Abstract: The design of materials on the base of azulene-embedded benzenoid nanographenes and polycyclic aromatic hydrocarbons (PAHs) has garnered a steadily growing interest in the recent decade due to their unique electronic properties originating from the azulene core. While a huge success has been achieved in applying these PAHs in optoelectronic devices due to narrow HOMO-LUMO gap and near-infrared absorption, the potential for exploiting another azulene's intrinsic feature – anti-Kasha emission - remains unrealized. In this work, we employ non-adiabatic dynamics to study the excited state relaxation for two representative examples of azulene-embedded PAHs featuring azulene-naphthalene and azulene-phenyl cores, Az2Nap2 and Az2Ph2, and reveal the ultrafast decay of the S2 state for both compounds in the picosecond range. According to the analysis of the vibronic coupling constants and normal modes associated with them, three key factors drive such rapid excited state relaxation: i) symmetry reduction from C2v (azulene) to C2 (PAHs); ii) the intrinsic vibrational activity of the azulene core, which remains active upon embedding it into PAH and iii) the vibrational activity of groups which bridge or fuse azulene units into a single PAH molecule. These findings challenge the well-known assumption that enhanced rigidity in azulene-embedded PAHs impedes non-radiative decay pathways and favors anti-Kasha emission, thus highlighting fundamental limitations for designing such materials. We establish that the strategic design of PAHs with maximized S2–S1 energy gaps must supersede the pursuit of structural rigidification as the paramount strategy for achieving efficient anti-Kasha emission.

Cite: Shekhovtsov N.A. , Bushuev M.B.
Can azulene-embedded nanographenes achieve efficient anti-Kasha fluorescence? Insights from non-adiabatic dynamics
Journal of Photochemistry and Photobiology A-chemistry. 2026. V.474. 117012 :1-10. DOI: 10.1016/j.jphotochem.2025.117012 WOS Scopus

Dates:

Submitted:	Oct 10, 2025
Accepted:	Dec 22, 2025
Published online:	Dec 24, 2025
Published print:	May 1, 2026

Identifiers:

Web of science:	WOS:001653282900001
Scopus:	2-s2.0-105025694813

Citing: Пока нет цитирований

Altmetrics: