The Morpholinyl Oxygen Atom as an Acceptor Site for Halogen-Bonded Cocrystallization of Organic and Metal–Organic Units

We explore the halogen bond acceptor potential of the morpholinyl oxygen atom in the synthesis of cocrystals involving organic and metal–organic units, by using N -aminomorpholine either as a potential halogen bond acceptor or as a reagent to insert a morpholine moiety into larger organic and copper(II)-based metal–organic building blocks. Challenged against four well-known halogen bond donor molecules differing in binding geometry and composition, these three morpholine-containing units have yielded a total of seven previously not reported cocrystals, of which six (86%) exhibited the formation of I···O or Br···O halogen bonds to the morpholinyl oxygen atom. The results illustrate the possibility to systematically insert and use a morpholine group as an efficient halogen bond acceptor into organic and metal–organic structures, thus enabling cocrystal formation.