Mononuclear Iron(III) Complex with Unusual Temperature Change of Color and Magneto-Structural Properties: Synthesis, Structure, Magnetization, Multi-frequency ESR and DFT Study

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex is reversible changing from red at...

Investigation of Substitution Reactions Between Zinc(II) Complexes with Different Geometries and N-bonding Nucleophiles

Aims: Investigation of interactions between zinc(II) complexes with different geometrical structures and relevant nitrogen donor nucleophiles at physiological pH. Background: The lack of clear distinction between the therapeutic and toxic doses of platinum drugs is a major challenge for the design of novel non-platinum DNA and protein targeting metal-based anticancer agents. The non-platinum antitumor complexes could be alternatives to platinum-based drugs due to their better characteristics and different mechanism of action. Objective This study could provide more information for the design of future zinc-based anticancer drugs, as well as providing a better understanding of the mechanism of interactions between Zn(II) complexes and nitrogen-donor nucleophiles (important from a medical point of view) and clarifies the changes in geometrical structures of zinc(II) that are referred to structure-reactivity correlation Methods Mole-ratio method and UV-Vis spectroscopic kinetic method were applied in this study. Objective : This study could provide more information for the design of future zinc-based anticancer drugs, as well as providing a better understanding of the mechanism of interactions between Zn(II) complexes and nitrogen-donor nucleophiles (important from a medical point of view) and clarifies the changes in geometrical structures of zinc(II) that are referred to structure-reactivity correlation Methods Mole-ratio method and UV-Vis spectroscopic kinetic method were applied in this study. Result: The results indicated additional coordination of chlorides in the first coordination sphere with changes in coordination geometry and formation of the octahedral complex anion [ZnCl4(en)]2- while an excess of chloride didn’t affect the square-pyramidal structure of [ZnCl2(terpy)]. The substitutions of studied complexes and relevant nucleophiles proceed in two consecutive reaction steps that depend on the nucleophile concentration. Octahedral complex anion [ZnCl4(en)]2- forms rapidly, and all substitution processes of this complex species should be considered. We assume that the first reaction step is accompanied by the dissociation of chloride ligands. Nucleophile 1,2,4-triazole have shown the highest affinity toward [ZnCl2(en)], and rates of both steps are almost the same value, which indicates parallel reactions. Conclusion: The different order of reactivity of relevant N-donor ligands toward [ZnCl2(en)] and [ZnCl2(terpy)] complexes for the first reaction step occurred due to the influence of different geometrical structures of complexes. In contrast, low reaction rates for the second reactions of [ZnCl2(en)] complex with imidazole and pyrazine were a consequence of interconversion between octahedral and tetrahedral structure during substitution processes.

Synthesis and Chemical and Biological Evaluation of a Glycine Tripeptide Chelate of Magnesium

Magnesium (Mg2+) plays a crucial role in over 80% of all metabolic functions. It is becoming increasingly apparent that magnesium deficiency (hypomagnesemia) may play an important role in chronic disease. To counteract magnesium deficiency, there is an unmet clinical need to develop new fully characterized, highly bioavailable, and substantially water-soluble magnesium supplements. To this end, triglycine (HG3), a tripeptide of the amino acid glycine, was chosen as a chelating ligand for magnesium, given its natural occurrence and water solubility, and entropically-driven metal binding. Herein, we discuss the synthesis, chemical and physical characterization, and cellular uptake of a magnesium triglycine chelate (MgG3), an octahedral complex with extraordinary water solubility and improved cellular uptake in CaCo-2 cells than select commonly used magnesium supplements.

Field-induced single-ion magnet based on a quasi-octahedral Co(II) complex with mixed sulfur-oxygen coordination environment

Synthesis and characterization of structure and magnetic properties of the quasi-octahedral complex (pipH2)[Co(TDA)2] 2H2O (I), (pipH22+ = piperazine dication, TDA2-= thiodiacetic anion) are described. X-ray diffraction studies reveal the first...

The Structure and Properties of Fe(II) 1,10-Phenanthroline-Thiobarbiturate

The structure of the mononuclear complex [Fe(Bipy)(H2O)2(Htba)2]∙6H2O (I), where Bipy – 2,2’-dipyridine, H2tba – 2-thiobarbituric acid (C4H4N2O2S), was determined by single crystal X-ray diffraction technique (cif-file CCDC No. 1831367). Crystals I are rhombic: a = 17.4697 (7), b = 11.7738 (4), c = 13.4314 (5) Å, V = 2762.6(2) Å3, space group Pnma, Z = 4. Two nitrogen atoms of the Bipy molecule and two water molecules are located in the equatorial plane of the octahedral complex, and two S-coordinated Htba− ions the axial positions are occupied. The structure is stabilized by N−H∙∙∙O, O−H∙∙∙O, С−H∙∙∙O, C−H∙∙∙S intermolecular hydrogen bonds and π–π interaction between Bipy and Htba−. The compound is characterized by the methods of powder X-ray diffraction, thermal analysis, and IR spectroscopy

fac-Bis(phenoxatellurine) tricarbonyl manganese(I) bromide

The reaction of (CO)5MnBr with phenoxatellurine (PT) provided the octahedral complex fac-(CO)3(PT)2MnBr in which the two PT ligands are situated in cis-position.

