Synthesis and Structure of bis(μ-2-aminopyridine N-oxide)-bis[dichlorocopper(II)]

1 INTRODUCTIONMany complexes of 2-aminopyridine N-oxide (apo) have been characterized by infrared spectra, X-ray powder diffraction spectra, and by magnetic measurements and electronic spectra at liquid nitrogen temperature, but very few of them are their crystal X-ray studies[1~3]. Recently, a number of bridged binuclear copper (II) complexes have been reported, some of which have important potential applications in bioinorganic chemistry and materials[4~6]. Particularly, the complexes …     

Structure and Spectroscopic Characteristics of N,N′-bis(2-Hydroxy-3-methoxyphenylmethylidene)2,6-pyridinediamine

The Schiff base N,N-bis(2-hydroxy-3-methoxyphenylmethylidene)-2,6-pyridinediamine has been synthesized and characterized in the solid state and in solution using X-ray analysis, IR, UV/Vis, and NMR spectroscopy. Crystal data: C₂₁H₁₉N₃O₄, M _r = 377.39, orthorhombic, space group Pnc2, a = 4.9288(8), b = 8.8873(19), c = 20.870(5) Å, V = 914.19(20) ų, Z = 2, R = 0.0387, R _w = 0.0530, 1845 independent reflections, 778 with I > 2(I). There are two intramolecular hydrogen bonds O—H-N between the hydroxyl and imino groups of 2.622(3) Å. The enolimine form is found in the solid state and is also the predominant tautomeric form in solution. Comparison of the title compound with the structurally related N,N-bis(salicylidene)-2,6-pyridinediamine and N,N-bis(salicylidene)-2,3-pyridinediamine is given.     

Synthesis and crystal structure of bis[(μ-κO:κO′-acetato)(μ-κO:κ2O′-acetato)][(η5-Cp)tris(dimethylphosphito-P)cobalt-O,O′,O″]yttrium(III)

The [η⁵-CpCo{P(O)(OMe)₂}₃Y(O₂CCH₃)₂]₂, yttrium(III) complex has been synthesized by the stoichiometric mixture of YCl₃, NaL_OMe and NaAc in a 1:1:2 molecular ratio in dry THF solvent and we have determined the structure by X-ray diffraction. The molecule is a dimeric compound, which consists of one tripodal ligand (L_OMe=CpCo[P(O)(OMe)₂]₃) and two bridging acetato (Ac) ligands on each yttrium atom. The acetate ligands of this complex have two different coordination modes, which are μ-κO:κO′-acetato and μ-κO:κ²O′-acetato bound to each yttrium atom.     

Synthesis and Structure of Di(μ-Ophenoxy)-bis{nitrato-2-[2-(hydroxyethylimino)-methyl]-phenoloimidazolecopper}

The crystal structure of di(-O_phenoxy)-bis{nitrato-2-[2-(hydroxyethylimino)-methyl]-phenoloimid-azolecopper} was determined. The crystals are monoclinic: a = 10.222(2) Å, b = 13.810(3) Å, c = 10.620(2) Å, =103.67(3)°, space group P2₁/n, Z = 2, R = 0.050. The copper atom coordinates the singly deprotonated 2-[2-(hydroxyethylimino)-methyl]-phenol molecule, imidazole, and nitrate ion. The coordination polyhedron of the central atom is an extended tetragonal bipyramid with imine and imidazole nitrogen atoms and phenol and alcohol oxygen atoms lying in its base. One axial vertex of the bipyramid is occupied by the oxygen atom of the nitrato group and the other vertex, by phenol oxygen atom of the neighboring complex joined with the initial complex by the symmetry center. Two bridging phenol oxygen atoms unite the complexes into a centrosymmetrical dimer.     

