Synthesis, crystal structure, spectroscopic properties and potential biological activities of salicylate‒neocuproine ternary copper(II) complexes.

Mixed ligand copper(II) complexes containing derivatives of salicylic acid and heterocyclic ligands with nitrogen donor atoms have been the subject of various studies and reviews. In this paper, synthesis and characterization of the ternary copper(II) complexes of neocuproine (2,9-dimethyl-1,10-phenanthroline, Neo) and salicylate ligands (Sal) are reported. In addition, the crystal structures of ([Cu(H2O)(5-Cl-Sal)(Neo)] (1), [Cu(µ-Sal)(Neo)]2 (2), Cu2(µ-5-Cl-Sal)(5-Cl-HSal)2(Neo)2]·EtOH (3)) were determined. In order to compare structural and biological properties of the prepared complexes, spectroscopic and biological studies were performed. Results of X-ray diffraction show that prepared complexes form three types of crystal structures in a given system: monomeric, dimeric and dinuclear complex. The preliminary study on the DNA cleavage activity has shown that the complexes under study behave as the chemical nucleases in the presence of added hydrogen peroxide with slight differences in the activity (1 > 2 > 3). The complexes 1 and 2 exhibited nuclease activity itself indicating the interaction of complexes with the DNA. It has been proposed that the enhanced destructive effect of the complexes 1 and 2 on the DNA is a result of two possible mechanisms of action: (i) the conversion of closed circular DNA (form I) to the nicked DNA (form II) caused by the copper complex itself and (ii) damage of DNA by Reactive Oxygen Species (ROS)-products of the interaction of copper with hydrogen peroxide by means of Fenton reaction (hydroxyl radicals). Thus the biological activity of the prepared Cu(II) complexes containing derivatives of salicylic acid and phenanthroline molecules is substantiated by two independent mechanisms. While derivatives of salicylic acids in the coordination sphere of copper complexes are responsible for radical-scavenging activity (predominantly towards superoxide radical anion), the presence of chelating ligand 2,9-dimethyl-1,10-phenanthroline significantly enhances capability of Cu(II) complexes binding to DNA via intercalation.

trans-Tetra-aqua-bis[3-(3-pyrid-yl)acrylato-κN]cobalt(II).

The asymmetric unit of the title compound, [Co(C(8)H(6)NO(2))(2)(H(2)O)(4)], contains one half-mol-ecule. The Co(II) atom lies on an inversion centre and is coordinated by two N atoms of the pyridine rings of 3-(3-pyrid-yl)acrylate anions and four O atoms of water mol-ecules in a distorted octa-hedral coordination geometry. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules, forming a three-dimensional network.

catena-Poly[[bis-[2-(2,3-dimethyl-anilino)benzoato-κO]cadmium(II)]-di-µ-3-pyridylmethanol-κN:O;κO:N].

In the crystal structure of the title compound, [Cd(C(15)H(14)NO(2))(2)(C(6)H(7)NO)(2)](n), the Cd atom displays a distorted octa-hedral geometry, including two pyridine N atoms and two hydroxyl O from four symmetry-related 3-pyridylmethanol (3-pyme) ligands and two carboxylate O atoms from mefenamate [2-(2,3-dimethyl-anilino)benzoate] anions. The Cd atoms are connected via the bridging 3-pyme ligands into chains, that extend in the a-axis direction. The Cd atom is located on a center of inversion, whereas the 3-pyme ligands and the mefenamate anions occupy general positions.

trans-Diaqua-bis(ethyl-enediamine-κN,N')copper(II) bis[3-(3-pyrid-yl)propionate] dihydrate.

The asymmetric unit of the title complex, [Cu(C(2)H(8)N(2))(2)(H(2)O)(2)](C(8)H(8)NO(2))(2)·2H(2)O, contains one anion, one half-cation and one water mol-ecule. The Cu(II) atom in the [Cu(en)(2)(H(2)O)(2)](2+) cation (en is ethyl-enediamine) lies on an inversion centre. The four N atoms of the en ligands in the equatorial plane around the Cu(II) atom form a slightly distorted square-planar arrangement, while the slightly distorted Jahn-Teller octa-hedral coordination is completed by two water O atoms in axial positions. In the crystal structure, intra- and inter-molecular N-H⋯O and O-H⋯O hydrogen bonds form a three-dimensional network.

Bis(chloro-acetato)-κO,O';κO-methanol-κO-bis-(2-methyl-furo[3,2-c]pyridine-κN)copper(II).

In the title compound, [Cu(C(2)H(2)ClO(2))(2)(C(8)H(7)NO)(2)(CH(4)O)], the Cu(2+) ion has a highly distorted square-bipyramidal (4 + 1 + 1) coordination environment and is bonded to three carboxyl-ate O atoms of two chloro-acetate anions (monodentate and asymmetrically bidentate), two pyridine N atoms of 2-methyl-furo[3,2-c]pyridine and one methanol O atom. There is an intra-molecular O-H⋯O hydrogen bond. Inter-molecular C-H⋯O hydrogen bonds result in the formation of a three-dimensional network and π-π stacking inter-actions [3.44-3.83 Å] are observed between symmetry-related rings of 2-methyl-furo[3,2-c]pyridine. Further inter-actions in the crystal structure are a short Cl⋯Cl inter-action [3.384 (2)Å] and C-H⋯π inter-actions between 2-methyl-furo[3,2-c]pyridine rings.

Di-µ-nicotinato-κN:O;κO:N-bis-[aqua-(ethyl-enediamine-κN,N')(nicotinato-κN)cadmium(II)] dihydrate.

The dinuclear mol-ecule of the title compound, [Cd(2)(C(6)H(4)NO(2))(4)(C(2)H(8)N(2))(2)(H(2)O)(2)]·2H(2)O, lies on an inversion centre and forms 12-membered (CdNC(3)O)(2) metallacycles with the two Cd(2+) ions bridged by two nicotinate ligands. Both Cd(2+) ions display coordination polyhedra with a distorted octa-hedral geometry that includes two pyridine N atoms from bridging and terminal nicotinate anions, two amine N atoms from chelating ethylene-diamine ligands, carboxylate O atoms from bridging nicotinate anions and water O atoms. Inter-molecular O-H⋯O and N-H⋯O hydrogen bonds result in the formation of a three-dimensional network, and π-π stacking inter-actions are observed between symmetry-related pyridine rings of bridging as well as terminal nicotinate anions (the centroid-centroid distances are 3.59 and 3.69 Å, respectively, and the distances between parallel planes of the stacked pyridine rings are 3.53 and 3.43 Å, respectively). The two methylene groups of the ethylene-diamine ligand are disordered over two positions; the site occupancy factors are ca 0.8 and 0.2.

Monoclinic polymorph of trans-tetra-aquabis-[(4-pyridylsulfanyl)-acetato-κN]cobalt(II).

The crystal structure of the title compound, [Co(C(7)H(6)NO(2)S)(2)(H(2)O)(4)], is a polymorph of the structure first reported by Du, Zhao & Wang [(2004). Dalton Trans, pp. 2065-2072]. The asymmetric unit of the title compound contains one half-mol-ecule; the Co(II) atom lies on an inversion centre in a distorted octa-hedral geometry coordinated by two N atoms of the pyridine rings of the 4-pyridylthio-acetate anions and four O atoms of water mol-ecules. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules, forming a three-dimensional network.