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The reactivity of the molybdenum oxide cluster anion (MoO3)5O−, bearing an unpaired electron at a bridging oxygen atom (Ob.−), towards methane under thermal collision conditions has been studied by mass spectrometry and density functional theory calculations. This reaction follows the mechanism of hydrogen atom transfer (HAT) and is facilitated by the Ob.− radical center. The reactivity of (MoO3)5O− can be traced back to the appropriate orientation of the lowest unoccupied molecular orbitals (LUMO) that is essentially the 2p orbital of the Ob.− atom. This study not only makes up the blank of thermal methane activation by the Ob.− radical on negatively charged clusters but also yields new insights into methane activation by the atomic oxygen radical anions. [ABSTRACT FROM AUTHOR]

The reactivity of the molybdenum oxide cluster anion (MoO 3 ) 5 O - , bearing an unpaired electron at a bridging oxygen atom (O b .- ), towards methane under thermal collision conditions has been studied by mass spectrometry and density functional theory calculations. This reaction follows the mechanism of hydrogen atom transfer (HAT) and is facilitated by the O b .- radical center. The reactivity of (MoO 3 ) 5 O - can be traced back to the appropriate orientation of the lowest unoccupied molecular orbitals (LUMO) that is essentially the 2p orbital of the O b .- atom. This study not only makes up the blank of thermal methane activation by the O b .- radical on negatively charged clusters but also yields new insights into methane activation by the atomic oxygen radical anions., (© 2021 Wiley-VCH GmbH.)

Fundamental understanding regarding oxygen storage capacity involving how and why an active site can buffer a large number of oxygen atoms in redox processes is vital to the design of advanced oxygen storage materials, while it is challenging because of the complexity of heterogeneous catalysis. Herein, we identified that an eight-atom iridium-aluminum oxide cluster IrAlO 6 + can transfer all the oxygen atoms to catalytically oxidize six CO molecules. This finding represents a breakthrough in cluster catalysis where at most three oxygen atoms from a heteronuclear metal oxide cluster can be catalytically involved in CO oxidation. We found that oxygen prefers to be stored on aluminum to form an O 3 -• radical in the energetically unfavorable IrAlO 6 + isomer and generate the low-coordinated iridium that is pivotal to capturing CO and triggering the catalysis. The powerful electron cycling capability of iridium and the cooperative iridium-aluminum interplay are emphasized to drive the oxygen atom-transfer behavior.

The construction of C-N bonds by the direct incorporation of dinitrogen (N 2 ) instead of ammonia (NH 3 ) into active species is particularly desirable but has been rarely reported. Herein, a ditantalum carbide cluster anion (Ta 2 C 4 - ) capable of cleaving the N≡N bond and constructing a C-N bond under mild conditions has been identified using mass spectrometry, photoelectron imaging spectroscopy, and quantum-chemical calculations. The photoelectron spectrum of Ta 2 C 4 N 2 - is remarkably different from that of Ta 2 C 4 - and matches the simulated spectrum of the Ta 2 C 4 N 2 - species with an end-on-bonded CN unit. The formation of the C-N bond has also been supported by the CN - fragment observed in the collision-induced dissociation of Ta 2 C 4 N 2 - . The exceptional reactivity of Ta 2 C 4 - is ascribed to the low-valent metal center serving as an electron reservoir. This study provides a non-NH 3 route to construct C-N bonds by incorporating N 2 into carbide compounds to produce nitrogenous species.

