Spectroscopic studies on some chromones

1970 ◽  
Vol 48 (24) ◽  
pp. 3928-3936 ◽  
Author(s):  
James B. Gallivan
Keyword(s):  
Absorption Spectra ◽  
Room Temperature ◽  
Broad Band ◽  
Spectroscopic Studies ◽  
Luminescence Spectra ◽  
Multiple Bonds ◽  
Polar Solvents ◽  
Singlet States ◽  
Orbital Character ◽  
Phosphorescence Spectra

Absorption and luminescence spectra were measured for chromone, 4-chromanone, and four photoproducts formed by the addition of extramolecular multiple bonds to photo-excited chromone. Absorption spectra in polar and non-polar solvents at room temperature revealed a low lying n → π* singlet transition in all of these systems. The cycloaddition products and 4-chromanone showed a weak fluorescence in polar solvents which was not observed in non-polar solvents, suggesting a solvent reordering, or at least increased mixing of low lying n,π* and π,π* singlet states. No fluorescence could be detected from chromone in either type of solvent. At 77 °K in polar solvents, all of these systems displayed a concentration independent, intense phosphorescence of intermediate lifetime (25 to 200 ms). The lifetime data, combined with the vibrational analyses of the phosphorescence spectra, phosphorescence polarization results, and oxygen induced singlet–triplet absorption spectra support the concept of a lowest energy triplet state of mixed orbital character. More detailed studies on chromone demonstrated a concentration dependent phosphorescence in non-polar solvents, with the "normal" chromone phosphorescence dominant below 10−4 M. At higher concentrations a lower energy, broad band phosphorescence was observed, which in spite of physical aggregation in the ground state, can be ascribed to a chromone exciplex.

SPECTROSCOPIC STUDIES OF KETO–ENOL EQUILIBRIA: PART 2. ANOMALOUS ULTRAVIOLET ABSORPTION SPECTRA OF SATURATED 1,2-DICYANO ESTERS

1962 ◽  
Vol 40 (12) ◽  
pp. 2272-2277 ◽  
Author(s):  
T. R. Kasturi ◽  
B. N. Mylari ◽  
A. Balasubramanian ◽  
C. N. R. Rao
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Spectroscopic Studies ◽  
Anomalous Behavior ◽  
Enol Form ◽  
Ultraviolet Absorption ◽  
Polar Solvents ◽  
Solvent Dependence

1,2-Dicyano esters show an absorption band around 245 mμ in alcoholic solutions which is not found in non-polar and other polar solvents. This anomalous behavior has been found to be due to the unusual solvent dependence of the equilibrium between the keto and enol forms. The intensity of the absorption band in alcoholic solutions decreases with increase in concentration of the 1,2-dicyano ester, indicating association of the enol form. The keto–enol equilibrium is also found to be sensitive to the substituent R of the alcohol ROH.

Steady-state and Time-resolved Spectroscopic Studies of Benzanilides

1999 ◽  
Vol 54 (8-9) ◽  
pp. 495-502 ◽  
Author(s):  
Józef Heldt ◽  
Janina R. Heldt ◽  
Jerzy Kamiński
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Steady State ◽  
Proton Transfer ◽  
Room Temperature ◽  
Spectroscopic Studies ◽  
Fluorescence Band ◽  
Polar Solvents ◽  
Time Resolved ◽  
Decay Times

Steady-state and time-resolved spectroscopic studies of benzanilide (I) and jV-methylbenzanilide (II)were performed at 298 and 77 K in various solvents. The results indicate that benzanilide fluorescencein non-polar solvents at room temperature involves three independent modes of emission: F1 (LE) normalfluorescence from the initially excited state S1 (LE) with λmax = 320 nm, F2´(PT) fluorescence from the proton transfer tautomer with λmax = 468 nm, F2″CT) fluorescence from the species where intramolecular charge transfer appears, with λmax = 510 nm. At 77 K in MCH a new fluorescence band, Fag, appears at λmax=415 nm instead of the F2(PT) and F2″CT) fluorescence. This new emission originates from benzanilide dipolar aggregates or cis-imidol dimers. The decay times of these emission modes aredifferent.N-methylbenzanilide, dissolved in nonpopular and weakly polar solvents at room temperature and at77 K, shows only two fluorescence modes, i.e., the normal and the charge-transfer emissions at 320 nmand 520 nm, respectively. The fluorescence is deactivated with two decay times, 30 ps and 2.05 ns, inMCH solution.

