A general framework for the theory of electron–intramolecular vibration (e–mv) interaction in charge-transfer (CT) compounds is presented, particular attention being devoted to the effect of this interaction on the optical spectra of quasi-one-dimensional organic semiconductors. The common physical basis of different theoretical models of e–mv coupling is evidenced by taking into consideration an isolated CT pair. In particular, it is shown that a complete and substantially equivalent description of the phenomena is provided by the approaches based on the linear response theory or on the Herzberg–Teller coupling scheme, the latter method being developed here to its full extent. The comparison with experimental data shows that a collection of isolated CT pairs can satisfactorily model the consequences of e–mv interaction on the optical spectra of dimerized stack organic semiconductors, either of segregated or mixed type. In addition, we develop here for the first time a model also able to take into account the effect of a nonzero interdimer CT integral. Finally, the case of regular stack CT crystals is analyzed, in such a way, a complete picture of the e–mv (vibronic) perturbation on the optical spectra is obtained, putting in evidence how the spectra can be used to obtain detailed information on the structure and properties of quasi-one-dimensional organic semiconductors. The consequences of the coupling between molecular vibrations and lattice modes are also briefly investigated.

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.