Qiu-Yue Lin

Synthesis, DNA interaction and antibacterial activities of La(III) and Gd(III) complexes of Schiff base derived from o-vanillin and lysine

Two novel complexes, [La(HL)(H2O)2NO3] · NO3 · H2O and [Gd(HL)(H2O)2NO3] · NO3 · H2O, where HL is a Schiff base derived from o-vanillin and lysine, have been synthesized and characterized by elemental analysis, conductivity measurements, IR, 1H NMR and thermogravimetric analyses (TGA). The Schiff base ligand behaves as a tetradentate, coordinating through azomethine nitrogen, phenolic oxygen and two carboxylic oxygen atoms. The interaction of these complexes with calf thymus DNA (CT-DNA) was also investigated by spectrometric titration and viscometric measurements. The faint hypochromism of the complexes in the absorption spectra, the remarkable reduction of fluorescence intensity of ethidium bromide (EB) bound DNA, together with a small decrease in the viscosity of the DNA suggest that a partial intercalation may be the preferred binding mode between these two complexes and DNA. The antibacterial activity testing revealed that the complexes and their precursor Schiff base show a weak to moderate activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli.

Synthesis, crystal structure, interaction with BSA and antibacterial activity of La(III) and Sm(III) complexes with enrofloxacin.

Two new La(III) and Sm(III) complexes with enrofloxacin (HER, 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid, C19H21FN3O3), [La2(ER)6(H2O)2]·14H2O(1) and [Sm2(ER)6(H2O)2]·14H2O(2) have been synthesized and characterized by elemental analysis, FT-IR, TG-DTG and X-ray single crystal diffraction. Both of the complexes are triclinic system with space group Pī. The structure of the complexes show that each rare earth atom in both complexes was nine-coordinated. Two of the enrofloxacin ions acted as tridentate chelate and bridging ligands, while the others as bidentate chelate ligands. The binding reaction between the complexes and bovine serum albumin (BSA) was studied by UV-vis absorption spectra and fluorescence spectroscopy. The results indicated that the two complexes had a quite strong ability to quench the fluorescence from BSA and the binding reaction was mainly a static quenching process. The binding constants KA/(L·mol−1) were 1.46 × 105(1) and 8.59 × 106(2) and one binding site was formed. The synchronous spectroscopy suggested that tryptophan residues were placed in BSA. It was also found that the two complexes exhibited greater antimicrobial activity than enrofloxacin at given concentrations.

Synthesis, Characterization, DNA-Binding and Antiproliferative Activity of Nd(III) Complexes With N-(Nitrogen Heterocyclic) Norcantharidin Acylamide Acid

Three novel complexes [Nd(L)(NO3)(H2O)2]·NO3·2H2O (HL1 = N-pyrimidine norcantharidin acylamide acid, C12H13N3O4; HL2 = N-pyridine norcantharidin acylamide acid, C13H14N2O4; HL3 = N-phenyl norcantharidin acylamide acid, C14H15NO4) were synthesized. HL1, HL2 and HL3 are the ligand of complex(1), complex(2) and complex(3), respectively. Their structures were characterized by elemental analysis, conductivity measurement, infrared spectra and thermogravimetric analysis. The DNA-binding properties of the complexes have been investigated by fluorescence spectroscopy and viscosity measurements. The results suggest that the complexes can bind to DNA by partial intercalation. The liner Stern-Volmer quenching constant Ksq values are 3.3(±0.21)(1), 1.7(±0.19)(2) and 0.9(±0.04)(3), respectively. Complex (1) and (2) have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity indicates that complex(1) has strong antiproliferative ability against the SMMC7721 (IC50 = 131.7 ± 23.4 μmol·L−1) and A549 (IC50 = 128.4 ± 19.9 μmol·L−1) cell lines. The inhibition rates of complex(2) (IC50 = 86.3 ± 11.3 μmol·L−1) are much higher than that of NCTD (IC50 = 115.5 ± 9.5 μmol·L−1) and HL2 (111.0 ± 5.7 μmol·L−1) against SMMC7721 cell lines.

Synthesis, characterization and DNA binding of the complexes of rare earth with phenanthroline and demethylcantharate

Three novel rare earth complexes, [Ln2(DCA)2(phen)2](NO3)2·6H2O (Ln(III)=Sm(III)(1), Er(III)(2), Yb(III)(3); DCA2−=demethylcantharate, 7-oxabicyclo[2.2.1] heptane-2,3-dicarboxylate, C8H8O52−; phen=1,10-phenanthroline, C12H8N2) were synthesized. The structures were characterized by elemental analysis, molar conductance, IR and TGA. The results suggested that the structural features of the complexes were: in each DCA2−, one carboxylate group, as bidentate bridging group, connected two rare earth ions; the other carboxylate group, as bidentate chelate group took part in the coordination with rare earth ion. And cyclic ether oxygen of DCA2− and nitrogen atoms of phen took part in the coordination. The probable coordination number was seven. The interaction of the complexes with DNA was studied by UV-spectra, fluorescence spectra and viscosity measurements. Following increasing the concentration of DNA, the UV absorption bands nearby 265 nm of the three complexes appeared hypochromism and red-shift phenomena. And the values of binding constants Kb were 1.89×105 L/mol (1), 3.54×104 L/mol (2) and 3.83×104 L/mol (3). The complexes could quench the fluorescence of EB-DNA system, and the values of equilibrium constants Ksq were 1.72(1), 0.56(2) and 1.09(3). The relative viscosity of DNA steadily decreased with increasing the concentration of complexes. So, we could infer that the complexes may partially insert into DNA. The study of agarose gel electrophoresis showed that the complexes could cleave plasmid DNA, and the process of the reaction was through unclassical redox mechanism.

