Photophysics of Internal Twisting

Lippert, E.; Rettig, Wolfgang; Bonačić‐Koutecký, Vlasta; Heisel, F.; Miehé, J.A.

doi:10.1002/9780470142967.ch1

Cited by 245 publications

(127 citation statements)

References 196 publications

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“…As the temperature is lowered from room temperature, the ethanol peak shifts toward red until the temperature reaches 253 K, and after that the emission peak starts moving toward blue, indicating the beginning of orientation of fluctuating solvent dipoles. The blue shift reaches a maximum at 193 K, showing the solvent dipoles orientation also to be maximum, and after that the same shift is maintained up to 77 K. This is somewhat similar to the emission in mixed D 2 OÀethanol solvent (vide supra). But in MCH only regular red-shifted spectra were observed throughout.…”

Section: Articlesupporting

confidence: 70%

“…It may so happen that after reaching a certain dielectric constant, along with the protic character of the solvent, the ground state of the probe gets more stabilized than the excited state due to a benzenoid to quinonoid transformation. To understand the phenomenon more clearly, the emission of DASQMI in D 2 OÀethanol mixed solvents has also been studied.…”

Section: Resultsmentioning

confidence: 99%

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Spectral Signature of 2-[4-(Dimethylamino)styryl]-1-methylquinolinium Iodide: A Case of Negative Solvatochromism in Water

2011

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Photophysics of the 2-[4-(dimethylamino) styryl]-1-methylquinolinium iodide (DASQMI) molecule has been studied in different solvents by steady-state and time-resolved emission spectroscopy and also with quantum chemical calculations. The probe molecule exhibits a strong solvent-polarity-dependent characteristic. The low-energy fluorescence band of DASQMI shows an anomalous 40 nm blue shift in water from that in dimethyl sulfoxide (DMSO); though in deuterium oxide the normal trend of red shift was observed. A marked increase in intensity of this band at 77 K and an increase in lifetime in viscous solvent point clearly to the intramolecular charge-transfer (ICT) character of the low-energy band. From the temperature-dependent emission and emission spectra in mixed solvents, the negative solvatochromism of DASQMI has been established, which means that the ICT state moves toward ground state with polarity and hydrogen-bond ability and beyond a critical dielectric constant coupled with protic nature of the solvent ground state gets further stabilized to show anomalous blue shift. In ethanol, below a critical temperature, 253 K, a blue shift starts due to greater solvent molecular polarization. A third long-lifetime component with dominant 75% amplitude was observed only in aqueous solution and may be due to the cis-isomer of hydrophobic DASQMI, a stable form in the excited state predicted from polarizable continuum model (PCM) calculations in water with 6-31G+(d,p) as basis set.

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Section: Articlesupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Spectral Signature of 2-[4-(Dimethylamino)styryl]-1-methylquinolinium Iodide: A Case of Negative Solvatochromism in Water

2011

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“…According to the twisted intramolecular charge transfer (TICT) model, the charge transfer process occurs with the simultaneous twisting of the bond connecting the amino group and the benzene ring. [1][2][3][4][5] Further evidence for the TICT mechanism comes from the experimentally observed solvent dynamical control of the LE → CT conversion reaction rate. [12][13][14][15] The agreement between theory and experiments found in our earlier studies in electrolyte solutions 12,13 also provides support to the TICT mechanism for the excited state intramolecular charge transfer reaction.…”

Section: Introductionmentioning

confidence: 97%

“…[1][2][3][4][5] While potential applications of ICT molecules in designing fluorescent dyes, 6-7 electron transfer photochemistry, 8 solar collectors, 7 pH or ion indicators 9,10 have driven much of the interest in industry, quest for fully understand the basic scientific aspects of ICT reactions in various media continues to attract attention of physical chemists. Photo-induced charge transfer is an important process in biology as light-induced charge separation plays key roles in photosynthesis and vision.…”

Section: Introductionmentioning

confidence: 99%

Excited state intramolecular charge transfer reaction of 4-(morpholenyl) benzonitrile in solution: Effects of hetero atom in the donor moiety

2010

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An intramolecular charge transfer (ICT) molecule with an extra hetero atom in its donor moiety has been synthesized in order to investigate how ICT reaction is affected by hetero atom replacement. Photo-physical and photo-dynamical properties of this molecule, 4-(morpholenyl)benzonitrile (M6C), have been studied in 20 different solvents. The correlation between the reaction driving force (-ΔG r ) and activation barrier (ΔG # ) has been explored in order to understand the solvent effects (static and dynamic) on the photo-excited ICT reaction in this molecule. A Kramer's model analysis of the experimentally observed reaction rate constants indicates a solvent-averaged activation barrier of ~ 4 k B T in the absence of solvent dynamical control. The reaction in M6C is therefore not a barrier-less reaction but close to the limit where conventional kinetics might break down.

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“…A dual fluorescence of 4-dimethylaminobenzonitrile (DMABN) was also experimentally detected by Lippert et al [62]. The DMABN was considered the paradigm for investigating dual fluorescence behavior [62][63][64][65][66][67][68][69][70]. To sum up, in order to understand the nature of BN and its derivatives in hydrogen-donating solvents upon being electronically excited has triggered lots of study, but few works have been carried out on the dynamics of the hydrogen bond in these systems.…”

Section: Introductionmentioning

confidence: 99%

A theoretical forecast of the hydrogen bond changes in the electronic excited state for BN and its derivatives

Wang¹,

Hao²,

Wang³

et al. 2011

Open Physics

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Ê Ú ¼ ÖÙ ÖÝ ¾¼½½ ÔØ ¼ Ù Ù×Ø ¾¼½½ ×ØÖ ØThe relationship between electronic spectral shifts and hydrogen-bonding dynamics in electronically excited states of the hydrogen-bonded complex is put forward. Hydrogen bond strengthening will induce a redshift of the corresponding electronic spectra, while hydrogen bond weakening will cause a blueshift. Time-dependent density function theory (TDDFT) was used to study the excitation energies in both singlet and triplet electronically excited states of Benzonitrile (BN), 4-aminobenzonitrile (ABN), and 4-dimethylaminobenzonitrile (DMABN) in methanol solvents. Only the intermolecular hydrogen bond C≡N· · · H-O was involved in our system. A fairly accurate forecast of the hydrogen bond changes in lowlying electronically excited states were presented in light of a very thorough consideration of their related electronic spectra. The deduction we used to depict the trend of the hydrogen bond changes in excited states could help others understand hydrogen-bonding dynamics more effectively.

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Photophysics of Internal Twisting

Cited by 245 publications

References 196 publications

Spectral Signature of 2-[4-(Dimethylamino)styryl]-1-methylquinolinium Iodide: A Case of Negative Solvatochromism in Water

Spectral Signature of 2-[4-(Dimethylamino)styryl]-1-methylquinolinium Iodide: A Case of Negative Solvatochromism in Water

Excited state intramolecular charge transfer reaction of 4-(morpholenyl) benzonitrile in solution: Effects of hetero atom in the donor moiety

A theoretical forecast of the hydrogen bond changes in the electronic excited state for BN and its derivatives

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