Results and Discussion
Figure 1 shows the optimized geometries of the radical anions. The T1 diagnostic values of the CCSD(T)/def2-TZVP//M06-2X/def2-TZVP calculations are all lower than 0.02 suggesting single determinant character of the wave functions. For the Be containing compounds, high lying isomers are also located in the potential energy surface which feature no Be-Be interaction. These no Be-Be bond isomers are very high in energy and represents bond stretch isomers which were theoretically explained in 1972 by Hoffmann and co-workers for the polytopal rearrangement of (CH)5+, (CH)5 and (CH)4CO.21 However, for Zn containing compounds, such high lying isomers (or bond stretch isomers) were not located on the potential energy surface. It is to be noted that all these molecules shown in Figure 1 are local minima in the potential energy surface with real values of Hessian matrix. The Be-Be distance in these compounds ranges from 2.586 to 2.450 Å with the shortest been found with –CN as the substituent attached to Be atoms. The computed Wiberg bond indices (WBIs) are in the range of 0.146 to 0.195. Similarly, for Zn containing compounds, the Zn-Zn bond distance ranges from 2.909 to 3.023 Å. The computed WBIs are in the range of 0.258 to 0.268. Thus, these radical anions feature a strong Be-Be and Zn-Zn bonds.