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J. Phys. Chem. 1996, 100, 1638-1642
Excited-State Dynamics of Ground-State Complexes between Haloanthraquinones and 2,5-Dimethylhexa-2,4-diene, and Quenching of Triplet Haloanthraquinones by 2,5-Dimethylhexa-2,4-diene Toshihiro Nakayama, Tetsuya Hamana, Sadao Miki, and Kumao Hamanoue* Department of Chemistry, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606, Japan ReceiVed: June 19, 1995; In Final Form: October 16, 1995X
Picosecond laser photolysis of haloanthraquinones (XAQ; the bromo and bromochloro compounds) in toluene containing 1 M 2,5-dimethylhexa-2,4-diene (DMHD) gives rise to the appearance of absorption bands due to not only the second and lowest excited triplet states of XAQ but also a transient ionic species (an excited singlet charge-transfer complex or a singlet ion pair) generated by direct excitation of a ground-state XAQDMHD complex. In DMHD, similar results are also obtained for R-bromoanthraquinones (the 1-bromo, 1,5-dibromo, and 1,8-dibromo compounds), whereas only the absorption band due to the transient ionic species is observed for the 2-bromo, 1-bromo-5-chloro, and 1-bromo-8-chloro compounds. Although this transient ionic species decomposes into the semiquinone radical of XAQ and 2,5-dimethylhexa-2,4-dien-1-yl radical, nanosecond laser photolysis indicates that a second-order reaction between these two radicals yields the corresponding haloanthrahydroquinone and a biradical (probably 2,5-dimethyl-1,3,5-hexatriene). From measurements of the molar extinction coefficients (at the 347.2-nm excitation wavelength in toluene) and the small fractions (0.03-0.13 in DMHD) of all free XAQ, the results obtained by picosecond laser photolysis of R-bromoanthraquinones in DMHD are ascribed to simultaneous excitation of free XAQ and the groundstate XAQ-DMHD complex; i.e., its molar extinction coefficient at 347.2 nm is very small owing to the significant reduction of a charge-transfer interaction (between DMHD and the carbonyl group of XAQ) by the bromine atom. The quenching of the lowest excited triplet states of all XAQ by DMHD is also interpreted in terms of their charge-transfer interaction.
Introduction The molecular association yielding a transient ionic species (such as an exciplex, an excited charge-transfer complex, an ion pair, or radical ions) is one of the most important primary processes in a number of photochemical reactions. On the basis of observation of the formation of a ground-state complex between 1,8-dichloroanthraquinone (1C,8C-AQ) and 2,5-dimethylhexa-2,4-diene (DMHD), we also studied the photoinduced intracomplex electron transfer from DMHD to 1C,8CAQ and the results obtained by picosecond laser photolysis were as follows.1 (1) Upon 347.2-nm excitation, not only the triplettriplet absorption bands due to the second (T2) and lowest (T1) excited triplet states (generated by excitation of 1C,8C-AQ) but also an absorption band due to an excited singlet charge-transfer complex or a singlet ion pair (generated by excitation of the ground-state complex between 1C,8C-AQ and DMHD) was observed in DMHD(1 M)/toluene, while only the latter absorption band was observed in DMHD. (2) Upon 435- or 527-nm excitation in both DMHD(1 M)/toluene and DMHD, however, only the absorption band due to the excited singlet chargetransfer complex (or the singlet ion pair) was observed. All the absorption bands stated above disappeared within a delay time of 1 ns and a similar result was obtained for anthraquinone (AQ).2 We thus thought that such an excited singlet charge-transfer complex (or a singlet ion pair) as observed for 1C,8C-AQ or AQ was not generated for 1,8dibromoanthraquinone, because its 347.2-nm excitation in both DMHD(1 M)/toluene and DMHD revealed the existence of only the T1 state of 1,8-dibromoanthraquinone even at 1-ns delay. For haloanthraquinones (XAQ) such as the 1-bromo (1B-AQ), 2-bromo (2B-AQ), 1,5-dibromo (1B,5B-AQ), 1,8-dibromo X
Abstract published in AdVance ACS Abstracts, January 1, 1996.
