Further Study on the Forms of Umbelliferone in Excited State

1978 ◽  
Vol 33 (11) ◽  
pp. 1307-1311 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanislawa Taszner ◽  
Jerzy Kruszewski
Keyword(s):  
Excited State ◽  
Water Content ◽  
Electron Density ◽  
Absorption Spectra ◽  
Water Solution ◽  
Emission Spectra ◽  
Volume Percentage ◽  
Absorption And Emission ◽  
Highly Sensitive ◽  
Wide Range

Absorption and emission spectra of umbelliferone in ethanol-water solution are studied in a wide range of water content. No variations in the absorption spectra were found, whereas the emission spectra proved to be highly sensitive to the volume percentage of water. An interpretation is attempted on the basis of electron density calculations by the SCF PPP CI method for the molecule of umbelliferone and a hypothetical tautomer.

DFT Study of Substituted Effect on Absorption and Emission Spectra of Naphthoquinone Derivatives

2011 ◽  
Vol 233-235 ◽  
pp. 1878-1883 ◽  
Author(s):  
Li Zhi Wang ◽  
Run Zhou Su ◽  
Shuo Qi ◽  
Wei Yu Gong ◽  
Tai Min Cheng
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Visible Region ◽  
Emission Spectra ◽  
Electron Transition ◽  
Functional Theory ◽  
Absorption And Emission ◽  
Absorption And Emission Spectra ◽  
The Density Functional Theory ◽  
Substituted Effect

The density functional theory (DFT) is used to compute the ground-state geometries of naphthoquinone derivatives, and lowest singlet excited-state geometries of them have been investigated by the singles configuration interaction (CIS) method. The absorption and emission spectra are calculated by time-dependent DFT (TDDFT) on the basis of the ground- and excited-state geometries, respectively. Our calculations are in good agreement with the available experimental results. The calculated results show that with the introduction of hydroxyl the red-shift was found in the absorption and emission, and the range of spectra reach the visible region. Furthermore, in the absorptions electron transition type was identified from the point-view of molecular orbitals. Study of the effect of hydroxyl and site on spectra can provide the helpful information on further designing molecular devices.

A study of photocyclization of O-alkyl N-(3-chloro-2-benzo[b]thienocarbonyl)monothiocarbamates

1986 ◽  
Vol 51 (9) ◽  
pp. 2002-2012 ◽  
Author(s):  
Peter Kutschy ◽  
Ján Imrich ◽  
Juraj Bernát ◽  
Pavol Kristian ◽  
Iveta Fedoriková
Keyword(s):  
Excited State ◽  
Complex Formation ◽  
Emission Spectra ◽  
Radical Mechanism ◽  
Singlet Excited State ◽  
Model Compounds ◽  
Reaction Conditions ◽  
Absorption And Emission ◽  
Absorption And Emission Spectra ◽  
High Yields

The O-alkyl N-(3-chloro-2-benzo[b]thienocarbonyl)monothiocarbamates prepared by the reaction of 2-isothiocyanatocarbonyl-3-chlorobenzo[b]thiophene with methanol, ethanol, 1-propanol, and 2-propanol are cyclized on irradiation with light of the wavelength above 300 nm to give high yields (80-90%) of 2-alkoxy-4H-benzo[b]thieno[2,3-e]-1,3-thiazin-4-one derivatives. From the absorption and emission spectra of the starting compounds as well as from a study of model compounds and influence of the reaction conditions it is presumed that the investigated intramolecular photosubstitution of chlorine by sulphur proceeds from the first singlet excited state (π, π*) by a radical mechanism through the phase of radical complex formation.

scholarly journals Initiation and propagation of combustion waves with competitive reactions and water evaporation

2013 ◽  
Vol 469 (2160) ◽  
pp. 20130506 ◽  
Author(s):  
K. J. Hughes ◽  
J. Brindley ◽  
A. C. McIntosh
Keyword(s):  
Water Content ◽  
Chemical Reactions ◽  
Water Solution ◽  
Ambient Pressure ◽  
Computational Modelling ◽  
Water Evaporation ◽  
Endothermic Effect ◽  
Combustion Waves ◽  
Water Fraction ◽  
Wide Range

We use a one-dimensional model to present numerical and analytical results on the propagation of combustion waves, driven by competing exothermic and endothermic chemical reactions in parallel with water evaporation. The research was motivated by the phenomenology of emulsion explosives comprising a mixture of fuel and an ammonium nitrate (AN)–water solution. An extensive programme of computational modelling has covered a range of important physical influences, particularly the water fraction and the ambient pressure, on which the endothermic effect of evaporation is critically dependent. A substantial, and not immediately obvious, influence of the evaporation, through its effect on the temperature, is on the fraction of the AN consumed, respectively, by the competing exo- and endothermic reactions, which are controlled by differing, temperature-sensitive kinetics. Self-sustaining travelling combustion waves are initiated for a wide range of parameter values. They are usually oscillatory, regular for small water content and become highly irregular, sometimes causing extinction for larger water content. The numerics are complemented by a brief theoretical analysis, which throws light on the complex and subtle interplay of the two chemical reactions and the evaporation, expressed in the form of a highly convoluted integral over the whole time and space extent of the process.

scholarly journals Relations between absorption, emission, and excited state chemical potentials from nanocrystal 2D spectra

