Remedial Treatment of Corroded Iron Objects by Environmental Aeromonas Isolates.

Using bacteria to transform reactive corrosion products into stable compounds represents an alternative to traditional methods employed in iron conservation. Two environmental Aeromonas strains (CA23 and CU5) were used to transform ferric iron corrosion products (goethite and lepidocrocite) into stable ferrous iron-bearing minerals (vivianite and siderite). A genomic and transcriptomic approach was used to analyze the metabolic traits of these strains and to evaluate their pathogenic potential. Although genes involved in solid-phase iron reduction were identified, key genes present in other environmental iron-reducing species are missing from the genome of CU5. Several pathogenicity factors were identified in the genomes of both strains, but none of these was expressed under iron reduction conditions. Additional in vivo tests showed hemolytic and cytotoxic activities for strain CA23 but not for strain CU5. Both strains were easily inactivated using ethanol and heat. Nonetheless, given a lesser potential for a pathogenic lifestyle, CU5 is the most promising candidate for the development of a bio-based iron conservation method stabilizing iron corrosion. Based on all the results, a prototype treatment was established using archaeological items. On those, the conversion of reactive corrosion products and the formation of a homogenous layer of biogenic iron minerals were achieved. This study shows how naturally occurring microorganisms and their metabolic capabilities can be used to develop bio-inspired solutions to the problem of metal corrosion.IMPORTANCE Microbiology can greatly help in the quest for a sustainable solution to the problem of iron corrosion, which causes important economic losses in a wide range of fields, including the protection of cultural heritage and building materials. Using bacteria to transform reactive and unstable corrosion products into more-stable compounds represents a promising approach. The overall aim of this study was to develop a method for the conservation and restoration of corroded iron items, starting from the isolation of iron-reducing bacteria from natural environments. This resulted in the identification of a suitable candidate (Aeromonas sp. strain CU5) that mediates the formation of desirable minerals at the surfaces of the objects. This led to the proof of concept of an application method on real objects.

Crystallographic Services and Technology Support for Industry.

The activities of CSEM's XRD Application Lab are oriented towards the analytical support of technology and product development in the fields of materials sciences, microtechnology, physics, chemistry, nanotechnology and life sciences. Non-destructive X-ray diffraction methods are used for the structural investigation of materials, components and systems. New developments are made with a focus on in situ techniques to 'watch the action' - structural transformations in dependence of applied external fields such as temperature, humidity, magnetic fields or mechanical stresses.

Crystallographic services and technology support for industry.

The activities of CSEM's XRD Application Lab are oriented towards the analytical support of technology and product development in the fields of materials sciences, microtechnology, physics, chemistry, nanotechnology and life sciences. Non-destructive X-ray diffraction methods are used for the structural investigation of materials, components and systems. New developments are made with a focus on in situ techniques to 'watch the action' - structural transformations in dependence of applied external fields such as temperature, humidity, magnetic fields or mechanical stresses.

Synthesis, structures, redox and photophysical properties of benzodifuran-functionalised pyrene and anthracene fluorophores.

Benzodifuran-functionalised pyrene and anthracene fluorophores 1 and 2 were obtained in reasonable yields. Their single crystal structures, electrochemical, optical absorption, and fluorescence characteristics have been described. They show strong luminescence with high quantum yields of 0.53 for 1 and 0.48 for 2.

Capacitance in carbon pores of 0.7 to 15 nm: a regular pattern.

The study of 28 porous carbons shows that the specific capacitance in the electrolyte (C(2)H(5))(4)NBF(4)/acetonitrile is relatively constant between 0.7 and 15 nm (0.094 ± 0.011 F m(-2)). The increase in pores below 1 nm and the lower values between 1 and 2 nm reported earlier are not observed in the present work.

1,4-Bis(hex-yloxy)-2,5-diiodo-benzene.