0022-3654/96/20100-1638$12.00/0
(1B,8B-AQ), 1-bromo-5-chloro (1B,5C-AQ), and 1-bromo-8chloro (1B,8C-AQ) compounds, however, we have recently observed the formation of a ground-state XAQ-DMHD complex. As an extension of our study on the formation and the decay of transient ionic molecular complexes,1-6 therefore, the present paper deals with the excited-state dynamics of the ground-state XAQ-DMHD complex studied by 347.2-nm picosecond-nanosecond laser photolysis of XAQ in DMHD(1 M)/toluene and DMHD. Our final conclusions are as follows: (1) Excitation of the ground-state XAQ-DMHD complex really generates an excited singlet charge-transfer complex (or a singlet ion pair) similar to that observed for 1C,8C-AQ1 or AQ;2 (2) for 1B,8B-AQ, no observation of an transient absorption responsible for the excited singlet charge-transfer complex (or the singlet ion pair) in the previous study can be attributed to a failure to search the transient absorption at a proper delay time shorter than 1 ns, because this absorption disappears completely at 1-ns delay whereas the triplet-triplet absorption due to the T1 state of 1B,8B-AQ still exists owing to a relatively slow triplet quenching by DMHD. Experimental Section The details of the methods for synthesis and/or purification of XAQ, AQ, and 1C,8C-AQ were given previously.7,8 DMHD (Aldrich) was distilled immediately before use but scintillationgrade toluene (Dojin) was used without further purification. The concentration of XAQ was kept to be 1.2 mM and the sample solution for picosecond laser photolysis was not degassed, while that for nanosecond laser photolysis was degassed by several freeze-pump-thaw cycles. All experiments were performed at room temperature and the ground-state absorption spectra of DMHD in toluene and XAQ in DMHD(0-3 M)/toluene were recorded by a Hitachi 200-20 © 1996 American Chemical Society
Excited-State Dynamics of XAQ-DMHD Complexes
Figure 1. Ground-state absorption spectra of 3 M DMHD in toluene (- - -) and those of 1.2 mM XAQ in DMHD(0-3 M)/toluene (s) recorded using a reference solvent of toluene; path length ) 10 mm. The number shown in each spectrum is the concentration of DMHD.
spectrophotometer. For picosecond sample excitation, the second harmonic (347.2 nm) from a mode-locked ruby laser was used and the double-beam absorption spectroscopy was performed by simultaneous intensity measurements of the probing and reference lights using a single polychromator (Unisoku M200) and a dual linear image sensor (Hamamatsu Photonics S4801-512Q) controlled by a personal computer (NEC PC-9801Vm);9 the full width at the half-maximum intensity (fwhm) of the second haromonic was 30 ps. For nanosecond sample excitation, the second harmonic (347.2 nm, fwhm ) 20 ns) from a Q-switched ruby laser was used and the transient absorption spectrum was recorded using a multichannel analyzer controlled by a personal computer (NEC PC-9801RA):10 The decay curve of transient absorption with time was analyzed by means of a combination of a photomultiplier (Hamamatsu Photonics R666) with a storage oscilloscope (Iwatsu TS-8123) controlled by the personal computer. Results As shown in Figure 1, the ground-state absorption spectra (solid lines) recorded for XAQ in DMHD(0-3 M)/toluene using a reference solvent of toluene revealed the intensity increment and broadening (to longer wavelengths) upon addition of DMHD. This spectral change could not be ascribed to the superposition of the absorption due to DMHD on that of XAQ, because even the absorption spectrum of 3 M DMHD shown by the dashed line was very weak at wavelengths longer than 410 nm. Since the absorption spectrum recorded for XAQ in DMHD(1 M)/toluene using a reference solution of XAQ/toluene was found to be consistent with that recorded in DMHD using a reference solvent of DMHD, the spectral change shown in Figure 1 was interpreted in terms of the formation of a groundstate XAQ-DMHD complex. From its equilibrium constant (K) determined in DMHD/toluene by the Benesi-Hildebrand method,11 the fraction (Fc) in DMHD, i.e., the concentration of the ground-state DMHD-XAQ complex divided by the initial concentration of XAQ, was estimated as listed in Table 1; K and Fc for AQ and 1C,8C-AQ as well as the molar extinction coefficients (f at 347.2 nm in toluene) of free AQ, 1C,8C-AQ, and XAQ were also determined for the latter discussion. Picosecond laser photolysis of 1B,8B-AQ in (a) DMHD(1 M)/toluene or (b) DMHD gave rise to the appearance of a
J. Phys. Chem., Vol. 100, No. 5, 1996 1639
Figure 2. Transient absorption spectra obtained by picosecond laser photolysis of 1.2 mM 1B,8B-AQ in (a) DMHD(1 M)/toluene and (b) DMHD; path length ) 2 mm.
