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3 pages, 191 KiB

Open AccessEditorial

Editorial: Advanced Research in Halogen Bonding

by Sergiy V. Rosokha and Atash V. Gurbanov

Crystals 2022, 12(2), 133; https://doi.org/10.3390/cryst12020133 - 19 Jan 2022

Cited by 1 | Viewed by 1413

Abstract

The Special Issue on “Advanced Research in Halogen Bonding” is a collection of 17 original articles reporting the results of theoretical and experimental studies that provide new insights into this fascinating intermolecular interaction [...] Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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12 pages, 3850 KiB

Open AccessCommunication

On the Importance of Halogen Bonding Interactions in Two X-ray Structures Containing All Four (F, Cl, Br, I) Halogen Atoms

by Dmitriy F. Mertsalov, Rosa M. Gomila, Vladimir P. Zaytsev, Mikhail S. Grigoriev, Eugeniya V. Nikitina, Fedor I. Zubkov and Antonio Frontera

Crystals 2021, 11(11), 1406; https://doi.org/10.3390/cryst11111406 - 18 Nov 2021

Cited by 32 | Viewed by 3001

Abstract

This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density [...] Read more.

This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density at the heavier halogen atoms provokes the formation of multiple Ha···Ha contacts in the solid state. That is, the heavier Ha-atoms exhibit a region of positive electrostatic potential (σ-hole) along the C–Ha bond and a belt of negative electrostatic potential (σ-lumps) around the atoms. The halogen bonding assemblies in both compounds were analyzed using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, the quantum theory of “atom-in-molecules” (QTAIM), the noncovalent interaction plot (NCIplot), and the electron localization function (ELF). Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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17 pages, 4678 KiB

Open AccessArticle

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

by Luka Fotović and Vladimir Stilinović

Crystals 2021, 11(10), 1240; https://doi.org/10.3390/cryst11101240 - 14 Oct 2021

Cited by 9 | Viewed by 3158

Abstract

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared [...] Read more.

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared them with their N-methyl-3-halopyridinium analogues. Structural analysis revealed that N-ethylated halogenopyridinium cations form slightly shorter C−X⋯I⁻ halogen bonds with iodide anion. We have also attempted synthesis of ditopic symmetric bis-(3-iodopyridinium) dications. Although successful in only one case, the syntheses have afforded two novel ditopic asymmetric monocations with an iodine atom bonded to the pyridine ring and another on the aliphatic N-substituent. Here, the C−I⋯I⁻ halogen bond lengths involving pyridine iodine atom were notably shorter than those involving an aliphatic iodine atom as a halogen bond donor. This trend in halogen bond lengths is in line with the charge distribution on the Hirshfeld surfaces of the cations—the positive charge is predominantly located in the pyridine ring making the pyridine iodine atom σ-hole more positive than the one on the alkyl chan. Full article

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8 pages, 3320 KiB

Open AccessCommunication

Synthesis and Properties of ortho-t-BuSO₂C₆H₄-Substituted Iodonium Ylides

by Tomohiro Kimura, Shohei Hamada, Takumi Furuta, Yoshiji Takemoto and Yusuke Kobayashi

Crystals 2021, 11(9), 1085; https://doi.org/10.3390/cryst11091085 - 7 Sep 2021

Cited by 7 | Viewed by 2732

Abstract

Iodonium ylides have recently attracted much attention on account of their synthetic applications. However, only a limited number of reports concerning the properties and reactivity of iodonium ylides exist, which is partly due to their instability. In this study, we synthesized several iodonium [...] Read more.

Iodonium ylides have recently attracted much attention on account of their synthetic applications. However, only a limited number of reports concerning the properties and reactivity of iodonium ylides exist, which is partly due to their instability. In this study, we synthesized several iodonium ylides that bear both an electron-withdrawing group and an aromatic ring with an ortho-t-BuSO₂ group. Based on the crystal structures of the synthesized iodonium ylides in combination with natural-bond-orbital (NBO) calculations, we estimated the strength of the intra- and intermolecular halogen-bonding interactions. In addition, we investigated the reactivity of the iodonium ylides under photoirradiation. Full article

