Differential Packing of Cs2Mo6Br14 Cluster-Based Halide in Variable Diameter Carbon Nanotubes with Elimination and Polymerization to 1D [Mo2Br6]x Ising Model Structures by Steric Confinement.

We present detailed findings on the imaging, structure, and vibrational properties of novel hybrids of the red-emitting octahedral cluster-based compound Cs₂Mo₆Br₁₄ encapsulated within single-walled carbon nanotubes (SWCNTs) of varying diameter. We explore the subtle relationship between the SWCNT internal diameter and Cs₂Mo₆Br₁₄ cluster packing and find a hierarchical relationship between the nature of the cluster packing and a progressive tendency toward formation of one-dimensional (1D) structures as the SWCNT diameter narrows from 24 to 11 Å. As the internal SWCNT van der Waals radius approaches the outside diameter (OD) of the [{Mo₆^IIBr₈ⁱ}Br₆^a]^2- (more simplistically, [Mo₆^IIIBr₁₄]^2-) molecular anion species, SWCNT steric confinement causes a compositional elimination and polymerization resulting in the formation of reduced extended [Mo₂^IIIBr₆]_x nanoribbons which approximate 1D Ising model structures. Our experimental results, obtained through high-resolution transmission electron microscopy and Raman spectroscopy, are supplemented by density functional theory (DFT) calculations.