Hongtu Zhang

Au-doped PtAgRhCu alloy wavy nanowire electrocatalysts deliver ultrahigh mass activity and selectivity for alcohol oxidation, enabling energy-saving hydrogen production and selective alcohol upgrading via alcohol-assisted water electrolysis.

In this study, we observed that EHEs from different anatomic sites shared some clinicopathological features.

The reactivity of the terminal zirconium(IV) oxo complex, OZr(MesNPⁱPr₂)₃CoCN^tBu (2), is explored, revealing unique redox activity imparted by the pendent redox active cobalt(I) center. Oxo complex 2 can be chemically reduced using Na/Hg or Ph₃C^• to afford the Zr^IV/Co⁰ complexes [(μ-Na)OZr(MesNPⁱPr₂)₃CoCN^tBu]₂ (3) and Ph₃COZr(MesNPⁱPr₂)₃CoCN^tBu (4), respectively. Based on the cyclic voltammogram of 2, Ph₃˙ should not be sufficiently reducing to achieve the chemical reduction of 2, but sufficient driving force for the reaction is provided by the nucleophilicity of the terminal oxo fragment and its affinity to bind Ph₃C⁺. Accordingly, 2 reacts readily with [Ph₃C][BPh₄] and Ph₃CCl to afford [Ph₃COZr(MesNPⁱPr₂)₃CoCN^tBu][BPh₄] ([5][BPh₄]) and Ph₃COZr(MesNPⁱPr₂)₃CoCl (6), respectively. The chemical oxidation of 2 is also investigated, revealing that oxidation of 2 is accompanied by immediate hydrogen atom abstraction to afford the hydroxide complex [HOZr(MesNPⁱPr₂)₃CoCN^tBu]⁺ ([9]⁺). Thus it is posited that the transient [OZr(MesNPⁱPr₂)₃CoCN^tBu]⁺ [2]⁺ cation generated upon oxidation combines the basicity of a nucleophilic early metal oxo fragment with the oxidizing power of the appended cobalt center to facilitate H-atom abstraction.

A reduced Zr^IV/Co^−I heterobimetallic complex facilitates the formation of 1,3-enynes from terminal alkynes through a cooperative bimetallic C–H activation process.

Herein we report the development of diffusion ordered NMR spectroscopy (DOSY) for its use to characterize metal complexes containing paramagnetic first row transition metal elements.

Oxygen reduction is a critical half reaction in renewable fuel cell development and a key step in the development of aerobic oxidation reactions. Herein, we report rapid two-electron O₂ reduction by a d⁰ Zr^IV center with an appended redox-active Co^–I site serving as an electron reservoir. The early/late heterobimetallic Zr/Co complex (THF)Zr(MesNPⁱPr₂)₃CoCN^tBu (1) reacts readily with O₂ and O atom transfer reagents to generate reactive oxygenated species including terminal peroxo and oxo complexes, (O₂)Zr(MesNPⁱPr₂)₃CoCN^tBu (2) and O≡Zr(MesNPⁱPr₂)₃CoCN^tBu (3). The bimetallic Zr/Co complex provides a new cooperative synthetic pathway to promote multielectron redox processes such as oxygen reduction, with each metal playing a distinct role as a substrate binding site or redox mediator.

Direct analysis of highly reactive volatile species such as the aliphatic aldehydes as vital biomarkers remains a great challenge due to difficulties in the sample pretreatment. To address such a challenge, we herein report the development of a novel double-region atmospheric pressure chemical ionization mass spectrometry (DRAPCI-MS) method. The DRAPCI source implements a separated structural design that uses a focus electrode to divide the discharge and ionization region to reduce sample fragmentation in the ionization process. Counter-flow introduction (CFI) configuration was adopted in the DRAPCI source to reduce background noises, while ion transmission efficiency was optimized through simulating the voltage of focus electrode and the ion trajectory of the ion source. The limits of detection (LODs) of four carbonyl compounds cyclohexanone, hexanal, heptanal, and octanal by DRAPCI-MS were between 0.1 and 3 μg·m-3, approximately two to eight times lower than those by atmospheric pressure chemical ionization mass spectrometry. Additionally, the DRAPCI-MS method carried out effective in-situ analyses of the volatile components in expired milk and the exhaled breath of smokers, demonstrating the DRAPCI-MS a practical tool to analyze complex mixtures. The DRAPCI-MS method provides a rapid, sensitive, and high-throughput technique in the real-time analysis of gaseous small-molecule compounds.

Two new ligand sets, ^pipMeLH₂ and ^NO2LH₂ (^pipMeL = N,N′-bis(2,6-diisopropylphenyl)-1-methylpiperidine-2,6-dicarboxamide, ^NO2L = N,N′-bis(2,6-diisopropyl-4-nitrophenyl)pyridine-2,6-dicarboxamide), are reported which are designed to perturb the overall electronics of the copper(III)–hydroxide core and the resulting effects on the thermodynamics and kinetics of its hydrogen-atom abstraction (HAT) reactions. Bond dissociation energies (BDEs) for the O–H bonds of the corresponding Cu(II)–OH₂ complexes were measured that reveal that changes in the redox potential for the Cu(III)/Cu(II) couple are only partially offset by opposite changes in the pK_a, leading to modest differences in BDE among the three compounds. The effects of these changes were further probed by evaluating the rates of HAT by the corresponding Cu(III)–hydroxide complexes from substrates with C–H bonds of variable strength. These studies revealed an overarching linear trend in the relationship between the log k (where k is the second-order rate constant) and the ΔH of reaction. Additional subtleties in measured rates arise, however, that are associated with variations in hydrogen-atom abstraction barrier heights and tunneling efficiencies over the temperature range from −80 to −20 °C, as inferred from measured kinetic isotope effects and corresponding electronic-structure-based transition-state theory calculations.