At the CCSD(T)/6-311＋G(2df)//B3LYP/6-311＋G(d) level, the geometries, infrared vibrational spectrum, relative energies as well as the isomerization and dissociation stability of a tetra-atomic molecule [GeCN2] were studied. A detailed [GeCN2] potential energy surface was constructed, and seven [GeCN2] isomers were located, covering five linear forms GeNCN (1), GeNNC (2), NGeCN (3), NGeNC (4), GeCNN (5), and two cyclic forms Ge-cCNN (6) and Ge-cNCN (7). Amongst, the isomers 5, 6 and 7 are our newly-found species. In particular, the isomer GeCNN (5) is the second most-stable one on the overall [GeCN2] potential energy surface. The structural and electronic analysis indicates that the GeCNN (5) possesses a conjugate triply bonded structure |Ge≡C—N≡N|. Since the GeCNN (5) has good thermodynamic and kinetic stability, it was expected to be observable in laboratory. Finally, it was found that coordination by transition metal carbonyl complexes could further stabilize the GeCNN (5). The present study could provide useful theoretical clues for future search of potential multiply bonded molecules containing higher-row elements.

Key words: Ge≡C—N≡N, triple bond, potential energy surface, stability