TABLE 1: Equilibrium Constant (K) for the Formation of the Ground-State XAQ-DMHD Complex in DMHD/ Toluene, Fraction (Fc) of the Ground-State XAQ-DMHD Complex in DMHD, and Molar Extinction Coefficient (Ef) of Free XAQ at 347.2 nm in Toluene XAQ
K/M-1
Fc
f/M-1 cm-1
AQ 1C,8C-AQ 1B-AQ 2B-AQ 1B,5B-AQ 1B,8B-AQ 1B,5C-AQ 1B,8C-AQ
1.2 3.6 1.1 0.9 3.3 4.4 4.1 3.2
0.89 0.96 0.89 0.87 0.96 0.97 0.97 0.96
2300 5100 3800 2400 5400 5100 5400 5400
transient absorption spectrum as shown in Figure 2; band B3 at a longer wavelength could be observed only in the presence of DMHD, while bands B1 and B2 at shorter wavelengths were identical with those due to the absorptions of the second and lowest excited triplet states of 1B,8B-AQ, respectively, which were populated in toluene without DMHD.4 Similar spectra were also obtained for 1B-AQ and 1B,5B-AQ. For 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ, the results obtained in DMHD(1 M)/toluene were identical with those obtained for 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ in both DMHD(1 M)/toluene and DMHD, but somewhat different results were obtained in DMHD as shown in Figure 3; i.e., no absorptions (bands B1 and B2) responsible for the excited triplet solute molecules were observed. For all the compounds studied here in DMHD, however, a plot of the relative absorbance (At/Amax) of band B3 against time shown by open circles in Figure 4 indicated that a transient species responsible for band B3 was produced within a duration of the excitation light pulse (fwhm ) 30 ps) and decayed following a single-exponential function (the solid curve) with a lifetime (τ) of 80-120 ps; identical results were also obtained in DMHD(1 M)/toluene. Although not shown in Figure 3, the accompanying appearance of an absorption (band B4) during the decrement of band B3 could clearly be seen for 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ in DMHD. And, a plot of At/Amax of band B4 against time shown by closed circles in Figure 4 revealed that the single-exponential rise curve of band B4 with time (shown by the dashed curve in Figure 4) had a time constant which was equal to that (τ) obtained for the decay curve of band B3. For 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ in DMHD(1 M)/ toluene and for 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ in both DMHD(1 M)/toluene and DMHD, the accompanying appear-
1640 J. Phys. Chem., Vol. 100, No. 5, 1996
Figure 3. Transient absorption spectra obtained by picosecond laser photolysis of 1.2 mM 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ in DMHD; path length ) 2 mm.
Nakayama et al.
Figure 5. Transient absorption spectra at 40-ns delay obtained by nanosecond laser photolysis of 1.2 mM XAQ in DMHD(1 M)/toluene; path length ) 10 mm.
Figure 4. Plots of the relative absorbances (At/Amax) of bands B3 (O) and B4 (b) against time in DMHD; monitoring wavelengths for band B3 are 590 nm (1B-AQ), 575 nm (2B-AQ), and 610 nm (1B,5B-AQ, 1B,8B-AQ, 1B,5C-AQ, and 1B,8C-AQ) and that for band B4 is 400 nm. The full and dashed curves are the best-fit single-exponential functions calculated using an excitation pulse width (fwhm) of 30 ps and decay (or rise) times (τ) indicated.
ance of band B4 during the decrement of band B3 was unclear owing to the existence of the second and/or lowest excited triplet states of XAQ. Upon nanosecond laser photolysis of all XAQ in DMHD(1 M)/toluene, however, we found that the transient absorption spectra obtained at the end of pulse excitation (at 40-ns delay) had only band B4 (cf. Figure 5), i.e., no triplettriplet absorption (band B2) due to the lowest excited triplet state of XAQ could be seen. Furthermore, Figure 6 indicated that the relative absorbance (At/Amax) of band B4 at 380 nm decreased with time following the second-order decay kinetics with a decay rate constant (kr) indicated, where r was found to be the molar absorption coefficient of the semiquinone radical of XAQ as discussed later. Discussion Upon picosecond laser photolysis of all the compounds studied here, not only the triplet-triplet absorptions (bands B1 and B2 due to the second (T2) and lowest (T1) excited triplet states of the solute molecule (XAQ), respectively) but also band B3 can be observed in DMHD(1 M)/toluene. These results are identical with those obtained by 347.2-nm excitation of
Figure 6. Decay curve for the relative absorbance (At/Amax) of band B4 monitored at 380 nm (s). The dashed curve is best-fit one calculated based on the second-order decay kinetics with a decay rate constant (kr) indicated, where r is the molar absorption coefficient of the semiquinone radical of XAQ.
1C,8C-AQ1 and AQ2 in DMHD(1 M)/toluene, where 435- or 527-nm excitation gives rise to the appearance of only band B3. Since the time constant estimated for a diffusion-controlled reaction of the lowest excited singlet (S1) state of XAQ with 1 M DMHD is about 100 ps and since the S1 f T2 intersystem crossing times obtained for 1B,8B-AQ4 and 1C,8C-AQ12 are 15-35 ps, the formation of a transient species (responsible for band B3) by a reaction of the S1 or T2 state of XAQ with 1 M DMHD can be ruled out. In fact, band B3 appears within a duration of the picosecond excitation light pulse in both DMHD(1 M)/toluene and DMHD; i.e., the time constant for the appearance of band B3 is not affected by the concentration of DMHD. On the basis of the discussions for the results obtained for 1C,8C-AQ1 and AQ,2 therefore, we again conclude that the transient species responsible for band B3 is an excited singlet charge-transfer complex (or a singlet ion pair) produced by direct excitation of the ground-state XAQ-DMHD complex; in the excited singlet charge-transfer complex or the singlet ion pair,
Excited-State Dynamics of XAQ-DMHD Complexes the negative charge is transferred from DMHD to XAQ. We have no definitive information regarding the structure of the XAQ-DMHD complex in the ground or excited state, although a similar complex formation is also reported for the 9,10dichloroanthracene/DMHD system by Smothers et al.13 In DMHD, only band B3 is observed for 2B-AQ, 1B,5CAQ, and 1B,8C-AQ in accordance with the results obtained for 1C,8C-AQ1 and AQ,2 whereas not only the triplet-triplet absorptions (bands B1 and B2 due to the T2 and T1 states of the free solute molecule, respectively) but also band B3 is observed for 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ. As can be seen from Table 1, however, both the fractions (Ff ) 1 - Fc ) 0.030.13 in DMHD) and the molar extinction coefficients (f ) 2300-5400 M-1 cm-1 at the 347.2-nm excitation wavelength in toluene) of AQ, 2B-AQ, 1B,5C-AQ, 1B,8C-AQ, and 1C,8C-AQ do not differ so much from those (Ff ) 0.03-0.11, f ) 3800-5400 M-1 cm-1) of 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ. Hence, observation of the triplet-triplet absorption bands due to the T2 and T1 states of free solute molecules (1B-AQ, 1B,5B-AQ, and 1B,8B-AQ) even in DMHD may reflect very small molar extinction coefficients (at the 347.2nm excitation wavelength) of ground-state XAQ-DMHD complexes compared with those of free solute molecules. In comparison of the results obtained for 1B-AQ and 2B-AQ with that reported for AQ,2 it is reasonable to conjecture that a chargetransfer interaction between DMHD and the carbonyl group of 2B-AQ (resulting in the formation of the ground-state XAQDMHD complex) is not affected by the bromine atom at the β-position of 2B-AQ; i.e., only the bromine atom at the R-position of 1B-AQ affects the charge-transfer interaction. In connection with this, we have reported that the deformation of molecular structure from the planarity causes an abnormal excited-state behavior; i.e., the phosphorescence spectra of planer AQ and β-haloanthraquinones are of usual nπ* character, while those of R-haloanthraquinones are of mixed nπ*-ππ* or ππ* character with unusually short lifetimes.8,14 Since this abnormal triplet behavior observed for R-haloanthraquinones can be ascribed to the distortion of the geometrical molecular structure caused by the steric hindrance between the oxygen and halogen atoms, and since the electronegativities of the oxygen, chlorine, and bromine atoms are 3.5, 3.0, and 2.8, respectively, the through-space transfer of the negative charge from the halogen to oxygen atoms may result in the smaller net negative charge on the oxygen atom adjacent to the chlorine atom than that adjacent to the bromine atom. Hence, the chargetransfer interaction between DMHD and the carbonyl group of XAQ may decrease in the order of AQ (or the β-bromo compound) g the R-chloro compound . the R-bromo compound. For 1B,5C-AQ and 1B,8C-AQ, therefore, not the carbonyl group adjacent to the bromine atom but that adjacent to the chlorine atom may participate in the formation of the ground-state XAQ-DMHD complex. In fact, excitation of these bromochloro compounds in DMHD gives rise to the appearance of band B3 alone in accordance with the result obtained for 1C,8C-AQ.1 At a delay time of 1 ns, the triplet-triplet (T′ r T1) absorption (band B2) due to the T1 state can be observed for 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ not only in DMHD(1 M)/ toluene but also in DMHD. In contrast, for 2B-AQ, 1B,5CAQ, and 1B,8C-AQ, band B2 is observed only in DMHD(1 M)/ toluene and disappears completely within a delay time of 1 ns. This result is identical with those obtained for 1C,8C-AQ1 and AQ,2 where their T1 states are quenched by DMHD with rate constants (kq) on the order for that of a diffusion-controlled reaction, i.e., kq ) 2.6 × 109 M-1 s-1 for triplet 1C,8C-AQ and kq ) 4.0 × 109 M-1 s-1 for triplet AQ, indicating that no
J. Phys. Chem., Vol. 100, No. 5, 1996 1641 observation of band B2 in DMHD(1 M)/toluene at 1-ns delay might be reasonable. However, a comparison of the phosphorescence spectra of 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ with those of AQ, 2B-AQ, 1B,5C-AQ, 1B,8C-AQ, and 1C,8C-AQ reveals no appreciable difference in the energy levels of the T1 states.8,14,15 For AQ, 1C,8C-AQ, and XAQ, therefore, the quenching of the T1 state by DMHD cannot be interpreted in terms of the donor-acceptor energy gap.16 Probably, a chargetransfer interaction between DMHD and the carbonyl group of triplet anthraquinones, which is similar to that discussed previously for the formation of the ground-state XAQ-DMHD complex, may be the origin for the triplet quenching. In connection with this conjecture, it is well-known that the triplettriplet energy transfer from a number of triplet sensitizers (such as aromatic carbonyl compounds) to 1,3-dienes occurs easily and that the triplet 1,3-dienes produced undergo efficient cistrans isomerization and dimerization.17-19 Furthermore, Kochevar and Wagner20 and Caldwell et al.21 have suggested that triplet exciplexes (or excited triplet charge-transfer complexes) are the intermediates in the cis-trans isomerization of several alkenes photosensitized by triplet ketones. As stated previously, band B3 decays with time following a single-exponential function. For 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ in DMHD, furthermore, the single-exponential decrement of band B3 with time is accompanied by the rate matching increment of band B4 (cf. Figure 4). Owing to the existence of the second and/or lowest excited triplet states of XAQ, however, the accompanying appearance of band B4 during the decrement of band B3 was unclear for 2B-AQ, 1B,5C-AQ, and 1B,8C-AQ in DMHD(1 M)/toluene and for 1B-AQ, 1B,5B-AQ, and 1B,8B-AQ in both DMHD(1 M)/toluene and DMHD. In spite of these circumstances, Figure 5 indicates that band B4 obtained at the end of the nanosecond pulse excitation (40-ns delay) of all XAQ in DMHD(1 M)/toluene is very similar to those of the semiquinone radicals generated by the intermolecular