Octahedral aromaticity in 2S+1A1g X6q clusters (X = Li-C and Be-Si, S=0-3, and q =-2 to+4)

It is generally observed that quintessential aromatic compounds have delocalised electronic configurations that are of closed-shells or open-shells half-filled with the same spin electrons. Guided by this property, we search for aromatic octahedral clusters of the type X-6(q) (X = Li-C and Be-Si, q = -2 to +4) in (2S+1)A(1g) electronic states with spin multiplicities ranging from the singlet to the septet. With some exceptions, we find that closed-shells or open-shells half-filled with same spin electron systems have large multicentre indices and negative NICS values that are characteristic patterns of aromatic compounds. Our results confirm the existence of octahedral aromaticity but do not allow us to define a general rule for octahedral aromaticity because the ordering of molecular orbitals does not remain the same for different octahedral clusters.