A new 2-D cluster-based polymer {[Cu(I)(6)Cu(II)(6)L(6)(H(2)O)(3)(CH(3)OH)(6)].5H(2)O.3CH(3)OH}(n) (2) (H(3)L = C(6)H(5)C(O)NHC(S)NHCH(2)COOH) containing unique mixed-valence [Cu(I)(6)Cu(II)(6)L(6)] subunits was synthesized by reaction of single crystals of [Ln(2)(H(2)L)(4)(Phen)(2)(NO(3))(2)] (Ln = Pr (1a), Nd (1b) or Ho (1c)) (Phen = 1,10-phenanthroline) with copper(II) acetate in aqueous DMF. Interestingly, cation-exchanged products {[Cu(I)(6)Cu(II)(5)Zn(H(2)O)(3)(CH(3)OH)(6)].5H(2)O.3CH(3)OH}(n) (3) or {[Cu(I)(6)Cu(II)(4)Co(2)(H(2)O)(3)(CH(3)OH)(6)].5H(2)O.3CH(3)OH}(n) (4) were obtained from single crystals of and the appropriate M(NO(3))(2) (M = Zn or Co) in H(2)O.