Isostructural Materials Achieved by Using Structurally Equivalent Donors and Acceptors in Halogen‐Bonded Cocrystals

Abstract

We demonstrate the supramolecular and structural equivalence of two halogen-bond donors (I and Br) and three acceptors (O, NH and S) through the synthesis of seven isostructural halogen-bonded cocrystals, involving six different molecules: 1,4-dibromo- and 1,4-diiodotetrafluorobenzene (donors) and thiomorpholine, thioxane, morpholine, and piperazine (acceptors). The formation of isostructural cocrystals indicates how cocrystallization may be used to overcome shape and functional group dissimilarities that control molecular arrangement in the solid state. The differences in composition between the seven isostructural cocrystals directly affect the strength and nature of halogen bonds between their constituents, allowing the systematic variation of cocrystal physical properties, in particular the melting point, without affecting their crystal structure. Replacement of each O or S halogen-bond acceptor with an NH group provided an approximate 70 degrees C increase in melting point, whereas the replacement of I with Br as the halogen-bond donor lowered the melting point of the resulting solid by a similar amount.

Equivalence of Ethylene and Azo-Bridges in the Modular Design of Molecular Complexes: Role of Weak Interactions

“…In their work on isostructurality, Jones and coworkers proposed the structural equivalence of halogen bonded -Br and -I in molecular complexes. 56,57 In a recent report, some of us 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 11 observed that due to the bigger size and higher polarizability of the electron cloud, I is capable of making I···I, I···C (sp2) , and I···N interactions, while smaller Cl prefers C−H···Cl hydrogen bonds. The intermediate Br, however, shifts its grouping depending on the crystallization conditions and coformers.…”

Halogen bonding in water results in enhanced anion recognition in acyclic and rotaxane hosts

“…1a). Although the utilization of halogen bonding (XB) in solid-state crystal engineering has been extensively explored [3][4][5][6][7] , its application in solution-phase molecular recognition and self-assembly remains underdeveloped, despite the obvious analogy with the ubiquitous hydrogen bond 8 . It is only very recently that seminal applications of XB to the fields of molecular recognition and assembly 9,10 , anion binding [11][12][13][14][15][16] and membrane transport 17 , catalysis 18 , structural biology 19 and medicinal chemistry 20 have resulted in an explosion of interest in this non-covalent intermolecular interaction.…”

Halogen Bonding in Crystal Engineering

“…[8,11,[20][21][22][23][24] Metal halides, oxygen, sulfur, selenium and even silicon have, however, been reported to have the capacity to act as halogen bond acceptors with suitable donors. [25][26][27][28][29][30][31] …”

“…[28,32,33] Similarly, 1,3-diiodoterfluorobenzene has been widely used as the Lewis acid in halogen bonds. [22,34,35] In the present study, however, we focus first on the XB systems with the less commonly used isomer of diiodotetrafluorobenzene, i.e., 1,2-diiodoterfluorobenzene (1,2-TFIB).…”