Carola Koper

Terrestrial and Extraterrestrial Fullerenes

Abstract This paper reviews reports of occurrences of fullerenes in circumstellar media, interstellar media, meteorites, interplanetary dust particles (IDPs), lunar rocks, hard terrestrial rocks from Shunga (Russia), Sudbury (Canada) and Mitov (Czech Republic), coal, terrestrial sediments from the Cretaceous‐Tertiary‐Boundary and Permian‐Triassic‐Boundary, fulgurite, ink sticks, dinosaur eggs, and a tree char. The occurrences are discussed in the context of known and postulated processes of fullerene formation, including the suggestion that some natural fullerenes might have formed from biological (algal) remains.

Redox properties of non-alternant cyclopenta-fused polycyclic aromatic hydrocarbons: The effect of peripheral pentagon annelation

The redox properties of 23 alternant PAH and non-alternant mono- and bis-CP-PAH that contain annelated peripheral pentagons were determined using cyclic voltammetry. The results show that peripheral cyclopenta-fusion markedly enhances their electron affinity. Unexpectedly for the non-alternant PAH, a good linear correlation between the first reduction potential [E1/2(0/−1) V vs. SCE] and their standard Huckel LUMO energy (−eLUMO/β) is found. This indicates that the peripheral pentagons perturb the LUMO of the original alternant PAH core in a systematic fashion. A survey of the reduction behaviour of the mono- and bis-CP-PAH reveals that upon reduction the effect of the cyclopenta-moiety on the remainder of the molecule becomes negligible. Evidence for the formation of 6π-electron cyclopentadienide sub-structures is obtained, i.e. localization of the added electrons in the peripheral pentagons occurs.

Externally-fused cyclopenta moieties in non-alternant CP-PAHs act as peri-substituents

Abstract The Hammett constants σ m for the externally fused cyclopenta moiety in the CP-PAHs 1 (1,8-CP), 2 (1,9-CP), 3 (1,10-CP) and 4 (3,5-CP) have been determined. The σ m values for these structurally different CP-PAHs are nearly identical. This gives evidence that the cyclopenta moiety acts as a peri -substituent with σ m =0.4±0.07.