C(2)nN(7)(-) cluster ions are produced by laser ablating on the K-3[Fe(CN)(6)] sample. DFT calculations have been performed for these cluster anions. Various isomeric structures of these clusters are optimized and their energies are compared to find the most stable isomers. The most stable structure for C8N7- is similar to that of adenine by theoretical calculation, which is in agreement with the collision-induced dissociation ( CID) experimental results. With the increasing even numbers of C atoms from 8 to 16, the N atoms in the double-ring structure are gradually substituted by C atoms from the six-membered ring to the five-membered ring. All these C(2)nN(7)(-) (n = 3-9) clusters exhibit planar aromatic characters. The energy difference and incremental binding energy analyses show that C(2)nN(7)(-) (n = 4-8) clusters are more stable than C6N7- and C18N7-, which are consistent with the observed mass spectrum.