Construction Of Supramolecular Structures Research Articles

Chitosan-based Maillard products for enzyme immobilization in multilayers structure: Its application in electrochemical sensing

In this work we demonstrate for the first time the advantages of using water-soluble chitosan polycation obtained by Maillard reaction with glucose (G-Chit) or lactose residues for the immobilization of glucose oxidase (GOx) and lactate oxidase by the layer-by-layer adsorption method onto carbon paste electrodes. Besides its solubility in enzyme-compatible media, these polymers have a suitable charge density for electrostatic adsorption and allow adequate charge transfer at the electrode-solution interface. Based on the analysis of the effect of the type of chitosan derivative on the enzymatic response; we built an efficient biosensor based on G-Chit and GOx. The multilayered structure made of three bilayers of G-Chit and GOx showed the best performance; the biosensor exhibits a sensitivity of (12.4 ± 0.3) µA mM−1 cm−2 in a glucose concentration range from 180 µM to 1.75 mM. In addition, the analytical response of this biosensor was tested in milk samples with negligible effects of the matrix. The results confirm the suitability of these chitosan derivatives for the adsorption of enzymes and the construction of supramolecular structures. The favorable environment for the enzymatic activity results in bioelectrodes with fast responses for quantification of glucose even in a complex matrix like milk.

Controlled Construction of Heteroleptic [Pd2 (LA )2 (LB )(LC )]4+ Cages: A Facile Approach for Site-Selective endo-Functionalization of Supramolecular Cavities.

Construction of supramolecular structures with internal functionalities is a promising approach to build enzyme-like cavities. The endo-functionalized [Pd12 L24 ] and [Pd2 L4 ] coordination cages represent the most successful systems in this regard. However, these systems mainly contain one type of endo-moiety. We herein provide a solution for the controlled endo-functionalization of [Pd2 L4 ] cages. Site-selective introduction of the endo-functional group was achieved through the formation of heteroleptic [Pd2 (LA )2 (LB )(LC )] cages. Using two orthogonal steric control elements is the key for the selective formation of the hetero-assemblies. We demonstrated the construction of two hetero-cages with a single internal functional group as well as a hetero-cage with two distinct endohedral functionalities. The endo-functionalized hetero-cages bound sulfonate guests with fast-exchange dynamics. This strategy provides a new solution for the controlled endo-functionalization of supramolecular cavities.

Supramolecular and theoretical investigation of copper(II) complexes containing 2,2′-bipyridine and substituted chalcone ligands: Estimation of non-covalent interactions

Copper complexes of type [Cu(L)(bpy)(NO3)] {1, L = L1; 2, L = L2; L1H= 3-(4-benzyloxyphenyl)-1-(2-hydroxylphenyl)-prop-2-en-1-one, L2H= 1-(2-hydroxyphenyl)-3-(4-chlorophenyl) prop-2-en-1-one, bpy=2,2′-bipyridine} have been synthesized and characterized using elemental analysis, spectroscopic (IR, UV–Vis) and single crystal X-ray diffraction techniques. In both complexes, Cu(II) adopts distorted square pyramidal geometry. The crystal packing of complex 1 displays an infinite 1D supramolecular architecture using C–H⋯O and π-π stacking interactions. The C–H⋯O and π⋯π interactions together with weak C–H⋯Cl interaction facilitate formation of a 2D supramolecular net like structure in complex 2. The comprehensive studies of these interactions have been made using hirshfeld surface, fingerprint plots analyses and energy frameworks. The molecular electrostatic potential (MEP) surface analysis shows the larger values of negatively charged nitrate and larger positive values at aromatic ring in both complexes. It implies that C–H⋯O and π⋯π interactions are dominant. Additionally, the combination of non-covalent interaction (NCI) plot index and QTAIM analysis computational tools are used to explore energetic features of the synthons involving different non-covalent interactions such as C–H⋯O, π⋯π and C–H⋯Cl interactions. Both analyses show that the combined π⋯π and CH⋯π interactions are dominant in the complex 1 for the dimer stabilization and construction of supramolecular structure. Whereas, complex 2 dimerization is prominently due to π⋯π interaction. The complexes 1 and 2 display emissions λmax 524 and 533 nm at λexcit 438 and 440 nm, respectively. It indicates small bathochromic shift in emission of complex 2 to complex 1 due to substituted chalcone ligands.

