Anion photoelectron spectroscopy and quantum chemical calculations of bimetallic niobium-aluminum clusters NbAln-/0 (n = 3-12): identification of a half-encapsulated symmetric structure for NbAl12.

Bimetallic niobium-doped aluminum clusters, NbAln-/0 (n = 3-12), are investigated through a synergetic combination of size-selected anion photoelectron spectroscopy and theoretical calculations. It is found that the dominant structures of NbAln- anions with n = 3-8 can be described by gradually adding Al atoms to the NbAl3- core. Starting from n = 9, the lowest-energy geometric structures of NbAl9-12- transform into bilayer structures. In particular, NbAl12- has a C3v symmetric structure, which can be viewed as a NbAl6 regular hexagon over a bowl-shaped Al6 structure. More detailed analyses indicate that NbAl9 and NbAl12- possess unusual stability, which may be attributed to their closed-shell electron configurations with superatomic features.

Role of Au-Sn bonding for stabilizing a gold nanocatalyst: a reinvestigation of purple of Cassius.

Purple of Cassius is a pigment based on a gold colloid that has been known for hundreds of years. It has had a profound influence on modern nanoscience. But the origin of the small size of the Au nanoparticles (NPs) and their superior stability remains ambiguous. The experiments and characterization studies discussed here confirmed that SnCl2 functioned not only as a reducing agent but also as an effective surface capping agent through bimetallic Au-Sn bonding. This finding expands the types of Au NP stabilizer from traditional organic examples (e.g., thiolate or phosphine) to metallic examples. The formation of a Au-Sn interface also endows Au NPs with excellent activity and separability for the hydration of alkynes to ketones.

Anion Photoelectron Spectroscopy and Quantum Chemical Calculations of Bimetallic Oxide Clusters YCu2On-/0 (n = 2-5).

The structural and electronic properties of bimetallic oxide clusters, YCu2On- and YCu2On (n = 2-5), are investigated using anion photoelectron spectroscopy and density functional theory calculations. The experimental vertical detachment energies of YCu2O2-, YCu2O3-, YCu2O4-, and YCu2O5- were measured to be 1.59, 1.76, 3.85, and 3.78 eV, respectively. Vibrationally resolved photoelectron spectra have been obtained for YCu2O2-, with a spacing of 726 ± 80 cm-1 assigned to the Y-O stretching vibrational mode. It is found that YCu2O2- and YCu2O2 have C2v symmetric planar five-membered ring structures. YCu2O3- and YCu2O3 have C2v symmetric planar six-membered ring structures. The most stable structure of YCu2O4- is a quasi-planar structure which can be viewed as one O atom interacting with the Y atom of the YCu2O3 six-membered ring, while the most stable structure of YCu2O4 is a planar seven-membered ring. YCu2O5- and YCu2O5 have nonplanar structures, which can be viewed as an O2 unit interacting with the Y atom of the YCu2O3 six-membered ring. In YCu2O3,4,5-/0, the Y-O and Cu-O bonds are dominant, while the Y-Cu and Cu-Cu interactions are weak.

Probing the electronic structure and Au-C bonding in AuC2nH (n = 4-7) using photoelectron imaging spectroscopy and quantum chemical calculations.

We report a combined experimental and theoretical study on the structures and chemical bonding of AuC2nH (n = 4-7) using photoelectron imaging and quantum chemical calculations. All the ground states of anions and neutral AuC2nH have a linear geometry. The electron affinities (EAs) are measured to be 2.063(5), 2.157(5), 2.220(5), and 2.267(5) eV for AuC2nH, n = 4-7, respectively. The photoelectron imaging data of AuC8H- and AuC10H- reveal major vibrational progressions in the Au-C stretching modes. The ground state stretching frequencies of the titled neutral molecules are 226, 193, 177, and 128 cm-1, respectively. By comparing the experimental ß value and theoretical molecular orbital analysis, we confirm that the CAM-B3LYP method is more suitable for describing the properties of such unsaturated long chains organogold clusters. The experimental and CAM-B3LYP methods give a big picture of the trend in EAs of AuC2nH. This shows that the EA value becomes larger with an increase in the carbon chain length, and it also shows a slow increment for larger n. The NRT analysis shows that the change of the Au-C bond order is not obvious as the number of carbon atoms increases, and the covalent character dominates the Au-C chemical bonds in these neutral species. The current study provides a wealth of electronic structure information about long-chain AuC2nH- (n = 4-7) and their corresponding neutral counterparts.

Anion photoelectron spectroscopy and theoretical calculations of Cu4On -/0 (n = 1-4): Identification of stable quasi-square structure for Cu4O4.

We investigated Cu4On - (n = 1-4) clusters through a synergetic combination of mass-selected anion photoelectron spectroscopy and density functional theory calculations. It is found that the most stable structure of Cu4O- is an irregular planar pentagon with a Cs symmetry. Those of Cu4O2 - and Cu4O3 - are non-planar structures with a Cs symmetry. The global minimum geometry of Cu4O4 - is a D4h symmetric quasi-square eight-membered ring with Cu-O bond lengths of ∼1.78 Å. The molecular orbital analyses suggest that Cu4O4 - has a large highest occupied molecular orbital and lowest unoccupied molecular orbital gap. The chemical bonding analyses and the calculations of the magnetically induced current density, and NICS(0) and NICS(1) values indicate that the D4h structure of Cu4O4 - is very stable and it has some aromaticity.

Structural and Electronic Properties of LaSin-/0 (n = 2-6) Clusters: Anion Photoelectron Spectroscopy and Density Functional Calculations.

The structures and electronic properties of LaSin- (n = 2-6) anions and their neutral counterparts were investigated by anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of the most stable structures of LaSin- (n = 2-6) were measured to be 1.28, 1.58, 2.30, 2.05, and 2.91 eV, respectively. The lowest-energy isomer of LaSi2- is an isosceles triangle with a C2v symmetry. For LaSi3-6- clusters, the most stable isomers are polyhedrons with La atom face-capping the Sin frameworks. The lowest-energy structures of neutral LaSi2,4,5 clusters are similar to their anionic counterparts. The most stable isomer of neutral LaSi3 is a planar structure with C2v symmetry, which is different from the triangular pyramid structure of LaSi3- anion. The lowest-energy isomer of LaSi6- is a C5v symmetric pentagonal bipyramid structure, while for neutral LaSi6 cluster, the C5v structure is not the most stable one. The natural population analysis showed that there is electron transfer from La atoms to Si atoms in LaSin-/0 (n = 2-6). The ZZ tensor component in isochemical shielding surfaces and the anisotropy of the induced current density analyses indicate that the most stable isomer of LaSi6- has aromaticity.

Observation of Aromatic Three-Membered Rings in Ge3C and Ge3O via Photoelectron Spectroscopy and Theoretical Calculations.

The structures and chemical bonding of Ge3C- and Ge3O- as well as their neutrals are explored with anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of Ge3C- and Ge3O- are measured to be 1.51 ± 0.04 and 2.00 ± 0.04 eV, respectively. It is found that Ge3C-/0 have a C2v symmetric planar structure with the C atom interacting with three Ge atoms. Ge3O-/0 have the O atom interacting with two Ge atoms of the triangular Ge3 unit. Ge3O- has a Cs symmetric nonplanar structure, while Ge3O has a C2v symmetric planar structure. Theoretical results show that the multiconfigurational effects in Ge3C-/0 and Ge3O-/0 are insignificant. Chemical bonding analyses reveal that there exist the C-Ge3 π⊥ orbital interaction and two π aromatic Ge2C units in Ge3C. There are O-Ge3 π⊥ orbital interaction and one doubly aromatic Ge3 unit in Ge3O, but the π⊥ orbital interaction is relatively weak.

Bidentate Phosphine-Assisted Synthesis of an All-Alkynyl-Protected Ag74 Nanocluster.

Determining the total structure of metal nanoparticles is vital to understand their properties. In this work, the first all-alkynyl-protected Ag nanocluster, Ag74(C≡CPh)44, was synthesized and structurally characterized by single crystal diffraction. Ag atoms are arranged in a Ag4@Ag22@Ag48 three shell structure and all 44 phenylethynyl ligands coordinated with Ag in a µ3 mode. In spite of being absent in nanocluster, 31P NMR study reveals that bidentate phosphine first reacts with Ag(I) to form a dinuclear complex, from which Ag atoms are then released to phenylethynyl ligands. This phosphine mediated strategy may find general application in synthesis of alkynyl-protected Ag nanoclusters.