COMPUTATIONAL METHODS
Planar BxNx (x = 2 – 11) clusters were
optimized at the PBE048/def2-TZVP49level of theory using Gaussian 09 computational
package50. For the fully optimized molecules,
vibrational frequency calculations were performed at the same level to
ensure that we obtained a true minimum on the potential energy surface.
NICSzz values were computed employing the
Gauge-Including Atomic Orbital (GIAO) in gas phase at the
above-mentioned level. Ring current strength (RCS) calculations were
done using AIMAll51 software. Chemical bond was
analysed through Adaptative Natural Density Partitioning (AdNDP), this
method is a generalization of NBO method. AdNDP recovers Lewis bonding
(1c-2e lone pairs, 2c-2e two electron bonds), additionally, localized
bonds associated with (anti)aromaticity. NICSzz scans,
FiPC and NICSzz isosurfaces and AdNDP orbitals were
obtained using our own routines and Multiwfn
software52. Visualization of NICSzzisosurfaces and NICSzz isolines have been plotted using
Chemcraft and VisIt 2.13.0 respectively53,54.