Presence Of Strong Hydrogen Bonds Research Articles

Pressure-induced shape and color changes and mechanical-stimulation-driven reverse transition in a one-dimensional hybrid halide

Dynamic crystals with directional deformations in response to external stimuli through molecular reconfiguration, are observed predominantly in certain organic crystals and metal complexes. Low-dimensional hybrid halides, resemble these materials due to the presence of strong hydrogen bonds between bulky organic moieties and inorganic units, whereas their dynamic behavior remains largely unexplored. Here we show that a one-dimensional hybrid halide (MV)BiBr5 (MV = methylviologen) undergoes an isosymmetric phase transition at hydrostatic pressure of 0.20 GPa, accompanied by a remarkable length expansion of 20–30% and red to dark yellow color change. Unexpectedly, the backward transition can be fully reversed by mechanical stimulation rather than decompression. In the high-pressure phase, the coexistence of strong Bi3+ lone pair stereochemical activity and large reorientations of the planar MV2+ cations, together with the newly formed CH···Br hydrogen interactions, are the structural features that facilitate microscopic changes and stabilize the metastable high-pressure phase at ambient conditions.

In situ crystallization of methanesulfonic acid, CH3SO3H, and serendipitous single crystal formation of its anhydride, (CH3)2S2O5

Methanesulfonic acid, CH3SO3H, has been crystallized using an in situ technique on a single crystal diffractometer. The crystal structure is monoclinic (P21/c, Z = 4, a = 842.07(4) pm, b = 582.20(3) pm, c = 820.38(4) pm, β = 106.459(2)°) and stamped by the presence of strong hydrogen bonds. Single crystals of the anhydride of methanesulfonic acid, (CH3)2S2O5, formed as a side product in the reaction of bis‐trimethylsilyl‐sulfate, [(CH3)3SiO]2SO2 with SO3 in a sealed glass ampoule. The monoclinic crystal structure (P21/n, Z = 12, a = 1794.5(2) pm, b = 831.75(7) pm, 1383.4(1) pm, β = 110.630(4)°) shows three crystallographically different (CH3)2S2O5 molecules in the unit cell. According to the orientation of the CH3 groups with respect to each other the (CH3)2S2O5 molecule appears as the so‐called trans‐conformer. The structure of both molecules is corroborated by quantum mechanical DFT calculations.

Hydrogen-bonded structure of hydrated water in polyvinyl pyrrolidone aqueous solution investigated by X-ray absorption and emission spectroscopy

Polyvinylpyrrolidone (PVP) is a hydrophilic polymer that is widely used in various biomedical applications owing to its excellent biocompatibility. It has been suggested that water-polymer interactions play a key role in controlling biocompatibility, although the molecular-level consequences of these interactions remain unknown. In this study, the hydrogen-bonded structures of water molecules hydrating PVP were investigated using X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES). XAS spectral profiles revealed that the CO bonds in highly concentrated PVP aqueous solutions have at least two states: one where hydrogen bonds are formed with water molecules and the other where they are not. In the XES profile of water extracted from a solution with a stoichiometric ratio of nw = 1.0, increased hydrogen bonding and hydrogen bond distortion were identified from the enhancement of 1b1′ and 3a1 peaks, respectively. Because it is difficult for water molecules to form strong hydrogen-bonded structures in tetrahedral coordination at nw = 1.0, these findings suggest that the presence of strong hydrogen bonds between the CO sites and water prevents the formation of tetrahedrally coordinated hydrogen-bonded structures among water molecules.

Low hysteresis zwitterionic supramolecular polymer ion-conductive elastomers with anti-freezing properties, high stretchability, and self-adhesion for flexible electronic devices.

