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Light-Assisted Akamptisomerization: Excited-State Bond-Angle Reflection (ESBAR) as a Molecular Photoswitching Element in B 2 OF 2 –Porphyrins

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Akamptisomerism arises from bond-angle reflection (BAR) at a B–O–B bridge in low-symmetry B 2 OF 2 porphyrins and leads to isolable diastereisomers in the ground state. Herein, we present the first theoretical investigation of the excited-state bond-angle reflection (ESBAR). TD-DFT calculations show that the BAR activation barrier decreases from 21.3 kcal mol –1 (0.924 eV) in the ground-state (S 0 ) to 15.3 kcal mol –1 (0.663 eV) in the triplet excited-state (T 1 ), rendering the process fluxional upon excitation. The feasibility of singlet–triplet intersystem crossing is supported by near-isoenergetic singlet and triplet states and enhanced spin–orbit coupling. These results provide substantial evidence that akamptisomerism could be facilitated in the excited state, highlighting ESBAR as a potential photoswitching mechanism in porphyrinoid systems.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.6c00108

Authors: Karine N. de Andrade, Jhonathan Rosa de Souza, Paula Homem-de-Mello, Rodolfo G. Fiorot

Institutions: Universidade Federal Fluminense, Universidade Federal do ABC, Universitat de Barcelona

Language: English

Topic: Porphyrin and Phthalocyanine Chemistry

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos