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 [{Mo6IIBr8i}Br6a]2- (more simplistically, [Mo6IIIBr14]2-) molecular anion species, SWCNT steric confinement causes a compositional elimination and polymerization resulting in the formation of reduced extended [Mo2IIIBr6]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.