Formation Of Supramolecular Network Research Articles

Assembly-Driven Oxidative Degradation of Melarsomine Triggered by Cyanuric Acid.

Molecular self-assembly can trigger or regulate specific chemical reactions that would otherwise be infeasible when molecules exist individually. Supramolecular structures can significantly affect the rate of chemical reactions; therefore, optimizing supramolecular structures by manipulating intermolecular interactions is crucial for achieving the desired reactivity. Melamine is known to form hydrogen bonds with cyanuric acid, resulting in the formation of a supramolecular network. Melarsomine, an effective medication for heartworm treatment in dogs, contains a melamine moiety. It has yet to be studied how the chemical stability of melarsomine is affected by its interaction with other molecules. Herein, we report the formation of a two-dimensional supramolecular network between melarsomine and cyanuric acid via hydrogen bonds. This network structure captures dissolved oxygen in an aqueous solution, accelerating the oxidative degradation of melarsomine.

Cyclodextrin 'Chaperones' Enable Quasi-Ideal Supramolecular Network Formation and Enhanced Photodimerization of Hydrophobic, Red-shifted Photoswitches in Water.

Precision-engineered light-triggered hydrogels are important for a diversity of applications. However, fields such as biomaterials require wavelength outside the harsh UV regime to prevent photodamage, typically requiring chromophores with extended π-conjugation that suffer from poor water solubility. Herein, we demonstrate how cyclodextrins can be used as auxiliary agents to not only solubilize such chromophores, but even to preorganize them in a 2 : 2 host-guest inclusion complex to facilitate photodimerization. We apply our concept to styrylpyrene-end-functionalized star-shaped polyethylene glycols (sPEGs). We initially unravel details of the host-guest inclusion complex using spectroscopy and mass spectrometry to give clear evidence of a 2 : 2 complex formation. Subsequently, we show that the resultant supramolecularly linked hydrogels conform to theories of supramolecular quasi-ideal model networks, and derive details on their association dynamics using in-depth rheological measurements and kinetic models. By comparing sPEGs of different arm length, we further elucidate the model network topology and the accessible mechanical property space. The photo-mediated dimerization proceeds smoothly, allowing to transform the supramolecular model networks into covalent ones. We submit that our strategy opens avenues for executing hydrophobic photochemistry in aqueous environments with enhanced control over reactivity, hydrogel topology or programmable mechanical properties.

Synthesis, structural characterization, Hirshfeld surface analysis and third-order nonlinear optical properties of Schiff bases derived from 1,1-diphenylmethylamine

Two Schiff bases namely, (E)-4-((benzhydrylimino) methyl)-N,N-dimethylaniline (I) and (E)-N-(4-isopropylbenzylidene)-1,1-diphenyl methanamine (II) were synthesized by one pot condensation reaction. The structures were confirmed by single-crystal X-ray diffraction (SXRD) analysis. The molecules are associated by C‒H···π and π···π interactions which are responsible for the formation of supramolecular network. The compounds are further characterized by FT-IR, 1H and 13C NMR spectral analysis. The UV–Vis-NIR and photoluminescence spectral data of the compounds were studied to explore the optical transmission and emission properties respectively. The surface morphological changes in the compounds were observed by scanning electron microscopic (SEM) analysis. TG-DTA methods were used to point out the thermal stability of the compounds. The third-order nonlinear optical property was investigated in detail using Z-scan technique. The optimized geometry, molecular electrostatic potential (MEP) maps, Mulliken atomic charge distribution and first-order molecular hyperpolarizability were calculated using density functional theory (DFT) calculations using the B3LYP method with 6–311 G as basis set. Intermolecular interactions were studied using 3D Hirshfeld surface maps and the percentage contributions of various interactions are studied and quantified by 2D fingerprint plots.

Structural and antioxidant properties of guanylhydrazinium pyrazine-2-carboxylate

In general, molecules with certain functional groups such as amine (-NH2) and carboxyl (-COOH) can promote the growth of co-crystals leading to the formation of supramolecular networks. However, if the differences in the pKa values of the two molecules are large [pKa (base)—pKa (acid)], salts can result instead of ‘real’ co-crystals. Here, we report the formation of such salt by letting pyrazine-2-carboxylic acid (pKa = 2.9) crystallize together with aminoguanidine (pKa = 11.5; high Δpka = 8.6) a nitrogen-rich organic base. The title salt has been prepared by slow evaporation of an equimolar ratio of guanylhydrazine bicarbonate (i.e., aminoguanidine bicarbonate (AgunH.HCO3)) and pyrazine-2-carboxylic acid (Pymca) in aqueous medium. The salt was characterized by IR spectroscopy, powder and single-crystal X-ray diffraction techniques. This material shows enhanced antioxidant activity and this is due to the crucial role of hydrazinic moiety in the aminoguanidinium salt.

