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intramolecular sense. I n addition, it is of interest to note that the plot passes, when extrapolated to Pa = 0, through an intercept which corresponds to the Aijh value obtained for MA homopolymer in benzene solution (17.7 cm-l). Another finding is that the band width tends to increase with elevating temperature.
Proton Ejection Accompanying Light-Induced Electron Transfer in the Chlorophyll-Quinone System
Sir: Linschitz and Rennert' have shown that chlorophyll undergoes a reversible photobleaching in the presence of benzoquinone. Tollin and his co-workers2,8 demonstrated by esr measurements that the benzosemiquinone ion radical is formed in these light-activated single electron transfer reactions. The present paper presents evidence to show that these reactions are accompanied by the ejection of a proton. Studies performed in the aprotic solvent, dimethylformamide, demonstrate that chlorophyll is the proton source. The apparatus used to measure the proton ejection has recently been de~cribed.~A Corning 52-61 filter, which is opaque to all wavelengths below 600 mp, was used. Chlorophylls a and b were prepared by the method of Zscheile and C ~ m a r . p-Benzoquinone ~ was purified by sublimation, p-chloranil was recrystallized from acetone, dimethylformamide was distilled under vacuum from calcium hydride, and the methanol used was the spectrophotometric grade (Fisher). Benzoquinone in alcohol slowly forms a species which absorbs at 355 mp. Since this species is not formed in Figure 2. Plots of half band width against dyad and triad either dimethylformamide or with chloranil, it is assequence probability, Pz and Pa,respectively. sumed to have little or no effect on the final results For details, see text. presented. Figure 1 shows the apparent proton ejection from both the chlorophyll a- and b-quinone systems in I n connection with the above observations, it should methanol. Solutions were deaerated by flushing with be noted that the half band width of the C=O band nitrogen pretreated with a chromous chloride solution. found for dimethyl fumarate is clearly smaller than The dashed line illustrates results obtained after the that for dimethyl maleate when they are determined air-free solutions were exposed to air for at least 0.5 hr. in benzene solution. The difference in the steric conThese are typical results obtained in a series of light figuration of carbonyl groups appears to be reflected and dark intervals. Irradiation of the chlorophylls in the band width. Further detailed observations alone in methanol in the presence of air gives irreversible and a pertinent interpretation of this phenomenon alkaline reactions which are probably due to the basicity will be given in due course. of the products from the photooxidation of the chlorophylls. Air-free systems of chlorophyll b give no pH Acknowledgments. The authors thank Professor response but a slight alkaline reaction is obtained with Toru Takenaka, Institute for Chemical Research, and chlorophyll a. This may be due to residual oxygen Professor Hirotsugd Matsuda, Research Institute for present in the system. Studies of the chlorophyll bFundamental Physics, Kyoto University, for their p-chloranil system in methanol showed that more prohelpful discussions during the course of this work. tons are ejected than observed with benzoquinone. The RESEARCH LABORATORY FUMIO KAMIYAMA apparent proton ejection activity is in the range of SEKISUICHEMICAL COMPANY MISHIMA-GUN, OSAKA-FU, JAPAN
HISAYUKI MATSUDA
(1) H. Linschits and J. Rennert, Nature, 169, 193 (1952). (2) G. Tollin and G. Green, Bwchim. Bwphys. Acta, 60, 524 (1962). INSTITUTE FOR CHEMICAL RESEARCH HIROSHIINAGAKI (3) G. Tollin, K. K. Chatterjee, and G. Green, Photochem. Photobwl., KYOTOUNIVERSITY 4, 592 (1965). TAKATSUKI, OSAKA-FU, JAPAN (4) K. P. Quinlan and E. Fujimori, ibid., 6 , 665 (1967). (5) F. P. Zscheile and C. L. Comar, Botan. Guz., 102, 463 (1941). RECEIVED AUGUST3, 1967
The Journal of Phyeical Chemietry
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oi
Y
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tt
7.825 t L
Z 7.815
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7.410
4
-
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7.405
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CHLOROPHYLL A
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CHLOROPHYLL B
9
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Figure 1. Ejection of protons from chlorophyll-quinone systems in methanol. Right ordinate represents results obtained in air. The upward arrows represent light on; downward, light off. Top figure: chlorophyll a, 3.7 X M ; with quinone, 0.03 M . Bottom figure: chlorophyll b, 2.3 X l o + M ; with quinone, 0.03 M .
