Special Issue "Halogen-Bonded Cocrystals"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: 30 September 2019.

Special Issue Editor

Guest Editor
Dr. Filip Topic

McGill University, Department of Chemistry, Montreal, Canada
Website | E-Mail
Interests: halogen bonding; X-ray crystallography; cocrystals; mechanochemistry; crystal engineering; supramolecular chemistry

Special Issue Information

Dear Colleagues,

Cocrystals encompass, in the broadest sense, solids consisting of two or more different molecular species. They have been intensively studied in the past two decades, not least for the great promise in the development of novel pharmaceutical materials, but also as a means of engineering novel crystalline materials with improved optical, mechanical and other properties.

Halogen bonding, an attractive interaction between an electrophilic region on a halogen atom and a nucleophilic moiety, has similarly experienced a renaissance in the last two decades. Cocrystals have enabled the exploration of the unique behaviour of halogen bonding, at times paralleling yet sometimes contrasting with hydrogen bonding, the competition of halogen bonding with other weak interactions, and the (non-)isomorphous switching of donor halogens between iodine, bromine and chlorine. Similarly, halogen-bonded cocrystals have played a critical role in demonstrating exciting new applications of halogen bonding, such as novel strategies for the preparation of liquid crystals, supramolecular gels and luminescent materials as well as the templating of solid-state reactions. X-ray crystallography has been an essential tool for the structural elucidation of halogen-bonded solids, more and more often supported by solid-state NMR and computational studies.

With this Special Issue on the topic of “Halogen-Bonded Cocrystals” we want to provide a venue for contributions dealing with the structures and properties of halogen-bonded organic solids, with a special focus on cocrystals, while also including closely related systems such as amorphous solids, liquid crystals or gels in which the halogen bonding plays a significant role.

Dr. Filip Topic
Guest Editor

Manuscript Submission Information

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Keywords

  • halogen bonding
  • cocrystals
  • molecular solids
  • polymorphs

Published Papers (4 papers)