Nanoparticles as template for porphyrin nanostructure growth

Porphyrins and metalloporphyrins are one of the most widely studied platforms for the construction of supramolecular structures. These compounds have an extended aromatic system that allows [Formula: see text]–[Formula: see text] stacking interactions which, together with hydrogen bonds, electrostatic forces and the formation of inter-metallic complexes arising from peripheral groups, offer a versatile platform to control the self-assembly mechanism. In this work, we present the study of nanostructures formed by self-assembly of the water-soluble porphyrins meso-tetra([Formula: see text]-methyl-4-pyridyl)porphyrin (TMPyP) and meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) in the presence of hard nanotemplates. Different nanoparticles (silica, gold, and polystyrene), concentrations and synthetic procedures were explored. The obtained materials were characterized by SEM and AFM microscopies, UV-vis absorption spectroscopy and dynamic light scattering measurements. A clear modification of the SiO2 NP surface roughness using one-pot synthesis was observed. The results were variable depending on the porphyrin–surface interactions and concentrations used. At lower porphyrin concentrations, a shift of the Soret band was observed, while at higher concentrations, free NS were formed. This reflects a competition between surface and solution directed self-assembly.

Supramolecular Protein Assemblies Based on DNA Templates.

DNA plays an important role in the process of protein assembly. DNA viruses such as the M13 virus are typical examples in which single DNA genomes behave as templates to induce the assembly of multiple major coat protein (PVIII) monomers. Thus, the design of protein assemblies based on DNA templates attracts much interest in the construction of supramolecular structures and materials. With the development of DNA nanotechnology, precise 1D and 3D protein nanostructures have been designed and constructed by using DNA templates through DNA-protein interactions, protein-ligand interactions, and protein-adapter interactions. These DNA-templated protein assemblies show great potential in catalysis, medicine, light-responsive systems, drug delivery, and signal transduction. Herein, we review the progress on DNA-based protein nanostructures that possess sophisticated nanometer-sized structures with programmable shapes and stimuli-responsive parameters, and we present their great potential in the design of biomaterials and biodevices in the future.

Effects of substituents and charge on the RCHO⋯X–Y {X = Cl, Br, I; Y = –CF3, –CF2H, –CFH2, –CN, –CCH, –CCCN; R = –OH, –OCH3, –NH2, –O−} halogen-bonded complexes

Noncovalent interactions involving halogen bonding interactions, one of the emerging interactions due to its directionality, have been a subject of interest for various researchers, owing to its role played in construction of supramolecular structures and crystal engineering. In this article, the RCHO⋯X–Y {X = Cl, Br, I; Y = –CF3, –CF2H, –CFH2, –CN, –CCH, –CCCN; R = –OH, –OCH3, –NH2, –O−} halogen-bonded complexes have been investigated with aid of quantum chemical calculations at MP2/aug-cc-pVDZ(-PP) level. The geometrical, spectroscopic and energetic properties have been analyzed for these complexes with QTAIM, MEP and NBO analyses. For same RCHO molecule, the interaction energies increase in the order of O⋯Cl < O⋯Br < O⋯I and for the same X–Y; the trend is (HO)CHO < (CH3O)CHO < (H2N)CHO. The present article also compares the neutral complexes involving (HO)CHO, (CH3O)CHO and (H2N)CHO carbonyl molecules with those of charged carbonyl species HCOO−. It has been found that strength of the latter complexes is highest among all of the four. The role of substituents in the complex formation has been analyzed on the basis of results obtained from MEP, QTAIM and NBO studies.

Methyl Cinnamate-Derived Fluorescent Rigid Organogels Based on Cooperative π-π Stacking and C═O···π Interactions Instead of H-Bonding and Alkyl Chains.

A new class of rigid low-molecular-mass organic gelators (LMOGs) was synthesized by McMurry and Heck reactions, and their gels and photophysical properties were investigated. The LMOGs lacked alkyl chain and H-bonding units and produced good gelation ability in selected mixed organic solvents facilitated by cooperative π-π stacking and C═O···π interactions. Sensitive gel-sol transformation by molecular aggregation and disaggregation was easily achieved upon heating and cooling. H-H 2D NOESY and X-ray diffraction (XRD) patterns showed the π-π stacking and C═O···π interactions between tiny methyl acrylate groups as "tails". Importantly, this soft interaction model offers a useful tool for the future design and construction of supramolecular structures. At present, the LMOGs reported herein offer a sensitive gel-formation ability and aggregation-induced emission (AIE) property and thus have promising application potentials as functional soft matter in amorphous materials, photoelectric materials, and so on.

