MacLeod Carey, Desmond

The use of different N-heterocyclic carbene (NHC) as dative ligands benefits from their capabilities ranging from strong to weak σ-donor according to the Tolman electronic parameter (TEP), well spread in the formation of monometallic complexes, and recently extended to metallic nanocluster and surfaces. Here, we set to explore the role of relativistic effects in determining the stabilization of the dative carbon–metal bond on coinage metal complexes given by NHC-MCl species (M = Cu, Ag, Au), by quantifying their contribution to the different terms related to the bond formation by comparing scalar relativistic and non-relativistic DFT calculations. Our results show a strong contribution to the stabilization of the NHC-M bond, increasing along with the group, from the lighter Cu atom (7.9%) to Ag (15.3%), and most notoriously for the heavier member, Au (39.9%). This observation is similar along the different stabilizing terms related to the C-M bond, where the acceptor character of the metal center is affected, resulting in a stronger σ-donor interaction from the involved ligand. Thus, the theoretical evaluation of carbon–metal bonds requires the equal footing treatment of relativistic effects along with the group, which is beneficial for the theoretical evaluation of ligand capabilities prior to the engaging exploration of the efficient formation of related complexes involving lighter to heavy metallic centers.

The hydrogen storage properties of Ti-doped Bn ((Formula presented.)) clusters are investigated by using the “diatomic deposition method” with further evaluation by density functional theory computations. The results show that TiBn ((Formula presented.)) clusters possess the ability to storage up to four H2 molecules, reaching a mass fraction of 6.12%. Further, the hydrogen release temperature is analyzed by molecular dynamics simulations with a variable temperature. It turns out that the TiB7 and TiB9 clusters release the H2 molecules at T ≲ 700 K, while TiB8 requires higher temperature due to stronger interactions with the H2 molecules, confirmed by the electronic density of states. The size-dependent properties and odd–even nuclearity on the clusters can be useful for applications with controlled temperature. These results serve for further design of novel materials with reversible and controlled hydrogen storage properties based on TiB7/TiB9 motifs. Additionally, new lower-energy isomers for TiB4 and TiB9 clusters were found within the accuracy of the all-electron triple-ζ Slater [slater type orbital (STO)-Triple-zeta basis set(TZP)] basis set.