Radio Frequency Magnetic Field Effects on a Radical Recombination Reaction: A Diagnostic Test for the Radical Pair Mechanism

Abstract

The photoinduced electron-transfer reaction of chrysene with isomers of dicyanobenzene is used to demonstrate the sensitivity of a radical recombination reaction to the orientation and frequency (5−50 MHz) of a ∼300 μT radio frequency magnetic field in the presence of a 0−4 mT static magnetic field. The recombination yield is detected via the fluorescence of the exciplex formed exclusively from the electronic singlet state of the radical ion pair Chr^•+/DCB^•-. Magnetic field effects are simulated using a modified version of the γ-COMPUTE algorithm, devised for the simulation of magic angle spinning NMR spectra of powdered samples. The response of a chemical or biological system to simultaneously applied radio frequency and static or extremely low-frequency magnetic fields could form the basis for a diagnostic test for the operation of the radical pair mechanism that would not require prior knowledge of the nature and properties of the radical reaction.