hydrogen-atom abstraction of several triplet anthraquinones from ethanol without DMHD,22-25 although the generation of these semiquinone radicals is observed in the microsecond time regime. Hence, the decomposition of the excited singlet charge-transfer complex (or the singlet ion pair) may give rise to the generation of the semiquinone radical of XAQ and 2,5dimethylhexa-2,4-dien-1-yl radical. This conclusion is consistent with those obtained for 1C,8C-AQ1 and AQ.2 As shown in Figure 6, the absorbance of band B4 decreases with time to a constant value following the second-order decay kinetics: We have confirmed that the absorption band responsible for the nondecay component is identical with that due to the photoreduced product (the haloanthrahydroquinone) which is produced by steady-state photolysis of XAQ in toluene (or ethanol) without DMHD.26 Although the decay rate constants (kr) indicated in Figure 6 are nearly equal to those obtained for 1C,8C-AQ (kr ) 9.0 r × 105 M-1 s-1) and AQ (kr ) 8.6 r × 105 M-1 s-1),2 they are about 1 order of magnitude greater than those (kr ) 5.3 r × 104-1.1 r × 105 M-1 s-1) obtained for the semiquinone radicals of several anthraquinones generated in ethanol without DMHD;21,26,27 r is the molar absorption coefficient of the semiquinone radical of XAQ. It is well-known that the disproportionation reaction of two semiquinone radicals (generated in the absence of DMHD) yields the corresponding anthrahydroquinone and the original anthraquinone simultaneously. Hence, the semiquinone radical generated by the decomposition of the excited singlet charge-transfer complex (or the singlet ion pair) may abstract a hydrogen atom from 2,5-dimethylhexa-2,4-dien-1-yl radical yielding the corresponding haloanthrahydroquinone (XAQH2)28 and a biradical (probably 2,5-dimethyl-1,3,5-hexatriene), although the identification
1642 J. Phys. Chem., Vol. 100, No. 5, 1996 of this compound (produced in the presence of a relatively large amount of DMHD) is very difficult. As the byproducts, furthermore, we have confirmed the presence of dimeric and oligomeric compounds which may be produced by a reaction of 2,5-dimethylhexa-2,4-dien-1-yl radical with DMHD. Conclusion Upon picosecond laser photolysis of haloanthraquinones (XAQ; the bromo and bromochloro compounds) in DMHD(1 M)/toluene, we have presented the appearance of absorption bands due to not only the second and lowest excited triplet states of XAQ but also the excited singlet charge-transfer complex or the singlet ion pair which is generated by direct excitation of the ground-state XAQ-DMHD complex. In this sense, we believe that the present study as well as those for 1,8dichloroanthraquinone1 and anthraquinone2 are typical examples demonstrating simultaneous excitation of a free solute molecule (XAQ) and a ground-state complex formed between XAQ and an additive (DMHD). When one deals with the time-dependent spectral change in order to understand photoinduced intermolecular electron transfer, therefore, great care must be taken regarding not only the origin and identification of the transient species but also the interpretation of the excited-state dynamics, because an ionic transient species is sometimes generated upon direct excitation of a ground-state molecular complex. Acknowledgment. This work was supported by a Grantin-Aid for Priority-Area-Research on Photoreaction Dynamics from the Ministry of Education, Science, Sports and Culture of Japan (No. 06239101). References and Notes (1) Hamanoue, K.; Nakayama, T.; Sasaki, H.; Ibuki, K. J. Photochem. Photobiol. A: Chem. 1993, 76, 7. (2) Nakayama, T.; Nakamura, N.; Miki, S.; Hamanoue, K. J. Chem. Soc., Faraday Trans. 1995, 91, 607. (3) Hamanoue, K.; Nakayama, T.; Yamamoto, Y.; Sawada, K.; Yuhara, Y.; Teranishi, H. Bull. Chem. Soc. Jpn. 1988, 61, 1121. Nakayama, T.; Ushida, K.; Hamanoue, K.; Washio, M.; Tagawa, S.; Tabata, Y. J. Chem. Soc., Faraday Trans. 1990, 86, 95. Hamanoue, K.; Nakayama, T.; Ibuki, K.; Otani, A. J. Chem. Soc., Faraday Trans. 1991, 87, 3731. Hamanoue, K.; Nakayama, T.; Sasaki, H.; Ikenaga, K.; Ibuki, K. Bull. Chem. Soc. Jpn. 1992, 65, 3141. Hamanoue, K.; Nakayama, T.; Asada, S.; Ibuki, K. J. Phys. Chem. 1992, 96, 3736. (4) Hamanoue, K.; Nakayama, T.; Ito, M. J. Chem. Soc., Faraday Trans. 1991, 87, 3487.
