Issei Harada

Spectroscopic studies on doped polyacetylene and β-carotene

In order to elucidate the structural details of doped polyacetylene (a highly conducting organic polymer), the optical absorption, Raman, and infrared spectra of not only trans‐(CH)x doped with iodine, AsF5, and SO3 but also β‐carotene doped with iodine and SO3 were studied. The infrared spectra of two kinds of isotopically substituted polyacetylenes (CD)x and (13CH)x doped with iodine were also observed. Analysis of the experimental results shows that upon doping each of the four vibrational branches (ν1–ν4) in the 1600–900 cm−1 region of a polyene chain splits into two groups, namely, the higher frequency group and the lower frequency one. The former group consists of the ’’gerade’’ vibrations of polyene parts which are not directly attacked by dopants but are perturbed along the chain, whereas the latter is made up of the ’’ungerade’’ vibrations of the positively charged polyene part with the doped site at its center. The Raman bands in the higher‐frequency group of ν1 (mainly the C=C stretching mode) ...

Normal Vibrations and Intermolecular Forces of Crystalline Benzene and Naphthalene

The GF matrix method was applied to the analysis of band splittings and lattice vibrations of crystalline benzene. The far‐infrared spectrum of crystalline naphthalene was measured in the region from 300 to 50 cm−1 and three infrared‐active lattice vibrations were observed. A normal‐coordinate treatment of the lattice vibrations of naphthalene was performed. Intermolecular force constants of nonbonded hydrogen—hydrogen pairs and hydrogen—carbon pairs were obtained.

Far‐Infrared Spectra of Crystalline Benzene at 138°K and Intermolecular Forces

Far‐infrared spectra of crystalline benzene have been measured at low temperatures. The three bands assigned to the translational lattice vibrations have been found. The frequencies of these lattice vibrations, those of the Raman‐active lattice vibrations and the frequency splittings of the infrared bands at 138°K have been consistently explained from the hydrogen—hydrogen and hydrogen—carbon interactions.The values obtained for these atom—atom interactions are correlated with the values of other intramolecular and intermolecular force constants and with the energy of internal rotation for n‐butane.

Far‐Infrared Spectra of Cyanuric Acid, Uracil, and Diketopiperazine

The far‐infrared spectra of cyanuric acid, uracil, and diketopiperazine were measured in the region from 300 to 90 cm—1. The GF matrix method was applied to the analysis of lattice vibrations. The translational lattice vibrations were assigned to some of the observed bands. The force constants of hydrogen bonds were obtained.

Tables of Molecular Vibrational Frequencies. Part 10

Fundamental vibrational frequencies of 94 molecular forms of 23 polyatomic chain molecules of halogenoalkanes and halogenoalkyl ethers consisting of the CH3, CH2, O, F, Cl, Br, and I groups are given as an extension of tables of molecular vibrational frequencies published in the NSRDS‐NBS publication series and in this journal. On preparing the tables in this part, an approach, similar to that in Part 9 but different from that in earlier parts, based on the calculations of normal vibration frequencies was adopted. A set of force constants which explains all the frequencies of small molecules for which the assignments had been established was obtained and then the frequencies of larger molecules were calculated and compared with the frequencies observed in the infrared and Raman spectra. The tables provide a convenient source of information for those who require vibrational energy levels and related properties in molecular spectroscopy, thermodynamics, analytical chemistry, and other fields of physics and ...

Far-infrared spectra and barriers to internal rotation of isopropyl alcohol and alkyl mercaptans

Far-infrared spectra of isopropyl alcohol, ethyl mercaptan, isopropyl mercaptan, tert-butyl mercaptan, and their deuterated analogs have been examined. The observed torsional transitions are interpreted with a potential function of the form V = 12ΣkVk(1 − cos kα). The obtained energy differences are in good agreement with those determined from calorimetric data. The coupling of torsional vibration with other low frequency vibrations is discussed.

Matrix-isolation infrared and ultraviolet spectroscopic studies of less stable conformers of 1,3,5-hexatriene

Abstract The infrared spectra of the 3- trans and 3- cis isomers of 1,3,5-hexatriene in low-temperature Ar matrices deposited from a high-temperature nozzle or deposited under irradiation of the Hg 253.7 nm light show a number of new bands. Correspondingly, the ultraviolet spectra of the 3- trans isomer observed under similar experimental conditions show a new absorption at 276 nm. Most of these new infrared bands and the new ultraviolet absorption are attributable to less stable isomers which have the planar s- cis conformation [or gauche conformation(s) close to the planar s- cis ] about either one or both of the two CC bonds.

Far-i.r. reflection spectrum and normal vibrations of red mercuric iodide crystal

Abstract The vibrational frequencies of the transverse and longitudinal modes of red mercuric iodide, HgI 2 , were obtained from the polarized far-i.r. reflection spectrum. The values of effective ionic charges of I and Hg atoms were determined to be −0.37 5 e and 0.75 e , respectively, on the basis of the TO—LO splittings. The normal coordinate analysis near the center of Brillouin zone was performed for the point charge model of the crystal and a good agreement between the observed and calculated frequencies was obtained.

Raman spectrum of toxin B in relation to structure and toxicity

There are two types of neurotoxic proteins in the venoms of Elapidae and Hydrophiidae snakes. They are the short-chain neurotoxins (type I toxins) consisting of 60-62 amino acid residues with four disulfide bridges and the long-chain neurotoxins (type II toxins) consisting of 7 1-74 amino acid residues with five disulfide bridges [l] . Laticauda semifasciata III (Is III) is the only one exceptional neurotoxin so far identified that does not belong to either type [2,3]. The shortchain and long-chain toxins have similar neurotoxicity [4]. However, the differences distinguished between them in the effects of chemical modifications on the toxicity [5,6] suggest some difference in the role of the essential amino acids for neurotoxicity. In the preceding paper, Harada et al. reported the Raman spectra of the short-chain neurotoxins, erabutoxins a and b (Ea and Eb), the denatured toxins, and the weakly neurotoxic Is III, and discussed on the structure-toxicity relationships [7]. Toxin B is a long-chain neurotoxin from the venom of the Indian cobra, Naja naja, and 71 amino acid sequence and the position of the five disulfide bridges have been determined [8], In the present paper, the Raman spectrum of toxin B is reported and the structure-toxicity relationships are discussed in comparison with the former results on the short-chain toxins [7,9].

Raman spectra of some snake venom components

The Raman spectra of aqueous solutions of cobrotoxin, erabutoxin b (short-chain neurotoxins), alpha-bungarotoxin (a long-chain neurotoxin), cardiotoxin, cytotoxin I (cardiotoxins), 6-carboxyl-modified cobrotoxin and cobrotoxin treated with 5 M guanidine-HCl (denatured neurotoxins) were investigated. The main-chain structure of the toxins was found to consist predominantly of beta-pleated sheets and random-coils. The relative amounts of the beta-conformations were estimated to be in order of: cardiotoxins approximately short-chain neurotoxins greater than long-chain neurotoxins greater than Laticauda semifasciata III (exceptionally weak neurotoxin). Most of the disulfide-bridges of every toxin take the gauche-gauche structure about the CC-SS-CC linkage. However, the number of gauche-gauche structures is not the same among the neurotoxins. Tyr-25 of cobrotoxin is found to form a strong hydrogen bond similar to that of other short-chain neurotoxins investigated earlier.