โ Scribed by Noboru Mataga; Hiroshi Yao; Tadashi Okada
No coin nor oath required. For personal study only.
relation to the photoinduced charge separation in the special pair ,of photosynthetic reaction center, solvation induced intramolecular electron transfer in the excited state of composite system with identical halves have been investigated with.picosecond spectroscopy in the case of l,t-dianthrylethanes. The energy gap dependences of charge separation and charge recombination in these systems are demonstrated and compared with those of hybrid dim& model of metal porphyrins, porphyrin-quinone systems and various aromatic donoracceptor systems. The significance of these results in the understanding vf efficient charge separetion in biological reaction center is discussed. In the SP. two bacteriochlorophyll chromophores interact weakly and the first CS process seems to take place at SP, leading from a pair of symmetric neutral chromophores to a cation-anion pair. 3 Therefore, the first step of.CS in the photoexcited RC is a symmetry breaking process due to ET in the SP with identical halves. which might be induced by Some environmental effect in proteins on which the chromophores are held. In this respect, it will be an important problem to examine the photoinduced CS in medel systems with identical halves. However, contrary to the case of the intramolecular exciplex systems where donor and acceptor are combined with spacers or directly by single bond and photoinduced intramolecular CS takes place easily. 4 clear-cut examples of the systems with identical halves combined by spacer or directly by single bond are quite scarce. N. MATAGA et al. due to the photoinduced intramolecular CS.5 This system has a special conformation where two anthracene planes are perpendicular to each other due to the steric repulsion. This special structure keeps the electronic interaction between the two chromophores moderately weak, which prevents the formation of symmetrical excimer-like state overcoming the driving force of symmetry breaking by solvation. However, recent picosecond laser photolysis and Spectrograde n-hexane, .ethylacetate, acetone-and acetonitrile were,' used without purification. Sample solutions of ca; 10m4 M for the'measnrement were deoxygenated by freeze-pump-thaw.cycTes or by flushihg with nitrogen gas.
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