Thione- and selone-containing compounds and their metal complexes show promise as antioxidants, as antithyroid drugs, and for applications in lasers and blue light-emitting diodes. Although Cu(i/ii), Co(ii), Ag(i), and Zn(ii) coordination to thione and selone ligands has been broadly studied and Fe(ii) plays an important role in oxidative damage, very few iron-thione complexes and no iron-selone complexes are reported. Novel Fe(ii)-containing thione and selone complexes of the formulae FeL2Cl2, [FeL2(CH3CN)2](2+), and [FeL4](2+), and {FeL'Cl2}n, (L = N,N'-dimethylimidazole selone (dmise), and thione (dmit); L' = bis(thioimidazolyl)ethane (ebit) and bis(selenoimidazolyl)ethane (ebis)) have been synthesized and characterized. Structures of Fe(dmise)2Cl2, Fe(dmit)2Cl2, [Fe(dmit)4][BF4]2, [Fe(dmise)4][BF4]2, and {Fe(ebit)Cl2}n were determined by X-ray crystallography. All Fe(ii) centers adopt a distorted tetrahedral coordination geometry with Fe-S distances ranging from 2.339(1) to 2.397(1) Å and F-Se distances ranging from 2.453(1) to 2.514(1) Å. Density functional theory optimized structures of FeL2Cl2, [FeL2(CH3CN)2](2+), and [FeL4](2+) are consistent with experimental results and suggest that thiones and selones are π-donor ligands that coordinate through their zwitterionic resonance structures. Thione and selone coordination to Fe(ii) lowers the Fe(ii/iii) reduction potential, with a greater decrease for Fe(ii)-bound dmise than Fe(ii)-bound dmit. Dmit and dmise ligand-based oxidation potentials also significantly increase upon Fe(ii) binding compared, indicating that bound thione and selone ligands will undergo oxidation prior to Fe(ii). The synthesis of these complexes suggests that iron coordination by thione and selone ligands may occur in vivo and may contribute to the protective antioxidant properties of sulfur and selenium.

Hydroxyl radical damage to DNA causes disease, and sulfur and selenium antioxidant coordination to hydroxyl-radical-generating Cu(+) is one mechanism for their observed DNA damage prevention. To determine how copper binding results in antioxidant activity, biologically relevant selone and thione ligands and Cu(+) complexes of the formula [Tpm*Cu(L)](+) [Tpm* = tris(3,5-dimethylpyrazolyl)methane; L = N,N'-dimethylimidazole selone or thione] were treated with H2O2 and the products analyzed by (1)H, (13)C{(1)H}, and (77)Se{(1)H} NMR spectroscopy, mass spectrometry, and X-ray crystallography. Upon H2O2 treatment, selone and thione binding to Cu(+) prevents oxidation to Cu(2+); instead, the chalcogenone ligand is oxidized. Thus, copper coordination by sulfur and selenium compounds can provide targeted sacrificial antioxidant activity.

Exposure to arsenic in food and drinking water has been correlated with adverse developmental outcomes, such as reductions in birth weight and neurological deficits. Additionally, studies have shown that arsenic suppresses sensory neuron formation and skeletal muscle myogenesis, although the reason why arsenic targets both of these cell types in unclear. Thus, P19 mouse embryonic stem cells were used to investigate the mechanisms by which arsenic could inhibit cellular differentiation. P19 cells were exposed to 0, 0.1, or 0.5 μM sodium arsenite and induced to form embryoid bodies over a period of 5 days. The expression of transcription factors necessary to form neural plate border specifier (NPBS) cells, neural crest cells and their progenitors, and myocytes and their progenitors were examined. Early during differentiation, arsenic significantly reduced the transcript and protein expression of Msx1 and Pax3, both needed for NPBS cell formation. Arsenic also significantly reduced the protein expression of Sox 10, needed for neural crest progenitor cell production, by 31-50%, and downregulated the protein and mRNA levels of NeuroD1, needed for neural crest cell differentiation, in a time- and dose-dependent manner. While the overall protein expression of transcription factors in the skeletal muscle lineage was not changed, arsenic did alter their nuclear localization. MyoD nuclear translocation was significantly reduced on days 2-5 between 15 and 70%. At a 10-fold lower concentration, monomethylarsonous acid (MMA III) appeared to be just as potent as inorganic arsenic at reducing the mRNA levels Pax3 (79% vs84%), Sox10 (49% vs 65%), and Msx1 (56% vs 56%). Dimethylarsinous acid (DMA III) also reduced protein and transcript expression, but the changes were less dramatic than those with MMA or arsenite. All three arsenic species reduced the nuclear localization of MyoD and NeuroD1 in a similar manner. The early changes in the differentiation of neural plate border specifier cells may provide a mechanism for arsenic to suppress both neurogenesis and myogenesis.

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Novel tinidazole (tnz) coordination compounds of different geometries were synthesised, whose respective solid-state packing appears to be driven by inter- and intramolecular lone pairπ interactions. The copper(ii) compounds exhibit interesting redox properties originating from both the tnz and the metal ions. These complexes interact with DNA through two distinct ways, namely via electrostatic interactions or/and groove binding, and they can mediate the generation of ROS that damage the biomolecule. Cytotoxic studies revealed an interesting activity of the dinuclear compound [Cu(tnz)2(μ-Cl)Cl]27, which is further more efficient towards cancer cells, compared with normal cells.

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Spin-1/2 antiferromagnetic triangular lattice models are paradigms of geometrical frustration, revealing very different ground states and quantum effects depending on the nature of anisotropies in the model. Due to strong spin orbit coupling and crystal field effects, rare-earth ions can form pseudo-spin-1/2 magnetic moments with anisotropic single-ion and exchange properties. Thus, rare-earth based triangular lattices enable the exploration of this interplay between frustration and anisotropy. Here we study one such case, the rare-earth double vanadate glaserite material K3Er(VO4)2, which is a quasi-2D isosceles triangular antiferromagnet. Our specific heat and neutron powder diffraction data from K3Er(VO4)2 reveal a transition to long range magnetic order at 155 ± 5 mK which accounts for all R ln 2 entropy. The quasi-2D magnetic order leads to anisotropic Warren-like Bragg peak profiles, and is best described by alternating layers of b-axis aligned antiferromagnetism and zero moment layers. Our magnetic susceptibility data reveal that Er 3+ takes on a strong XY single-ion anisotropy in K3Er(VO4)2, leading to vanishing moments when pseudo-spins are oriented along c. Thus, the magnetic structure, when considered from the pseudo-spin point of view comprises alternating layers of b-axis and c-axis aligned antiferromagnetism.