How transient photoconductivity reveals significant features of the reduction of ground-state aromatic ketones by amino-alkyl radicals through a thermal electron-transfer process

摘要

The rate constants k_(red) of the thermal electron-transfer reaction between several amino-alkyl radicals and two ground-state aromatic ketones, benzophenone (BP) and thioxanthone (TX), were measured by nanosecond transient photoconductivity in acetonitrile. The kveti values were strongly at variance from those expected from the free energy change ΔG_(red) of the reaction within the framework of the Marcus' theory of electron transfer. Moreover, addition of small amounts of water in acetonitrile strongly enhanced k_(red) and the ion quantum yield. These results were rationalized by invoking a 1: 1 complex formation between amino-alkyl radicals and water, and semi-empirical AMI calculations were used to sustain this explanation.