The fabrication of stretchable ionic conductors with low hysteresis and anti-freezing properties to enhance the durability and reliability of flexible electronics even at low temperatures remains an unmet challenge. Here, we report a facile strategy to fabricate low hysteresis, high stretchability, self-adhesion and anti-freezing zwitterionic supramolecular polymer ion-conductive elastomers (ICEs) by photoinitiated polymerization of aqueous precursor solutions containing a newly designed zwitterionic monomer carboxybetaine ureido acrylate (CBUIA) followed by solvent evaporation. The resultant poly(carboxybetaine ureido acrylate) (PCBUIA) ICEs are highly stretchable and self-adhesive owing to the presence of strong hydrogen bonds between ureido groups and dipole-dipole interactions of zwitterions. The zwitterion groups on the polymer side chains and loaded-lithium chloride endow PCBUIA ICEs with excellent anti-freezing properties, demonstrating mechanical flexibility and ionic transport properties even at a low temperature (-20 °C). Remarkably, the PCBUIA ICEs demonstrate a low hysteresis (≈10%) during cyclic mechanical loading-unloading (≤500%), and are successfully applied as wearable strain sensors and triboelectric nanogenerators (TENGs) for energy harvesting and human motion monitoring. In addition, the PCBUIA ICE-based TENG was used as a wireless sensing terminal for Internet of Things smart devices to enable wireless sensing of finger motion state detection.

Measurement and molecular simulation of the solubility properties of 4-tert-Butyl-2, 6-dinitro-3-methoxytoluene in single and binary solvents

The solubility of 4-tert-Butyl-2, 6-dinitro-3-methoxytoluene (musk amberette) in methanol, ethanol, n-propanol, n-butanol, acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide, tetrahydrofuran and methanol + tetrahydrofuran at 278.15 K to 318.15 K were determined. All measurement data obtained good results by merging Van’t Hoff, modified Apelblat, λh, Yaws, NRTL, Wilson, Jouyban-Acree and Sun model. The deviation analysis between fitting values and experimental values indicates that the Yaws model was more effectively in fitting the solubility of musk amberette. In addition, the ΔsolH°, ΔsolG°, ΔsolS° of musk amberette solution were discussed by Van’t Hoff equation. Their fruits implied that the dissolution of musk amberette is found to be accompanied by heat absorption and entropy gain processes. This is consistent with the positive slope of the T-x1 curve, which means that high temperature is advantage for the continued dissolution of musk amberette. In contrast, the presence of strong hydrogen bonds between alcohol solvents results in their lowest solubility for musk amberette. As an important task, the melting performance and crystal structure of musk amber were tested through instruments. The same characteristics exclude the presence of solvates or polymorphs. Finally, molecular visualization analysis was used to summarize the interatomic interactions within the crystal of musk amberette. The relationship between HSP, π, α, β, CED and their ability to dissolve musk amberette was discussed. It has been proven that high CED of the solvent is the main obstacle to the dissolution of musk amberette. The interaction between the O atom of musk amberette and hydroxyl H atom of alcohol in binary mixed solutions was obtained through molecular dynamics. Further, elucidated the relationship between mixed solvents and solubility. In summary, these studies will provide strong guidance for the upgrading of musk amberette production processes.

Solubility of CO2 in Aqueous Formic Acid Solutions and the Effect of NaCl Addition: A Molecular Simulation Study.

There is a growing interest in the development of routes to produce formic acid from CO2, such as the electrochemical reduction of CO2 to formic acid. The solubility of CO2 in the electrolyte influences the production rate of formic acid. Here, the dependence of the CO2 solubility in aqueous HCOOH solutions with electrolytes on the composition and the NaCl concentration was studied by Continuous Fractional Component Monte Carlo simulations at 298.15 K and 1 bar. The chemical potentials of CO2, H2O, and HCOOH were obtained directly from single simulations, enabling the calculation of Henry coefficients and subsequently considering salting in or salting out effects. As the force fields for HCOOH and H2O may not be compatible due to the presence of strong hydrogen bonds, the Gibbs-Duhem integration test was used to test this compatibility. The combination of the OPLS/AA force field with a new set of parameters, in combination with the SPC/E force field for water, was selected. It was found that the solubility of CO2 decreases with increasing NaCl concentration in the solution and increases with the increase of HCOOH concentration. This continues up to a certain concentration of HCOOH in the solution, after which the CO2 solubility is high and the NaCl concentration has no significant effect.

