Naslov
Incommensurately modulated structure of the halogen bonded cocrystal of urotropine and octafluoro-1, 4-diiodobutane

Autori
Tolj, Davor ; Stilinović, Vladimir ; Topić, Edi ; Nemec, Vinko ; Cinčić, Dominik

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

Izvornik
The Twenty-fourth Croatian-Slovenian Crystallographic Meeting - Book of Abstracts / Bijelić, Mirjana ; Cetina, Mario ; Čobić, Andrea ; Matković-Čalogović, Dubravka ; Popović, Stanko ; Štefanić, Zoran ; Tonejc, Antun ; Višnjevac Aleksandar - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU) ; Hrvatska kristalografska zajednica HAZU, 2016, 46-46

Skup
The Twenty-fourth Croatian-Slovenian Crystallographic Meeting

Mjesto i datum
Bol, Hrvatska, 22.09.2016. - 24.09.2016

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
cocrystals ; incommensurate crystal ; octafluoro-1, 4-diiodobutane

Sažetak
Aperiodic crystals are crystals which do not possess 3D translation symmetry. An incommensurately modulated structure can be considered a perturbed periodic crystal. Urotropine (hexamethylenetetramine) is a quasi-spherical molecule that is known for forming co-crystals of modulated superstructures with long linear coformers such as aliphatic diacids, of wich cocrystal with azelaic acid was found to have an invommensurately modulated superstructure. Here we present a halogen bonded cocrystal of urotropine and a linear halogen bond donor, octafluoro-1, 4-diiodobutane (ofib). The cocrystal was prepared by means of LAG (liquid-assisted grinding) and from solution. X-ray diffraction at room temperature has shown that the structure of the cocrystal is incommensurately modulated with a monoclinic sublattice (a = 5.976 Å, b = 24.82 Å, c = 6.015 Å, β = 105.82°, Z = 2) and the modulation vector q(298 K) = (0.0808, 0, 0.2063). Repeated measurement at 150K has shown only minor changes in the sublattice parameters (a = 5.911 Å, b = 24.21 Å, c = 5.947 Å, β = 103.94°, Z = 2) and a considerable change in the modulation vector q(150 K) = (0.0824, 0, 0.1907). Interestingly, it was possible to solve and refine both the room temperature and low temperature structures as periodic approximates – the room temperature one can be modeled as a centrosymmetric monoclinic structure with Z = 20, and the low temperature as an acentric monoclinic one with Z = 22 (Figure 1). Subsequent measurements oft he unit cell parameters and the modulation vector have shown that the change occurs relatively abruptly between 0 °C and the room temperature. There was, however, no corresponding thermal event discernable in the DSC curve bellow the room temperature, but a reversible phase transition at 35-40 °C has been detected, which has prompted us to remeasure the crystal at 325 K. The crystal structure of the high temperature phase was found to be a non-modulated orthorhombic structure with severe disorder in difluoromethylene groups of the ofib molecules.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA