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 Pt(6) (+/0/-); whereas Pt(10) (+/0/-), Pt(14) (+/0/-) and Pt(18) (+/0/-) also emerge as building blocks. The sizes Pt(4), Pt(6), Pt(10) and Pt(18) emerge as magic clusters, in part in agreement with experimental mass spectrometry. Tubular Pt structures are identified at the sizes of Pt(12), Pt(18) and Pt(24) clusters that can be constructed by either stacking planar Pt(6) or assembling prismatic Pt(6) units. These tubular configurations are energetically favorable and present an effective pathway for the design of more complex Pt-based nanostructures. The Pt(6) triangle features six σ bonds, six conjugated π-bonds of (2c-1e) delocalization and six (6c-1e) bonds reflecting a fully SP(2) hybridization. The Pt(6) 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 Pt(12), Pt(18) and Pt(24) 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.