Naslov
Spin pairing, electrostatic and dipolar interactions shape stacking of radical anions in alkali salts of 4, 5-dichloro-3, 6-dioxocyclohexa-1, 4-diene-1, 2-dicarbonitrile (DDQ)

Autori
Molčanov, Krešimir ; Kojić-Prodić, Biserka

Izvornik
Crystengcomm (1466-8033) 19 (2017), 13; 1801-1808

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
semiquinone, pi-interactions, stacking, crystal engineering

Sažetak
A series of five novel air-stable alkali salts of 4, 5-dichloro-3, 6-dioxocyclohexa-1, 4-diene-1, 2-dicarbonitrile radical anion (DDQ) were prepared and structurally characterised. Four of them (Li, Na and two Cs salts) involve Peierls-distorted π-stacks of radicals, while the K salt-structure comprises equidistant stacks of radicals. Different orientations of radicals in the stacks and different directions of offset have been observed. For an unambiguous description of π-stacking geometry of quinones and semiquinone radicals, the geometric parameters calculated by the program PLATON are not sufficient. Therefore, the two additional geometric parameters are introduced: δ (torsion angle between molecular axes O=C∙∙∙C=O of contiguous rings) and ε (angle between the molecular axis O=C∙∙∙C=O and direction of the offset). On a base of these geometric parameters the optimal stacking orientations can be quantified and correlated with the polarity and steric effects.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA