Reaction of a Bis(benzoylhydrazone) with Copper(II): Complex Formation, Hydroxylation, and DNA Cleavage Activity

Abstract

The reaction of the ditopic bis(benzoylhydrazone) of isophthalaldehyde (H2L) with copper(II) acetate in methanol under aerobic conditions afforded a green solid that contains the tetranuclear complex [Cu4L*2(OCH3)2] (1). The ligand L*, a bis(benzoylhydrazone) of 2,6‐diformylphenol, resulted from hydroxylation of the corresponding isophthalaldehyde derivative. H2L and 1 were characterized by different spectroscopic techniques, and their molecular structures were confirmed by single‐crystal X‐ray diffraction. The reaction of H2L with copper(II) under argon, on the other hand, resulted in a brown diamagnetic solid [Cu2L]·H2O (2) containing copper(I), which was readily transformed into 1 when exposed to air. In contrast, the reaction with [Cu(CH3CN)4][BF4] afforded a mononuclear complex [Cu(H2L)][BF4]·H2O (3), and single crystals of [Cu(H2L)2][BF4] (4) were isolated from its dichloromethane solution. H2L cleaved plasmid DNA in the presence of copper(II) independently of any reducing agent, but more efficiently when ascorbate was present. The cleavage process is likely oxidative because the enzyme catalase, which decomposes hydrogen peroxide, quenched the reaction. In the absence of ascorbate, the ligand H2L presumably acts as the reductant in the redox reaction, as exploited also in the synthesis of 1. As a consequence, a variety of reactive oxygen species were generated, eventually also leading to the cleavage of DNA (“self‐activating” chemical nuclease).

Self-Assembly by Tridentate or Bidentate Ligand: Synthesis and Vapor Adsorption Properties of Cu(II), Zn(II), Hg(II) and Cd(II) Complexes Derived from a Bis(pyridylhydrazone) Compound

“…The copper atom is coordinated with three oxygen atoms and one nitrogen atom in the basal positions, and a methanol oxygen atom (for Cu1) or a methoxide oxygen atom (for Cu2) in the axial position. In the molecule, the Cu1-Cu2 distance is 2.957(4) Å, which is consistent with similar complexes found in the literature [33,34]. Noticeably, [Cu2(µ 3 -OCH 3 ) 2 Cu2a] forms a square with Cu2-Cu2a separation of 2.973(5) Å and the distance of the two µ 3 -methoxide oxygen atoms bridged by Cu2/Cu2a is 2.969(4) Å, which is well comparable with previously reported copper complexes [35] 3as colorless block crystals.…”

New VIV, VIVO, VVO, and VVO2 Systems: Exploring their Interconversion in Solution, Protein Interactions, and Cytotoxicity

“…However, 1 and 2 possess a band in the range 3436–3321 cm –1 , for the uncoordinated −OH group attached to the aroylhydrazide moiety of their corresponding ligands. , The free ligands also exhibit characteristic stretching bands in the region 3059–3022 (ν N–H ) and 1649–1637 (ν C=O ) cm –1 for their amide moiety, which are not observed in the spectra of their respective complexes ( 1 – 3 ). Additionally, the appearance of new bands in the complex within 1244–1234 cm –1 , due to the stretching vibration of the conjugated CN–NC–O – moiety, clearly indicate the coordination of the ligands in their deprotonated enolic form. ,− Moreover, the presence of one sharp band at 982 cm –1 for 1 , due to the ν­(VO) stretching, indicates the mono-oxido nature of the complex, ,,, while its absence in the spectra of 2 and 3 agrees with the presence of “bare” vanadium centers. ,, …”

Transition Metal Complexes with 1‐Adamantoyl Hydrazones – Cytotoxic Copper(II) Complexes of Tri‐ and Tetradentate Pyridine Chelators Containing an Adamantane Ring System

“…[7,8] Very recently, some copper(II) complexes with acylhydrazone ligands were reported as efficient DNA binders with enhanced cytotoxic potency, and correlation between DNA binding and cytotoxic activity is often an important step in the investigation of new antitumor agents. The square-pyramidal and square-planar Cu II complexes derived from bis(benzoylhydrazone) showed superior DNA binding properties, [9] whereas Cu II complexes with ferrocene-based acylhydrazones exhibited significant cleavage of supercoiled pUC19 DNA in the presence of hydrogen peroxide as co-oxidant. [10] Cu II complexes prepared from acylhydrazone bearing a naphthalene ring bind to calf thymus DNA (CT-DNA) by both groove binding and intercalation; [11] furthermore, the Cu II acylhydrazone complex prepared from 2-acetylpyridine benzoylhydrazone indicated an intercalative mode of binding between the complex and CT-DNA.…”