The effect of rigidity on the emission of quadrupolar strongly polarized dyes

Hybrid dyes comprising 1,4-dihydropyrrolo[3,2-b]pyrrole and two strongly electron-withdrawing benzoxadiazole substituents, differing in their level of planarization, offer an insightful window into the interplay between internal conversion and intersystem crossing as relaxation pathways from the excited state. The emission intensity is strong for non-fused systems whilst it is minimal for fused dyes. Computational evaluation has revealed that internal conversion, and not inter-system crossing, is the main non-radiative process for planar, fused quadrupolar dyes.

Polish National Science Center, (grants OPUS 2020/37/B/ST4/00017 and 2019/33/B/ST4/03144); grant no. 324139 of the Research Council of Norway; Ministry of Education and Science of Ukraine for support (Project No. 0121U107533); European Union within the European Regional Development Fund (program no. POIG.02.01.00-14.122/09); National Academic Infrastructure for Supercomputing in Sweden (NAISS 2023/5-77) at the National Supercomputer Centre (NSC) at Linko¨ping University partially funded by the Swedish Research Council through grant agreement no. 2022-06725; Swedish Research Council through starting grant no. 2020-04600; Olle Engkvists Stiftelse (Sweden), project number 212-0136.