Simple design for metal-based halogen-bonded cocrystals utilizing the M–Cl⋯I motif

Abstract

We demonstrate a strategy for synthesizing halogen-bonded metal–organic cocrystals by utilizing metal complexes whose pendant chloride group enables halogen bonding. A series of 12 cocrystals involving octahedral CoCl₂L₂ complexes (L = 2,2′-bipyridine or 1,10 phenantroline) as halogen bond acceptors were prepared by both liquid-assisted grinding and conventional solution-based methods. The efficacy of this strategy is evident by the assembly of a large family of cocrystals involving six perfluorinated halogen bond donors: 1,4-diiodotetrafluorobenzene, 1,3-diiodotetrafluorobenzene, 1,2-diiodotetrafluorobenzene, 1,3,5-triiodotrifluorobenzene, iodopentafluorobenzene and octafluoro-1,4-diiodobutane. Single crystal X-ray diffraction experiments have shown that cocrystals display different crystal packing governed by Cl⋯I halogen bonds between halogen bond donor iodine atoms and metal complex chlorine atoms (varying from 3.061 to 3.471 Å) based on zero-, one-, two- and three- dimensional halogen-bonded architectures.