High stability of the radical at the catalytic center of cytochrome c oxidase.

In aerobic organisms, cellular respiration is associated with electron transfer through a respiratory system of membrane-bound complexes. This electron flow is terminated by the reduction of dioxygen to water by respiratory oxidases. Cytochrome c oxidase (CcO) is a widely distributed heme-copper-oxygen reductase (HCO) found in all mitochondria and some bacteria.

Structural, optical and magnetic properties of a new metal-organic Co-based complex.

A mononuclear cobalt(ii) complex [CHN][CoCl(CHN)] (I) was synthesized and structurally characterized. Single crystal X-ray diffraction analysis indicates that monometallic Co(ii) ions acted as coordination nodes in a distorted octahedral geometry, giving rise to a supramolecular architecture. The latter is made up of a ½ unit form composed of an anionic element [CoCl(CHN)] and one 2-amino-4-methylpyrimidinium cation [CHN].

Above room temperature spin crossover in mononuclear iron(II) complexes featuring pyridyl-benzimidazole bidentate ligands adorned with aliphatic chains.

Two bidentate ligands (L1 = 1-pentyl-2-(pyridin-2-yl)-1-benzimidazole and L2 = 1-heptyl-2-(pyridin-2-yl)-1-benzimidazole) were employed for the synthesis of five mononuclear Fe(II) coordination compounds 1-5 containing perchlorate, tetrafluoroborate and triflate counterions. Single-crystal X-ray diffraction analysis confirmed the expected molecular structures of all the reported compounds, revealing a moderately distorted octahedral geometry of {FeN} coordination chromophores. All five compounds exhibit thermal spin crossover with temperatures allocated above 400 K.

Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(II) complex ions.

Four novel Co(II) coordination compounds 1-4 of the general formula [Co(L)][Co(NCY)]·CHCN (where L are tridentate ligands L1 = 2,6-bis(1-hexyl-1-benzimidazol-2-yl)pyridine for 1 and 2; L2 = 2,6-bis(1-octyl-1-benzimidazol-2-yl)pyridine for 3; L3 = 2,6-bis(1-dodecyl-1-benzimidazol-2-yl)pyridine for 4, Y = O for 1, 3, and 4 and Y = S for 2; = 0 for 1 and 3, = 0.5 for 2 and = 2 for 4) were prepared and characterised. The molecular structures of all four compounds consist of the hexacoordinate complex cation [Co(L)] and tetracoordinate complex anion [Co(NCY)], with distorted octahedral and tetrahedral symmetry of coordination polyhedra, respectively.

Comprehensive Exploration of Optics and Magnetism in a Hydrothermally Synthesized Nickel(II) Complex.

The hydrothermal reaction of 2-MeIm (2-MeIm: 2-methylimidazole) with nickel sulfate hexahydrate in methanol afforded a mononuclear complex formulated as [Ni(SO)(2-MeIm)(HO)]·CHOH (1). The title compound was described by X-ray single-crystal diffraction, thermal assessment, IR, and UV-vis spectroscopy. The crystal structure of is composed of segregated [Ni(SO)(2-MeIm)(HO)] neutral entities and a solvent methanol molecule.

Influence of the phonon-bottleneck effect and low-energy vibrational modes on the slow spin-phonon relaxation in Kramers-ions-based Cu(II) and Co(II) complexes with 4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole and dicyanamide.

Two new complexes, bis-[4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole-κ,]bis-(dicyanamide-κ)copper(II), [Cu(abpt)(dca)] (1) and bis-[4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole-κ,]bis-(dicyanamide-κ)cobalt(II), [Co(abpt)(dca)] (2), have been prepared and magneto-structurally characterised. Single crystal studies of both complexes have shown that their crystal structures are molecular, in which the central atoms are six-coordinated in the form of a distorted octahedron by two bidentate abpt and two monodentate dca ligands. Even if both complexes have the same composition and crystallize in the same 1̄ space group, they are not isostructural.

An Old Crystallization Technique as a Fast, Facile, and Adaptable Method for Obtaining Single Crystals of Unstable "LiTCNQF" and New Compounds of TCNQ or TCNQF: Syntheses, Crystal Structures, and Magnetic Properties.

Detailed structural information is essential for understanding the properties of TCNQ and TCNQF compounds (TCNQ = 7,7,8,8-tetracyanoquinodimethane; TCNQF = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The ineludible requirement of obtaining crystals of a size and quality sufficient to yield a successful X-ray diffraction analysis has been challenging to satisfy because of the instability of many of these compounds in solution. Crystals of two new complexes of TCNQ, [-M(2)(TCNQ)] [M = Ni (), Zn (); 2ampy = 2-aminomethylpyridine], as well as unstable [Li(TCNQF)(CHCN)]·CHCN (), can be prepared in minutes by a horizontal diffusion technique and can be harvested easily for X-ray structural studies.

The role of redox active copper(II) on antioxidant properties of the flavonoid baicalein: DNA protection under Cu(II)-Fenton reaction and Cu(II)-ascorbate system conditions.

The antioxidant properties of flavonoids are mediated by their functional hydroxyl groups, which are capable of both chelating redox active metals such as iron, copper and scavenging free radicals. In this paper, the antioxidant vs. prooxidant and DNA protecting properties of baicalein and Cu(II)-baicalein complexes were studied under the conditions of the Copper-Fenton reaction and of the Copper-Ascorbate system.

Radical in the Peroxide-Produced F-Type Ferryl Form of Bovine Cytochrome Oxidase.

The reduction of O in respiratory cytochrome oxidases (CcO) is associated with the generation of the transmembrane proton gradient by two mechanisms. In one of them, the proton pumping, two different types of the ferryl intermediates of the catalytic heme -Cu center and forms, participate. Equivalent ferryl states can be also formed by the reaction of the oxidized CcO () with HO.

Annealing-Dependent Morphotropic Phase Boundary in the BiMgTiO-BiZnTiO Perovskite System.

The annealing behavior of (1-x)BiMg0.5Ti0.5O3−xBiZn0.

Novel Lanthanide(III) Porphyrin-Based Metal-Organic Frameworks: Structure, Gas Adsorption, and Magnetic Properties.

The present work focuses on the hydrothermal synthesis and properties of porous coordination polymers of metal-porphyrin framework (MPF) type, namely, {[Pr(HTPPS)]·11HO} (), {[Eu/Sm(HTPPS)]·HO·16HO} (), and {[Ce(HTPPS)]·11HO} () (HTPPS = 4,4',4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrakisbenzenesulfonate(4-)). The compounds were characterized using several analytical techniques: infrared spectroscopy, thermogravimetric measurements, elemental analysis, gas adsorption measurements, and single-crystal structure analysis (SXRD). The results of SXRD revealed a three-dimensional open porous framework containing crossing cavities propagating along all crystallographic axes.

3d-4f magnetic exchange interactions and anisotropy in a series of heterobimetallic vanadium(IV)-lanthanide(III) Schiff base complexes.

A series of heterobimetallic Ln-V compounds [Ln(VO)L(NO)(HO)] (Ln = Gd(1), Tb(2), Dy(3), and Er(4)) assembled by a Schiff base ligand (HL = ,'-bis(1-hydroxy-2-benzylidene-6-methoxy)-1,7-diamino-4-azaheptane) were prepared and studied with experimental and theoretical methods. The single-crystal X-ray analysis revealed the change of the coordination number from 10 found in 1-3 to 9 confirmed in 4. The DC magnetic data were fit with several Hamiltonians to extract the exchange and anisotropy parameters of complexes 1-4.

Modulation of the electron-proton coupling at cytochrome a by the ligation of the oxidized catalytic center in bovine cytochrome c oxidase.

Cytochrome a was suggested as the key redox center in the proton pumping process of bovine cytochrome c oxidase (CcO). Recent studies showed that both the structure of heme a and its immediate vicinity are sensitive to the ligation and the redox state of the distant catalytic center composed of iron of cytochrome a (Fe) and copper (Cu). Here, the influence of the ligation at the oxidized Fe-Cu center on the electron-proton coupling at heme a was examined in the wide pH range (6.

The Structural and Magnetic Properties of Fe and Co Complexes with 2-(furan-2-yl)-5-pyridin-2-yl-1,3,4-oxadiazole.

Two novel coordination compounds containing heterocyclic bidentate ,-donor ligand 2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (fpo) were synthesized. A general formula for compounds originating from perchlorates of iron, cobalt, and fpo can be written as: [M(fpo)(HO)](ClO) (M = Fe(II) for () Co(II) for ()). The characterization of compounds was performed by general physico-chemical methods-elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) in case of organics, and single crystal X-ray diffraction (sXRD).

Stabilization of Pancake Bonding in (TCNQ) Dimers in the Radical-Anionic Salt (N-CH-2-NH-5Cl-Py)(TCNQ)(CHCN) Solvate and Antiferromagnetism Induction.

We report a new antiferromagnetic radical-anion salt (RAS) formed from 7,7,8,8-tetracyanquinonedimethane (TCNQ) anion and 2-amino-5-chloro-pyridine cation with the composition of (N-CH-2-NH-5Cl-Py)(TCNQ)(CHCN). The crystallographic data indicates the formation of (TCNQ) radical-anion π-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π-dimers characterize with strong π-stacking "pancake" interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions.

1D coordination polymer (OPD)CoSO showing SMM behaviour and multiple relaxation modes.

A novel one-dimensional Co coordination polymer (OPD)CoSO was formed from alternating tetrahedral sulphate anions, Co centers and molecules of 1,2-phenylenediamine (OPD). The thermal stability of the structure was confirmed up to ∼230 °C using thermogravimetry and non-ambient powder X-ray diffraction in air. The distorted pseudo-octahedral coordination sphere of Co ions promotes strong magnetic anisotropy.

Correlating Bridging Ligand with Properties of Ligand-Templated [MnX] Clusters (X = Br, Cl, H, MeO).

Polynuclear manganese compounds have garnered interest as mimics and models of the water oxidizing complex (WOC) in photosystem II and as single molecule magnets. Molecular systems in which composition can be correlated to physical phenomena, such as magnetic exchange interactions, remain few primarily because of synthetic limitations. Here, we report the synthesis of a family of trimanganese(II) complexes of the type MnXL (X = Cl, H, and MeO) where L is a tris(β-diketiminate) cyclophane.

Antiferromagnetic ordering in MnF(salen).

Antiferromagnetic order at [Formula: see text] K has been identified in Mn(III)F(salen), salen  =  H14C16N2O2, an S  =  2 linear-chain system. Using single crystals, specific heat studies performed in magnetic fields up to 9 T revealed the presence of a field-independent cusp at the same temperature where (1)H NMR studies conducted at 42 MHz observed dramatic changes in the spin-lattice relaxation time, T 1, and in the linewidths. Low-field (less than 0.

A family of tri- and dimetallic pyridine dicarboxamide cryptates: unusual O,N,O-coordination and facile access to secondary coordination sphere hydrogen bonding interactions.

A series of tri- and dimetallic metal complexes of pyridine dicarboxamide cryptates are reported in which changes to the base and metal source result in diverse structure types. Addition of strong bases, such as KH or KN(SiMe3)2, followed by divalent metal halides allows direct access to trinuclear complexes in which each metal center is coordinated by a dianionic N,N,N-chelate of each arm. These complexes bind a guest K(+) cation within the central cavity in a trigonal planar coordination environment.

Preorganized assembly of three iron(II) or manganese(II) β-diketiminate complexes using a cyclophane ligand.

A trinucleating cyclophane bearing three β-diketimine arms, and the corresponding iron(II) and manganese(II) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of μ(3), μ, and terminal coordination modes are observed for the halide donors.