Divalent Species Research Articles

Confinement chemistry of FeOx centers for activating molecular oxygen under ambient conditions.

Activating molecular oxygen under mild conditions is highly important for developing advanced green technologies and for understanding the origin and running of life as well, which still remains a challenge. In this work, we report on the confinement chemistry for activating molecular oxygen over oxides under mild conditions by presenting the synthesis and characterization of FeOx species confined to the pores of support CeO2 nanospheres. Active catalytic materials are obtained by a controllable three-step method via the formation of porous CeO2 nanospheres that have an average diameter of 120 nm and exhibit a large surface area of 168 m2 g-1 and a pore size of 18.7 nm, confining FeOx in intimate contact with ultra-small Pt particles in pores. The optimized PtOy-FeOx/CeO2-H catalyst showed an excellent performance in the preferential oxidation of CO reactions, as featured by 100% CO conversion at room temperature with almost no attenuation in a prolonged operation, which could not be accessible without pore-confined FeOx centers. Mechanical studies prove that the reaction progresses via abnormal non-competitive adsorption associated with synergistic roles from uniform loading, stabilization of divalent Fe species, surface oxygen activation on CeO2 supports, and the reduced H2 spillover effect on Pt0, making the CO species adsorbed on Ptδ+ easier to be desorbed. The methodology demonstrated here may inspire one to explore more advanced catalysts with high activity at room temperature essential for a wide range of applications.

Unlocking the origin of triggering hysteretic oxygen capacity in divalent species incorporated O-type sodium layered-oxide cathodes

A novel electrochemistry featuring anion redox via oxygen ions beyond conventional cation redox via transition metal (TM) ions has been investigated intensively to achieve high-energy-density cathodes for A-ion batteries, where A refers to alkali metals. Unlike lithium-ion batteries (LIBs), this novel paradigm is crucial and realizable for sodium-ion batteries (SIBs) because Li+-excess layered oxides showed highly reversible oxygen capacities during the first cycle. However, the hysteretic oxygen redox induced by Li+-migration and cyclic degradation derived from oxygen loss remain unsolved in monovalent-species-containing cathodes. In this study, the Mg2+-containing oxygen redox picture was investigated in detail to determine the critical factors that trigger the hysteretic oxygen capacities in the Mn- and Ti-based cathode models (i.e., Na[Mg1/3Mn2/3]O2 and Na[Mg1/3Ti2/3]O2) and the chemical features of Mn(3d)−O(2p) and Ti(3d)−O(2p) were generalized to exploit the full potential of oxygen redox in SIBs and LIBs. First, the Mg2+-site stability is critically determined using the Na+ coordination number, and it is located in the thermodynamically most stable Mn or Ti layer, thereby mitigating the Mg2+ migration during desodiation. Second, the hysteretic oxygen capacity for Na[MgxTM1−x]O2 is attributed to the phase transition induced by the interlayer O−O dimerization. Finally, the level of O−O dimerization, which is directly correlated with the hysteretic oxygen capacity, is governed by the TM−O bonding properties, such as ionic or covalent characteristics. Therefore, our findings provide insights into the utilization of the oxygen redox reaction of O-type Mg2+-incorporated oxide cathodes for advanced SIBs.

Exploiting valence band mapping and select blue-green and red phosphorescence decay of γ-irradiated nanoscale Eu3+: Gd2O3 below concentration quenching

We report on manifested blue-green and red emission features in Eu 3+ doped Gd 2 O 3 nanophosphors, subjected to 1.3 MeV gamma ( γ ) -irradiation and up to a dose of 2.4 kGy. While Eu 3+ states can be predicted at the core, occurrence of divalent species (Eu 2+ ) at the nanoparticle surfaces was revealed from the X-ray photoelectron spectroscopy (XPS) studies. Characteristic Eu 3+ activated orange-red emissions (590–650 nm) were revealed, and the nature of the corresponding transitions assigned. Moreover, time resolved photoluminescence (TR-PL) technique was employed to evaluate the lifetime of carriers participating in specific recombination emission events with and without specimens being exposed to γ -rays. The lifetime decay of our nanophosphor ranges between ∼1.6–1.3 ms, for electrically driven (ED: 5 D 0 → 7 F 2 ) and ∼1.98–1.56 ms, for magnetically driven (MD: 5 D 0 → 7 F 1 ) emissions. The modulation of ED and MD transitions in a suitable nanophosphor will have immense scope in next generation smart windows, display panels and bioimaging prospects. • XPS analysis reveals near surface Eu 2+ (divalent) states and dominant Eu 3+ (trivalent) at the core. • Modulation of PL emissions accompanied via 5 D 0 . → 7 F 1 (magnetic) and 5 D 0 → 7 F 2 (electric) transitions has been realized with dopant concentration andγ-dose. • TR-PL study offers decay parameters that seem to vary with dopant concentration and radiation exposure. • Two possible excitation pathways can populate the 5 D 0 level, one via 5 D 1 level and the other directly into 5 D 0 at higher dose.

Evaluation of Manganese Cubanoid Clusters for Water Oxidation Catalysis: From Well-Defined Molecular Coordination Complexes to Catalytically Active Amorphous Films.

With a view to developing multimetallic molecular catalysts that mimic the oxygen‐evolving catalyst (OEC) in Nature's photosystem II, the synthesis of various dicubanoid manganese clusters is described and their catalytic activity investigated for water oxidation in basic, aqueous solution. Pyridinemethanol‐based ligands are known to support polynuclear and cubanoid structures in manganese coordination chemistry. The chelators 2,6‐pyridinedimethanol (H2L1) and 6‐methyl‐2‐pyridinemethanol (HL2) were chosen to yield polynuclear manganese complexes; namely, the tetranuclear defective dicubanes [MnII 2MnIII 2(HL1)4(OAc)4(OMe)2] and [MnII 2MnIII 2(HL1)6(OAc)2] (OAc)2⋅2 H2O, as well as the octanuclear‐dicubanoid [MnII 6MnIII 2(L2)4(O)2(OAc)10(HOMe/OH2)2]⋅3MeOH⋅MeCN. In freshly prepared solutions, polynuclear species were detected by electrospray ionization mass spectrometry, whereas X‐band electron paramagnetic resonance studies in dilute, liquid solution suggested the presence of divalent mononuclear Mn species with g values of 2. However, the magnetochemical investigation of the complexes’ solutions by the Evans technique confirmed a haphazard combination of manganese coordination complexes, from mononuclear to polynuclear species. Subsequently, the newly synthesized and characterized manganese molecular complexes were employed as precursors to prepare electrode‐deposited films in a buffer‐free solution to evaluate and compare their stability and catalytic activity for water oxidation electrocatalysis.

Lattice Boltzmann method to simulate three-dimensional ion channel flow using fourth order Poisson–Nernst–Planck–Bikerman model

Over the past three decades, the lattice Boltzmann method (LBM) has been applied to a vast range of hydrodynamic and non-hydrodynamic (e.g., ion transport) systems. In conjunction with the immersed boundary method (IBM), the LBM has been successfully implemented to solve systems with complex geometries. In this study, the immersed boundary–lattice Boltzmann method (IB-LBM) is implemented to simulate nanoscale ion transport. Traditionally, ion transport is described through the Poisson–Nernst–Planck (PNP) equations where ionic interactions are included. In the current paper, the fourth order Poisson–Nernst–Planck–Bikerman (4PNPBik) model has been used. In addition to ionic interactions, the 4PNPBik model includes the effects of the finite size of particles (ions and water) and interactions between ions and its surrounding medium. Applicability of the 4PNPBik model is demonstrated through comparison of the experimental and predicted ion activity. Implementation of the 4PNPBik model has been validated by comparing the predicted current–voltage curve with the analytical result. The transient receptor potential (TRP) ion channel of the vanilloid group (TRPV4) is used to demonstrate the applicability of this approach. The TRPV4 is a nonselective cation channel that prefers divalent cationic species over monovalent cations. In this study, this selectivity is demonstrated by comparing the concentration profiles of calcium, sodium, and chloride ions. Further, the role of the finite size of particles and nonlocal electrostatics is discussed by comparing the results obtained from the PNP and 4PNPBik models under identical initial and boundary conditions.

Transition-Metal Chemistry of the Heavier Alkaline Earth Atoms Ca, Sr, and Ba.

ConspectusAlkaline earth elements beryllium, magnesium, calcium, strontium, and barium with an ns2 valence-shell configuration are usually classified as main-group elements that belong to the s-block atoms. For a long time, the elements were considered to be rather chemically uninteresting atomic species due to preconceived ideas about bonding, structure, and reactivity. They typically use the two ns valence electrons in forming ionic salt compounds with the metal in a formal oxidation state of +2. For the heavier alkaline earth atoms, calcium, strontium, and barium, their (n - 1)d atomic orbitals (AOs) are empty but lie close in energy to the valence np orbitals. Earlier theoretical investigations have already suggested that these elements can employ the (n - 1)d AOs to some extent to form polar bonds in divalent species in which the alkaline earth metal centers are sufficiently positively charged. The d orbital involvement increases from Ca to Sr and markedly in Ba. Thus, barium has been termed an honorary transition metal.Recently, molecular complexes of Ca, Sr, and Ba were prepared in the gas phase and in a low-temperature solid neon matrix and were detected by infrared spectroscopy. An analysis of the electronic structures of [Ba(CO)]+, [Ba(CO)]-, saturated coordinated octacarbonyls [M(CO)8] and [M(CO)8]+, isoelectronic dinitrogen complexes [M(N2)8] and [M(N2)8]+, and the tribenzene complexes [M(Bz)3] (M = Ca, Sr, Ba) revealed that the metal-ligand bonding can be straightforwardly discussed using the traditional Dewar-Chatt-Duncanson (DCD) model as in classical transition-metal complexes. The metal-ligand bonds can be explained with metal → ligand π back donation from occupied metal (n - 1)d AOs to vacant antibonding π molecular orbitals of the ligands with concomitant σ donation from occupied MOs of the ligands to vacant metal d orbitals of the alkaline earth atoms. In addition, heteronuclear Ca-Fe carbonyl cation complexes were also produced in the gas phase. Bonding analysis of the coordination saturated [CaFe(CO)10]+ complex implies that it can be described by the bonding interactions between a [Ca(CO)6]2+ fragment and an [Fe(CO)4]- anion fragment in forming a Fe → Ca d-d dative bond. The nature of metal-ligand and metal-metal bonding was quantitatively elucidated by the energy decomposition analysis in conjunction with the natural orbitals for the chemical valence (EDA-NOCV) method, which indicate that the (n - 1)d AOs of the alkaline earth metals are the dominant orbitals participating in the covalent interactions, just as typical transition metals. The results indicate that the heavier alkaline earth elements have a much richer covalent chemistry than previously thought. These findings, along with earlier studies, suggest that the heavier alkaline earth atoms Ca, Sr, and Ba should be classified as transition metals rather than main group atoms in the periodic table of the elements. This interesting structural chemistry, together with some recently reported examples of spectacular reactivity, establishes these elements as exciting and promising research targets in current research.

Synthetic Access to Pentacene‐Silylene Adducts via Dehydrogenative Silylation of a 5,14‐Dihydropentacene with a Stable Silylene

AbstractUtility of a thermally stable divalent silicon species (silylene) toward the dehydroaromatization of a dihydropentacene is demonstrated. The reaction of a cyclic (alkyl)(amino)silylene with 6,13‐dipropyl‐5,14‐dihydropentacene afforded the corresponding pentacene‐silylene adducts. The reaction likely proceeds through a combination of 1,4‐dehydrogenation and (1+4) cycloaddition of the silylene towards the dihydropentacene.

Rapid Fabrication by Lyotropic Self-Assembly of Thin Nanofiltration Membranes with Uniform 1 Nanometer Pores.

