2010) Synthesis, characterization, and biological activity studies of copper(II)-metal(II) binuclear complexes of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazoneA new series of copper(II) mononuclear and copper(II)-metal(II) binuclear complexes [(H 2 L)Cu] Á H 2 O, [CuLM] Á nH 2 O, and [Cu(H 2 L)M(OAc) 2 ] Á nH 2 O, n ¼ 1-2, M ¼ Co(II), Ni(II), Cu(II), or Zn(II), and L is the anion of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone), H 4 L, were synthesized and characterized. Elemental analyses, molar conductivities, and FT-IR spectra support the formulation of these complexes. IR data suggest that H 4 L is dibasic tetradentate in [(H 2 L)Cu] Á H 2 O and [Cu(H 2 L)M(OAc) 2 ] Á nH 2 O but tetrabasic hexadentate in [CuLM] Á nH 2 O (n ¼ 1-2). Thermal studies indicate that waters are of crystallization and the complexes are thermally stable to 347-402 C depending upon the nature of the complex. Magnetic moment values indicate magnetic exchange interaction between Cu(II) and M(II) centers in binuclear complexes. The electronic spectral data show that d-d transitions of CuN 2 O 2 in the mononuclear complex are blue shifted in binuclear complexes in the sequences: Cu-Cu 4 Cu-Ni 4 Cu-Co 4 Cu-Zn, suggesting that the binuclear complexes [CuLM] Á nH 2 O are more planar than the mononuclear complex. The structures of complexes were optimized through molecular mechanics applying MM þ force field coupled with molecular dynamics simulation. [(H 2 L)Cu] Á nH 2 O, [CuLM] Á nH 2 O, and the free ligand were screened for antimicrobial activities on some Gram-positive and Gramnegative bacterial species. The free ligand is inactive against all studied bacteria. The screening data showed that [CuLCu] Á H 2 O 4 [(H 2 L)Cu] Á H 2 O 4 [CuLZn] Á H 2 O 4 [CuLNi] Á 2H 2 O % [CuLCo] Á H 2 O in order of biological activity. The data are discussed in terms of their compositions and structures.