Ling Jiang

A series of heterotrinuclear carbonyl clusters TiNi2(CO)n– (n = 3–5) have been produced by a laser sputtering supersonic cluster ion source and probed by a velocity-map photoelectron imaging spectrometer. Theoretical calculations have been executed to probe the structures and assist the experimental spectral assignments. At n = 3, an intriguing trigonal pyramidal Ti–Ni–Ni–C motif is formed with two μ2-bridging CO ligands and one μ3-bridging CO ligand, which is retained in the most stable structures of larger clusters. For n = 4 and 5, the additional CO ligands are separately bound to each Ni atom in a terminal coordination mode. C–O bond activation is found to increase systematically with the binding motif of metal–CO coordination: terminal < μ2-bridging < μ3-bridging coordination. The present findings elucidate the bonding mechanism in the heteronuclear metal clusters at the molecular level and provide microscopic insights into metal–CO interactions in heterometallic systems.

Triadimefon is a widely used systemic triazole fungicide, yet its heat capacity and enthalpy of solution, which are key thermodynamic data for reactor heat transfer design, formulation process optimization, and environmental fate modeling, remain unreported. Herein, the molar heat capacity (Cp,m) of triadimefon was measured by differential scanning calorimetry (DSC) using the sapphire three-step method over the range 283.15–333.15 K. The temperature dependence of Cp,m is well described by a cubic polynomial, and Cp,m at 298.15 K is 359.23 J mol–1 K–1. The thermodynamic functions HT – H298.15 K and ST – S298.15 K were derived from the experimental heat-capacity data. These quantities, together with Cp,m, were also calculated by density functional theory. The calculated values are slightly lower than the experimental ones, with relative deviations ranging from 8.70 to 10.25%. To further understand its solution behavior, the dissolution of triadimefon in N,N-dimethylformamide was investigated at 298.15 K. The process is endothermic, with a molar dissolution enthalpy of 15.71 ± 0.13 kJ mol–1. An empirical relationship between dissolution enthalpy and molality is established, with the dissolution kinetics described by dαdt=10−2.42(1−α)0.80. The present thermochemical and kinetic results of triadimefon afford reliable bases of physical and chemical properties for formulation development, recrystallization process optimization, and environmental behavior assessment.

The structural transition from clustered water molecules to the hydrogen-bonding networks of bulk liquid defines one of the most fundamental problems in physical chemistry, yet the precise size at which the endohedral cages emerge remains experimentally elusive. While theory has long predicted that a fully encapsulated water molecule requires a minimum of 16–23 surrounding molecules, direct experimental identification has been hindered by the difficulty of size selection of neutral clusters. Using infrared spectroscopy coupled to vacuum-ultraviolet threshold photoionization, we provide the first experimental evidence that (H2O)17 forms the smallest water endohedral cage, achieving a decades-standing goal of establishing the molecular limit of a solvation shell. Surprisingly, the oxygen framework of this (H2O)17 cage defines an unprecedented, nonclassic polyhedron with four tetragonal, four pentagonal, and two hexagonal faces that breaks the symmetry constraints of all classical Platonic, Archimedean, and Johnson solids. This work establishes a critical structural precursor to the hydrogen-bonding network topology observed in condensed-phase water and offers new perspectives at the multidisciplinary sciences of mathematics, materials, physics, and chemistry.

Ammonia synthesis under mild conditions remains challenging because of the inertness of the N≡N bond and the limited ability of conventional catalysts to couple efficient dinitrogen activation with rapid hydrogenation. Here, we report a LiH/FePcG catalyst in which strong interfacial coupling between LiH and Fe–N–C sites enable efficient ammonia synthesis. Comprehensive characterization, including structural analysis, kinetic study, isotopic-labelling, gas-phase mass spectrometry, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveal that the catalytic activity originates from interfacial active sites. Under reaction conditions, structural nitrogen atoms within the Fe–Nx moieties undergo reversible consumption and reconstruction, demonstrating the dynamic participation of the Fe–N–C framework in ammonia synthesis. Concurrently, hydridic hydrogen supplied by LiH directly participates in the initial hydrogenation steps, while the LiH/Fe–N–C interface generates Fe-centered multicomponent hydride species essential for N2 binding and activation. An inverse H/D kinetic isotope effect, an H2-promoted 28N2/30N2 exchange rate, in situ spectroscopic evidence, and density functional theory (DFT) calculations collectively support a non-classical, hydrogen-assisted pathway for dinitrogen activation rather than the conventional direct N≡ bond cleavage. These findings establish interfacial hydride chemistry as a cooperative mechanism for efficient ammonia synthesis and provide a strategy for designing advanced catalysts under mild conditions.

Investigation of the interactions of methane with metal oxides is crucial for elucidating absorption configurations at active sites of catalysts, which has proven to be a challenging experimental target due to the difficulty in size selection of neutral systems. In this work, the interactions of methane with rare earth metal oxides are studied by using size-specific infrared-vacuum ultraviolet spectroscopy and quantum chemical calculations. Two distinct configurations of methane adsorption are found in the MO(CH4)n (M = Ce, Y; n = 1–3) complexes. In the first configuration, the C and H atoms of methane are positioned between a Lewis acid-base pair (M2+–O2−); in the second configuration, one H atom of methane is oriented toward a Lewis basic oxygen anion (O2−). Such adsorption features of methane on cerium and yttrium monoxides are dominantly governed by electrostatic interactions. These findings provide key microscopic information for methane adsorption on metal oxides that are helpful for understanding the crucial initial steps in the catalytic cycles.

