Transient Raman Snapshots of the Twisted Intramolecular Charge Transfer State in a Stilbazolium Dye

Karmakar, S.; Ambastha, Abhinandan; Jha, Ajay; Dharmadhikari, A. K.; Dharmadhikari, J. A.; Venkatramani, Ravindra; Dasgupta, Jyotishman

doi:10.1021/acs.jpclett.0c01124

Cited by 20 publications

(21 citation statements)

References 42 publications

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“…(see Scheme 1 c) was reported to be <5 ps and competitive with solvent relaxation. 69 It is much faster than the observed continuous relaxation process (≫80 ps), observed in this study. Therefore, the TICT process contribution toward the observed slow spectral temporal evolution for C1[BPhCl] and C2[BPhCl] can be neglected.…”

Section: Resultsmentioning

confidence: 44%

Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer

Lin

Liu

et al. 2021

JACS Au

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A series of D−π– A + pyridinium compounds, in which D = −NPh 2 and A + = −PyMe + are linked by various amounts of linear phenyl spacers, were strategically designed and synthesized. Their characterization revealed the presence of excited-state intramolecular charge transfer (ESICT) that triggers a corresponding response from the counterion. In medium and strong polar solvents, the fast solvent relaxation occurring after ESICT overwhelms the counterion effect, showing typical emission solvatochromism. In weakly polar solvents, ESICT induces counteranion migration for electrostatic stabilization, the time scale of which is dependent on the radius of the counteranion, the length of the π-linker, and the viscosity of the solvent. In low-viscosity organic solvents such as toluene, counteranion migration occurs within several tens to hundreds of picoseconds, resulting in a time-dependent continuous emission that can be resolved from the spectral temporal evolution. Concrete evidence for this is provided by the chemical synthesis of a D−π– A + pyridinium–sulfur trioxide – zwitterion, where anion migration is restricted due to its internally locked ion pair. As a result, only a single emission band can be observed. These comprehensive studies prove that the ion migration process may be significant for a wide range of ESICT-type ionic fluorophores. Such an ionic movement, triggered by optically pumped ESICT of the D−π– A + dyad, is similar to the molecular machine driven by the redox reaction, but with a facile access and fast response.

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Section: Resultsmentioning

confidence: 44%

Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer

Lin

Liu

et al. 2021

JACS Au

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“…Recently, Dasgupta and co-workers have reported the FSRS of stilbazolium dye, where the twisted ICT state in the excited state was indicated by the decoupling between the ethylenic ν C = C and the ν 8a modes of phenyl (electron donor-side) and pyridine (electron acceptor-side) rings [38]. The twist of N-methylpyridine ring and change in the molecular symmetry in the ICT state increased the Raman intensity of the ν 8a mode of pyridine ring at 1650 cm −1 , which is only infrared active with the planar geometry in the ground state.…”

Section: Twisted Ict State Of Dcmmentioning

confidence: 99%

“…No straightforward experimental evidence for the structure of the ICT state of DCM or similar push-pull dyes have been reported by now [10][11][12][13][14]25,[32][33][34][35][36][37][38]. Numerous investigations on the excited-state dynamics of DCM by using the time-resolved transient absorption and fluorescence spectroscopy have been made [11][12][13][14]25,34].…”

Section: Introductionmentioning

confidence: 99%

Twisted Intramolecular Charge Transfer State of a “Push-Pull” Emitter

Lee

Jen

Pang

2020

IJMS

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The excited state Raman spectra of 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in the locally-excited (LE) and the intramolecular charge transfer (ICT) states have been separately measured by time-resolved stimulated Raman spectroscopy. In a polar dimethylsulfoxide solution, the ultrafast ICT of DCM with a time constant of 1.0 ps was observed in addition to the vibrational relaxation in the ICT state of 4–7 ps. On the other hand, the energy of the ICT state of DCM becomes higher than that of the LE state in a less polar chloroform solution, where the initially-photoexcited ICT state with the LE state shows the ultrafast internal conversion to the LE state with a time constant of 300 fs. The excited-state Raman spectra of the LE and ICT state of DCM showed several major vibrational modes of DCM in the LE and ICT conformer states coexisting in the excited state. Comparing to the time-dependent density functional theory simulations and the experimental results of similar push-pull type molecules, a twisted geometry of the dimethylamino group is suggested for the structure of DCM in the S1/ICT state.

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“…This emissive phenomenon is attributed to the TICT effect. [49][50][51] As the water fractions (f w ) further increases from 70 to 95%, the uorescence intensity sharply recovers, exhibiting a typical AIE property, and the emission peak blue-shifts to 547 nm. Such photo-physical behaviors demonstrate that BT-LC can be viewed as a dual-state emission (DSE) molecule.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Macrocyclization-Induced Emission Enhancement of Benzothiadiazole-based Macrocycle

Bai

Cui

et al. 2021

Preprint

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We presented a novel strategy for the improvement of luminophore’s solid-state emission, i.e., macrocyclization-induced emission enhancement (MIEE), by linking luminophores through C(sp3) bridges to give a macrocycle. Benzothiadiazole-based macrocycle (BT-LC) has been synthesized by a one-step condensation of the monomer 4,7-bis(2,4-dimethoxyphenyl)-2,1,3-benzothiadiazole (BT-M) with paraformaldehyde, catalyzed by Lewis acid. BT-LC shows strong emission in both dilute solution and aggregated state. Moreover, in comparison with the monomer, macrocycle BT-LC produces much more intense fluorescence in the solid state (ΦPL=99%) and exhibits better device performance in the application of OLEDs. The MIEE can be ascribed to the restriction of intramolecular motion and the alleviation of the concentration quenching by the macrocyclic topological structure.

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Transient Raman Snapshots of the Twisted Intramolecular Charge Transfer State in a Stilbazolium Dye

Cited by 20 publications

References 42 publications

Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer

Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer

Twisted Intramolecular Charge Transfer State of a “Push-Pull” Emitter

Synthesis and Macrocyclization-Induced Emission Enhancement of Benzothiadiazole-based Macrocycle

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