Utilizing "Latent" Carbon: Repositioning Hydrogen-Bonded Synthons and Assemblies via Halogen Bonding to π-Systems

Molecules bearing carboxylic acid, amide, and hydroxyl groups are ubiquitous in crystal engineering, where robust hydrogen-bonded synthons centred on these functionalities enable reliable crystal structure design. We now show that halogen bonding to the carbon π-system of such molecules, traditionally ignored in crystal engineering, permits the recognition and directional assembly of the resulting hydrogen-bonded structural subunits, leaving the archetypal hydrogen-bonded ring, ladder, and chain homosynthons intact, but repositioned in space. When applied to heteromolecular synthons, this enables rearranging more complex hydrogen-bonded motifs and the evolution of binary cocrystals into ternary ones through "latent" carbon-based recognition sites, demonstrating a rational approach to build higher-order solid-state supramolecular assemblies.

Fluorescent nano-sized aggregates of halogen bonded complexes formed using perfluoropropyl iodides: a systematic comparison between two isomeric halogen bond acceptors, aniline and 4-methyl pyridine

The halogen bonds (XB) formed by the two isomers 4-methyl pyridine (MePy) and aniline (ANL) with heptafluoro-1-propyl iodide (n-C₃F₇I) and heptafluoro-2-propyl iodide (iso-C₃F₇I) were investigated using vibrational (FT-IR and Raman) spectroscopy and quantum mechanical calculations. While these two isomers indicated a distinctive impact on the ring related vibrations, molecular electrostatic potential, frontier molecular orbitals, intermolecular electron density delocalisation and consequential charge transfer upon halogen bonding with n-C₃F₇I and iso-C₃F₇I, the dramatic intermolecular charge transfer (CT) occurring on the MePy involved XB systems demonstrated an ion-pair like aggregation. Such aggregation, after 72 h and longer after mixing, leads to an emission of fluorescence for both [MePy·C₃F₇I] systems. The resulting nano-sized aggregates were characterised using UV-Vis absorption and fluorescence spectroscopy along with scanning and transmittance electron microscopy (SEM and TEM), wherein, the XB complex with iso-C₃F₇I showed a faster and more severe aggregation due to a stronger CT than that with n-C₃F₇I. The present work is the first case of aggregation induced emission (AIE) due to aggregation of XB complexes formed by small neutral molecules.

Keggin-Type Anions as Halogen Bond Acceptors

To study the potential of Keggin-type polyoxometalate anions to act as halogen bond acceptors, we have prepared a series of 10 halogen-bonded compounds starting from phosphomolybdic and phosphotungstic acid and halogenopyridinium cations as halogen (and hydrogen) bond donors. In all the structures, the cations and the anions were interconnected by halogen bonds, more often with terminal M=O oxygen atoms than with bridging oxygen atoms as acceptors. In four structures comprising protonated iodopyridinium cations capable of forming both hydrogen and halogen bonds with the anion, the halogen bond with the anion is apparently favored, whereas hydrogen bonds preferentially involve other acceptors present in the structure. In three obtained structures derived from phosphomolybdic acid, the corresponding oxoanion has been found in its reduced state [Mo₁₂PO₄₀]^4-, which has also led to a decrease in halogen bond lengths as compared to the fully oxidated [Mo₁₂PO₄₀]^3-. The electrostatic potential on the three types of anions involved in the study ([Mo₁₂PO₄₀]^3-, [Mo₁₂PO₄₀]^4-, and [W₁₂PO₄₀]^3-) has been calculated for optimized geometries of the anions, and it has been shown that the terminal M=O oxygen atoms are the least negative sites of the anions, indicating that they act as halogen bond acceptors primarily due to their steric availability.