Theoretical study of spin–orbit coupling and kinetics in spin-forbidden reaction between Ta(NH2)3 and N2O

The activation mechanism of the nitrous oxide (N₂O) with the Ta(NH₂)₃ complex on the singlet and triplet potential energy surfaces has been investigated using the hybrid exchange correlation functional B3LYP. The minimum energy crossing point (MECP) is located by using the methods of Harvey et al. The rate-determining step of the N–O activation reaction is the intersystem crossing from ¹ 2 to ³ 2. The reacting system will change its spin multiplicities from the singlet state to the triplet state near MECP-1, which takes place with a spin crossing barrier of 32.5 kcal mol^?1, and then move on the triplet potential energy surface as the reaction proceeds. Analysis of spin–orbit coupling (SOC) using localized orbitals shows that MECP-1 will produce the significant SOC matrix element, the value of SOC is 272.46 cm^?1, due to the electron shift between two perpendicular π orbitals with the same rotation direction and the contribution from heavy atom Ta. The rate coefficients are calculated using Non-adiabatic Rice-Ramsperger-Kassel-Marcus (RRKM). Results indicate that the coefficients, k(E), are exceedingly high, k(E) > 10¹² s^?1, for energies above the intersystem crossing barrier (32.5 kcal mol^?1); however, in the lower temperature range of 200–600 K, the intersystem crossing is very slow, k(T) < 10^?6 s^?1.     

Synthesis and mesomorphic properties of 4-methoxyphenyl 4′- n -alkoxy-2′,3′,5′,6′-tetrafluorobiphenyl-1-carboxylates

A novel type of 4-methoxyphenyl 4′-n-alkoxy-2′,3′,5′,6′-tetrafluorobiphenyl-1-carboxylates have been synthesized. Textural observations by polarizing microscopy and DSC measurements of the phase transitions show that all of these compounds are thermotropic liquid crystals with only a nematic mesophase. The relationship between the properties and chemical structures of these compounds is discussed.     

Pyridinium tetrakis(nitrato-κ2O,O′)(2,2′:6′,2′′-terpyridine-κ3N)cerate(III) pyridine solvate and bis(methanol-κO)tris(nitrato-κ2O,O′)(2,2′:6′,2′′-terpyridine-κ3N)cerium(III)

The title complexes, (C₅H₆N)[Ce(NO₃)₄(C₁₅H₁₁N₃)]·C₅H₅N or (Hpy)­[Ce(NO₃)₄(terpy)]·py, (I) (py is pyridine, C₅H₅N, and terpy is ter­pyridine, C₁₅H₁₁N₃), and [Ce(NO₃)₃­(C₁₅H₁₁N₃)(CH₄O)₂] or [Ce(NO₃)₃(terpy)(OHCH₃)₂], (II), are 11-coordinate. The coordination polyhedron of the Ce atom in (I) is irregular, while that in (II) can be described as an icosahedron with two vertices replaced by one.     

Synthesis and Structure of the Complex [Mo3(μ3-S)(μ2-S2)3(Et2NCS2)3 +Br-

Tri-₂-disulfido-₃-thiotris(diethyldithiocarbamato)-S,S'-triangle-trimolybdenum bromide [Mo₃(₃-S)(₂-S₂)₃(Et₂NCS₂)₃ ⁺Br^- was obtained and characterized.     

Synthesis and Crystal Structure of[Co3(CO)9(μ3-C)C(O)OCH2]2

The title compound [Co3(CO)9(μ3-C)C(O)OCH2]2 was synthesized by the reaction of [Cl3CC(O)OCH2]2 with Co2(CO)8 at 40～50 ℃. Crystal data: C24H4O22Co6, Mr=997.88, monoclinic, space group P21/n(#14), a=9.330(2), b=15.197(4), c=11.783(4), β=91.16(2)°, V=1670.4(7) 3, Z=2, Dc=1.984 g/cm3, μ(MoKα)=30.01 cm-1, F(000)=972.00, T=293K, final R=0.045, Rw=0.051 for 1936 observed reflections with I＞2σ(I). The structure contains two centrosymmetric dimeric molecules in a unit cell, each of which has two tetrahedral skeletons (CCo3) connected through a C(O)OCH3CH2OC(O) bridge.     

