Laser flash photolysis of 1,8-bis(substituted methyl)naphthalenes

Abstract

The transient absorption spectra obtained by the laser flash photolysis of 1,8-bis(substituted methyl)naphthalenes [(PhX–CH₂)₂Naph; X = O, S, Se] have been measured. By comparison with the transient spectra for 1-(substituted methyl)naphthalenes, the transient species absorbing at 430 nm observed from (PhO–CH₂)₂Naph is attributed to the triplet state. In the case of (PhS–CH₂)₂Naph, absorption bands at 490 and 430 nm due to PhS˙ are observed in addition to an absorption band in the region of 310–400 nm, which is due to the carbon-centred radical [˙CH₂Naph(CH₂–SPh)]. For (PhSe–CH₂)₂Naph, a new broad absorption band appeared in the region of 400–520 nm, which covered weak absorption bands due to PhSe˙ at 430 and 490 nm. The new absorption is attributed to the carbon-centred radical [˙CH₂Naph(CH₂–SePh)] in which there is considerable interaction between the ˙CH₂–and PhSe moieties. The possibility of a bridged radical for ˙CH₂Naph(CH₂–SePh) is suggested by MO calculations.