Different hydrogen‐bonding modes in two closely related oximes

Two closely related oximes, namely 1‐chloroacetyl‐3‐ethyl‐2,6‐diphenylpiperidin‐4‐one oxime, C₂₁H₂₃ClN₂O₂, (I), and 1‐chloroacetyl‐2,6‐diphenyl‐3‐(propan‐2‐yl)piperidin‐4‐one oxime, C₂₂H₂₅ClN₂O₂, (II), despite their identical sets of hydrogen‐bond donors and acceptors, display basically different hydrogen‐bonding patterns in their crystal structures. While the molecules of (I) are organized into typical centrosymmetric dimers, created by oxime–oxime O—H...N hydrogen bonds, in the structure of (II) there are infinite chains of molecules connected by O—H...O hydrogen bonds, in which the carbonyl O atom from the chloroacetyl group acts as the hydrogen‐bond acceptor. Despite the differences in the hydrogen‐bond schemes, the –OH groups are always in typical anti positions (C—N—O—H torsion angles of ca 180°). The oxime group in (I) is disordered, with the hydroxy groups occupying two distinct positions and C—C—N—O torsion angles of approximately 0 and 180° for the two alternatives. This disorder, even though the site‐occupancy factor of the less occupied position is as low as ca 0.06, is also observed at lower temperatures, which seems to favour the statistical and not the dynamic nature of this phenomenon.     

Intermolecular dihydrogen‐ and hydrogen‐bonding interactions in diammonium closo‐decahydrodecaborate sesquihydrate

The asymmetric unit of the title salt, 2NH₄⁺·B₁₀H₁₀²⁻·1.5H₂O or (NH₄)₂B₁₀H₁₀·1.5H₂O, (I), contains two B₁₀H₁₀²⁻ anions, four NH₄⁺ cations and three water molecules. (I) was converted to the anhydrous compound (NH₄)₂B₁₀H₁₀, (II), by heating to 343 K and its X‐ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen‐bonding interactions (N—H...O and O—H...O) and two types of dihydrogen‐bonding interactions (N—H...H—B and O—H...H—B). The N—H...H—B dihydrogen bonding forms a two‐dimensional sheet structure, and hydrogen bonding (N—H...O and O—H...O) and O—H...H—B dihydrogen bonding link the respective sheets to form a three‐dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H₂ at a faster rate than (NH₄)₂B₁₂H₁₂ and we believe that this is due to the stronger dihydrogen‐bonding interactions shown in the hydrate (I).     

Epoxy‐based networks combining chemical and supramolecular hydrogen‐bonding crosslinks

We combine the supramolecular chemistry of heterocyclic ureas with the chemistry of epoxides to synthesize new crosslinked materials incorporating both chemical and supramolecular hydrogen‐bonded links. A two‐step facile and solvent‐free procedure is used to obtain chemically and thermally stable networks from widely available ingredients: epoxy resins and fatty acids. The density of both chemical and physical crosslinks is controlled by the stoichiometry of the reactants and the use of a proper catalyst to limit side reactions. Depending on the stoichiometry, a wide range of thermomechanical properties can be attained. The method can be used to produce elastomeric objects of complex shapes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1133–1141, 2010     

Polymer/clay nanocomposites through multiple hydrogen‐bonding interactions

An 2‐ureido‐4[1H]pyrimidinone (UPy) motif with self‐association capability (through quadruple hydrogen bonds) was successfully anchored onto montmorillonite clay layers. Polymer/clay nanocomposites were prepared by specific hydrogen bonding interactions between surface functionalized silica nanoclays and UPy‐bonded supramolecular poly(ethylene glycol) or poly(?‐caprolactone). The mixed morphologies including intercalated layers with a non‐uniform separation and exfoliated single layers isolated from any stack were determined by combined X‐ray diffraction and transmission electron microscopic measurements. Thermal analyses showed that all nanocomposites had higher decomposition temperatures and thermal stabilities compared with neat polymer. The differential scanning calorimetric data implied that the crystallinity of polymers did not show essential changes upon introduction of organomodified UPy clays. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 650–658     

Fluoride anion sensing mechanism of a BODIPY‐linked hydrogen‐bonding probe

The sensing mechanism of a fluoride‐anion probe BODIPY‐amidothiourea ( 1c ) has been elucidated through the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) calculations. The theoretical study indicates that in the DMSO/water mixtures the fluorescent sensing has been regulated by the fluoride complex that formed between the probe 1c /two water molecules and the fluoride anion, and the excited‐state intermolecular hydrogen bond (H‐B) plays an important role in the fluoride sensing mechanism. In the first excited state, the H‐Bs of the fluoride complex 1cFH₂ are overall strengthened, which induces the weak fluorescence emission. In addition, molecular orbital analysis demonstrates that 1cFH₂ has more obvious intramolecular charge transfer (ICT) character in the S₁ state than 1cH₂ formed between the probe 1c and two water molecules, which also gives reason to the weaker fluorescence intensity of 1cFH₂ . Further, our calculated UV‐vis absorbance and fluorescence spectra are in accordance with the experimental measurements. © 2018 Wiley Periodicals, Inc.     