Anticooperativity and Competition in Some Cocrystals Featuring Iodine-Nitrogen Halogen Bonds

Phenomena such as anticooperativity and competition among non-covalent bond donors and acceptors are key considerations when exploring the polymorphic and stoichiomorphic landscapes of binary and higher-order cocrystalline architectures. We describe the preparation of four cocrystals of 1,3,5-trifluoro-2,4,6-triiodobenzene with N-heterocyclic compounds, namely acridine, 3-aminopyridine, 4-methylaminopyridine, and 1,2-di(4-pyridyl)ethane. The cocrystals, which are characterized by single-crystal and powder X-ray diffraction experiments, all show moderately strong and directional iodine⋅⋅⋅nitrogen halogen bonds with reduced distance parameters ranging from 0.79 to 0.92 and carbon-iodine⋅⋅⋅nitrogen bond angles ranging from 165.4(3) to 175.31(7)°. The cocrystal comprising 1,3,5-trifluoro-2,4,6-triiodobenzene and acridine provides a relatively rare example where all three halogen bond donor sites form halogen bonds with three acceptor molecules, overcoming an anticooperative effect. This effect manifests itself through the lengthening of non-halogen-bonded C-I bonds, weakening their potential to form halogen bonds. The effect is only observed once two halogen bonds have been formed to 1,3,5-trifluoro-2,4,6-triiodobenzene; one such bond does not appear to be adequate. Among the four cocrystals studied, competition between the pyridyl nitrogen atoms and the amine nitrogen atoms suggests that the former are the preferred halogen bond acceptors. Analysis by Hirshfeld fingerprint plots and ¹³ C and ¹⁹ F magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy provides additional insights into the prevalence of various short contacts in the crystal structures and into the spectral response to halogen-bond-induced cocrystallization.

The Halogen Bonding Proclivity of the sp3 Sulfur Atom as a Halogen Bond Acceptor in Cocrystals of Tetrahydro-4H-thiopyran-4-one and Its Derivatives

In this work, we present a systematic study of the capability of the sp³ hybridized sulfur atom for halogen bonding both in a small building block, tetrahydro-4H-thiopyran-4-one, and two larger ones derived from it, Schiff bases with a morpholine fragment on the other end of the molecule. These three building blocks were cocrystallized with six perhalogenated aromates: 1,4-diiodotetrafluorobenzene, 1,3,5-triiodotrifluorobenzene, 1,3-diiodotetrafluorobenzene, 1,2-diiodotetrafluorobenzene, iodopentafluorobenzene, and 1,4-dibromotetrafluorobenzene. Out of the 18 combinations, only 7 (39%) yielded cocrystals, although with a high occurrence of the targeted I···S halogen bonding motif in all cocrystals (71%), and in imine cocrystals the I···O_morpholine motif (100%) as well as, surprisingly, the I···N_imine motif (100%). The I···S halogen bonds presented in this work feature lower relative shortening values than those for other types of sulfur atoms; however, the sp³ sulfur atom could potentially be more specific an acceptor for halogen bonding.

Halogen Bond Motifs in Cocrystals of N,N,O and N,O,O Acceptors Derived from Diketones and Containing a Morpholine or Piperazine Moiety

In this study, we investigate the halogen bond acceptor potential of oxygen and nitrogen atoms of morpholine and piperazine fragments when they are peripherally located on N,O,O or N,N,O acceptor molecules. We synthesized four acceptor molecules derived from either acetylacetone or benzoylacetone and cocrystallized them with 1,4-diiodotetrafluorobenzene and 1,3,5-triiodotrifluorobenzene. This resulted in eight cocrystals featuring different topicities and geometric dispositions of donor atoms. In all cocrystals, halogen bonds are formed with either the morpholinyl oxygen atom or the terminal piperazine nitrogen atom. The I···O_morpholine halogen bonds feature lower relative shortening values than I···N_terminal, I···O_carbonyl, and I···N_proximal halogen bonds. The N and O halogen bond acceptor sites were evaluated through calculations of molecular electrostatic potential values.

Anticooperativity of Multiple Halogen Bonds and Its Effect on Stoichiometry of Cocrystals of Perfluorinated Iodobenzenes

To investigate influences on the topicity of perfluorinated halobenzenes as halogen bond (XB) donors in the solid state, we have conducted a database survey and prepared 18 novel cocrystals of potentially ditopic (13ditfb, 14ditfb) and tritopic (135titfb) XB donors with 15 monotopic pyridines. 135titfb shows high tendency to be mono- or ditopic, but with strong bases it can act as a tritopic XB donor. DFT calculations have shown that binding of a single acceptor molecule on one of the iodine atoms of the XB donor reduces the ESP_max on the remaining iodine atoms and dramatically decreases their potential for forming further halogen bonds, which explains both the high occurrence of crystal structures where the donors do not achieve their maximal topicity and the observed differences in halogen bond lengths. Despite the fact that this effect increases with the basicity of the acceptor, when the increase of halogen bond energy due to the basicity of the acceptor compensates its decrease due to the reduction of the acidity of the donor, it enables strong bases to form cocrystals in which a potentially polytopic XB donor achieves its maximal topicity.