The centrosymmetric title compound, C(18)H(28)I(2)O(2), crystallized in the monoclinic space group P2(1)/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosymmetric bromo analogue [Li et al. (2008 ▶). Acta Cryst. E64, o1930] that crystallized in the triclinic space group P. The difference between the two structures lies in the orientation of the two alkyl chains with respect to the C(aromatic)-O bond. In the title compound, the O-C(alk-yl)-C(alk-yl)-C(alk-yl) torsion angle is 55.8 (5)°, while in the bromo analogue this angle is -179.1 (2)°. In the title compound, the C-atoms of the alkyl chain are almost coplanar [maximum deviation of 0.052 (5) Å] and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue, these two mean planes are almost coplanar, making a dihedral angle of 4.1 (2)°. Another difference between the crystal structures of the two compounds is that in the title compound there are no halide⋯halide inter-actions. Instead, symmetry-related mol-ecules are linked via C-H⋯π contacts, forming a two-dimensional network.

Multitopic ligand design: a concept for single-source precursors.

The multitopic ligand O,O'-bisnicotinic acid tetraethylene glycol, L, was designed for the coordination of two distinct types of metal ions. In this work, we describe how the O-donor part of L is used to coordinate to alkaline earth metal ions and that the N-donor atoms of L bind to group 11 elements. This makes L a suitable ligand for the combination of both metal ion types within the same compound. This concept will be exemplified by highlighting the pure Ca(2+) complexes, a Cu(+)-coordination polymer network, as well as the mixed-metal compound, which can be used as a single-source precursor for mixed-metal oxide materials.

Poly[deca-mu(2)-cyanido-dicyanidobis(mu(2)-ethylenediamine)bis(ethylenediamine)tricadmium(II)dicobalt(III)]: a two-dimensional coordination polymer.

The title coordination polymer, [Cd(3)Co(2)(CN)(12)(C(2)H(8)N(2))(4)](n), has an infinite two-dimensional network structure. The asymmetric unit is composed of two crystallographically independent Cd(II) atoms, one of which is located on a twofold rotation axis. There are two independent ethylenediamine (en) ligands, one of which bis-chelates to the Cd atom that sits in a general position, while the other bridges this Cd atom to that sitting on the twofold axis. The Cd atom located on the twofold rotation axis is linked to four equivalent Co(III) atoms via cyanide bridges, while the Cd atom that sits in a general position is connected to three equivalent Co(III) atoms via cyanide bridges. In this way, a series of trinuclear, tetranuclear and pentanuclear macrocycles are linked to form a two-dimensional network structure lying parallel to the bc plane. In the crystal structure, these two-dimensional networks are linked via N-H...N hydrogen bonds involving an en NH(2) H atom and a cyanide N atom, leading to the formation of a three-dimensional structure. This coordination polymer is only the second example involving a cyanometallate where the en ligand is present in both chelating and bridging coordination modes.

Poly[diaqua(mu-4,4'-bipyridine-kappa2N:N')bis(mu-cyanido-kappa2C:N)bis(cyanido-kappaC)nickel(II)copper(II)]: a metal-organic cyanide-bridged framework.

The structure of the title compound, [NiCu(CN)4(C10H8N2)(H2O)2]n or [{Cu(H2O)2}(mu-C10H8N2)(mu-CN)2{Ni(CN)2}]n, was shown to be a metal-organic cyanide-bridged framework, composed essentially of -Cu-4,4'-bpy-Cu-4,4'-bpy-Cu- chains (4,4'-bpy is 4,4'-bipyridine) linked by [Ni(CN)4](2-) anions. Both metal atoms sit on special positions; the Cu(II) atom occupies an inversion center, while the Ni(II) atom of the cyanometallate sits on a twofold axis. The 4,4'-bpy ligand is also situated about a center of symmetry, located at the center of the bridging C-C bond. The scientific impact of this structure lies in the unique manner in which the framework is built up. The arrangement of the -Cu-4,4'-bpy-Cu-4,4'-bpy-Cu- chains, which are mutually perpendicular and non-intersecting, creates large channels running parallel to the c axis. Within these channels, the [Ni(CN)4](2-) anions coordinate to successive Cu(II) atoms, forming zigzag -Cu-N[triple-bond]C-Ni-C[triple-bond]N-Cu- chains. In this manner, a three-dimensional framework structure is constructed. To the authors' knowledge, this arrangement has not been observed in any of the many copper(II)-4,4'-bipyridine framework complexes synthesized to date. The coordination environment of the Cu(II) atom is completed by two water molecules. The framework is further strengthened by O-H...N hydrogen bonds involving the water molecules and the symmetry-equivalent nonbridging cyanide N atoms.

