Elad Shabtai

Dianions and Tetraanions of Bowl-Shaped Fullerene Fragments Dibenzo[a,g]corannulene and Dibenzo[a,g]cyclopenta[kl]corannulene

The fullerene fragment 1 (C28H14) gives a paratropic dianion and a diatropic tetraanion on alkali metal reduction, whereas the C30H14 hydrocarbon 2, which contains just one more ring from the C60 network, gives a diatropic dianion and a paratropic tetraanion.

π‐Conjugated Anions: From Carbon‐Rich Anions to Charged Carbon Allotropes

Stable π-conjugated anions are formed in the reaction of π-conjugated systems with alkali metals. Reactivity, aromatic properties and aggregation of the anions are described. Bowl-shaped and fullerene anions, as well as helicene and planar polycyclic anions, are discussed vis-a-vis their aromaticity and charge delocalization pattern.

Self-diffusion measurements of polycyclic aromatic hydrocarbon alkali metal salts

The solvations of various polycyclic aromatic hydrocarbon alkali metal salts are studied using their self-diffusion rates measured by NMR spectroscopy. The moiety size is more dependent on the anion than the cation. The self-diffusion rates of the neutral compounds are found to be predictable while the salts diffuse considerably slower than the unsolvated species indicating the presence of a solvent shell. The apparent moiety size is temperature dependent for the salts in ethereal solutions indicating a solvation shell of varying size.

Charged cyclophanes with extended conjugation: the effect of the cyclophane hub on the charge distribution

Compounds 1, 2 and 3 were chemically reduced with lithium, sodium and potassium metals in [2H8]THF at 220 K. In each case the reversibility of the process was tested by quenching with molecular oxygen. The reduction of 1 with all three metals yields the corresponding tetraanion salt 14–/4M+. Compound 2 was reduced reversibly with potassium and sodium only, while compound 3 underwent decomposition. According to the UV–VIS spectra and the electrochemical results, the tetraanion species is formed via a stepwise four-electron transfer process. A strong effect of the cyclophane hub on the charge distribution visavis a relevant model system is demonstrated.

Charged paracyclophanes behave as annulenes with enhanced anisotropy

Paracyclophanes, in which benzene units are linked at the 1,4 positions by ethylene bridges (1–4), show annulene characteristics upon charging. The dependence of the magnetic properties of these charged rigid systems on the number of π-electrons in the peripheries has been studied systematically. For the first time it can be shown that upon extensive reduction, two observable diatropic anionic stages exist (for 3). The results of advanced DFT calculations are in line with the experimental results. The limit on the number of π-electrons in the periphery of annulenes, which still exhibit aromatic or anti-aromatic behavior, is extended far beyond the number of 26. p

Isotope shifts in polycyclic aromatic hydrocarbon anions

Isotope shifts are a well established tool for structural analysis by NMR. The substitution of a proton with a deuterium is the most widely studied of these effects. We have synthesized all three monodeuterated anthracenes and shown that their 13C spectra provide the same information that can be obtained from perdeuterated anthracene. The isotope shifts change when the PAH is reduced by an alkali metal. For a planar molecule such as anthracene, the isotope shifts change in approximate proportion to the change in charge density. However, when there is steric hindrance, such as in chrysene, reduction weakens the framework, allowing conformational change that substantially alters the isotopic shifts.

Substituted [24]paracyclophanes

Synthesis, characterization and stereochemistry of new derivatives of [24]paracyclophane, containing carboxylic acid ester groups, are described.