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Two copper(II) complexes of disubstituted 2,2'-bipyridine (bpy = 2, 2'-bipyridine) with tetraalkylammonium groups, [Cu(L1)2Br](ClO4)5·2H2O (1) and [Cu(L2)2Br](ClO4)5·H2O (2) (L1 = [4, 4'-(Et3NCH2)2-bpy]2+, L2 = [4, 4'-((n-Bu)3NCH2)2-bpy]2+), have been synthesized and characterized. X-ray crystallographic study of 1 indicates that Cu(II) is a distorted trigonal bipyramidal or square pyramid. DNA binding of both complexes was studied by UV spectroscopic titration. In the presence of reducing reagents, the cleavage of plasmid pBR322 DNA mediated by both complexes was investigated and efficient oxidative cleavage of DNA was observed. Mechanistic study with reactive oxygen scavengers indicates that hydrogen peroxide and singlet oxygen participate in DNA cleavage. [ABSTRACT FROM AUTHOR]

Abstract: A series of Cu(II) complexes of disubstituted 2,2′-bipyridine bearing ammonium groups [Cu(L1−4)2Br]5+ (1–4, L1 =[5,5′-(Me2NHCH2)2-bpy]2+, L2 =[5,5′-(Me3NCH2)2-bpy]2+, L3 =[4,4′-(Me2NHCH2)2-bpy]2+, L4 =[4,4′-(Me3NCH2)2-bpy]2+ and bpy=2,2′-bipyridyl) were synthesized, of which complexes 1 and 4 were structurally characterized. Both coordination configurations of Cu(II) ions can be described as distorted trigonal bipyramid. The interaction between all complexes and CT-DNA was evaluated by thermal-denaturation experiments and CD spectroscopy. Results show that the complexes interact with CT-DNA via outside electrostatic interactions and their binding ability follows the order: 1 > 2 > 3 > 4. In the absence of any reducing agents, the cleavage of plasmid pBR322 DNA by these complexes was investigated and the hydrolysis kinetics of DNA was studied in Tris buffer (pH 7.5) at 37°C. Obtained pseudo-Michaelis–Menten kinetic parameters: 15.0, 13.6, 2.01 and 1.69h−1 for 1, 2, 3 and 4, respectively, indicate that complexes 1 and 2 exhibit very high DNA cleavage activities. According to their crystal data, the high nuclease activity may be attributed to the strong interaction of the metal moiety and two ammonium groups with phosphate groups of DNA. [Copyright &y& Elsevier]