A dipole moment study on gradually hindered N-phenylpyrroles

Lumbroso, H.; Bertin, Daniel; Marschner, F.

doi:10.1016/0022-2860(88)85017-8

Cited by 26 publications

(28 citation statements)

References 45 publications

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“…Previous estimates of the ground-state dipole moment of 1PP include a measured value of |1.39| D (in benzene solution at 30 °C) and calculated values (for a twisted structure) of −1.51, −1.3, and −1.9 D . The negative sign of the dipole of ground-state 1PP indicates that the center of negative charge is located on the pyrrole ring, which agrees with chemical intuition (see II ).…”

supporting

confidence: 64%

Stark-Effect Studies of 1-Phenylpyrrole in the Gas Phase. Dipole Reversal upon Electronic Excitation

Thomas

Young

Fleisher

et al. 2010

J. Phys. Chem. Lett.

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High-resolution fluorescence excitation experiments on 1-phenylpyrrole in a molecular beam, both in the absence and presence of an applied electric field, show that the electronic state responsible for the strong features in the gas-phase UVabsorption spectrum is the 1 L b state, that this state is significantly more planar than the ground state, and that the direction of the permanent electric dipole moment in the 1 L b state is reversed relative to that of the ground state. Implications of these findings for intramolecular charge transfer in the isolated molecule are discussed.

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supporting

confidence: 64%

Stark-Effect Studies of 1-Phenylpyrrole in the Gas Phase. Dipole Reversal upon Electronic Excitation

Thomas

Young

Fleisher

et al. 2010

J. Phys. Chem. Lett.

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“…The measured µ g values are Ϫ1.39 D (PP) and 3.24 D (PP4C). 34 For PP4C, the experimental ICT dipole moments reported here have values between those calculated for µ e (PICT) and µ e (TICT), whereas our data for PP are closer to µ e (TICT), favouring the TICT structure. The theoretical dipole moment for the planar LE state of PP (around Ϫ1.0 D), 16,19 similar to the negative value obtained here (see above), may indicate that a reversal of the positive and negative charge distribution on the pyrrole and phenyl or cyanophenyl moieties of PP and PP4C does indeed not occur upon excitation from S 0 to LE.…”

Section: Comparison With Theoretical Values Of the S 0 Le And Ict Di...supporting

confidence: 50%

“…Ground state dipole moments µ g , to be used in connection with eqn. (1), are available for PP (Ϫ1.39 D), 34 PP4C (3.24 D) 34 and DMABN (6.6 D). 25 The negative sign of the dipole moment of PP indicates that the center of negative charge is located on the pyrrole ring, different from PP4C.…”

Section: Calculation Of Ground State Dipole Moments G For Pp3c and Pp4mmentioning

confidence: 99%

Singlet excited state dipole moments of dual fluorescent N-phenylpyrroles and 4-(dimethylamino)benzonitrile from solvatochromic and thermochromic spectral shifts

Yoshihara

Galievsky

Druzhinin

et al. 2003

Photochem Photobiol Sci

187

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The excited state dipole moments mue(ICT) and mue(LE) of the dual fluorescent molecules N-phenylpyrrole (PP), N-(4-cyanophenyl)pyrrole (PP4C) and N-(3-cyanophenyl)pyrrole (PP3C) are determined from solvatochromic and thermochromic measurements. It is shown that the best results are obtained when the solvatochromic as well as the thermochromic analysis of the spectral shifts is made relative to 4-(dimethylamino)benzonitrile (DMABN) as the model compound. Direct thermochromic experiments with PP4C, PP3C and DMABN in diethyl ether lead to reasonable results, but unrealistically large dipole moments mue(ICT) are found for PP, PP4C, PP3C and DMABN in acetonitrile, ethyl cyanide and n-propyl cyanide. The mue(ICT) values obtained for the N-phenylpyrroles from the thermochromic analysis in these solvents relative to DMABN (17 D) do not depend on solvent polarity: 13 D for PP, 15 D for PP4C and PP3C. The spectral shifts for the LE emission of the N-phenylpyrroles and aminobenzonitriles are much smaller than those for the ICT fluorescence, resulting in relatively small values for mue(LE). With PP and N-(4-methylphenyl)pyrrole (PP4M) the problem arises that one of the two values calculated by solving the quadratic equation for mue(LE) in the solvatochromic and thermochromic analysis cannot be discarded on photophysical or molecular grounds, as is the case for the other molecules. The experimental data for mue(ICT) of PP and PP4C are compared with theoretical values calculated for coplanar (PICT) and perpendicular (TICT) conformations of the pyrrole and phenyl or cyanophenyl groups. The experimental ICT dipole moment of PP4C has a value in between the theoretical results for mue(PICT) and mue(TICT), whereas the data for PP tend to favour the TICT configuration. It appears that in the LE state of PP and PP4M a negative charge remains on the pyrrole moiety, whereas a charge reversal takes place for the LE state of PP3C and the ICT state of PP, PP4C and PP3C.

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“…Schweke and collaborators reported the experimental vibrational spectra of 1-phenylpyrrole molecules in the vapour, argon matrix, and crystalline phases, recorded by Infrared and Raman spectroscopies [17]. A dipole moment study of several N-phenylpyrroles was obtained by Lumbroso et al [18]. Parusel [19], using DFT/MRCI calculations, studied the ground and the excited states properties of electron donor-acceptor systems, namely 1-phenylpyrrole.…”

Section: Introductionmentioning

confidence: 97%

Experimental and computational thermochemistry of 1-phenylpyrrole and 1-(4-methylphenyl)pyrrole

Santos

Silva

2010

The Journal of Chemical Thermodynamics

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A dipole moment study on gradually hindered N-phenylpyrroles

Cited by 26 publications

References 45 publications

Stark-Effect Studies of 1-Phenylpyrrole in the Gas Phase. Dipole Reversal upon Electronic Excitation

Stark-Effect Studies of 1-Phenylpyrrole in the Gas Phase. Dipole Reversal upon Electronic Excitation

Singlet excited state dipole moments of dual fluorescent N-phenylpyrroles and 4-(dimethylamino)benzonitrile from solvatochromic and thermochromic spectral shifts

Experimental and computational thermochemistry of 1-phenylpyrrole and 1-(4-methylphenyl)pyrrole

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