This tutorial provides a comprehensive description of the origin of chiroptical properties of supramolecular and plasmonic assemblies in the UV–visible region of the electromagnetic spectrum. The photophysical concepts essential for understanding chiroptical signatures are presented in the first section. Just as the oscillator strength (a positive quantity) is related to absorption, the rotational strength (either a positive or a negative quantity) defines the emergence of chiroptical signatures in molecular/plasmonic systems. In supramolecular systems, induced circular dichroism (ICD) originates through the off-resonance coupling of transition dipoles in chiral inclusion complexes, while exciton coupled circular dichroism (ECD) originates through the on-resonance exciton coupling of transition dipoles in chiral assemblies resulting in the formation of a bisignated CD signal. In bisignated ECD spectra, the sign of the couplet is determined not only by the handedness of chiral supramolecular assemblies, but also by the sign of the interaction energy between transition dipoles. Plasmonic chirality is briefly addressed in the last section, focusing on inherent chirality, induced chirality, and surface plasmon-coupled circular dichroism (SP-CD). The oscillator strength is of the order of 1 in molecular systems, while it becomes very large (10⁴–10⁵) in plasmonic systems due to the collective plasmonic excitations, resulting in intense CD signals, which can be exploited for the design of plasmonic metamaterial platforms for chiral sensing applications.

In this paper we present the synthesis, spectroscopic characterization and theoretical modelling of two pairs of correlated dipolar and octupolar donor–acceptor conjugated chromophores, based on the triphenylamine branching centre. The two pairs of chromophores differ for the electron withdrawing end-groups. Linear absorption, fluorescence and two-photon absorption of all the compounds in different solvents can be well described by the use of charge-resonance theoretical models based on essential-state descriptions of the electronic structure, and taking into account the coupling to effective molecular vibrations and to polar solvation degrees of freedom. On the contrary, the alternative Frenkel exciton model does not provide a good description of the observed behavior. The robustness of the proposed theoretical models is demonstrated for the first time by the fact that the modulation of a single molecular parameter (the one linked to the electron-withdrawing ability of the end groups) is enough to describe the evolution of the spectroscopic properties along the whole series of chromophores, both “intra-pair” and “inter-pair”. The effectiveness of the approach suggests that this kind of theoretical modelling can be very useful to predict different properties of the compounds at hand or of correlated structures of increasing complexity, such as dendrons and dendrimers, giving a guide to the synthesis of (macro)molecules for applications in light-emitting and nonlinear optical devices, artificial light-harvesting systems or optical imaging of living tissues.

Essential-state models, validated against TD-DFT, rationalize the ultra-excitonic effects observed in the experimental spectra of aggregates of polarizable quadrupolar dyes.

Exciton chirality rule for assigning the handedness of supramolecular aggregates is rephrased by accounting for the nature of intermolecular interactions.

TADF offers a promising way to harvest triplets in OLED for improved efficiency. To concurrently optimize the dye inside the matrix, a thorough experimental and theoretical study is presented of a the TADF dye addressing environmental effects.