Structural features of several species based on Sb-3 as a nuclear unit are investigated by ab initio analysis. In particular, the applicability of the Zintl-Klemm-Busmann (ZKB) principle on alkali-antimony clusters of the form A(3)Sb(3) and A(4)Sb(3)(+) (A = Na, K, Rb) is examined, which have been detected by mass spectrometric measurements. It is shown that basic properties pertaining to geometry, bonding, and stability of these 18 valence electron units display a clear analogy to the respective features of the isoelectronic ozone molecule. We conclude that A(3)Sb(3) represents a case in which the ZKB principle, so far almost exclusively applied to solids and liquids, is valid for the gaseous phase as well. An extension of the ZKB principle, which according to its traditional meaning involves transfer of charge, to spin-transfer processes is proposed. Possible experimental tests regarding.the geometries of the species investigated are pointed out.