Distortion, diagonal rhomboidal

Next, we consider also the effects of rhomboidal distortions, which permit a diagonal interaction. These may either reinforce or counteract the effect of the substituents, depending on which of the two diagonals has been shortened. For a head-to-tail approach of two substituted ethylenes, there will be two funnels corresponding to 1,3-disubstituted critically heterosym-metric biradicaloids, one at less and one at more diagonally distorted geometry than for the unsubstituted ethylene. This is confirmed by the results of calculations shown in Figure 7.30. 

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