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Developing a laboratory scale or pilot scale chemical process into industrial scale is not trivial. The direct conversion of CO2 to methanol, and concomitant production of hydrogen from water electrolysis on large scale, are no exception. However, when successful, there are certain benefits to this process over the conventional process for producing methanol, both economic and environmental. In this article, we highlight some aspects that are unique to the process of converting pure CO2 to methanol. Starting from pure CO2 and a separate pure source of H2, rather than a mixture of CO, CO2, and H2 as is the case with syngas, simplifies the chemistry, and therefore also changes the reaction and purification processes from conventional methanol producing industrial plants. At the core of the advantages is that the reaction impurities are essentially limited to only water and dissolved CO2 in the crude methanol. In this paper we focus on several aspects of the process that direct conversion of CO2 to methanol enjoys over existing methods from conventional syngas. In particular, we discuss processes for removing CO2 from a methanol synthesis intermediate product stream by way of a stripper unit in an overhead stream of a distillation column, as well as aspects of a split tower design for the distillation column with an integrated vapo-condenser and optionally also featuring mechanical vapor re-compression. Lastly, we highlight some differences in reactor design for the present system over those used in conventional plants.

The quasicrystalline structures of alloys with nominal compositions of Al72Ni13.4Co14.6 and Al72.3Ni7.8Co19.8 were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. For catalytic application, the solids were leached with an alkaline NaOH solution and tested at 373 K with two model reactions under atmospheric pressure: hydrogenation of crotonaldehyde and acetonitrile. The catalytic activities of these leached alloys were compared to that of a Raney nickel reference catalyst. Catalysts prepared from quasicrystals showed high catalytic activities and high selectivities towards butanal (in crotonaldehyde hydrogenation) and ethylamine (in acetonitrile hydrogenation).

A series of isostructural dimeric manganese complexes of the type [(Me(4)dtne)Mn(2)(mu-O)(2)(mu-R)](2+)(X(-))(2) have been prepared and characterized. The dimanganese cores of these complexes are rigidly held together by the hexadentate ligand Me(4)dtne (Me(4)dtne = 1,2-bis(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethane). Molecular structures for the entire series have been obtained by X-ray diffraction measurements, of which complexes 2 (R = (-)O(2)BPh), 3 (R = (-)O(2)C-PROXYL), 4 (R = (-)O(2)C-TEMPO), and 5 (R = (-)O(2)BPhNIT) are reported here (HO(2)C-PROXYL = 3-carboxy-2,2,5,5-tetramethylpyrrolidin-1-yloxy; HO(2)C-TEMPO = 4-carboxy-2,2,6,6-tetramethylpiperidin-1-yloxy; and HO(2)BPhNIT = 2-(4-(dihydroxyboranyl)-phenyl)-4,4,5,5-tetramethyl-3-oxyimidazolidin-1-oxide). The structures of 1 (R = (-)OAc) and 6 (R = (-)O(2)CPhNIT) have been reported previously (HO(2)CPhNIT = 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-3-oxyimidazolidin-1-oxide). All complexes exhibit several redox states, which have been investigated by electrochemistry. Complexes 1, 3, 4, and 6 contain a mixed-valent Mn(III)Mn(IV) core with an isolated magnetic ground state of S = 1/2. The exchange coupling between the manganese ions is strong throughout the series (J approximately -130 +/- 10 cm(-)(1), H = -2JS(1)S(2)). The radical complexes 3, 4, and 6 exhibit, in addition, long-range exchange interaction (6.9, 7.7, and 8.8 A, respectively) between the organic radical and the dimanganese core. The intramolecular anisotropic coupling was determined from cw-EPR line shape analyses at S-, X-, and Q-band frequencies and from the intensity of half-field signals detected in normal- and parallel-mode (J(d,)(z)() = -120 x 10(-)(4), -105 x 10(-)(4), and -140 x 10(-)(4) cm(-)(1), for 3, 4, and 6 respectively). Distance information was obtained for the dimanganese core and the organic radicals from these values by using a three-spin dipole model and local spin contributions for the manganese ions.

