Interplay of computational chemistry and transient absorption spectroscopy in the ultrafast studies

Pritchina, Elena A.; Gritsan, Nina P.; Burdziński, Gotard; Platz, Matthew S.

doi:10.1007/s10947-007-0149-y

Cited by 3 publications

(2 citation statements)

References 20 publications

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“…Here, we investigated the excited state dynamics of 2,6-bis(diphenylamino)anthraquinone (DPA-AQ-DPA), which is a candidate for a red TADF emitter, using femtosecond transient absorption (TA) spectroscopy and kinetics analysis aided by singular value decomposition (SVD). Quinone compounds with a carbonyl group exist in natural photosynthesis systems and play an important role as electron and hydrogen atom acceptors. − DPA-AQ-DPA, which contains two diphenylamino groups (DPA) as D and one anthraquinone (AQ) as A, can be considered a multibranched molecule with two linear ICT moieties (Figure ). The results presented in this study reveal that structural change, such as twisting between DPA and AQ moieties, takes place more slowly than the charge transfer between DPA and AQ.…”

Section: Introductionmentioning

confidence: 99%

Charge Transfer-Induced Torsional Dynamics in the Excited State of 2,6-Bis(diphenylamino)anthraquinone

et al. 2017

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Intramolecular charge transfer (ICT) in a multibranched push–pull chromophore is a key photophysical process which is attracting attention due to its relevance to the development of highly efficient organic light-emitting diodes, but the excited-state dynamics of multibranched push–pull chromophores is still unclear. Here, using femtosecond transient absorption spectroscopy and singular value decomposition analysis, we studied the excited state dynamics of 2,6-bis(diphenylamino)anthraquinone (DPA-AQ-DPA), which contains two diphenylamino (DPA) groups as electron-donors (D) and anthraquinone (AQ) as an electron-acceptor (A) and is a candidate for an efficient red TADF (thermally activated delayed fluorescence) emitter. The emission of DPA-AQ-DPA exhibits large Stokes shifts with increasing solvent polarity, indicating that the emission can be attributed to an ICT process. The charge separated (CS) state formed by ICT undergoes torsional dynamics, involving twisting between D and A, resulting in the formation of a twisted charge separated state (CStwisting). This twisting reaction between D and A is accelerated in high-polarity solvents compared with that in low-polarity solvents. Such faster CT-induced torsional dynamics in high-polarity solvents is explained in terms of the localization of ICT on one of two ICT branches, suggesting that DPA-AQ-DPA in localized CStwisting formed in high-polarity solvents has two different dihedral angles between a single A group and two D groups. On the other hand, with increasing solvent polarity, the CS and CStwisting states of DPA-AQ-DPA become stabilized, making their energy levels considerably lower than that of 3(π,π*), consequently blocking the formation of the triplet excited state and TADF in a high-polarity solvent such as acetonitrile. By contrast, the energy levels of CS and CStwisting states in a low-polarity solvent, such as diethyl ether, are higher than that of 3(π,π*), allowing for deactivation into 3DPA-AQ-DPA* through intersystem crossing. This result indicates that the energy levels of CS and CStwisting states can be adjusted by controlling aspects of the local environment, such as solvents, so that intersystem crossing can be either inhibited or promoted. In other words, the energy gap (ΔE ST) between the lowest singlet and triplet excited states for DPA-AQ-DPA can be regulated by changing the solvent polarity.

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Section: Introductionmentioning

confidence: 99%

Charge Transfer-Induced Torsional Dynamics in the Excited State of 2,6-Bis(diphenylamino)anthraquinone

et al. 2017

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“…For the parent nitrene, imidogen NH, the singlet–triplet energy gap (Δ E ST ) favors the triplet by 36 kcal/mol . By contrast, both experimental and theoretical studies have concluded that acylnitrenes 1 , particularly acetylnitrene and benzoylnitrene, have closed-shell ground states of singlet multiplicity. − (Early computational studies , have clearly been superseded by more recent work. )…”

Section: Introductionmentioning

confidence: 99%

Computational Rationalization for the Observed Ground-State Multiplicities of Fluorinated Acylnitrenes

Sherman

Jenks

2014

J. Org. Chem.

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Computational methods are used to investigate the mechanism by which fluorination of acetylnitrene reduces the stabilization of the singlet configuration. ΔEST is made more positive (favoring the triplet state) by 1.9, 1.3, and 0.7 kcal/mol by the addition of the first, second, and third fluorine, respectively, at the CR-CC(2,3)/6-311(3df,2p)//B3LYP/6-31G(d,p) level of theory. Smaller effects observed with substitution of β-fluorines in propanoylnitrene derivatives and examination of molecular geometries and orbitals demonstrate that the effect is due to inductive electron withdrawal by the fluorines, rather than hyperconjugation. ABSTRACT: Computational methods are used to investigate the mechanism by which fluorination of acetylnitrene reduces the stabilization of the singlet configuration. ΔE ST is made more positive (favoring the triplet state) by 1.9, 1.3, and 0.7 kcal/mol by the addition of the first, second, and third fluorine, respectively, at the CR-CC(2,3)/6-311(3df,2p)//B3LYP/ 6-31G(d,p) level of theory. Smaller effects observed with substitution of β-fluorines in propanoylnitrene derivatives and examination of molecular geometries and orbitals demonstrate that the effect is due to inductive electron withdrawal by the fluorines, rather than hyperconjugation.

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A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

Irigoyen-Campuzano

González‐Béjar

Pino

et al. 2017

Chemistry A European J

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Heterogeneous catalysts that can absorb light over the solar range are ideal for green photocatalysis. Recently, attention has been directed towards the generation of novel solar-light photocatalysts, in particular, metal-free polymers. Herein, it is demonstrated that a metal-free, nonconjugated, anthraquinone-based copolymer (poly[1,4-diamine-9,10-dioxoanthracene-alt-(benzene-1,4-dioic acid)] (COP)) with a strong absorption in the visible region is effective as a sunlight heterogeneous photocatalyst. As a proof of concept, it has been used to mineralize 2,5-dichlorophenol (2,5-DCP) in water under air and sunlight irradiation. The photocatalytic efficiency of COP compares well with that of TiO -P25 when the reaction is carried out in a solar photoreactor in acid medium. Steady-state and time-resolved (absorption and emission) studies performed on COP suspended in 6:4 DMF/H O have provided valuable information about the COP species generated under different pH conditions. Steady-state absorption and fluorescence data are consistent with the existence of a tautomeric equilibrium between the 9,10-keto and 1,10-iminoketo quinoid forms for the anthraquinone in the ground state. Moreover, in basic media, transient absorption measurements showed the presence of two bands ascribed to the tautomeric triplet excited states, whereas only one of the triplets was observed in acid medium. A mechanism for the photocatalyzed degradation of 2,5-DCP by COP is proposed on the basis of these observations.

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Interplay of computational chemistry and transient absorption spectroscopy in the ultrafast studies

Cited by 3 publications

References 20 publications

Charge Transfer-Induced Torsional Dynamics in the Excited State of 2,6-Bis(diphenylamino)anthraquinone

Charge Transfer-Induced Torsional Dynamics in the Excited State of 2,6-Bis(diphenylamino)anthraquinone

Computational Rationalization for the Observed Ground-State Multiplicities of Fluorinated Acylnitrenes

A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

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