The radical cation of N,N-dimethylpiperazine is investigated by resonance Raman spectroscopy and ab initio calculations. The calculations strongly support the assignment of the vibrational spectrum to a chair conformation. It is shown that a dramatic geometry relaxation following ionization allows a much more efficient interaction between the nitrogen 'lone pairs' than in the neutral ground state.
Brouwer, A. M., Langkilde, F. W., Bajdor, K., & Wilbrandt, R. (1994). Through-bond interaction in the radical cation of N,N-dimethylpiperazine: Resonance Raman spectroscopy and quantum chemical calculations. Chemical Physics Letters, 225(4-6), 386-390. https://doi.org/10.1016/0009-2614(94)87099-3