Naslov
Dipole-dipole interactions in crystal structures of 1, 3, 3'-triketones

Autori
Stilinović, Vladimir

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

Izvornik
Engineering of crystalline materials properties: state-of-the-art in modelling, design, applications / Addadi , Lia ; Braga , Dario ; Novoa , Juan - Erice : International School of Crystallography, 2007, 644-644

Skup
Engineering of crystalline materials properties: state-of-the-art in modelling, design, applications

Mjesto i datum
Erice, Italija, 07.06.2007. - 17.06.2007

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
crystal packing; dipole interactions; triketones

Sažetak
The carbonyl groups are quite ubiquitous in organic and biological chemical systems and their supramolecular chemistry has been widely studied. Since carbonyl group interactions are much used in the field oh crystal engineering, and carbonyl groups can be engaged in several different types of interactions, the study of these interactions can prove of great value. The most studied to date has been the role of the carbonyl group in hydrogen bonding, but it was also shown that carbonyl-carbonyl interactions (not mediated by hydrogen) exist and can even be competitive with hydrogen bonding.[1] The carbonyl group is characterised by a rather large dipole moment. Molecules with several (properly oriented) carbonyl groups are therefore quite polar, and it is to be expected that their polarity will have an important role in their crystal packing. 1, 3, 3'-triketones (triacylmethanes) are compounds with three carbonyl groups bound to the same tertiary carbon. Although such compounds could exist in several enolic tautomer forms, acyclical 1, 3, 3'-triketones crystallize solely as triketo tautomers. In this form, all carbonyl groups are oriented on the same side of the molecule, rendering the molecule very polar. In our study about a dozen 1, 3, 3'-triketones were synthesized and their crystal structures solved. In all these structures the predominant driving force in crystal packing are dipole-dipole interactions. The molecules pack in rows so that their dipole moments are collinear (or quasi-collinear) and aligned in a head to tail manner. Molecules can be of the same orientation (parallel) in all rows, thus creating a structure with a polar axes, or the molecules of neighbouring rows can be of opposite orientation (antiparallel) which is the case in centric structures. Varying the acyl groups of the triketones, the crystal structures are greatly altered. However, the dipole interaction is always the predominant crystal packing driving force. In structures where other intermolecular interactions also exist, they are usually collinear with the polar interactions acting in synergy with them. In fewer cases the carbonyl groups act as proton acceptors in C-H… O hydrogen bonding with molecules of the neighbouring row. Although such interactions are antagonistic to the stacking of dipoles since they somewhat reduce the dipole moment of the triketone molecule, the dipole interactions remain principal driving force in the crystal structure. [1] F. H. Allen, C. A. Baalham, J. P. M. Lommerse, P. R. Raithby, Acta Cryst. (1998) B54, 320-329.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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