Collision of CH3CN and CH3NC with He*(2(3)S) metastable atoms has been studied by collision-energy resolved Penning ionization electron spectroscopy. Collision energy dependence of the partial ionization cross sections indicates that the interaction potentials are strongly anisotropic between He*(2(3)S) and the molecules investigated, In the studied energy range, the interaction potential is attractive if the metastable atom approaches the pseudohalide group along the CCN or CNC frame, but it is repulsive around the methyl group. Model potential curves for the collision of CH3CN and CH3NC with Li(2(2)S) atoms have been calculated and the computational strategy discussed. The quantum chemical calculations and the spectroscopic investigations predict the existence. of stable C2H3NLi radicals, and their structure is characterized using the MP2/6-31+G** method.