EPR studies on carboxylic esters. Part 17. EPR spectra and spin densities in the radical anions of thio and dithiocoumarins

The radical anions of 4-methyl-l-thiocoumarins and 4-methyl-l-thio-2-thionocoumarins are generated by internal electroreduction and studied by EPR spectrosopy. The spin density distribution is evaluated from the proton hfs coupling constants and by MO calculations. The radical anions of the corresponding cournarins and 2-thionocournarins are not persistent enough for EPR spectroscopic measurements.