Zhi-Quan Pan

DNA-binding and cleavage activity of a new alkoxo and acetate-bridged dinuclear copper(II) complex

A new copper complex, [Cu2L(OAc)(CH3OH)] · CH3OH, where H3L is 1,3-bis(5-methylsalicylideneimino)propan-2-ol, has been synthesized and characterized by single-crystal X-ray diffraction, IR, ES-MS, and UV-Vis techniques. The coordination polyhedra of copper(II) can be described as a tetrahedron and a planar quadrilateral. The interaction between the complex and calf thymus DNA/DNA was investigated by UV-Vis, fluorescence, circular dichroism spectra, and viscosity. All the results show that the interaction mode of the complex with DNA is intercalative with a binding constant of 1.16 × 105 (mol L−1)−1 and linear Stern–Volmer quenching constant of 4.89 × 102 (mol L−1)−1, respectively. Agarose gel electrophoresis exhibits that the complex can transform supercoiled to nicked form and exhibits effective DNA-cleavage activity via hydrolytic-cleavage mechanism.

Syntheses, crystal structures, and properties of two macrocyclic dinuclear Ni(II) complexes bearing 2-pyridylmethyl pendant-arms

Two new dinuclear nickel macrocyclic complexes, [Ni2(II)L1(OAc)] · ClO4 · CH3OH · 0.5H2O (1) and [Ni2(II)L2(OAc)] · CH3CN · ClO4 · 0.5H2O (2), have been obtained and fully characterized [where H2L = macrocycle as the [2 + 2] condensation product of 4-X-2,6-diformylphenol (X = CH3, Cl) and N,N-bis(2-aminopropyl)-N-(2-pyridylmethyl)amine]. The interactions of the complexes with calf thymus-DNA were studied by UV-Vis and CD spectroscopic techniques. The binding constants of 1 and 2 are 1.5 × 105 and 4.9 × 105 (mol L−1)−1, respectively. The complexes exhibit powerful DNA cleavage activity. The cleavage process occurs via an oxidative cleavage and a hydrolytic mechanism for 1, while the mechanism for 2 was a hydrolytic cleavage. The variable-temperature magnetisms show that there are weak antiferromagnetic couplings between Ni(II) ions in [Ni2L(OAc)]+, and the cyclic voltammograms of the complexes are also investigated.

Synthesis and structure of a macrocyclic dinuclear Zn(II) complex together with DNA-binding and kinetic studies

A new macrocyclic dinuclear Zn(II) complex, [Zn2(OAc)L] · ClO4 (H2L was obtained by condensation between 3,3′-(ethane-1,2-diylbis(benzylazanediyl))bis(methylene)bis(2-hydroxy-5-methylbenzaldehyde) and aniline (1 : 2 molar ratio)), was synthesized and characterized by spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The interactions of the complex with DNA have been measured by UV spectroscopy and viscosity experiment. The interaction of the complex with calf thymus DNA has a binding constant of 1.18 × 104 mol−1 L. Phosphate hydrolysis of the complex was investigated using bis(4-nitrophenyl)phosphate as the substrate. The observed first-order rate constant is 4.23 × 10−5  s−1.

Synthesis, crystal structure, electrochemical and magnetic properties of dinuclear complexes with strong electron-drawing groups in the diphenoxo-tetraaza macrocyclic ligand

Three symmetrical macrocyclic dinuclear complexes [M2L(H2O) n ](ClO4)2 (M2+ = Cu2+, Ni2+, Mn2+ and n = 0, 2) have been synthesized by cyclocondensation between 2,6-diformyl-4-fluorophenol and 1,4-diaminobutane in the presence of M2+ cations. The crystal structure of [Cu2L](ClO4)2 was determined by X-ray diffraction techniques. The electronic and magnetic properties of the complexes were studied by cyclic voltammetry and magnetic susceptibility. The results confirm that the complexes obtain electrons easily and there are very strong antiferromagnetic couplings between two copper(II) ions in [Cu2L](ClO4)2. The strong electron-drawing groups of fluorine attached to the phenyl ring of a macrocyclic complex enhances the antiferromagnetic exchange of the complex and makes it more easily reduced than its analogs.

Hexamine copper(II) coordination polymers: synthesis, structure and magnetic properties

Four new one-dimensional (1D) polymeric complexes, {[Cu4(L1)2(µ-Br)2(µ4-CO3)]Br(ClO4)3·3H2O}n (1), {[Cu2L2(µ-Cl)Cl2] (ClO4)2·H2O}n (2), {[Cu2L3(µ-Cl)2](ClO4)2}n (3), and {[Cu2L4(µ-Cl)2](ClO4)2}n (4), have been synthesized and characterized, where L1 = N,N,N′,N′-tetrakis(3′-aminopropyl)-1,3-propylenediamine, L2 = N,N,N′,N′-tetrakis(2′-aminoethyl)-1,3-propylenediamine, L3 = N,N,N′,N′-tetrakis(2′-aminoethyl)-1,4-butylenediamine, L4 = N,N,N′,N′-tetrakis(2′-aminoethyl)-1, 6-hexylenediamine. X-Ray structure analysis revealed that the polymeric complexes, created by the bridging groups which are exhibited in the formula, present different 1D coordination motifs: double-stranded chains with voids of 43.5 A2 for 1, sigmoid chains for 2, zigzag chains for 3 and 4 with different coordination polyhedra. Various hydrogen bonding interactions such as N–H⋯Cl, N–H⋯O, C–H⋯Cl, N–H⋯Br and O–H⋯Br join the polymeric chains to generate two-dimensional networks with bigger voids. Magnetic susceptibility data were fitted according to the molecular structures using Hamiltonians: H = −2J1(S2S3 + S1S4) − 2J2(S2S1) − 2J3(S1S3 + S2S4) − 2J4(S3S4), which corresponds to a rectangular array of spins for 1, and H = −2JS1S2 corresponds to a dinuclear array of spins for 2, 3 and 4. It was found that the coupling constants of 1 are −60, −113, −54 and −11 cm−1, and those of 2, 3, and 4 are −2.46, −1.56 and −0.15 cm−1, respectively.

