Renata Sygula

Spectroscopic study of a representative polar cap of buckminsterfullerene: Cyclopentacorannulene

The spectroscopic properties of corannulene and cyclopentacorannulene are examined by use of absorption and steady-state fluorescence measurements. A red shift in the emission maxima of cyclopentacorannulene is noted with respect to the emission maxima in the corannulene spectrum. Similar differences in the absorption spectra of both molecules are also observed. Reasons for the dissimilarities in the absorption and emission spectra of these molecules are discussed. The fluorescence quantum yields and lifetimes of the molecules measured in organic solvents are reported. The fluorescence quantum yield and lifetime of cyclopentacorannulene are lower than those of corannulene. This difference is attributed to the highly strained and nonplanar structure of cyclopentacorannulene. The effectiveness of nitromethane as a quencher of corannulene and cyclopentacorannulene fluorescence is examined. In contrast to previously reported results, the fluorescence of these molecules is quenched by nitromethane. Fluorescence quenching of the molecules has been attributed to complex formation in the ground state, i.e., static quenching.

Concerning the structure of the corannulene tetraanion.

Abstract The question of an anion within an anion structure for corannulane tetraanion is examined by ab initio and semi-empirical calculations, as well as by the behavior of corannulene anionic intermediates in anhydrous ammonia. Calculations do not lend much support to a central cyclopentadienyl anion in the tetraanion, and a tetraanion is either not formed or does not resist protonation in liquid ammonia.

2-Trimethylsilylcorannulenyl Trifluoromethanesulfonate: An Efficient Precursor for 1,2-Didehydrocorannulene

2-Trimethylsilylcorannulenyl trifluoromethanesulfonate, prepared from bromocorannulene, provides a means for generating of 1,2-didehydrocorannulene (corannulyne) under very mild conditions as demonstrated by the high-yield formation of its adducts with dienes.

1,2,5,6-Tetraketopyracene : synthesis, and structure by ab initio calculation and X-ray analysis

Abstract The title compound is conveniently synthesized from the known 1,2-diketopyracene via NBS bromination followed by reaction with silver nitrate in acetonitrile, and treatment with sodium acetate trihydrate in DMSO. Its structure determined by semiempirical PM3 and ab initio calculations is in excellent agreement with the x-ray analysis, and suggests that the bond alternation observed in pyracylene and related compounds is probably not due to antiaromaticity.

Bowl stacking in curved polynuclear aromatic hydrocarbons: crystal and molecular structure of cyclopentacorannulene

Cyclopentacorannulene (dibenzo[ghi,mno]cyclopenta[cd]fluoranthene) exhibits long-range concave–convex bowl stacking in the crystal; its molecular structure is satisfactorily described by ab initio calculations at both HF/3-21G and HF/6-31G* levels.