General Construction of Asymmetric Amine Ethers via Efficient Transesterification.

A novel method to prepare asymmetric amine ethers is reported. Tertiary amine alcohol hydrogen sulfate intermediates are prepared through a reactive distillation process, followed by the transesterification process to afford eventually asymmetric amine ethers. Experiments and DFT calculations revealed the essential roles the sulfate group plays in the highly selective monoesterification process. This clean method is tolerant towards various functional groups with good yields under mild condition, which is obviously superior compared to the conventional processes.

Carbon-Atom Exchange between [MC2]+ (M = Os and Ir) and Methane: on the Thermodynamic and Dynamic Aspects.

Gas-phase reactions of [OsC2]+ and [IrC2]+ with methane at ambient temperature have been studied using quadrupole-ion trap mass spectrometry combined with quantum chemical calculations. Both [OsC2]+ and [IrC2]+ undergo carbon-atom exchange reactions with methane. The associated mechanisms for the two systems are found to be similar. The differences in the rates of carbon isotope exchange reactions of methane with [MC2]+ (M = Os and Ir) are explained by several factors like the energy barrier for the initial H3C-H bond breaking processes, the molecular dynamics, orbital interactions, and the H-binding energies of the pivotal steps. Besides, the number of participating valence orbitals might be one of the keys to regulate the rate in the key step. The present findings may provide useful ideas and inspiration for designing similar processes.

Effects of Central Metal Ion on Binuclear Metal Phthalocyanine-Based Redox Mediator for Lithium Carbonate Decomposition.

Li2CO3 is the most tenacious parasitic solid-state product in lithium-air batteries (LABs). Developing suitable redox mediators (RMs) is an efficient way to address the Li2CO3 issue, but only a few RMs have been investigated to date, and their mechanism of action also remains elusive. Herein, we investigate the effects of the central metal ion in binuclear metal phthalocyanines on the catalysis of Li2CO3 decomposition, namely binuclear cobalt phthalocyanine (bi-CoPc) and binuclear cobalt manganese phthalocyanine (bi-CoMnPc). Density functional theory (DFT) calculations indicate that the key intermediate peroxydicarbonate (*C2O62-) is stabilized by bi-CoPc2+ and bi-CoMnPc3+, which is accountable for their excellent catalytic effects. With one central metal ion substituted by manganese for cobalt, the bi-CoMnPc's second active redox couple shifts from the second Co(II)/Co(III) couple in the central metal ion to the Pc(-2)/Pc(-1) couple in the phthalocyanine ring. In artificial dry air (N2-O2, 78:22, v/v), the LAB cell with bi-CoMnPc in electrolyte exhibited 261 cycles under a fixed capacity of 500 mAh g-1carbon and current density of 100 mA g-1carbon, significantly better than the RM-free cell (62 cycles) and the cell with bi-CoPc (193 cycles).

How Doping Affects the Activity of the Aluminum Oxide Support.

The performance of heteronuclear clusters [AlXO3 ]+ (X=Al, AlO4 , AlMg2 O2 , AlZnO, AlAu2 , Mg, Y, VO, NbO, TaO) in activating methane has been explored by a combination of high-level quantum calculations with reported and supplementary gas-phase experiments. With different dopants in [AlXO3 ]+ , the mechanism, reactivity and selectivity towards methane activation varies accordingly. The classic HAT competes with PCET, depending on the composition of intramolecular interactions. Although the existence of terminal oxygen radical is beneficial for classic HAT, the Alt -C interaction in the [AlXO3 ]+ clusters as enhanced by the strongly electronegative doping groups (X=Al, AlZnO, Mg, Zn, VO, NbO, TaO) favors the PCET process, facilitating C-H bond breaking. In addition, with different dopants, the destiny of the split methyl group varies accordingly. While strong interaction between Alt and CH3 results in the formation of the Alt -C bond, dopants with variable valance may promote the formation of deep-oxidation products like formaldehyde. It has been discussed in detail how to regulate the activity and selectivity of the active center of the catalyst via rational doping.

Methane Activation by [AlFeO3 ]+ : the Hidden Spin Selectivity.

The performance of heteronuclear cluster [AlFeO3 ]+ in activating methane has been explored by a combination of high-level quantum chemical calculations with gas-phase experiments. At room temperature, [AlFeO3 ]+ is a mixture of 7 [AlFeO3 ]+ and 5 [AlFeO3 ]+ , in which two states lead to different reactivity and chemoselectivity for methane activation. While hydrogen extracted from methane is the only product channel for the 7 [AlFeO3 ]+ /CH4 couple, 5 [AlFeO3 ]+ is able to convert this substrate to formaldehyde. In addition, the introduction of an external electric field may regulate the reactivity and product selectivity. The interesting doping effect of Fe and the associated electronic origins are discussed, which may guide one on the design of Fe-involved catalyst for methane conversion.

Size Effects in Gas-phase C-H Activation.

The gas-phase clusters reaction permits addressing fundamental aspects of the challenges related to C-H activation. The size effect plays a key role in the activation processes as it may substantially affect both the reactivity and selectivity. In this paper, we reviewed the size effect related to the hydrocarbon oxidation by early transition metal oxides and main group metal oxides, methane activation mediated by late transition metals. Based on mass-spectrometry experiments in conjunction with quantum chemical calculations, mechanistic discussions were reviewed to present how and why the size greatly regulates the reactivity and product distribution.

Genome-wide association study for biomass accumulation traits in soybean.

Soybean is one of the most versatile crops for oil production, human diets, and feedstocks. The vegetative biomass of soybean is an important determinant of seed yield and is crucial for the forage usages. However, the genetic control of soybean biomass is not well explained. In this work, we used a soybean germplasm population, including 231 improved cultivars, 207 landraces, and 121 wild soybeans, to investigate the genetic basis of biomass accumulation of soybean plants at the V6 stage. We found that biomass-related traits, including NDW (nodule dry weight), RDW (root dry weight), SDW (shoot dry weight), and TDW (total dry weight), were domesticated during soybean evolution. In total, 10 loci, encompassing 47 putative candidate genes, were detected for all biomass-related traits by a genome-wide association study. Among these loci, seven domestication sweeps and six improvement sweeps were identified. Glyma.05G047900, a purple acid phosphatase, was a strong candidate gene to improve biomass for future soybean breeding. This study provided new insights into the genetic basis of biomass accumulation during soybean evolution. Supplementary information: The online version contains supplementary material available at 10.1007/s11032-023-01380-6.

On the performance of the M-C (M = Fe, Ru, Os) unit toward methane activation.

Gas-phase reactions of [MC]+ (M = Os and Ru) with methane at ambient temperature have been studied by using quadrupole-ion trap (Q-IT) mass spectrometry combined with quantum chemical calculations. Theoretical calculations reveal the influence of electronic signatures and that it is the energy gap of the associated frontier molecular orbitals that dominates the ability of the cluster in the initial H3C-H bond breaking. By extension, a theoretical consideration upon changing the ligand from carbide to carbyne and eventually to carbene reveals that the reactivities of the M-complex (M = Os, Ru and Fe) are determined by the energy gap of the involved orbitals. In addition, a few factors like the dipole moment, spin density and charge distributions influence the orbital energy gap to different extents. Thus, altering the local structure of the active center to modulate the orbital distribution may be a possible means of regulation of the activity.

Striking Size and Doping Effects of Ti-Si-O Clusters on Methane Conversion Reactions.

The size and doping effects in methane activation by Ti-Si-O clusters have been explored by using a combination of gas-phase experiments and quantum chemical calculations. All [Tim Sin O2(m+n) ].+ (m+n=2, 3, 8, 10, 12, 14) clusters can extract a hydrogen from methane. The associated energies and structures have been revealed in detail. Moreover, the doping and size effects have been discussed involving generalized Kohn-Sham energy decomposition analysis, natural population analysis, Wiberg bond indexes (WBI), molecular polarity index (MPI) and ionization potential (IP). It suggested that Ti-Si-O clusters with a low Ti : Si ratio is beneficial to adsorbing methane and inclination to the hydrogen atom transfer (HAT) process, while the clusters with a high Ti : Si ratio favors the generation of a terminal oxygen radical and results in high reactivity and turnover frequency. On the other hand, a cluster size of m+n=12 is recommended considering both the ionization potential and the turnover frequency of the reaction. Hopefully, these finding will be instructive for the design of high-performance Ti-Si-O catalyst toward methane conversion.

General Construction of Amine via Reduction of N=X (X = C, O, H) Bonds Mediated by Supported Nickel Boride Nanoclusters.

Amines play an important role in synthesizing drugs, pesticides, dyes, etc. Herein, we report on an efficient catalyst for the general construction of amine mediated by nickel boride nanoclusters supported by a TS-1 molecular sieve. Efficient production of amines was achieved via catalytic hydrogenation of N=X (X = C, O, H) bonds. In addition, the catalyst maintains excellent performance upon recycling. Compared with the previous reports, the high activity, simple preparation and reusability of the Ni-B catalyst in this work make it promising for industrial application in the production of amines.

Underlying Mechanisms of Reductive Amination on Pd-Catalysts: The Unique Role of Hydroxyl Group in Generating Sterically Hindered Amine.

Pd nanospecies supported on porous g-C3N4 nanosheets were prepared for efficient reductive amination reactions. The structures of the catalysts were characterized via FTIR, XRD, XPS, SEM, TEM, and TG analysis, and the mechanisms were investigated using in situ ATR−FTIR spectroscopic analysis complemented by theoretical calculation. It transpired that the valence state of the Pd is not the dominating factor; rather, the hydroxyl group of the Pd(OH)2 cluster is crucial. Thus, by passing protons between different molecules, the hydroxyl group facilitates both the generation of the imine intermediate and the reduction of the C=N unit. As a result, the sterically hindered amines can be obtained at high selectivity (>90%) at room temperature.

On the origin of reactivity variation upon sequential ligation: the [Re(Cl)x]+/CH4 (x = 1-3) couples.

The potential of [ReClx]+ (x = 1-3) in activating methane has been explored by using a combination of gas-phase experiments and high-level quantum calculations. When the number of Cl ligands increases, the reactivity towards methane activation varies accordingly. While [ReClx]+ (x = 1-2) are able to dehydrogenate methane by a three-state reactivity scenario, [ReCl3]+ shows inertness towards methane at ambient conditions. Furthermore, the product ion [ClRe(H)CH]+ of the [ReCl]+/CH4 couple could continue to activate methane and liberate molecular dihydrogen but another product ion [Cl2ReCH2]+ is unreactive with methane. Obviously, the nature and the number of ligands make a difference to the reactivity towards methane activation. The associated reaction mechanism and the electron origins for the rather different reactivities are discussed in detail. Finally and more importantly, instructive information concerning the rational design of Re-catalysts for methane conversion is obtained.

On the origins of the mechanistic variants in the thermal reactions of Sx+ (x = 1-3) with benzene.

The S-π interaction between sulfur atom(s) and aromatic ring prevails in chemical and biochemical processes. The thermal gas-phase reactions of the Sn+ (n = 1-3) ions with benzene have been explored by using Quadrupole-Ion Trap (Q-IT) mass spectrometry complemented by quantum chemical calculations. Charge transfer was found to be the only reaction channel for S2+/C6H6, while both charge transfer and bond activation are available for the S+/C6H6 and S3+/C6H6 couples. Upon interrogating the associated electronic origins, multiple factors were found to matter for these processes. In contrast to the σ-type two-center three-electron (2c-3e) S-π hemibond as reported previously, unusual S-π hemibonds were addressed for the Sn+/C6H6 couples, i.e. the 2c-3e π(S061Eπ) and the three-center three-electron (3c-3e) σ(S2061Eπ) hemibonds. Such S-π interaction was found to be responsible for the charge transfer processes in S+/C6H6 and S2+/C6H6, but uninvolved in any transformation for S3+/C6H6.

Thermal Activation of CH4 and H2 as Mediated by the Ruthenium Oxide Cluster Ions [RuOx ]+ (x=1-3): On the Influence of Oxidation States.

Thermal gas-phase reactions of the ruthenium-oxide clusters [RuOx ]+ (x=1-3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]+ /CH4 couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO2 ]+ brings about the generations of [Ru,O,C,H2 ]+ /H2 O, [Ru,O,C]+ /H2 /H2 O, and [Ru,O,H2 ]+ /CH2 O, whereas [RuO3 ]+ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H2 ). Regarding the reactions with H2 , as compared to CH4 , both [RuO]+ and [RuO2 ]+ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO3 ]+ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H-H bond activation. Furthermore, the reactivity patterns of [RuOx ]+ (x=1-3) with CH4 and H2 have been compared with the previously reported results of Group 8 analogues [OsOx ]+ /CH4 /H2 (x=1-3) and the [FeO]+ /H2 system. The electronic origins for their distinctly different reaction behaviors have been addressed.