Crystal structures of {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n and {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n [where Lpn = (R)-propane-1,2-di-amine]: two heterometallic chiral cyanide-bridged coordination polymers.

The title compounds, catena-poly[[[bis-[(R)-propane-1,2-di-amine-κ(2) N,N']copper(II)]-µ-cyanido-κ(2) N:C-[tris-(cyanido-κC)(nitroso-κN)iron(III)]-µ-cyanido-κ(2) C:N] monohydrate], {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n , (I), and poly[[hexa-µ-cyanido-κ(12) C:N-hexa-cyanido-κ(6) C-hexa-kis-[(R)-propane-1,2-di-amine-κ(2) N,N']dichromium(III)tricopper(II)] penta-hydrate], {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n , (II) [where Lpn = (R)-propane-1,2-di-amine, C3H10N2], are new chiral cyanide-bridged bimetallic coordination polymers. The asymmetric unit of compound (I) is composed of two independent cation-anion units of {[Cu(Lpn)2][Fe(CN)5)(NO)]} and two water mol-ecules. The Fe(III) atoms have distorted octa-hedral geometries, while the Cu(II) atoms can be considered to be penta-coordinate. In the crystal, however, the units align to form zigzag cyanide-bridged chains propagating along [101]. Hence, the Cu(II) atoms have distorted octa-hedral coordination spheres with extremely long semicoordination Cu-N(cyanido) bridging bonds. The chains are linked by O-H⋯N and N-H⋯N hydrogen bonds, forming two-dimensional networks parallel to (010), and the networks are linked via N-H⋯O and N-H⋯N hydrogen bonds, forming a three-dimensional framework. Compound (II) is a two-dimensional cyanide-bridged coordination polymer. The asymmetric unit is composed of two chiral {[Cu(Lpn)2][Cr(CN)6]}(-) anions bridged by a chiral [Cu(Lpn)2](2+) cation and five water mol-ecules of crystallization. Both the Cr(III) atoms and the central Cu(II) atom have distorted octa-hedral geometries. The coordination spheres of the outer Cu(II) atoms of the asymmetric unit can be considered to be penta-coordinate. In the crystal, these units are bridged by long semicoordination Cu-N(cyanide) bridging bonds forming a two-dimensional network, hence these Cu(II) atoms now have distorted octa-hedral geometries. The networks, which lie parallel to (10-1), are linked via O-H⋯O, O-H⋯N, N-H⋯O and N-H⋯N hydrogen bonds involving all five non-coordinating water mol-ecules, the cyanide N atoms and the NH2 groups of the Lpn ligands, forming a three-dimensional framework.

In situ single-crystal to single-crystal (SCSC) transformation of the one-dimensional polymer catena-poly[[diaqua(sulfato)copper(II)]-µ2-glycine] into the two-dimensional polymer poly[µ2-glycine-µ4-sulfato-copper(II)].

