Planar and twisted intramolecular charge transfer states of the excited proton transfer products of aminocoumarins

Druzhinin, S. I.; Bursulaya, Badry; Uzhinov, B. M.

doi:10.1016/1010-6030(95)04055-k

Cited by 20 publications

(17 citation statements)

References 9 publications

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“…(3) The DE a gradually increases with Df. This is an unexpected observation because with the increased solvent polarity the highly polar TICT state should undergo better stabilization and consequently the DE a corresponding to the ICT fi TICT conversion process was expected to reduce (52)(53)(54)(55)(56). Increase in DE a with Df thus indicates that the ICT fi TICT conversion is not the rate-determining step for the TICT-mediated nonradiative process for the C30 dye in high-polarity protic solvents.…”

Section: Protic Solventsmentioning

confidence: 96%

“…1A and 2A, respectively) are more or less linear for all the protic solvents studied including those having Df more than 0.28, it is indicated that the fluorescence state of the dye remains the same in all the solvents studied, which we suppose to be the same ICT structure, as also exists in moderate to higher polarity aprotic solvents. The TICT state for C30 dye, which is basically a zwitterionic structure and can be visualized as Structure IV in Scheme 3, attends a relatively more stabilization than the ICT state as the solvent polarity exceeds the critical value of Df ;0.28 and consequently introduces the new nonradiative deexcitation channel for the dye excited state, which is otherwise absent in solvents having Df less than ;0.28 (52)(53)(54)(55)(56).…”

Section: Protic Solventsmentioning

confidence: 99%

“…In 7-aminocoumarin dyes, participation of the TICT state is supposed to be determined by the electron-donating power of the 7-amino group (52)(53)(54)(55)(56). Thus, in C120 dye with weak electrondonating 7-NH 2 group, no involvement of the TICT state has been observed, even in a very high-polarity solvent (30).…”

Section: Protic Solventsmentioning

confidence: 99%

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Photophysical Properties of Coumarin-30 Dye in Aprotic and Protic Solvents of Varying Polarities¶

Senthilkumar

Nath

Pal

2004

Photochem Photobiol

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Experimental results on various photophysical properties of coumarin-30 (C30) dye, namely, Stokes' shift (Deltanu), fluorescence quantum yield (Phi(f)), fluorescence lifetime (tau(f)), radiative rate constant (k(f)) and nonradiative rate constant (k(nr)), as obtained using absorption and fluorescence measurements have been reported. Though in most of the solvents the properties of C30 show more or less linear correlation with the solvent polarity function, Deltaf = [(epsilon - 1)/(2epsilon + 1) - (n(2) - 1)/(2n(2) + 1)], they show unusual deviations in nonpolar solvents at one end and in high-polarity protic solvents at the other end. From the solvent polarity and temperature effect on the photophysical properties of the dye, following inferences have been drawn: (1) in nonpolar solvents, the dye exists in a nonpolar structure, where its 7-NEt(2) substituent adopts a pyramidal configuration and the amino lone pair is out of resonance with the benzopyrone pi cloud; (2) in medium to higher polarity solvents, the dye exists in a polar intramolecular charge transfer structure, where the 7-NEt(2) group and the 1,2-benzopyrone moiety are in the same plane and the amino lone pair is in resonance with the benzopyrone pi cloud; (3) in protic solvents, the dye-solvent intermolecular hydrogen bonding influences the photophysical properties of the dye; and (4) in high-polarity protic solvents, the excited C30 undergoes a new activation-controlled nonradiative deexcitation process because of the involvement of a twisted intramolecular charge transfer (TICT) state. Contrary to most other TICT molecules, the activation barrier for this deexcitation process in C30 is observed to increase with solvent polarity. A rational for this unusual behavior has been given on the basis of the solvent polarity-dependent stabilization and crossing of relevant electronic states and the relative propensity of interconversion among these states.

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Section: Protic Solventsmentioning

confidence: 96%

Section: Protic Solventsmentioning

confidence: 99%

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Photophysical Properties of Coumarin-30 Dye in Aprotic and Protic Solvents of Varying Polarities¶

Senthilkumar

Nath

Pal

2004

Photochem Photobiol

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“…A rearrangement of the closest environment of the molecule or a change in its structure in the excited state results in the dependence of the efficiency of fluorescence of such systems on the viscosity and polarity of the medium. 4,6 In this work, the effects of the structure of the 4-amino substituent, of the polarity and viscosity of a solvent, as well as the effect of temperature on the fluorescent properties of N-(2,4-dimethylphenyl)imides of 4-amino-1,8-naphthalenedicarboxylic acid were studied to elucidate the reasons for the different fluorescent …”

