ESR Line-width Alternation and Na+ Transfer in the Ion Pairs of 3,5-Dinitropyridine

An ESR study of the ion pairs of 3,5-dinitropyridine with alkali metals in tetrahydrofuran and 1,2-dimethoxyethane is reported. The analysis of the ESR spectra of the ion pair with Na+ after the addition of sodium tetraphenylborate shows an intermolecular cation transfer between DNP-·Na+ and Na+BPh4-. Kinetic parameters are compared with those of the corresponding reaction of m-dinitrobenzene. The interpretation of the ion pairs structure is supported with ab initio calculations of the electrostatic potential generated by the 3,5-dinitropyridine radical anion. The spin distribution in the ion pair is computed by the McLachlan method modified according to McClelland. The same method is adopted to study the exchange mechanism by evaluating the association energy for the triple ions.