The one-dimensional coordination polymer catena-poly[diaqua(sulfato-κO)copper(II)]-µ2-glycine-κ(2)O:O'], [Cu(SO4)(C2H5NO2)(H2O)2]n, (I), was synthesized by slow evaporation under vacuum of a saturated aqueous equimolar mixture of copper(II) sulfate and glycine. On heating the same blue crystal of this complex to 435 K in an oven, its aspect changed to a very pale blue and crystal structure analysis indicated that it had transformed into the two-dimensional coordination polymer poly[(µ2-glycine-κ(2)O:O')(µ4-sulfato-κ(4)O:O':O'':O'')copper(II)], [Cu(SO4)(C2H5NO2)]n, (II). In (I), the Cu(II) cation has a pentacoordinate square-pyramidal coordination environment. It is coordinated by two water molecules and two O atoms of bridging glycine carboxylate groups in the basal plane, and by a sulfate O atom in the apical position. In complex (II), the Cu(II) cation has an octahedral coordination environment. It is coordinated by four sulfate O atoms, one of which bridges two Cu(II) cations, and two O atoms of bridging glycine carboxylate groups. In the crystal structure of (I), the one-dimensional polymers, extending along [001], are linked via N-H···O, O-H···O and bifurcated N-H···O,O hydrogen bonds, forming a three-dimensional framework. In the crystal structure of (II), the two-dimensional networks are linked via bifurcated N-H···O,O hydrogen bonds involving the sulfate O atoms, forming a three-dimensional framework. In the crystal structures of both compounds, there are C-H···O hydrogen bonds present, which reinforce the three-dimensional frameworks.

Exploratory studies on coordination chemistry of a redox-active bridging ligand: synthesis, properties and solid state structures of the complexes.

The explorative coordination chemistry of the bridging ligand TTF-PPB is presented. Its strong binding ability to Co(II) and then to Ni(II) or Cu(II) in the presence of hexafluoroacetylacetonate (hfac(-)), forming new mono- and dinuclear complexes 1-3, is described. X-ray crystallographic studies have been conducted in the case of the free ligand TTF-PPB as well as its complexes [Co(TTF-PPB)(hfac)(2)] (1) and [Co(hfac)(2)(µ-TTF-PPB)Ni(hfac)(2)] (2). Each metal ion is bonded to two bidentate hfac(-) anions through their oxygen atoms and two nitrogen atoms of the PPB moiety with a distorted octahedral coordination geometry. Specifically, nitrogen donor atoms of TTF-PPB adopt a cis-coordination but not in the equatorial plane, which is quite rare. Electronic absorption, photoinduced intraligand charge transfer ((1)ILCT), and electrochemical behaviour of 1-3 have been investigated. UV-Vis spectroscopy shows very strong bands in the UV region consistent with ligand centred π-π* transitions and an intense broad band in the visible region corresponding to a spin-allowed π-π* (1)ILCT transition. Upon coordination, the (1)ILCT band is bathochromically shifted by 3100, 6100 and 5900 cm(-1) on going from 1 to 3. The electrochemical studies reveal that all of them undergo two reversible oxidation and one reversible reduction processes, ascribed to the successive oxidations of the TTF moiety and the reduction of the PPB unit, respectively.

Synthesis and self-assembly of spin-labile and redox-active manganese(III) complexes.

New amphiphilic and spin-labile Mn(III) complexes based on dianionic N(4)O(2)-hexadentate sal(2)trien or sal(2)bapen ligands, which contain OC(6)H(13), OC(12)H(25), or OC(18)H(37) alkoxy substituents at different positions of the salicylidene unit were prepared (H(2)sal(2)trien = N,N'''-bis(salicylidene)-1,4,7,10-tetraazadecane, H(2)sal(2)bapen = N,N'''-bis(salicylidene)-1,5,8,12-tetraazadodecane). According to electrochemical measurements, these complexes undergo two (quasi)reversible redox processes. Temperature-dependent magnetic measurements revealed a high-spin configuration for all sal(2)trien complexes (S = 2) and gradual spin crossover for sal(2)bapen complexes from high to low spin (S = 1). The chain length strongly influences the spin crossover, as C(18)-functionalization stabilizes the low spin state at much higher temperatures than shorter alkyl chains. Moreover, long alkyl chains allow for spontaneous self-assembly of the molecules, which was investigated in single crystals and in Langmuir-films at the air-water interface. Long alkyl chains (C(12) or C(18)) as well as a mutual syn-orientation of these molecular recognition sites were required for the Langmuir monolayers to be stable.