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12 pages, 8642 KiB

Open AccessArticle

The Isocyanide Complexes cis-[MCl₂(CNC₆H₄-4-X)₂] (M = Pd, Pt; X = Cl, Br) as Tectons in Crystal Engineering Involving Halogen Bonds

by Maria V. Kashina, Daniil M. Ivanov and Mikhail A. Kinzhalov

Crystals 2021, 11(7), 799; https://doi.org/10.3390/cryst11070799 - 8 Jul 2021

Cited by 14 | Viewed by 2595

Abstract

The isocyanide complexes cis-[MCl₂(CNC₆H₄-4-X)₂] (M = Pd; X = Cl, Br; M = Pt; X = Br) form isomorphous crystal structures exhibiting the Cl/Br and Pd/Pt exchanges featuring 1D chains upon crystallisation. Crystal packing [...] Read more.

The isocyanide complexes cis-[MCl₂(CNC₆H₄-4-X)₂] (M = Pd; X = Cl, Br; M = Pt; X = Br) form isomorphous crystal structures exhibiting the Cl/Br and Pd/Pt exchanges featuring 1D chains upon crystallisation. Crystal packing is supported by the C–X···X–C halogen bonds (HaBs), C–H···X–C hydrogen bonds (HB), X···M semicoordination, and C···C contacts between the C atoms of aryl isocyanide ligands. The results of DFT calculations and topological analysis indicate that all the above contact types belong to attractive noncovalent interactions. A projection of the electron localization function (ELF) and an inspection of the electron density (ED) and the electrostatic potential (ESP) reveal the amphiphilic nature of X atoms playing the role of HaB donors, HaB and HB acceptors, and a nucleophilic partner in X···M semicoordination. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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15 pages, 20781 KiB

Open AccessArticle

Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

by Valentina Martinez, Nikola Bedeković, Vladimir Stilinović and Dominik Cinčić

Crystals 2021, 11(6), 699; https://doi.org/10.3390/cryst11060699 - 18 Jun 2021

Cited by 7 | Viewed by 2944

Abstract

In order to study the effect of halogen bond on tautomerism in β-diketones in the solid-state, we have prepared a series of cocrystals derived from an asymmetric β-diketone, benzoyl-4-pyridoylmethane (b4pm), as halogen bond acceptor and perfluorinated iodobenzenes: iodopentaflourobenzene (ipfb), [...] Read more.

In order to study the effect of halogen bond on tautomerism in β-diketones in the solid-state, we have prepared a series of cocrystals derived from an asymmetric β-diketone, benzoyl-4-pyridoylmethane (b4pm), as halogen bond acceptor and perfluorinated iodobenzenes: iodopentaflourobenzene (ipfb), 1,2-, 1,3- and 1,4-diiodotetraflorobenzene (12tfib, 13tfib and 14tfib) and 1,3,5-triiodo-2,4,6-trifluorobenzene (135titfb). All five cocrystals are assembled by I···N halogen bonds involving pyridyl nitrogen and iodoperfluorobenzene iodine resulting in 1:1 (four compounds) or 1:2 (one compound) cocrystal stoichiometry. Tautomer of b4pm in which hydrogen atom is adjacent to the pyridyl fragment was found to be more stable in vacuo than tautomer with a benzoyl hydroxyl group. This tautomer is also found to be dominant in the majority of crystal structures, somewhat more abundantly in crystal structures of cocrystals in which additional I···O halogen bond with the benzoyl oxygen has been established. Attempts have also been made to prepare an equivalent series of cocrystals using a closely related asymmetric β-diketone, benzoyl-3-pyridoylmethane (b3pm); however, all attempts were unsuccessful, which is attributed to more effective crystal packing of b3pm isomer compared to b4pm, which reduced the probability of cocrystal formation. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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12 pages, 2406 KiB

Open AccessArticle

The Amine Group as Halogen Bond Acceptor in Cocrystals of Aromatic Diamines and Perfluorinated Iodobenzenes

by Erik Uran, Luka Fotović, Nikola Bedeković, Vladimir Stilinović and Dominik Cinčić

Crystals 2021, 11(5), 529; https://doi.org/10.3390/cryst11050529 - 11 May 2021

Cited by 16 | Viewed by 4068

Abstract

In order to study the proclivity of primary amine groups to act as halogen bond acceptors, three aromatic diamines (p-phenylenediamine (pphda), benzidine (bnzd) and o-tolidine (otol)) were cocrystallised with three perfluorinated iodobenzenes (1,4-tetrafluorodiiodobenzene ( [...] Read more.

