Electronic States of Aminonitrene ( 1 , l - Diazine ) . A Study of the Endwise Bonding of Dinitrogenla

The ground and excited states of aminonitrene (1 ,I-diazine), H2NN, were studied using generalized valence bond (GVB) and configuration interaction (GVB-CI) wave functions. We find that the ground state is a singlet state ( 'Ai) with the triplet (3A2) lying 15 kcal/mol higher. ( In the Hartree-Fock description, the triplet state is 5 kcal below the singlet, indicating the necessity of including electron-correlation effects.) The stabilization of the singlet state is due to a large amount of double bond character in the N N bond (HzN+=N:-) as reflected in the short bond length ( R , = 1.25 A) and the large dipole moment ( f i = 4.036 D). In contrast, the 3A2 state has Re = 1.37 A and p = 2.35 D. With extensive CI we find an N N bond energy of Do(H2NN) = 69 kcal/mol, leading to a heat formation of AHf2,,,(H2NN) = 90 kcal/mol. The character of higher excited states and ions is also discussed. Some predictions of the thermochemistry of 1,l-diazines are provided.