Ultrafast photoexcitation dynamics of π-conjugated bodipy-anthracene-radical triad system

Kanemoto, Katsuichi; Fukunaga, Atsushi; Yasui, Motoaki; Kosumi, Daisuke; Hashimoto, Hideki; Tamekuni, Hirotaka; Kawahara, Y.; Takemoto, Yohei; Takeuchi, Jun; Miura, Yozo; Teki, Yoshio

doi:10.1039/c2ra20473h

Cited by 20 publications

(26 citation statements)

References 42 publications

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“…In a nitroxide radical labeled NDI, the ISC takes approximately 338 ps . In a bodipy–anthracene–verdazyl triad, charge separation occurs within 120 ps upon photoexcitation …”

Section: Resultsmentioning

confidence: 99%

“…[17] In ab odipy-anthracene-verdazyl triad, charges eparation occurs within 120 ps upon photoexcitation. [48] We measured the fs TA spectra of the reference compounds ( Supporting Information, Figures S32-S34). ISC occurred on a timescale longert han 1.5 ns (the maximum pump-probe delay accessible with our system).…”

Section: Femtosecond Transientabsorption Spectroscopymentioning

confidence: 99%

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Intersystem Crossing in Naphthalenediimide–Oxoverdazyl Dyads: Synthesis and Study of the Photophysical Properties

Hussain

Taddei²,

Bussotti³

et al. 2019

Chemistry A European J

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Oxoverdazyl( Vz) radicalu nits were covalently linked to the naphthalenediimide (NDI) chromophore to study the effect of the radicalo nt he photophysical properties, especially the radicale nhanced intersystem crossing (REISC), which is ap romisinga pproach to develop heavyatom-free triplet photosensitizers. Rigid phenylo re thynylphenyll inkers betweent he two moieties were used, thus REISC andf ormation of doublet (D 1 ,t otal spin quantum number S = 1/2) and quartet states (Q 1 , S = 3/2) are anticipated. The photophysical properties of the dyadsw ere studied with steady-statea nd femtosecond/nanosecond transient absorption (TA) spectroscopiesa nd DFT computations. Femtosecond transienta bsorption spectras how af ast electron transfer (< 150 fs), and ISC (ca. 1.4-1.85ps) is induced by charger ecombination (CR, in toluene). Nanosecond transient absorption spectra demonstrated ab iexponential decay of the triplet state of the NDI moiety.T he fast component (lifetime:5 0ns; population ratio:8 0%)i sa ssigned to the D 1 ! D 0 decay,a nd the slow decay component (2.0 ms; 20 %) to the Q 1 !D 0 ISC. DFT computations indicated ferromagnetic interactions between the radicala nd chromophore( J = 0.07-0.13 eV). Reversible formation of the radical aniono ft he NDI moiety by photoreduction of the radical-NDI dyadsi nt he presence of sacrificial electron donor triethanolamine (TEOA) is achieved. This work is useful for design of new triplet photosensitizers based on the REISC effect.

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“…In a nitroxide radical labeled NDI, the ISC takes approximately 338 ps . In a bodipy–anthracene–verdazyl triad, charge separation occurs within 120 ps upon photoexcitation …”

Section: Resultsmentioning

confidence: 99%

Section: Femtosecond Transientabsorption Spectroscopymentioning

confidence: 99%

Intersystem Crossing in Naphthalenediimide–Oxoverdazyl Dyads: Synthesis and Study of the Photophysical Properties

Hussain

Taddei²,

Bussotti³

et al. 2019

Chemistry A European J

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“…In other words, it is possible to attain efficient ISC in radical-chromophore hybrids, yet at the same time the triplet state of the chromophore can have al ong lifetime. [50] Challenges still remaini nt he above area, for instance, the chromophores used for EISC are limited to anthracene, [41,[51][52][53] perylene, [50] perylene bisimide (PBI), [38,44] BODIPY (boron-dipyrromethene, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene), [54] and cyanine. [55] The triplet state properties of molecular systems based on EISC have not usually been studied in detail.I mportantly,t he triplet state quantum yields reported for EISC molecules are usually low and triplet lifetimes are short.…”

Section: Introductionmentioning

confidence: 99%

“…Challenges still remain in the above area, for instance, the chromophores used for EISC are limited to anthracene, perylene, perylene bisimide (PBI), BODIPY (boron‐dipyrromethene, 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐ s ‐indacene), and cyanine . The triplet state properties of molecular systems based on EISC have not usually been studied in detail.…”

Section: Introductionmentioning

confidence: 99%

Efficient Radical‐Enhanced Intersystem Crossing in an NDI‐TEMPO Dyad: Photophysics, Electron Spin Polarization, and Application in Photodynamic Therapy