Several iron(III) complexes with N-methylimidazole (N-MeIm) as the ligand have been synthesized by using N-MeIm as the solvent. Under anaerobic conditions, [Fe(N-MeIm)(6)](ClO(4))(3) (1) reacts with stoichiometric amounts of water in N-MeIm to afford the (mu-oxo)diiron(III) complex, [Fe(2)(mu-O)(N-MeIm)(10)](ClO(4))(4) (3). Exposure of a solution of 3 in N-MeIm to stoichiometric and excess CO(2) gives rise to the (mu-oxo)(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-HCO(2))(N-MeIm)(8)](ClO(4))(3) (4) and the methyl carbonate complex [Fe(2)(mu-O)(mu-CH(3)OCO(2))(N-MeIm)(8)](ClO(4))(3) (5), respectively. Formation of the formato-bridged complex 4 upon fixation of CO(2) by 3 in N-MeIm is unprecedentated. Methyl transfer from N-MeIm to a bicarbonato-bridged (mu-oxo)diiron(III) intermediate appears to give rise to 5. Complex 3 is a good starting material for the synthesis of (mu-oxo)mono(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-RCO(2))(N-MeIm)(8)](ClO(4))(3) (where R = H (4), CH(3) (6), or C(6)H(5) (7)); addition of the respective carboxylate ligand in stoichiometric amount to a solution of 3 in N-MeIm affords these complexes in high yields. Attempts to add a third bridge to complexes 4, 6, and 7 to form the (mu-oxo)bis(mu-carboxylato)diiron(III) species result in the isolation of the previously known triiron(III) mu-eta(3)-oxo clusters [[Fe(mu-RCO(2))(2)(N-MeIm)](3)O](ClO(4)) (8). The structures of 3, 4, 6, and 7 allow one, for the first time, to inspect the various features of the [Fe(2)(mu-O)(mu-RCO(2))](3+) moiety with no strain from the ligand framework.

As part of our attempts to prepare FeIII complexes with “tunable” spin states, we have synthesized three novel six-coordinate FeIII complexes containing both carboxamido nitrogen (Namido) and phenolato oxygen (Ophen) donors in their ligand framework. Since it has already been shown that carboxamido nitrogen donors usually stabilize FeIII in a low spin configuration, while phenolato oxygens tend to stabilize FeIII in a high spin state, we have incorporated both donor groups in our designed ligands. The syntheses and structures of FeIII complexes with either one or two Namido and Ophen donors are reported in this paper. The properties of these complexes have been compared with the properties of analogous FeIII complexes. The competing effects of Namido and Ophen on the spin state of the FeIII center are discussed in terms of the stabilities of the overall complexes. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

In its deprotonated form, the ligand N,N′-bis[2-(2-pyridyl)methyl]pyridine-2,6-dicarboxamide (MePy3PH2, where the Hs represent the dissociable amide nitrogens) coordinates to Cu(II) as one strand of a short double helix. The crystal structure of the title complex, bis-(MePy3P)dicopper(II) [Cu2(MePy3P)2], has been determined. The binuclear structure of [Cu2(MePy3P)2] is in contrast to the monomeric Cu(II) complex [Cu(Py3P)] in which the ligand N,N′-bis[2-(2-pyridyl)ethyl]pyridine-2,6-dicarboxamide (Py3PH2) differs from MePy3PH2 by only a single methylene linker. The helical structure of [Cu2(MePy3P)2] has now been added to the rapidly growing number of spontaneously forming helical assemblies, for which crystal structures have been determined.

The small organic molecule pyridine-2,6-dicarboxamide, although known in the literature for some time, exhibits interesting and previously unexplored intermolecular and intramolecular hydrogen bonding both in solid state and in solution. With the aid of X-ray crystallography and variable-temperature NMR spectroscopy, we here demonstrate the presence of a very strong hydrogen bonding network for this molecule both in condensed state and solution. Furthermore, a novel extended hydrogen bonding graph-set has been derived for this molecule in crystalline state. Comparison of pyridine-2,6-dicarboxamide with 1,3-benzenedicarboxamide, where the intramolecular hydrogen bonding to the pyridine ring in the former has been removed, yields a different intermolecular hydrogen bonded structure in the solid state. A new graph-set has been determined for the extended structure of 1,3-benzenedicarboxamide in the solid state. In solution, 1,3-benzenedicarboxamide is shown to maintain a hydrogen bonding pattern that is weaker than that observed with pyridine-2,6-dicarboxamide. Replacement of one hydrogen on each carboxamide nitrogen of pyridine-2,6-dicarboxamide by a methyl group also alters the extended structure to a significant extent. In N , N ′-dimethyl-2,6-pyridinedicarboxamide, the three-dimensional hydrogen bonding pattern observed with pyridine-2,6-dicarboxamide all but collapses to one-dimensional chains.