Conservation of the Hydrogen-Bonded Pyridone Homosynthon in Halogen-Bonded Cocrystals

Seven cocrystals of pyridone and perfluorinated halocarbons have been prepared. In all cases pairs of pyridone molecules are connected into dimers by two N-H···O hydrogen bonds, forming the characteristic pyridone homosynthon of R₂ ²(8) topology. These dimers further act as acceptors of halogen bonds through the two pyridone oxygen atoms, forming two (in six cases) or three (in one case) halogen bonds with the donor molecules. The stoichiometry of the cocrystals obtained and the overall topology of the supramolecular architecture depend primarily on the topicity of the halogen bond donor, with the monotopic donor yielding a cocrystal of 1:1 stoichiometry comprising discrete supramolecular complexes, the ditopic donors cocrystals of 1:2 stoichiometry comprising chains, and the tritopic donor a cocrystal of 1:2 stoichiometry comprising hydrogen- and halogen-bonded layers. The results indicate that the pyridone homosynthon is a robust and reliable supramolecular synthon that is conserved in halogen-bonded cocrystals of pyridone.

Halogen bonding in cadmium(II) MOFs: its influence on the structure and on the nitroaldol reaction in aqueous medium

A solvothermal reaction of Cd(II) with the dicarboxyl-functionalized arylhydrazone pro-ligands, 5-(2-(2,4,6-trioxotetrahydro-pyrimidin-5(2H)-ylidene)hydrazineyl)isophthalic acid (H₅L¹) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)isophthalic acid (H₃L²), or their halogen bond donor centre(s) decorated analogs 2,4,6-triiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl)isophthalic acid (H₅L³) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)-2,4,6-triiodoisophthalic acid (H₃L⁴), leads to the formation of known [Cd(H₃L¹)(H₂O)₂]_n (1) and new {[Cd(HL²)(H₂O)₂(DMF)]·H₂O}_n (2), [Cd(H₃L³)]_n (3) and {[Cd₂(μ-H₂O)₂(μ-H₂L⁴)₂(H₂L⁴)₂]·2H₂O}_n (4) coordination compounds, respectively. The aggregation of mononuclear units via Cd-OC and Cd-OH₂ coordination and C_Ar-I⋯I types of intramolecular halogen bonds lead to a dinuclear tecton 4. Both C_Ar-I⋯O and C_Ar-I⋯I types of intermolecular halogen bonds play a fundamental role in the supramolecular architectures of the obtained metal-organic frameworks 3 and 4. Theoretical (DFT) calculations confirmed the presence of the C_Ar-I⋯O and C_Ar-I⋯I halogen bonds in 3 and 4 and allowed their characterisation. The formation of intermolecular noncovalent interactions between the attached iodine substituents to the hydrazone ligands and polar solvent (water or methanol) molecules promoted, at least in part, the solubility of the corresponding complexes (3 and 4), which act as homogeneous catalyst precursors in the Henry reaction between aldehydes and nitroethane. The corresponding β-nitroalkanol products were obtained in good yields (66-79%) and with good diastereoselectivity (threo/erythro ca. 72 : 28) in water at room temperature.

