Hybrid Cu-Containing Compounds Based on Lacunary Strandberg Anions: Synthesis under Mild Conditions, Crystal Structure, and Magnetic Properties.

A one-pot reaction of a copper source (metallic powder Cu0 or Cu2+ salts) and bpy (bpy = 2,2'-bipyridine) in the presence of (NH4)2HPO4 and (NH4)6Mo7O24·4H2O yields heterometallic hybrid compounds of the general type {[Cu(bpy)n(H2O)m]p[P2MoxOy]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P2Mo5O23]6- but also its unprecedented bi- and trilacunary derivatives [P2Mo3O18]8- and [P2Mo2O15]8-. The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different CuII complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1-3 indicate rather strong antiferromagnetic metal-metal exchange interactions. Compound 1 exhibits field-induced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.

Crystal structure of bis-(µ-N-hy-droxy-picolin-amid-ato)bis-[bis-(N-hy-droxy-picolinamide)-sodium].

The title compound, [Na2(C6H5N2O2)2(C6H6N2O2)4], is a centrosymmetric coordination dimer based on the sodium(I) salt of N-hy-droxy-picolinamide. The mol-ecule has an {Na2O6(µ-O)2} core with two bridging carbonyl O atoms and two hydroxamate O atoms of two mono-deprotonated residues of N-hy-droxy-picolinamide, while two neutral N-hy-droxy-picolinamide mol-ecules are coordinated in a monodentate manner to each sodium ion via the carbonyl O atoms [the Na-O distances range from 2.3044 (2) to 2.3716 (2) Å]. The penta-coordinated sodium ion exhibits a distorted trigonal-pyramidal coordination polyhedron. In the crystal, the coordination dimers are linked into chains along the c axis via N-H⋯O and N-H⋯N hydrogen bonds; the chains are linked into a two-dimensional framework parallel to (100) via weak C-H⋯O and π-π stacking inter-actions.

Crystal structure of bis-(bis-{µ3-3-methyl-3-[(4-nitro-2-oxido-benzyl-idene)amino]-propane-1,3-diolato}tris-[chlorido-(dimethyl sulfoxide)-iron(III)]) dimethyl sulfoxide hepta-solvate dihydrate.

The title compound, [Fe3(C11H11N2O5)2Cl3(C2H6OS)3]2·7C2H6OS·2H2O, was isolated accidentally from an Fe0-NiCl2·6H2O-H3L-TEA-DMSO system [where H3L is the product of the condensation between p-nitro-salicyl-aldehyde and 2-amino-2-methyl-propane-1,3-diol and dimethyl sulfoxide (DMSO), and TEA is triethylamine]. The structure is based on a trinuclear {Fe3(µ-O)4} core, with an angular arrangement of the FeIII ions that can be explained by the geometrical restrictions of two bulky ligands, each coordinating to all of the metal cations.

Crystal structure of tetra-kis-[µ2-2-(di-methyl-amino)-ethano-lato-κ(3) N,O:O]di-µ3-hydroxido-di-thio-cyanato-κ(2) N-dichromium(III)dilead(II) di-thio-cyanate aceto-nitrile monosolvate.

The tetra-nuclear complex cation of the title compound, [Cr2Pb2(NCS)2(OH)2(C4H10NO)4](SCN)2·CH3CN, lies on an inversion centre. The main structural feature of the cation is a distorted seco-norcubane Pb2Cr2O6 cage with a central four-membered Cr2O2 ring. The Cr(III) ion is coordinated in a distorted octa-hedron, which involves two N atoms of one bidentate ligand and one thio-cyanate anion, two µ2-O atoms of 2-(di-methyl-amino)-ethano-late ligands and two µ3-O atoms of hydroxide ions. The coordination geometry of the Pb(II) ion is a distorted disphenoid, which involves one N atom, two µ2-O atoms and one µ3-O atom. In addition, weak Pb⋯S inter-actions involving the coordinating and non-coordinating thio-cyanate anions are observed. In the crystal, the complex cations are linked through the thio-cyanate anions via the Pb⋯S inter-actions and O-H⋯N hydrogen bonds into chains along the c axis. The chains are further linked together via S⋯S contacts. The contribution of the disordered solvent aceto-nitrile mol-ecule was removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] procedure in PLATON. The solvent is included in the reported mol-ecular formula, weight and density.

Crystal structure of bis-(ethyl-enedi-thio)-tetra-thia-fulvalenium µ2-acetato-bis-[tri-bromido-rhenate(III)] 1,1,2-tri-chloro-ethane hemisolvate.

The asymmetric unit of the title salt, (C10H8S8)[Re2Br6(CH3COO)]·0.5C2H3Cl3, contains one bis-(ethyl-enedi-thio)-tetra-thia-fulvalene (ET) radical cation, one µ2-acetato-bis-[tri-bromido-rhenate(III)] anion and a 1,1,2-tri-chloro-ethane mol-ecule with half-occupancy disordered about a twofold rotation axis. The tetra-thia-fulvalene fragment adopts an almost planar configuration typical of the ET radical cation. The C atoms of both ethyl-enedi-thio fragments in the cation are disordered over two orientations with occupancy factors 0.65:0.35 and 0.77:0.23. In the anion, six Br atoms and a µ2-acetate ligand form a strongly distorted cubic O2Br6 coordination polyhedron around the Re2 dinuclear centre. In the crystal, centrosymmetrically related ET cations and Re2O2Br6 anions are linked into dimers by π-π stacking inter-actions [centroid-to-centroid distance = 3.826 (8) Å] and by pairs of additional Re⋯Br contacts [3.131 (3) Å], respectively. The dimers are further packed into a three-dimensional network by non-directional inter-ionic electrostatic forces and by C-H⋯Br and C-H⋯S hydrogen bonds. The disordered 1,1,2-tri-chloro-ethane mol-ecules occupy solvent-accessible channels along the b axis.

Crystal structure of N-hy-droxy-picolinamide monohydrate.

The crystal structure of the title compound, C6H6N2O2·H2O, consists of N-hy-droxy-picolinamide and water mol-ecules connected through O-H⋯O and N-H⋯N hydrogen bonds. The O-H⋯O inter-actions and π-π stacking inter-actions between the pyridine rings [centroid-centroid distance = 3.427 (1) Å] organize the components into columns extending along the b axis and the N-H⋯N hydrogen bonds link these columns into a two-dimensional framework parallel to (100). The N-hy-droxy-picolinamide mol-ecule adopts a strongly flattened conformation and only the O-H group H atom deviates significantly from the mol-ecule best plane. The dihedral angle between the hydroxamic group and the pyridine ring is 5.6 (2)°. The conformation about the hydroxamic group C-N bond is Z and that about the C-C bond between the pyridine and hydroxamic groups is E.

A self-assembled octanuclear complex bearing the uncommon close-packed {Fe4Mn4(µ4-O)4(µ-O)4} molecular core.

A one-pot open-air reaction of manganese powder with iron(ii) chloride in DMF solution of the Schiff base (H2L) formed in situ from salicylaldehyde and hydroxylamine hydrochloride yields the heterometallic complex [Fe4(µ4-O)4Mn4(L)8(DMF)4]·2DMF (). Single crystal X-ray analysis shows that its molecular structure is based on the octanuclear core {Fe4Mn4(µ4-O)4(µ-O)4} with a quite rare molecular structure type {M8(µ4-X)4(µ-X)4}, where the central cube-like iron motif is modified with four terminal manganese fragments, the whole core being presented as the {Fe4(µ4-O)4} + 4{Mn(µ-O)} combination. Using the data from the Cambridge Structural Database (CSD), an analysis of the octanuclear structures with similar central {M4(µ4-X)4} fragments was performed. The hierarchical order of molecular structure types with the general formula M8Xn for such compounds was proposed and the topological features as well as the factors that influence the molecular type formation are discussed. Variable-temperature (1.8-300 K) magnetic susceptibility measurements reveal an antiferromagnetic coupling among the magnetic centres in .

Ionization and tautomerism of methyl fluorescein and related dyes.

The protolytic equilibrium of methyl ether of fluorescein is studied in water, aqueous ethanol, and in other solvents. The constants of the two-step dissociation are determined by spectrophotometry. In water, the fractions of the zwitterionic, quinonoid, and lactonic tautomes are correspondingly 11%, 6%, and 83%, as deduced from the UV-visible spectra. Corresponding study of the ionization of the methyl ether ester of fluorescein, fluorescein ethyl ester, and sulfonefluorescein allows testing the correction of the attribution of the microscopic dissociation constants of methoxy fluorescein. The results of nuclear magnetic resonance and infrared spectroscopy, as well as the X-ray analysis confirm the predomination of the lactonic structure of the molecular species in solid state and in DMSO. Contrary to it, the spectroscopic studies in both hydrogen-donor bond (HDB) and non-HBD solvents confirm that the presence of lactonic monoanion is atypical for the dye under study and, with high probability, also for the mother compound fluorescein.

Direct synthesis of a {Co6(III)Fe6(III)} dodecanuclear complex, revealing an unprecedented molecular structure type.

A novel heterometallic Co6Fe6 Schiff base complex, possessing an unprecedented {M12(µ-X)22} branched structure (according to the search via the Cambridge Structural Database), has been prepared using the "direct synthesis" approach and characterized by single crystal X-ray diffraction and magnetometry.

Crystal structure of {2-[({2-[(2-amino-eth-yl)amino]-eth-yl}imino)-meth-yl]pheno-lato}aqua-copper(II) bromide.

