Introducing the new concept of a chiral-polaron giant-IRAV signature, optical-active giant-response in vibrational circular dichroism

Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds of primary importance in the field of organic semiconductors, with applications in both organic electronics and photovoltaics. This paper delves into two strictly related topics. First, the theoretical rationalization of the physical factors underlying the emergence of the polaron "giant-response infrared active vibrations (IRAVs)" signature in positively charged PAHs. Results are presented concerning the tight comparison between the experimental results and theoretical results obtained within different DFT paradigms (BLYP, B3LYP, CAM-B3LYP and LC-BLYP) and the pure Hartree-Fock Hamiltonian. This allowed the rationalization of the emergence of the giant IRAV response as essentially propelled by long-range electronic interactions. Moreover, the role of vibrational modes and molecular dimensions (topology) is addressed. Second, the analysis is extended to chiral [4]helicene. This allows the introduction of a new concept yet to be explored experimentally: the chiral-polaron giant-IRAV signature in vibrational circular dichroism (VCD) spectra.