Halogen and Hydrogen Bond Motifs in Ionic Cocrystals Derived from 3-Halopyridinium Halogenides and Perfluorinated Iodobenzenes

Four halopyridinium salts, 3-chloro- and 3-bromopyridinium chlorides and bromides, have been successfully cocrystallized with two ditopic perfluorinated iodobenzenes, 1,4-diiodotetrafluorobenzene and 1,2-diiodotetrafluorobenzene. These halogen bond donor molecules were chosen because the different positionings of halogen bond donor atoms can lead to different supramolecular architectures. In this work, we present insight into the halogen bond acceptor potential of chloride and bromide ions, as well as the halogen bond donor potential of chlorine and bromine atoms substituted on the pyridinium ring when combined with the expectedly very strong hydrogen bonds between halopyridinium ions and free halogenide anions. A series of eight cocrystals were obtained in which three pairs of isostructural cocrystals were formed. Dominant interactions in the obtained cocrystals were charge-assisted hydrogen bonds between halopyridinium cations and halogenide ions as well as halogen bonds between halogen atoms on the pyridinium ring and halogenide ions.

Interplay of Halogen and Hydrogen Bonding through Co-Crystallization in Pharmacologically Active Dihydropyrimidines: Insights from Crystal Structure and Energy Framework

A solvent-assisted grinding method has been used to prepare co-crystals in substituted dihydropyrimidines (DHPM) that constitutes pharmacologically active compounds. These were characterized using FT-IR, PXRD, and single-crystal X-ray diffraction. In order to explore the possibility of formation of halogen (XB) and hydrogen bonding (HB) synthons in the solid state, co-crystallization attempts of differently substituted DHPM molecules, containing nitro, hydoxy, and chloro substituents, with different co-formers, such as 1,4-diiodo tetrafluorobenzene (1,4 DITFB) and 3-nitrobenzoic acid (3 NBA) were performed. The XB co-crystals (C2aXB, C2bXB, and C2cXB) prefer the formation of C-I⋅⋅⋅O/C-I⋅⋅⋅S XB synthon, whereas the HB co-crystal (C2dHB) is stabilized by N-H⋅⋅⋅O H-bond formation. Hirshfeld surface analysis revealed that the percentage contribution of intermolecular interactions for XB co-crystals prefer equal contribution of XB synthon along with HB synthon. Furthermore, the interaction energy was analyzed using energy frameworks, which suggests that their stability, a combination of electrostatics and dispersion, is enhanced through XB/HB in comparison to the parent DHPMs.

Structural and mechanistic insight into DNA bending by antitumour calicheamicins

Among the class of enediyne antibiotics endowed with potent antitumour activities, the calicheamicin derivative known as ozogamicin is selectively targeted to several leukaemia cell types by means of tailor-made immunoconjugates. Binding of these drugs to the DNA minor groove in a sequence-specific fashion eventually causes double-stranded cleavage that results in cell death. Use of calicheamicin ε, an unreactive analogue of calicheamicin γ1I, has demonstrated that these structurally sophisticated molecules inflict bending on certain DNA oligonucleotides of defined sequence to the extent that they increase their circularization ratio upon ligation into multimers. By modelling and simulating several linear and circular DNA constructs containing high-affinity 5'-TCCT-3' and low-affinity 5'-TTGT-3' target sites in the presence and absence of calicheamicin ε, we have shed light into the structural distortions introduced by the drug upon binding to DNA. This new insight not only informs about the direction and magnitude of the DNA curvature but also provides a rationale for an improved understanding of the preferred structural and dynamic features associated with DNA target selection by calicheamicins.

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

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.

Supramolecular architectures sustained by delocalised C–I⋯π(arene) interactions in molecular crystals and the propensity of their formation

A survey of delocalised C–I⋯π(chelate ring) interactions is presented.

Co-crystals of polyhalogenated diaminobenzonitriles with 18-crown-6: effect of fluorine on the stoichiometry and supramolecular structure

Fluorine in the ortho-position of diaminobenzonitrile promotes the formation of the N–H⋯NC bond which results in a 3D supramolecular structure of the co-crystal.

Crystal engineering strategies towards halogen-bonded metal–organic multi-component solids: salts, cocrystals and salt cocrystals

This highlight presents an overview of the current advances in the preparation of halogen bonded metal–organic multi-component solids, including salts and cocrystals comprising neutral and ionic constituents.

Halogen bonding in the co-crystallization of potentially ditopic diiodotetrafluorobenzene: a powerful tool for constructing multicomponent supramolecular assemblies

Halogen bonding is emerging as a significant driving force for supramolecular self-assembly and has aroused great interest during the last two decades. Among the various halogen-bonding donors, we take notice of the ability of 1,4-diiodotetrafluorobenzene (1,4-DITFB) to co-crystallize with diverse halogen-bonding acceptors in the range from neutral Lewis bases (nitrogen-containing compounds, N-oxides, chalcogenides, aromatic hydrocarbons and organometallic complexes) to anions (halide ions, thio/selenocyanate ions and tetrahedral oxyanions), leading to a great variety of supramolecular architectures such as discrete assemblies, 1D infinite chains and 2D/3D networks. Some of them act as promising functional materials (e.g. fluorescence, phosphorescence, optical waveguide, laser, non-linear optics, dielectric and magnetism) and soft materials (e.g. liquid crystal and supramolecular gel). Here we focus on the supramolecular structures of multicomponent complexes and their related physicochemical properties, highlight representative examples and show clearly the main directions that remain to be developed and improved in this area. From the point of view of crystal engineering and supramolecular chemistry, the complexes summarized here should give helpful information for further design and investigation of the elusive category of halogen-bonding supramolecular functional materials.

Exploring the Halogen-Bonded Cocrystallization Potential of a Metal-Organic Unit Derived from Copper(ii) Chloride and 4-Aminoacetophenone

In this work, we describe a novel halogen-bonded metal-organic cocrystal involving a square-planar Cu(ii) complex and 1,4-diiodotetrafluorobenzene (14tfib) by utilizing an amine ligand whose pendant acetyl group enables halogen bonding. The cocrystal was prepared by both mechanochemical synthesis (liquid-assisted grinding) and the conventional solution-based method. Crystal structure determination by single crystal X-ray diffraction revealed that the dominant supramolecular interactions are the I···O halogen bond between 14tfib and CuCl₂(aap)₂ building blocks, and the N–H···Cl hydrogen bonds between CuCl₂(aap)₂ molecules. The combination of halogen and hydrogen bonding leads to the formation of a 2D network. Overall, this work showcases an example of the possibility for extending the complexity of metal-organic crystal structures by using halogen bonding in a way that does not affect other hydrogen bonding synthons.

Straightening out halogen bonds

A new parameter is proposed to quantify the linearity of halogen bonds.

Halogen-bonded cocrystals of donepezil with perfluorinated diiodobenzenes

Donepezil, an active pharmaceutical ingredient with several different acceptor sites for halogen bonding has successfully been cocrystallized with two perfluorinated halogen bond donors.

Halogen versus Hydrogen Bonding in Binary Cocrystals: Novel Conformation a Coformer with [2+2] Photoreactivity of Criss-Crossed C=C Bonds

A series of cocrystals involving the hydrogen- and halogen-bond donor coformers catechol (cat) and 1,2-diiodotetrafluorobenzene (1,2-di-I-tFb), respectively, is reported. Each coformer forms a cocrystal with each of the three symmetric bipyridines trans-1,2-bis(n-pyridyl)ethylene (n,n'-bpe, where: n=n'=2, 3, 4). Four novel cocrystals (cat) ⋅ (3,3'-bpe), 2(1,2-di-I-tFb) ⋅ (2,2'-bpe), 2(1,2-di-I-tFb) ⋅ (3,3'-bpe), and (1,2-di-I-tFb) ⋅ (4,4'-bpe) comprise components that assemble by either O-H⋅⋅⋅N hydrogen bonds (cat) or N⋅⋅⋅I halogen bonds (1,2-di-I-tFb). In (cat) ⋅ (3,3'-bpe), cat acts as a template to support an intermolecular [2+2] photocycloaddition of 3,3'-bpe. The reactivity occurs via a one-dimensional (1D) hydrogen-bonded tape with stacked and criss-crossed olefins that react stereoselectively and quantitatively to form rctt-tetrakis(3-pyridyl)cyclobutane (3,3'-tpcb). The reactivity of the criss-crossed olefins is facilitated by a hitherto not reported cis-gauche conformation adopted by cat. The stereochemistry of 3,3'-tpcb is confirmed in the cocrystal 2(cat) ⋅ (3,3'-tpcb).

Halogen bonding of the aldehyde oxygen atom in cocrystals of aromatic aldehydes and 1,4-diiodotetrafluorobenzene

Novel halogen bonded cocrystals of aromatic aldehydes have been synthesized. We present the halogen bond acceptor potential of the aldehyde group oxygen atom in competition with the hydroxy, methoxy and pyridine groups.

Halogen-bonded cocrystals ofN-salicylidene Schiff bases and iodoperfluorinated benzenes: hydroxyl oxygen as a halogen bond acceptor

Novel halogen bondedo-hydroxy imine cocrystals with 1,3,5-triiodotrifluoro-benzene and 1,2-, 1,3- and 1,4-diiodotetrafluorobenzene have been synthesized.

Comparison of isomericmeta- andpara-diiodotetrafluorobenzene as halogen bond donors in crystal engineering

The ability ofmeta- andpara-diiodotetrafluorobenzene to act as halogen bond donors in crystal engineering has been compared by the synthesis and crystal structure analysis of a family of 20 novel halogen-bonded cocrystals with simple monotopic and ditopic nitrogen-based acceptors.

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

The halogen bonding proclivity of the chlorine atom coordinated to the Co(ii) metal centre has been explored by synthesis and crystal structure analysis of a family of 12 novel metal-based halogen-bonded cocrystals with iodine-based donors.

Mechanochemistry and cocrystallization of 3-iodoethynylbenzoic acid with nitrogen-containing heterocycles: concurrent halogen and hydrogen bonding

Halogen-bonded and hydrogen-bonded cocrystals of 3-iodoethynylbenzoic acid and several nitrogen-containing heterocycles are formed using mechanochemical and solvent-based slow evaporation methods.

Halogen and Hydrogen Bonding between (N-Halogeno)-succinimides and Pyridine Derivatives in Solution, the Solid State and In Silico

A study of strong halogen bonding within three series of halogen-bonded complexes, derived from seven para-substituted pyridine derivatives and three N-halosuccinimides (iodo, bromo and chloro), has been undertaken with the aid of single-crystal diffraction, solution complexation and computational methods. The halogen bond was compared with the hydrogen bond in an equivalent series based on succinimide. The halogen-bond energies are in the range -60 to -20 kJ mol^-1 and change regularly with pyridine basicity and the Lewis acidity of the halogen. The halogen-bond energies correlate linearly with the product of charges on the contact atoms, which indicates a predominantly electrostatic interaction. The binding enthalpies in solution are around 19 kJ mol^-1 less negative due to solvation effects. The optimised geometries of the complexes in the gas phase are comparable to those of the solid-state structures, and the effects of the supramolecular surroundings in the latter are discussed. The bond energies for the hydrogen-bonded series are intermediate between the halogen-bond energies of iodine and bromine, although there are specific differences in the geometries of the halogen- and hydrogen-bonded complexes.

Interactions between haloperfluorobenzenes and fluoranthene in luminescent cocrystals from π-hole⋯π to σ-hole⋯π bonds

From π-hole⋯π to σ-hole⋯π bonds between haloperfluorobenzenes and fluoranthene in luminescent cocrystals.

Halogen bonded cocrystals of active pharmaceutical ingredients: pyrazinamide, lidocaine and pentoxifylline in combination with haloperfluorinated compounds

Six novel halogen-bonded cocrystals of active pharmaceutical ingredients with 1,4-diiodo- and 1,4-dibromotetrafluorobenzene have been synthesized.

Endo-/exo- and halogen-bonded complexes of conformationally rigid C-ethyl-2-bromoresorcinarene and aromatic N-oxides

Unlike that of the conformationally flexibleC-ethyl-2-methylresorcinarene the structurally more rigidC_4vcavity inC-ethyl-2-bromoresorcinarene prefers only small aromaticN-oxides stabilized through C–H⋯π interactions.

The halogen bonding proclivity of the ortho-methoxy–hydroxy group in cocrystals of o-vanillin imines and diiodotetrafluoro-benzenes

Novel halogen bondedo-hydroxy imine cocrystals with 1,2-, 1,3- and 1,4-diiodotetrafluorobenzene have been synthesized. We present an insight into the halogen bond acceptor potential of theortho-methoxy–hydroxy group of theo-vanillin moiety.