N22C2 versus N24: role of molecular curvature in determining isomer stability.

Three-dimensional N(22)C(2) cages are examined by theoretical calculations to determine relative stability among various isomers. Stability as a function of cage shape and stability as a function of carbon location are calculated and discussed. The results are compared to isomers of N(24) to determine the effects of carbon substitution into the cage structure. Further, since the various cage shapes in this study vary by degree of curvature, model calculations are carried out to determine the energetic consequences of curving the local structure around nitrogen and carbon. The model calculations are compared to the actual results on the larger cages to determine how well curvature effects explain the relative stability of N(22)C(2) isomer as compared to the corresponding N(24).