Strong Intermolecular Hydrogen-bonding Interactions Research Articles

Vibrational analysis, DFT computations of spectroscopic, non-covalent analysis with molecular docking and dynamic simulation of 2-amino-4, 6-dimethyl pyrimidine benzoic acid

Vibration assignments were refined through the use of normal coordinate analysis (NCA), one of several spectroscopic computations employed in extensive investigations into the composition of 2-amino-4,6-dimethylpyrimidine benzoic acid (2ADPB). Red-shifting bands revealed N-H-O hydrogen bonding, which is corroborated by optimised geometry results and vibrational analysis. The bond length and angle have been studied through an optimized geometry at B3PW91/6–31 G (d, p) theory. FMO and NBO methods investigate chemical reactions and strength of 2ADPB. Strong intermolecular hydrogen bond interactions O13‧‧‧H27-N25 and O14-H15‧‧‧N16 have been confirmed by structural studies and remains confirmed through BCP on H15-N16, H27-O13 for 2ADPB have sturdy intermolecular hydrogen bonds interactions. MEP categorizes negative and positive sites, visualizing charge accumulation on individual atoms in the molecule. The molecule showed charge transfer, analyzed with descriptors like LOL and ELF. Kirby-Bauer method confirmed findings across bacterial strains. Molecular Docking explored ligand-protein interactions, while pharmacokinetics was studied using drug features.

Macrocyclization-induce emission enhancement characteristics of benzothiadiazole-based macrocycles: A theoretical study

We present a comprehensive investigation into the molecular structures in the ground state and the first singlet excited state, intramolecular and intermolecular interactions, as well as the emission properties of monomers, dimers and macrocycles using density functional theory and time-dependent density functional theory. Our study aims to unveil the macrocyclization-induce emission enhancement principle for benzothiadiazole-based macrocycles. Compared with the typical π-π stacking of monomers, macrocycles exhibit the tighter stacking arrangement due to the presence of strong intramolecular and intermolecular hydrogen bond interactions and the rigid triangular geometry of macrocycle, which is conducive to the enhancement of emissions efficiency. The calculated oscillator strength of macrocycles in the first excited state is much higher than that of dimers composed of two monomers. Meanwhile, the large transition electric dipole moment is beneficial for enhancing the emission efficiency. Additionally, our study reveals an emission wavelength red-shift for macrocycles after “CH”/N substitution in the acceptor moiety, and the transition mode from LUMO to HOMO can be mainly attributed to intramolecular charge transition characters from acceptor to donor fragments. Our theoretical study might provide valuable insights for the design of innovative luminescent macrocycles with high emission efficiency.

Reconstruction of Cellulose Intermolecular Interactions from Hydrogen Bonds to Dynamic Covalent Networks Enables a Thermo-processable Cellulosic Plastic with Tunable Strength and Toughness.

Its excellent renewability and biodegradability make cellulose an attractive resource to prepare fossil-based plastic alternatives. However, cellulose itself exhibits strong intermolecular hydrogen bond (H-bond) interactions, significantly restricting the mobility of cellulose chains, thus leading to poor thermo-processing performance. Here, we reconstructed the intermolecular interactions of cellulose chains via replacing the original H-bonds with dynamic covalent bonds. By this, cellulose can be easily thermo-processed into a cellulosic plastic under mild conditions (70 °C). Through adjusting the chemical structure of dynamic covalent networks, the cellulosic plastic shows tunable mechanical strength (3.0-33.5 MPa) and toughness (43-321 kJ m-2). The cellulosic plastic also exhibits excellent resistance to water, organic solvent, acid solution, alkali solution, and high temperature (>400 °C). Moreover, it owns good chemical and biological degradability and recyclability. This work provides an effective method to develop high-performance cellulosic plastics for fossil-based plastic substitution.

Structural Studies of Monounsaturated and ω-3 Polyunsaturated Free Fatty Acids in Solution with the Combined Use οf NMR and DFT Calculations-Comparison with the Liquid State.

Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons, transient 1D NOE experiments and DFT calculations demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated structures even at the low concentration of 20 mM in CDCl3. For the dimeric DHA, a structural model of an intermolecular hydrogen bond through carboxylic groups and an intermolecular hydrogen bond between the carboxylic group of one molecule and the ω-3 double bond of a second molecule is shown to play a role. In DMSO-d6 solution, NMR and DFT studies show that the carboxylic groups form strong intermolecular hydrogen bond interactions with a single discrete solvation molecule of DMSO. These solvation species form parallel and antiparallel interdigitated structures of low molecular weight, as in chloroform solution. This structural motif, therefore, is an intrinsic property of the FFAs, which is not strongly affected by the length and degree of unsaturation of the chain and the hydrogen bond ability of the solvent.

NMR and DFT studies of monounsaturated and ω-3 polyunsaturated free fatty acids in the liquid state reveal a novel atomistic structural model of DHA

Structures of low-energy conformers of caproleic acid (CA; 10:1 cis-9), oleic acid (OA; 18:1 cis-9), α-linolenic acid (ALA; 18:3 cis-9,12,15 ω-3), eicosapentaenoic acid (EPA; 20:5 cis-5,8,11,14,17 ω-3), and docosahexaenoic acid (DHA; 22:6 cis-4,7,10,13,16,19 ω-3) in the liquid state, based on detailed 1D NOE and density functional theory calculations of 1H NMR chemical shifts are presented. Transient 1D NOE experiments with variable mixing time showed significant through-space proximity of the CH2–COOH protons and the terminal CH3– groups. Variable temperature 1H NMR experiments revealed strong intermolecular centro-symmetric cyclic hydrogen bond interactions of the carboxylic groups of the monounsaturated oleic and caproleic acids (δ(COOH) ∼ 12.0–12.4 ppm), ALA and EPA (δ(COOH) ∼ 11.0 ppm). On the contrary, the carboxylic proton of DHA is strongly shielded with δ(COOH) ∼ 8.5 ppm. DFT calculations were interpreted in terms of aggregates of dimerized fatty acids with parallel and antiparallel interdigitated structures. The antiparallel arrangement was found to be in excellent agreement with experimental 1D NOE NMR data. For the dimeric DHA, a flip-flop process between a classical intermolecular centro-symmetric hydrogen bond through carboxylic groups and a novel intramolecular hydrogen bond between the carboxylic group and the terminal ω-3 double bond is demonstrated.

Cosmetic-Derived Mannosylerythritol Lipid-B-Phospholipid Nanoliposome: An Acid-Stabilized Carrier for Efficient Gastromucosal Delivery of Amoxicillin for In Vivo Treatment of Helicobacter pylori.

Helicobacter pylori infection is a leading cause of gastritis and peptic ulcer. Current treatments for H. pylori are limited by the increase in antibiotic-resistant strains and low drug delivery to the infection site, indicating the need for effective delivery systems of antibiotics. Although liposomes are the most successful drug delivery carriers that have already been applied commercially, their acidic stability still stands as a problem. Herein, we developed a novel nanoliposome using cosmetic raw materials of mannosylerythritol lipid-B (MEL-B), soy bean lecithin, and cholesterol, namely, LipoSC-MELB. LipoSC-MELB exhibited enhanced stability under the simulated gastric-acid condition, owing to its strong intermolecular hydrogen-bond interactions caused by the incorporation of MEL-B. Moreover, amoxicillin-loaded LipoSC-MELB (LipoSC-MELB/AMX) had a particle size of approximately 100 nm and exhibited sustained drug release under varying pH conditions (pH 3–7). Besides, LipoSC-MELB/AMX exhibited significantly higher anti-H. pylori and anti-H. pylori biofilm activity as compared with free AMX. Furthermore, LipoSC-MELB was able to carry AMX across the barriers of gastric mucus and H. pylori biofilms. Remarkably, in vivo assays indicated that LipoSC-MELB/AMX was effective in treating H. pylori infection and its associated gastritis and gastric ulcers. Overall, the findings of this study showed that LipoSC-MELB was effective for gastromucosal delivery of amoxicillin to improve its bioavailability for the treatment of H. pylori infection.

