Masao Koizumi

Photochemical Reactions between Methylene Blue and Tri-, Di- and Monomethylamine. II

The effects of various factors upon the photobleaching of methylene blue in the evacuated aqueous solution by means of mono-, di- and trimethylamine, were studied experimentally, and the result were analyzed by the rate formula presented in the preceding paper on the basis of the following scheme;(Remark: Graphics omitted.)The results obtained can be summarized as follows: k1 is written in the form; k1=k10[OH−][TA]I0. k2 and k3 are also proportional to [OH−] and they both increase monotonously with the light intensity and amine concentration.In addition, the photobleaching was examined in the presence of Fe+++ and Cu−−. It was found that in the case of Fe+++, k3 is much decreased while k1 and k2 are scarcely affected. The absorption spectra of the intermediate were observed more prominently than when no Fe+++ was present. From these results it was concluded that Fe+++ stabilizes the intermediate. In case of Cu++ some induction period was observed during which Cu precipitates, and its duration was found to...

Dependence of the Stability of Exciplex upon the Solvent Polarity

It has been found that the stability of exciplex consisting of naphthylethylether and dimethylphthalate, increases with the solvent polarity in sligthly polar solvents. This is in sharp contrast to Mataga et al.s result on the exciplex of pyrene with dimethylaniline of which the stability decreases with the solvent polarity. It has been suggested that as a general tendency, weak exciplexes may display the first feature while stronger ones the second.

Reversible Energy Transfer between Eosine and Anthracene

In 1965, Parker et al. discovered that the triplet energy transfer and mixed T—T annihilation can occur between some dyes and aromatic hydrocarbons1. But any quantitative investigations upon these processes have not yet been made since then. By means of a flash technique involving emission measurement2, we have carried out such studies on the ethanol solutions of eosine and anthracene ; these compounds have almost the same triplet levels. This short communication deals with a reversible triplet energy transfer occurring between eosine and anthracene in ethanol, leaving the problem of mixed T—T annihilation to the next paper. The elementary reactions to be taken up in connection with the triplet energy transfer, are the ones involved in scheme [A], and as the result of the present investigation all the rate constants for them have now been decided. In particular, the existence of the approximate equilibrium (2, 4), ET + A ^ E AAT has been demonstrated in a simple way.

Mixed T—T Annihilation between Eosine and Anthracene

ET h°±E*. (10) Processes (7) and (8) are the mixed T—T annihilation, the former giving rise to the delayed fluorescence of eosine while the latter, that of anthracene. (9) is the T—T annihilation process pertaining only to anthracene. Process (10) brings forth the i£-type delayed fluorescence of eosine. The rate constants of these four processes were evaluated by combining the delayed fluorescence data for eosine and anthracene with those of the decay of the T—T absorption which were obtained under the same experimental conditions. It has been established by the present investigation that process (7) occurs with a high rate constant while process (8) does not practically occur. If process (8) were to occur, the intensity of the delayed fluores-

Determination of the S*–T transition probability of acridine dyes by the method of sensitized delayed fluorescence

ΦST Values for proflavine, acriflavine, and Acridine Orange in ethanol solutions have been determined by means of the sensitized delayed fluorescence method.