Naslov
Charge density of the semiquinone radical anion

Autori
Molčanov, Krešimir ; Jelsch, Christian ; Wenger, Emmanuel ; Stilinović, Vladimir ; Kojić-Prodić, Biserka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
30th European Crystallographic Meeting, Book of Abstracts / Fromm, Katharina - Basel : European Crystallographic Association, 2016, S90-s90

Skup
30th European Crystallographic Meeting

Mjesto i datum
Basel, Švicarska, 28.08.2016. - 01.09.2016

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
semiquinone ; electronic structure ; charge density

Sažetak
Semiquinones are a class of stable organic radical anions ; especially stable are ones with four electronegative substituents such as halogens, which enhance delocalisation of the unpaired electron. Therefore, they are potential candidates for design of functional materials with fine-tuned magnetic properties. Here we present detalied study of electron density and delocalisation in two polymorphs of N-methylpyridinium salt of the tetrachlorosemiquinone radical anion (N- MePy∙CA), which are especially interesting due to their stability and semiconductivity. In the diamagnetic polymorph closely bound radical dimers occur, similar to previously known K∙CA∙Me2CO and similar alkali salts of 5, 6- dichloro-2, 3-dicyanosemiquinone (DDQ), and the crystals are diamagnetic due to spin pairing. In the orthorhombic polymorph radicals are equdistant, leading to 1D antiferromagnetic coupling between the spins. Electronic delocalisation in the semiquinones is particulary interesting because it is somewhere between aromatic (fully delocalised π electrons) and quinoid (distinguishable single and double bonds), as confirmed by previous crystallographic and computational studies. However, exact bond orders of C-C and C-O bonds have not yet been experimentally determined. Also, study of charge density reveals subtle differences between diamagnetic (triclinic) and antiferromagnetic (orthorhombic) phases, which will enable more insight into the phenomenon of magnetic exchange between organic molecules. This is the first experimental study of electronic structure in ionic semiquinones, and is complemented by periodic DFT caculations.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA