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Abstract Unraveling the intriguing aspects of the intramolecular charge transfer (ICT) phenomenon of multi‐modular donor‐acceptor‐based push–pull systems are of paramount importance considering their promising applications, particularly in solar energy harvesting and light‐emitting devices. Herein, a series of symmetrical and unsymmetrical donor‐acceptor chromophores1–6, are designed and synthesized by the Corey‐Fuchs reaction via Evano's condition followed by [2+2] cycloaddition retroelectrocyclic ring‐opening reaction with strong electron acceptors TCNE and TCNQ in good yields (~60–85 %). The photophysical, electrochemical, and computational studies are investigated to explore the effect of incorporation of strong electron acceptors 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) and dicyanoquinodimethane (DCNQ) with phenothiazine (PTZ) donor. An additional low‐lying broad absorption band extended towards the near‐infrared (NIR) region suggests charge polarization after the introduction of the electron acceptors in both symmetrical and asymmetrical systems, leading to such strong ICT bands. The electrochemical properties reveal that reduction potentials of3and6are lower than those of2and5, suggesting DCNQ imparts more on the electronic properties and hence largely contributes to the stabilization of LUMO energy levels than TCBD, in line with theoretical observations. Relative positions of the frontier orbitals on geometry‐optimized structures further support accessing donor‐acceptor sites responsible for the ICT transitions. Eventually, ultrafast carrier dynamics of the photoinduced species are investigated by femtosecond transient absorption studies to identify their spectral characteristics and target analysis further provides information about different excited states photophysical events including ICT and their associated time profiles. The key findings obtained here related to excited state dynamical processes of these newly synthesized systems are believed to be significant in advancing their prospect of utilization in solar energy conversion and related photonic applications.
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Intramolecular Charge Transfer in Antiaromatic Donor/Acceptor‐Fused s ‐Indacenes
Abstract Herein we report the synthesis and characterization of four donor/acceptor‐fuseds‐indacenes via the late‐stage oxidation of a family of unsymmetrical benzofuran/benzothiophene‐s‐indacene regioisomers. A thorough study of their properties through experimental and computational analysis has revealed the effect of asymmetry on the molecular properties associated with antiaromaticity, as well as a strong correlation between antiaromaticity and intramolecular charge transfer (ICT). The strength of the charge transfer depends on the fusion orientation of the donor and acceptor motifs relative to thes‐indacene core. The two most antiaromatic oxidized isomers exhibit strong evidence of ICT with 30 and 40 nm solvatochromic shifts.
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- Award ID(s):
- 2246964
- PAR ID:
- 10595926
- Publisher / Repository:
- Wiley-VCH
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 64
- Issue:
- 9
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/anie.202420989