A polymorph of butobarbital with two distinct hydrogen‐bonding motifs

N—H...O bonding in a form of 5‐butyl‐5‐ethylbarbituric acid (systematic name: 5‐butyl‐5‐ethyl‐1,3‐diazinane‐2,4,6‐trione), C₁₀H₁₆N₂O₃, produces two distinct one‐dimensional motifs, viz. tape and ladder. Both are different from the ribbon chain motif observed in two previously reported polymorphs of the same compound.     

Water‐induced pseudo‐quadruple hydrogen‐bonding motifs in xanthine–inorganic acid complexes

In xanthinium nitrate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium nitrate monohydrate], C₅H₅N₄O₂⁺·NO₃⁻·H₂O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium hydrogen sulfate monohydrate], C₅H₅N₄O₂⁺·HSO₄⁻·H₂O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo‐quadruple hydrogen‐bonding motif is formed between the xanthinium cations and the water molecules via N—H...O and O—H...O hydrogen bonds in both structures, and leads to the formation of one‐dimensional polymeric tapes. These cation–water tapes are further connected by the respective anions and aggregate into two‐dimensional hydrogen‐bonded sheets in (I) and three‐dimensional arrangements in (II).     

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Development of effective organocatalysts for the living ring‐opening polymerization (ROP) of lactones is highly desired for the preparation of biocompatible and biodegradable polyesters with controlled microstructures and physical properties. Herein, a new class of hydrogen‐bond donating bisurea catalysts is reported for the ROP of lactones under solvent‐free conditions. ROP of lactones mediated by the bisurea/7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (MTBD) catalyst exhibits a living/controlled manner, affording the polymers and copolymers with the well‐defined structure, predictable molecular weight, narrow molecular weight distribution, and high selectivity for monomer at low catalyst loadings at ambient temperature. The possible mechanism of bisurea/MTBD‐catalyzed ROP of lactones is proposed, in which the bisurea activates the carbonyl group of lactones while MTBD facilitates the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding. Moreover, the poly(ε‐caprolactone‐co‐δ‐valerolactone) [P(CL‐co‐VL)] random copolymers with various compositions were synthesized using the bisurea/MTBD catalyst. The measurements of thermal properties and crystalline structure demonstrate that the CL and VL units are cocrystallized in the crystalline phase of P(CL‐co‐VL) copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 90–100     

A 16‐connected three‐dimensional hydrogen‐bonding network in tetrakis(4‐aminopyridinium) perylene‐3,4,9,10‐tetracarboxylate octahydrate

The novel title organic salt, 4C₅H₇N₂⁺·C₂₄H₈O₈⁴⁻·8H₂O, was obtained from the reaction of perylene‐3,4,9,10‐tetracarboxylic acid (H₄ptca) with 4‐aminopyridine (4‐ap). The asymmetric unit contains half a perylene‐3,4,9,10‐tetracarboxylate (ptca⁴⁻) anion with twofold symmetry, two 4‐aminopyridinium (4‐Hap⁺) cations and four water molecules. Strong N—H...O hydrogen bonds connect each ptca⁴⁻ anion with four 4‐Hap⁺ cations to form a one‐dimensional linear chain along the [010] direction, decorated by additional 4‐Hap⁺ cations attached by weak N—H...O hydrogen bonds to the ptca⁴⁻ anions. Intermolecular O—H...O interactions of water molecules with ptca⁴⁻ and 4‐Hap⁺ ions complete the three‐dimensional hydrogen‐bonding network. From the viewpoint of topology, each ptca⁴⁻ anion acts as a 16‐connected node by hydrogen bonding to six 4‐Hap⁺ cations and ten water molecules to yield a highly connected hydrogen‐bonding framework. π–π interactions between 4‐Hap⁺ cations, and between 4‐Hap⁺ cations and ptca⁴⁻ anions, further stabilize the three‐dimensional hydrogen‐bonding network.     

