RADICAL-CATION OF N,N-DIMETHYLPIPERAZINE - DRAMATIC STRUCTURAL EFFECTS OF ORBITAL INTERACTIONS THROUGH BONDS

The radical cation of N,N-dimethylpiperazine (DMP) has been studied us ing time-resolved optical absorption and resonance Raman spectroscopy. Different quantum-chemical methods were used to calculate the molecul ar structures and vibrational force fields in the ground state of the radical cation and in the resonant excited state. An excellent agreeme nt between theoretical and experimental vibrational frequencies as wel l as resonance Raman intensities could be achieved. It is concluded th at through-sigma-bond interaction between the formal lone pair on one amino nitrogen and the odd electron on the other is strong enough to l ead to a symmetric charge-delocalized molecular structure of the DMP r adical cation, with a chair-type geometry.