The hexahomotrioxacalix[3]arene macrocycles 1 are observed to bind trivalent metals (Sc3+, Lu3+,Y3+, La3+) more strongly than alkali metal ions (Li+, Na+, K+). Complexes of macrocycle la with Lu(III) (3), Y(III) (4), and La(III) (5) have been structurally characterized to be mu-aryloxo-bridged dimers with the formula [M(L)(DMSO)](2) (M = Lu, Y, La; L = trianion of macrocycle 1a). Periodic trends in the structures and dynamic behavior of the complexes are discussed.