The photoreaction of $\underline{trans}$-1.2-bispyrazylethylene ($\underline{trans}$-BPE) with tetracyanoethylene (TCNE) was studied in comparison with that of stilbene.
Stilbene undergoes dehydrophotocyclization in the presence of TCNE.
$\underline{Trans}$-BPE, one of the N-hetero aromatic compounds, has the $(n-\pi^*)$ excited state which is absent in stilbene. Thus, $\underline{trans}$-BPE has different photochemical reactivities and photophysical properties compared to those of stilbene.
The fluorescence of $\underline{trans}$-BPE is well quenched by ground state of TCNE with the quenching constant of 1.6×$10^{10}/mol.\sec$.
$\underline{Trans}$-BPE and TCNE solution in benzene was irradiated by 350nm UV light and the product was separated by recrystallization from the benzene solution. Major product was 1.2-dipyrazine-3,3,4,4-tetracyanocyclobutane which was formed by ($\pi^2+\pi^2$) cycloaddition.
The structure of the adduct was confirmed by the characteristics in their NMR, IR, UV and mass spectra.
$\underline{trans}$-BPE와 TCNE를 벤젠 용매에서 350nm의 자외선으로 광반응 시켰으며 광반응 생성물은 고리화 부가반응에서 얻은 1.2-dipyrazine-3,3,4,4-tetracyano cyclobatane 이였다.
TCNE는 trans-BPE의 형광을 매우 잘 ?칭했으며 이때 ?칭 반응 속도상수는 1.6×$10^{10}$ ℓ/mol·sec 이다.
아마도 $(\pi-\pi^*)$ 단일상태의 \underline{trans}$-BPE가 바닥상태의 TCNE 와 들뜬상태착물을 만드는 것으로 생각되며 이 들뜬상태 착물에서 생성물이 얻어졌으리라 생각된다.