In order to study the proclivity of primary amine groups to act as halogen bond acceptors, three aromatic diamines (p-phenylenediamine (pphda), benzidine (bnzd) and o-tolidine (otol)) were cocrystallised with three perfluorinated iodobenzenes (1,4-tetrafluorodiiodobenzene (14tfib), 1,3-tetrafluorodiiodobenzene (13tfib) and 1,3,5-trifluorotriiodobenzene (135tfib)) as halogen bond donors. Five cocrystals were obtained: (pphda)(14tfib), (bnzd)(13tfib)₂, (bnzd)(135tfib)₄, (otol)(14tfib) and (otol)(135tfib)₂. In spite of the variability of both stoichiometries and structures of the cocrystals, in all the prepared cocrystals the amine groups form exclusively I···N halogen bonds, while the amine hydrogen atoms participate mostly in N–H⋯F contacts. The preference of the amine nitrogen atom toward the halogen bond, as opposed to the hydrogen bond (with amine as a donor), is rationalised by means of computed hydrogen and halogen bond energies, indicating that the halogen bond energy between a simple primary amine (methylamine) and a perfluorinated iodobenzene (pentafluoroiodobenze ne) is ca. 15 kJ mol⁻¹ higher than the energy of the (H)NH∙∙∙NH₂ hydrogen bond between two amine molecules. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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21 pages, 2935 KiB

Open AccessArticle

Halogen Bonding Involving I₂ and d⁸ Transition-Metal Pincer Complexes

by Marek Freindorf, Seth Yannacone, Vytor Oliveira, Niraj Verma and Elfi Kraka

Crystals 2021, 11(4), 373; https://doi.org/10.3390/cryst11040373 - 3 Apr 2021

Cited by 16 | Viewed by 2699

Abstract

We systematically investigated iodine–metal and iodine–iodine bonding in van Koten’s pincer complex and 19 modifications changing substituents and/or the transition metal with a PBE0–D3(BJ)/aug–cc–pVTZ/PP(M,I) model chemistry. As a novel tool for the quantitative assessment of the iodine–metal and iodine–iodine bond strength in these [...] Read more.

We systematically investigated iodine–metal and iodine–iodine bonding in van Koten’s pincer complex and 19 modifications changing substituents and/or the transition metal with a PBE0–D3(BJ)/aug–cc–pVTZ/PP(M,I) model chemistry. As a novel tool for the quantitative assessment of the iodine–metal and iodine–iodine bond strength in these complexes we used the local mode analysis, originally introduced by Konkoli and Cremer, complemented with NBO and Bader’s QTAIM analyses. Our study reveals the major electronic effects in the catalytic activity of the M–I–I non-classical three-center bond of the pincer complex, which is involved in the oxidative addition of molecular iodine I₂ to the metal center. According to our investigations the charge transfer from the metal to the

σ^{*}

antibonding orbital of the I–I bond changes the 3c–4e character of the M–I–I three-center bond, which leads to weakening of the iodine I–I bond and strengthening of the metal–iodine M–I bond, facilitating in this way the oxidative addition of I₂ to the metal. The charge transfer can be systematically modified by substitution at different places of the pincer complex and by different transition metals, changing the strength of both the M–I and the I₂ bonds. We also modeled for the original pincer complex how solvents with different polarity influence the 3c–4e character of the M–I–I bond. Our results provide new guidelines for the design of pincer complexes with specific iodine–metal bond strengths and introduce the local vibrational mode analysis as an efficient tool to assess the bond strength in complexes. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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12 pages, 5293 KiB

Open AccessEditor’s ChoiceArticle

1,4-Dibromo-2,5-bis(phenylalkoxy)benzene Derivatives: C–Br...π(arene) Versus C–H...Br and Br...Br Interactions in the Solid State

by Giacomo Manfroni, Alessandro Prescimone, Edwin C. Constable and Catherine E. Housecroft

Crystals 2021, 11(4), 325; https://doi.org/10.3390/cryst11040325 - 25 Mar 2021

Cited by 4 | Viewed by 2796

Abstract

We have prepared and characterized 1,4-dibromo-2,5-bis(2-phenylethoxy)benzene (1) and 1,4-dibromo-2,5-bis(3-phenylpropoxy)benzene (2). Their single-crystal structures confirm that, at the molecular level, they are similar with the phenylalkoxy chains in extended conformations. However, there are significant differences in packing interactions. The packing [...] Read more.

We have prepared and characterized 1,4-dibromo-2,5-bis(2-phenylethoxy)benzene (1) and 1,4-dibromo-2,5-bis(3-phenylpropoxy)benzene (2). Their single-crystal structures confirm that, at the molecular level, they are similar with the phenylalkoxy chains in extended conformations. However, there are significant differences in packing interactions. The packing in 1 is dominated by C–Br...π(arene) interactions, with each Br located over one C–C bond of the central arene ring of an adjacent molecule. In contrast, the packing of molecules of 2 involves a combination of C–H...Br hydrogen bonds, Br...Br interactions, and arene–arene π-stacking. The single-crystal structures of both orthorhombic and triclinic polymorphs of 1 have been determined and the packing interactions are shown to be essentially identical. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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12 pages, 4557 KiB

Open AccessArticle

Halogen-Bonding-Driven Self-Assembly of Solvates of Tetrabromoterephthalic Acid

by Nucharee Chongboriboon, Kodchakorn Samakun, Winya Dungkaew, Filip Kielar, Mongkol Sukwattanasinitt and Kittipong Chainok

Crystals 2021, 11(2), 198; https://doi.org/10.3390/cryst11020198 - 18 Feb 2021

Cited by 4 | Viewed by 2742

Abstract

Halogen bonding is one of the most interesting noncovalent attractions capable of self-assembly and recognition processes in both solution and solid phase. In this contribution, we report on the formation of two solvates of tetrabromoterephthalic acid (H₂Br₄tp) with acetonitrile [...] Read more.

Halogen bonding is one of the most interesting noncovalent attractions capable of self-assembly and recognition processes in both solution and solid phase. In this contribution, we report on the formation of two solvates of tetrabromoterephthalic acid (H₂Br₄tp) with acetonitrile (MeCN) and methanol (MeOH) viz. H₂Br₄tp·2MeCN (1_MeCN) and H₂Br₄tp·2MeOH (2_MeOH). The host structures of both 1_MeCN and 2_MeOH are assembled via the occurrence of simultaneous Br···Br, Br···O, and Br···π halogen bonding interactions, existing between the H₂Br₄tp molecular tectons. Among them, the cooperative effect of the dominant halogen bond in combination with hydrogen bonding interactions gave rise to different supramolecular assemblies, whereas the strength of the halogen bond depends on the type of hydrogen bond between the molecules of H₂Br₄tp and the solvents. These materials show a reversible release/resorption of solvent molecules accompanied by evident crystallographic phase transitions. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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10 pages, 2126 KiB

Open AccessEditor’s ChoiceCommunication

Role of Halogen Substituents on Halogen Bonding in 4,5-DiBromohexahydro-3a,6-Epoxyisoindol-1(4H)-ones

by Atash V. Gurbanov, Dmitriy F. Mertsalov, Fedor I. Zubkov, Maryana A. Nadirova, Eugeniya V. Nikitina, Hieu H. Truong, Mikhail S. Grigoriev, Vladimir P. Zaytsev, Kamran T. Mahmudov and Armando J. L. Pombeiro

Crystals 2021, 11(2), 112; https://doi.org/10.3390/cryst11020112 - 26 Jan 2021

Cited by 15 | Viewed by 2478

Abstract

A series of 4,5-dibromo-2-(4-substituted phenyl)hexahydro-3a,6-epoxyisoindol-1(4H)-ones were synthesized by reaction of the corresponding 2-(4-substituted phenyl)-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6H)-ones with [(Me₂NCOMe)₂H]Br₃ in dry chloroform under reflux for 3−5 h. In contrast to the 4-F and 4-Cl substituents, one of [...] Read more.

