Ying-Ying Kou

Oxidative DNA cleavage by Cu(II) complexes of 1,10-phenanthroline-5,6-dione

A dimeric dichloro-bridged copper(II) complex [Cu2(pdon)2Cl4] · 2DMF (1) and two mononuclear copper(II) complexes [Cu(pdon)(DMSO)Cl2] · DMSO · H2O (2) and [Cu(pdon)3] · (ClO4)2 · 2.25CH3CN · 6H2O (3) (pdon = 1,10-phenanthroline-5,6-dione) have been synthesized and characterized. Variable-temperature magnetic susceptibility studies indicate the existence of weak anti-ferromagnetic coupling in the binuclear complex. The interaction of these complexes with CT-DNA (calf thymus DNA) has been studied using absorption and emission spectral methods. The apparent binding constants (K app) for 1, 2 and 3 are 5.20 × 105, 2.68 × 105 and 7.05 × 105 M−1, respectively, showing moderate intercalative binding modes. All of these complexes cleave plasmid DNA to nicked DNA in a sequential manner as the concentration or reaction time is increased. The cleavage mechanism between the complex and plasmid DNA is likely to involve singlet oxygen 1O2 and •OH as reactive oxygen species.

Synthesis and pH-sensitive redox properties of 1,10-phenanthroline-5,6-dione complexes

Synthesis and pH-sensitive electrochemical properties of three complexes, [Cu(PD)3] · (ClO4)2 · 2.25CH3CN · 6H2O (1), [Cu(PD)(DMSO)Cl2] · DMSO · H2O (2) and [Co(PD)3] · (ClO4)2 · CH3CN · 2H2O (3) (PD=1,10-phenanthroline-5,6-dione), are reported. Single-crystal X-ray diffraction of the complexes suggest that the structure of 1 is orthorhombic, 2 triclinic and 3 orthorhombic. The electrochemical properties of free PD and the three complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potentials of these compounds are strongly dependent on the proton concentration in the range −0.3 V ∼ 0.4 V versus SCE (saturated calomel reference electrode). The reduction behavior of PD can be described from quinone species to semiquinone anion then to the fully reduced dianion. At pH < 4, the reduction of PD proceeds via 2e−/3H+ processes, while at pH > 4, the reduction of PD proceeds via 2e−/2H+. For all complexes, the N–N chelate PD ligand is electrochemically active and underwent step reduction via 2e−/2H+.

Synthesis, crystal structure and magnetic properties of an oxamato-bridged heterobinuclear NiIICuII complex [Ni(cyclam)Cu(opba)]2·3DMSO

An oxamato-bridged heterobinuclear NiIICuII complex [Ni(cyclam)Cu(opba)]2 · 3DMSO (1) has been synthesized, characterized by elemental analysis, infrared spectra and magnetic susceptibility, where cyclam is 1, 4, 8, 11-tetraazacyclotetradecane and opba is o-phenylenebis(oxamato). The complex crystallizes in the triclinic system, space group P 1 with a = 12.006(3) Å, b = 12.783(3) Å, c = 20.977(5) Å, α = 76.634(4)°, β = 75.172(4)°, γ = 80.818(4)° and Z = 2. According to X-ray crystallographic studies, the four-coordinate copper(II) atom is a slightly distorted planar geometry and is linked to nickel(II) through the exo-cis oxygen atoms of [Cu(opba)]2−; the six-coordinate nickel(II) center lies in a highly distorted octahedral environment. Magnetic susceptibility measurements of the complex in the temperature range 2–300 K indicate that the heterobinuclear NiIICuII units are coupled antiferromagnetically with J = −57.38 cm−1, g Ni = 2.25 and g Cu = 2.02.