Naslov
Stacking of planar conjugated rings: a continuum of interactions ranging from dispersion to multicentric two-electron covalent bonding

Autori
Molčanov, Krešimir ; Kojić-Prodić, Biserka

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

Izvornik
The 5th Crystal Engineering and Emerging Materials Workshop of Ontario & Quebec (CEMWOQ5) : Book of Abstracts / Friščić, Tomislav - Montréal : McGill University, 2018, 16-16

Skup
The 5th Crystal Engineering and Emerging Materials Workshop of Ontario & Quebec (CEMWOQ5)

Mjesto i datum
Montréal, Kanada, 16.07.2018. - 19.07.2018

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
pi-stacking ; aromaticity ; quinones ; semiquinone radicals ; metal chelates

Sažetak
Stacking of aromatic rings is a well-known type of intermolecular interaction. It is usually considered as rather weak (typically <1 kcal mol-1), and is assumed that it is an exclusive property of aromatic rings ; the fact that other types of planar conjugated rings also stack is usually overlooked. Misconceptions about the very nature of stacking are numerous, and are reflected in a variety of names used (often misleading): π∙∙∙π interaction, π-stacking, π-interaction, aromatic interaction, stacking interaction, etc. However, there is a growing amount of evidence that all rings stack, and that aromaticity is not a conditio sine qua non for formation of π-stacks. Stacking of planar organic radicals has been used in design of organic semiconductors and magnetic materials. Our detailed studies have shown that interactions between quinoid rings and semiquinone radicals are by an order of a magnitude stronger than interactions between aromatics. As a result of numerous X-ray charge density studies on different types of stacked rings, we propose a generalised model of stacking, which accounts for both aromatic and non-aromatic rings. Our results show that: 1) non-aromatic planar polyenic rings can stack ; 2) interactions are more pronounced between systems/rings with little or no π-electron delocalisation (e.g. quinones) than those involving delocalised systems (e.g. aromatics) ; 3) the main component of the interaction is electrostatic/multipolar between closed-shell rings ; 4) interactions between radicals involve a significant covalent contribution. Thus, stacking covers a wide range of interactions and energies ranging from weak dispersion to non-localised two-electron multicentric covalent bonding ('pancake bonding').

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA