Carbyne, the elusive sp-hybridized linear allotrope of carbon, is a controversial material (Fig. a). It has fascinated scientists for decades because it ought to exist but all claims of its synthesis and identification in meteorites have turned out to be dubious. Many attempts have been made to prepare structures consisting exclusively of sp-carbon, either in linear or cyclic form. However, their inherent instability in a pristine form seems to result in immediate decomposition under standard conditions. Linear polyynes with enormous end-capping protective groups are, so far, the best isolable model system for carbyne. Wesley Chalifoux and Rik Tykwinski managed to make the longest known linear polyyne with 44 sp carbon atoms (22 consecutive triple bonds, Nature Chem. 2010, 2, 967). The Fritsch-Buttenberg-Wiechell (FBW) rearrangement is a valuable synthetic tool in the synthesis of these long molecular wires. In this rearrangement the 1,1-dibromoolefin is transformed undergoing a 1,2-shift to an acetylene upon treatment with a strong reducing agent (Fig. b).
The chemical and structural complexity of crystalline metal-organic frameworks (MOFs), which are network architectures formed from linked inorganic and organic components, presents great challenges for their characterization. Recently, one family of MOFs have been shown to melt (without decomposition), and form glasses upon quenching of the resultant liquids. The arrangements of atoms in these liquids and glasses are, by their nature, highly disordered and lack a unit cell. They are thus even more demanding to characterize than their crystalline counterparts.