Yoshiya Kanda

The triplet-singlet emission spectra of phenanthrene and related compounds in EPA and in petroleum ether at 90° K

Abstract Phosphorescence spectra of phenanthrene, 5:6-benzoquinoline and 7:8-benzoquinoline have been studied in EPA and in petroleum ether at 90°K. The spectra have similar structures and their vibrational analyses have been discussed. For this purpose Raman, infra-red and ultra-violet spectra of these compounds have also been studied.

Singlet—triplet absorption spectra of several carbonyl compounds

Singlet—triplet absorption spectra of benzaldehyde, acetophenone and benzophenone have been studied in solution and the absorption curves have been presented. For comparison, the spectrum of benzoquinone has also been studied. Phosphorescence spectra of these compounds have been studied for confirmation of the triplet state. Vibrational analyses made by SIDMAN for the crystal spectrum of benzoquinone and by ANNO and SADO for the vapour spectrum have been criticized. The S′—T separation, i.e. the separation between the lowest excited singlet state and the lowest triplet state, is seen to decrease with increasing ratio, fS,T| fS,S′, namely, an f-number of a single—triplet spectrum over an f-number of a singlet—singlet spectrum.

Study on the molecular geometry of phosphorescent pyrazine by optical detection of zero-field magnetic resonance and T ← S excitation spectroscopy

The phosphorescent state of pyrazine has been studied with the T → S emission and T ← S excitation methods in combination with microwave techniques in the systems of pyrazine-h 4 in pyrazine-d 4, pyrazine-h 4 and -d 4 in p-dioxane, p-xylene, and benzene, and pyrazine-h 4 x-trap. The three out-of-plane hydrogen bending vibrations of v 10a , v 5 and v 17a are found to be active in the Tx sublevel emission of the isotopic mixed crystal. By modifying the force constants used by Scully, the frequencies of the out-of-plane vibrations were reexamined and the result was compared with the observed frequencies. The microwave-induced changes in the phosphorescence intensity were used as a measure of the relative populations in the triplet sublevels, when the system was excited with light having the wavelength corresponding to a particular vibronic band of the T ← S absorption. In this way, the vibrational structure of the absorption spectra was successfully analysed. The overtone bands of v 10a and v 5 were observed...

The phosphorescence spectrum of biphenyl at 90°K

Abstract The phosphorescence spectra of biphenyl were studied in EPA, petroleum ether, cyclohexane and carbon tetrachloride at 90°K. In the last three solutions the spectra showed fine structure and the vibrational analyses have been discussed.

The triplet-singlet emission spectra of benzene in carbon tetrachloride and dioxane matrices at 90°K

Abstract The phosphorescence spectrum of benzene has been studied in carbon tetrachloride and dioxane matrices at 90°K, and vibrational analyses are discussed. The intensity of the 0,0-band of the spectrum in carbon tetrachloride is fairly strong and no b 2 g vibration is found, while an e 2 u vibration of 404 cm −1 is obtained. It is concluded that the molecular shape is probably of C 2 v symmetry because of deformation of the molecule due to lattice forces of the matrix. On the other hand, the spectrum in dioxane is similar to, but sharper than, that in EPA. An e 1 g vibration (849 cm −1 ) is found in the spectrum. The occurrence of this vibration is also ascribed to the deformation of benzene in dioxane matrix. The reduced symmetry is probably D 2 h .

n, π∗ electronic states of p-benzoquinone; The T-S emission spectrum in mixed crystals

Abstract In order to scrutinize the lowest triplet n, π ∗ state of p-benzoquinone, we have observed its T-S emission and absorption spectra in a crystal, in an isotopically mixed crystal, and in p-dihalobenzene crystals at various temperatures between 1.45 and 77°K. Important evidence was found that leads to a conclusion that the phosphorescence process may have been an orbitally and spin forbidden 3B1g-1Ag transition. Although it is still multiplicity forbidden, the phosphorescence has been allowed vibronically through perturbation of four b1u fundamentals (except a CH stretching mode) and two b3u fundamentals of the out-of-plane CH and ring distortion modes. The contribution of the b1u CO stretching mode to the vibronic perturbation was greatest and that of the b1u ring bending mode was second. A detailed analysis of the T-S absorption of the p-benzoquinone crystal and the T-S emission of p-benzoquinone-h4 in an isotopically mixed crystal predicted that the 3B1g level is the lowest triplet, being located at 18 624 cm−1, which is lower about 320 cm−1 than the 3Au level. Comparison of the f-value and the observed lifetime (6.4 × 10−4 sec in an isotopically mixed crystal) of the T-S transition indicated there should be anomalous nonradiative processes in the triplet state of p-benzoquinone. For comparison, the phosphorescence spectrum of toluquinone has also been observed in p-dihalobenzenes.

On the origin of the Ham bands in the spectrum of benzene in fluid solution

The spectrum of benzene has been studied in various fluid solutions at various temperatures in the ultra-violet region and at room temperature in the infra-red, and the relations between the spectral behaviour and the intensity of the Ham bands have been examined. No positive evidence for assigning the bands to the 3E1u−1A1g transition has been found, and it is believed that the bands belong to the lowest 1B2u−1A1g transition. No evidence has been found that the appearance of the bands is due to chemical bond forces or charge-transfer bond forces between benzene and solvent molecules. It has been concluded that the intensity of the Ham bands has a close relation to the intensity of the anomalous infra-red bands of benzene 1177(e2g) and 850(e1g) cm−1 vibrations, and that the origin of the Ham bands is due to dispersion forces between benzene and solvent molecules. This conclusion is valid only if the solution is fluid.

The triplet-singlet emission spectra of toluene, o-, m- and p-xylenes and mesitylene in cyclohexane matrices at 90°K

Abstract Phosphorescence spectra of toluene, o-, m- and p-xylenes and mesitylene have been studied in cyclohexane matrices at 90°K. All the spectra appeared sharper than those in EPA, and, especially, the spectra of toluene and o-xylene showed finelyresolved structures. Vibrational analyses are discussed.

Fluorescence spectra of organic compounds in solution—I On the positions of the 0,0-bands of the fluorescence spectra

Abstract Fluorescence spectra of various condensed ring compounds have been studied in various solvents at room temperature. The positions and intensities of the 0,0-bands of the fluorescence spectra were seen to depend on the concentration of the solutions and, especially, the 0,0-bands for anthracene, phenanthrene and two isomers of benzoquinoline agreed well with those of the absorption spectra when sample solutions were highly diluted. On the other hand, no agreement was found for the 0,0-bands of the fluorescence and absorption spectra of long molecules, such as trans -stilbcno, trans , trans -diphenyloctatetraene, biphenyl and p -terphenyl, even at a very low concentration.

The absorption spectrum of benzene in carbon tetrachloride at 77°K

Abstract The absorption spectrum of benzene has been studied in carbon tetrachloride solutions of various concentrations at 77°K and in 10 per cent solution at various temperatures from 30°C to 77°K. The so-called crystalline spectrum appeared strongly at low temperature and its occurrence was ascribed to the deformation of benzene due to crystal forces of the carbon tetrachloride matrix.