10-6 M . Proton ejection has also been observed in the present study with the quinone systems of pheophytin, bacteriochlorophyll, and hematoporphyrin. These studies will be reported later. A possible explanation of the observations is presented in the following simplified scheme CHLH h', CHLH*
(1)'
CHLH* --f CHLH'
(2)
The results presented in the present paper are not only important in gaining insight into the mechanism of the light-activated electron transfer of chlorophyll systems but also lend support to the current hypothesisll which relates the dissociation of some form of chlorophyll to the chemiosmotic12theory of photophosphorylation in photosynthesis. (6) R. Livingston, Quart. Rev. (London), 14, 174 (1960). (7) E. Fujimori and M. Tavla, Photochem. Photobwl., 5, 877 (1966). (8) R. Livingston and K. E. Owens, J . Am. Chem. soc., 7 8 , 3301 (1956). (9) G.0.Schenck, Nuturwissenschuften, 40, 205 (1953). (10) C. 0.Ritchie and G. H. Megerle, J. Am. Chem. soc., 89, 1447 (1967). (11) H.T. Witt, G. Doring, B. Rumberg, P. SchmidbMende, U. Siggel, and H. H. Stiehl in "Energy Conversion by the Photosynthetic Apparatus," Publication No. 19,Biology Department, Brookhaven National Laboratory, Upton, N. Y., 1967, p 161. (12) P. Mitchell, Nature, 191, 144 (1961).
PHOTOCHEMISTRY SECTION ENERGETICS BRANCH SPACEPHYSICS LABORATORY L. G. HANSCOM FIELD BEDFORD, MASSACHUSETTS 01730
KENNETH P. QUINLAN EIJI FUJIMORI
RECEIVED AUGUST14, 1967
The Intracrystalline Rearrangement of Constitutive Water in Hydrogen Zeolite Y
CHLH'(CHLH*)
+ Q +CHL. + Q . - + H +
(3)
where CHLH* and CHLH' are the excited singlet and triplet states of chlorophyll. The interaction of quinone with either of the excited states of chlorophyll as in eq 3 is well documented.6 Figure 1 also shows that the proton ejection activities are of the same order of magnitude whether air is present or not. This is surprising since both quinone and oxygen are known to compete for the excited states of chlorophyll.6 The role of the chlorophyll-oxygen in these light-activated reactions is uncertain. This aspect of the problem is currently under investigation. The ejected proton in the present system can originate from two possible sources: (A) reaction 3 and (B) the solvent, where CHLH. + is a cation of a weak base and Q . - is an anion of a strong acid. Studies performed in the aprotic solvent, dimethylformamide, show that a proton is ejected as in reaction 3. In this study a calomel electrode, containing a saturated solution of KC1 in dimethylformamide, was used. The theoretical behavior of this type of an electrode system has recently been shown by Ritchie and Megerle.1°
Sir: The loss of constitutive or chemical water from hydrogen zeolite Y occurs at temperatures above 500" at torr.'P2 We have found that this reaction occurs in several minutes, using an inert purge gas a t 650 to 750" and approximately 760 torr. The product has poor thermal stability. Hydrogen zeolite Y heated 2-4 hr at 700-800" in an inert static atmosphere, where the chemical water remains in the environs of the hydrogen zeolite, yields a substance of unusually high thermal stability. This material remains crystalline on heating to 1000", whereas sodium and hydrogen zeolite Y both lose their zeolite crystal structure at temperatures below 950". McDaniel and Maher report the synthesis of a zeolite Y of similar high ~ t a b i l i t y . ~They do not define the critical requirements for its formation nor do they account for its composition. (1) H. A. Szymanski, D. N. Stamires, and G. R. Lynch, J. O p t . SOC. Am., 50, 1323 (1960).
(2) J. B. Uytterhoeven, L. G. Christner, and W. K . Hall, J . Phys. Chem., 69, 2117 (1965). (3) C. V. McDaniel and P. K. Maher, preprint of paper presented a t Molecular Sieve Conference, London, April 1967.
Volume 71, Number 12 November 1967
