Electronic states of the GeC2N radical are explored at various theoretical levels including complete active space multi-configuration self-consistent field followed by complete active space perturbation computations. Ten minimal energy isomers and 10 interconversion transition states are found. The thermodynamically most stable isomer is a linear form GeCCN 1 which is qualitatively described as a resonance hybrid of vertical bar Ge=C=C=N vertical bar, vertical bar Ge=C.-C N vertical bar, and vertical bar Ge=C=C=N vertical bar. forms, with the second one contributing to a greater extent suggestive of a radical adduct between Ge=C and C =. The second low-lying linear isomer GeCNC 2 (21.9 kcal/mol) has resonating structures vertical bar Ge=C.-N=C vertical bar, vertical bar Ge=C=N C vertical bar, and vertical bar Ge=C=N-C vertical bar. (c) 2007 Elsevier B.V. All rights reserved.