Magnetism of dinuclear benzoato cobalt(II) complexes modeled by a general bilinear exchange

Synthesis, structural determination, in vitro and in silico biological evaluation of divalent or trivalent cobalt complexes with indomethacin

The interaction of cobalt chloride with the non-steroidal anti-inflammatory drug indomethacin (Hindo) led to the formation of the polymeric complex [Co(indo-O)2(H2O)2(μ-Cl)]n·n(MeOH·H2O) bearing one chlorido bridge between the cobalt atoms. The presence of the nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 1H-imidazole (Himi) resulted in the isolation of complexes [Co2(μ-indo-O,O')2(indo-O)2(bipy)2(μ-H2O)]·3.3MeOH, [Co(indo-O,O')2(bipyam)]·0.9MeOH·0.2H2O, [Co(indo-O,O')2(phen)] (4) and [Co(indo-O)2(Himi)2] (5), respectively, where the indomethacin ligands were coordinated in diverse manners. The study of the affinity of the complexes for calf-thymus DNA revealed their intercalation between the DNA-bases. The binding of the complexes to albumins was also examined and the corresponding binding constants and binding subdomain were determined. The free radical scavenging activity of the compounds was evaluated towards 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Molecular modeling calculations may usually provide a molecular basis for the understanding of both the impairment of DNA by its binding with the studied complexes and the ability of these compounds to transportation through serum albumin proteins. This study can provide information for the elucidation of the mechanism of action of the compounds in a molecular level.

Slow magnetic relaxation in a μ1,1'-azido cobalt(ii) methylquinoline chain complex

A [Co(N3)2(mqu)] complex with a 1D chain architecture (mqu - 4-methylquinoline) displays the paramagnetic behaviour with a slight exchange interaction of antiferromagnetic nature among Co(ii) centres. It shows slow magnetic relaxation with three distinct modes. The relaxation time strongly depends upon the applied external field. The slowest relaxation time refers to the low-frequency mode τLF = 1.6(2) s at BDC = 0.8 T and T = 1.9 K.

Structural and magnetic properties of Co(II) complexes with tridentate ONO pincer-type ligands

Pincer type ligand 2,6-pyridinedimethanol was used as a useful tool in the preparation of the Co(II) pseudoctahedral complex together with 3,5-dinitrobenzoate counteranion. New complex of the composition [Co(pydm)2](3,5-dnbz)2(pydm = 2,6-pyridinedimethanol, and 3,5-dnbz = 3,5-dinitrobenzoate anion) has been prepared and characterized. Its XRD structure revealed pseudooctahedral {CoN2O4} chromophore around the cobalt atom with Co-N distances significantly shorter (Co-Nav = 2.038 Ǻ) in comparison to the Co-O ones (Co-Oav = 2.142 Ǻ), which was probably the reason of its relatively high zero-field splitting parameter (D/hc = 43.6 cm-1). Positive value of the D parameter causes slow relaxation process typical for Co(II) SMM behavior. The 3,5-dinitrobenzoate counteranions are strongly bonded to the [Co(pydm)2] cation via rather strong hydrogen bonds (O∙∙∙Oav = 2.568 Ǻ) forming “quasi molecular” units. Solid state structure allowed different π-π stacking interactions of neighboring “molecular” unit aromatic rings probally leading to observation of the additional relaxation mode.

Effective Anisotropic Interactions in Spin Pairs Containing High-Spin Ions with Large Zero-Field Splitting

Analytic and numeric derivations are made of the effective exchange and dipolar magnetic interactions between spin pairs containing S = 3/2 ions, such as high-spin Co(II), S = 5/2 ions, such as high-spin Fe(III) ions, experiencing zero-field splittings much larger than the interion interactions, or J = 15/2 ions such as Dy(III) with crystal-field splittings much larger than the interion interaction. These formulas allow for a simpler analysis of the magnetic properties of dimers containing high-spin ions.

Impact of nuclearity and topology on the single molecule magnet behaviour of hexaazatrinaphtylene-based cobalt complexes

A hexaazatrinaphtylene-based transition metal complex that exhibits single molecule magnet behaviour is reported herein. This study reveals the influence of both nuclearity and topology on the magnetic properties of hexaazatrinaphtylene-based complexes.

Inducing magnetic communication in caged dinuclear Co(ii) systems

Magnetic interactions were probed for a series of mono and tri atomic bridged dinuclear Co(ii) azacryptand complexes. Magneto-structural correlations were established usingab initiocalculations.

Single-molecule magnetism in a pentacoordinate cobalt(II) complex supported by an antenna ligand

Pentacoordinate complex [CoL(3)Cl2] with a tridentate antenna-like ligand L(3) forms a dimer held by short π-π stacking with head-to-head contacts at 3.4 Å. The direct-current (dc) magnetic susceptibility and magnetization data confirm weak ferromagnetic interaction and a large-magnetic anisotropy, D/hc = 150 cm(-1) and E/hc = 11.6 cm(-1). The system shows superparamagnetic behavior at low temperature that depends upon the applied magnetic field. At Bdc = 0.2 T, a low-frequency peak at the out-of-phase susceptibility is seen (ν ∼ 0.3 Hz), whereas the onset of the second peak appears at ν > 1500 Hz, indicating the existence of two slow relaxation processes.