B13+ cluster is a unique nano-scale tri-spoke wheel which exhibits rotor action. This rotor action is associated with the interconversion between two closely lying states - the minimum energy ground state (GS) and a closely lying transition state (TS) of this planar cluster in which a B4 subunit successively transforms from the square shape in GS to the diamond shape in TS. In the present study, the square to diamond fluxional interconversion of the B4 subunit has been explored through electronic structural analysis including AdNDP, LOL and AIM analysis. Nucleus independent chemical shift (NICS) study has also been carried out for both the parent cluster and the B4 unit to understand the inter-relationship in the aromatic character of these clusters. The electronic scale origin of the fluxional character of the B4 cluster has been explored and its connection with the diamond-square-diamond (DSD) mechanism can be foreseen.