The possibility of stabilizing an electronically metastable anion in a molecular trap is studied using ab initio electronic structure methods. The B-2(2g) C2H4- d-wave shape resonance state is used as the metastable anion solute, and a pair of inwardly oriented LiCN molecules (NCLi...LiCN) is used as a molecular trap. Although the global minimum of the C2H4 + 2LiCN + e system is the (LiCN)(2)(-) anion with a weakly (van der Waals) bound C2H4 molecule, it was found that for the (NCLi...LiCN) trap at its local minimum geometry, the B-2(2g) state becomes electronically stable and is the ground state of the system. It is also found that, in this model trap, three other (excited) anionic states are bound ((2)A(g), B-2(1u), and B-2(2u)). Detailed numerical results are presented for the (NCLi...H2C=CH2...LiCN)(-) species (i.e., the trapped ethylene anion) whose vertical electron detachment energy is 2.97 eV at the CCSD(T) level with the augcc-pVDZ basis sets. (C) 2003 Elsevier Science B.V. All rights reserved.