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Mixed cobalt and manganese oxides embedded in the nanoporous carbon framework (M/MO@C) were synthesized by the direct carbonization of a binary mixed-metal organic framework (CoMn-MOF-74) for the first time. The unique M/MO@C carbon materials maintained the primary morphology of CoMn-MOF-74, and showed a uniform dispersibility of Co, MnO and CoO nanoparticles in the carbon matrix, and therefore greatly increased the conductivity of the M/MO@C materials. A series of M/MO@C samples were tested as the electrode materials for supercapacitors, and a remarkable specific capacitance of 800 F g(-1) was obtained using the M/MO@C-700 sample at a current density of 1 A g(-1) in 6 M KOH electrolyte. Moreover, the M/MO@C sample showed a good cycling stability with a capacitance retention of 85% after 1000 cycles. It is also found that the optimized carbonization temperature is a critical parameter to obtain such a M/MO@C nanoporous carbon framework with the best capacitive performances. The present approach is convenient and reproducible, which could be easily extended to the preparation of other M/MO@C composites with excellent electrochemical performances.

Gold compounds, clusters, and nanoparticles are widely used as catalysts and therapeutic medicines; the interactions between gold and its ligands in these systems play important roles in their chemical properties and functionalities. In order to elucidate the nature of the chemical interactions between Au(I) and its ligands, herein we use several theoretical methods to study the chemical bonding in a variety of linear [AuX2](-) complexes, where X = halogen atoms (F, Cl, Br, I, At and Uus), H, OH, SH, OCH3, SCH3, CN and SCN. It is shown that the most important bonding orbitals in these systems have significant contributions from the Au sd hybridized atomic orbitals. The ubiquitous linear or quasi-linear structures of [AuX2](-) are attributed to the well-balanced optimal overlap in both σ and π bonding orbitals and minimal repulsion between the two negatively charged ligands. The stability of these complexes is related to the covalency of the Au-X bond and a periodic trend is found in the evolution of covalency along the halogen group ligands. The special stability of [Au(CN)2](-) is a result of strong covalent and ionic interactions. For the superheavy element Uus, the covalency of Au-Uus is enhanced through the spin-orbit interactions.

We report an investigation of the electronic structure and chemical bonding of AuH2− using photoelectron spectroscopy and ab initio calculations. We obtained vibrationally resolved photoelectron spectra of AuH2− at several photon energies. Six electronic states of AuH2 were observed and assigned according to the theoretical calculations. The ground state of AuH2− is known to be linear, while that of neutral AuH2 is bent with a ∠H–Au–H equilibrium bond angle of 129°. This large geometry change results in a very broad bending vibrational progression in the photoelectron spectra for the ground-state transition. The electron affinity of AuH2 is measured to be 3.030 ± 0.020 eV. A short bending vibrational progression is also observed in the second photodetachment band, suggesting a slightly bent structure for the first excited state of AuH2. The linear geometry is a saddle point for the ground and first excited states of AuH2, resulting in double-well potentials for these states along the bending coordinate. Spectroscopic evidence is observed for the detachment transitions to the double-well potentials of the ground and first excited states of AuH2. Higher excited states of AuH2 due to detachment from the nonbonding Au 5d electrons are all linear, similar to the anion ground state. Kohn–Sham molecular orbital analyses reveal surprising participation of H 2p orbitals in the Au–H chemical bonding and an unprecedented weak Au 5dπ to H 2pπ back donation. The simplicity of the linear AuH2− anion and its novel spectroscopic features make it a textbook example for understanding the covalent bonding properties and relativistic effects of Au.

Thiolate-protected gold nanoparticles have been found recently to be coordinated by the so-called "staple" bonding motifs, consisting of quasi-linear [RS-Au-SR] and V-shaped [RS-Au-(SR)-Au-SR] units, which carry a negative charge formally. Using photoelectron spectroscopy (PES) in conjunction with ab initio calculations, we have investigated the electronic structure and chemical bonding of the simplest staples with R = CH(3): Au(SCH(3))(2)(-) and Au(2)(SCH(3))(3)(-), which were produced by electrospray ionization. PES data of the two Au-thiolate complexes are obtained both at room temperature (RT) and 20 K. The temperature-dependent study reveals significant spectral broadening at RT, in agreement with theoretical predictions of multiple conformations due to the different orientations of the -SCH(3) groups. The Au-S bonds in Au(n)(SCH(3))(n+1)(-) (n = 1, 2) are shown to be covalent via a variety of chemical bonding analyses. The strong Au-thiolate bonding and the stability of the Au-thiolate complexes are consistent with their ubiquity as staples for gold nanoparticles and on gold surfaces.

We report a combined experimental and theoretical investigation of [XAuCN]− (X = F, Cl, Br, I) to examine the chemical bonding in the mixed cyanide halide Au(I) complexes. Photoelectron spectra are obtained for [XAuCN]−, yielding electron affinities of 5.38 ± 0.05, 5.14 ± 0.05, and 4.75 ± 0.05 eV for XAuCN (X = Cl, Br, I), respectively. Relativistic quantum chemical calculations based on wavefunction theory and density functional theory are carried out to help interpret the photoelectron spectra and elucidate the electronic structures and chemical bonding in the [XAuCN]− complexes. Spin–orbit coupling is found to be important in all the complexes, quenching the Renner–Teller distortion in the neutral molecules. Ab initio calculations including spin–orbit effects allow quantitative assignments of the observed photoelectron spectra. A variety of chemical bonding analyses based on the charge population, bond orders, and electron localization functions have been carried out, revealing a gradual transition from ionic behavior between F–Au in [FAuCN]− to relatively strong covalent bonding between I–Au in [IAuCN]−. Both relativistic effects and electron correlations are shown to enhance the covalency in the gold iodide complex.

Understanding the geometry structures of gold clusters, especially with adsorbates, is essential for designing highly active gold nanocatalysts. Here, we report a detailed theoretical study of the geometry structures of bare and CO-saturated Au(n)(+) (n = 4-6) clusters. It is found that the chemisorption of CO molecules leads to significant geometry changes of the gold clusters from two- to three-dimensions (3D), even for clusters as small as Au(4)(+). These gold cationic clusters exhibit characteristic coordination binding sites that have distinct electronic structures. We also find that commonly used density functional theory (DFT) methods have difficulty in accurately predicting energies of some isomers of Au(n)(+) clusters or Au(n)(CO)(n)(+) complexes, with the calculated relative energies strongly depending on the exchange-correlation functionals used. Caution must be exercised when using DFT methods as a blackbox for predicting the structures and energies of gold clusters.