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.