Using density functional theory calculations, we investigated the structure and electronic properties of cyclooctatetraene (CH, COT)-ligand mono- or bi-transition-metal (M) sandwich clusters, M (COT) (M = Sc, Ti, Cr, Mn, = 1, 2) or (COT)M(COT)M(COT), as well as their one-dimensional infinite molecular wires. All the sandwich M-COT clusters and molecular wires are rather stable with their binding energies ranging from 3.20 to 7.48 eV per transition-metal atom. Superior to M Bz complexes, most sandwich M-COT complexes are in their high spin states with ultrahigh magnetic moments. Moreover, one-dimensional infinite molecular wires, [Cr(COT)], [(COT)V(COT)Ti] and [(COT)Sc(COT)Cr], are predicted to be ferromagnetic half-metals. Our findings suggest that such M-COT sandwich complexes may be potential candidates for applications in spintronics.