DNA interaction analysis with automated biosensor of paraben derivative s-triazines

Among all heterocyclic compounds, the triazine scaffold has an important place due to its wide range of biological activities. Triazine has been preferred by many researchers as the target structure for the design and development of new drugs, as it is found in many biologically active molecules with promising biological potential such as anti-inflammatory, anti-mycobacterial, anti-viral, anti-cancer properties. In this study, a series of paraben substituted s-triazine compounds 1-5 were synthesized and their structures were determined by 1H and 13C NMR spectroscopies as well as mass spectrometry. Also, structure of compound 5 was adjusted by X-ray crystallographic technique and crystallographic analysis revealed that 5 was crystallized in the trigonal space group R-3. According to X-ray analysis, compound 5 has very important intermolecular interaction such as nonclassical H-bond and pi-pi interaction. These interactions lead formation of supramolecular network. The thermal stabilities were investigated by thermogravimetric analysis. According to thermogravimetric analysis results, all of the synthesized compounds have high thermal stability. DNA interaction studies of the compounds 1-5 were performed with an automatic biosensor device that can measure the efficiency of DNA hybridization on the biochip surface. The biosensor results show that benzyl paraben substituted s-triazine compound 5, the most reactive compound at low concentration, was showed 61% and 75% activity reduction at concentrations 12.5 and 25 µM.

Synthesis and structural characterization of Zn(II) and Cd(II) ion directed coordination networks and their template-free fabrication to metal oxide nanomaterials

Using a tetradentate capping ligand, N,N,N-tris(2-pyridylmethyl)-amine (tpa) and acetylene dicarboxylic acid (H2adc), structural diversity is achieved with two group 12 divalent metal ions, Zn(II) and Cd(II). With a change in metal center, a discrete molecule [Zn2(tpa)2(adc)2].5H2O (1) and a water soluble coordination polymer [Cd(tpa)(adc)]n (2) are isolated under the same reaction conditions. Furthermore, the formation of supramolecular networks of higher dimensionality in 1 and 2 has different associations: hydrogen bonding interactions between lattice water molecules and the uncoordinated oxygen atoms of adc are primarily involved in 1, whereas π-π interactions between pyridyl moieties are responsible for it in 2. Both 1 and 2 are characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis (TGA), single crystal and powder X-ray diffraction. The exceptional thermal stability of 2 compared to 1 based on TGA is correlated to their structural differences. The template-free ecofriendly and efficient fabrication of 1 and 2 to the corresponding metal oxide nanomaterials (ZnO and CdO, respectively) was achieved via the direct calcination method but without any external reagent such as surfactants. Furthermore, a temperature-dependent (400–600 °C) diversification of size and morphology of both ZnO and CdO has established the value of such precursors.

The effect of the change in substituents’ positions on the formation of supramolecular networks and the solvent type/substituent dependence of prototropic behavior in three new o-hydroxy Schiff bases

The effect of substituent position on the formation of supramolecular topology, intra-molecular geometry and tautomeric behavior, and the dependence of prototropy on the solvent type have been investigated applying the XRD, UV–Vis, NMR, DFT, PES and HOMA methods on three new o-hydroxy Schiff bases. Based on key geometric parameters, total molecular energy and aromaticity calculations, the XRD, DFT and HOMA studies propose the phenol-imine structure as the most consistent tautomeric form for the compounds. PES and HOMA studies give results that relate the preference of the phenol-imine form to its high π-electron delocalization. For the solvent type dependence of tautomerism, the investigation of UV–Vis and NMR spectra and the PES studies for different solvent media reveals that the co-existence of two tautomeric structures becomes easier by increasing solvent polarity. As to the effect of substituent position on the supramolecular topology, XRD studies show that different substituent positions cause different types of non-covalent inter-molecular interactions in the crystal packings of the compounds. This is resulted in a significant change in the formation and topology of the supramolecular architecture, emphasizing the importance of a substituent position as a regulator in crystal engineering.