Wang

Gao

Hussain

et al. 2018

Chemistry A European J

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A compact naphthalenediimide (NDI)–2,2,6,6‐tetramethylpiperidinyloxy (TEMPO) dyad has been prepared with the aim of studying radical‐enhanced intersystem crossing (EISC) and the formation of high spin states as well as electron spin polarization (ESP) dynamics. Compared with the previously reported radical–chromophore dyads, the present system shows a very high triplet state quantum yield (ΦT=74 %), a long‐lived triplet state (τT=8.7 μs), fast EISC (1/kEISC=338 ps), and absorption in the red spectral region. Time‐resolved electron paramagnetic resonance (TREPR) spectroscopy showed that, upon photoexcitation in fluid solution at room temperature, the D0 state of the TEMPO moiety produces strong emissive (E) polarization owing to the quenching of the excited singlet state of NDI by the radical moiety (electron exchange J>0). The emissive polarization then inverts into absorptive (A) polarization within about 3 μs, and then relaxes to a thermal equilibrium while quenching the triplet state of NDI. The formation and decay of the quartet state were also observed. The dyad was used as a three‐spin triplet photosensitizer for triplet–triplet annihilation upconversion (quantum yield ΦUC=2.6 %). Remarkably, when encapsulated into liposomes, the red‐light‐absorbing dyad–liposomes show good biocompatibility and excellent photodynamic therapy efficiency (phototoxicity EC50=3.22 μm), and therefore is a promising candidate for future less toxic and multifunctional photodynamic therapeutic reagents.

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“…However, instability of this compound and its homologs-hexacene and heptacene-toward light and air makes difficult their practical application [8]. To solve this problem, it was suggested to use derivatives with paramagnetic substituents showing high stability on exposure to light due to ultrafast singlet-triplet conversion of acene moiety in photoexcited states [9,10].The aim of this work is to study acenes 2 modified with two o-benzoquinone groups and their complexes with sodium cations 3 containing free-radical semiquinone (SQ) states of redox-active moieties (Fig. 2).…”

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confidence: 99%

Magnetic Properties of Acenes and Their o-Quinone Derivatives: Computer Simulation

et al. 2018

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Abstract-Quantum chemical study p)) of the structure and properties of acenes functionalized with two o-benzoquinone groups and their complexes with sodium cations has been performed. An increase in the number of fused rings has been shown to result in the stabilization of biradicaloid state of acenes and the switching of the character of exchange interactions between redox-active moieties from antiferromagnetic to ferromagnetic. The obtained results allow one to consider o-quinone acene derivatives as a basis for designing magnetoactive compounds. DOI: 10.1134/S0012500818020015Acenes 1 are the most widespread kind of fused aromatic polycyclic hydrocarbons, which are intensely studied for more than a century (Fig. 1). Doping the acene chain with electron-donating or electron-withdrawing atoms and organic or organometallic molecules allows one to vary the electronic structure of the system and provides a possibility to prepare materials with unusual electric and magnetic properties [1][2][3]. These polyaromatic compounds are considered as a basis for organic field-effect transistors [4] and organic semiconductors [5]. Considerable variation in the properties with a change in the number of fused rings is a specific feature of acenes. In particular, an increase in the length of oligomer molecule leads to a considerable decrease in the HOMO-LUMO energy gap, while compounds containing six and more rings are biradicals [6], this fact can be used in molecular electronics and spintronics [7].Pentacene is the most studied member of this series. It shows semiconducting properties and is a promising candidate for application as an organic field-effect transistor (OFET). However, instability of this compound and its homologs-hexacene and heptacene-toward light and air makes difficult their practical application [8]. To solve this problem, it was suggested to use derivatives with paramagnetic substituents showing high stability on exposure to light due to ultrafast singlet-triplet conversion of acene moiety in photoexcited states [9,10].The aim of this work is to study acenes 2 modified with two o-benzoquinone groups and their complexes with sodium cations 3 containing free-radical semiquinone (SQ) states of redox-active moieties (Fig. 2). The biradical state of acenes is expected to facilitate the appearance of supplementary exchange interactions between paramagnetic centers of complexes 3 whose character and strength may be governed by the polyacene chain length.All computations were performed with the aid of the Gaussian 09 program [11] by the density functional theory (DFT) method using the UB3LYP functional, which correctly reproduces geometrical and magnetic characteristics of open-shell compounds [12], and the standard 6-311++G(d,p) basis set. Localization of stationary points on the potential energy surface (PES) was carried out by complete optimization of molecular structure geometry with computation of force constants and verification of the DFT wave function stability. Exchange interaction parameters (J, cm -1 ) w...

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Ultrafast photoexcitation dynamics of π-conjugated bodipy-anthracene-radical triad system

Cited by 20 publications

References 42 publications

Intersystem Crossing in Naphthalenediimide–Oxoverdazyl Dyads: Synthesis and Study of the Photophysical Properties

Intersystem Crossing in Naphthalenediimide–Oxoverdazyl Dyads: Synthesis and Study of the Photophysical Properties

Efficient Radical‐Enhanced Intersystem Crossing in an NDI‐TEMPO Dyad: Photophysics, Electron Spin Polarization, and Application in Photodynamic Therapy

Magnetic Properties of Acenes and Their o-Quinone Derivatives: Computer Simulation

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