Discrete homo Cu–Cu–Cu and hetero Cu–Pd–Cu or Cu–Co–Cu metal arrays are prepared within an organic-pillared coordination box by inserting M(II)-azaporphine/porphine cartridges (M = Cu(II), Pd(II) or Co(II)), where the metal arrays show unique spin interactions in ESR: in particular, ms = 3 for the Cu–Cu–Cu array.