New Spectroelectrochemical Insights into Manganese and Rhenium Bipyridine Complexes as Catalysts for the Electrochemical Reduction of Carbon Dioxide.

This study aimed to demonstrate the behavior of different complexes using IR spectroelectrochemistry (SEC), a technique that combines IR spectroscopy with electrochemistry. Four different Mn and Re catalysts for electrochemical CO reduction were studied in dry acetonitrile. In the case of Mn(apbpy)(CO)Br (apbpy = 4(4-aminophenyl)-2,2'-bipyridine), SEC suggested that a very slow catalytic reduction of CO also occurs in acetonitrile in the absence of proton donors, but at rather negative potentials.

Leucopterin, the white pigment in butterfly wings: structural analysis by PDF fit, FIDEL fit, Rietveld refinement, solid-state NMR and DFT-D.

Leucopterin (CHNO) is the white pigment in the wings of Pieris brassicae butterflies, and other butterflies; it can also be found in wasps and other insects. Its crystal structure and its tautomeric form in the solid state were hitherto unknown. Leucopterin turned out to be a variable hydrate, with 0.

Zwitterionic or Not? Fast and Reliable Structure Determination by Combining Crystal Structure Prediction and Solid-State NMR.

When it comes to crystal structure determination, computational approaches such as Crystal Structure Prediction (CSP) have gained more and more attention since they offer some insight on how atoms and molecules are packed in the solid state, starting from only very basic information without diffraction data. Furthermore, it is well known that the coupling of CSP with solid-state NMR (SSNMR) greatly enhances the performance and the accuracy of the predictive method, leading to the so-called CSP-NMR crystallography (CSP-NMRX). In this paper, we present the successful application of CSP-NMRX to determine the crystal structure of three structural isomers of pyridine dicarboxylic acid, namely quinolinic, dipicolinic and dinicotinic acids, which can be in a zwitterionic form, or not, in the solid state.

Ambiguous structure determination from powder data: four different structural models of 4,11-di-fluoro-quinacridone with similar X-ray powder patterns, fit to the PDF, SSNMR and DFT-D.

Four different structural models, which all fit the same X-ray powder pattern, were obtained in the structure determination of 4,11-di-fluoro-quinacridone (CHNOF) from unindexed X-ray powder data by a global fit. The models differ in their lattice parameters, space groups, , ', molecular packing and hydrogen bond patterns. The molecules form a criss-cross pattern in models A and B, a layer structure built from chains in model C and a criss-cross arrangement of dimers in model D.

Efficient Electrochemical Reduction of CO to Formate in Methanol Solutions by Mn-Functionalized Electrodes in the Presence of Amines.

Carbon cloth electrode modified by covalently attaching a manganese organometallic catalyst is used as cathode for the electrochemical reduction of CO in methanol solutions. Six different industrial amines are employed as co-catalyst in millimolar concentrations to deliver a series of new reactive system. While such absorbents were so far believed to provide a CO reservoir and act as sacrificial proton source, we herein demonstrate that this role can be played by methanol, and that the adduct formed between CO and the amine can act as an effector or inhibitor toward the catalyst, thereby enhancing or reducing the production of formate.

A Review of Mechanical and Chemical Sensors for Automotive Li-Ion Battery Systems.

The electrification of passenger cars is one of the most effective approaches to reduce noxious emissions in urban areas and, if the electricity is produced using renewable sources, to mitigate the global warming. This profound change of paradigm in the transport sector requires the use of Li-ion battery packages as energy storage systems to substitute conventional fossil fuels. An automotive battery package is a complex system that has to respect several constraints: high energy and power densities, long calendar and cycle lives, electrical and thermal safety, crash-worthiness, and recyclability.

Solid-State NMR-Driven Crystal Structure Prediction of Molecular Crystals: The Case of Mebendazole.

Among all possible NMR crystallography approaches for crystal-structure determination, crystal structure prediction - NMR crystallography (CSP-NMRX) has recently turned out to be a powerful method. In the latter, the original procedure exploited solid-state NMR (SSNMR) information during the final steps of the prediction. In particular, it used the comparison of computed and experimental chemical shifts for the selection of the correct crystal packing.

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes.

This work reports two new cationic heteroleptic cyclometalated iridium complexes, containing ether derivatives of di(pyridin-2-yl)methanol. The new ligands are based on dipyridin-2-ylmethane and are designed to obtain ether-based intermediates with extended electronic conjugation by insertion of π system such as phenyl, allyl and ethynyl. Different synthetic strategies were employed to introduce these units, as molecular wires, between the dipyridin-2-ylmethane chelating portion and the terminal N-containing functional group, such as amine and carbamide.

Molecular Catalysts with Intramolecular Re-O Bond for Electrochemical Reduction of Carbon Dioxide.

