Theoretical study on the structures and properties of the isomers of Nn(CH)8−nH8 (n = 0-7)

With replacement of N atoms by CH groups in the most stable chain isomer of N8H8, 34 possible isomers of Nn(CH)8−nH8 (n = 0-7) have been designed and optimized at the B3LYP/6-311++G∗∗ level of theory. The natural bond orbital (NBO) and atoms in molecules (AIM) analysis are carried out to study the bonding nature and relative stabilities of these conformers. G3MP2 method is applied to calculate energies and heats of formation. The results indicate that the hyperconjugation effect from lone pairs of nitrogen atoms to germinal C-N bonds is the major factor which caused the change of the C-N bond length. With the more replacement of nitrogen atoms by CH groups, the heats of formation of the isomers of Nn(CH)8−nH8 (n = 0-7) decrease gradually, but the energies increase linearly.