Photophysical properties of pyridinium salts derived from purine bases

1990 ◽  
Vol 68 (12) ◽  
pp. 2164-2170 ◽  
Author(s):  
Bohdan Skalski ◽  
Stefan Paszyc ◽  
Ryszard W. Adamiak ◽  
Ronald P. Steer ◽  
Ronald E. Verrall
Keyword(s):  
Absorption Spectra ◽  
Fluorescence Spectra ◽  
Room Temperature ◽  
Transient Absorption ◽  
Photophysical Properties ◽  
Pyridinium Salts ◽  
Excited Triplet ◽  
Transient Absorption Spectra ◽  
Counter Ions ◽  
Phosphorescence Spectra

The absorption spectra, fluorescence spectra, fluorescence lifetimes, fluorescence quenching, phosphorescence spectra, phosphorescence lifetimes, and picosecond transient absorption spectra of several purinyl-pyridinium salts have been measured in several solvents at room temperature and in ethanol glasses at 77 K. It is concluded that the previously observed photochemical transformation of N-[9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)purin-6-yl]pyridinium chloride 1 into the highly fluorescent tri-O-acetylluminarosine 6 occurs via an excited triplet state. It is also shown that intersystem crossing in purinyl-pyridinium salts is induced by an intermolecular charge-transfer interaction with the counter ions. Keywords: purinyl-pyridinium salts, fluorescence, phosphorescence.

Use of Halocarbon Oils as a Matrix for Transmission Spectroscopic Studies of Solid Inorganic Materials in the Near-Infrared and Visible Regions

1993 ◽  
Vol 47 (5) ◽  
pp. 556-559
Author(s):  
N. S. Guyot-Sionnest ◽  
V. A. Maroni
Keyword(s):  
Light Scattering ◽  
Absorption Spectra ◽  
Room Temperature ◽  
Near Infrared ◽  
Spectroscopic Studies ◽  
Inorganic Materials ◽  
Potassium Sulfate ◽  
Silicotungstic Acid ◽  
Inorganic Substances

Halocarbon oils are shown to be a useful matrix for transmission spectroscopic studies of solid inorganic materials in the near-infrared and visible regions. Absorption spectra of these oils are flat and featureless between 5000 and 32,000 cm−1. The halocarbon oils are inert to virtually all types of inorganic substances at room temperature. Light scattering appeared to be reduced for the more viscous of two halocarbon oils investigated. Examples of the application of the halocarbon oil mull technique are given for three inorganic substances: chromium(III) potassium sulfate dodecahydrate, nickel(II) hydroxide, and silicotungstic acid.

Fractionation of Plasminogen by Starch Gel Electrophoresis

1964 ◽  
Vol 12 (01) ◽  
pp. 126-136 ◽  
Author(s):  
Karl H. Slotta ◽  
J. D Gonzalez
Keyword(s):  
Gel Electrophoresis ◽  
Room Temperature ◽  
Broad Band ◽  
Caproic Acid ◽  
Starch Gel Electrophoresis ◽  
Full Activity ◽  
Veronal Buffer ◽  
Starch Gel ◽  
Alkaline Range

SummaryWhen urea or ε-amino caproic acid were used as solublizing agents for plasminogen in electrophoretic experiments, only one broad band of the proenzyme was obtained on acetate cellulose, in starch block, and in acrylamide gel. In starch gel electrophoresis, however, both forms of plasminogen – the native or euglobulin and Kline’s or Pseudoglobulin plasminogen – separated into six bands. These migrated toward the cathode at room temperature in borate or veronal buffer in the alkaline range and showed full activity in fibrinagar-streptokinase plates.

Luminescence Properties of Europium-Doped Yttrium Oxides Derived from Their Dodecylsulfate-Templated Mesostructure and Nanotube Forms

2003 ◽  
Vol 775 ◽  
Author(s):  
Tsuyoshi Kijima ◽  
Kenichi Iwanaga ◽  
Tomomi Hamasuna ◽  
Shinji Mohri ◽  
Mitsunori Yada ◽  
...  
Keyword(s):  
Room Temperature ◽  
Broad Band ◽  
Concentration Quenching ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Bulk Materials ◽  
Main Band ◽  
Homogeneous Precipitation Method ◽  
Order Of Magnitude ◽  
Weak Luminescence

AbstractEuropium-doped hexagonal-mesostructured and nanotubular yttrium oxides templated by dodecylsulfate species as well as surfactant free bulk oxides were synthesized by the homogeneous precipitation method. All the as grown nanostructured or bulk materials with amorphous or poorly crystalline frameworks showed weak luminescence bands at room temperature. On calcination at 1000°C these materials were converted into highly crystalline yttrium oxides, resulting in a total increase in intensity of all the bands by one order of magnitude. In the hexagonal-mesostructured system, the main band due to the 5D0-7F2 transition for the calcined phases showed a sharp but asymmetrical multiplet splitting indicating multiple Eu sites. Concentration quenching was found at a Eu content of 3 mol% or above for these phases. In contrast, the main emission for the calcined solids in the nanotubular system occurred as poorly resolved broad band and the intensity of the main band at higher Eu content was significantly enhanced compared with those for the other two systems.

Infrared spectra of N-acetyl-L-α-amino-acid N'-methylamides with aliphatic side chains in non-polar solvents

1981 ◽  
Vol 46 (3) ◽  
pp. 772-780 ◽  
Author(s):  
Jorga Smolíková ◽  
Jan Pospíšek ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Conformational Changes ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Side Chains ◽  
Polar Solvents

Infrared spectra of the L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured. Amides I-IV are not self associated in tetrachlormethane in the concentration 2 . 10-5 mol l-1 at room temperature and in tetrachloroethylene in the concentration 1.5 . 10-4 mol l-1 at temperatures above 65° C. True conformational changes are observable only with the least flexible amide IV which exists at room temperature in a C5 conformation. This conformational type is also highly populated in the valine derivative III, but is less important in the alanine and leucine derivatives I and II in which the intramolecularly bonded C7 and the distorted hydrogen-nonbonded conformations contribute seriously.

NIR and Upconversion Luminescence Properties of Nd3+ Doped in Gd2O3-CaO-SiO2-B2O3 Glass System

2014 ◽  
Vol 548-549 ◽  
pp. 124-128 ◽  
Author(s):  
S. Insiripong ◽  
S. Kaewjeang ◽  
U. Maghanemi ◽  
H.J. Kim ◽  
N. Chanthima ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Upconversion Luminescence ◽  
Emission Spectra ◽  
Concentration Quenching ◽  
Luminescence Spectra ◽  
Optical Absorption Spectra ◽  
Glass Matrices ◽  
Nir Luminescence

In this work, properties of Nd3+ in Gd2O3-CaO-SiO2-B2O3 glass systems with composition 25Gd2O3-10CaO-10SiO2-(55-x)B2O3-xNd2O3 where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol% were investigated. The optical absorption spectra show peaks at 4F3/2 (877 nm) , 4F5/2+2H9/2 (802 nm), 4F7/2+4S3/2 (743 nm), 4F9/2 (682 nm), 2H11/2 (627 nm), 2G7/2 +4G5/2 (582 nm), 4G7/2 +2K13/2 (527 nm), 4G11/2 (481 nm), 2P1/2 (427 nm) and 2L15/2 + 4D1/2 + 1I11/2+ 4D5/2+ 4D3/2 (355 nm) reflecting the Nd3+ ions in glass matrices. The densities were increased with increasing of Nd2O3 concentration. This indicates the increase of the molecular weight by the replacement of B2O3 with a heavier Nd2O3 oxide in the glass. The upconversion luminescence spectra show bands at 393 nm for all Nd2O3 concentration and the strongest intensity from 2.5 % mol of Nd2O3 was obtained. For NIR luminescence, the intensity of Nd3+ emission spectra increases with increasing concentrations of Nd3+ up to 1.5 mol% and beyond 1.5 mol% the concentration quenching is observed.

Electrical and Optical Properties of Si+ and P+ Implanted InP:Fe

1990 ◽  
Vol 201 ◽  
Author(s):  
Honglie Shen ◽  
Genqing Yang ◽  
Zuyao Zhou ◽  
Guanqun Xia ◽  
Shichang Zou
Keyword(s):  
Optical Properties ◽  
Silicon Nitride ◽  
Temperature Dependence ◽  
Optimal Condition ◽  
Room Temperature ◽  
Broad Band ◽  
Photoluminescence Spectra ◽  
Electrical And Optical Properties ◽  
Spectrum Measurement ◽  
Single Implant

AbstractDual implantations of Si+ and P+ into InP:Fe were performed both at 200°C and room temperature. Si+ ions were implanted by 150keV with doses ranging from 5×1013 /cm2 to 1×1015 /cm2, while P+ ions were implanted by 110keV. 160keV and 180keV with doses ranging from 1×l013 /cm2 to 1×1015 /cm2. Hall measurements and photoluminescence spectra were used to characterize the silicon nitride encapsulated annealed samples. It was found that enhanced activation can be obtained by Si+ and P+ dual implantations. The optimal condition for dual implantations is that the atomic distribution of implanted P overlaps that of implanted si with the same implant dose. For a dose of 5×l014 /cm2, the highest activation for dual implants is 70% while the activation for single implant is 40% after annealing at 750°C for 15 minutes. PL spectrum measurement was carried out at temperatures from 11K to 100K. A broad band at about 1.26eV was found in Si+ implanted samples, of which the intensity increased with increasing of the Si dose and decreased with increasing of the co-implant P+ dose. The temperature dependence of the broad band showed that it is a complex (Vp-Sip) related band. All these results indicate that silicon is an amphoteric species in InP.

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