Nanostructured materials with precisely defined and water-bicontinuous 1-nm-scale pores are highly sought after as advanced materials for next-generation nanofiltration membranes. While several self-assembled systems appear to satisfy this need, straightforward fabrication of such materials as submicron films with high-fidelity retention of their ordered nanostructure represents a nontrivial challenge. We report the development of a lyotropic liquid crystal mesophase that addresses the aforementioned issue. Films as thin as ∼200 nm are prepared on conventional support membranes using solution-based methods. Within these films, the system is composed of a hexagonally ordered array of ∼3 nm diameter cylinders of cross-linked polymer, embedded in an aqueous medium. The cylinders are uniformly oriented in the plane of the film, providing a transport-limiting dimension of ∼1 nm, associated with the space between the outer surfaces of nearest-neighbor cylinders. These membranes exhibit molecular weight cutoffs of ∼300 Da for organic solutes and are effective in rejecting dissolved salts, and in particular, divalent species, while exhibiting water permeabilities that rival or exceed current state-of-the-art commercial nanofiltration membranes. These materials have the ability to address a broad range of nanofiltration applications, while structure-property considerations suggest several avenues for potential performance improvements.

AFX Zeolite for Use as a Support of NH3-SCR Catalyst Mining through AICE Joint Research Project of Industries–Academia–Academia

This paper introduces a joint industries–academia–academia research project started by researchers in several automobile companies and universities working on a single theme. Our first target was to find a zeolite for NH3-SCR, that is, zeolite mining. Zeolite AFX, having the same topology of SSZ-16, was found to be the one of the zeolites. SSZ-16 can be synthesized by using an organic structure-directing agent such as 1,1′-tetramethylenebis(1-azonia-4-azabicyclo[2.2.2]octane; Dab-4, resulting in the formation of Al-rich SSZ-16 with Si/Al below five. We found that AFX crystallized by use of N,N,N′,N′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium ion, called TEBOP in this study, had the same analog as SSZ-16 having Si/Al around six and a smaller particle size than SSZ-16. The AFX demonstrated a high performance for NH3-SCR as the zeolitic support to load a large number of divalent Cu ionic species with high hydrothermal stability.

Generation of Bis(ferrocenyl)silylenes from Siliranes

Divalent silicon species, the so-called silylenes, represent attractive organosilicon building blocks. Isolable stable silylenes remain scarce, and in most hitherto reported examples, the silicon center is stabilized by electron-donating substituents (e.g., heteroatoms such as nitrogen), which results in electronic perturbation. In order to avoid such electronic perturbation, we have been interested in the chemistry of reactive silylenes with carbon-based substituents such as ferrocenyl groups. Due to the presence of a divalent silicon center and the redox-active transition metal iron, ferrocenylsilylenes can be expected to exhibit interesting redox behavior. Herein, we report the design and synthesis of a bis(ferrocenyl)silirane as a precursor for a bis(ferrocenyl)silylene, which could potentially be used as a building block for redox-active organosilicon compounds. It was found that the isolated bis(ferrocenyl)siliranes could be a bottleable precursor for the bis(ferrocenyl)silylene under mild conditions.

Stabilization of novel N‐heterocyclic germylenes: A computational perspective

AbstractIn this theoretical survey, N‐heterocyclic Germylenes (NHGes; 1–13) are compared and contrasted at DFT. All singlet (s) and triplet (t) states of NHGes turn out as minima for showing no negative force constant on their energy surfaces. Yet, only s states appear as global minima. From thermodynamic view point, the scrutinized NHGes show singlet‐triplet energy gap (ΔEs–t) larger than that of VI and VII germylenes, in the range of 51.45–60.37 versus 49.72 and 42.83 kcal/mol, respectively. In addition, all species are found less stable than NHGes synthesized by Veith (V) and more stable than the NHGes synthesized by Herrmann (VI) and Driess (VII) and so except for 9s–13s structures, reminder singlet divalent species have minimum vibrational frequencies (υmin) more than 100 cm−1. From kinetic view point, the ΔEHOMO–LUMO (band gap) of all singlet NHGes under study is higher than that of Driess's germylene. Henceforth, 1s–8s structures as stable molecules satisfy the identified conditions by Hoffmann, Schleyer, and Schaefer. Dimer of the singlet 1H‐4‐germapyridine‐4‐ylidene (1s), is found 11.44 kcal/mol less thermodynamically stable than its corresponding aromatic monomer. Endothermicity of head‐to‐head dimerization indicates that the reaction is unfavorable for 1, just as 8, while exothermicity shows that head‐to‐head dimerization is favorable for the others especially 9. This survey indicates the substitution effects of fused rings on thermodynamic and kinetic stabilities of NHGes hoping to prompt the experimental attentions toward them.

Self-assembly of highly ordered DNA origami lattices at solid-liquid interfaces by controlling cation binding and exchange

The surface-assisted hierarchical self-assembly of DNA origami lattices represents a versatile and straightforward method for the organization of functional nanoscale objects such as proteins and nanoparticles. Here, we demonstrate that controlling the binding and exchange of different monovalent and divalent cation species at the DNA-mica interface enables the self-assembly of highly ordered DNA origami lattices on mica surfaces. The development of lattice quality and order is quantified by a detailed topological analysis of high-speed atomic force microscopy (HS-AFM) images. We find that lattice formation and quality strongly depend on the monovalent cation species. Na+ is more effective than Li+ and K+ in facilitating the assembly of high-quality DNA origami lattices, because it is replacing the divalent cations at their binding sites in the DNA backbone more efficiently. With regard to divalent cations, Ca2+ can be displaced more easily from the backbone phosphates than Mg2+ and is thus superior in guiding lattice assembly. By independently adjusting incubation time, DNA origami concentration, and cation species, we thus obtain a highly ordered DNA origami lattice with an unprecedented normalized correlation length of 8.2. Beyond the correlation length, we use computer vision algorithms to compute the time course of different topological observables that, overall, demonstrate that replacing MgCl2 by CaCl2 enables the synthesis of DNA origami lattices with drastically increased lattice order.

Seasonal Variation of Mercury and Its Isotopes in Atmospheric Particles at the Coastal Zhongshan Station, Eastern Antarctica.

Mercury (Hg) is a globally spread trace metal due to its long atmospheric residence time. Yet, our understanding of atmospheric processes (e.g., redox reactions and deposition) driving Hg cycling is still limited, especially in polar regions. The Antarctic continent, by virtue of its remoteness, is the perfect location to investigate Hg atmospheric processes in the absence of significant local anthropogenic impact. Here, we present the first 2 year record (2016-2017) of total suspended particulate mercury (PHg) concentrations along with a year-round determination of an Hg stable isotopic composition in particles collected at Zhongshan Station (ZSS), eastern Antarctic coast. The mean PHg concentration is 21.8 ± 32.1 pg/m3, ranging from 0.9 to 195.6 pg/m3, and peaks in spring and summer. The negative mass-independent fractionation of odd Hg isotopes (odd-MIF, average -0.38 ± 0.12‰ for Δ199Hg) and the slope of Δ199Hg/Δ201Hg with 0.91 ± 0.12 suggest that the springtime isotope variation of PHg is likely caused by in situ photo-oxidation and reduction reactions. On the other hand, the increase of PHg concentrations and the observed odd-MIF values in summer are attributed to the transport by katabatic winds of divalent species derived from the oxidation of elemental Hg in the inland Antarctic Plateau.

Computational investigation of two-dimensional LDHs and the modification of their electronic structure induced by defects

The exfoliation of layered double hydroxides was studied using DFT calculations with periodic boundary conditions. F−, Cl−, Br−, NO3− and CO32− were chosen as the counteranions to estimate their influence on the exfoliation energies. Two surfactants (dodecyl sulfate and dodecylbenzene sulfonate) were also considered for the simulations. The binding energies demonstrated that both NO3− and dodecyl sulfate favor the exfoliation over the other anions. Regarding the electronic structure, the band gaps were altered upon exfoliation. The comparison between the structural and energetic features of the hydrated and dehydrated 2D forms showed that the hydration degree is a relevant factor for the fabrication of novel composites. Band gap modifications were also observed after dehydration. The energetic and electronic aspects of the formation of vacancy defects were also analyzed. The defect formation energies showed that the removal of clusters (M(OH)x) is less costly than the formation of single atom vacancies. The band structures of the defective structures presented significant band gap changes. In certain cases, metallic states appeared as the divalent species were removed from the LDH layers. These results highlight the importance of 2D LDHs for photocatalytic applications, since many degrees of freedom are available for the tuning of the electronic structure.

High-Value Organic Acid Recovery from First-Generation Bioethanol Dunder Using Nanofiltration

Nanofiltration (NF) was investigated for the recovery of platform chemicals, specifically, succinic acid, from high-strength bioethanol waste (dunder). Conventional methods focusing on chemical precipitation entail poor selectivity in complex matrices and are inherently expensive owing to the consumption of large volumes of chemicals and the generation of excess by-product sludge. For these reasons, three commercially available NF membranes with varying molecular weight cut-off were screened in a dead-end configuration to benchmark transmission behavior at different solution chemistries including pH, feed pressure, concentration, and ionic strength prior to filtration with the industrial effluent. Examination of behavior with model solutions only reveals that both NF270 and NTR-7450 membranes exhibit a succinic acid permeation above 80% irrespective of pH and solute concentration, while the addition of inorganic salts, in particular, divalent species, lowered the transmission of succinic acid with all membranes, in particular, NF90. Measurements of the surface charge (zeta potential) before and after filtration of the industrial effluent indicate a shift toward more positive values for the polyamide membranes (NF90 and NF270) within the pH range of 2-10. This change in surface charge was attributed to the formation of complexes between humic compounds and divalent cations present in elevated concentrations. Considerable fouling was observed for all membranes with the mean permeate flux around 2 L/m(2)h at 5 bar for the NF270 and NTR-7450 membranes; however, findings from deionized water rinsing suggest that the majority of foulants reside within the reversible fouling layer. Finally, size exclusion chromatography (liquid chromatography-organic carbon detection) findings highlight substantial (>70%) rejection of biopolymers, humics, building blocks, and low-molecular-weight neutral species following filtration with all membranes. Overall, this work demonstrates the merits and potential of nanofiltration in the recovery of high-value organic acids from concentrated bioethanol waste.

Effect of Divalent Cations on the Structure and Mechanics of Vimentin Intermediate Filaments

Divalent cations behave as effective cross-linkers of intermediate filaments (IFs) such as vimentin IF (VIF). These interactions have been mostly attributed to their multivalency. However, ion-protein interactions often depend on the ion species, and these effects have not been widely studied in IFs. Here, we investigate the effects of two biologically important divalent cations, Zn2+ and Ca2+, on VIF network structure and mechanics in vitro. We find that the network structure is unperturbed at micromolar Zn2+ concentrations, but strong bundle formation is observed at a concentration of 100 μM. Microrheological measurements show that network stiffness increases with cation concentration. However, bundling of filaments softens the network. This trend also holds for VIF networks formed in the presence of Ca2+, but remarkably, a concentration of Ca2+ that is two orders higher is needed to achieve the same effect as with Zn2+, which suggests the importance of salt-protein interactions as described by the Hofmeister effect. Furthermore, we find evidence of competitive binding between the two divalent ion species. Hence, specific interactions between VIFs and divalent cations are likely to be an important mechanism by which cells can control their cytoplasmic mechanics.

Chemomechanical Design Factors for High Performance in Manganese-Based Spinel Cathode Materials for Advanced Sodium-Ion Batteries.