Synthesis,crystal structures of novel complexes of rare earth with norfloxacin,interaction with DNA and BSA

Three novel rare earth complexes [N(CH3)4][Ln(NF)4]6H2O(Ln=Nd(III)(1), Sm(III)(2), Ho(III)(3)) were synthesized using hydrothermal method from norfloxacin HNF=1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid, C16H18FN3O3), imidazole and rare earth nitrates. The complexes were characterized by elemental analysis, FT-IR, TG-DTG and X-ray single crystal diffraction. Each rare earth ion was eight-coordinated with carboxyl-O atoms and keto-O atoms from norfloxacin. Four of the norfloxacin ions acted as bidentate chelate group took part in the coordination with rare earth ion. The structures of complexes were tetragonal system with space group I41/acd, which were allomerism. The interaction between complex 1 and DNA was studied by electronic absorption spectra and fluorescence spectroscopy. The binding interaction between the complex 1 and bovine serum albumin (BSA) was studied by fluorescence spectroscopy. The complex 1 bound to DNA by the mode of partial intercalation. Complex 1 had a strong ability to quench the fluorescence from BSA. The complex interaction was mainly a static quenching process with BSA together with formation of two binding sites.

Synthesis, DNA-binding and antiproliferative activity of N-(Nitrogen heterocyclic) norcantharidin acylamide acid

Two novel norcantharidin acylamide acids (HL1=N-pyrimidine norcantharidin acylamide acid, C12H13N3O4; HL2=N-pyridine norcantharidin acylamide acid, C13H14N2O4) were synthesized by a reaction of norcantharidin(NCTD) with 2-aminopyrimidine and 2-aminopyridine, respectively. Their structures were characterized by elemental analysis, IR, UV and 1 H NMR. Fluorescence titration and viscosity measurements indicated that HL1, HL2 and HL3 (HL3=N-phenyl norcantharidin acylamide acid, C14H15NO4) can bind calf thymus DNA via partial intercalation. The liner Stern-Volmer quenching constant Ksv values for HL1, HL2 and HL3 were 2.05 × 104 L mol−1, 1.15 × 104 L mol−1 and 8.30×103 L mol−1, respectively. Two compounds containing heterocycle of HL1 and HL2 have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity showed that the compounds had moderate to strong antiproliferative ability against the tested cell lines except of HL3 against the SMMC7721 cell line. The results indicated that the heterocycle attached to the norcantharidin was favorable to antiproliferative activity. This result was consistent with the DNA binding experiment.

Bis(2-amino-3H-benzothia-zolium) bis-(7-oxabicyclo-[2.2.1]heptane-2,3-dicarboxyl-ato)cobaltate(II) hexa-hydrate.

In the crystal structure of the title salt, (C7H7N2S)2[Co(C8H8O5)2]·6H2O, the heterocyclic N atom of the 2-aminobenzothiazole molecule is protonated. The CoII atom is situated on an inversion centre and exhibits a slightly distorted octahedral CoO6 coordination defined by the bridging O atoms of the bicycloheptane unit and four carboxylate O atoms of two symmetry-related and fully deprotonated ligands. The crystal packing is stabilized by N—H⋯O hydrogen bonds between the cations and anions and by O—H⋯O hydrogen bonds including the crystal water molecules.

Tris(1H-imidazole-κN3)(7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxyl­ato-κ3O2,O3,O7)cobalt(II) 3.35-hydrate

In the crystal structure of the title compound, [Co(C8H8O5)(C3H4N2)3]·3.35H2O, the central CoII ion is in a slightly distorted octahedral environment, coordinated by the bridging O atom from the bicyclo[2.2.1]heptane ligand, by two carboxylate O atoms from two different carboxylate groups and by three N atoms from imidazole ligands. Uncoordinated water molecules, some of them disordered, are present in the crystal structure. In the crystal structure, molecules are linked by O—H⋯O, N—H⋯O and O—H⋯N hydrogen-bonding interactions.

exo-4-[(1H-Benzimidazol-2-yl)meth­yl]-10-oxa-4-aza­tricyclo­[5.2.1.02,6]decane-3,5-dione

In the title compound, C16H15N3O3, the dihedral angle between the approximately planar benzimidazolyl group (r.m.s. deviation = 0.010 Å) and the pyrrolidine ring is 78.20 (6)°. The C—C—N bond angle of the bridging CH2 group is 112.14 (16)°. In the crystal, molecules are linked via N—H⋯N hydrogen bonds, forming infinite chains parallel to [101] and [10].

Bis(2-amino-3H-benzothia­zolium) bis­(7-oxabicyclo­[2.2.1]heptane-2,3-di­carbox­yl­ato)manganate(II) hexa­hydrate

In the crystal structure of the title salt, (C7H7N2S)2[Mn(C8H8O5)2]·6H2O, the heterocyclic N atom of the 2-aminobenzothiazole molecule is protonated. The MnII atom (site symmetry ) has a slightly distorted octahedral MnO6 coordination defined by the bridging O atoms of the bicycloheptane unit and four carboxylate O atoms of two symmetry-related and fully deprotonated ligands. The crystal packing is stabilized by N—H⋯O hydrogen bonds between the cations and anions and by O—H⋯O hydrogen bonds including the crystal water molecules.