Exploring Polymorphism and Diversity in Intermolecular Interactions in Substituted Crystalline Benzophenones

A detailed experimental investigation of the supramolecular features of the structural assembly and a quantitative evaluation of the various intermolecular interaction energies were performed for a total of six substituted crystalline benzophenones. Among these, two compounds, namely, 2-fluoro-4′-hydroxybenzophenone (2F4′HBZP) and 2-chloro-5-nitro benzophenone (2C5NBZP), were found to exist as concomitant dimorphs due to their conformational flexibility with respect to the carbonyl and phenyl groups. The remaining four compounds, namely, 3-fluorobenzophenone (3FBZP), 4-fluoro-4′-hydroxy benzophenone (4F4′HBZP), 2,4′-dichloro benzophenone (2C4′CBZP), and 4,4′-dichloro-3-nitro benzophenone (4,4′C3NBZP), exist as monomeric forms. Crystal packing analysis revealed the relevance of weak hydrogen bond interactions like C–H···O (with nitro and carbonyl group as hydrogen bond acceptors), C–H···F, C–H···π, and π···π interactions along with halogen bond interactions in the absence and presence of strong hydrogen bonds, like O–H···O═C, respectively. Furthermore, the quantitative interplay of electrostatic, dispersive, and repulsive contributions to the interaction energies was explored on account of the variation in the substituents on the phenyl rings in benzophenones via PIXEL calculations.

Determination of Hybrid TSPO Ligands with Minimal Impact of SNP (rs6971) through Molecular Docking and MD Simulation Study

Background: In an endeavor to ascertain high-affinity TSPO ligands with minimal single nucleotide polymorphism (SNP), six hybrid molecules have been identified as new leads for future inflammation PET imaging. Objective: Genesis for chemical design was encouraged from structural families of well-known ligands FEBMP and PBR28/ DAA1106 that have demonstrated remarkable TSPO binding characteristics. Methods: All proposed hybrid ligands 1-6 are subjected to molecular docking and simulation studies with wild and mutant protein to study their interactions, binding, consistency of active conformations and are correlated with well-established TSPO ligands. Results: Each hybrid ligand demonstrate better docking score > -11.00 kcal/mol with TSPO with respect to gold standard PK11195, i.e., -11.00 kcal/mol for 4UC3 and -12.94 kcal/mol for 4UC1. On comparison with FEBMP and GE-180 (-12.57, -7.24 kcal/mol for 4UC3 and -14.10, -11.32 kcal/mol for 4UC1), ligand 3 demonstrates maximum docking energy (> -15.50 kcal/mol) with minimum SNP (0.26 kcal/mol). Discussion: Presence of strong hydrogen bond Arg148-3.27Å (4UC1) and Trp50-2.43Å, Asp28- 2.57Å (4UC3) apart from short-range interactions, including π–π interactions with the aromatic residues, such as (Trp39, Phe46, Trp135) and (Trp39, Trp108), attributes towards its strong binding. Conclusion: Utilizing the results of binding energy, we concluded stable complex formation of these hybrid ligands that could bind to TSPO with the least effect of SNP with similar interactions to known ligands. Overall, ligand 3 stands out as the best ligand having insignificant deviations per residue of protein that can be further explored and assessed in detail for future inflammation PET application after subsequent detailed biological evaluation.

