Naslov
Halogen bond as a rival to hydrogen bond in crystal engineering – cocrystals of N- halogenoimides

Autori
Stilinović, Vladimir ; Cinčić, Dominik

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

Izvornik
25th Congress of Society of Chemists and Technologists of Macedonia - Book of Abstracts / - , 2018, 162-162

Skup
25th Congress of Society of Chemists and Technologists of Macedonia

Mjesto i datum
Ohrid, Sjeverna Makedonija, 19.09.2018. - 22.09.2018

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
halogen bond ; imide ; crystal engineering ; cocrystal

Sažetak
Over the past couple of decades, the importance of halogen bonds (XB) 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. Recently, N-halogenated imides, common halogenating agents in organic synthesis, have been marked as extremely strong halogen donors. In our studies, we have conducted an extensive study on the effect of the halogen type as well as the basicity (nucleophilicity) of the halogen acceptor in N-halogenated succinimide cocrystals with pyridine derivatives of different basicities. These studies have shown N-halogenated succinimides to form short XBs with the presented donors with the bond energies decreasing with the decrease of the pyridine basicity and with decreasing size of the halogen (I>Br>Cl). The use of imides allowed for a direct comparison between halogen bonding (with N-halosuccinimides) and hydrogen bonding with unmodified succinimide, which has revealed that the hydrogen bond is in fact weaker than the halogen bond with iodine, and comparable to that with bromine. Employing different imides can change the potential of forming other interactions – when N-halogenated phthalimides are used as XB donors, weak hydrogen bonds form which might complement, or compete with, the primary halogen bond formed by the imide and a XB acceptor. Particularly interesting are cocrystals formed by N-halogenimides and pyridines possessing additional halogen (or hydrogen) bond donor groups. The halogen atom of the N-haloimide binds preferentially to the pyridine nitrogen, while the halogen of the pyridine ring forms only substantially longer halogen bond with the N- haloimide oxygen atoms, other halogen atoms, or π- systems. This hierarchy is maintained even if the N-haloimide halogen is a lighter one than the one on the pyridine ring following the molecular electrostatic potential ; the highest positive values of ESP being associated with the best XB- donor atoms. In cocrystals of N-iodoimides with aminopyridines, the imide and pyridine nitrogen also bind 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. The dominant interaction in all structures is clearly the halogen bond with the N-haloimide as the donor. In this way we were able to study the subtle interplay of halogen and hydrogen bond.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA