Naslov
Coexistence of halogen and hydrogen bonds in crystal structures – competition, cooperation and antagonism

Autori
Stilinović, Vladimir ; Cinčić, Dominik

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

Izvornik
The Twenty-Sixth Croatian-Slovenian Crystallographic Meeting - Book of abstracts and Programme / Matković-Čalogović, Dubravka ; Popović, Stanko ; Skoko, Željko - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU) ; Hrvatska Kristalografska Zajednica, 2018, 10-10

Skup
26th Croatian-Slovenian Crystallographic Meeting (CSCM26)

Mjesto i datum
Poreč, Hrvatska, 13.06.2018. - 17.06.2018

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
halogen bond, hydrogen bond, N-halogenoimides, aminopyridines, halogenopyridines

Sažetak
Over the past couple of decades, the importance of halogen bonds in crystal engineering is constantly increasing. This is predominantly due to their strength and directionality which are commonly claimed to be close to those of hydrogen bonds – the generally accepted benchmark for evaluation of intermolecular interactions in supramolecular chemistry and crystal engineering. In this contribution, the comparison of halogen and hydrogen bonding will be made by studying structures in which halogen and hydrogen bonds coexist. In this manner some of similarities and differences between the two interactions will be discussed. In the first part of the talk we shall concentrate on the competition between halogen bond and ‘classical’ strong hydrogen bonds (N– H∙∙∙O and N–H∙∙∙N). As a model system for this study we have employed cocrystals of N- halogenoimides with aminopyridines. NHalogenoimides (N- iodoimides in particularly) have been shown to be extremely strong halogen donors, with halogen bond energies larger than those of equivalent hydrogen bonds. [1] In cocrystals of N-iodoimides with aminopyridines, the imide and pyridine nitrogen always binds through a very short N–I∙∙∙N halogen bond, while the amino group participates in N– H∙∙∙O – hydrogen bonds with imine oxygen atoms, in much the same way as aromatic groups form C–H∙∙∙O interactions in equivalent structures without strong hydrogen donors.[2] The dominant interaction in all structures is clearly the halogen bond. In the second part we shall observe the interdependence of halogen and hydrogen bonds in salts and cocrystals of organic acids of various strengths with metahalogenopyridines, a series of rather modest halogen bond donors. The dominant interaction in these structures is O– H∙∙∙N (or O–∙∙∙H–N+) hydrogen bond between the acid and the pyridine. This bond however can be affected by the additional halogen bond. The effect can be measured within series of isostructural compounds derived from halogenopyridines, as the steric properties and pKa values change very little with the change of the halogen, the only significant variable being the ability of the halogenopyridine to form halogen bond (which increases with the size of the halogen). In this way we were able to study the subtle interplay of halogen and hydrogen bond, revealing instances of both cooperativie and antagonistic interdependence between the two interactions.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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