Citation: Calderon-Casado, Ainhoa; Barandika, Gotzone; Bazan, Bego\~na; Urtiaga, Miren-Karmele; Arriortua, Mar\'ia-Isabel (2010). Unprecedented coordination modes for PDC (pyridine-2,5-dicarboxylate) in polymorphic 3D heterobimetallic compounds \a- and \b-[MNa2(PDC)2(H2O)4], with M = Ni, Co. CrystEngComm, 12, pp. 1784-.