Synthesis and Crystal Structure of Compound [Fe(Phen)_3][(μ-oxo)Fe_2Cl_6]DMF

1 INTRODUCTION Recently polynuclear iron (Ⅲ) clusters have attracted considerable attention in bioinorganic chemistry due to their presence in the protein ferritin and the related materical hemosiderin[1, 2]. The binuclear oxo-bridge non-haem iron com- plexes (containing the FeⅢOFeⅢ unit) which provide models for the diiron site in the protein involved in the storage (haemrythrin) and on the reductive activation (methanemonoxygenas， ribonclectidereductas) of dioxygen[3,4]. Also, wel…     

Electrochemical synthesis and spectroscopy of the polymeric form of N,N′-bis(3-methoxysalicylidene)-1,3-propylenediamine

Electrochemical oxidation of N,N′-bis(3-methoxysalicylidene)-1,3-propylenediamine leads to the formation of a conducting polymer on the electrode surface. The diffusion coefficient and activation barrier of the charge transfer in the bulk of the polymer in an electrolyte medium were determined. The Schiff base and its polymeric form in the oxidized and reduced states were characterized by IR, X-ray photoelectron, and electronic absorption spectroscopy. Reversible changes in the polymer structure, accompanying its electrochemical oxidation-reduction, are substantiated.     

Calorimetric study of the reaction between formic acid and N,N,N′,N′-tetramethylethylenediamine from the aspect of thermal energy storage

The attack by formic acid on the nitrogen electron pairs of N,N,N,N-tetramethylethylenediamine leads to the stoichiometric salt or to many other complexes with different molar fractions. Physical and thermodynamic parameters of two adducts, obtained by calorimetric study, are discussed in terms of their use as potential phase change materials in thermal energy storage because of their large heat of fusion between 288 and 333 K.

---

Zusammenfassung Bei der Einwirkung von Ameisensäure auf die Elektronenpaare von N,N,N,N-Tetramethylethylendiamin entsteht ein stöchiometrisches Salz oder mehrere andere Komplexe mit unterschiedlichem Molenbruch. Es werden physikalische und thermodynamische Parameter zweier bei der kalorimetrischen Untersuchung erhaltenen Addukte hinsichtlich ihrer Verwendung als potentielle Phasenwechselsubstanzen bei der thermischen Energiespeicherung diskutiert, da sie im Bereich 288–333 K eine große Schmelz-wärme besitzen.

     

Structures of bis(2-thiobarbiturato-O)tetraaquamagnesium and catena-[(μ2-2-thiobarbiturato-O,O)(2-thiobarbiturato-O) bis(μ2-aqua)diaquastrontium] monohydrate

The crystal structures of bis(2-thiobarbiturato-O)tetraaquamagnesium Mg(H₂O)₄(HTBA-O)₂ I and catena-[(μ₂-2-thiobarbiturato-O,O)(2-thiobarbiturato-O)bis(μ₂-aqua)diaquastrontium] monohydrate catena-[Sr(μ₂-H₂O)₂(H₂O)₂(μ₂-HTBA-O,O)(HBTA-O)] _n · nH₂O (II), where H₂TBA is 2-thiobarbituric acid C₄H₄N₂O₂S, have been determined. Crystal data for a=6.7598(2) Å, b = 7.6060(2) Å, c = 8.5797(2) Å, α = 79.822(2)°, β = 76.622(1)°, γ = 69.124(1)°, V = 398.82(2) ų, space group P $\bar 1$ , Z = 1; for II: a = 20.8499(4) Å, b = 19.2649(5) Å, c = 4.14007(9) Å, β = 92.023(2)°, V = 1661.91(7) ų, space group P2₁/n, Z = 4. The Mg²⁺ ion in I is bonded to six O atoms of two HTBA^? ions and four water molecules that form a nearly regular octahedron. Each Sr²⁺ ion in II is coordinated to three oxygen atoms of three HTBA^? ions and six water molecules that form an almost ideal tricapped trigonal prism. These polyhedra share edges to form infinite chains. Intermolecular hydrogen bonds create layered structures of I and II.     

Evaluating the identity and diiron core transformations of a (μ-oxo)diiron(III) complex supported by electron-rich tris(pyridyl-2-methyl)amine ligands

The composition of a (μ-oxo)diiron(III) complex coordinated by tris[(3,5-dimethyl-4-methoxy)pyridyl-2-methyl]amine (R(3)TPA) ligands was investigated. Characterization using a variety of spectroscopic methods and X-ray crystallography indicated that the reaction of iron(III) perchlorate, sodium hydroxide, and R(3)TPA affords [Fe(2)(μ-O)(μ-OH)(R(3)TPA)(2)](ClO(4))(3) (2) rather than the previously reported species [Fe(2)(μ-O)(OH)(H(2)O)(R(3)TPA)(2)](ClO(4))(3) (1). Facile conversion of the (μ-oxo)(μ-hydroxo)diiron(III) core of 2 to the (μ-oxo)(hydroxo)(aqua)diiron(III) core of 1 occurs in the presence of water and at low temperature. When 2 is exposed to wet acetonitrile at room temperature, the CH(3)CN adduct is hydrolyzed to CH(3)COO(-), which forms the compound [Fe(2)(μ-O)(μ-CH(3)COO)(R(3)TPA)(2)](ClO(4))(3) (10). The identity of 10 was confirmed by comparison of its spectroscopic properties with those of an independently prepared sample. To evaluate whether or not 1 and 2 are capable of generating the diiron(IV) species [Fe(2)(μ-O)(OH)(O)(R(3)TPA)(2)](3+) (4), which has previously been generated as a synthetic model for high-valent diiron protein oxygenated intermediates, studies were performed to investigate their reactivity with hydrogen peroxide. Because 2 reacts rapidly with hydrogen peroxide in CH(3)CN but not in CH(3)CN/H(2)O, conditions that favor conversion to 1, complex 1 is not a likely precursor to 4. Compound 4 also forms in the reaction of 2 with H(2)O(2) in solvents lacking a nitrile, suggesting that hydrolysis of CH(3)CN is not involved in the H(2)O(2) activation reaction. These findings shed light on the formation of several diiron complexes of electron-rich R(3)TPA ligands and elaborate on conditions required to generate synthetic models of diiron(IV) protein intermediates with this ligand framework.     

Conformational and structural study of N-nicotinyl N′, N″-bis(diisobutyl amine)phosphoric triamide

Single crystals of C5H4NC(O)NHP(O)[N(i-C4H9)2]2 were prepared and investigated by X-ray crystallography. Interestingly, four symmetrically independent conformers were detected in the structure of this compound by X-ray crystallography. The greatest difference in these conformers was different torsion angles. In all conformers, the phosphoryl and carbonyl groups showed anti-configurations, and the two terminal CH3 groups of each alkyl chain in amine parts have different spatial orientations due to their connection to a prochiral carbon atom. The diastereotopic protons of every CH2 moiety in amine groups also have different spatial orientations. Every conformer forms a centrosymmetric dimer with its own symmetrically generated analog via a hydrogen bond. The first conformer connects to others (A, B, and C) via electrostatic interactions and forms a tetramer. All hydrogen bonds and electrostatic interactions result in the formation of a three-dimensional polymeric network in the crystalline lattice of compound. To find the most stable conformer, density functional theory (DFT) calculations were performed. The computationally optimized geometric parameters are in good agreement with the experimental results. According to DFT calculations, B is the most stable conformer with energy of ?987714.07 kcal/mol. In all conformers the electron density of HOMO is localized on P=O and C=O oxygen atoms and some parts of amine groups, while LUMO is localized on the nicotinamide part of the molecule.