Three metal–organic coordination compounds based on 4,6-dipyridyl-2-aminopyrimidine: Important role of hydrogen bonding in supramolecular assemblies

The reactions of divalent metal salts and 4,6-dipyridyl-2-aminopyrimidine ligands gave rise to three metal–organic coordination compounds: [ZnL1(OOCCH 3) 2] ( 1), [Co(L2) 2(OH) 2]·3H 2O ( 2), and [Cu 2(L2) 2(OH) 2(H 2O) 2](NO 3) 2·0.5H 2O ( 3) [L1 = 4,6-bis(2-pyridyl)-2-aminopyrimidine; L2 = 4-(2-pyridyl)-6-(4-pyridyl)-2-aminopyrimidine] and their crystal structures were determined via single-crystal X-ray diffraction. In the three structures, L1 and L2 both exhibit terminal coordination mode. As the ligands contain both hydrogen bonding donors and acceptors, hydrogen bonding interactions play a crucial role in construction of supramolecular structures. In compound 1, the mono-nuclear complexes were connected to dimer structure by hydrogen bondings; in compound 2, dimer units were constructed through intermolecular hydrogen bondings and the crystallographic water molecules link the dimers into a 1-D supramolecular chain; and in compound 3, a complicated 3-D supramolecular architecture was formed via a series of hydrogen bondings. Moreover, the compounds 1– 3 display room-temperature luminescent properties.

超分子ポリマーの構築と機能

Recently, much attention has been focused on construction of supramolecular polymers because of their unique structures and functions. Supramolecular polymers are ubiquitous in nature, especially in biological systems, such as microtubules, flagella, virus, and phages. They have unique structures and functions such as self-replication, self-restoration, transportation, and movements. If such supramolecular systems are available by synthetic methods, we are able to obtain various interesting materials and functional devices. In the first part of this review, construction of nano-structures using cyclodextrins as a cyclic building block is described. Rotaxanes and polyrotaxanes of various kinds are introduced. In the last part, construction of supramolecular structures using biopolymers such as DNA and immunoglobulins are described. In this review, I would like to show some recent advances in this field from the viewpoint of polymer science and synthetic chemistry.

Self-Assembling Calix[4]arene [2]Catenanes. Preorganization, Conformation, Selectivity, and Efficiency

A novel class of preorganized U-shape calix[4]arene clefts, dicationic salts 3a,c,e.2Cl, 3b.2PF(6)(), and 3f.2Br, consisting of one cone calix[4]arene and two bipyridine residues being linked by an aliphatic chain, have been designed and synthesized as precursors for self-assembly of calix[4]arene [2]catenanes by utilizing pi-stacking interactions between the hydroquinone and bipyridinium units. Conformationally flexible 6.2PF(6)() and cone 10.2Cl, whose conformation is fixed by two propyloxy groups on the lower rim, were also prepared in order to explore the effects of conformation and hydrogen bonding of the calix[4]arene moiety on self-assembly. For all reactions, bis-p-phenylene-34-crown ether-10 (11) was employed as the donor component. Alternate cone [2]catenane 13.4Cl is obtained in 8% yield from reaction of ethylene-incorporating 3a.2Cl and 1,4-bis(bromomethyl)benzene (12a). Three cone and one conformationally flexible [2]catenanes were obtained in moderate to good yields from reactions of propylene-incorporating 3b.PF(6)() and 3c.2Cl with 12a, 1,3-bis(bromomethyl)benzene (12b) or 4,4'-(bromomethyl)biphenyl (12c). Both cone and partial cone [2]catenanes were generated in moderate yields from butylene-incorporating 3c.2Cl with four tert-butyl groups on the calix[4]arene moiety and with 12a. In contrast, only cone [2]catenane was obtained from similar tert-butyl-free cleft 3d.2Cl. Cone and conformationally flexible [2]catenanes were obtained in moderate yields, respectively, from the reactions of 3d.2Cl and 3e.2Cl with 12c. No catenanes were isolated from reaction of phenylene-incorporating 3f.2Br or 6.2Cl, whereas reaction of 10.2Cl afforded cone [2]catenane in low yield. It was demonstrated that hydrogen bonding, which may be destroyed after catenation, within the calix[4]arene moiety is crucial for efficient self-assembly of the [2]catenanes. The dynamic (1)H NMR and absorption spectra and luminescent properties of the [2]catenanes were investigated, which reveal that incorporation of calix[4]arene into the tetracationic cyclophane reduces pi-stacking interactions between the donor and acceptor units and catenation has substantial influence on conformational distributions of the calix[4]arene moiety. The results demonstrate the versatility of calix[4]arene derivatives as building blocks in the construction of supramolecular structures.

