Nanoarchitecture through Strained Molecules: Cubane-Derived Scaffolds and the Smallest Carbon Nanothreads

Abstract

Relative to the rich library of small-molecule organics, few examples of ordered extended (i.e., nonmolecular) hydrocarbon networks are known. In particular, sp 3 bonded, diamond-like materials represent appealing targets because of their desirable mechanical, thermal, and optical properties. While many covalent organic frameworks (COFs)extended, covalently bonded, and porous structureshave been realized through molecular architecture with exceptional control, the design and synthesis of dense, covalent extended solids has been a longstanding challenge. Here we report the preparation of a sp 3 -bonded, low-dimensional hydrocarbon synthesized via high-pressure, solid-state diradical polymerization of cubane (C 8 H 8 ), which is a saturated, but immensely strained, cage-like molecule. Experimental measurements show that the obtained product is crystalline with three-dimensional order that appears to largely preserve the basic structural topology of the cubane molecular precursor and exhibits high hardness (comparable to fused quartz) and thermal stability up to 300 °C. Among the plausible theoretical candidate structures, one-dimensional carbon scaffolds comprising six-and four-membered rings that pack within a pseudosquare lattice provide the best agreement with experimental data. These diamond-like molecular rods with extraordinarily small thickness are among the smallest members in the carbon nanothread family, and calculations indicate one of the stiffest one-dimensional systems known. These results present opportunities for the synthesis of purely sp 3 -bonded extended solids formed through the strain release of saturated molecules, as opposed to only unsaturated precursors.

‘Sacrificial’ supramolecular assembly and pressure-induced polymerization: toward sequence-defined functionalized nanothreads

“…14 Such sp 3 -based backbones are theorized to possess the strength of diamond, 22 the chemical versatility of graphene, and large insulating band gaps. 23 In contrast to simple molecules (e.g., benzene) under pressure, polymerization of this co-crystal produced ordered nanothreads even under fast compression. Despite an electronically-biased preorganization, the pressure needed for reaction was still quite high, ca.…”

Decagram Synthesis of Dimethyl 1,4-Cubanedicarboxylate Using Continuous-Flow Photochemistry

“…Recently, cubane and cubane dicarboxylic acid have been used in the synthesis of carbon nanothreads and metallic organic frameworks. 4,5 In addition, 1,4-disubstituted cubanes have found interest as non-aromatic rigid spacers in organic materials and polymers. [6][7][8] Recently, cubanes have been the subject of much interest in medicinal chemistry.…”

“…The first synthesis of 1 involved 8 steps (Scheme 1), 1 starting with a 2-step tribromination of cyclopentenone (2) using N-bromosuccinimide (NBS) and molecular bromine. The tribromocyclopentanone (4) was subjected to a double dehydrobromination to give 2-bromocyclopentadienone (5), that spontaneously dimerised to give 6. This [4+2] Diels-Alder cycloaddition occurs with complete regio-and endo-selectivity.…”

The effect of doping on the electronic structure and optical properties of silicon biprismanes: DFT and TD-DFT studies

“…Besides interest to SPPs itself, they are considered as promising building blocks for novel materials with more complicated structures. Carbon analogous of SPPs [14] are embedded into some new diamond-like allotropes [15,16] and form stable 1D [17,18], 2D [19,20] and 3D [18,21] structures. Similarly, SPPs can produce a family of silicon clusters and crystal forms with different dimensionalities.…”