An unusual two‐dimensional hydrogen‐bonding network in bis(2,9‐dimethyl‐1,10‐phenanthrolin‐1‐ium) peroxodisulfate dihydrate

The title compound, 2C₁₄H₁₃N₂⁺·S₂O₈²⁻·2H₂O, is a protonated amine salt which is formed from two rather uncommon ionic species, namely a peroxodisulfate (pds²⁻) anion, which lies across a crystallographic inversion centre, and a 2,9‐dimethyl‐1,10‐phenanthrolin‐1‐ium (Hdmph⁺) cation lying in a general position. Each pds²⁻ anion binds to two water molecules through strong water–peroxo O—H...O interactions, giving rise to an unprecedented planar network of hydrogen‐bonded macrocycles which run parallel to (100). The atoms of the large R₈⁸(30) rings are provided by four water molecules bridging in fully extended form (...H—O—H...) and four pds²⁻ anions alternately acting as long (...O—S—O—O—S—O...) and short (...O—S—O...) bridges. The Hdmph⁺ cations, in turn, bind to these units through hydrogen bonds involving their protonated N atoms. In addition, the crystal structure also contains π–π and aromatic–peroxo C—H...O interactions.     

Correlation between hydrogen‐bonding interaction and mechanical properties of polyimide fibers

Novel co‐polymerization polyimide (PI) fibers based on 4,4′‐oxydianiline (ODA)‐pyromellitic dianhydride (PMDA) were prepared. 2‐(4‐Aminophenyl)‐5‐aminobenzimidazole (PABZ) containing the N? H group was introduced into the structure of the fibers as the proton donor. The results of Fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) showed that hydrogen bonding occured between the N? H group and chains, which strongly enhanced interchain interaction. This hydrogen bonding interaction increased the tensile strength and initial modulus of the PI fibers up to 2.5 times and 26 times, respectively, compared to those of homo‐PI PMDA‐ODA fibers with no hydrogen‐bonding interaction because of the absence of proton donors after the imidization process. In the mean time, glass transition temperature (T_g) of the modified PI fibers was found to be 410–440°C, which was higher than that of the homo‐PI PMDA‐ODA fibers. From the result, a novel access to molecular design and manufacture of high performance PI fibers with good properties could be provided. Copyright © 2009 John Wiley & Sons, Ltd.     

l‐Isoleucyl‐l‐asparagine 1.094‐hydrate: a hybrid hydrogen‐bonding pattern

The title compound, C₁₀H₂₀N₃O₄·1.094H₂O, crystallizes with two dipeptide molecules in the asymmetric unit, each participating in two head‐to‐tail chains with hydrogen bonds between the terminal amino and carboxylate groups. As with many other dipeptides, the resulting structure is divided into distinct layers, but as the amide groups of the two peptide molecules participate in different types of interaction, the observed hydrogen bonds within a peptide main‐chain layer (as distinct from the side‐chain/solvent regions) cannot adapt to any of the four basic patterns observed previously for dipeptides. Instead, a rare hybrid pattern is formed.     

From single‐chain folding to polymer nanoparticles via intramolecular quadruple hydrogen‐bonding interaction

Single‐chain folding via intramolecular noncovalent interaction is regarded as a facile mimicry of biomacromolecules. Single‐chain folding and intramolecular crosslinking is also an effective method to prepare polymer nanoparticles. In this study, poly(methyl methacrylate‐co?2‐ureido‐5‐deazapterines functionalized ethylene methacrylate) (P(MMA‐co‐EMA‐DeAP)) is synthesized via free radical polymerization. The single‐chain folding of P(MMA‐co‐EMA‐DeAP) and the formation of the nanoparticles in diluted solution (concentration <0.005 mg/mL) are achieved via supramolecular interaction and intramolecular collapsing during the disruption‐reformation process of the hydrogen bonding triggered by water. The size and the morphology of the nanoparticles are characterized by dynamic light scattering, transmission electron microscope, and atomic force microscope. The results show that the size of the nanoparticles depends on the molecular weight of the polymer and the loading of 2‐ureido‐5‐deazapterines functionalized ethylene methacrylate (EMA‐DeAP) on the polymer backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1832–1840     

Reaction control in radical polymerization of di‐n‐butyl itaconate utilizing a hydrogen‐bonding interaction

