Does Twisted π-Conjugation Framework Always Induce Efficient Intersystem Crossing? A Case Study with Benzo[<i>b</i>]- and [<i>a</i>]Phenanthrene-Fused BODIPY Derivatives and Identification of a Dark State

Yan, Yizhou; Sukhanov, Andrei A.; Bousquet, Manon H. E.; Guan, Qing‐Lin; Zhao, Jianzhang; Воронкова, В. К.; Escudero, Daniel; Barbon, Antonio; Ye, Xing; Gurzadyan, Gagik G.; Jacquemin, Denis

doi:10.1021/acs.jpcb.1c03189

Cited by 28 publications

(31 citation statements)

References 124 publications

(298 reference statements)

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“…Recently we and others studied the ISC and the triplet state of a few twisted BDP derivatives. − First, we noted a previously reported naphtho[ b ]-fused BDP ( helical-BDP-1 . Figure ).…”

Section: Discussionsupporting

confidence: 85%

“…We carried out magnetophotoselection measurements; i.e., the TREPR spectra were recorded by aligning of the excitation laser polarization direction perpendicular or parallel to the magnetic field (Figure ). With simulation of these spectra, the angle between the S 0 → S 2 transition dipole moment and the ZFS Z principal axis was determined as 10° …”

Section: Discussionsupporting

confidence: 63%

“…0.1%), and a short fluorescence lifetime was observed (ca. 150 ps) . For BDP-P , the molecular structure is more twisted, with a torsion angle of the BDP core of ca.…”

Section: Discussionmentioning

confidence: 81%

“…The study showed that the UV–vis absorption band of the compound is broad, but no detailed photophysical property was reported. We determined the molecular structure by single crystal X-ray diffraction; the deviation from planarity is small, only ca. 4.2°.…”

Section: Discussionmentioning

confidence: 99%

“…BDP derivatives with twisted molecular structures BDP-B , and BDP-P . Reproduced with permission from ref .…”

Section: Discussionmentioning

confidence: 99%

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Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

2021

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Intersystem crossing (ISC) is one of the fundamental photophysical processes. Achieving efficient ISC is critical in the design of triplet photosensitizers and also in the study of photochemistry. Most of the previous studies on ISC and the triplet state are focused on the kinetics of the ISC, the quantum yield, or the lifetime of the triplet states, with femtosecond or nanosecond transient absorption spectroscopic methods. However, another fundamental feature of ISC, i.e., the electron spin selectivity, or the electron spin polarization (ESP) of the triplet state, was much less studied, especially for the newly developed triplet photosensitizers. These features characterize the non-Boltzmann populated sublevels of the T1 state. Herein we summarized the recent progress on the study of the electron spin selectivity of ISC and the ESP of the T1 state of the triplet photosensitizers that show strong absorption of visible light and a long lifetime of the triplet state. The electron spin selectivity of the compact orthogonal electron donor–acceptor dyads (spin–orbit charge transfer ISC mechanism) and compounds with twisted π-conjugation molecular structures, studied with the time-resolved electron paramagnetic resonance (TREPR) spectroscopy, are discussed.

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“…Recently we and others studied the ISC and the triplet state of a few twisted BDP derivatives. − First, we noted a previously reported naphtho[ b ]-fused BDP ( helical-BDP-1 . Figure ).…”

Section: Discussionsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 63%

“…0.1%), and a short fluorescence lifetime was observed (ca. 150 ps) . For BDP-P , the molecular structure is more twisted, with a torsion angle of the BDP core of ca.…”

Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 99%

“…BDP derivatives with twisted molecular structures BDP-B , and BDP-P . Reproduced with permission from ref .…”

Section: Discussionmentioning

confidence: 99%

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Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

2021

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BOPAM: Efficient Synthesis of a Bright Asymmetric Bis‐Boron Complex and its Dark Side

Huang,

de Jong,

Elisa van Raamsdonk

et al. 2023

Advanced Optical Materials

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A new family of unsymmetrical boron chromophores chelated with two BF2 units, named BOPAM, has been developed via a one‐pot, three‐step reaction starting from commercially available thioamides via i) conversion to amidrazones, ii) condensation with pyrrole aldehydes, and iii) boron chelation. This synthetic pathway has been proven to be highly efficient, having a broad substrate tolerance and giving the BOPAM products high yield. Notably, some of the BOPAM dyes show interesting photophysical properties with fluorescence quantum yields up to 0.98 in toluene. A fine‐tuning of their emissive properties has been attained through tailored molecular design strategies guided by in‐depth computational investigations. Tailored substitution with electron‐donating groups at the BOPAM ring leads to the opening of a non‐radiative decay channel involving a dark state and consequently a significant quenching of the fluorescence. The study is complemented by exhaustive steady‐state and time‐resolved spectroscopic measurements.

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Design and Synthesis of BODIPY‐Hetero[5]helicenes as Heavy‐Atom‐Free Triplet Photosensitizers for Photodynamic Therapy of Cancer

Koli

Gupta

Chakraborty

et al. 2023

Chemistry A European J

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Designing heavy‐atom‐free triplet photosensitizers (PSs) is a challenge for the efficient photodynamic therapy (PDT) of cancer. Helicenes are twisted polycyclic aromatic hydrocarbons (PAHs) with an efficient intersystem crossing (ISC) that is proportional to their twisting angle. But their difficult syntheses and weak absorption profile in the visible spectral region restrict their use as heavy‐atom‐free triplet PSs for PDT. On the other hand, boron‐containing PAHs, BODIPYs are highly recognized for their outstanding optical properties. However, planar BODIPY dyes has low ISC and thus they are not very effective as PDT agents. We have designed and synthesized fused compounds containing both BODIPY and hetero[5]helicene structures to develop red‐shifted chromophores with efficient ISC. One of the pyrrole units of the BODIPY core was also replaced by a thiazole unit to further enhance the triplet conversion. All the fused compounds have helical structure, and their twisting angles are also increased by substitutions at the boron centre. The helical structures of the BODIPY‐hetero[5]helicenes were confirmed by X‐ray crystallography and DFT structure optimization. The designed BODIPY‐hetero[5]helicenes showed superior optical properties and high ISC with respect to [5]helicene. Interestingly their ISC efficiencies increase proportionally with their twisting angles. This is the first report on the relationship between the twisting angle and the ISC efficiency in twisted BODIPY‐based compounds. Theoretical calculations showed that energy gap of the S1 and T1 states decreases in BODIPY‐hetero[5]helicene as compared to planar BODIPY. This enhances the ISC rate in BODIPY‐hetero[5]helicene, which is responsible for their high generation of singlet oxygen. Finally, their potential applications as PDT agents were investigated, and one BODIPY‐hetero[5]helicene showed efficient cancer cell killing upon photo‐exposure. This new design strategy will be very useful for the future development of heavy‐atom‐free PDT agents.

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Does Twisted π-Conjugation Framework Always Induce Efficient Intersystem Crossing? A Case Study with Benzo[b]- and [a]Phenanthrene-Fused BODIPY Derivatives and Identification of a Dark State

Cited by 28 publications

References 124 publications

Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

BOPAM: Efficient Synthesis of a Bright Asymmetric Bis‐Boron Complex and its Dark Side

Design and Synthesis of BODIPY‐Hetero[5]helicenes as Heavy‐Atom‐Free Triplet Photosensitizers for Photodynamic Therapy of Cancer

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