Perturbation of the fuchsone chromophore by 3,5-methyl substitution. Sterically crowded exocyclic double bond

1981 ◽  
Vol 46 (10) ◽  
pp. 2540-2556 ◽  
Author(s):  
Bohumír Koutek ◽  
Lubomír Musil ◽  
Jiří Velek ◽  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Bathochromic Shift ◽  
Exocyclic Double Bond ◽  
Wavelength Band ◽  
Methyl Substitution ◽  
Steric Crowding ◽  
Hypochromic Effect

Several 3,5-methyl substituted fuchsones have been synthesized and characterized by means of UV and NMR spectroscopy as well as dipole moment measurements. Two basic types of behaviour of the longest wavelength band have been found for these derivatives in comparison to 2,6-substituted analogues i.e. hypochromic effect and bathochromic shift. These effects can be attributed to a steric crowding of the C(4)-C(7) double bonds. The role of the steric interactions in the ground state and in the excited state is discussed.

scholarly journals Solvatochromic Study of Supramolecular Amphiphile Based on Calix[4]arene Connected to a Fluorescent Benzofurazan Moiety at Lower Rim: Evaluation of Ground and Excited State Dipole Moments-=SUP=-*-=/SUP=-

2020 ◽  
Vol 128 (12) ◽  
pp. 1864
Author(s):  
S. Joshi
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Fluorescence Spectra ◽  
Dipole Moments ◽  
Photophysical Properties ◽  
Bathochromic Shift ◽  
Fluorescence Emission ◽  
Wide Range ◽  
Excited State Dipole Moment

Photophysical properties of a supramolecular amphiphile of calix[4]arene having benzofurazan moiety at the lower rim, L has been studied. Electronic absorption and fluorescence spectra of L have been recorded in wide range of solvents of different polarities and data were used to study solvatochromic properties. The ground state and the excited state dipole moment of L were estimated from the Bakhshiev's and Bilot-Kawaski's equations. High value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of molecule. Also, fluorescence emission peak undergoes a bathochromic shift with increase in the polarity of the solvent, confirming π-> π* transition. Scanning electron microscopy reveals that the aggregation of L is increased on going from the polar to non polar solvents. Keywords: solvatochromism, benzofurazan, dipole moment, quantum yield, absorption, fluoresence.

A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases

2017 ◽  
Vol 474 (16) ◽  
pp. 2713-2731 ◽  
Author(s):  
Athinoula L. Petrou ◽  
Athina Terzidaki
Keyword(s):  
Oxidative Stress ◽  
Excited State ◽  
Singlet Oxygen ◽  
Ground State ◽  
Meta Analysis ◽  
Common Mechanism ◽  
High Electron ◽  
A Value ◽  
First Excited State

From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG≠ values that vary in the range 92.8–127 kJ mol−1 at 310 K. A value of ∼10–30 kJ mol−1 is the activation energy for the diffusion of reactants, depending on the reaction and the medium. The energy needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen) is equal to 92 kJ mol−1. So, the ΔG≠ is equal to the energy needed for the excitation of ground state oxygen to the singlet oxygen (1Δg first excited) state. The similarity of the ΔG≠ values is an indication that a common mechanism in the above disorders may be taking place. We attribute this common mechanism to the (same) role of the oxidative stress and specifically of singlet oxygen, (1Δg), to the above-mentioned processes: excitation of ground state oxygen to the singlet oxygen, 1Δg, state (92 kJ mol−1), and reaction of the empty π* orbital with high electron density regions of biomolecules (∼10–30 kJ mol−1 for their diffusion). The ΔG≠ for cases of heat-induced cell killing (cancer) lie also in the above range at 310 K. The present paper is a review and meta-analysis of literature data referring to neurodegenerative and other disorders.

scholarly journals The Role of Polarizabilities in the Fluorescence Behaviour of 4-cyano-N,N-dimethylaniline

1981 ◽  
Vol 36 (8) ◽  
pp. 868-875 ◽  
Author(s):  
Wolfram Baumann
Keyword(s):  
Dipole Moment ◽  
Electric Field ◽  
External Electric Field ◽  
Ground State ◽  
Permanent Dipole Moment ◽  
Reaction Field

Abstract The effect of an external electric field on the absorption and the double fluorescence of 4-cyano-N,N-dimethylaniline can be understood, taking into account reaction field induced polarizability effects. If a TICT state conformation emits the a-fiuorescence in dioxane, the permanent dipole moment in this state is only slightly larger than in the equilibrium ground state.

Electroabsorption spectra of push–pull porphyrins in solution and in solid films

2015 ◽  
Vol 19 (01-03) ◽  
pp. 527-534
Author(s):  
Kamlesh Awasthi ◽  
Hung-Yu Hsu ◽  
Hung-Chu Chiang ◽  
Chi-Lun Mai ◽  
Chen-Yu Yeh ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Charge Transfer ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Ground State ◽  
Benzene Solution ◽  
Solid Films ◽  
The One ◽  
Interfacial Charge

Polarized electroabsorption (E-A) spectra of highly efficient porphyrin sensitizers (YD2 and YD2-oC8) have been measured in benzene solution. Polarized E-A spectra of these push–pull porphyrins embedded in poly(methyl methacrylate) films or sensitized on TiO 2 films are also observed. Based on the analysis of the E-A spectra, the magnitude of the electric dipole moment both in the ground state and in the lowest excited state have been evaluated in solution and in solid films. The electric dipole moment in the excited state of these compounds is very large on TiO 2 films, suggesting the interfacial charge transfer on TiO 2 surface following photoexcitation of porphyrin dyes. The electric dipole moment in the excited state evaluated from the E-A spectra is very different from the one evaluated from the electrophotoluminescence spectra on TiO 2, suggesting that the strong local field of TiO 2 films is applied to the fluorescing dyes attached to TiO 2 films.

