Photochemical decomposition of amidobiphenyls in highly excited triplet states studied by stepwise two-color laser photolysis

Yamaji, Minoru; Nishio, Makoto

doi:10.1016/j.jphotochem.2007.07.016

Cited by 6 publications

(3 citation statements)

References 36 publications

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“…In an effort to overcome this drawback, several research groups have begun to explore stepwise two-photon excitation (s-TPA), described in Scheme 1. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Scheme 1. Idealized scheme of a stepwise, two-photon absorption process Initial excitation of a substrate (S) generates an intermediate species (I).…”

Section: Introductionmentioning

confidence: 99%

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Photoacid Generators Activated through Sequential Two-Photon Excitation: 1-Sulfonatoxy-2-alkoxyanthraquinone Derivatives

2021

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Two sulfonate ester derivatives of anthraquinone, 1-tosyloxy-2-methoxy-9,10-anthraquinone (1a) and 1-trifluoromethylsulfonoxy-2-methoxy-9,10-anthraquinone (1b) were prepared and their ability to produce strong acids upon photoexcitation was examined. It is shown that these compounds generate acid with a yield that increases with light intensity when the applied photon dose is held constant. Additional experiments show that the rate of acid generation increases 4 fold when visible light (532 nm) laser pulses are combined with ultraviolet (355 nm) compared with ultraviolet alone.Continuous wave diode laser photolysis also effects acid generation with a rate that depends quadratically on the light intensity. Density functional theory calculations, laser flash photolysis, and chemical trapping experiments support a mechanism whereby an initially formed triplet state (T 1 ) is excited to a higher triplet state which in turn undergoes homolysis of the RS(O 2 )-OAr bond. Secondary reactions of the initially formed sulfonyl radicals produce strong acids. It is demonstrated that high intensity photolysis of either 1a or 1b can initiate cationic polymerization of ethyl vinyl ether.

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Section: Introductionmentioning

confidence: 99%

“…This in turn increases the expense and limits the ability to run such processes on scale. In an effort to overcome this drawback, several research groups have begun to explore stepwise two-photon excitation (s-TPA), described in Scheme . − …”

Section: Introductionmentioning

confidence: 99%

Photoacid Generators Activated through Sequential Two-Photon Excitation: 1-Sulfonatoxy-2-alkoxyanthraquinone Derivatives

2021

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“…Recently, Majima's group and ourselves have been studying bond cleavage reactions in highly excited triplet (T n ) states of aromatic compounds and aromatic carbonyls by means of twocolor two-laser photolysis techniques. 8- 16 The method of multistep excitation has been widely used to investigate photophysical and photochemical processes in highly excited states by other researchers. 17- 24 In our foregoing paper, we reported photochemical properties of b-bond cleavage of C-O bond in the T n states of some biphenyl derivatives.…”

Section: Introductionmentioning

confidence: 99%

Stepwise two-color laser photolysis studies of α-cleavage in highly excited triplet states of α-acyl-4-phenylphenols

Yamaji

2008

Photochem Photobiol Sci

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The photochemical properties of alpha-cleavage of C-O bond in highly excited triplet states (T(n) with n>2) of p-biphenyl acetate and p-biphenyl benzoate (Me-OBP and Ph-OBP) in solution were investigated in comparison with those in the lowest excited singlet and triplet states by using single laser and sequential two-color two-laser photolysis techniques. Upon 266 nm laser photolysis of Me-OBP and Ph-OBP, occurrence of C-O bond cleavage in the excited singlet state was recognized from the observation of the formation of p-phenylphenoxy radical (PPR) in the transient absorption. The quantum yields (Phi(rad)) of the PPR formation were determined to be 0.29 and 0.24 for Me-OBP and Ph-OBP, respectively. Triplet sensitization using acetone (Ac) provided efficient formation of the lowest triplet states (T(1)) of Me-OBP and Ph-OBP, and the molar absorption coefficients of the triplet-triplet absorption were determined. No photochemical reactions were found in the T(1) state. Upon 355 nm laser flash photolysis of the T(1) states of Me-OBP and Ph-OBP, formation of PPR accompanied with decomposition of the triplet state was confirmed in the transient absorption. This observation indicated that alpha-cleavage proceeds in the highly excited triplet state. The quantum yields (Phi(dec)) of the decomposition in the dissociative highly excited triplet state (T(R)) were determined to be 0.25 and 0.15 for Me-OBP and Ph-OBP, respectively. The reaction mechanism for alpha-bond cleavage in the T(R) state was discussed.

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Photodecomposition Profiles of β-Bond Cleavage of Phenylphenacyl Derivatives in the Higher Triplet Excited States during Stepwise Two-Color Two-Laser Flash Photolysis

et al. 2008

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Photochemical properties of p-phenylphenacyl derivatives (PP-X) having C-halide, C-S, and C-O bonds in the lowest (T 1) and higher (T n ) triplet excited states were investigated in solution by using single-color and stepwise two-color two-laser flash photolysis techniques. PP-Xs (X = Br, SH, and SPh) undergo beta-bond dissociation in the lowest singlet excited states (S 1) while the C-X bonds of other PP-Xs are stable upon 266-nm laser photolysis. The T 1(pi,pi*) states of PP-X were efficiently produced during 355-nm laser photolysis of benzophenone as a triplet sensitizer. Triplet PP-Xs deactivate to the ground state without photochemical reactions. Upon 430-nm laser photolysis of the T 1 states of PP-X (X = Br, Cl, SH, SPh, OH, OMe, and OPh), decomposition of PP-X in the T n states was found. On the basis of the changes in the transient absorption, quantum yields (Phi dec) of the decomposition of PP-X in the T n states were determined, while bond dissociation energies (BDE) of the C-X bonds were calculated by computations. According to the relationship between the Phi dec and BDE values, it was shown that the decomposition of PP-X in the T n state is due to beta-cleavage of the corresponding C-X bond, and that the state energy of the reactive T n for the C-O bond cleavage differs from that for the C-halide and C-S bond cleavage. The reaction profiles of the C-X bond cleavage of PP-X in the T n states were discussed.

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Photochemical decomposition of amidobiphenyls in highly excited triplet states studied by stepwise two-color laser photolysis

Cited by 6 publications

References 36 publications

Photoacid Generators Activated through Sequential Two-Photon Excitation: 1-Sulfonatoxy-2-alkoxyanthraquinone Derivatives

Photoacid Generators Activated through Sequential Two-Photon Excitation: 1-Sulfonatoxy-2-alkoxyanthraquinone Derivatives

Stepwise two-color laser photolysis studies of α-cleavage in highly excited triplet states of α-acyl-4-phenylphenols

Photodecomposition Profiles of β-Bond Cleavage of Phenylphenacyl Derivatives in the Higher Triplet Excited States during Stepwise Two-Color Two-Laser Flash Photolysis

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