Synthetic Approaches toward Molecular and Polymeric Carbon Allotropes

Abstract

Life on earth is based on compounds that have carbon frames and backbones. Today, chemists have added to the world of biomolecules and biopolymers approximately lo7 different synthetic molecules and polymers, the structures of which also depend on the formation of strong, stable carbon-carbon bonds. Although the stability of carbon-carbon bonds has been recognized for more than a century, the two natural modifications graphite and diamond were, until recently. the only allotropic forms of carbon on earth that were available in macroscopic quantities and were structurally well characterized. With the synthesis of macroscopic quantities of buckminsterfullerene (C6,) and the higher fullerenes (C,,, C 7 6 , C,,, etc.) and the exploration of the fascinating properties of these all-carbon spheres, this situation has completely changed. In the coming decades, the design, preparation, and study of novel molecular and polymeric allotropic forms of carbon will be a central topic in chemistry. Research in this area will dramatically advance the fundamental knowledge on carbon-based matter and, as already illustrated by the ongoing work on C,, , generate unprecedented technological perspectives. This review surveys synthetic organic-chemical approaches toward the preparation and study of all-carbon molecules and polymers that differ from the familiar networks of graphite and diamond as well as from the fullerenes. We will also discuss the ongoing research on fullerenes with a particular focus on the synthetic approaches to these all-carbon spheres and their transition metal complexes.

Synthesis and Characterization of Novel Chiral Conjugated Materials

“…com pared with fullerenes) was fi rst considered by Riley and coworkers, in their stud ies of amorphous carbon. However, this structure remains experimentally elusive [104][105][106].…”

Functional acetylenic molecular architecture

“…These efforts have greatly benefited from the recent renaissance in preparative acetylene chemistry [1] and, in particular, from the discovery of novel metal-catalyzed cross-coupling reactions for C-C bond formation [2]. A rich variety of peralkynylated building blocks have been prepared as starting materials in this modular synthetic approach to new advanced materials [3][4][5][6] and, among these, derivatives of tetraethynylethene (1, TEE, 3,4-diethynylhex-3-ene-1,5-diyne) [7][8][9] are particularly useful. Today, TEEs of nearly any desired functionalization and silyl-protection are available.…”

Synthesis of 1,3-diynes via detelluration of bis(ethynyl)tellurides

“…Among these compounds, 1,3-butadiynes 6 have been prominently utilized as substructures in the formation of valuable intermediates for natural products 7 and pharmaceuticals such as antitumor, 8 antibacterial, 9 anti-inflammatory, 10 and antifungal agents. 11 These conjugated diynes also serve as the core functional group in organic molecular materials such as linearly σ-conjugated acetylenic oligomers and polymers, 12 macrocycles 13 (Figure 1), and supramolecular scaffolds. 14 Oxidative dimerization of sp-hybridized terminal alkynes mediated by Cu(I) or Cu(II) salts under either catalytic or stoichiometric conditions is the most commonly used synthetic methodology for obtaining symmetrically substituted 1,3-butadiyne.…”