Platinum clusters Pt _n ^+/0/- (n = 3-21): from triangles to remarkable tubular architectures

This paper reports on a theoretical investigation of Pt _n ^+/0/- clusters with n = 3-21 in three-charge states using density functional theory with the B3PW91 functional in conjunction with the aug-cc-pVTZ-PP and Def2-TZVP basis sets. Geometric structures of Pt _n ^+/0/- in the small-to-medium size range are primarily derived from Pt₆ ^+/0/-; whereas Pt₁₀ ^+/0/-, Pt₁₄ ^+/0/- and Pt₁₈ ^+/0/- also emerge as building blocks. The sizes Pt₄, Pt₆, Pt₁₀ and Pt₁₈ emerge as magic clusters, in part in agreement with experimental mass spectrometry. Tubular Pt structures are identified at the sizes of Pt₁₂, Pt₁₈ and Pt₂₄ clusters that can be constructed by either stacking planar Pt₆ or assembling prismatic Pt₆ units. These tubular configurations are energetically favorable and present an effective pathway for the design of more complex Pt-based nanostructures. The Pt₆ triangle features six σ bonds, six conjugated π-bonds of (2c-1e) delocalization and six (6c-1e) bonds reflecting a fully SP² hybridization. The Pt₆ prism contains three (6c-1e) bonds and nine σ-bonds from (2c-1e) delocalization, spanning its edges and faces. These delocalized bonds facilitate the structural integrity and connectivity of tubular Pt₁₂, Pt₁₈ and Pt₂₄ isomers. In these tubular clusters, increased bond coordination and redistribution of electron contributions among s, p and d orbitals enhance bonding interactions and promote stabilized structural assemblies.