AbstractThree novel oxamidato‐bridged complexes incorporating a macrocyclic oxamide of formula [(CuL)3{CuL(C2H5OH)}Eu(H2O)](ClO4)3·1.5H2O (1), [(CuL)3{CuL(C2H5OH)}Tb(H2O)](ClO4)3·2H2O (2) and [(NiL)5Sm](ClO4)3·2H2O (3) (CuL and NiL, H2L = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclopentadeca‐7,13‐dien), have been hydrothermally synthesized and structurally characterized. In these complexes, the central LnIII and external copper (or nickel) ions are bridged by macrocyclic oxamide groups. The EuIII (or TbIII) ion of 1 (or 2) resides in a distorted tricapped trigonal prismatic environment surrounded by eight oxygen atoms from four oxamide groups and one oxygen atom from a water molecule, whereas the SmIII ion of 3 resides in a distorted bicapped square antiprismatic environment surrounded by ten oxygen atoms from five oxamide groups. Furthermore, there are hydrogen bonding interactions in 1 and 2 between perchlorate, ethanol and water moieties. Especially for 1 and 2, O−H···O and weak coordination of ClO4− groups link the pentanuclear fragments and perchlorate ions to form a 1‐D supramolecular architecture. The fluorescence of EuIII and TbIII are almost completely quenched in 1 and 2. The magnetic properties of 1 and 2 have been characterized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)