Anisotropic S1T1 intersystem crossing of 1-chloromethylnaphthalene

Relative populating rates and zero-field splitting parameters of the lowest triplet state of naphthalene derivatives were measured by time-resolved ESR. In most of the naphthalene derivatives, in-plane triplet sublevels were more populated than out-of-plane sublevels by S1T1 intersystem crossing (ISC), whereas the highest in-plane sublevel was less populated than the other sublevels in 1-chloromethylnaphthalene (1CMN). This exceptional anisotropy in the ISC of 1CMN was interpreted by the internal heavy atom effect of the chlorine atom.