A new Re bipyridine-type complex, namely, -Re(pmbpy)(CO)Cl (pmbpy = 4-phenyl-6-(2-hydroxy-phenyl)-2,2'-bipyridine), , carrying a single OH moiety as local proton source, has been synthesized, and its electrochemical behavior under Ar and under CO has been characterized. Two isomers of , namely, characterized by the proximity of Cl to OH and , are identified. The interconversion between and is clarified by DFT calculations, which reveal two transition states.

Simultaneous CO capture and metal purification from waste streams using triple-level dynamic combinatorial chemistry.

A reduction in CO emissions is required to mitigate global warming. Post-combustion carbon capture is one of the most developed technologies that has the potential to meet this goal, but its cost prevents its widespread use. A different approach would be to use CO directly as it is captured, before it is stored.

Electronic Effects of Substituents on -M(bpy-R)(CO) (M = Mn, Re) Complexes for Homogeneous CO Electroreduction.

Synthesis and characterization of 14 new 2,2'-bipyridine metal complexes -M(bpy-R)(CO)X (where M = Mn, X = Br or M = Re, X = Cl and R = -CF, -CN, -Ph, -PhOH, -NMe) are reported. The complexes have been characterized by NMR, IR spectroscopy and elemental analysis. Single crystal X-Ray diffraction structures have been solved for Re(dpbpy)(CO)Cl (dpbpy = 4,6-diphenyl-2,2'-bipyridine) and Re(hpbpy)(CO)Cl (hpbpy = 4-(2-hydroxy-phenyl)-6-phenyl-2,2'-bipyridine).

Strontium and Zinc Substitution in β-Tricalcium Phosphate: An X-ray Diffraction, Solid State NMR and ATR-FTIR Study.

β-tricalcium phosphate (β-TCP) is one of the most common bioceramics, widely applied in bone cements and implants. Herein we synthesized β-TCP by solid state reaction in the presence of increasing amounts of two biologically active ions, namely strontium and zinc, in order to clarify the structural modifications induced by ionic substitution. The results of X-ray diffraction analysis indicate that zinc can substitute for calcium into a β-TCP structure up to about 10 at% inducing a reduction of the cell parameters, whereas the substitution occurs up to about 80 at% in the case of strontium, which provokes a linear increase of the lattice constants, and a slight modification into a more symmetric structure.

Electrochemical CO reduction in water at carbon cloth electrodes functionalized with a fac-Mn(apbpy)(CO)Br complex.

The organometallic complex (fac-Mn(apbpy)(CO)3Br) (apbpy = 4-(4-aminophenyl)-2,2'-bipyridine) grafted electrochemically onto carbon cloth serves as an electrocatalyst in the aqueous reduction of CO2 to syngas. A faradaic efficiency of around 60% for CO and 40% for H2 at -1.35 V is achieved together with a productivity rate higher than 870 NlCO h-1 gMn-1 at turnover numbers of up to 33 200 during 10 hours of operation.

Synthesis, structure, and polymorphic transitions of praseodymium(iii) and neodymium(iii) borohydride, Pr(BH) and Nd(BH).

In this work, praseodymium(iii) borohydride, Pr(BH4)3, and an isotopically enriched analogue, Pr(11BD4)3, are prepared by a new route via a solvate complex, Pr(11BD4)3S(CH3)2. Nd(BH4)3 was synthesized using the same method and the structures, polymorphic transformations, and thermal stabilities of these compounds are investigated in detail. α-Pr(BH4)3 and α-Nd(BH4)3 are isostructural with cubic unit cells (Pa3[combining macron]) stable at room temperature (RT) and a unit cell volume per formula unit (V/Z) of 180.

Electrochemical CO Reduction at Glassy Carbon Electrodes Functionalized by Mn and Re Organometallic Complexes.

The catalytic activities towards electrochemical CO reduction of two new rhenium and manganese complexes, namely fac-Mn(apbpy)(CO) Br (1) and fac-Re(apbpy)(CO) Cl (2) (apbpy=4-(4-aminophenyl)-2,2'-bipyridine), in both homogeneous and heterogeneous phases are compared. A glassy carbon electrode (GCE) surface has been functionalized with complexes 1 and 2 by two approaches: a) direct electrochemical oxidation of the amino group with formation of C-N bonds, and b) electrochemical reduction of the corresponding diazonium salts with formation of C-C bonds. The chemically modified GCEs show efficient conversion of CO into CO, with turnover numbers (TONs) about 60 times higher than those of the corresponding catalysts in homogeneous solutions, and in a much shorter time.

Proton in a Confined Space: Structural Studies of H ⊂Crypt-111 Iodide and Some Halogen-Bonded Derivatives.

Experimental observations and modeling data are reported on the solid-state structural features of crypt- 111⋅HI (1) and the three-component co-crystals that 1 forms with α,ω-diiodoperfluoroalkanes 2 a-d. X-ray analyses indicate that, in all five systems and at low temperature, the caged proton is covalently bonded to a single nitrogen atom and is involved in a network of intramolecular hydrogen bonds. In contrast, room-temperature, solid-state N NMR spectroscopy suggests magnetic equivalency of the two N atoms of crypt-111 in both 1 and co-crystals of 1 with diiodoperfluoroalkanes.