Decreasing the hygroscopicity of ammonium dinitramide (ADN) through cocrystallization

To decrease the hygroscopicity of ADN—a energetic oxidizer, this study developed a new cocrystal composed of ADN and 18C6 (18-crown-6) at a 1:1 ​M ratio through cocrystallization using the solvent evaporation method. The structure of the ADN/18C6 cocrystal, which has been confirmed using single X-ray diffraction (SXRD), indicates that the formation of this cocrystal is attributed to the strong intermolecular hydrogen bond interactions between ammonium ions and crown ether cycles. The ADN/18C6 cocrystal has a melting point of 151.5 ​°C, which is significantly higher than those of its respective components: 93.6 ​°C of ADN and 43.2 ​°C of 18C6. Notably, the ADN/18C6 cocrystal is nearly non-hygroscopic compared with ADN. The cocrystal's hygroscopicity rate is 0.9% when exposed to the air with relative humidity (RH) of 60% and a temperature of 30 ​°C for 12 ​h. By comparison, ADN's hygroscopicity rate is 18% under the same conditions. In addition, the impact sensitivity of the ADN/18C6 cocrystal is 18 ​J, which is substantially lower than that of raw ADN (2.5 ​J). These results show that cocrystallization offers an effective way to reduce the hygroscopicity of ADN.

Characterization of Novel Solid Dispersions of Moringa oleifera Leaf Powder Using Thermo-Analytical Techniques

Moringa oleifera leaf powder (MOLP) has been identified as the most important functional ingredient owing to its rich nutritional profile and healthy effects. The solubility and functional properties of this ingredient can be enhanced through solid dispersion technology. This study aimed to investigate the effects of polyethylene glycols (PEGs) 4000 and 6000 as hydrophilic carriers and solid dispersion techniques (freeze-drying, melting, solvent evaporation, and microwave irradiation) on the crystallinity and thermal stability of solid-dispersed Moringa oleifera leaf powders (SDMOLPs). SDMOLPs were dully characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The PXRD results revealed that the solid dispersions were partially amorphous with strong diffraction peaks at 2θ values of 19° and 23°. The calorimetric and thermogravimetric curves showed that PEGs conferred greater stability on the dispersions. The FTIR studyrevealed the existence of strong intermolecular hydrogen bond interactions between MOLP and PEG functional groups. MOLP solid dispersions may be useful in functional foods and beverages and nutraceutical formulations.

Reversible Solvatochromism of Polydiacetylenes Based on Extensively Hydrogen-Bonded Tubular Arrays

Since the pioneering discovery by Wagner, polydiacetylenes (PDAs) and their solvatochromic properties (typically blue-to-red or purple transitions) have been the subject of extensive research efforts. Without exception, PDAs have been found to undergo irreversible solvent-induced color changes, and no cases exist in which initial blue states of the PDAs are regenerated after solvent removal. Herein, we describe the first example of a reversibly solvatochromic PDA that is derived from a macrocyclic diacetylene (MCDA) containing four carboxylic acid moieties. Infrared spectroscopic studies confirmed the synergetic interplay of intra- and intermolecular hydrogen-bonding interactions to control the reversibility. The weak intramolecular hydrogen bonds allowed a solvent-induced distortion of the PDA backbone (purple state) by releasing unpolymerized monomers, while the strong and networked intermolecular hydrogen-bonding interactions ensured the rigidity of the tubular channels and served as the driving forces for the recovery of the initial conformation (blue state).

New Insights into the Structure of Glycols and Derivatives: A Comparative X-Ray Diffraction, Raman and Molecular Dynamics Study of Ethane-1,2-Diol, 2-Methoxyethan-1-ol and 1,2-Dimethoxy Ethane

In this study, we report a detailed experimental and theoretical investigation of three glycol derivatives, namely ethane-1,2-diol, 2-methoxyethan-1-ol and 1,2-dimethoxy ethane. For the first time, the X-ray spectra of the latter two liquids was measured at room temperature, and they were compared with the newly measured spectrum of ethane-1,2-diol. The experimental diffraction patterns were interpreted very satisfactorily with molecular dynamics calculations, and suggest that in liquid ethane-1,2-diol most molecules are found in gauche conformation, with intramolecular hydrogen bonds between the two hydroxyl groups. Intramolecular H-bonds are established in the mono-alkylated diol, but the interaction is weaker. The EDXD study also evidences strong intermolecular hydrogen-bond interactions, with short O···O correlations in both systems, while longer methyl-methyl interactions are found in 1,2-dimethoxy ethane. X-ray studies are complemented by micro Raman investigations at room temperature and at 80 °C, that confirm the conformational analysis predicted by X-ray experiments and simulations.