We have reported that intramolecular chain‐transfer reaction takes place in radical polymerization of itaconates at high temperatures and/or at low monomer concentrations. In this article, radical polymerizations of di‐n‐butyl itaconate (DBI) were carried out in toluene at 60 °C in the presence of amide compounds. The ¹³C‐NMR spectra of the obtained poly(DBI)s indicated that the intramolecular chain‐transfer reaction was suppressed as compared with in the absence of amide compounds. The NMR analysis of DBI and N‐ethylacetamide demonstrated both 1:1 complex and 1:2 complex were formed at 60 °C through a hydrogen‐bonding interaction. The ESR analysis of radical polymerization of diisopropyl itaconate (DiPI) was conducted in addition to the NMR analysis of the obtained poly(DiPI). It was suggested that the suppression of the intramolecular chain‐transfer reaction with the hydrogen‐bonding interaction was achieved by controlling the conformation of the side chain at the penultimate monomeric unit of the propagating radical with an isotactic stereosequence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4895–4905, 2004     

Supramolecular hydrogen‐bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate monohydrate (TMPDCTPC, 1:1), C₁₄H₁₉N₄O₃⁺·C₅HCl₂O₂S⁻, ( I ), trimethoprimium 3‐bromothiophene‐2‐carboxylate monohydrate, (TMPBTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂BrO₂S⁻·H₂O, ( II ), trimethoprimium 3‐chlorothiophene‐2‐carboxylate monohydrate (TMPCTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂ClO₂S⁻·H₂O, ( III ), trimethoprimium 5‐methylthiophene‐2‐carboxylate monohydrate (TMPMTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₆H₅O₂S⁻·H₂O, ( IV ), trimethoprimium anthracene‐9‐carboxylate sesquihydrate (TMPAC, 2:2:3), C₁₄H₁₉N₄O₃⁺·C₁₅H₉O₂⁻·1.5H₂O, ( V ), pyrimethaminium [or 2,4‐diamino‐5‐(4‐chlorophenyl)‐6‐ethylpyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate (PMNDCTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅HCl₂O₂S⁻, ( VI ), pyrimethaminium 5‐bromothiophene‐2‐carboxylate (PMNBTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅H₂BrO₂S⁻, ( VII ), pyrimethaminium anthracene‐9‐carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C₁₂H₁₄ClN₄⁺·C₁₅H₉O₂⁻·C₂H₅OH·H₂O, ( VIII ), and bis(pyrimethaminium) naphthalene‐1,5‐disulfonate (PMNNSA, 2:1), 2C₁₂H₁₄ClN₄⁺·C₁₀H₆O₆S₂²⁻, ( IX ), have been prepared and characterized by single‐crystal X‐ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts ( I )–( III ) and ( VI )–( IX ), the 2‐aminopyrimidinium cation interacts with the corresponding anion via a pair of N—H…O hydrogen bonds, generating the robust R₂²(8) supramolecular heterosynthon. In salt ( IV ), instead of forming the R₂²(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N—H…O hydrogen bonds. In salt ( V ), one of the carboxylate O atoms bridges the N1—H group and a 2‐amino H atom of the pyrimidinium cation to form a smaller R₂¹(6) ring instead of the R₂²(8) ring. In salt ( IX ), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R₂²(8) ring motif. In salts ( II )–( IX ), the pyrimidinium cation forms base pairs via a pair of N—H…N hydrogen bonds, generating a ring motif [R₂²(8) homosynthon]. Compounds ( II ) and ( III ) are isomorphous. The quadruple DDAA (D = hydrogen‐bond donor and A = hydrogen‐bond acceptor) array is observed in ( I ). In salts ( II )–( IV ) and ( VI )–( IX ), quadruple DADA arrays are present. In salts ( VI ) and ( VII ), both DADA and DDAA arrays co‐exist. The crystal structures are further stabilized by π–π stacking interactions [in ( I ), ( V ) and ( VII )–( IX )], C—H…π interactions [in ( IV )–( V ) and ( VII )–( IX )], C—Br…π interactions [in ( II )] and C—Cl…π interactions [in ( I ), ( III ) and ( VI )]. Cl…O and Cl…Cl halogen‐bond interactions are present in ( I ) and ( VI ), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.     

Preparation of hollow composite spheres with raspberry‐like structure based on hydrogen‐bonding interaction

The hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Particle and breath figure formation of triblock copolymers having self‐complementary hydrogen‐bonding units

Novel triblock copolymers having self‐complementary hydrogen‐bonding units were synthesized by using reversible addition–fragmentation transfer polymerization. As characterized by dynamic light scattering and atomic force microscopy, these polymers formed noncovalently crosslinked polymer particles and showed an aggregation behavior by intermolecular and intramolecular interactions. At low concentration, polymers formed nanoparticles, and the particle diameter increased with increasing polymer concentration. Well‐ordered hexagonal microstructures were prepared by “Breath Figure” technique with the triblock copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012