We use random searches, basin hopping and simulated annealing techniques to obtain low energy isomers of the B-21 cluster. Our search shows that planar structures dominate the low energy isomers of B-21 for the neutral as well as singly positively and negatively charged states continuing the trend seen for smaller clusters. The ring-like structures previously reported as global minima for the B-20 and B-21 are about 1 eV higher than the most stable planar isomer. The quantum chemical calculations using the second order Moller-Plasset perturbation theory agree with the OFT predictions. (C) 2012 Elsevier B.V. All rights reserved.