Cyanide-Bridged Polynuclear and One-Dimensional FeIII-MnIII/II Bimetallic Complexes Based-on Pentacyanoferrite(III) Building Block: Synthesis, Crystal Structures, and Magnetic Properties

In this contribution, based-on the structurally confirmed pentacyanometallate (PPh4)2[Fe(CN)5(imidazole)]·(imidazole)·H2O (1) and the manganese compounds [Mn(L)(H2O)2]ClO4 (L = N,N-ethylenebis(3-methoxysalicylideneiminate) or [Mn(MAC)(H2O)Cl]ClO4 (MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene), two new cyanide-bridged bimetallic FeIII-MnIII/II complexes [Mn(L)(H2O)]3[Fe(CN)5(imidazole)](ClO4) (2) and [Mn(MAC)][Fe(CN)5(imidazole)]·CH3OHn (3) were successfully synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals the cationic FeMn3 tetranuclear entity for complex 2, which can be further assembled into supramolecular 1D ladder-like double chain by the strong intermolecular hydrogen bond interactions. For complex 3, it can be structurally characterized as neutral one-dimensional linear single infinite chain. The magnetic investigations discover the ferromagnetic coupling between the FeIII-MnIII units in complex 2 and the antiferromagnetic coupling in complex 3 between the FeIII-MnII units through the bridging cyanide group, respectively.

Development of antioxidant and antimicrobial packaging films based on chitosan, D-α-tocopheryl polyethylene glycol 1000 succinate and silicon dioxide nanoparticles

Antioxidant and antimicrobial packaging were developed by adding D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and/or silicon dioxide nanoparticles (nano-SiO2) into chitosan (CS) films. The microstructures, physical and functional properties of CS, CS-TPGS, CS-SiO2 and CS-TPGS-SiO2 films were compared. Results showed the simultaneous addition of TPGS and nano-SiO2 into CS film produced a compact inner microstructure and strong intermolecular hydrogen bond interactions. Meanwhile, the addition of TPGS slightly increased the crystallinity of CS-TPGS and CS-TPGS-SiO2 films. By comparing different films, CS-TPGS-SiO2 film presented the lowest moisture content, water vapor and oxygen permeability, whereas the highest tensile strength and elongation at break. Moreover, CS-TPGS and CS-TPGS-SiO2 films possessed stronger free radical scavenging activity than CS and CS-SiO2 films. CS-SiO2 and CS-TPGS-SiO2 films showed higher antimicrobial activity than CS and CS-TPGS films. Notably, CS-TPGS and CS-TPGS-SiO2 film packaging effectively increased the oxidative stability of soybean oil. Our results suggest CS-TPGS-SiO2 film can be used as a novel antioxidant and antimicrobial packaging material in food industry.

Rapid analysis of carboxylic acids and esters with a direct analysis in real time ion source.

Coal oxidation produces carboxylic acids (CAs), including aliphatic acids, benzoic acids, and benzenepolycarboxylic acids, which are important fine chemicals which could be used to understand the structural features of coals. However, detecting CAs usually presents great challenges due to extremely troublesome pretreatments. Therefore, it is essential to develop an analytical method for the rapid detection of CAs from coal oxidation. A series of model compounds (MCs) of oxidation products and two practical samples were investigated by direct analysis in real time time-of-flight mass spectrometry (DART-TOFMS) under three different analytical conditions (ionizing gas temperature, organic solvent, and MC concentration). Ionizing methyl benzoate, dimethyl phthalate, and dimethyl adipate produces typical ions of methyl esters, including [M-OCH3 ]+ , [M+H]+ , and [M+NH4 ]+ . In contrast, the characteristic ions generated from CAs are polymer ions, such as [2M+NH4 ]+ , [3M+NH4 ]+ , [4M+NH4 ]+ , and [5M+NH4 ]+ , indicating the strong intermolecular hydrogen-bond interaction among CAs. Results suggest that DART-TOFMS could rapidly analyze CAs or esters in coal oxidation products according to their typical ions to further gain deep insights into the coal structure.