A turn-on NIR fluorescence sensor for gossypol based on Yb-based metal-organic framework

The development of analytical method for selective and sensitive detection of gossypol (Gsp), an extraction from the cotton plants, is important but still challenging in food safety and medical field. Herein, we reported a turn-on near infrared (NIR) fluorescence detection strategy for Gsp based on a metal-organic framework (MOF), QBA-Yb, which was prepared from 4,4’-(quinolone-5, 8-diyl) benzoate with Yb(NO3)3·5H2O by solvothermal synthesis. The Gsp acted as another “antenna” to sensitize the luminescence of Yb3+, leading to the turn-on NIR emission upon 467 nm excitation. As Gsp concentration increased, the NIR emission at 973 nm enhanced gradually, thus enabling highly sensitive Gsp detection in a turn-on way. The experiment and theoretical calculation results revealed the presence of strong hydrogen bonds between Gsp molecules and the MOF skeleton. The developed QBA-Yb probe showed excellent characteristics for detection of Gsp molecules, accompanied by wide linear range (5–160 μg/mL), low detection limit (0.65 μg/mL) and short response time (within 10 min). We have further demonstrated that the QBA-Yb probe was successfully applied for the determination of Gsp in real samples of cottonseeds.

L-Prolinium l-proline halogenides: a comparison of the respective chloride, bromide and iodide salts

• # Chloride, bromide and iodide salts with l -prolinium l -proline dimeric cation were studied • # Tetragonal chloride and bromide are isostructural, while iodide is orthorhombic • # Short O-H…O hydrogen bonds of dimeric cations are reflected in the infrared spectra • # Isostructural chloride and bromide are not SHG-active in agreement with Kleinman condition Structures and vibrational spectra of l -prolinium l -proline chloride (I), l -prolinium l -proline bromide (II) and l -prolinium l -proline iodide (III) were analyzed at 100K, 200K and room temperature (RT). The salts (I) and (II) are isostructural and crystallize in the tetragonal space group P 4 1 2 1 2, Z=8 at RT and in orthorhombic P 2 1 2 1 2 1 , Z=8 at 100K and 200K. The salt (III) is orthorhombic, space group P 2 1 2 1 2 1 , Z=4 at all three temperatures. The O⋅⋅⋅O distances in l -prolinium l -proline dimeric cations are equal to 2.464(3) Å (I), 2.456(3) Å (II) and 2.456(4) Å (III) at RT. The presence of strong hydrogen bonds in the crystal structures is reflected in the infrared spectra. The influence of symmetry on second harmonic activity is discussed.

Получение и свойства аминиевых солей (1-гидроксиэтилиден)дифосфоновой кислоты

An overview of the preparation methods and properties of (1-hydroxyethylidene) diphosphonic acid aminium salts is presented. (1-Hydroxyethylidene) diphosphonic acid with monoethanolamine forms a crystalline compound, which, according to the elemental analysis and XRD data, is ternary C(CH3)(OH)[P(O)O-NH3+CH2CH2OH]3[P(O)(OH)] amine salt. A characteristic feature of the derivatives of (1-hydroxyethylidene) diphosphonic acid and tris (hydroxymethyl)aminomethane is the formation of glassy and resinous products. Their composition Н4L∙4NH2C(CH2OH)3 corresponds to 4 base molecules per 1 tetrabasic acid molecule. The addition of 4 molecules of the primary amine occurs both when the ratio of the initial reagents is 1: 4 and 1: 3. The polymer structure and the presence of strong hydrogen bonds in the Н4L∙4NH2C(CH2OH)3 compound lead to its very low solubility in organic media and good solubility in water. The solubility of Н4L∙4NH2C(CH2OH)3 in methanol is 1.8 g per 100 mL. The reaction of (1-hydroxyethylidene)diphosphonic acid with para-aminobenzoic acid leads to the formation of bis(4-carboxyphenylamine)(1-hydroxyethylidene)diphosphonate C(CH3)(OH)[P(O)(OH)O-NH3+C6H4С(О)ОН]2. In a crystal, this compound consists of the anion of the double-deprotonated (1-hydroxyethylidene)diphosphonic acid C(CH3)(OH)[P(OH)(O)O-]2 and two amine cations NH3+C6H4С(О)ОН. The tetrabasic acid binds 3 molecules of morpholine, giving tris(morpholinium)(1-hydroxyethylidene)diphosphonate H4L•3HN(CH2CH2)2O in the form of a white powder that dissolves well in water, methyl and ethyl alcohols. The solid complex of morpholine with (1-hydroxyethylidene)diphosphonic acid does not crystallize from various solvents, which may be caused by the oligomeric form of morpholine included in the molecule of the complex with H4L.