Complementarity in Cyclotricatechylene Assemblies: Symmetric Cages Linked within 3D Cubic Hydrogen Bonded Networks

A serendipitous discovery has led to the generation of a family of four compounds in which six components combine to form symmetric metal-cyclotricatechylene (H6ctc) cages. The four compounds, which have the compositions, [Cs((CH3)2CO)6][K4(H6ctc)4(H2O)8][Cs4(H2O)6](PO4)3, [Rb((CH3)2CO)6][Rb2K2(H6ctc)4(H2O)6][Rb4(H2O)6](PO4)3, [Cs((CH3)2CO)6][K4(H6ctc)4(H2O)8]-[Cs(H2O)9](SO4)3 and [Rb((CH3)2CO)6][Rb2K2(H6ctc)4(H2O)6][Rb(H2O)9](SO4)3 possess cubic symmetry that arises from the complementary interactions that govern the assembly of the components. The cage cavities contain water molecules and either one or four large alkali metal ions (either Rb+ or Cs+) which interact with the internal aromatic surfaces of the cage. Each cage is linked to six tetrahedral anions (PO43− or SO42−) through 24 equivalent hydrogen bonds and each anion bridges a pair of cages through eight such hydrogen bonds. An unusual octahedral complex M((CH3)2CO)6+ (M = Rb or Cs), in which the M-C=O link is linear, appears to be a key structural component. A feature of this family of crystalline compounds is the presence of a range of complementary interactions which combine to generate materials that exhibit high crystallographic symmetry.

X-ray Structure Refinement and Vibrational Spectroscopy of Metavauxite FeAl2(PO4)2(OH)2·8H2O

In this paper, we provide a crystal-chemical investigation of metavauxite, ideally FeAl2(PO4)2(OH)2·8H2O, from Llallagua (Bolivia) by using a multi-methodological approach based on EDS microchemical analysis, single crystal X-ray diffraction, and Raman and Fourier transform infrared (FTIR) spectroscopy. Our new diffraction results allowed us to locate all hydrogen atoms from the structure refinements in the monoclinic P21/c space group. Metavauxite structure displays a complex framework consisting of a stacking of [Al(PO4)3(OH)(H2O)2]7− layers linked to isolated [Fe(H2O)6]2+ cationic octahedral complex solely by hydrogen bonding. The hydrogen-bonding scheme was inferred from bond-valence calculations and donor-acceptor distances. Accordingly, strong hydrogen bonds, due to four coordinated H2O molecules, bridge the [Fe(H2O)6]2+ units to the Al/P octahedral/tetrahedral layer. The hydroxyl group, coordinated by two Al atoms, contributes to the intra-layer linkage. FTIR and Raman spectra in the high-frequency region (3700–3200 cm−1) are very similar, and show a complex broad band consisting of several overlapping components due to the H2O molecules connecting the isolated Fe(H2O)6 and the adjacent Al/P octahedral/tetrahedral layers. A sharp peak at 3540 cm−1 is assigned to the stretching mode of the OH group. The patterns collected in the low-frequency region are dominated by the stretching and bending modes of the PO43− group and the metal-oxygen polyhedra.

Crystal chemistry of halurgite, Mg4[B8O13(OH)2]2·7H2O, a microporous heterophylloborate mineral

Three samples of halurgite were re-examined: two from the Chelkar salt dome in the North Caspian Region, Western Kazakhstan (the type locality and including the type specimen), and one from a new locality in the Satimola salt dome located in the same region. The crystal structure of halurgite has been solved for the first time on the specimen from Chelkar with the empirical formula Mg3.94[B8.03O13.03(OH)1.97]2·7.16H2O; refinement began with single-crystal X-ray diffraction data and was subsequently refined on a powder sample using the Rietveld method (Rp= 0.0232,Rwp= 0.0354 andRobs= 0.0558). The idealised crystal chemical formula of halurgite is Mg4[B8O13(OH)2]2·7H2O. The mineral is monoclinic,P2/c,a= 13.201(2),b= 7.5622(10),c= 13.185(2) Å, β = 91.834(14)°,V= 1315.6(4) Å3andZ= 2. The crystal structure is unique. Eight B polyhedra form a fundamental building block [B8O16(OH)2], which is a six-membered borate ring (built by two pairs of B tetrahedra and two B triangles) with two additional triangular BO2(OH) groups. Each [B8O16(OH)2] ring is linked to six adjacent analogous rings to form a [B8O13(OH)2]∞layer. These layers are connectedviaMgO6and Mg(OH)2(H2O)4octahedra into a microporous heteropolyhedral pseudo-framework. The crystal structure of halurgite can also be described in terms of an approach developed for heterophyllosilicates containing three-layerHOHmodules, whereHOHrefers to an octahedral layerOsandwiched between two heteropolyhedral layersH. In halurgite theHOHmodule consists of two heteropolyhedral (BO3triangles + BO4tetrahedra) borateHlayers [B8O13(OH)2]∞and a central interruptedOlayer composed of MgO6octahedra, whereas a more voluminous Mg(OH)2(H2O)4octahedral complex and additional H2O molecules are located betweenHOHmodules. Halurgite and four related synthetic H-free boratesM2Cd3B16O28andM2Ca3B16O28(M= Rb or Cs) can be considered microporous heterophylloborates.