Controlling of the 2D Self-Assembly Process by the Variation of Molecular Geometry

In this paper, we check how the molecular architecture influences the self-assembly process of tetrapod molecules. These particles were built of the linear core and four attached arms. For this purpose, we employ molecular dynamics simulation together with the lattice Monte Carlo method to investigate the formation of supramolecular networks. To characterize them, we evaluated structure parameters such as distribution of the core–core angle, average degree of association, and theoretical diffractograms. Moreover, we conclude that for the latter parameter, the influence of the rotation of differently oriented domains may lead to wrong interpretation of results.

Bio-based epoxidized natural rubber/chitin nanocrystals composites: Self-healing and enhanced mechanical properties

A kind of epoxidized natural rubber (ENR)/CNCs composites without using conventional crosslinking agents was successfully fabricated in this paper, in which a supramolecular network based on hydrogen bonds is formed. FTIR confirmed that parts of hydroxyl groups of CNCs reacted with the epoxy group of ENR and hydrogen bonds were developed between CNCs and ENR. This made CNCs involve in the formation of supramolecular network, effectively improving the mechanical properties and endowing the ENR/CNCs composites with superior self-healing capacity simultaneously. The tensile strength of ENR/CNCs composites with 20 wt% CNCs rises to 1.19 MPa, almost 2 times than that of the neat ENR. Importantly, the ENR/CNCs composite with a filler loading of 20 wt% exhibits impressive self-healing efficiency of 83% of the its original strength and 95% of the original extensibility without any external stimulus at room temperature. Healing behavior is strongly influenced by CNCs contents, healing temperature, healing time and its times.

Scrutinizing the two new o-hydroxy Schiff bases from the point of tautomeric behavior and non-covalent interactions (H-bond, Br⋯Br, π⋯π and C[sbnd]H⋯π) in their supramolecular architectures

Two new Schiff bases, (E)-4,6-dibromo-2-[(5-chloro-2-methylphenylimino)methyl]-3-methoxyphenol (1) and (E)-4-bromo-2-[(4-bromophenylimino)methyl]-5-methoxyphenol (2), have been investigated by focusing on the prototropy-related-changes in the geometric parameters, the molecular planarity and the way of crystal packing. X-ray diffraction (XRD), density functional theory (DFT), Hartree-Fock theory (HF) and Møller–Plesset perturbation theory (MP2) and harmonic oscillator model of aromaticity (HOMA) studies show the preference of phenol-imine form by the compounds. The crystal packings of the compounds have been studied in detail by noting the importance of the substituent type and position in regulating the non-covalent interactions, thus, the formation of supramolecular networks. The results underline the fact that the halogen atoms of high polarizability and their presence in the appropriate position dominate the construction of supramolecular structure in Schiff bases.

Synthesis, Structure and Magnetic Study of a Di-Iron Complex Containing N-N Bridges

The iron (II) coordination compound, {[Fe(3,6 pzdc)](H2O)2}2. (1) has been synthesized from a mixture of FeCl2.4H2O and pyridazinedicarboxylate (3,6 pzdc). The molecular structure of complex 1 was determined by single crystal X-ray diffraction study. It reveals that the dinuclear structure contains a pyridazine bridge in between the two metal centers. The variable temperature magnetic study results in g = 2.496(8), J = −2.50(8) cm−1, Ɵ = −0.1 K values, by fitting the magnetic data in a simple dinuclear Fe-Fe model which indicates that the major exchange pathway through the N-N bridge. Presence of dense H-bonding interaction leads to supramolecular network formation.

Synthesis, crystal structure, DNA binding and in vitro cytotoxicity studies of Zn(II) complexes derived from amino-alcohol Schiff-bases

Three new zinc(II) complexes, namely, [Zn2(H2L1)2(OAc)2] (1), [Zn3(H2L1)2(OAc)4] (2) and {[Zn3(H2L2)2(OAc)4]·C2H5OH·DMF} (3) [(H3L1 = Schiff-base derived from salicylaldehyde and 2-amino-2-ethyl-1,3-propanediol and H3L2 = Schiff-base derived from 5-chlorosalicylaldehyde and 2-amino-2-ethyl-1,3-propanediol)], were synthesized and characterized using elemental analyses, infrared spectroscopy and X-ray diffraction. Single crystal structure analysis reveals that complex 1 is five-coordinated distorted square pyramidal configuration. Complexes 2 and 3 exhibit the similar trinuclear structure. And the alkoxy groups in the ligands are play an important role in the formation of supramolecular networks of complexes 1–3. The interaction of the complexes 1–3 with calf thymus (CT) DNA was investigated using UV–visible (UV–Vis), circular dichroism spectra (CD), fluorescence, viscosity and thermal denaturation methods. The intrinsic binding constants for the complexes are found to order of 104 indicating that the complexes are good metallo-intercalators. Complex 1 shows maximum binding affinity (Kb: 7.64 × 104) compared to others. The all complexes can bind to CT-DNA via intercalative mode. The MTT assay show that the cytotoxicity of dinuclear complex 1 is more effective with HeLa cancerous cells. All the experimental results are suggestive that the nuclearity and configuration of zinc complexes have significant influence on their properties.