A series of 4,5-dibromo-2-(4-substituted phenyl)hexahydro-3a,6-epoxyisoindol-1(4H)-ones were synthesized by reaction of the corresponding 2-(4-substituted phenyl)-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6H)-ones with [(Me₂NCOMe)₂H]Br₃ in dry chloroform under reflux for 3−5 h. In contrast to the 4-F and 4-Cl substituents, one of the bromine atoms of the isoindole moiety behaves as a halogen bond donor in the formation of intermolecular halogen bonding in the 4-H, 4-Br and 4-I analogues. Not only intermolecular hydrogen bonds, but also Ha⋯Ha and Ha⋯π types of halogen bonds in the 4-H, 4-Br, and 4-I compounds, contribute to the formation of supramolecular architectures leading to 2D or 3D structures. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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22 pages, 18092 KiB

Open AccessArticle

5-Iodo-1-Arylpyrazoles as Potential Benchmarks for Investigating the Tuning of the Halogen Bonding

by Denisa Dumitrescu, Sergiu Shova, Isabela C. Man, Mino R. Caira, Marcel Mirel Popa and Florea Dumitrascu

Crystals 2020, 10(12), 1149; https://doi.org/10.3390/cryst10121149 - 17 Dec 2020

Cited by 14 | Viewed by 3408

Abstract

5-Iodo-1-arylpyrazoles are interesting templates for investigating the halogen bond propensity in small molecules other than the already well-known halogenated molecules such as tetrafluorodiiodobenzene. Herein, we present six compounds with different substitution on the aryl ring attached at position 1 of the pyrazoles and [...] Read more.

5-Iodo-1-arylpyrazoles are interesting templates for investigating the halogen bond propensity in small molecules other than the already well-known halogenated molecules such as tetrafluorodiiodobenzene. Herein, we present six compounds with different substitution on the aryl ring attached at position 1 of the pyrazoles and investigate them in the solid state in order to elucidate the halogen bonding significance to the crystallographic landscape of such molecules. The substituents on the aryl ring are generally combinations of halogen atoms (Br, Cl) and various alkyl groups. Observed halogen bonding types spanned by these six 5-iodopyrazoles included a wide variety, namely, C–I⋯O, C–I⋯π, C–I⋯Br, C–I⋯N and C–Br⋯O interactions. By single crystal X-ray diffraction analysis combined with the descriptive Hirshfeld analysis, we discuss the role and influence of the halogen bonds among the intermolecular interactions. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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14 pages, 3418 KiB

Open AccessArticle

Halogen Bonding in the Complexes of Brominated Electrophiles with Chloride Anions: From a Weak Supramolecular Interaction to a Covalent Br–Cl Bond

by Cody Loy, Matthias Zeller and Sergiy V. Rosokha

Crystals 2020, 10(12), 1075; https://doi.org/10.3390/cryst10121075 - 25 Nov 2020

Cited by 6 | Viewed by 2783

Abstract

The wide-range variation of the strength of halogen bonds (XB) not only facilitates a variety of applications of this interaction, but it also allows examining the relation (and interconversion) between supramolecular and covalent bonding. Herein, the Br^…Cl halogen bonding in a [...] Read more.

The wide-range variation of the strength of halogen bonds (XB) not only facilitates a variety of applications of this interaction, but it also allows examining the relation (and interconversion) between supramolecular and covalent bonding. Herein, the Br^…Cl halogen bonding in a series of complexes of bromosubstituted electrophiles (R-Br) with chloride anions were examined via X-ray crystallographic and computational methods. Six co-crystals showing such bonding were prepared by evaporation of solutions of R-Br and tetra-n-propylammonium chloride or using Cl⁻ anions released in the nucleophilic reaction of 1,4-diazabicyclo[2.2.2]octane with dichloromethane in the presence of R-Br. The co-crystal comprised networks formed by 3:3 or 2:2 halogen bonding between R-Br and Cl⁻, with the XB lengths varying from 3.0 Å to 3.25 Å. Analysis of the crystallographic database revealed examples of associations with substantially longer and shorter Br^…Cl separations. DFT computations of an extended series of R–Br^…Cl⁻ complexes confirmed that the judicious choice of brominated electrophile allows varying halogen Br^…Cl bond strength and length gradually from the values common for the weak intermolecular complexes to that approaching a fully developed covalent bond. This continuity of halogen bond strength in the experimental (solid-state) and calculated associations indicates a fundamental link between the covalent and supramolecular bonding. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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16 pages, 3966 KiB

Open AccessArticle

Halide Ion Embraces in Tris(2,2′-bipyridine)metal Complexes

by Edwin C. Constable and Catherine E. Housecroft

Crystals 2020, 10(8), 671; https://doi.org/10.3390/cryst10080671 - 3 Aug 2020

Cited by 6 | Viewed by 3317

Abstract

An analysis of the [M(bpy)₃]ⁿ⁺ (bpy = 2,2′-bipyridine) complexes with halide counterions in the Cambridge Structural Database reveals a common structural motif in two thirds of the compounds. This interaction involves the formation of 12 short C–H…X contacts between [...] Read more.

