Regioselective Ultrafast Photoinduced Electron Transfer from Naphthols to Halocarbon Solvents

Excited state decay of 2-naphthol (2N) in halocarbon solvents has been observed to be significantly slower when compared to that of 1-naphthol (1N). In this study, we provide new physical insights behind this observation by exploring the regioselective electron transfer (ET) mechanism from photoexcited 1N and 2N to halocarbon solvents at a detailed molecular level. Using state-of-the-art electronic structure calculations, we explore several configurations of naphthol-chloroform complexes and find that the proximity of the electron-accepting chloroform molecule to the electron-rich -OH group of the naphthol is the dominant factor affecting electron transfer rates. The origin of significantly slower electron transfer rates for 2N is traced back to the notably smaller electronic coupling when the electron-accepting chloroform molecule is on top of the aromatic ring distal to the -OH group. Our findings suggest that regioselective photoinduced electron transfer could thus be exploited to control electron transfer in substituted acenes tailored for specific applications.