Two polynuclear copper(II)-squarate compound,,, of formulas [Cu(HBIP)(BIP)](C4O4)(1/2)(.)2H(2)O (1) and [{Cu(BIP)(OH2)}(4)(mu -C4O4)](ClO4)(2)(.)4H(2)O (2) (HBIP = 3,3-bis(2-imidazolyl)propionic acid) have been synthesized and characterized by single-crystal X-ray diffraction. Both Compounds crystallize in the triclinic system, space group P1. with a =7.947( 1) Angstrom, b = 12.327(4) Angstrom. c = 13.150(3) Angstrom, alpha = 113.91(2)degrees, beta = 99.85(2)degrees, gamma = 90.02(2)degrees for compound 1 and a = 8.010( 1) Angstrom. b = 13,073(1) Angstrom. c = 14.561 (1) Angstrom. alpha = 72.13(1)degrees, beta = 80.14(1)degrees, gamma = 84.02(1)degrees for compound 2. The structure of compound I can be viewed as made up of [Cu(HBIP)(BIP)] units linked together by the BIP carboxylate groups to form a one-diniensional chain Structure along the a axis in the crystal. The copper ion is fi e-coordinated (CuN4O chromophore) with BIP and HBIP acting as tridentate and bidentate ligands. respectively. The coordination geometry is intermediate between SP and TBP. The structure of compound 2 is made of infinite chains built from cationic tetranuclear [{Cu(BIP)(OH2)}(4)(mu -C4O4)](2+) Complex units, two uncoordinated perchlorate anions. and four water molecules of crystallization. The squarato group bridges the copper(II) ions. while BIP acts as a tridentate ligand, connecting through its carboxylate group the tetrameric units along the a axis. The two crystallographical ly independent copper(II) ions are pentacoordinated within a distorted square-based pyramid. Electronic and EPR spectra are consistent with the crystallographic data. Both compounds follow a Curie-Weiss law with very low values of theta (-0.13 and +0.12 K). In compound 2, the weak ferromagnetism interaction is discussed on the basis of the structural features and correlated with Published magnetostructural data on similar squarato-bridged copper(II) compounds.