Structure and dynamics of triethylamine and tripropylamine radical cations generated in AlPO4-5 by ionizing radiation: an EPR and MO study

Abstract

An EPR study was carried out to investigate both the structure and molecular dynamics of triethylamine (Et₃N) and tripropylamine (Pr₃N) radical cations generated in γ-irradiated AlPO₄-5 from neutral mother molecules incorporated as an organic template. Both Et₃N^+• and Pr₃N^+• radical cations were stable at 300 K and showed strongly temperature-dependent EPR spectral line-shapes in the temperature range from 77 to 300 K. The spectral change was successfully explained by assuming a two-site exchange model in which two inequivalent β-hydrogens interchange their positions with each other. The experimental spectra were quantitatively analyzed by a simulation method using the exchange rate as a variable parameter. From an Arrhenius plot of the rate constants, activation energies of 9.1 and 11.4 kJ mol⁻¹ were evaluated for Et₃N^+• and Pr₃N^+• in AlPO₄-5, respectively.