Solvent Dependence of Magnetic Field Effects upon Photoisomerization of 2-(3,3-Dimethyl-1-butenyl)naphthalene in the Presence of Electron Acceptors.

The efficiency of isomerization of trans-2-(3,3-dimethyl-1-butenyl)naphthalene (t-BN) in the presence of electron accepters was reduced by an applied magnetic held in polar solvents such as acetonitrile. This effect together with laser flash photolysis studies indicates that the precursor of isomerization is the BN triplet arising from intersystem crossing of a singlet radical pair consisting of a t-BN cation and an acceptor anion. The external magnetic field effect as well as laser flash photolysis was employed to estimate the contribution of ion radical pairs to the isomerization of t-BN in the presence of p-dicyanobenzene in various solvents. The t-BN triplet was produced most efficiently almost through an exciplex in chloroform (epsilon=4.8) among the employed solvents.