mentioning

confidence: 99%

Radiationless deactivation of excited molecules of 4-aminonaphthalimides

Dmitruk

Druzhinin

Minakova³

et al. 1997

Russ Chem Bull

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The effects of alkylation of the 4-amino group, polarity and viscosity of a solvent, and temperature on the fluorescence of N-(2,4-dimethylphenyl)imides of 4-aroino-1,8-naphthalenedicarboxylic acid were studied. A decrease in the temperature and polarity of a solvent and an increase in its viscosity cause the rate of radiationless deactivation of 4-dimethylaminonaphthalimide to decrease and have almost no effect on the rate of eroissive deactivation of excited state. The abnormally low efficiency of fluorescence of 4-dimethylaminonaphthalimide in polar low-viscosity media at room temperature is associated with the formation of a nonfluorescent charge-transfer state. The increase in the rate of radiationless deactivation of 4-aminonaphthalimide in the alkylation of its amino group is associated with the increase in its electron-donor ability.Key words: 4-aminonaphthalimide, fluorescence, radiationless deactivation, donor-acceptor interaction.Derivatives of 4-aminonaphthalimides are used as active laser media I and fluorescent labels, z The luminescent properties of these compounds are strongly dependent on the structure of the molecule and solvent. The fluorescence of naphthalimides containing the 4-amino-or 4-monoalkylamino group is characterized by a high quantum yield independent of the solvent, whereas the quantum yield of fluorescence of 4-(N,Ndialkylamino)naphthalimides is strongly dependent on the nature of the solvent, z,3 The nineteen-fold decrease in the quantum yield of fluorescence in ethanol on going from 4-amino-to 4-(N,N-dialkylamino)naphthalimide has been explained by the violation of planarity of the dialkylaminonaphthalimide molecule) The strong effect of substitution in the amino group on luminescent properties of derivatives of 4-aminobenzonitriles, coumarins, and other compounds is associated with a change in the extent of the charge transfer in the excited state 4-~ and in the molecular structure (with a change in hybridization 5 and rotation of the fragments4,6). A rearrangement of the closest environment of the molecule or a change in its structure in the excited state results in the dependence of the efficiency of fluorescence of such systems on the viscosity and polarity of the medium. 4,6 In this work, the effects of the structure of the 4-amino substituent, of the polarity and viscosity of a solvent, as well as the effect of temperature on the fluorescent properties of N-(2,4-dimethylphenyl)imides of 4-amino-1,8-naphthalenedicarboxylic acid were studied to elucidate the reasons for the different fluorescent ExperimentalAbsorption and fluorescence spectra were recorded on a Shimadzu UV-3100 spectrophotometer and an Elyumin 2M spectrofluorimeter, respectively. The kinetics of fluorescence was studied on a nanosecond ORTEC spectrometer by photon counting. The quantum yield of fluorescence (g~) was determined by comparing the areas under the curves of corrected fluorescence spectra of the compound under study with those of a solution of quinine bisulfate in I N H2SO 4 (cp = 0.546). 7 Polym...

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“…24,[38][39][40][41][42] Excited-state proton-transfer reactions have also been widely studied using 7-aminocoumarins. [43][44][45][46][47][48] We have recently published a theoretical study of coumarins 151 and 120. 49 These coumarins have been used in a variety of applications but are small enough to admit treatment with a wide range of electronic structure techniques.…”

Section: Introductionmentioning

confidence: 99%

Time-Dependent Density Functional Theory Investigation of the Ground and Excited States of Coumarins 102, 152, 153, and 343

2002

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We present calculations of various properties of the ground and excited electronic states of coumarins 102, 152, 153, and 343. Using density functional theory (DFT) and time-dependent density functional theory (TDDFT), we examine the excitation energies to the S 1 and S 2 states, the ground and excited-state dipole moments, and the lowest ionization potentials of these coumarins. In the case of C153, we locate two distinct S 0 minima due to differing conformations of the julolidyl ring structure and compare properties for the syn and anti conformers. For C343, we examine the possibility of proton transfers in the ground and S 1 states of the system. We find that (1) DFT tends to overestimate the ground-state dipole moments in these systems, (2) excellent agreement is obtained between TDDFT and experimental vertical excitation energies, (3) TDDFT and CIS yield similar estimates of the dipole moment change between the S 0 and S 1 states, both of which are in the range of previous experimental estimates, (4) in each case, the S 2 state is at least 0.5 eV above the S 1 state for the ground-state geometry, and (5) proton transfer is not likely in the ground state of C343 but is only 0.18 eV higher in energy in the S 1 state. We also compare the DFT/TDDFT results with RHF/CIS, MP2, and INDO S/CI results. We find good agreement between MP2 and experimental ground-state dipole moments and good agreement between INDO S/CI and TDDFT gas-phase excitation energies.

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Planar and twisted intramolecular charge transfer states of the excited proton transfer products of aminocoumarins

Cited by 20 publications

References 9 publications

Photophysical Properties of Coumarin-30 Dye in Aprotic and Protic Solvents of Varying Polarities¶

Photophysical Properties of Coumarin-30 Dye in Aprotic and Protic Solvents of Varying Polarities¶

Radiationless deactivation of excited molecules of 4-aminonaphthalimides

Time-Dependent Density Functional Theory Investigation of the Ground and Excited States of Coumarins 102, 152, 153, and 343

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