Molecular and structural characterization of New Red and Erythrosine by fluorescence polarization spectroscopy

2017 ◽  
Vol 31 (19-21) ◽  
pp. 1740062
Author(s):  
Chun Zhu ◽  
Jia-Meng Du ◽  
Jin-Chen Zhao ◽  
Tuo Zhu ◽  
Guo-Qing Chen
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Dipole Moments ◽  
Linear Structure ◽  
Polarization Spectroscopy ◽  
Angle Shift ◽  
Ground State Structures ◽  
Average Angle

The fundamental and the fluorescence anisotropies of New Red and Erythrosine were measured. The intersection angles between the absorption and the emission dipole moments for New Red and Erythrosine are 4.44[Formula: see text] and 23.26[Formula: see text], respectively. The average angle shift of the emission dipole moment of New Red is 3.91[Formula: see text] during the lifetime of the excited state. This indicates that it has a bifurcated linear structure with weak rotational capacity. The average angle shift of the emission dipole moment of Erythrosine is 9.25[Formula: see text], indicating that it has a partial planar structure and is easier to rotate. The spatial ground state structures were simulated with Gaussian 09.

scholarly journals Ground and Excited State Dipole Moment of 2,5-Dihydroxybenzoic Acid from Solvatochromic Shifts

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Meena Adhikari ◽  
Sanjay pant
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ionic Species ◽  
Dihydroxybenzoic Acid ◽  
Fluorescence Techniques ◽  
Solvatochromic Shifts ◽  
Spectral Behaviour ◽  
Excited State Dipole Moment ◽  
Polarity Of Solvents

In present work we explore the role of solvents on the 2, 5-dihydroxybenzoic acid by using fluorescence techniques. It was found that DHBA shows spectral behaviour depending on polarity of solvents. DHBA shows generally three components at 405-415nm, 430-450nm, and 450-470nm. The effects of zwitterion as well as the interplay ionic species are involved to explain the observed results

Investigations of a Metastable Dependence on the Ionization of Sputtered Species in Neon Glow Discharges

1991 ◽  
Vol 45 (10) ◽  
pp. 1656-1664 ◽  
Author(s):  
D. Serxner ◽  
R. L. Smith ◽  
K. R. Hess
Keyword(s):  
Excited State ◽  
Glow Discharge ◽  
Ground State ◽  
Copper Ion ◽  
Penning Ionization ◽  
Glow Discharges ◽  
Discharge Gas ◽  
Discharge Pressure ◽  
Ion Emission

Optical investigations of a low-pressure (0.3–4.0 Torr), low-current (1–4 mA), coaxial geometry glow discharge operating with neon as the fill gas are described. Studies were designed to experimentally illustrate the role of neon metastable atoms in the population of selected excited-state ion levels of copper atoms sputtered from a brass cathode. Methane was employed as a quenching agent to reduce the neon metastable population, and ion emission signals from a variety of copper ion transitions showed a decrease in intensity corresponding to the introduction of methane to the plasma. In addition, with variations in discharge pressure, a correlation between the number of neon metastables and the strength of the ion emission signals was observed. These results provide evidence that Penning ionization is an important mechanism for the ionization of sputtered atoms in neon glow discharges, similar to the results obtained for an argon system. Finally, a brief comparison of the neon and argon systems was made which showed the neon discharge gas to be more efficient at populating the monitored copper ion levels. This is most likely due to the higher energy of the neon metastables, which permits the direct population of these ion levels from the copper ground state.

scholarly journals Solvent effect on the absorption and emission spectra of carbon dots: evaluation of ground and excited state dipole moment

BMC Chemistry ◽  
2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Parisa Mohammad-Jafarieh ◽  
Abolfazl Akbarzadeh ◽  
Rahman Salamat-Ahangari ◽  
Mohammad Pourhassan-Moghaddam ◽  
Kazem Jamshidi-Ghaleh
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Carbon Dots ◽  
Dipole Moments ◽  
Emission Spectra ◽  
Aprotic Solvents ◽  
One Step ◽  
The Difference ◽  
Excited State Dipole Moment

Abstract Background Carbon dots (C-dots) are photoluminescent nanoparticles with less than 10 nm in size. Today, many studies are performed to exploit the photoluminescence (PL) property of carbon dots, and our focus in this study is to estimate the dipole moment of carbon dots. For reaching our aims, C-dots were synthesized and dissolved in the different solvents. Results Carbon dots with intense photoluminescence properties have been synthesized by a one-step hydrothermal method from a carbon bio-source. In this research, we report on the effect of aprotic solvents on absorption and fluorescence spectra and dipole moments of C-dots dispersed in a range of many aprotic solvents with various polarity and dielectric constant at room temperature. The change in the value of dipole moment was estimated by using the Stokes shifts. The difference between the dipole moment of the excited state and the ground state was shown using an extended form of Lippert equations by Kawski and co-workers. Conclusions The values found for μg = 1.077 D, and μe = 3.157 D, as well as the change in the dipole moments. The results showed that the dipole moment of the excited state is more than the ground state, indicating a high density and redistribution of electrons in the excited state. Finally, the quantum yield of C-dots in the eclectic aprotic solvents was communicated and discussed.

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