyes, paving the way to their knowledge-based exploitation in photonic devices.