As part of our continuing effort to develop the chemistry of iron(III) complexes of ligands that employ carboxamido nitrogens to bind the metal center, we have synthesized the designed ligand N,N′-bis(2-hydroxyphenyl)pyridine-2,6-dicarboxamide (POPYH4, Hs are dissociable phenolic and carboxamido hydrogens). Reactions of the completely deprotonated POPY4− with certain iron(III) starting materials in DMF afford pentagonal bipyramidal complexes of the type [Fe(POPY)X2]n− (X=1-MeIm, SCN−), in which the pentadentate POPY4− ligand occupies the equatorial plane. When smaller amounts of base are used, the partially deprotonated POPYH2 2− ligand gives rise to the tetrahedral bis complex [Fe(POPYH2)2]− in which only the phenolic oxygens of the ligand are bound to iron(III). With [Fe2OCl6]2−, one obtains [Fe(POPYH2)(Cl)]2O, a new species that contains a (μ-oxo)diiron(III) core. Here also, POPYH2 2− employs the phenolic oxygens to bind iron and acts as a bidentate ligand. The structures of these complexes have been determined by X-ray crystallography. The conditions for interconversions among the four complexes have also been elucidated. Both [Fe(POPY)X2]n− complexes with coordinated carboxamido nitrogens are stable in air and in aqueous solution. The redox properties of these species indicate that ligated carboxamido nitrogens provide enhanced stability to iron(III) centers.

Although coordination of carboxamido nitrogen to Fe(III) center has been assumed to be improbable, research work during the past few years has demonstrated that Fe(III) complexes with ligated carboxamido nitrogens can be readily synthesized. The Fe(III)–Namido bond distances lie in the range of 1.8–2.2 A in the various low spin and high spin Fe(III) complexes. These complexes are stable in aqueous media and their redox parameters indicate that the carboxamido nitrogens provide significant stability to the Fe(III) center.

Two nonmacrocyclic ligands with pyridine and carboxamide nitrogens as donors readily form bis complexes of the type [FeIIIL2]+ in which the Fe(III) centers exhibit preference for coordination to carboxamido nitrogens over pyridine nitrogens. These Fe(III) complexes with deprotonated carboxamido nitrogens are very stable in water.

International audience; Two alloys of composition Al59Cu25.5Fe12.4B3 and Al71Cu9.7Fe8.7Cr10.6 were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The latter forms a mixture of imperfect icosahedral phase and cubic phase upon rapid solidification from the liquid state. After heat treatment, this alloy transforms into a decagonal quasicrystalline phase. Both alloys can be used as catalysts precursors and transformed into active metallic phases after alkali leaching with a NaOH solution. These catalysts were used for hydrogen production by steam reforming of methanol between 473 and 773 K. The catalytic activities of these treated alloys were compared to that of a reference Cu/ZnO/Al2O3 catalyst. Quasicrystal derived catalysts showed a high catalytic activity for the production of hydrogen.

Three iron complexes of a pentadentate ligand N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide (PaPy(3)H, H is the dissociable amide proton) have been synthesized. All three species, namely, two nitrosyls [(PaPy(3))Fe(NO)](ClO(4))(2) (2) and [(PaPy(3))Fe(NO)](ClO(4)) (3) and one nitro complex [(PaPy(3))Fe(NO(2))](ClO(4)) (4), have been structurally characterized. These complexes provide the opportunity to compare the structural and spectral properties of a set of isostructural [Fe-NO](6,7) complexes (2 and 3, respectively) and an analogous genuine Fe(III) complex with an "innocent" sixth ligand ([(PaPy(3))Fe(NO(2))](ClO(4)), 4). The most striking difference in the structural features of 2 and 3 is the Fe-N-O angle (Fe-N-O = 173.1(2) degrees in the case of 2 and 141.29(15) degrees in the case of 3). The clean (1)H NMR spectrum of 2 in CD(3)CN reveals its S = 0 ground state and confirms its [Fe-NO](6) configuration. The binding of NO at the non-heme iron center in 2 is completely reversible and the bound NO is photolabile. Mossbauer data, electron paramagnetic resonance signal at g approximately 2.00, and variable temperature magnetic susceptibility measurements indicate the S = (1)/(2) spin state of the [Fe-NO](7) complex 3. Analysis of the spectroscopic data suggests Fe(II)-NO(+) and Fe(II)-NO(*) formulations for 2 and 3, respectively. The bound NO in 3 does not show any photolability. However, in MeCN solution, it reacts rapidly with dioxygen to afford the nitro complex 4, which has also been synthesized independently from [(PaPy(3))Fe(MeCN)](2+) and NO(2)(-). Nucleophilic attack of hydroxide ion to the N atom of the NO ligand in 2 in MeCN in the dark gives rise to 4 in high yield.

