Eight new copper(II) complexes of 2-benzoylpyridine N(4),N(4)-(butane-1,4-diyl)thiosemicarbazone (HBpypTsc) with general stoichiometry CuBpypTscX [X=N-3, Cl, NO3, NCS, ClO4, Br, SH and CN] were synthesized and characterized by IR and UV-Vis spectroscopies. The terdentate nature of the ligand is inferred from the IR spectra. Spin Hamiltonian parameters of the compounds were calculated from the EPR spectra. The structures of the compounds CuBpypTscCl (2), CuBpypTscBr (6) and CuBpypTscSH (7) were solved by single crystal X-ray diffraction. CuBpypTscCl (2) is a centrosymmetric dimer with chloro bridges. The geometry around copper in other two complexes is square planar. (C) 2003 Elsevier Ltd. All rights reserved.