We have designed a bidentate ligand with multi-proton donor property as a building block of models for one-dimensional heterobimetallic complexes. We have synthesized [Cu(bbim)(2)]((n)Bu(4)N)(2) (1) as a candidate for the building block of such one-dimensional complexes. The crystal structure analysis of 1 and magnetic characterization by single-crystal ESR spectroscopy have been carried out. The crystal data is as follows : orthorhombic, P2(1)2(1)2, a = 17.860 Angstrom, b = 20.274 Angstrom, c = 8.704 Angstrom, Z = 2. ESR measurements of non-magnetically diluted single crystals of 1 have shown that Cu(II) ions are in the tetrahedral ligand field with great tetragonal distortion, being in accord with the molecular structural data on 1 by the X ray analysis.