In recent years, iron complexes of designed ligands have been synthesized as mimics of the active sites of the various non-heme iron enzymes. The reactions of these model complexes have been studied to establish the mechanisms of the enzymatic reactions as well as the identities of the intermediates involved in the biocatalytic processes. The ultimate goal in these endeavors is to isolate functional mimics that could be employed in biomimetic catalysis under mild conditions. This review provides key references to the burgeoning literature on the results of research performed by various groups in the area of oxygen activation, oxygenation of organic substrates, amide hydrolysis, and other useful chemical transformations. Examples of good structural and functional models have been included along with brief descriptions of the enzymes. The role of the coordination spheres of the iron centers and the nature of the key iron-peroxo and/or hypervalent iron-oxo intermediates have been discussed. Results of the attempted catalysis by the functional model complexes have also been discussed to highlight the challenge involved in bio-inspired catalysis as well as the success of the modeling work completed so far. Keywords: non-heme iron enzymes; model complexes; functional mimics; oxygen activation; oxygenation; epoxidation; catalysis

Eight Cu(II) complexes with the [Cu(dmppy)] moiety (dmppyH(2) = tridentate ligand N,N'-dimethylpyridine-2,6-dicarboxamide; H's are dissociable amide protons) and ligands like pyridine, water, N-methylimidazole, substituted and unsubstituted o-phenanthroline, and bipyridine have been isolated and structurally characterized. The basal angles of these structurally related five-coordinate Cu(II) complexes (and two previously reported ones) correlate well with the EPR hyperfine splitting parameter A( parallel). However, the values of the parameter tau which provides a measure of the degree of square pyramid versus trigonal bipyramid geometry adopted by these complexes do not correlate linearly with the A( parallel) values. It is evident that out-of-plane distortions and ligand strain make calculation of tau inconsistent in certain sets of five-coordinate Cu(II) complexes. Structure-spectroscopy correlation involving tau is not feasible in such cases.

To investigate the relation between common acid-base parameters and blood lactate concentrations and their prognostic importance in sick, ventilated neonates.Two hundred and seventy eight serial simultaneous measurements of arterial acid-base status and blood lactate concentrations were carried out in 75 mechanically ventilated neonates with indwelling arterial catheters (gestational age and birthweight, median (range) -29 (23-40) weeks, and 1340 (550-4080) g, respectively).There were no correlations between arterial blood lactate and pH and base excess within subjects (r = 0.07 and r = -0.06, respectively) and only weakly positive but clinically irrelevant positive correlations between subjects (r = 0.28 and r = 0.27) in this group. Even in those infants who had not received any bicarbonate before their initial measurements (n = 48), there were no correlations between initial blood lactate concentrations and pH (r = 0.27), base excess (r = 0.17), or serum bicarbonate concentrations (r = -0.18). There was no relation between peak lactate concentration (PLC) and base excess (r = 0.16), and only a weak correlation between peak lactate concentration (PLC) and pH (r = 0.28). Negative base excess was an insensitive indicator of raised lactate concentrations. Only two out of 33 (6%) instances of hyperlactataemia (lactate2.5 mmol/l) would have been identified with a base excess-10 mmol/l as a cutoff. Lower cutoff values of base excess or pH performed no better. Raised lactate concentrations were associated with increased mortality at all levels. While six of 53 (11%) infants with a PLC2.5 mmol/l died, this proportion increased to four of 15 (27%) with a PLC between 2.5-5.0 mmol/l, and four of seven (57%) with a PLC5.0 mmol/l. Infants showing little rise or a substantial fall in blood lactate fared better than those with persistently raised values. A clinically important increase in blood lactate preceded the development of clinical markers of deterioration and complications in six infants.Contrary to popular belief, pH or base excess cannot be used as proxy measures for blood lactate concentration, and independent measurement of the latter are needed. Blood lactate concentrations may provide an early warning signal and important prognostic information in ill, ventilated neonates. In this regard, serial measurements of blood lactate are more useful than a single value.