skip to main content


Title: Controlling Thermal Expansion in Supramolecular Halogen‐Bonded Mixed Cocrystals through Synthetic Feed and Dynamic Motion
Abstract

Control over thermal expansion (TE) behaviors in solid materials is often accomplished by modifying the molecules or intermolecular interactions within the solid. Here, we use a mixed cocrystal approach and incorporate molecules with similar chemical structures, but distinct functionalities. Development of mixed cocrystals is at a nascent stage, and here we describe the first mixed cocrystals sustained by one‐dimensional halogen bonds. Within each mixed cocrystal, the halogen‐bond donor is fixed, while the halogen‐bond acceptor site contains two molecules in a variable ratio. X‐ray diffraction demonstrates isostructurality across the series, and SEM‐EDS shows equal distribution of heavy atoms and similar atomic compositions across all mixed cocrystals. The acceptor molecules differ in their ability to undergo dynamic motion in the solid state. The synthetic equivalents of motion capable and incapable molecules were systematically varied to yield direct tunabililty in TE behavior.

 
more » « less
Award ID(s):
2045506
NSF-PAR ID:
10368424
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie International Edition
Volume:
61
Issue:
26
ISSN:
1433-7851
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Control over thermal expansion (TE) behaviors in solid materials is often accomplished by modifying the molecules or intermolecular interactions within the solid. Here, we use a mixed cocrystal approach and incorporate molecules with similar chemical structures, but distinct functionalities. Development of mixed cocrystals is at a nascent stage, and here we describe the first mixed cocrystals sustained by one‐dimensional halogen bonds. Within each mixed cocrystal, the halogen‐bond donor is fixed, while the halogen‐bond acceptor site contains two molecules in a variable ratio. X‐ray diffraction demonstrates isostructurality across the series, and SEM‐EDS shows equal distribution of heavy atoms and similar atomic compositions across all mixed cocrystals. The acceptor molecules differ in their ability to undergo dynamic motion in the solid state. The synthetic equivalents of motion capable and incapable molecules were systematically varied to yield direct tunabililty in TE behavior.

     
    more » « less
  2. null (Ed.)
    The halogen-bond (X-bond) donors 1,3- and 1,4-diiodotetrafluorobenzene (1,3-di-I-tFb and 1,4-di-I-tFb, respectively) form cocrystals with trans-1,2-bis(2-pyridyl)ethylene (2,2′-bpe) assembled by N···I X-bonds. In each cocrystal, 2(1,3-di-I-tFb)·2(2,2′-bpe) and (1,4-di-I-tFb)·(2,2′-bpe), the donor molecules support the C=C bonds of 2,2′-bpe to undergo an intermolecular [2+2] photodimerization. UV irradiation of each cocrystal resulted in stereospecific and quantitative conversion of 2,2′-bpe to rctt-tetrakis(2-pyridyl)cyclobutane (2,2′-tpcb). In each case, the reactivity occurs via face-to-face π-stacked columns wherein nearest-neighbor pairs of 2,2′-bpe molecules lie sandwiched between X-bond donor molecules. Nearest-neighbor C=C bonds are stacked criss-crossed in both cocrystals. The reactivity was ascribed to the olefins undergoing pedal-like motion in the solid state. The stereochemistry of 2,2′-tpcb is confirmed in cocrystals 2(1,3-di-I-tFb)·(2,2′-tpcb) and (1,4-di-I-tFb)·(2,2′-tpcb). 
    more » « less
  3. The ditopic halogen-bond (X-bond) donors 1,2-, 1,3-, and 1,4-diiodotetrafluorobenzene (1,2-, 1,3-, and 1,4-di-I-tFb, respectively) form binary cocrystals with the unsymmetrical ditopic X-bond acceptor trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (2,4-bpe). The components of each cocrystal (1,2-di-I-tFb)·(2,4-bpe), (1,3-di-I-tFb)·(2,4-bpe), and (1,4-di-I-tFb)·(2,4-bpe) assemble via N···I X-bonds. For (1,2-di-I-tFb)·(2,4-bpe) and (1,3-di-I-tFb)·(2,4-bpe), the X-bond donor supports the C=C bonds of 2,4-bpe to undergo a topochemical [2+2] photodimerization in the solid state: UV-irradiation of each solid resulted in stereospecific, regiospecific, and quantitative photodimerization of 2,4-bpe to the corresponding head-to-tail (ht) or head-to-head (hh) cyclobutane photoproduct, respectively.

     
    more » « less
  4. Utilizing the N -heterocyclic chalcogenones hexahydro-1,3-bis(2,4,6-trimethylphenyl)-2 H -1,3-diazepine-2-thione ( SDiazMesS ) and hexahydro-1,3-bis(2,4,6-trimethylphenyl)-2 H -1,3-diazepine-2-selone ( SDiazMesSe ) as halogen-bond acceptors, a total of 24 new cocrystals were prepared. The solid-state structures of the parent molecules were also determined, along with those of their acetonitrile solvates. Through the reaction of the chalcogen atom with molecular diiodine, a variety of S—I—I and Se—I—I fragments were formed, spanning a wide range of I—I bond orders. With acetone as a reaction solvent, molecular diiodine causes the oxidative addition of acetone to the chalcogen atom, resulting in new C—S, C—Se and C—C covalent bonds under mild conditions. The common halogen-bond donors, iodopentafluorobenzene, 1,2-, 1,3- and 1,4-diiodotetrafluorobenzene, 1,3,5-trifluorotriiodobenzene and tetraiodoethylene resulted in halogen-bond-driven cocrystal formation. In most cases, the analogous SDiazMesS and SDiazMesSe cocrystals are isomorphic. 
    more » « less
  5. The thermal expansion behavior of a series of halogen-bonded cocrystals containing 1,4-diiodoperchlorobenzene as the donor is described. Two of the solids are polymorphs and contain 4-stilbazole as the acceptor, while the third solid contains 4-(phenylethynyl)pyridine as the acceptor, and this solid is isostructural with one of the polymorphs. All solids are sustained by I···N halogen bonds, and the least thermal expansion occurs along this direction in all solids. The polymorphs exhibit significant differences in π stacking, and we show that electronically similar face-to-face stacked rings undergo more expansion compared to electronically different stacked rings. Moreover, in the two polymorphs, the directions of moderate expansion and most expansion are reversed, demonstrating how cocrystal polymorphism can affect material properties. 
    more » « less