An analysis of the [M(bpy)₃]ⁿ⁺ (bpy = 2,2′-bipyridine) complexes with halide counterions in the Cambridge Structural Database reveals a common structural motif in two thirds of the compounds. This interaction involves the formation of 12 short C–H…X contacts between halide ions lying within sheets of the cations and H-3 and H-3′ of six [M(bpy)₃]ⁿ⁺ complex cations. A second motif, also involving 12 short contacts, but with H-6 and H-5, is identified between halide ions lying between sheets of the [M(bpy)₃]ⁿ⁺ cations. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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14 pages, 4204 KiB

Open AccessArticle

Crystal Structure and Supramolecular Architecture of Inorganic Ligand-Coordinated Salen-Type Schiff Base Complex: Insights into Halogen Bond from Theoretical Analysis and 3D Energy Framework Calculations

by Qiong Wu, Jian-Chang Xiao, Cun Zhou, Jin-Rong Sun, Mei-Fen Huang, Xindi Xu, Tianyu Li and Hui Tian

Crystals 2020, 10(4), 334; https://doi.org/10.3390/cryst10040334 - 23 Apr 2020

Cited by 25 | Viewed by 4179

Abstract

To identify the effects of halogen bonding in the architecture of Schiff base complex supramolecular networks, we introduced halogenated Schiff-base 3-Br-5-Cl-salen as ligand and isolated a new salen-type manganese(III) complex [Mn^III(Cl)(H₂O)(3-Br-5-Cl-salen)] (1) where 3-Br-5-Cl-salen = [...] Read more.

To identify the effects of halogen bonding in the architecture of Schiff base complex supramolecular networks, we introduced halogenated Schiff-base 3-Br-5-Cl-salen as ligand and isolated a new salen-type manganese(III) complex [Mn^III(Cl)(H₂O)(3-Br-5-Cl-salen)] (1) where 3-Br-5-Cl-salen = N,N’-bis(3-bromo-5-chlorosalicylidene)-1,2-diamine. The complex was investigated in the solid-state for halogen bonds (XBs) by single crystal X-ray structure analysis. Meanwhile, theoretical calculations were carried out to rationalize the formation mechanism of different types of XBs in the complex. The analysis result of electronic structure of the halogen bonds indicated that the chlorine atom coordinated to the Mn(III) center possesses the most negative potential and acts as anionic XB acceptor (electron donor) to the adjacent substituted halogens on the ligand, meanwhile the intermolecular Mn-Cl···X-C halogen bonding plays a significant role in directing the packing arrangement of adjacent molecules and linking the 2D layers into a 3D network. In order to verify the above results and acquire detailed information, the title complex was further analyzed by using the Hirshfeld surface analyses. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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11 pages, 1867 KiB

Open AccessArticle

Influence of Halogen Substituent on the Self-Assembly and Crystal Packing of Multicomponent Crystals Formed from Ethacridine and Meta-Halobenzoic Acids

by Artur Mirocki and Artur Sikorski

Crystals 2020, 10(2), 79; https://doi.org/10.3390/cryst10020079 - 31 Jan 2020

Cited by 8 | Viewed by 4041

Abstract

In order to determine the influence of halogen substituent on the self-assembly of the 6,9-diamino-2-ethoxyacridinium cations and 3-halobenzoate anions in the crystals formed from ethacridine and halobenzoic acids, the series of ethacridinium meta-halobenzoates dihydrates: ethacridinium 3-chlorobenzoate dihydrate (1), ethacridinium 3-bromobenzoate [...] Read more.

