Physics

Nanotechnology

Organic chemistry

Fission

Singlet fission

Excited state

Atomic physics

Neutron

Chemical-mechanical planarization

Nuclear physics

Chemistry

Materials science

Acene

Cyclooctatetraene

Layer (electronics)

Molecule

Singlet state

Photochemistry

Angewandte Chemie International Edition

A set of flapping acene dimers fused with an 8π cyclooctatetraene (COT) ring showed distinct excited‐state dynamics in solution. While the anthracene dimer showed a fast V‐shaped‐to‐planar conformational change within 10 ps in the lowest excited singlet state, reminding us of extended Baird aromaticity, the tetracene dimer and the pentacene dimer underwent intramolecular singlet fission (SF) in different manners: A fast and reversible SF with a characteristic delayed fluorescence (FL), and a fast and quantitative SF, respectively. Conformational flexibility of the fused COT linkage plays an important role in these ultrafast dynamics, demonstrating the utility of the flapping molecular series as a versatile platform for designing photofunctional systems.

Conformational Planarization versus Singlet Fission: Distinct Excited‐State Dynamics of Cyclooctatetraene‐Fused Acene Dimers