Unconventional ring currents in an 'all-metal aromatic', Al42-

The square planar anion Al-4(2-) supports an unconventional diamagnetic ring current which originates in the a system, has negligible contribution from the two-electron pi system, and survives in pyramidal bimetallic clusters MAI, (M = Li, Na, Cu). (C) 2001 Elsevier Science B.V. All rights reserved.