In the mononuclear copper(II) title complex, [Cu(C11H16N3O)(H2O)]Br, the Cu(II) atom is coordinated by one O and three N atoms of the Schiff base ligand that forms together with one water mol-ecule a slightly distorted [CuN3O2] square-pyramidal polyhedron. The deviation of the Cu(II) atom from the mean equatorial plane is 0.182 (2) Å. The equatorial plane is nearly coplanar to the aromatic ring of the ligand [angle between planes = 10.4 (1)°], and the water molecule is situated in the apical site. All coordinating atoms (except the imine nitro-gen) and the bromide ion contribute to the formation of the N-H⋯Br, O-H⋯Br and O-H⋯O hydrogen bonds, which link mol-ecules into chains along [01-1].

Tetra-kis(µ3-2-{[1,1-bis-(hy-droxy-meth-yl)-2-oxidoeth-yl]imino-meth-yl}-6-nitro-pheno-lato)tetra-copper(II).

The title cluster, [Cu4(C11H12N2O6)4], was obtained from the Cu(0)-FeCl2·4H2O-H4 L-Et3N-DMF reaction system (in air), where H4 L is 2-hy-droxy-methyl-2{[(2-hy-droxy-3-nitro-phen-yl)methyl-idene]amino}-propane-1,3-diol and DMF is di-methyl-formamide. The asymmetric unit consists of one Cu(2+) ion and one dianionic ligand; a -4 symmetry element generates the cluster, which contains a {Cu4O4} cubane-like core. The metal ion has an elongated square-based pyramidal CuNO4 coordination geometry with the N atom in a basal site. An intra-molecular O-H⋯O hydrogen bond is observed. The solvent mol-ecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155], which indicated a solvent cavity of volume 3131 Å(3) containing approximately 749 electrons. These solvent molecules are not considered in the given chemical formula.

Magnetic, high-field EPR studies and catalytic activity of Schiff base tetranuclear CuII2FeIII2 complexes obtained by direct synthesis.

Two novel heterometallic complexes [Cu2Fe2(HL(1))2(H2L(1))2]·10DMSO (1) and [Cu2Fe2(HL(2))2(H2L(2))2]·2DMF (2) have been prepared using the open-air reaction of copper powder, iron(II) chloride and DMSO (1) or DMF (2) solutions of the polydentate Schiff base (H4L(1), 1; H4L(2), 2) formed in situ from salicylaldehyde (1) or 5-bromo-salicylaldehyde (2) and tris(hydroxymethyl)aminomethane. Crystallographic analysis revealed that both compounds are based on the centrosymmetric tetranuclear core {Cu(II)2Fe(III)2(µ-O)6} where metal centres are joined by µ-O bridges from the deprotonated ligands forming a nonlinear chain-like arrangement. Variable-temperature (1.8-300 K) magnetic susceptibility measurements of 1 and 2 showed a decrease of the effective magnetic moment value at low temperature, indicative of antiferromagnetic coupling (JCu-Fe/hc = -10.2 cm(-1), JFe-Fe/hc = -10.5 cm(-1) in 1, JCu-Fe/hc = -10.5 cm(-1), JFe-Fe/hc = -8.93 cm(-1) in 2) between the magnetic centres in both compounds. They reveal an exceptionally high catalytic activity in the oxidation of cyclohexane with hydrogen peroxide under mild conditions, with the best observed yield/TON combined values of 36%/596 and 44%/1.1 × 10(3) for 1 and 2, respectively.

catena-Poly[[manganese(III)-bis-{µ-2-[(2-hy-droxy-eth-yl)imino-meth-yl]-6-meth-oxy-phenolato-κ(3) O (1),N:O (2);κ(3) O (2):N,O (1)}] iodide].

In the title one-dimensional coordination polymer, {[Mn(C10H12NO3)2]I} n , the potentially tetra-dentate (O,O,O,N) 2-[(2-hy-droxy-eth-yl)imino-meth-yl]-6-meth-oxy-phenol (H2 L) ligands are mono-deprotonated (as HL (-)) and coordinated by the metal ions in a tridentate chelate-bridging fashion [2.0111112]. The Mn(III) atom possesses a distorted trans-MnO4N2 octa-hedral coordination environment. The bridging ligands lead to [010]-chain polymeric cations {[Mn(HL)2](+)} n in the crystal. The charge-balancing iodide ions are disordered over two sites in a 0.690 (2):0.310 (2) ratio and a weak O-H⋯I hydrogen bond occurs. The crystal studied was found to be a racemic twin.

Entropy versus aromaticity in the conformational dynamics of aromatic rings.