In order to determine the influence of halogen substituent on the self-assembly of the 6,9-diamino-2-ethoxyacridinium cations and 3-halobenzoate anions in the crystals formed from ethacridine and halobenzoic acids, the series of ethacridinium meta-halobenzoates dihydrates: ethacridinium 3-chlorobenzoate dihydrate (1), ethacridinium 3-bromobenzoate dihydrate (2), and ethacridinium 3-iodobenzoate dihydrate (3), were synthesized and structurally characterized. Single-crystal X-ray diffraction measurements showed that the title compounds crystallized in the monoclinic P2₁/c space group and are isostructural. In the crystals of title compounds, the ions and water molecules interact via N–H⋯O, O–H⋯O and C–H⋯O hydrogen bonds and π–π stacking interactions to produce blocks. The relationship between the distance X⋯O between the halogen atom (X=Cl, Br, I) of meta-halobenzoate anion and the O-atom from the ethoxy group of cation from neighbouring blocks and crystal packing is observed in the crystals of the title compounds. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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22 pages, 3834 KiB

Open AccessEditor’s ChoiceReview

On the Importance of σ–Hole Interactions in Crystal Structures

by Antonio Frontera and Antonio Bauzá

Crystals 2021, 11(10), 1205; https://doi.org/10.3390/cryst11101205 - 7 Oct 2021

Cited by 62 | Viewed by 5728

Abstract

Elements from groups 14–18 and periods 3–6 commonly behave as Lewis acids, which are involved in directional noncovalent interactions (NCI) with electron-rich species (lone pair donors), π systems (aromatic rings, triple and double bonds) as well as nonnucleophilic anions (BF₄⁻, [...] Read more.

Elements from groups 14–18 and periods 3–6 commonly behave as Lewis acids, which are involved in directional noncovalent interactions (NCI) with electron-rich species (lone pair donors), π systems (aromatic rings, triple and double bonds) as well as nonnucleophilic anions (BF₄⁻, PF₆⁻, ClO₄⁻, etc.). Moreover, elements of groups 15 to 17 are also able to act as Lewis bases (from one to three available lone pairs, respectively), thus presenting a dual character. These emerging NCIs where the main group element behaves as Lewis base, belong to the σ–hole family of interactions. Particularly (i) tetrel bonding for elements belonging to group 14, (ii) pnictogen bonding for group 15, (iii) chalcogen bonding for group 16, (iv) halogen bonding for group 17, and (v) noble gas bondings for group 18. In general, σ–hole interactions exhibit different features when moving along the same group (offering larger and more positive σ–holes) or the same row (presenting a different number of available σ–holes and directionality) of the periodic table. This is illustrated in this review by using several examples retrieved from the Cambridge Structural Database (CSD), especially focused on σ–hole interactions, complemented with molecular electrostatic potential surfaces of model systems. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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20 pages, 3413 KiB

Open AccessReview

Characterising Supramolecular Architectures in Crystals Featuring I⋯Br Halogen Bonding: Persistence of X⋯X’ Secondary-Bonding in Their Congeners

by Edward R. T. Tiekink

Crystals 2021, 11(4), 433; https://doi.org/10.3390/cryst11040433 - 16 Apr 2021

Cited by 9 | Viewed by 2223

Abstract

The Cambridge Structural Database was surveyed for crystals featuring I⋯Br secondary-bonding in their supramolecular assemblies occurring independently of other obvious supramolecular synthons and devoid of other halogen bonding interactions. In all, 41 crystals satisfied these criteria, with nine examples of zero-dimensional aggregation (uniformly [...] Read more.

The Cambridge Structural Database was surveyed for crystals featuring I⋯Br secondary-bonding in their supramolecular assemblies occurring independently of other obvious supramolecular synthons and devoid of other halogen bonding interactions. In all, 41 crystals satisfied these criteria, with nine examples of zero-dimensional aggregation (uniformly two-molecule aggregates) and 30 one-dimensional chains of varying topology (linear, zigzag and helical). There is one example each of two- and three-dimensional patterns. Type-I, type-II and intermediate bonding situations are apparent; for type-II bonding, the ratio of iodide:bromide functioning as the electrophile is 2:1. Most molecules participated, on average, in one I⋯Br contact, although smaller numbers of half (zero-dimensional) or two contacts (two- and three-dimensional) were observed. The propensity of the formation of related halogen bonding interactions in congeners of the 41 investigated crystals was also studied. Congeners were apparent for 11 crystals, with seven of these exhibiting isostructural relationships, in terms of space-group symmetry and unit-cell parameters. Isostructural relationships do not ensure the formation of analogous aggregation patterns, particularly and in accord with expectation, for the lighter halides. When formed, often distinct aggregation patterns are observed despite the isostructural relationships. Hetero-atomic halogen bonding offers surprises and opportunities in crystal engineering endeavours. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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