Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

Inner sphere reorganisation energies for self-exchange electron transfer (λe) reactions are calculated as being lower than those associated hole transfer processes (λh) in model planar phenyl and thiophenyl substituted DPP systems. It is found that λe < λh for all planar ring/DPP core structures examined. The effect on λh/e of non-planarity between phenyl substituents and DPP core is explored in detail. The relative ordering of λh and λe is dependent upon the torsional angle of phenyl rings and reverses at twist angles of greater than 60° such that λe > λh.