2021 ◽  
Vol 7 (22) ◽  
pp. eabf4741
Author(s):  
Jisu Ryu ◽  
Samuel D. Park ◽  
Dmitry Baranov ◽  
Iva Rreza ◽  
Jonathan S. Owen ◽  
...  
Keyword(s):  
Excited State ◽  
Single Molecule ◽  
Chemical Potential ◽  
Emission Spectra ◽  
Optical Methods ◽  
Chemical Potential Difference ◽  
Absorption And Emission ◽  
Absorption And Emission Spectra ◽  
Standard Chemical Potential ◽  
Size Dispersion

For quantum-confined nanomaterials, size dispersion causes a static broadening of spectra that has been difficult to measure and invalidates all-optical methods for determining the maximum photovoltage that an excited state can generate. Using femtosecond two-dimensional (2D) spectroscopy to separate size dispersion broadening of absorption and emission spectra allows a test of single-molecule generalized Einstein relations between such spectra for colloidal PbS quantum dots. We show that 2D spectra and these relations determine the thermodynamic standard chemical potential difference between the lowest excited and ground electronic states, which gives the maximum photovoltage. Further, we find that the static line broadening from many slightly different quantum dot structures allows single-molecule generalized Einstein relations to determine the average single-molecule linewidth from Stokes’ frequency shift between ensemble absorption and emission spectra.

UV/Vis Absorption, Emission Spectra and Two-Photo Absorption Cross Sections of 4-Dihydroquinolinone Derivatives

2011 ◽  
Vol 233-235 ◽  
pp. 2748-2754
Author(s):  
Qi Qi ◽  
Yong Quan Ha ◽  
Hai Qing Xu ◽  
Yue Ming Sun
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectra ◽  
Cross Sections ◽  
Density Functional ◽  
Emission Spectra ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Functional Theory ◽  
Model Calculations ◽  
Absorption And Emission

A series of 4-dihydroquinolinone derivatives were fully optimized by density functional theory (DFT), Hartree-Fock (HF) and Configuration Interaction Singlet (CIS) approaches. Absorption spectra, emission spectra and two-photon absorption cross sections were calculated by using time-dependent density functional theory and few-state model. Calculations were performed in the presence of solvent by using Conductor polarizable continuum model (CPCM). The molecular geometries, absorption spectra, emission spectra were in good agreement well with those experiment values. The absorption and emission peak red-shifted as a result of the extension of the conjugated structures. The introduction of heteroatoms such as F, Cl and Br gave rise to intramolecular transfer and the blueshift of the absorption and the emission spectra. The introduction of O or S atoms in two sides of molecules propelled the redshift of the absorption and emission maximum.

Excited state dynamics of organic semi-conducting materials

2015 ◽  
Vol 177 ◽  
pp. 111-119 ◽  
Author(s):  
Kenneth P. Ghiggino ◽  
Andrew J. Tilley ◽  
Benjamin Robotham ◽  
Jonathan M. White
Keyword(s):  
Excited State ◽  
Conjugated Polymer ◽  
Variable Temperature ◽  
Emission Spectra ◽  
Time Resolved ◽  
Absorption And Emission ◽  
X Ray ◽  
X Ray Crystallography ◽  
Conducting Materials ◽  
Absorption And Emission Spectroscopy

Time-resolved absorption and emission spectroscopy has been applied to investigate the dynamics of excited state processes in oligomer models for semi-conducting organic materials. Following the photo-excitation of a pentamer oligomer that is a model for the conjugated polymer MEH-PPV, an ultrafast component of a few picoseconds is observed for the decay of the initially formed transient species. Variable temperature absorption and emission spectra combined with X-ray crystallography and calculations support the assignment of this rapid relaxation process to an excited state conformational rearrangement from non-planar to more planar molecular configurations. The implications of the results for the overall photophysics of conjugated polymers are considered.

scholarly journals Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

2017 ◽  
Vol 13 ◽  
pp. 203-212 ◽  
Author(s):  
Jonas Becher ◽  
Daria V Berdnikova ◽  
Darinka Dzubiel ◽  
Heiko Ihmels ◽  
Phil M Pithan
Keyword(s):  
Optical Properties ◽  
Excited State ◽  
Ground State ◽  
Emission Spectra ◽  
Weak Acid ◽  
Deprotonated Form ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Ph Values ◽  
Acidic Conditions

3-Hydroxynaphtho[1,2-b]quinolizinium was synthesized by cyclodehydration route and its optical properties in different media were investigated. The absorption and emission spectra of this compound depend on the pH of the solution. Thus, at higher pH values the deprotonation yields a merocyanine-type dye that exhibits significantly red-shifted absorption bands and causes a dual emisson, i.e., a combination of emission bands of the hydroxyquinolizinium and its deprotonated form. Whereas this compound is a weak acid in the ground state (pK a = 7.9), it has a strongly increased acidity in the excited state (pK a * = 0.4). As a result, the blue-shifted fluorescence of the hydroxyquinolizinium becomes dominant only under strongly acidic conditions. In addition, it is shown that 3-hydroxynaphtho[1,2-b]quinolizinium binds to cucurbit[7]uril (CB[7]) with moderate affinity (K b = 1.8 × 104 M−1, pH 5) and that the pK a and pK a * values of this ligand increase by about two to three orders of magnitude, respectively, when bound to CB[7].

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