In this paper, we report mass spectrometry studies on C2nN5-cluster ions by collision-induced dissociation (CID). The mass-selected cluster ions were dissociated by collision with a crossed nitrogen beam and the fragment ions were mass analyzed in a secondary mass spectrometer. Characterization of the species as cyano-substituted, planar five-membered rings is supported by density functional theory (DFT) calculations. Based on the analysis of the experimental and computational results, cluster structures, energies, and stabilities are discussed.