Vinko Nemec, Nikola Bedeković and Dominik Cinčić, researchers of the Department of Chemistry, and Ruđer Sušanj, a student of the Department of Chemistry, have published an article titled Halogen Bond Motifs in Cocrystals of N,N,O and N,O,O Acceptors Derived from Diketones and Containing a Morpholine or Piperazine Moiety in the ACS journal Crystal Growth & Design (IF 4.010).
The work was focused on studying the propensity of the morpholine and piperazine functional groups for halogen bonding when they are peripherally located on larger molecules. To that end, four imines were prepared by a reaction between N-(2-aminoethyl)morpholine or N-(2-aminoethyl)piperazine and either acetylacetone or 1-benzoylacetone. The prepared imines were then cocrystallized with two perfluorinated halogen bond donors, 1,4-diiodotetrafluorobenzene and 1,3,5-triiodo-2,4,6-trifluorobenzene. Eight new cocrystals were prepared by crystallization from reactant solutions. The products were then characterized by single crystal X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry. Structural analysis has confirmed the acceptor potential of both the morpholine oxygen and terminal piperazine nitrogen atoms, because they were found out to participate in N/O∙∙∙I halogen bonding in all of these cocrystals. Analysis of relative shortening values and other parameters of the observed halogen bonds has shown that the terminal piperazine nitrogen atom participates in shorter, more linear halogen bonds than the morpholine oxygen atom.
This research was performed as part of the project New building blocks for the supramolecular design of complex multi-component molecular crystals based on halogen bonds (HaloBond IP-2019-04-1868), financed by the Croatian Science Foundation