Tuning the Reactivities of the Heteronuclear [Aln V3-n O7-n ]+ (n=1,†2) Cluster Oxides towards Methane by Varying the Composition of the Metal Centers.

The thermal gas-phase reactions of [Al2 VO5 ]+ and [AlV2 O6 ]+ with methane have been explored by using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry complemented by high-level quantum chemical calculations. Both cluster ions chemisorbed methane as the major reaction channels at room temperature. [Al2 VO5 ]+ could break only one C-H bond to liberate CH3 , whereas [AlV2 O6 ]+ exhibited higher oxidizing ability such that it brings about the selective generation of formaldehyde. Mechanistic aspects are revealed and the crucial roles of the metal centers are discussed.

On the Remarkable Role of the Nitrogen Ligand in the Gas-Phase Redox Reaction of the N2 O/CO Couple Catalyzed by [NbN].

The thermal gas-phase catalytic reduction of N2 O by CO, mediated by the transition-metal nitride cluster ion [NbN]+ , has been explored by using FT-ICR mass spectrometry and complemented by high-level quantum chemical calculations. In contrast to the [Nb]+ /[NbO]+ and [NbO]+ /[Nb(O)2 ]+ systems, in which the oxidation of [Nb]+ and [NbO]+ with N2 O is facile, but in which neither [NbO]+ nor [Nb(O)2 ]+ react with CO at room temperature, the [NbN]+ /[ONbN]+ system at ambient temperature mediates the catalytic oxidation of CO. The origins of the distinctly different reactivities upon nitrogen ligation are addressed by quantum chemical calculations.

Selective C-O Coupling Hidden in the Thermal Reaction of [Al2 CuO5 ]+ with Methane.

The thermal gas-phase reaction of [Al2 CuO5 ]+ with methane has been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. The generation of atomic [Cu]+ from the [Al2 CuO5 ]+ /CH4 couple corresponds to the only reaction channel. Labeling experiments and computational studies strongly suggest that methane activation is indeed involved in the production of [Cu]+ , and generation of CH2 O prevails. Mechanistic aspects and the associated doping effects are discussed.

On the Origin of the Distinctly Different Reactivity of Ruthenium in [MO]+ /CH4 Systems (M=Fe, Ru, Os).

The thermal gas-phase reactions of [RuO]+ with methane have been explored by FT-ICR mass spectrometry and high-level quantum-chemical calculations. In contrast to the previously studied [FeO]+ /CH4 and [OsO]+ /CH4 couples, which undergo oxygen/hydrogen atom transfers and dehydrogenation, respectively, the [RuO]+ /CH4 system produces selectively [Ru(CH)2 ]+ and H2 O, albeit with much lower efficiency. Various mechanistic scenarios were uncovered, and the associated electronic origins were revealed by high-level quantum-chemical calculations. The reactivity differences observed for the [MO]+ /CH4 couples (M=Fe, Ru, Os) are due to the subtle interplay of the spin-orbit coupling efficiency, orbital overlap, and relativistic effects.

Direct Room-Temperature Conversion of Methane into Protonated Formaldehyde: The Gas-Phase Chemistry of Mercury among the Zinc Triad Oxide Cations.

In thermal reactions of methane with diatomic metal oxides [MO].+ of the zinc triad (M=Zn, Cd, Hg), protonated formaldehyde [CH2 OH]+ is generated as the major product only for the [HgO].+ /CH4 couple. Mechanistic insight is provided by high-level quantum-chemical calculations, and relativistic effects are suggested to be the root cause for the unexpected thermal production of [CH2 OH]+ from [HgO].+ /CH4 .

Experimental Identification of the Active Site in the Heteronuclear Redox Couples [AlVOx ]+. /CO/N2 O (x=3,†4) by Gas-Phase IR Spectroscopy.

Cryogenic ion vibrational spectroscopy was used in combination with electronic structure calculations to identify the active site in the oxygen atom transfer reaction [AlVO4 ]+. +CO→[AlVO3 ]+. +CO2 . Infrared photodissociation spectra of messenger-tagged heteronuclear clusters demonstrate that in contrast to [AlVO4 ]+. , [AlVO3 ]+. is devoid of a terminal Al-Ot unit while the terminal V=Ot group remains intact. Thus it is the Al-Ot moiety that forms the active site in the [AlVOx ]+. /CO/N2 O (x=3, 4) redox couples, which is in line with theoretical predictions.