Onset of Carbon−Carbon Bonding in Ta5Cy(y= 0−6) Clusters: A Threshold Photoionization and Density Functional Theory Study

Structural Determination and Bonding Properties of Gas-Phase Ternary [O, Ta, 2C]- Anions

A combined anion photoelectron spectroscopic and quantum chemical investigation was performed to explore the structures and bonding properties of ternary [O, Ta, 2C]^- anions. The atomic bonding connectivity of the ternary anion was found to be (O-Ta-C₂)^- rather than (Ta-O-C₂)^-. The photoelectron spectrum using 266 nm photons was measured, and the theoretical simulated spectrum was calculated, with good agreement between experimental and theoretical results being found. Computations obtained electronic energies and low-energy structures and enabled chemical bonding analyses. The experimental vertical detachment energies of OTaC₂^- were measured to be 2.85 ± 0.08 eV. OTaC₂^- exhibits π aromaticity with two delocalized π electrons and σ antiaromaticity.

Ti12C68: A stable T h -symmetry hollow cage

A stable T h -symmetry Ti12C68 cage was systemically investigated using density functional theory. The structure of Ti12C68 is a hollow cage with twelve TiC13 subunit of three pentagons and one hexagon. The calculated frequencies are in the range 95.1 cm-1-1423.9 cm-1. There are no imaginary frequencies, showing its kinetic stability. Ab initio molecular dynamics simulations demonstrate that the topological structure of cage-like Ti12C68 cluster was well maintained when the effective temperature is up to 1139 K. The natural bond orbitals analysis shows that the d orbit of Ti atoms form four σ bonds with the neighboring four carbon atoms in each TiC13 subunit playing an important role in the cluster stability. The molecular frontier orbitals analysis indicates that Ti12C68 cage has a narrow HOMO-LUMO gap with metal-like property. It would be expected to enrich the species of hollow metal carbide clusters.

Unusual Bonding in Platinum Carbido Clusters

Vibrational spectroscopy and density functional theory calculations are used to determine the structures of small gas-phase platinum carbido clusters PtnC(+), n = 3-5. The carbon atom is found to prefer three-coordinate binding sites near the center of the cluster, in contrast to most previously investigated adatoms on transition metal clusters. The Pt3C unit is particularly stable, and binding of the carbon atom also leads to significant rearrangement of the metal framework when compared to the bare clusters.