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9H-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imide-ether) (PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9H-xanthene and 4,4′-oxydiphthalic dianhydride (ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe3O4 nanoparticles (MNPs) which synthesized from chemical co-precipitation route were coated with silica (SiO2), sequentially with (3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde (MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe3O4 and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis (TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss (T10) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe3O4 nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.

Mussel-inspired fabrication of konjac glucomannan/microcrystalline cellulose intelligent hydrogel with pH-responsive sustained release behavior

Intelligent hydrogels are attractive biomaterials for various applications, however, fabricating a hydrogel with both adequate self-healing ability and mechanical properties remains a challenge. Herein, a series of novel intelligent konjac glucomannan (KGM)/microcrystalline cellulose (MCC) hydrogels were prepared vis the mussel-inspired chemistry. MCC was firstly functionalized by the oxidative polymerization of dopamine, and the intelligent hydrogels were obtained by mixing aqueous solutions of KGM and functionalized MCC (PDMCC). By introducing PDMCC, a more compact interconnected porous structure formed for the resulting hydrogels. The self-healing ability and mechanical properties of intelligent hydrogels were dependence on the PDMCC content. Compared with KGM hydrogels, KGM/PDMCC hydrogels exhibited a more distinct pH sensitivity and a lower initial burst release, which was attributed to the compact structure and strong intermolecular hydrogen bond interaction between PDMCC and KGM. These results suggest that the KGM/PDMCC intelligent hydrogels may be promising carriers for controlled drug delivery.

Mussel-Inspired Fabrication of Konjac Glucomannan/Poly (Lactic Acid) Cryogels with Enhanced Thermal and Mechanical Properties.

Three-dimensional nanofibers cryogels (NFCs) with both thermally-tolerant and mechanically-robust properties have potential for wide application in biomedical or food areas; however, creating such NFCs has proven to be extremely challenging. In this study, konjac glucomannan (KGM)/poly (lactic acid) (PLA)-based novel NFCs were prepared by the incorporation of the mussel-inspired protein polydopamine (PDA) via a facile and environmentally-friendly electrospinning and freeze-shaping technique. The obtained KGM/PLA/PDA (KPP) NFCs were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and compressive and tensile test. The results showed that the hierarchical cellular structure and physicochemical properties of KPP NFCs were dependent on the incorporation of PDA content. Moreover, the strong intermolecular hydrogen bond interactions among KGM, PLA and PDA also gave KPP NFCs high thermostability and mechanically-robust properties. Thus, this study developed a simple approach to fabricate multifunctional NFCs with significant potential for biomedical or food application.

Highly stable Al-doped ZnO by ligand-free synthesis as general thickness-insensitive interlayers for organic solar cells

Highly conductive and dispersible Al-doped ZnO (AZO) nanoparticles (NPs) have been successfully prepared by ligand-free colloidal synthesis at low temperature and stabilization by surfactant-aid including ethanolamine (EA), ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA). Due to the strong intermolecular hydrogen-bonding interactions between AZO NPs and the amino groups from surfactants, the inevitable aggregation was suppressed and the surface defect sites were passivated obviously. The existence of electron transfer from the nitrogen of the amino groups to the zinc of AZO, led to a dramatic increase in electrical conductivity. A homogeneous current intensity value up to ~2200 pA for AZO tread by DETA was characterized by conductive atomic force microscopy (C-AFM), which was more superior than that of the reported sol-gel synthesized AZO with the assistance of EA surfactant (refer to 170.7 pA). Furthermore, non-fullerenes solar cells based on PBDB-T:ITIC with AZO-DETA (80 nm) yielded a best device efficiency of 10.7% and kept up prominent PCE exceeding 10% even with more thicker interlayer (95 nm).

