Structures and thermochemistry of B3N3 and B4N4

The mixed boron-nitrogen clusters B3N3 and B4N4 has been studied using augmented coupled-cluster methods. Both molecules have monocyclic ground state structures (1A1′ and 1A1g, respectively) with cumulenic-type equal bond lengths and alternating bond angles (BNB sharp, NBN blunt). The second most stable structures are linear BNBNBN(BN), with a 3Π ground state and alternating polyacetylenic-type bond lenghts. B3N3 and B4N4 have intense infrared bands predicted to fall in the 1550–1650 and 1700–1800 cm−1 regions, respectively. Both B3N3 and B4N4 are stable, with ΣDe = 697.0 and 995.6 kcal/mol, respectively.