Synthesis and characterization of water‐soluble copper(II), cobalt(II) and zinc(II) complexes derived from 8‐hydroxyquinoline‐5‐sulphonic acid: DNA binding and cleavage studies

Abstract

Three water‐soluble complexes, [Cu2L2Cl2] (1), [CoL2(im)2] (2) and [ZnLClH2O] (3) (HL = 8‐hydroxyquinoline‐5‐sulphonic acid; im = N‐methylimidazole), were prepared and characterized using various spectral techniques. The DNA binding behaviour of complexes 1–3 was studied using UV–visible and circular dichroism (CD) spectra and cyclic voltammetry. All three complexes exhibit hypochromism but complexes 1 and 3 alone give a red shift of 4 nm with a significant binding constant of Kb = 2.1 × 104 and 1.0 × 104 M−1, respectively, but complex 2 shows no red shift with lower Kb of 4.1 × 103 M−1. The voltammetric E1/2 of complex 1 on interaction with herring sperm DNA shifts to a more positive potential, as expected, than complex 2 due to higher DNA affinity. Additionally, analysis of electrochemical data yields a value of K+/K2+ greater than one suggesting that complex 1 binds to DNA through intercalation in the M(I) state. Evidently in CD spectral analysis, complex 1 exhibits a decrease in molar ellipticity with a red shift of 10 nm and a significant decrease in intensity compared to complexes 2 and 3. This clearly indicates that complex 1 induces the B → A transition to a greater extent than 2 and 3. Oxidative cleavage using circular plasmid pUC18 DNA with complex 1 was investigated using gel electrophoresis. Interestingly, complex 1 displays a strong DNA binding affinity and is efficient in cleaving DNA in the presence of H2O2 at pH = 8.0 at 37 °C.

A novel series of M(II) complexes of 6‐methylpyridine‐2‐carboxylic acid with 4(5)methylimidazole: Synthesis, crystal structures, α‐glucosidase activity, density functional theory calculations and molecular docking

“…The calculated magnetic moments of complexes 1 – 6 are found to be 4.48, 4.57, 4.25, 4.51, 4.72 and 4.78 BM, respectively. These results confirm the coordination geometry of complexes and are consistent with previously reported results …”

“…In this regard, the thermal, spectral and physicochemical properties of some metal complexes containing 4(5)MeI have been reported . Furthermore, there are a number of studies of the synthesis, crystal structure and biological activity of metal(II) complexes in the literature …”

Oxazolidine copper complexes: Synthesis, characterization and superoxide dismutase activity of copper(II) complexes with oxazolidine ligands derived from hydroxyquinoline carboxaldehyde

“…No red shift was observed in all cases and this is indicative of non‐observed electrostatic interaction of the copper(II) quinolyl complexes and DNA . The observed change in bands caused by interaction can be indicating the coordinated ligand interaction via hydrogen bonding with the DNA bases and the strong copper(II) center ion interaction with ct‐DNA (Figure ). The intrinsic binding constants ( K b ) of the compounds were calculated using equation and are summarized in Table .…”

Synthesis, Characterization, Antimicrobial and Anticancer Activities of 14-Membered Macrocyclic Schiff Base Metal Complexes

“…Few transition metal chelates of pyrazolone derivatives are of large attention due to their biological activity. Amongst the derivatives of pyrazolone, 4-aminoantipyrine forms a wide number of Schiff bases with ketones/aldehydes and is recognized to be superior reagents in pharmacological, clinical, analytical and biological applications [8,9]. The biological activities of such Schiff bases are further improved by complexation with transition metal ions.…”