Synthesis, photophysical and computational studies of two lophine derivatives with electron-rich substituents in the 2-position

Abstract An exploration of the photophysical properties of two lophine derivatives with electron-donating groups in the 2-position began with the preparation of compounds 1 and 2 via one-pot reactions in good yields, 83% and 74%, respectively. The absorption spectra of 1 and 2 had bands at approximately 300 nm (e ≈ 25,000–34,000 M −1  cm −1 ), while that of 2 had an additional band at 348 nm (e = 35,600 M −1  cm −1 ). These absorptions were assigned to π→π* transitions. Excitation into the absorption band of 1 at approximately 300 nm produced emission at 387 nm, while excitation into either of the absorption bands of 2 produced emission at 406 nm. Of the two compounds, 2 had the higher quantum yield. The emission spectra of compounds 1 and 2 were slightly blue-shifted at 77 K. Excited state lifetimes for 1 and 2 were short (indicating that the observed emission was fluorescence) at room temperature and 77 K, ranging from 1.1 to 1.8 ns. Computational studies of both compounds 1 and 2 were performed to better understand how their structures relate to their photophysical properties.