Valence isomers of benzene and their relationship to the isoelectronic isomers of arsenic molecule (As6)

Abstract

We report the results of geometry-optimized ab initio SCF-MO calculations for As 6 in structural forms corresponding to the five valence isomers of benzene, C 6 H 6 , with which As 6 is valence-isoelectronic. We used Scuseria's 752+P polarized basis set for arsenic. The resulting energy ordering of As 6 isomeric structures is very similar to what we found previously for P 6 isomers but quite different from that known for the C 6 H 6 valence isomers. For As 6 , as for P 6 , prismane and benzvalene structures have the lowest energies while the planar hexagon (benzene) has the highest. The range of energies of the five structures is small, around 45 kcal/mol, somewhat larger than for the P 6 isomers but far smaller than for C 6 H 6