Fast formation of a supramolecular ion gel/solvoplastic elastomer with excellent stretchability.

This study describes a simple yet efficient approach for the preparation of an ionic gel that is also elastomeric in its solid-state bulk form. A series of poly(2-(diethylamino)ethyl methacrylate-co-lauryl methacrylate) P(DMAEMA-co-LMA) copolymers were synthesized first by radical polymerization. Quaternization of the PDMAEMA component in tetrahydrofuran enables the formation of supramolecular network, giving rise to an ion gel. An elastomer with an elongation at break of over 600% was obtained from the gel. The elastomer, connected by supramolecular ionic cross-links, is solvoplastic in certain solvents. The simple yet efficient approach of the formation of ion-gel and the dried elastomer allows fast preparation of both gel-like and solid-state elastic materials for various applications where recyclability is required.

Ladder-Type Poly(3,4-ethylenedioxythiophene)–Poly(ethylene glycol)–Polyurethane Supramolecular Network for Gel Polymer Electrolyte

ABSTRACTA ladder-type poly(3,4-ethylenedioxythiophene)–poly(ethylene glycol)–polyurethane (PEDOT–PEG–PU) supramolecular network was successfully synthesized using graft copolymerization of hydroxymethyl-EDOT with isocyanate-terminated PEG–PU prepolymer. PEDOT functionalized as the frame for a ladder-type supramolecular structure and PEG–PU as the rung. The successful formation of supramolecular network was confirmed by analyzing the Fourier transform infrared spectroscopy. A series of PEDOT–PEG–PU gel polymer electrolytes by linking the LiClO4 were prepared as a function of [O/Li+] ratios. The pH effect of their electrical capacitances was investigated using cyclic voltammetry. Ionic conductivities of different PEDOT–PEG–PU/Li+ complexes at a fixed pH were also evaluated through impedance analysis.

Co(II) Induced Aggregation of Chiral Perylene Derivatives and Macroscopic Formation of Supramolecular Networks

Metal directed supramolecular chiral network of perylene diimide with high stretchability is demonstrated. The self-healing property of the hydrogel network has been utilized for making healable electrical circuits.

Supramolecular heterosynthon assemblies of ortho-phenylenediamine with substituted aromatic carboxylic acids

Co-crystallization experiments conducted between ortho-phenylenediamine (OPDA) and five substituted aromatic acids (phthalic acid, salicylic acid, 4-hydroxybenzoic acid, 4-nitrobenzoic acid and 3,5-dinitrobenzoic acid) reveal the formation of supramolecular networks constructed from acid–base heterosynthons of ortho-phenylenediammonium cations with respective aromatic anions. All of these coformers are generally regarded as safe (GRAS) molecules. The five reported crystal structures are sustained predominantly by intermolecular N+−H...O−, N—H...O− and N—H...O hydrogen-bonding interactions; in addition intramolecular O—H...O and intermolecular O—H...O, O—H...O− and C—H...O interactions contribute to the formation of various networks. Five 1:1 salts [NH2C6H4NH3]+·[COOHC6H4COO]− (1); [NH2C6H4NH3]+·[OHC6H4COO]− (2); [{NH2C6H4NH2}2·{OHC6H4COOH}2·{NH2C6H4NH3}+ 2·{OHC6H4COO}− 2] (OPDPHB) (3); [NH2C6H4NH3]+·[NO2C6H4COO]− (4) and [NH2C6H4NH3]+·[(NO2)2C6H4COO]− (5) were isolated as single crystals by the slow evaporation method and were characterized using spectroscopic and X-ray crystallographic techniques. X-ray diffraction studies confirmed the formation of salts. The pK a difference between the amine and respective acid favours the transfer of a proton from the acid to the amine, which leads to the formation of the anion and the cation. The interactions between these ions resulted in a stable heterosynthon in each case. The asymmetric units of salts (1), (2), (4) and (5) contain one anion and one cation each, but salt (3) consists of two anions, two cations and two neutral species in its asymmetric unit. A polymorph of salt (3) was also isolated from the crystallization of the ground material from liquid-assisted grinding [{NH2C6H4NH2}·{NH2C6H4NH3}+·{OHC6H4COO}−] (OPDPHB 3P). The polymorph crystallized in the monoclinic non-centrosymmetric space group P21. The liquid-assisted grinding experiments using a 1:1 ratio also revealed the formation of the expected salts, except salt (3), where this product matches with polymorph (OPDPHB 3P).