Reinforcement effect of pulp fines and microfibrillated cellulose in highly densified binderless paperboards

This study investigates the use of papermaking fines as a reinforcement fibre for fully bio-based highly densified paperboards. Paperboards were prepared in a wet process followed by subsequent densification, aiming to exploit the self-bonding capabilities of cellulosic fibres without addition of synthetic binders. The cohesion of paper-based materials can be mainly attributed to the presence of strong hydrogen bonds which effectively interlink individual pulp fibres especially in highly densified paperboard. However, at a given board density, cohesion of pulp fibres may be further enhanced by adding micro- or nanoscale cellulosic fibres which provide a high surface area and thus enable extensive hydrogen bonding. In the present study, primary papermaking pulp and microfibrillated cellulose (MFC) were used to mechanically reinforce highly densified paperboards prepared from unrefined kraft pulp. All fibre materials used were characterised with regard to morphology, size distribution and dewatering behaviour (Schopper-Riegler freeness). The prepared paperboards were characterised in uniaxial tensile tests and fracture surfaces were investigated by scanning electron microscopy. As revealed by tensile tests, both reinforcement materials were highly effective, resulting in an ultimate strength increase of 50% for primary fines and 60% for MFC. Even at an addition level of 1 wt%, both reinforcement materials increased board strength by around 25%. In terms of mechanical properties, the paperboards produced in this study were found to be competitive to densified paper-based materials described in literature and similar boards which are already commercially available.

High selectivity of cyclic tetrapyrrole over tetrafuran and tetrathiophene toward toxic chemicals; A first-principles study

Abstract Although, the sensor applications of straight chain conducting polymers are well explored, but, the cyclic analogues are not much explored in this regard. The density functional theory calculations are performed to study the interaction behaviour of tetracyclic oligomers such as tetrapyrrole (4CP), tetrafuran (4CF) and tetrathiophene (4CT) for the detection of harmful gases like, phosgene, thiophosgene and formaldehyde. The most stable interaction configurations, interaction energies (Eint), interaction distance (Dint), SAPT0 energies, NCI, NBO charge transfer, HOMO-LUMO gaps and maximum absorbance are evaluated to understand the sensitivity and selectivity of these cyclic analogues toward poisonous gases. The results of all these properties illustrate that 4CP exhibits the highest sensitivity towards analytes with the sequence of formaldehyde > phosgene > thiophosgene. The interaction energies are −10.91, −9.03 and −7.58 kcal mol−1 for fd@4CP, ph@4CP and tph@4CP complexes, respectively. SAPT0 results depict that the electrostatic forces have strong influence in these complexes which indicate the presence of strong hydrogen bond between 4CP and analytes. However, this is not the case in other oligomer-analyte complexes especially in 4CT based complexes. The highest sensitivity of 4CP enables it to act as promising sensing material for formaldehyde, phosgene and thiophosgene as compared to 4CF and 4CT.

Structural, elastic, and quasiparticle bandstructure of 4,4′-Bis(nitramino)azofurazan from first principles theory

A detailed study on the properties of furazan based energetic material 4,4′-Bis(nitramino)azofurazan (DNAF) using density functional theory (DFT) is presented. Our calculated structural parameters at equilibrium are found to be in good agreement with the experimental results when the van der Waals (vdW) interactions are taken into account. The variation of the lattice parameters with respect to pressure indicates that the crystalline compound is highly compressible along the b-axis, while the calculated bulk modulus is 15 GPa. The variation of the intramolecular bond lengths with pressure shows that the bond between the nitrogen atoms in the nitramine group is more compressible than other bonds. Also, we found the presence of strong hydrogen bonds in the material. The value of elastic constants along different directions is such that C33 > C22 > C11, which can be linked to the impact sensitivity. Knowledge of accurate band gap value, being an important parameter to make a possible correlation with photodecomposition process of energetic materials is very important. As a result the band structure calculations have been carried out using GW approximation along with normal LDA/GGA which are well known to underestimate the band gaps. The calculated band gap from GW approximation found to be 4.9 eV compared to GGA band gap 1.9 eV, indicates the importance of quasiparticle correction in this study.