Construction of Supramolecular Structures via. Hydrogen Bonds. Formation of Two Dimensional Superstructure of DNA Base Molecules through Hydrogen Bonding.

Scanning tunneling microscopic observations at room temperature and 70 K have revealed that the DNA and RNA base molecules which are randomly dispersed on Cu(111) surfaces self-assemble to form two dimensional superstructure through the interaction of hydrogen bonding.

Construction of Supramolecular Structures via. Hydrogen Bonds. Self-organization of Nitroxide Radicals by Hydrogen Bond and the Preparation of LB Film.

There has been increasing research interest in the study of molecular-based magnetism. A rational design of nitroxisides with magnetic cooperativity using the intermolecular magnetic coupling is described. Introducing the hydrogen bonding site into nitroxides is a useful way of controlling magnetic interaction and/or molecular arrangement in crystal. Nitronyl nitroxide with imidazole (Im-NN) and benzimidazole (BIm-NN) were designed and their self-assembled structures and magnetic properties were characterized according to McConnell's theorem. BIm-NN were assembled in a columnar structure with N-H…O-N motif and formed a 1-D ferromagnetic chain due to the overlap of magnetic orbitals. The effect of hydrogen bonding on the molecular packing was also observed with nitronyl nitroxides having hydrophobic chain. Spectroscopic property of nitronyl nitroxides at air-water interface was discussed in terms of their electronic structure.

Construction of Supramolecular Structures via. Hydrogen Bonds. Self-assembly of Complementary Hydrogen Bond-mediated Supermolecules in Aqueous and in Organic Media. Mesoscopic Supramolecular Assemblies.

Self-organization of amphiphilic supermolecules consisted of complementary hydrogen bonds provide supramolecular assemblies of higher hierarchy, which are soluble in water or in organic media (mesoscopic supramolecular assemblies). When ammonium-derivatized cyanuric acids and dialkylmelamines were mixed in water, complementary hydrogen bond-mediated bilayer assembly were spontaneously formed. This “reconstitution” in water is achieved as a result of interplaying hydrophobic interaction and hydrogen bond formation. The hydrogen bond-mediated bilayers displayed unique bilayer characteristics as exemplified by dynamic aggregate separation process, which was observed for ternaly complimentary mixtures. On the other hand, an equimolar mixture of dialkyl-melamine and naphthalenediimide formed stable dispersions in cyclohexanes. Electron microscopy observations indicated the presence of flexible rods with a diameter of ca. 100A, and is most probably composed of circularly hydrogen-bonded units of the two components. In addition, an equimolar mixtures of dialkyl-melamine and alkylated cyanuric acid provided linear hydrogen bond-mediated bilayer structures both in cyclohexanes and in chloroform, in which thermal phase transition characteristics were preserved in organic media.

Construction of supramolecular structures from cyclodextrins, polymers

Cyclodextrins (CDs) have been found to form inclusion complexes with various polymers with high specificity to give stoichiometric compounds in crystalline states. In these complexes, polymer chains were threaded into cyclodextrins and recognized by the host. For example, α-cyclodextrin (α-CD) formed complexes with poly(ethylene glycol) (PEG) of molecular weight higher than 200, although β-CD did not form complexes with PEG of any molecular weight. However, β-CD formed complexes with poly(propylene glycol) (PPG) of various molecular weights with which α-CD did not form complexes. γ-CD formed complexes with poly(methyl vinyl ether) (PMVE), though α-, β-CD did not form complexes with PMVE. α-CD formed complexes with oligoethylene, but only γ-CD formed complexes with polyisobutylene of molecular weight over 500. The structures and properties of the complexes have been studied by spectroscopic methods. Polyrotaxanes in which many CDs are threaded on a single chain were prepared by capping the chain ends with bulky groups.