Hierarchical formation of Fe-9eG supramolecular networks via flexible coordination bonds.

From the interplay between high-resolution scanning tunneling microscopy imaging/manipulations and density functional theory calculations, we display the hierarchical formation of supramolecular networks by codeposition of 9eG molecules and Fe atoms on Au(111) based on the flexible coordination bonds (the adaptability and versatility in the coordination modes). In the first step, homochiral islands composed of homochiral G4Fe2 motifs are formed; and then in the second step, thermal treatment results in the transformation into the porous networks composed of heterochiral G4Fe2 motifs with the ratio of the components being constant. In situ STM manipulations and the coexistence of some other heterochiral G4Fe2 motifs and clusters also show the flexibility of the coordination bonds involved. These studies may provide a fundamental understanding of the regulations of multilevel supramolecular structures and shed light on the formation of designed supramolecular nanostructures.

Ladder-Type Poly(3,4-ethylenedioxythiophene)-Poly (ethylene glycol)-Polyurethane Supramolecular Network for Gel Polymer Electrolyte

ABSTRACTA ladder-type poly(3,4-ethylenedioxythiophene)-poly (ethylene glycol)-polyurethane (PEDOT-PEG-PU) supramolecular network was successfully synthesized using graft copolymerization of hydroxymethyl-EDOT with isocyanate-terminated PEG-PU prepolymer. PEDOT functionalized as the frame for a ladder-type supramolecular structure and PEG-PU as the rung. The successful formation of supramolecular network was confirmed by analyzing the Fourier transform infrared spectroscopy (FTIR). A series of PEDOT-PEG-PU gel polymer electrolyte by linking the LiClO4 were prepared as a function of [O/Li+] ratios. The pH effect of their electrical capacitances was investigated using cyclic voltammetry. Ionic conductivities of different PEDOT-PEG-PU/Li+ complexes at a fixed pH were also evaluated through impedance analysis.

Two-Component Self-Assembly: Hierarchical Formation of pH-Switchable Supramolecular Networks by π-π Induced Aggregation of Ion Pairs.

Two-component self-assembly is a promising approach to construct functional nanomaterials. Interaction of a flexible guanidiniocarbonyl pyrrole tetra-cation (1) with naphthalene diimide dicarboxylic acid (NDIDC) in aqueous DMSO leads to the formation of supramolecular networks. First, the carboxylate groups of NDIDC bind to the guanidiniocarbonyl pyrrole cations of 1 in a 1:2 stoichiometry. Further π-π induced aggregation then leads to 3D networks, as established by dynamic light scattering studies (DLS), NMR, fluorescence titration, viscosity measurements, AFM, and TEM microscopy. Due to ion pairing, the resulting aggregates can be switched between the monomers and the aggregates reversibly using external stimuli like protonation or deprotonation. At high concentration, a stable colloidal solution is formed, which shows an extensive Tyndall effect. Increasing the concentrations even further leads to formation of a supramolecular gel.

Supramolecular approach to new inkjet printing inks.

Electronically complementary, low molecular weight polymers that self-assemble through tunable π-π stacking interactions to form extended supramolecular polymer networks have been developed for inkjet printing applications and successfully deposited using three different printing techniques. Sequential overprinting of the complementary components results in supramolecular network formation through complexation of π-electron rich pyrenyl or perylenyl chain-ends in one component with π-electron deficient naphthalene diimide residues in a chain-folding polyimide. The complementary π-π stacked polymer blends generate strongly colored materials as a result of charge-transfer absorption bands in the visible spectrum, potentially negating the need for pigments or dyes in the ink formulation. Indeed, the final color of the deposited material can be tailored by varying the end-groups of the π-electron rich polymer component. Piezoelectric printing techniques were employed in a proof of concept study to allow characterization of the materials deposited, and a thermal inkjet printer adapted with imaging software enabled in situ analysis of the ink drops as they formed and of their physical properties. Finally, continuous inkjet printing allowed greater volumes of material to be deposited, on a variety of different substrate surfaces, and demonstrated the utility and versatility of this novel type of ink for industrial applications.