Multiple bonds involving the main-group element represent a prominent class of interactions whose formation and cleavage involve substantial electron redistribution, yet its functional role in redox processes remains unexplored. Herein, we identify a triple-bond character in the RhC– anion, which was generated in the gas phase and characterized spectroscopically by mass spectrometry and photoelectron spectroscopy. Concurrently, the RhC– species is demonstrated to exhibit dinitrogen cleavage capability. Quantum chemical calculations reveal that the resulting products feature a pronounced weakening of the Rh–C interaction along with concomitant C–N bond formation. Electronic structure analysis further indicates that the Rh–C triple bond acts as an electron reservoir, and nitrogen reduction proceeds primarily through cleavage of the Rh–C bond, which releases stored electrons. This work establishes the functional application of metal–carbon multiple bonds in dinitrogen cleavage, demonstrating their unique capacity to couple structural dynamics with redox chemistry and thereby establishing a transformative mechanism for designing electron-reservoir catalysts in dinitrogen activation and beyond.

Elucidating the water splitting by neutral metals is crucial for understanding the structure–reactivity relationship of catalysts. However, experimental characterization of such neutral metal–water systems remains extremely challenging due to the difficulty in mass selection. Herein, the reactions of neutral tantalum with water were studied by size-specific infrared-vacuum ultraviolet spectroscopy with the combination of quantum chemical calculations and ab initio molecular dynamics simulations. The agreement between experimental and theoretical results identifies the key products of stepwise solvated hydrides HTa(OH)3(H2O)n (n = 1–3). The n = 1 monohydrate is stabilized by a cyclic double hydrogen bond motif between the HTa(OH)3 core and the water molecule, while subsequent hydration (n = 2 and 3) progressively extends this hydrogen bond network to form the first solvation shell. Significantly, the first water molecule in TaO(H2O)n inhibits the water dissociation reaction on TaO, whereas the second water molecule in TaO(H2O)n is able to trigger the water splitting facilitated by a six-membered hydrogen bond network. This work provides the direct spectral evidence of intrinsic structure and solvation effect of hydrolysis products and offers a molecular-level prelude to the macroscopic mechanism of single-atom catalysts for water splitting.

In vacuum ultraviolet (VUV) lamp-based photoionization mass spectrometry (PI-MS), the axially mounted configuration exhibits higher sensitivity due to a longer light absorption path. However, VUV light irradiation of the metal surfaces within the transmission chamber induces photoelectron emission; excessive background gas ions are generated via photoelectron ionization under the radio frequency (RF) electric field, which affects the quantitative performance and repeatability of PI-MS, especially for deuterium lamps with a higher photon flux. In this study, a size- and position-adjustable baffle electrode was integrated into the ionization chamber to reduce the light leakage into the transmission chamber. For a 3 mm-diameter baffle positioned 5.4 mm from the skimmer, the intensity of background gas ions generated in the transmission chamber decreased to 1/506, while the intensity of the trichloroethylene ion was maintained at half that without the baffle. The intensities of chlorinated hydrocarbon ions were enhanced by 9-fold compared with the SPI mode when an RF voltage was further applied to the baffle electrode, under which the dominant ionization process was Penning ionization (PenI). Surprisingly, the intensities of chlorinated hydrocarbon ions did not decrease but increased by up to 126% compared to those without the baffle. Simulation of the electric field distribution and electron kinetic energy highlights that the precise overlap of the ion generation region and efficient transmission region plays a pivotal role in the regulation of spatially confined PenI toward sensitivity improvement. This approach has achieved limits of detection down to sub-pptv, even for molecules with ionization energies higher than the photon energy.

Gas-phase heteronuclear cerium-nickel carbonyl complexes, OCeNi(CO)₃^- and CeNi(CO)₃^-, were successfully synthesized and characterized via mass-selected infrared photodissociation spectroscopy in combination with global minimum energy searches. The agreement between experimental and theoretical spectra reveals the coexistence of multiple isomers, different from single-structured iron carbonyl analogues. Besides, these complexes possess the shortest Ce-Ni bond and a relatively higher bond order reported to date, along with a previously unobserved Ce≡O triple bond. Detailed chemical bonding analyses unravel the formation of multicenter covalent bonds or dative bonds between Ce-based moieties and the Ni(CO)₃^- fragment, highlighting that the Ni 4p (rather than 3d) orbital plays a key role in bonding with the Ce 6s or 5d orbital. Such diverse bonding modes are found to arise from the singly occupied molecular orbital (SOMO) of the Ni(CO)₃^- fragment, whose amphiphilic nature and multiple active sites facilitate interactions with Ce-based moieties. These findings advance the scope of metal-metal bond between f-block elements and transition metals, paving a way for exploring novel heterobimetallic interactions.

Nitrogen fixation is a challenging target in chemistry. N₂ adsorption on transition metal sites has been identified as a prerequisite for activating the stable N≡N triple bond in industrial and biological processes. The structural and bonding properties of the Rh₂O₂(N₂)_n^- (n = 1-2) complexes have been investigated via mass-selected photoelectron velocity-map imaging spectroscopy combined with quantum chemical calculations. The experimental and theoretical results indicate that the N₂ molecules in the Rh₂O₂(N₂)_n^- (n = 1-2) complexes possess the end-on bonding motifs. Adsorption and activation of dinitrogen are facilitated by charge transfer from Rh and O to N₂. The importance of π back-donation from the 4d orbital of the Rh atom to the antibonding π orbitals of N₂ for dinitrogen activation is discussed in detail; these results identify Rh₂O₂(N₂)_n^- (n = 1-2) as a key adsorbed species in the initial stage of dinitrogen activation by rhodium oxide clusters.