Ring currents in six-membered heterocycles:: the diazaborinines (CH)2B2N2

Six of the eleven possible cyclic isomers (CH)(2)B2N2 are found, by geometric optimization at a correlated level of theory, to have planar closed-shell ground states. Current density maps calculated with distributed-origin coupled Hartree-Fock theory wavefunctions show that all six of these have delocalized pi-electron systems supporting diamagnetic ring currents. In comparison with benzene at the same level of theory, the isomer with lowest energy, 1,3,2,4 diazadiborinine, has a 5% greater centre of ring shielding, but 20-25% smaller mean magnetizability, mean polarizability and polarizability anisotropy.