Stepwise photocleavage of two C-O bonds of 1,8-bis[(4-benzoylphenoxy)-methyl]naphthalene with three-step excitation using three-color, three-laser flash photolysis

Xichen Cai; Masanori Sakamoto; Michihiro Hara; Sachiko Tojo; Akihiko Ouchi; Kiyohiko Kawai; Masayuki Endo; Mamoru Fujitsuka; Tetsuro Majima

doi:10.1021/ja049007x

Stepwise photocleavage of two C-O bonds of 1,8-bis[(4-benzoylphenoxy)-methyl]naphthalene with three-step excitation using three-color, three-laser flash photolysis

J Am Chem Soc. 2004 Jun 23;126(24):7432-3. doi: 10.1021/ja049007x.

Authors

Xichen Cai¹, Masanori Sakamoto, Michihiro Hara, Sachiko Tojo, Akihiko Ouchi, Kiyohiko Kawai, Masayuki Endo, Mamoru Fujitsuka, Tetsuro Majima

Affiliation

¹ The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.

PMID: 15198577
DOI: 10.1021/ja049007x

Abstract

Stepwise photocleavage of two naphthylmethyl-oxygen bonds of 1,8-bis[(4-benzoylphenoxy)methyl]naphthalene (1,8-(BPO-CH2)2Np, 1) was observed during three-color, three-laser flash photolysis at room temperature. The mechanism from 1 to the final product, acenaphthene (2), was clearly elucidated. The first (308 nm, 5 mJ pulse-1) XeCl laser excited 1 to the lowest triplet excited state 1(T1), in which the excited energy was localized in the naphthalene moiety, but the C-O bond cleavage did not occur. The second (430 nm, 7 mJ pulse-1) OPO laser excited 1(T1) to the higher triplet excited states 1(Tn) in which the excited energy is delocalized in the naphthalene moiety and C-O bonds, and one C-O bond cleavage occurred. The third (355 nm, 10 mJ pulse-1) YAG laser excited the carbon-centered radical in the ground state 1-(BPO-CH2)NpCH2*(D0) to its excited states 1-(BPO-CH2)NpCH2*(Dn), from which the second C-O bond cleavage occurred to give 2 as the final product. This is a successful example of stepwise cleavage of two equivalent C-O bonds in a molecule using three-color three-laser photolysis method.