Nakayama et al. (5) Hamanoue, K.; Nakayama, T.; Ikenaga, K.; Ibuki, K. J. Phys. Chem. 1992, 96, 10297; J. Photochem. Photobiol. A: Chem. 1993, 69, 305. Nakayama, T.; Hanada, T.; Ibuki, K.; Hamanoue, K. Chem. Phys. Lett. 1993, 209, 367. (6) Nakayama, T.; Takahashi, T.; Ibuki, K.; Hamanoue, K. Chem. Phys. Lett. 1993, 215, 622. (7) Hamanoue, K.; Kajiwara, Y.; Miyake, T.; Nakayama, T.; Hirase, S.; Teranishi, H. Chem. Phys. Lett. 1983, 94, 276. (8) Hamanoue, K.; Nakayama, T.; Tsujimoto, I.; Miki, S.; Ushida, K. J. Phys. Chem. 1995, 99, 5802. (9) Nagamura, T.; Nakamura, N.; Ibuki, K.; Nakayama, T.; Hamanoue, K. ReV. Sci. Instrum. 1993, 64, 2504. (10) Ushida, K.; Nakayama, T.; Nakazawa, T.; Hamanoue, K.; Nagamura, T.; Mugishima, A.; Sakimukai, S. ReV. Sci. Instrum. 1989, 60, 617. (11) Benesi, H. A.; Hildebrand, J. H. J. Am. Chem. Soc. 1949, 71, 2703. (12) Hamanoue, K.; Nakayama, T.; Shiozaki, M.; Funasaki, Y.; Nakajima, K.; Teranishi, H. J. Chem. Phys. 1986, 85, 5698. (13) Smothers, W. K.; Schanze, K. S.; Saltiel, J. J. Am. Chem. Soc. 1979, 101, 1985. (14) Hamanoue, K.; Nakayama, T.; Kajiwara, Y.; Yamaguchi, T.; Teranishi, H. J. Chem. Phys. 1987, 86, 6654. (15) Hamanoue, K.; Nakayama, T.; Yamaguchi, T.; Ushida, K. J. Phys. Chem. 1989, 93, 3814. (16) Birks, J. B. In Photophysics of Aromatic Molecules; WileyInterscience: New York, 1970; p 606. (17) Gorman, A. A.; Gould, I. R.; Hamblett, I. J. Am. Chem. Soc. 1981, 103, 4553. (18) Caldwell, R. A.; Singh, M. J. Am. Chem. Soc. 1982, 104, 6121. (19) Kumar, C. V.; Chattopadhyay, S. K.; Das, P. K. Chem. Phys. Lett. 1984, 106, 431. (20) Kochevar, I.; Wagner, P. J. J. Am. Chem. Soc. 1972, 94, 3859. (21) Caldwell, R. A.; Sovocool, G. W.; Gajewski, R. P. J. Am. Chem. Soc. 1973, 95, 2549. (22) Hamanoue, K.; Yokoyama, K.; Kajiwara, Y.; Nakajima, K.; Nakayama, T.; Teranishi, H. Chem. Phys. Lett. 1984, 110, 25. Hamanoue, K.; Nakayama, T.; Tanaka, A.; Kajiwara, Y.; Teranishi, H. J. Photochem. 1986, 34, 73. (23) Bridge, N. K.; Porter, G. Proc. R. Soc. 1958, A244, 259. (24) Carlson, S. A.; Hercules, D. M. Photochem. Photobiol. 1973, 17, 123. (25) Hulme, B. E.; Land, E. J.; Phillips, G. O. J. Chem. Soc., Faraday Trans. 1 1972, 68, 1992. (26) Hamanoue, K.; Nakayama, T.; Sawada, K.; Yamamoto, Y.; Hirase, S.; Teranishi, H. Bull. Chem. Soc. Jpn. 1986, 59, 2735. (27) Hamanoue, K.; Sawada, K.; Yokoyama, K.; Nakayama, T.; Hirase, S.; Teranishi, H. J. Photochem. 1986, 33, 99. (28) XAQH2 thus produced may causes a subsequent photochemical reaction with DMHD, because such a reaction has been observed for anthrahydroquinone (AQH2) or 1,8-dichloroanthrahydroquinone, and 4′,4′dimethyl-3′-(2-methylprop-1-en-1-yl)spiro[anthracene-10,2′-oxetan]-9(10H)one is obtained from AQH2.2
JP951683L
