Stacking of planar conjugated rings: a continuum of interactions ranging from dispersion to multicentric two-electron covalent bonding (CROSBI ID 664654)
Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija
Podaci o odgovornosti
Molčanov, Krešimir ; Kojić-Prodić, Biserka
engleski
Stacking of planar conjugated rings: a continuum of interactions ranging from dispersion to multicentric two-electron covalent bonding
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').
pi-stacking ; aromaticity ; quinones ; semiquinone radicals ; metal chelates
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Podaci o prilogu
16-16.
2018.
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objavljeno
Podaci o matičnoj publikaciji
The 5th Crystal Engineering and Emerging Materials Workshop of Ontario & Quebec (CEMWOQ5) : Book of Abstracts
Friščić, Tomislav
Montréal: McGill University
Podaci o skupu
The 5th Crystal Engineering and Emerging Materials Workshop of Ontario & Quebec (CEMWOQ5)
pozvano predavanje
16.07.2018-19.07.2018
Montréal, Kanada