Finding the best density functional approximation to describe interaction energies and structures of ionic liquids in molecular dynamics studies.

Ionic liquids raise interesting but complicated questions for theoretical investigations due to the fact that a number of different inter-molecular interactions, e.g., hydrogen bonding, long-range Coulomb interactions, and dispersion interactions, need to be described properly. Here, we present a detailed study on the ionic liquids ethylammonium nitrate and 1-ethyl-3-methylimidazolium acetate, in which we compare different dispersion corrected density functional approximations to accurate local coupled cluster data in static calculations on ionic liquid clusters. The efficient new composite method B97-3c is tested and has been implemented in CP2K for future studies. Furthermore, tight-binding based approaches which may be used in large scale simulations are assessed. Subsequently, ab initio as well as classical molecular dynamics simulations are conducted and structural analyses are presented in order to shed light on the different short- and long-range structural patterns depending on the method and the system size considered in the simulation. Our results indicate the presence of strong hydrogen bonds in ionic liquids as well as the aggregation of alkyl side chains due to dispersion interactions.

A DFT study of RuO4 interactions with porous materials: metal-organic frameworks (MOFs) and zeolites.

Radioactive gaseous ruthenium tetroxide (RuO4) can be released into the environment in the case of a severe nuclear accident. Using periodic dispersion corrected density functional theory calculations, we have investigated for the first time the adsorption behavior of RuO4 into prototypical porous materials, Metal-Organic Frameworks (MOFs) and zeolites, with the aim of mitigating ruthenium releases to the outside. For the MOFs, we have screened a set of six structures (MIL-53(Al), MIL-120(Al), HKUST-1(Cu), UiO-66(Zr), UiO-67(Zr) and UiO-68(Zr)), while for the zeolites two structures have been selected: mordenite (MOR) with Si/Al ratios of 11 and 5, and faujasite (FAU) with a Si/Al ratio of 2.4. The DFT calculations show that the nature of the porous materials does not have a significant effect on the adsorption energy of RuO4 compounds and that the main interaction is due to the formation of hydrogen bonds. For the tested materials, computational results show that the interaction energies of RuO4 reach their maximum with the hydrated form of HKUST-1(Cu) (-114 kJ mol-1) due to the presence of strong hydrogen bonds between the water molecules and the oxygen atoms of RuO4.

Molecular self-assembly in indole-based benzamide derivative: Crystal structure, Hirshfeld surfaces and antimicrobial activity

Two new compounds, 1H-indole-7-amine (1) and N-(1H-indol-7-yl)-2-methylbenzamide (2) were synthesized and structurally characterized by NMR and FT-IR spectroscopic techniques. The molecular structure of compound 2 was further elucidated by single-crystal X-ray diffraction technique. Moreover, the crystal packing of compound 2 is analyzed in terms of non-covalent N-H···O, C-H···π, and parallel displaced π···π interactions. Hirshfeld surface analysis and decomposed fingerprint plots of the compound 2 were performed to visualize the presence of strong hydrogen bond N-H···O and C-H···π stacking interactions. Hirshfeld surface analysis and decomposed fingerprint plots show that the structure of compound 2 is stabilized by H···H, N-H···O, C-H···π and π···π intermolecular interactions and these interactions contribute mostly to molecular self-assembly in the crystal. In addition, compound 2 was evaluated for both their in-vitro antibacterial and antifungal activity. The obtained results have been reported, explained and compared with fluconazole and ampicillin used as reference drugs.

