Naslov
Synthon conservation upon changing the contact atom in saccharin and N-halogenosaccharin cocrystals

Autori
Stilinović, Vladimir ; Cinčić, Dominik

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

Izvornik
25th Slovenian – Croatian Crystallographic Meeting - Book of abstracts / - , 2017, 43-43

Skup
25th Slovenian – Croatian Crystallographic Meeting

Mjesto i datum
Ljubljana, Slovenija, 15.06.2017. - 17.06.2017

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
halogen bond ; synthon ; 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 strengths and directionalities which rival (and even surpass) those of hydrogen bonds in equivalent surroundings. The similarity of hydrogen and halogen bonds also raises question of their interchangeability in supramolecular architectures, i.e. whether equivalent structural motifs will be achieved either through halogen or hydrogen bond, providing the donor and acceptor to be other ways identical. In the case of weak halogen/hydrogen bonds of C−X∙∙∙Y type (X = H, I ; Y = N, O) this does seem to hold, however with strong halogen/hydrogen bonds (N−X∙∙∙Y type ; X = H, I, Br ; Y = N, O) additional question of hydrogen/halogen transfer along the bond may arise, thus significantly complicating the possible outcomes of co-crystallisation experiments. In order to investigate this, we have prepared a number of cocrystals derived from saccharin (NHSacc) and its N- iodinated and -brominated derivatives (NISacc and NBrSacc) and a series of pyridine derivatives. Being a relatively strong organic acid with pKa = 1.6, saccharin is an excellent model compound for the study of proton transfer in the solid state, as it should be able to protonate majority of usual simple pyridine derivatives (pKa range ca. 1-10). At the same time N- iodosaccharin, has been shown to be excellent halogen bond donors. The results of our study show that the dominant supramolecular bond in all cocrystals derived from NISacc and NBrSacc is the N−X∙∙∙N halogen bond between the saccharin donor and the pyridine acceptor. In the case of NHSacc, the N−H∙∙∙N hydrogen bond occurs only in cocrystals where proton transfer has not occurred, while in salts N+−H∙∙∙O− hydrogen bond between the pyridinium N−H and the carbonyl group of the saccharinate anion. The proton transfer between saccharin and the pyridine is only partially controlled by the basicity of the pyridine - it does occur with all strong bases, while among weaker bases either N−H∙∙∙N or N+−H∙∙∙O− hydrogen bonded molecules may be found, depending on other supramolecular interactions.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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