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Nemkovich, N. A.; Baumann, Wolfram; Kruchenok, Yu. V.; Reis, Heribert; Рубинов, А. Н.

doi:10.1023/a:1022598430510

Cited by 25 publications

(23 citation statements)

References 20 publications

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“…4,5 Although the MP2 value for the C120 dipole moment is similar to the experimental value in dioxane, the measured dipole moment is expected to be enhanced in solution, as noted above. Thus, on the basis of the experimental solution phase dipole moment, the gas-phase value would be expected to be significantly smaller than our calculated values.…”

Section: Comparison Of Excited-state Dipole Moments For C151 Withsupporting

confidence: 64%

“…3 The energy of the lowest singlet state relative to the ground state for 7-aminocoumarins is remarkably sensitive to the polarity of their environment, indicating a substantial dipole moment change between the ground and excited state. [4][5][6][7][8] This solvatochromic behavior has allowed a number of groups to use ultrafast spectroscopic techniques to unravel the dynamics of solvation in polar solvents by examining coumarin fluorescence dynamics. 2,[9][10][11][12][13][14][15][16] Following this seminal work, researchers have begun to apply coumarin fluorescence dynamics to probe local environment fluctuations in a wide variety of chemical environments.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

2002

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We present calculations of various properties of the ground and excited states of Coumarins 151 and 120. These and related coumarins are important in investigating ultrafast solvation processes in liquids and complex solutions as well as being important acceptors in model electron-transfer systems. We calculate the following: (1) the electronic excitation energies to several low-lying singlet states, (2) ground and excitedstate dipole moments, (3) solvation effects on excitation energies, and (4) the properties of single Coumarin 151-water complexes. We test our Time-Dependent Density Functional Theory (TDDFT) calculations against CASSCF, CASPT2 (both single and multistate versions), CIS, and ZINDO. Using TDDFT, we find excellent agreement with experimental S 1 r S 0 excitation energies. On the basis of these results, we address several outstanding questions for these systems and find: (1) that TICT-formation is unlikely upon photexcitation for gas-phase C151, (2) a greater tendency toward a planar amine group for the S 1 state than for the ground state, (3) significant differences between our gas-phase ground-state dipole moment and the experimental value, and (4) TDDFT results for water-Coumarin 151 complexes are in good agreement with the experimental results of Topp and co-workers.

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Section: Comparison Of Excited-state Dipole Moments For C151 Withsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

2002

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“…However, on photoexcitation, the electron from amino group is transferred further more to the carbonyl group, resulting in a much larger ICT character in the excited state. The enhancement of the charge transfer character on photoexcitation is supported by the fact that the difference in dipole moment between the ground and the excited state for these molecules is very large [18][19][20][21]. It is now believed that the emission of these coumarin dyes is mainly originated from their planar ICT state.…”

Section: Effect On the Ict To Tict Conversionmentioning

confidence: 98%

“…The protic solvent molecules can act as donors in type-I and type-II interactions, whereas it acts as an acceptor in type-III H-bonding. It is well known that the excited state of coumarin dyes is of intramolecular charge transfer (ICT) character [18][19][20][21]. Thus, on photoexcitation, an electron from the amine site is partially transferred to the carbonyl site.…”

Section: Effect On Photophysical Propertiesmentioning

confidence: 99%

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Effect of H‐Bonding on the Photophysical Behaviour of Coumarin Dyes

Nath

Kumbhakar

Pal

2010

Hydrogen Bonding and Transfer in the Excited State

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The Lippert-Mataga [1, 2] expression is the most generalized equation used to describe the solvent-dependent spectral shifts of many chromophoric molecules. The Lippert-Mataga equation considers mainly two characteristic factors of the solvents, namely the refractive index (n) and the static dielectric constant («). According to the Lippert-Mataga representation, a chromophore should show bathochromic shifts in the absorption and emission spectra and a linear increase in the Stokes shift with increasing solvent polarity parameter, Df (Df ¼ [(« À 1)/(2« þ 1) À (n 2 À 1)/(2n 2 þ 1)]). This general solvent effect predicted by the Lippert-Mataga equation is expected to be independent of the chemical properties of the chromophore and the solvent used.Besides its extensive use, the Lippert-Mataga equation fails to predict the spectral properties of several chromophores in different solvent environments [3][4][5][6][7][8]. This failure is mainly due to the presence of specific interactions of the chromophores with their surrounding solvent molecules. These specific interactions can arise owing to different mechanisms such as preferential solvation [9-11], charge transfer interaction [12], hydrogen bonding interaction [13][14][15], etc. The changes in spectral characteristics experienced by a chromophore owing to its specific interaction with the surrounding solvent can sometimes be much more prominent than those expected from the general solvent effect as predicted by the Lippert-Mataga equation. For example, N-phenyl-2-aminonaphthalene shows a structured emission spectrum in a non-polar solvent such as cyclohexane. However, the structures in the emission spectrum disappear, and the emission maxima undergo a large shift on the addition of just $0.2% of ethanol in the cyclohexane solution of the dye [16]. Further, it is seen that the spectrum of N-phenyl-2-aminonaphthalene in 3% ethanolic solution is only marginally different from that observed in the neat ethanol solution. Such a small amount of ethanol in

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Fluorescent properties and spontaneous Raman spectroscopy of new ketocyanine probes in organic solvents

2006

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The position of their electronic spectra depends strongly on the polarity of the solvent. We measured the dipole moments of the dyes in the equilibrium ground state and the Franck-Condon excited state. In mixtures of neutral nonpolar toluene with aprotic polar dimethylsulfoxide, we observe inhomogeneous broadening of the electronic spectra for the indicated compounds, due to fluctuations in solution of the intermolecular interaction energy. The time-resolved characteristics of fluorescence obtained suggest formation of an intermolecular hydrogen bond between the dye and the surrounding medium in a toluene-ethanol mixture. We measured the Raman spectra of CPET and CPMR in different organic solvents. The most intense lines in the 1582-1591 cm -1 region can be assigned to stretching of the phenyl rings of the molecules; the lines in the 831-842 cm -1 region can be assigned to a cyclopentanone ring mode; the lines at 1186-1195 cm -1 can be assigned to stretching of the =C-C-bond of the phenyl ring and rocking of the H atoms of the phenyl ring. We have observed that the position and width of the lines for the stretching vibrations of the ketocyanines depend substantially on the polarity of the surrounding medium.The studied dyes can be used as probes for studying different biological systems by site-selective laser spectroscopy and Raman spectroscopy. The fact that these two methods can be used simultaneously for diagnostics of biosystems is an important advantage of ketocyanine dyes compared with other known probes.Key words: fluorescence spectroscopy, spontaneous Raman scattering, ketocyanine dyes, inhomogeneous broadening of spectra, hydrogen bond.Introduction. Fluorescent probes have been increasingly intensively used for more and more diverse purposes in physics, chemistry, biology, and medicine, since such probes make it possible to solve a number of complicated and important problems [1]. The fluorescent probes themselves have also been perfected, and new spectral effects are used for analysis of the microcharacteristics of the environment. Fluorescent probes have been previously synthesized containing distinct electron density donor and acceptors, most often amino and carbonyl groups. Many such dipolar compounds (naphthalenes, phthalimides, anthracenes, etc.) have found broad application in analysis of molecular structure relaxation in simple solutions and biological macromolecules [2][3][4][5]. The indicated compounds are characterized by a significant change in the charge distribution in the excited electronic state, occurring on a femtosecond to nanosecond time scale. From the position of the fluorescence spectrum, its Stokes shift, the lifetime of the excited state, the emission anisotropy kinetics, and other characteristics, we can obtain information about the polarity, viscosity, dynamics of nearest-neighbor molecules and their segments in the environment of the probe, the presence, nature, and size of the charge on the ions.

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Cited by 25 publications

References 20 publications

Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

Effect of H‐Bonding on the Photophysical Behaviour of Coumarin Dyes

Fluorescent properties and spontaneous Raman spectroscopy of new ketocyanine probes in organic solvents

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