Cations local minima structures

The structure of the 2-norbornyl cation has been a focal point of controversy in physical organic chemistry. Experimental NMR spectroscopy and computational methods have been the decisive tools, favoring the hypercoordinated symmetric bridged structure 30, a protonated nortricyclane.79 The tricoordinated 2-norbornyl cation 31 is not a local minimum (MP2/6-31G(d)) on the energy surface.80... 

Hehre and Hiberty (1972, 1974) have determined that the bisected cyclo-propylcarbinyl cation [33] is a local minimum on the STO-3G potential surface, and that structures such as puckered cyclobutyl cation [35] and homo-allyl cation [101] collapse without barrier to such a form. No evidence for other stable C H+ forms was discovered at this level. 

A double Rydberg anion (DRA) consists of a stable cationic core and two electrons in a diffuse Rydberg orbital. These anions correspond to a local minimum on a potential energy surface where more stable isomers may exist. Experimental and theoretical works have contributed to a better understanding of the unusual electronic structure of these molecules. With electron propagator calculations and analysis of the electron localization function, some relationships between electronic structure and reactivity in DRAs are considered. 

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