The Lowest Photoexcited Triplet State of Subphthalocyanine in Solid and Fluid Environments. Time-Resolved Electron Paramagnetic Resonance Studies

Abstract

Time-resolved EPR spectra of the lowest excited triplet state of boron subphthalocyanine chloride have been measured in toluene at various temperatures (5−360 K). On the basis of the observed and simulated spectra, electronic structure and molecular motion of the triplet state (1T) were analyzed, both in solid and fluid solution. The simulations were carried out using a model, which considers a temperature-dependent exchange between sites having different zero-field splitting (ZFS) parameters and molecular orientations. The ZFS parameter, D, was nearly the same at all temperatures examined. At very low temperatures, below 20 K, the spectrum was analyzed by a static model. At 40−120 K, two conformers with different ZFS parameter, E, have been found. The population ratio between the two conformers showed strong temperature dependence. These conformers were attributed to Jahn−Teller states and were identified by their different ZFS parameters. The exchange rate and activation energy of the conformers were co...