Self-assembling Tetrathiafulvalene-based Rotaxanes and Catenanes

A general stepwise approach is described for the preparation of tetrathiafulvalene (TTF)-based linear and monoand dimacrocyclic compounds incorporating one or two 1,4-dioxyphenylene, 9,10-dioxyanthrylene, or 1,5- or 2,6-dioxynaphthylene units from readily available starting materials. By utilizing the π–π stacking interactions of the TTF unit with the dipyridinium dication of 1,1′-[1,4-phenylenebis (methylene)] bis-4,4′-bipyridinium bis(hexafluorophosphate), a rotaxane and two [2]catenanes were synthesized starting from the linear and monomacrocyclic compounds, respectively. From the dioxyphenylene-based dimacrocycle, three [3]pseudocatenanes (trans, cis, and a mixture of cis/trans isomers) were obtained with the trans compound as the major product. From the dioxyanthrylene dimacrocycle, only the trans-[3]pseudocatenane was obtained. Catenane products were formed quantitatively from the 1,5-dioxynaphthylene dimacrocycle in a template-directed reaction, affording a trans-[3]pseudo-catenane together with a [4]pseudocatenane (mixture of cis/trans isomers). From the 2,6-dioxynaphthylene dimacrocycle, a cis-[3]pseudocatenane was obtained as the major product and a trans-[3]pseudocatenane as the minor one. For the [3]pseudocatenanes (i.e., both the cis and trans catenanes), in which the TTF units were clamped by the tetracationic macrocycle, isomerizations were completely prevented even in the presence of trifluoroacetic acid. All new rotaxanes and catenanes were characterized by electrospray mass spectrometry, and the cis- and trans- [3]pseudocatenanes were additionally investigated by 1H NMR spectroscopy. The electrochemical and spectral properties of the rotaxane and the catenanes are reported. Catenane formation increases the redox potentials of the TTF unit. The results demonstrate the versatility of TTF as a building block in the construction of supramolecular structures.

A model of molecular electronics based on the concept of conjugated lonic–hydrogen bond systems

AbstractA new model of lmolecular electronics is proposed as an alternative to the ‘soliton logic’ developed by Carter. The model is based on the principles of continuity of conjugated ionic–hydrogen bond systems (CIHBSs) in the construction of supramolecular structures and conjugation through the hydrogen bond in energy transduction. It is presumed that these principles are realized in biostructures. The Concept implies a symmetrica oligomeric organisation of supramolecular structures and an oscillatory mode of their functioning. The basic architecture and basic elements have been identified. The basic architecture is determined by periodic CIHBSs. The latter have been analysed in proteins, nucleoproteids and biomembranes. The basic elements contain groups capable of building in CIHBSs. Charge generators, valves and other basic elements contain groups capable of building in CIHBSs. Charge generators, valves and other basic elements have been distinguished among biomolecules. Oligomeric enzymes have been suggested as functional prototypes of molecular processors–multivibrators where CIHBSs form Feedback loops and Provide energy recuperation. Technologcal aspects of designing molecular electronic devices on CIHBS principles have been considered. The most challenging and complicated problem is the creation of supramolecular structures with properties which can be specified in advance. Synthesis of membrane two‐dimensional active media capable of storing and processing information in the mode of parallel fluxes is suggested as the most promising route for the fabrication of biochips.

Formation of Interwoven 2‐D Networks by the Spontaneous Strict Self‐Assembly of [{M(CO)3(μ3‐OH)}4] (M  Mn, Re) and Complementary Angular Spacer Molecules

The construction of supramolecular structures by simple cocrystallization of compounds whose molecular building blocks are complementary is amazingly easy. Td-symmetric molecules that can function as Hbond donors, for instance [{M(CO)3(μ3OH)}4] (M  MnI, ReI) (shown on the right), and bi- or multifunctional Hbond acceptors such as 1,3-diaminopropane and hexamethylenetetramine form two-dimensional “chickenwire” networks.