Manganese-based spinel cathode materials for sodium-ion batteries (SIBs) are promising candidates for next-generation batteries; especially, Na[Ni0.5Mn1.5]O4 (NNMO) should get attention because of its relatively high operating voltage and firm octahedral host structure. Here, first-principles calculations and the phase field method are used to elucidate the reasons for the low performance of NNMO compared with Li[Ni0.5Mn1.5]O4, and we determine the requirements for realizing high-performance cathode materials for SIBs. Owing to the Ni2+/Ni4+ double redox, NNMO could operate at a high voltage; however, the large Na+ increases the local site energy of the redox center, promoting electron extraction from the redox center, leading to unexpected voltage loss. Additionally, the homogeneous free energy confirms that NNMO would undergo phase separation into fully intercalated and deintercalated phases, inducing lattice misfits along the interfaces of the two phases. Particularly, a higher phase transition barrier and large Na+ cause fast phase separation, inducing increased polarization and severe stress field upon cycling. The present analysis with comprehensive first-principles calculations and the phase field method provides three critical factors toward high electrochemical performance: (i) strengthening Ni-O bonding to avoid undesirable voltage loss, (ii) increasing the vacancy/Na solubility during (de)sodiation to enhance cyclability, and (iii) suppressing the structural distortion during (de)sodiation to prevent mechanical failure. Based on these crucial points, additionally, we suggest the M-pillared Na1-xMx[Ni0.5Mn1.5]O4 (monovalent or divalent species, M), where the M works to strengthen the redox center for improved energy density and to alleviate the drastic structural change and voltage hysteresis for better cyclability, would have superior electrochemical performance as a cathode material for SIBs.

Glycerol Conversion to Lactic Acid with Unsupported Copper Salts and Bulk Cupric Oxide in Aqueous Alkali Media.

Glycerol conversion to lactic acid (LA) was investigated in aqueous alkali over eight unsupported copper compounds (CuBr2, CuBr, CuCl2, CuCl, CuF2, Cu(NO3)2,CuO, and Cu2O) for studying the effects of anion and valence. Powder X-ray diffraction and scanning electron microscopy measurements indicated that these copper compounds were reduced to metallic copper with different morphologies. Divalent copper compounds exhibited much better performances than the corresponding univalent species, ascribed to their greater reduction heat and higher local reaction temperature. Divalent copper species activity, ionic radius, and the reported reduction potential decreased in the same order: bromide > chloride > floride ≫ nitrate. With increasing reaction temperature, catalyst amount, NaOH concentration and reaction time, glycerol conversion, and LA selectivity increased (due to by-product conversions to LA). Kinetic studies indicated that glycerol disappearance rate was first-order with respect to its concentration. CuBr2 had greater activation energy and therefore exhibited better performance than CuO when reaction temperature was greater than 155°C. At 185°C, CuBr2 reached 95.7% lactic acid yield and 98.65% glycerol conversion.

Ferrocenyl-substituted low-coordinated heavier group 14 elements.

Several examples of stable low-coordinated species of heavier group 14 elements (Si, Ge, Sb, Pb) such as divalent species and multiple-bond compounds have been reported. With the goal in mind to create unprecedented low-coordinated species of heavier group 14 elements that exhibit considerably increased redox stability, ferrocenyl (Fc)-substituted low-coordinated species of heavier group 14 elements were designed. In this short account article, recent progress on the synthesis of Fc-based low-coordinated species of heavier group 14 elements is summarized.

The absorption and fluorescence spectra of 4-(3-methoxybenzylidene)-2-methyl-oxazalone interpreted by Franck-Condon simulation in various pH solvent environments.

The absorption and fluorescence spectra of 4-(3-methoxybenzylidene)-2-methyl-oxazalone (m-MeOBDI) dissolved in neutral, acidic, and basic solvent environments have been investigated and assigned by using Franck-Condon (FC) simulations at the quantum TDDFT level. Four different structures of m-MeOBDI in the ground and excited states are optimized and are found to be responsible for the observed absorption and fluorescence spectra. The (absorption) fluorescence of m-MeOBDI in pure methanol and neutral/basic methanol/water (1/9 vol) mixed solvent is found to arise from the (ground neutral N-I) excited neutral N-I* and cationic C-III* species, respectively. In acidic solvent, the absorption is found to arise from ground acidic C-II species, and the excited divalent cation DC-IV* is found to be formed in its excited state due to the excess H+ in the solution, and then it emits ∼560 nm fluorescence. FC simulations have also been employed to confirm our assignments as well as interpret the vibronic band profiles. As expected, the simulated emission spectrum of the divalent cationic species is in good agreement with the experimental observation. Therefore, within the present FC simulation, the observed absorption and fluorescence spectra have been reasonably interpreted and novel fluorescence mechanisms of m-MeOBDI in various pH solvent environments have been proposed.