Pseudopolymorphs of LB30870, a Direct Thrombin Inhibitor: One-Dimensional Solvent Channel Structures Explain Reversible Hydration/Dehydration

Three different hydrates of LB30870, a new direct thrombin inhibitor, were identified during the screening of solid form, and their interconversion relationship and relative thermodynamic stabilities were investigated. Form I (hexahydrate) changes to Form II (dihydrate) or Form III (tetrahydrate) by dehydration, while Form II becomes Form I by hydration, and both Form II and Form III change to Form I in the aqueous slurry. Single crystals obtained from two different crystallization conditions, wet or air-dried, were found to be isostructural with a difference in the solvent channels, and based on the simulated and experimental powder X-ray diffraction patterns, the air-dried crystals are assigned as Form I and Form III, respectively. In all crystal structures, LB30870 is in a folded conformation forced by the presence of strong hydrogen bonds by two structural water molecules. The solvent channel formed can hold up to six additional hydration water sites per each LB30870, and the one-dimensional solvent c...

Solid-State Versatility of the Molecular Salts/Cocrystals of 2-Chloro-4-nitrobenzoic Acid: A Case Study on Halogen Bonds.

2-Chloro-4-nitrobenzoic acid (2c4n) is an antiviral agent used for the treatment of HIV infection and to boost the immune response in immune deficiency diseases. In the present study, a series of eight molecular salts of 2c4n with pyridyl and benzoic acid derivatives have been synthesized by a crystal engineering approach and were characterized structurally by various spectroscopic, thermal, and X-ray diffraction techniques. Crystal structures of all synthesized molecular salts were determined by single-crystal X-ray diffraction techniques. In all synthesized molecular salts, the charge-assisted acid···pyridine/amine heterosynthon was found to be the primary supramolecular synthon. The synthesized salts, namely, 2c4n.g and 2c4n.h salts were found to be isostructural. Further, in the current work, the occurrence of weak halogen bonds in the presence of strong hydrogen bonds in the synthesized and in the reported molecular salts/cocrystals of 2c4n has been investigated. A detailed inspection of the crystal structures of salts/cocrystals of 2c4n was carried out to demonstrate the importance of halogen bonds in these crystal structures. It was found that 4 out of 8 synthesized molecular salts and 12 out of 24 reported molecular adducts of 2c4n were found to exhibit halogen bonds in their crystal structures. A similar kind of conformational change was observed for molecular salts exhibiting halogen bonds in their crystal structures; however, the conformations were found to be slightly different in other molecular salts. It was observed that two-point primary supramolecular synthon and stronger intramolecular Cl···O halogen bonds in the molecular adducts of 2c4n are found to be more susceptible to exhibit halogen bonds in their crystal structures. Halogen bond interactions played a vital role in the crystal stabilization of these molecular adducts.

Can C[sbnd]H⋯F[sbnd]C hydrogen bonds alter crystal packing features in the presence of N[sbnd]H⋯O[dbnd]C hydrogen bond?

Intermolecular interactions involving organic fluorine have been the contemporary field of research in the area of organic solid state chemistry. While a group of researchers had refuted the importance of “organic fluorine” in guiding crystal structures, others have provided evidences for in favor of fluorine mediated interactions in the solid state. Many systematic studies have indicated that the “organic fluorine” is capable of offering weak hydrogen bonds through various supramolecular synthons, mostly in the absence of other stronger hydrogen bonds. Analysis of fluorine mediated interaction in the presence of strong hydrogen bonds has not been highlighted in detail. Hence a thorough structural investigation is needed to understand the role of “organic fluorine” in crystal engineering of small organic fluorinated molecules having the possibility of strong hydrogen bond formation in the solution and in the solid state. To fulfil this aim, we have synthesized a series of fluorinated amides using 3-methoxyphenylacetic acid and fluorinated anilines and studied their structural properties through single crystal and powder X-ray diffraction methods. Our results indicated that the “organic fluorine” plays a significant role in altering the packing characteristics of the molecule in building specific crystal lattices even in the presence of strong hydrogen bond.