Local Proton Source in Electrocatalytic CO Reduction with [Mn(bpy-R)(CO) Br] Complexes.

The electrochemical behavior of fac-[Mn(pdbpy)(CO) Br] (pdbpy=4-phenyl-6-(phenyl-2,6-diol)-2,2'-bipyridine) (1) in acetonitrile under Ar, and its catalytic performances for CO reduction with added water, 2,2,2-trifluoroethanol (TFE), and phenol are discussed in detail. Preparative-scale electrolysis experiments, carried out at -1.5 V versus the standard calomel electrode (SCE) in CO -saturated acetonitrile, reveal that the process selectivity is extremely sensitive to the acid strength, producing CO and formate in different faradaic yields.

Natural Abundance N and C Solid-State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry.

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a versatile characterization technique that can provide a plethora of information complementary to single crystal X-ray diffraction (SCXRD) analysis. Herein, we present an experimental and computational investigation of the relationship between the geometry of a halogen bond (XB) and the SSNMR chemical shifts of the non-quadrupolar nuclei either directly involved in the interaction ( N) or covalently bonded to the halogen atom ( C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors.

Scalable Binder-Free Supersonic Cold Spraying of Nanotextured Cupric Oxide (CuO) Films as Efficient Photocathodes.

We demonstrate production of nanotextured p-type cupric oxide (CuO) films via a low-cost scalable supersonic cold spray method in open air conditions. Simply sweeping the spray nozzle across a substrate produced a large-scale CuO film. When used as hydrogen evolution photocathodes, these films produced photocurrent densities (PCD) of up to 3.

Electrocatalytic reduction of CO2 by thiophene-substituted rhenium(i) complexes and by their polymerized films.

Three novel thiophene substituted bipyridine ligands and their corresponding rhenium complexes were synthesized and tested for the electrocatalytic reduction of CO2. Two complexes underwent oxidative electropolymerization on a glassy carbon electrode (GCE) surface. The conductive polymers chemically deposited on the GCE allow electron transport from the surface to the polymer-attached rhenium catalytic center in contact with the solution.

The Role of the Amino Protecting Group during Parahydrogenation of Protected Dehydroamino Acids.

A series of dehydroamino acids endowed with different protective groups at the amino and carboxylate moieties and with different substituents at the double bond have been reacted with parahydrogen. The observed ParaHydrogen Induced Polarization (PHIP) effects in the (1)H NMR spectra are strongly dependent on the amino protecting group. DFT calculations allowed us to establish a relationship between the structures of the reaction intermediates (whose energies depend on the amido substitution) and the observed PHIP patterns.

Enhanced Photoelectrochemical Solar Water Splitting Using a Platinum-Decorated CIGS/CdS/ZnO Photocathode.

A Cu(InGa)Se2 film was modified with CdS/ZnO for application to solar water splitting. Platinum was electrodeposited on the ZnO layer as a hydrogen evolution catalyst. The effects of the electroplating time and acidity level of the electrolyte on the photocurrent density were studied.

A local proton source in a [Mn(bpy-R)(CO)3Br]-type redox catalyst enables CO2 reduction even in the absence of Brønsted acids.

The effect of a local proton source on the activity of a bromotricarbonyl Mn redox catalyst for CO2 reduction has been investigated. The electrochemical behaviour of the novel complex [fac-Mn(dhbpy)(CO)3Br] (dhbpy = 4-phenyl-6-(1,3-dihydroxybenzen-2-yl) 2,2'-bipyridine), containing two acidic OH groups in the proximity of the metal centre, under a CO2 atmosphere showed a sustained catalysis in homogeneous solution even in the absence of Brønsted acids.

Photophysics of singlet and triplet intraligand excited states in [ReCl(CO)3(1-(2-pyridyl)-imidazo[1,5-α]pyridine)] complexes.

Excited-state characters and dynamics of [ReCl(CO)3(3-R-1-(2-pyridyl)-imidazo[1,5-α]pyridine)] complexes (abbreviated ReGV-R, R = CH3, Ph, PhBu(t), PhCF3, PhNO2, PhNMe2) were investigated by pico- and nanosecond time-resolved infrared spectroscopy (TRIR) and excited-state DFT and TD-DFT calculations. Near UV excitation populates the lowest singlet state S1 that undergoes picosecond intersystem crossing (ISC) to the lowest triplet T1. Both states are initially formed hot and relax with ∼20 ps lifetime.

Monolithic cells for solar fuels.

Hybrid energy generation models based on a variety of alternative energy supply technologies are considered the best way to cope with the depletion of fossil energy resources and to limit global warming. One of the currently missing technologies is the mimic of natural photosynthesis to convert carbon dioxide and water into chemical fuel using sunlight. This idea has been around for decades, but artificial photosynthesis of organic molecules is still far away from providing real-world solutions.