Neutral manganese oxide clusters with the general composition Mn 2 N O 3 N+x (N=2-22; x=-1, 0, 1) with dimensions up to a nanosize were prepared by laser ablation and reacted with C 2 H 4 in a fast flow reactor. The size-dependent reactivity of C 2 H 4 adsorption on these clusters was experimentally identified and the adsorption reactivity decreases generally with an increase of the cluster size. Density functional theory calculations were performed to study the geometrical and electronic structures of the Mn 2 N O 3 N (N=1-6) clusters. The calculated results indicated that the coordination number and the charge distribution of the metal centers are responsible for the experimentally observed size-dependent reactivity. The highly charged Mn atoms with low coordination are preferential to adsorb C 2 H 4 . In contrast, the neutral manganese oxide clusters are completely inert toward the saturated hydrocarbon molecule C 2 H 6 . This work provides new perspectives to design related materials in the separation of hydrocarbon molecules., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Vanadium oxide cluster anions (V 2 O 5 ) n V x O y - (n = 1-31; x = 0, 1; and x + y ≤ 5) with different oxygen deficiencies (Δ = 2y-1-5x = 0, ± 1, and ±2) have been prepared by laser ablation and reacted to abstract hydrogen atoms from alkane molecules (n-butane) in a fast flow reactor. When the cluster size n is less than 25, the Δ = 1 series [(V 2 O 5 ) n O - clusters] that can contain atomic oxygen radical anions (O •- ) generally have much higher reactivity than the other four cluster series (Δ = -2, -1, 0, and 2), indicating that each atom counts in the hydrogen-atom abstraction (HAA) reactivity. Unexpectedly, all of the five cluster series have similar HAA reactivity when the cluster size is greater than 25. The critical dimension of vanadia particles separating the cluster behavior (each atom counts) from the bulk behavior (each atom contributes a little part) is thus about 1.6 nm (∼V 50 O 125 ). The strong electron-phonon coupling of the vanadia particles has been proposed to create the O •- radicals (V 5+ = O 2- + heat → V 4+ -O •- ) for the n > 25 clusters with Δ = -2, -1, 0, and 2. Such a mechanism is supported by a comparative study with the scandium system [(Sc 2 O 3 ) n Sc x O y - (n = 1-29; x = 0, 1; and x + y ≤ 4)] for which the Δ = 1 series [(Sc 2 O 3 ) n O - clusters] always have much higher HAA reactivity than the other cluster series.

To study the temporal and spatial distribution of dissolved organic matter (DOM) and the related influencing factors of Lake Chaohu, surface water samples were collected at seventeen sites in three different regions of the Lake from April 2013 to April 2014. The concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were then analyzed. A significance difference in DON concentration was observed among the sampling sites (P <0. 01, n = 13), which was caused by the terrestrial input from the western rivers and the bioavailability of DON. The ratio of total nitrogen to total phosphorus, total dissolved nitrogen to total dissolved phosphorus, and dissolved inorganic nitrogen to soluble reactive phosphorus (DIN/SRP) declined gradually during the phytoplankton bloom period, especially the ratio of DIN/SRP dropped to 5 ± 7 in August 2013, indicating the nitrogen was limited in lake water. Moreover, the concentration of DON was decreased and a significant negative correlation was observed between DON and Chl-a (r = - 0. 265, P < 0. 05, n = 91), suggesting that DON is bioavailable, and can be utilized by phytoplankton directly or indirectly during nitrogen limitation. No significant difference in DOC concentration was observed and water temperature was the major factor related to the variation of DOC. Chl-a and nitrate concentrations can also affect the dynamics of DOC. In addition, the ratio of DOC/DON was considerably varied, the concentration of DON contributed to the variation of DOC/DON, and DON was the major component contributed to the bioavailability of DOM.

Tanshinone IIA is a lipophilic abietane diterpene compound, which exhibits protective effects against ischaemia/reperfusion injury; however, the pathways responsible for the myocardial protective activities of tanshinone IIA remain to be elucidated. The aim of the present study was to investigate the effect of tanshinone IIA on the Janus‑activated kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway, which is associated with cardiac dysfunction during ischemia/reperfusion. The results demonstrated that tanshinone IIA protected myocardial cells from hypoxia/ischemia‑induced injury in vitro and recovered decreased cell viability due to activation of the JAK2/STAT3 pathway, with 10 µM tanshinone IIA exhibiting the most potent protective effects. Flow cytometric analysis revealed that tanshinone IIA reversed the apoptotic aggravation induced by JAK2/STAT3 inhibitors following hypoxic ischemia. However, JAK2 inhibitors promoted the myocardial protective effect of tanshinone IIA from hypoxic‑ischemic injury. Furthermore, tanshinone IIA and JAK2/STAT3 inhibitors in combination augmented the protection of myocardial cells from apoptosis induced by ischemia/reperfusion preconditioning in vivo. In conclusion, the results of the present study indicated that JAK2/STAT3 inhibitors may enhance the protective effect of tanshinone IIA on cardiac myocytes from hypoxic ischemia-induced injury, therefore suggesting that JAK2/STAT3 inhibitors may have a potential application in combination therapies with tanshinone IIA.