Da-KGM based GO-reinforced FMBO-loaded aerogels for efficient arsenic removal in aqueous solution

Composites based on deacetylated konjac glucomannan (Da-KGM) and graphene oxide (GO) aerogels with iron and manganese oxides (FMBO) for effective removal of arsenic from contaminated water. Da-KGM, which was used as supporting composite matrix here, were firstly treated with GO and loaded FMBO. The obtained Da-KGM/GO/FMBO composite aerogels were characterized by compression test, thermo gravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The characteristic results showed that addition of GO exhibited enhanced mechanical properties towards Da-KGM aerogels. What’s more, results of FTIR indicated the strong intermolecular hydrogen bond interaction between KGM and GO. Batch adsorption tests were used to evaluate arsenic removal capacity. Da-KGM/GO loaded FMBO composite aerogels exhibited high adsorption ability for arsenite [As(III)] and arsenate [As(V)]. The adsorption results showed that the arsenic for both arsenite [As(III)] and arsenate [As(V)] removal process followed a pseudo-second-order rate equation and Langmuir monolayer adsorption. The maximum As(III) and As(V) uptake capacity of Da-KGM/GO(10%)/FMBO composite aerogels reached 30.21mgg−1 and 12.08mgg−1 respectively according to Langmuir isotherm at pH 7 and 323K.

Topological characterization of electron density, electrostatic potential and intermolecular interactions of 2-nitroimidazole: an experimental and theoretical study.

An experimental charge density distribution of 2-nitroimidazole was determined from high-resolution X-ray diffraction and the Hansen-Coppens multipole model. The 2-nitroimidazole compound was crystallized and a high-angle X-ray diffraction intensity data set has been collected at low temperature (110 K). The structure was solved and further, an aspherical multipole model refinement was performed up to octapole level; the results were used to determine the structure, bond topological and electrostatic properties of the molecule. In the crystal, the molecule exhibits a planar structure and forms weak and strong intermolecular hydrogen-bonding interactions with the neighbouring molecules. The Hirshfeld surface of the molecule was plotted, which explores different types of intermolecular interactions and their strength. The topological analysis of electron density at the bond critical points (b.c.p.) of the molecule was performed, from that the electron density ρbcp(r) and the Laplacian of electron density ∇2ρbcp(r) at the b.c.p.s of the molecule have been determined; these parameters show the charge concentration/depletion of the nitroimidazole bonds in the crystal. The electrostatic parameters like atomic charges and the dipole moment of the molecule were calculated. The electrostatic potential surface of the molecule has been plotted, and it displays a large electronegative region around the nitro group. All the experimental results were compared with the corresponding theoretical calculations performed using CRYSTAL09.

A double stranded metal-organic assembly accommodating a pair of water trimers in the host cavity and catalysing Glaser coupling.

A supramolecular compound, catena-poly{[Cu2(1,3-μ2-(1a))2(μ2-ter)2(H2O)2]n·(6H2O)n} (1) has been synthesized using (1a) [(1a = N(1),N(3),N(5)-trimethyl-N(1),N(3),N(5)-tris((pyridin-4-yl)methyl)-1,3,5-benzene tricarboxamide] and terephthalate (ter) as the pillaring unit by self-assembly. The terephthalate units are connected by copper(II) ions forming a single strand, while a pair of such strands are then linked by (1a) via two pyridyl terminal arms bound to copper(II) nodes on either side forming a one-dimensional double stranded assembly propagating along the c axis. The compound crystallizes in the Fdd2 space group. The cavity created in the interior of this double strand assembly trap six water molecules and are stabilized by hydrogen bonding with the host. The arrangement of the pair of acyclic water trimers in isolated cavities of (1) is such that it resembles a closed-bracket-like formation. The Hirshfeld surface analysis of (1) reveals the presence of strong intermolecular hydrogen-bonding interactions between one-dimensional ladder-like units and with the water trimer in the host cavity. The copper(II)-containing coordination polymer also acts as an efficient catalyst for the Glaser-Hay homo-coupling reaction.