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Research

Open AccessArticle
Extended Assemblies of Ru(bpy)(CO)2X2 (X = Cl, Br, I) Molecules Linked by 1,4-Diiodotetrafluoro-Benzene (DITFB) Halogen Bond Donors
Crystals 2019, 9(6), 319; https://doi.org/10.3390/cryst9060319
Received: 20 May 2019 / Revised: 12 June 2019 / Accepted: 19 June 2019 / Published: 24 June 2019
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Abstract
The ruthenium carbonyl compounds, Ru(bpy)(CO)2X2 (X = Cl, Br or I) act as neutral halogen bond (XB) acceptors when co-crystallized with 1,4-diiodotetrafluoro-benzene (DITFB). The halogen bonding strength of the Ru-X⋅⋅⋅I halogen bonds follow the nucleophilic character of the halido ligand. [...] Read more.
The ruthenium carbonyl compounds, Ru(bpy)(CO)2X2 (X = Cl, Br or I) act as neutral halogen bond (XB) acceptors when co-crystallized with 1,4-diiodotetrafluoro-benzene (DITFB). The halogen bonding strength of the Ru-X⋅⋅⋅I halogen bonds follow the nucleophilic character of the halido ligand. The strongest halogen bond occurs between the chlorido ligand and the iodide atoms of the DITFB. All three halogen bonded complexes form polymeric assemblies in the solid state. In Ru(bpy)(CO)2Cl2⋅DITFB (1) and in Ru(bpy)(CO)2Br2⋅DITFB (2) both halido ligands are halogen bonded to only one DITFB donor. In Ru(bpy)(CO)2I2⋅DITFB (3) only one of the halido ligands is involved in halogen bonding acting as ditopic center for two DITFB donors. The polymeric structures of 1 and 2 are isomorphic wave-like single chain systems, while the iodine complexes form pairs of linear chains attached together with weak F⋅⋅⋅O≡C interactions between the closest neighbors. The stronger polarization of the iodide ligand compared to the Cl or Br ligands favors nearly linear C-I⋅⋅⋅I angles between the XB donor and the metal complex supporting the linear arrangement of the halogen bonded chain. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
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Open AccessArticle
Adenine as a Halogen Bond Acceptor: A Combined Experimental and DFT Study
Crystals 2019, 9(4), 224; https://doi.org/10.3390/cryst9040224
Received: 25 March 2019 / Revised: 12 April 2019 / Accepted: 24 April 2019 / Published: 25 April 2019
Cited by 3 | PDF Full-text (3114 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we report the cocrystallization of N9-ethyladenine with 1,2,4,5-tetrafluoro-3,6-diiodobenzene (TFDIB), a classical XB donor. As far as our knowledge extends, this is the first cocrystal reported to date where an adenine derivative acts as a halogen bond acceptor. In [...] Read more.
In this work, we report the cocrystallization of N9-ethyladenine with 1,2,4,5-tetrafluoro-3,6-diiodobenzene (TFDIB), a classical XB donor. As far as our knowledge extends, this is the first cocrystal reported to date where an adenine derivative acts as a halogen bond acceptor. In the solid state, each adenine ring forms two centrosymmetric H-bonded dimers: one using N1···HA6–N6 and the other N7···HB6–N6. Therefore, only N3 is available as a halogen bond acceptor that, indeed, establishes an N···I halogen bonding interaction with TFDIB. The H-bonded dimers and halogen bonds have been investigated via DFT (Density Functional Theory) calculations and the Bader’s Quantum Theory of Atoms In Molecules (QTAIM) method at the B3LYP/6-311+G* level of theory. The influence of H-bonding interactions on the lone pair donor ability of N3 has also been analyzed using the molecular electrostatic potential (MEP) surface calculations. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
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Open AccessArticle
Synthesis, Structures and Co-Crystallizations of Perfluorophenyl Substituted β-Diketone and Triketone Compounds
Crystals 2019, 9(3), 175; https://doi.org/10.3390/cryst9030175
Received: 26 February 2019 / Revised: 15 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
Cited by 1 | PDF Full-text (3394 KB) | HTML Full-text | XML Full-text
Abstract
Perfluorophenyl-substituted compounds, 3-hydroxy-1,3-bis(pentafluorophenyl)-2- propen-1-one (H1) and 1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one (H22), were prepared in 56 and 30% yields, respectively, and only the enol forms were preferentially obtained among the keto-enol tautomerism. Molecular conformations and tautomerism of the fluorine-substituted compounds were certified [...] Read more.
Perfluorophenyl-substituted compounds, 3-hydroxy-1,3-bis(pentafluorophenyl)-2- propen-1-one (H1) and 1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one (H22), were prepared in 56 and 30% yields, respectively, and only the enol forms were preferentially obtained among the keto-enol tautomerism. Molecular conformations and tautomerism of the fluorine-substituted compounds were certified based on X-ray crystallographic studies and density functional calculations. The solvent dependency of the absorption spectra was only observed for the fluorinated compounds. The compounds H1 and H22 quantitatively formed co-crystals with the corresponding non-perfluorinated compounds, dibenzoylmethane (H3) and 1,5-dihydroxy-1,5-diphenyl-1,4-pentadien-3-one (H24), respectively, through the arene–perfluoroarene interaction to give the 1:1 co-crystals H1•H3 and H22•H24, which were characterized by X-ray crystallographic and elemental analysis studies. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
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Open AccessArticle
New Crystal Forms for Biologically Active Compounds. Part 1: Noncovalent Interactions in Adducts of Nevirapine with XB Donors
Crystals 2019, 9(2), 71; https://doi.org/10.3390/cryst9020071
Received: 12 January 2019 / Revised: 25 January 2019 / Accepted: 29 January 2019 / Published: 30 January 2019
Cited by 1 | PDF Full-text (1443 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Stabilization of specific crystal polymorphs of an active pharmaceutical ingredient is crucial for preventing uncontrollable interconversion of various crystalline forms, which affects physicochemical properties as well as physiological activity. Co-crystallization with various excipients is an emerging productive way of achieving such stabilization in [...] Read more.
Stabilization of specific crystal polymorphs of an active pharmaceutical ingredient is crucial for preventing uncontrollable interconversion of various crystalline forms, which affects physicochemical properties as well as physiological activity. Co-crystallization with various excipients is an emerging productive way of achieving such stabilization in the solid state. In this work, we identified an opportunity for co-crystallization of antiviral drug nevirapine (NVP) with a classical XB donor, 1,2,4,5-tetrafluoro-3,6-diiodobenzene (1,4-FIB), as well as 1,3-diiodobenzene (1,3-DIB), which has been seldom employed as an XB donor to date. In the X-ray structures of NVP·1,4-FIB and NVP·1,3-DIB co-crystals, different hydrogen and halogen bonding modes were detected and further investigated via DFT calculations as well as topological analysis of the electron density distribution within the framework of the QTAIM method at the M06/DZP-DKH level of theory. Estimated energies of these supramolecular contacts vary from 0.6 to 5.7 kcal/mol. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
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