Comparison of the results of Car-Parrinello molecular dynamics simulations of isolated benzene, pyrimidine and 1,2,4-triazine molecules reveals that the unusually low population of planar geometry of the benzene ring is caused by entropy effects despite its high aromaticity. The decrease in symmetry of the molecule results in smaller changes in entropy and Gibbs free energy due to out-of-plane deformations of the ring, leading to an increase in the population of planar geometry of the ring. This leads to differences in the topology of potential energy and Gibbs free energy surfaces.

Bis(2-hy-droxy-imino-methyl-6-meth-oxy-phenolato-κ(2)N,O(1))copper(II).

In the title compound, [Cu(C(8)H(8)NO(3))(2)], the nearly planar mol-ecule (r.m.s. deviation = 0.037 Å) is centrosymmetric with the Cu(II) atom lying on an inversion center. The Cu(II) atom is tetra-coordinated, displaying a slightly distorted square-planar geometry. The main deviation from the ideal geometry is seen in the differences in the Cu-O [1.8833 (10) Å] and Cu-N [1.9405 (13) Å] bond lengths, while angular deviations are less than 3°. Intra-molecular O-H⋯O and inter-molecular Csp(2)-H⋯O hydrogen bonds form S(5) and R(2) (2)(8) ring motifs, respectively. The latter inter-action results in chains of mol-ecules along [100].

Hexa-kis-(dimethyl-formamide-κO)manganese(II) (dimethyl-formamide-κO)pentakis(-thio-cyanato--κN)chromate(III).

The title compound, [Mn(C(3)H(7)NO)(6)][Cr(NCS)(5)(C(3)H(7)NO)], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes based on Reineckes anion using manganese powder, Reineckes salt and 1-(2-hy-droxy-eth-yl)tetra-zole as starting materials. The crystal structure of the complex consists of an [Mn(dmf)(6)](2+) cation and a [Cr(NCS)(5)(dmf)](2-) anion (dmf = dimethyl-formamide). The Mn(II) and Cr(III) atoms show a slightly distorted octa-hedral MnO(6) and CrN(5)O coordination geometries with adjacent angles in the range 85.29 (13)-95.96 (14)°.

Tris(2,2'-bipyridine-κN,N')cobalt(III) tris-(oxalato-κO,O)ferrate(III) mono-hydrate.

The title compound, [Co(C(10)H(8)N(2))(3)][Fe(C(2)O(4))(3)]·H(2)O, con-sists of two discrete tris-(chelate) metal ions (Co(III)N(6) and Fe(III)O(6) chromophores) and a water mol-ecule. The structure is highly symmetrical; the Co(III) and Fe(III) ions occupy positions with site symmetry 3.2. The coordination polyhedra of the metal atoms have a nearly octa-hedral geometry with noticeable trigonal distortions. The Co-N and Fe-O bond lengths are equal by symmetry, viz. 1.981 (2) and 1.998 (4) Å, respectively. The cations and anions are arranged alternately along their threefold rotation axes parallel to [001], forming chains that are packed in a hexa-gonal manner. The water mol-ecules occupy voids between the chains. The crystal under investigation was an inversion twin.

Aromaticity in heterocyclic analogues of benzene: comprehensive analysis of structural aspects, electron delocalization and magnetic characteristics.

The degree of aromaticity of six-membered monoheterocycles with IV-VI group heteroatoms (C(6)H(5)X, where X = SiH, GeH, N, P, As, O(+), S(+), Se(+)) was analyzed using the results of ab initio calculations at the MP2/cc-pvtz level. Values of common aromaticity indices including those based on electronic delocalization properties, structural-dynamic features and magnetic properties all indicate high aromaticity of all considered heterocycles. A decrease in aromaticity is observed with increasing atomic number of the heteroatom, except in the case of the pyrylium cation. However, not all types of indices or even different indices within the same type correlate well among each other. Ring currents have been obtained at the HF/cc-pvdz level using the ipsocentric formulation. Ring current maps indicate that in the case of cationic heterocycles the ring current persists in all molecules under consideration. The different conclusions reached depending on the type of index used are a manifestation of the fact that when not dealing with hydrocarbons, aromaticity is ill-defined. One should always express explicitly which property of the molecules is considered to establish a degree of "aromaticity".

Hexa-kis-(dimethyl-formamide-κO)manganese(II) µ-oxido-bis-[trichlorido-ferrate(III)].

The title compound, [Mn(C(3)H(7)NO)(6)][Fe(2)Cl(6)O], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes with Schiff base ligands using manganese powder and FeCl(3)·6H(2)O as starting materials. In the [Fe(2)OCl(6)](2-) anion, the O atom and the Fe atom occupy positions with site symmetry [Formula: see text] and 3, respectively, resulting in a linear Fe-O-Fe angle and a staggered conformation. The octa-hedrally surrounded cation (site symmetry [Formula: see text]) and the [Fe(2)Cl(6)O](2-) anion are alternately stacked along [001].