Two dinuclear Schiff-base complexes: synthesis, characterization, and biological activity

Two complexes, [Zn2L(µ-OAc)](ClO4) (1) and [Mn2L(OAc)2] · 4H2O (2), were synthesized by [2 + 2] cyclo-condensation between 2,6-diformyl-4-fluorophenol and 1,3-propyldiamine in the presence of metal ions M(II) (M = Zn and Mn), and were characterized by chemical analyses, IR spectra, electrospray mass spectra, and X-ray determinations. The results show that 1 forms dimers through hydrogen bonding. In 2, lattice waters, forming a 1-D water chain, function as glue to form a 3-D supramolecular network through extended hydrogen bonding. pBR322 plasmid DNA can be transformed to nicked form in air by 1 or nicked and linear forms in air by 2. Moreover, their antibacterial activities against S. aureus were investigated using penicillin as reference system.

DNA cleavage activities of two dinuclear copper coordination polymers

The DNA cleavage activities of two coordination polymers of Robson-type macrocycles, {[Cu4L1(4,4′-bipy)2](ClO4)4·H2O}∞ (1) and {[Cu4L2(4,4′-bipy)4](ClO4)4·2CH3CN·2H2O}∞ (2) (where H2L1 and H2L2 are the [2 + 2] condensation products of 1,3-diaminopropane with 2,6-diformyl-4-methylphenol and 2,6-diformyl-4-fluorophenol, respectively), have been studied. The interactions of the complexes with calf thymus-DNA were investigated by UV–vis spectroscopy, CD spectroscopy, and gel electrophoresis. The binding constants of 1 and 2 are 7.2 × 104 and 2.1 × 105 M−1, respectively. The complexes exhibit DNA cleavage activity, with the cleavage process involving oxidative cleavage of DNA. The DNA cleavage activities of two new coordination polymers of Robson-type macrocycles, {[Cu2L1(bipy)]·(ClO4)2·CH3CN}∞ (1) and {[Cu2L2(bipy)]·(ClO4)2·H2O}∞ (2), have been studied. The interactions of the complexes with calf thymus-DNA were studied by UV–vis and CD spectroscopic techniques. The complexes exhibit good DNA cleavage activity. The results show that the substituent on the benzene ring plays an important role in DNA cleavage and the cleavage process occurs via oxidative cleavage.

A thiophenopolyamine Cu(II) complex fixed by atmospheric carbon dioxide: synthesis, structure and properties

A new trinuclear complex, {[Cu(L)]3 (μ3-CO3)}(ClO4)4 (L = N-(2-thiophenoethyl)-N,N-bis (3-aminopropyl)amine), was synthesized and characterized by single-crystal X-ray analysis. The complex contained three identical mononuclear copper(II) units connected by the μ3-carbonate formed from atmospheric carbon dioxide. The electronic and magnetic properties were studied by cyclic voltammetry and the measurement of magnetic susceptibility, respectively. The μ3-bridging model revealed weak ferromagnetic coupling of Cu(II), with the J value of −11.28 cm−1 and the Zeeman splitting g value of 2.06, which were determined by means of magnetic measurements in the 2–300 K range.

Crystal structures and DNA cleavage activities of two mononuclear nickel(II) complexes

Two new nickel complexes, [Ni(L1)2] · 2(CH3OH) (1) and [Ni(L2)2] · 2(CH3OH) (2), where HL1 is 4-chloro-2-((2-hydroxy-ethylimino)methyl)phenol and HL2 is 4-fluoro-2-((2-hydroxy-ethylimino)methyl)phenol, have been synthesized and characterized by single-crystal X-ray diffraction and UV-Vis absorption spectra. The coordination polyhedron of nickel(II) in each complex can be described as distorted octahedral. The interactions between the complexes and calf thymus (CT)-DNA/DNA were investigated by UV-Vis spectra and agarose gel electrophoresis. The results show that the complex transforms supercoiled to nicked form and exhibits effective DNA cleavage activity via hydrolytic cleavage mechanism.

Coordination polymers of polyamine and macrocycles controlled by pyridine-containing arms

N,N′-bis(3-aminopropyl)-3-pyridylmethylamine (bapa) has been synthesized as a building block for coordination polymers, and its coordination polymer {[Cu(bapa)(MeCN)][Cu(bapa)(ClO4)] (ClO4)3·MeCN}∞ (1) was obtained by reacting it with Cu(ClO4)2·6H2O in MeCN solution. In addition, three macrocyclic coordination polymers, {[CuL1](H2O)2}∞ (2), {[MnL1](H2O)2}∞ (3) and {[CuL2]CH3CN·H2O·ClO4}∞ (4), were obtained by the condensation between bapa and N,N′-bis(3-formyl-5-methylsalicylimine)-1, 2-propylenediimine for 2 and 3, and N,N′-bis(3-formyl-5-methylsalicylidene)-1,2-ethylenediimine for 4 in the presence of Cu(II), Mn(II) and Cu(II), respectively. These polymers have the common feature that the 3-methylaminopyridine group in one ligand coordinates to the metal ion in the neighboring coordination unit, leading to the formation of a one-dimensional infinite chain. There are abundant hydrogen bonds in each of the complexes, involving water clusters and perchlorate anions.