5 詳細
Semi-empirical PM3 calculations predict the fluorescence quantum yields of 4-monosubstituted benzofurazan compounds
S. Uchiyama, T. Santa, N. Okiyama, K. Aduma and K. Imai
J. Chem. Soc., Perkin Trans. 2, 2000, 1199-1207.
■ Abstract
We have elucidated the relationship between the fluorescence quantum yield of 4-monosubstituted benzofurazan (2,1,3-benzoxadiazole) compounds and the substituent group at the 4-position using a group of eleven such compounds. The absorption and fluorescence spectra of these compounds were measured in fifteen different solvents. Semi-empirical PM3 calculations were carried out to obtain the optimized geometry, energies, charges and dipole moments of this group in the ground and excited states. The S1-T2 energy gaps obtained from the PM3-CAS/CI calculations, which reflected the probability of S1-->T2 intersystem crossing, related well to the fluorescence quantum yield of the 4-monosubstituted benzofurazan compounds in nonpolar solvents. It also appeared that the decrease in the S1-T1 energy gaps was related to the change in the fluorescence quantum yield due to solvent effects. In highly polar solvents, non-radiative S1-->T2 intersystem crossing occurs, in addition to non-radiative S1-->T2 intersystem crossing, in 4-monosubstituted benzofurazan compounds, as they have a larger dipole moment in the S1 state than in the T2 state. These studies have enabled us to predict the fluorescence quantum yield for a series of 4-monosubstituted benzofurazan compounds.
■ 内容
４位一置換ベンゾフラザン化合物のシクロヘキサン中における蛍光量子収率が，半経験的分子軌道法PM3-CAS/CI 法によって算出したS1-T2のエネルギー差と良好な関係にあったという論文です．
■ ひとこと
JACS Reject → JOC Reject → JCS Minor revision でアクセプト．この論文の内容は，当時教室配属された４年生，沖山さん（現花王）のテーマとして始めました．これまでの自分の研究は，４，７二置換化合物に対して行っていたのですが，セミナー中に「一般則を導きたいなら，ひとまずもっと化合物を単純にしてみたら？」という同級生からの意見をいただいたことが，きっかけとなっています．沖山さんが M1 になってテーマが変わり，僕が引き継いでまとめました．やはり，化合物を単純にしたことによって，わかりやすい関係が得られたのだと思います．