Yoshie Tanizaki

Dichroism analysis: Part I. Vibronic transitions of some naphthols☆

Abstract Descriptions are given for the empirical facts concerning the dichroic spectra where the stretched PVA (polyvinyl alcohol) sheet is used. The principle and the process of the qualitative and quantitative analysis of the transition directions are discussed. Absorption and dichroic spectra of several naphthols in the nonstretched and stretched PVA sheets, respectively, were determined in the region above 220 mμ and were discussed from the usual spectroscopic and the dichroic points of view. It is found that the intense 1 B b band appearing at about 230 mμ has the smallest orientation angle in every case. The polarization of the shorter side band ( 1 L a ) of the weak absorptions in the region above 260 mμ is always perpendicular to that of 1 B b , while the polarization of the longer side band ( 1 L b ) is parallel or perpendicular to 1 B b according to whether an OH group occupies the α or β position of naphthalene, respectively. When two OH groups occupy two symmetric β positions with respect to the long ( x ) or short ( y ) axis of naphthalene, the 1 L b band is polarized in the same direction as 1 B b . Both the 1 L a and 1 L b polarizations are not always restricted to the pure y and x axes.

Assignment of the π—π* Transitions of some Tropone Derivatives by Dichroism Analysis

The absorption spectra of tropolone (abbreviated to HT) and 2-aminotropone (AT) were observed in various solutions. In alkaline solution, HT becomes tropolone anion (HT-) by dissociation of hydrogen of the phenolic hydroxyl group. In acid solution, AT is protonated at the amino group, (AT+). The dichroic spectra of the above compounds in the stretched polyvinylalcohol (PVA) sheet were observed and the direction of the transition moment of each band was determined by the dichroism analysis. Two oxygen atoms of HTare not equivalent. All the above compounds possess four — * transitions above 220 μ. Calculations about the electronic transitions of tropone, HT and AT were made by means of the semi-empirical LCAO ASMO SCF CI method. It was shown that the transition direction obtained by the dichroism analysis can provide an important information to determine the parameters for the semi-empirical calculations.

Polarized Absorption Spectra of 1,10-Phenanthroline and Phenanthrene in Stretched PVA Sheets

The divided spectra of 1,10-phenanthroline and phenanthrene were obtained, and the polarization direction of each band in the near ultraviolet region was determined. By comparison of the results of the divided spectra and those of the Pariser-Parr-Pople calculations including a variable ß approximation, assignment of the electronic bands of these compounds was established. It has been found that 1,10-phenanthroline has the a;-polarized bands (polarized perpendicularly to the (72-axis) at 30.7 kK, 34.5 kK, 37.3 kK and 43.7 kK, and the 2/-polarized bands (parallel to the C2-axis) at 29.4 kK, 39.2 kK and 42.7 kK. The a;-polarized band at 30.7 kK might be assigned to be due to an

Localized and Delocalized Electronic Transitions in Diphenylacetylene, Stilbene and Diphenylbutadiene

Dichroic spectra of diphenylacetylene, stilbene and diphenylbutadiene were measured in stretched polyvinylalcohol sheets, and semiempirical SCF-CI calculations for these compounds were carried out. The first bands of these compounds appeared above 300 μ are considered to be delocalized bands and the relatively weak second bands at around 230 μ to be localized ones. The polarization of the first band of each compound is along a line connecting two centers of the ben-

Assignment of electronic spectrum of perylene

Abstract By means of the dichroism analysis using the stretched PVA film, the electronic spectrum at room temperature of perylene below 46 kcm −1 was divided into two component spectra polarizing to the long ( x ) and short ( y ) axes of the molecule. The first band system (22–29 kcm −1 ) is polarized to x axis and is constituted of four vibrational bands starting at 22.6 kcm −1 . The second band system (36–43 kcm −1 ) is polarized to y and also has four vibrational bands starting at 37.8 kcm −1 . The third band system (above 42 kcm −1 ) consists of x - and y -polarized bands with comparable intensity. The x component of the third band has a well defined 0-0 peak at 43.5 kcm −1 . The experimentally determined energies of 0-0 bands and the calculated transition energies showed a linear relation to each other. Making use of the linear relation, all the weak absorptions in the divided spectra could be assigned. The assignments proposed so far were critically discussed and compared with present assignment.

Polarized absorption and ESR spectra of acridine C-radical

Abstract The polarized absorption and ESR spectra of the acridine C-radical have been measured at room temperature, the radical was produced at 77 K by γ-ray irradiation of a stretched polyvinyl alcohol film saturated with acridine. The dichroism of the absorption spectrum has been well explained by the results of MO calculations for the acridine C-radical.

Polarized absorption spectra of aromatic radicals in stretched polymer films. Part 6.—Radical ions of some aromatic molecules

By use of the stretched polymer-film technique combined with γ-irradiation, polarized absorption spectra of the radical anions and cations of perylene, pyrene, naphthalene, phenanthrene and biphenyl have been studied. The polarized absorption spectra have been resolved into components with transition moments polarized parallel to and perpendicular to the molecular long axis. The pairing relation has been examined between the electronic transitions of the radical anion and the corresponding cation.

Dichroism Analysis. Experimental Assignment of Electronic Spectra of some Bridged Derivatives of Biphenyl

The diohroic spectra of diprotonated 2,7-diaminofluorene, phenanthrene, phenanthrenequinone, fluorenone and carbazole in the stretched PVA sheet were determined and discussed. The dichroism analysis was carried out on a criterion that possible transitions are along the long or the short axis of molecule because of the symmetry property, Civ A correlation diagram of correspondence of the transition directions of all compounds used was established.

Dichroism analysis: the allowed and forbidden n-π∗ transition bands of 1,3-diazaazulene

Abstract The dichroism analysis of 1,3-diazaazulene has been carried out. There are five π-π ∗ and two n -π ∗ absorption bands above 220 nm. Concerning the π-π ∗ bands, the polarizations, transition energies and relative intensities are in agreement with the results of an MO calculation. An n -π ∗ band which is hidden in the first absorption band is polarized along the long axis and is symmetry forbidden. Another n -π ∗ band buried in the second band is polarized in a direction normal to the molecular plane and is symmetry allowed. The MO schemes concerning the n -π ∗ transitions are discussed in comparison with those of 2-ethoxy-1,3-diazaazulenes.

Assignment of electronic bands of some benzidines by dichroism

Abstract The dichroic spectra in the stretched polyvinyl alcohol (PVA) sheet of benzidine, 3,3′-dichlorobenzidine, o -tolidine, and dianisidine were analyzed in the region above 220 mμ. The first electronic band appearing at around 310 mμ in the neutral state corresponds to the first band of biphenyl (ca. 250 mμ), and its transition moment is directed along the long axis of the molecule. At the shorter wavelengths of the first band a weak absorption (ca. 270 mμ) is hidden, the transition moment of which is directed along the short axis of the molecule and is attributed to the 1 L b transition of benzene. But in the case of dianisidine, the corresponding band appears at about 290 mμ as a shoulder. The intense band below 220 mμ, of which only the tail was observable, has the same polarization as that of the hidden band and is assigned to the 1 B b transition of benzene. All samples in the acid state have the first band with the longitudinal polarization at about 250 mμ and the second band with the latitudinal below 220 mμ. Besides, dianisidine in the acid state has another band at 292 mμ with the polarization slanting against the molecular axis. This may have originated from the 1 L b transition of benzene which has become intensified and has changed its polarization due to the perturbation of the methoxy groups.