Heterocyclic amine directed synthesis of metal(II)-oxalates: investigating the magnetic properties of two complete series of chains with S = 5/2 to S = 1/2.

We report here two series of coordination polymer chains: the first being [M(II)(ox)(bnz)(2)](n) (M = Mn 1, Fe 2, Co 3, Ni 4, Cu 5 and Zn 6; ox = oxalate C(2)O(4)(2-); bnz = benzimidazole) and the second [M(II)(ox)(btz)(2)](n) (M = Mn 7, Fe 8, Co 9, Ni 10, Cu 11 and Zn 12; btz = benzotriazole). The first series displays an unusual homometallic [-M(i)-M(ii)-M(ii)-](n) chain topology and the second series is isostructural to [Fe(II)(ox)(btz)(2)](n), originally reported by Jia et al. (Collect. Czech. Chem. Commun., 2002, 67, 1609-1615). These two series allow us to make comparisons between the spin state of each metal and the magnetic coupling interaction within an isostructural series spanning the full range of spin states available in 3d metals and to investigate which models are the best to use in each case. Compound 8 is a single-chain magnet, the behaviour through spin-canting arising from a Dzyaloshinskii-Moriya interaction. Additionally, we have synthesised a two-dimensional coordination polymer {[Zn(II)(bnz)(4)][Zn(II)(2)(ox)(3)]}(n) (13), in which distorted hexagonal [Zn(II)(2)(ox)(3)](n)(2n-) layers are hydrogen bonded by [Zn(II)(bnz)(4)](2+) cations to give an interlayer separation of 12.001(2) Å.

New 3D and chiral 1D CuIICrIII coordination polymers exhibiting ferromagnetism.

The reaction of K3[Cr(CN)6] and the copper(II) bis-diamino complex of the ligand 1,3-diaminopropane (tn) led to the new cyanide-bridged 3D polymer ([(Cu(tn)2)3(Cr(CN)6)][Cr(CN)6]) infinity (1). Crystallographic data for 1: trigonal space group R3, a = b = 15.4908(11), c = 16.7699(13) angstroms, Z = 3, V = 3485.0(4) angstroms3. By the same reaction using trans-cyclohexane-(1R,2R)-diamine [1R,2Rchxn] or trans-cyclohexane-(1S,2S)-diamine [1S,2Schxn] as ligands, the chiral 1D polymers ([Cu(1R,2Rchxn)2]3[Cr(CN)6]2.4.75H2O) infinity (2) and ([Cu(1S,2Schxn)2]3[Cr(CN)6]2.4.25H2O} infinity (3), respectively, were obtained. 2 and 3 are isostructural and crystallize in the triclinic space group P1, with a = 8.5421(6), b = 12.6379(9), c = 16.1571(11) angstroms, alpha = 104.594(5) degrees , beta = 98.425(6) degrees , gamma= 97.440(5) degrees , Z = 1, V = 1644.3(2) angstroms3 for 2, and a = 8.5435(8), b = 12.6309(12), c = 16.1711(17) angstroms, alpha = 104.632 degrees , beta = 98.429(8) degrees , gamma = 97.375(8) degrees , Z = 1, and V = 1645.1(3) angstroms3 for 3. The complexes have been characterized by X-ray crystallography, IR, and magnetic susceptibility measurements. The chirality of 2 and 3 has been confirmed by circular dichroism measurements in the solid state. From the magnetic point of view, 1 shows 3D ferromagnetic ordering at ca. 4K, and 2 shows a weak intrachain ferromagnetic exchange, as a result of magnetic orbital orthogonality between Cr(III) and Cu(II) in the chain, with very long Cu-N(cyano) distances (2.665(5) and 2.671(5) angstroms) due to the long Jahn-Teller axis of the copper(II) ions.