engleski

Halogen bond motifs in cocrystals of Schiff bases that contain a morpholine or piperazine moiety

In the past few decades halogen bonding has become a focus of research of many organic, supramolecular and solid-state chemists. It has been shown that it can be a powerful tool in crystal engineering for the design of organic, metal-organic and ionic materials. In the course of this research we have investigated the halogen bond acceptor potential of oxygen and nitrogen atoms of morpholine and piperazine fragments when located peripherally on tritopic N, O, O or N, N, O acceptor molecules. For this purpose, four Schiff bases with peripherally located piperazine and morpholine moieties, derived from acetylacetone and 1-benzoylacetone, have been cocrystallized with 1, 4-diiodo- and 1, 3, 5- triiodotrifluorobenzene. This has resulted in eight halogen-bonded cocrystals featuring different topicities and geometric dispositions of donor atoms. The obtained cocrystals have been structurally characterised by X-ray diffraction (SCXRD, PXRD) and thermal (TG-DSC) methods. From the crystallographic data it was possible to infer that the morpholine oxygen and terminal piperazine nitrogen atoms participate in all cases as acceptors in halogen bonding, thus confirming our hypothesis and previous research indicating that these fragments could be used in crystal engineering of various halogen-bonded solids. Contrary to our expectations, the I···O(morpholine) halogen bonds feature lower relative shortening values than I···N(terminal), I···O(carbonyl) and I···N(proximal) halogen bonds. The N and O halogen bond acceptor sites were additionally evaluated through calculations of molecular electrostatic potential (MEP) values.

Halogen-bonding, Carbonyls, Group 17 compounds, Molecules, Nitrogen, Oxygen

nije evidentirano