REKS calculations on ortho-, meta- and para-benzyne

Spin-restricted ensemble-referenced Kohn-Sham (REKS) calculations have been performed on isomeric benzyne systems. The density functional results compare favorably with those of multi-reference CASPT2 and CASRS3 methods. In general for enthalpies of isodesmic reactions, the REKS energies are in better agreement with experiment compared with the ab initio calculations. Experimental singlet-triplet energy gaps are reproduced to within 1 kcal mol- of experimental values.