Excited state dipole moments and lifetimes of 2-cyanoindole from rotationally resolved electronic Stark spectroscopy

Hebestreit, Marie-Luise; Lartian, Hilda; Henrichs, Christian; Kühnemuth, Ralf; Meerts, W. Leo; Schmitt, Michaël

doi:10.1039/d1cp00097g

Cited by 5 publications

(3 citation statements)

References 46 publications

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“…Curiously, both TD-DFT and CIS calculations indicate very weak oscillator strength for the S 1 ← S 0 transition of the perpendicular conformer (see Table ). Side-chain conformation in substituted benzenes is known to affect p-orbital orientation and electronic transition dipole moment (TDM) alignment, and in the case of non-symmetrically aligned substituents, L a / L b state mixing may result. , The lower energy L b (S 1 ) state is considered to comprise chiefly HOMO → LUMO and HOMO–1 → LUMO+1 excitations where the TDM contributions largely cancel, resulting in small overall oscillator strengths . In the case of cyclopropyl substituents, a perpendicular conformation appears to lead to near-complete cancellation of those TDM contributions.…”

Section: Resultsmentioning

confidence: 99%

“…26,27 The lower energy L b (S 1 ) state is considered to comprise chiefly HOMO → LUMO and HOMO−1 → LUMO+1 excitations where the TDM contributions largely cancel, resulting in small overall oscillator strengths. 28 In the case of cyclopropyl substituents, a perpendicular conformation appears to lead to near-complete cancellation of those TDM contributions. Thus, both the orientation and the magnitude of the TDM are seen to be very sensitive to the details of sidechain geometry.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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When Phenyl and Cyclopropyl Rings Meet: Spectroscopic Shifts and Conformational Questions

Villani,

Mohire,

Robertson

2023

J. Phys. Chem. A

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The electronic and vibrational spectra of cyclopropylbenzene (CPB) and 1,3-bromocyclopropylbenzene (BrCPB) in the gas phase were investigated using quantum chemical calculations in combination with resonance-enhanced multi-photon ionization REMPI techniques including 1c-R2PI, UV−UV holeburning, and IR-UV ion depletion in the CH stretch region. The electronic spectra revealed the presence of a single conformer for both species, with the absence of any perpendicular conformer attributed to low computed barriers to conformer interconversion. Assignment of CPB to the bisected conformer was made through interpreting distinctive CH stretch bands in the IR-UV spectrum in conjunction with quantum chemical calculations. A local anharmonic model based on DFT calculations was adapted to reproduce the cyclopropyl CH stretch spectrum successfully. It was not feasible to definitively assign which bisected conformer of BrCPB was observed using vibrational information alone due to the close similarity of their predicted IR spectra. However, conformational sensitivity of the S 1 ← S 0 transition dipole moment (TDM) alignments leads to simulated rotational contours that display stark differences, which prompted assignment to the "B1" bisecting conformer with the cyclopropyl ring directed away from the bromine atom. The absence of the energetically comparable "B2" conformer is unexpected. The analysis of the convolution of aromatic and aliphatic modes serves as a basis for assignment in constrained aliphatic systems.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

When Phenyl and Cyclopropyl Rings Meet: Spectroscopic Shifts and Conformational Questions

Villani,

Mohire,

Robertson

2023

J. Phys. Chem. A

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“…Fluorescent microscopy makes use of fluorescent proteins (FPs) [60] , [61] , [62] , [63] , [64] , [65] , [66] , [67] , [68] , [69] , [70] , [71] , [72] , [73] , [74] , [75] , [76] , [77] , [78] , [79] , [80] , [81] , [82] , [83] , [84] , [85] , [86] , [87] , [88] , [89] , [90] , [91] , [92] , [93] , [94] , [95] , [96] , [97] , [98] , [99] , [100] , [101] , [102] , [103] to label target proteins and monitor their localisation in cells, for example, and reveal information about the target protein's relationships with other molecules within cells. It has become an essential tool in biology and the biomedical sciences.…”

Section: Conformational Changesmentioning

confidence: 99%

Applications of fluorescence spectroscopy in protein conformational changes and intermolecular contacts

et al. 2023

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The photophysics of 2-cyanoindole probed by femtosecond spectroscopy

Morshedi

Nolden

Janke

et al. 2022

Photochem Photobiol Sci

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The photophysics of 2-cyanoindole (2-CI) in solution (water, 2,2,2-trifluoroethanol, acetonitrile‚ and tetrahydrofuran) was investigated by steady-state as well as time resolved fluorescence and absorption spectroscopy. The fluorescence quantum yield of 2-cyanoindole is strongly sensitive to the solvent. In water the quantum yield is as low as 4.4 × 10–4. In tetrahydrofuran, it amounts to a yield of 0.057. For 2-CI dissolved in water, a bi-exponential fluorescence decay with time constants of ∼1 ps and ∼8 ps is observed. For short wavelength excitation (266 nm) the initial fluorescence anisotropy is close to zero. For excitation with 310 nm it amounts to 0.2. In water, femtosecond transient absorption reveals that the fluorescence decay is solely due to internal conversion to the ground state. In aprotic solvents, the fluorescence decay takes much longer (acetonitrile: ∼900 ps, tetrahydrofuran: ∼2.6 ns) and intersystem crossing contributes. Graphical abstract

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Excited state dipole moments and lifetimes of 2-cyanoindole from rotationally resolved electronic Stark spectroscopy

Abstract: The rotationally resolved electronic spectrum of 2-cyanoindole has been measured and analyzed using evolutionary strategies. Dipole moments, transition dipole, and life time of the isolated molecule have been extracted and compared to ab initio calculations.

Cited by 5 publications

References 46 publications

When Phenyl and Cyclopropyl Rings Meet: Spectroscopic Shifts and Conformational Questions

When Phenyl and Cyclopropyl Rings Meet: Spectroscopic Shifts and Conformational Questions

Applications of fluorescence spectroscopy in protein conformational changes and intermolecular contacts

The photophysics of 2-cyanoindole probed by femtosecond spectroscopy

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