Influence of gelator structures on formation and stability of supramolecular hydrogels

A supramolecular hydrogel(defined as G1) formed from 1,2,4,5-benzene tetracarboxylic acid (BTCA) and 2-amino-3- hydroxypyridine possessed higher T_(gel) than that of another hydrogel(defined as G2) formed from BTCA and 3-hydroxypyridine. Based on the analysis of their xerogels by ~1H NMR,IR and XRD,the higher stability of G1 was attributed to the formation of stronger hydrogen binding enhanced by the ortho amino group of 2-amino-3-hydroxypyridine.     

Assembling and releasing performance of supramolecular hydrogels formed from simple drug molecule as the hydrogelator

A simple drug compound, 4-oxo-4-（2-pyridinylamino） butanoic acid （defined as AP）, was able to gel water at 4 wt% concentration under various conditions. In the superstructure, AP molecules assembled into fibrous aggregates driving by hydrogen bonds and π-π stacking interaction. The gels with different backbone structures released drug molecules in different speeds.     

基于偏苯三甲酸与对羟基吡啶复合物的超分子水凝胶

基于偏苯三甲酸和对羟基吡啶合成了一种具有支化结构的凝胶因子,采用氢核磁、红外光谱及元素分析确认其结构.该凝胶因子熔体在冷却时可拉出数厘米的长丝,表明分子间形成了强相互作用.将凝胶因子的水溶液分别在25℃和0℃下自然冷却、以及在25℃的超声作用下冷却,凝胶因子自组装成纤维状网络结构并使水凝胶化,纤维网络的密度及凝胶的稳定性均按上述凝胶形成条件顺序增加.通过干凝胶能谱面扫描分析发现氮元素主要处于纤维内部,表明两亲性凝胶因子对分子自组装的影响.通过分析邻苯二甲酸与对羟基吡啶复合物、偏苯三甲酸的单晶结构表明,凝胶因子基于多种氢键识别作用组装成纤维结构.干凝胶的粉末X射线衍射分析表明在凝胶化过程中凝胶因子沿着特定方向进行组装.     

The selective and enhanced adsorptive behaviors of supramolecular recrystallized 1,3,5-benzenetricarboxylic acid assembled nano-bacterial cellulose

The effluent discharge produced in the textile printing and dyeing, leather and other fields, will cause the irreversible environmental pollution and extremely threatening safety of living organisms. The appropriate and efficient disposal method of dyestuff originated wastewater has been widely concerned in the past decades. In this study, the recrystallization of 1,3,5-benzene tricarboxylic acid (RCTMA) was put forward via a hydrothermal method to form the supramolecular RCTMA-based hexamer and thereafter assembled into the porous nano-bacterial cellulose (NBC) to construct the RCTMA@NBC composite. The morphology and surface properties of RCTMA@NBC were examined by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. This RCTMA@NBC was employed to adsorb methylene blue (MB) adjusting the pH, temperature, and dosage of adsorbent. The result showed the maximal absorption capacity of RCTMA@NBC appeared under pH = 7.1 and higher temperature will hinder the adsorption of dyes. Moreover, the adsorption isotherms and kinetics were evaluated which was more confirmed to Langmuir model and quasi-second-order kinetic equation, and the simulated maximum adsorption capacities of MB was 1162.12 mg/g. Moreover, cationic golden XGL and anionic brilliant crocein were selected to further verify the distinct adsorptive behavior. The excellent affinity towards cationic dyes proved the easy combination was based on the chemical force originated from mutual attraction between opposite charges, π–π interactions, and H-bonding, whereas the poor attraction for brilliant crocein was due to the electrostatic repulsion between sulfonic and carboxyl groups. The synthesized RCTMA@NBC possesses higher efficiency and selective adsorption, which exhibits the promising potential in the field of precise treatment of organic dye wastewater.     

基于氢键作用由低分子量凝胶因子形成的超分子水凝胶

利用对羟基吡啶及均苯四甲酸合成的超分子单体, 基于分子间氢键作用, 在水中成功地制备出了具有温度响应性的超分子凝胶, 研究了制备条件对凝胶结构的影响.     

Multiple hydrogen-bond-induced supramolecular nanostructure from a pincer-like molecule and a [60]fullerene derivative

A new supramolecular self-assembled system between a perylene bisimide bearing diaminopyridine-substituted isophthalamide groups (PP) and a [60]fullerene containing barbituric acid moiety (C₆₀bar) through a complementary six-point hydrogen-bonding interaction was constructed. The formation of hydrogen bonding was confirmed by ¹H NMR spectra studies in CDCl₃. Fluorescence quenching experiments indicated that the fluorescence of PP was greatly quenched by the hydrogen-bonded C₆₀bar (K_sv=2.71×10⁴ M⁻¹). A steady and rapid cathodic 0.15 μA cm⁻² photocurrent response of the PP/C₆₀bar film deposited onto an ITO electrode was produced under the irradiation of 20 mW cm⁻² white light, indicating the presence of photo-induced electron transfer between PP and C₆₀bar. TEM images showed that spherical particles were fabricated by the self-assembly of PP and C₆₀bar through hydrogen-bonding interaction.     

Effect of hydrogen bonding and hydrophobic interaction on the formation of supramolecular hydrogels formed by L-phenylalanine derivative hydrogelator

A new hydrogelator,pyridinium bromide salt of N-6-bromohexanoyl-L-phenylamino octadecane,was synthesized.Supramo- lecular hydrogels can be formed through the self-assembly of this hydrogelator in water.In this work,D_2O was used instead of H_2O as solvent for FT-IR measurement due to the fact that it is impossible to obtain useful FT-IR information on the hydrogen bonding in water.The investigation of FT-IR and steady-state fluorescence indicated that the driving forces for the self-assembly were mainly hydrogen bonding and hydrophobic interaction.Based on the data of XRD and molecular modeling,the possible mechanism of the formation of hydrogelator aggregates was proposed.     

Hydrothermal syntheses and characterizations of two new hydrogen bond-supported supramolecular compounds based on polyoxometalates

Two new polyoxometalates [HN(C₂H₅)₃]₃[PMo₁₂O₄₀] (1) and [NH₂(C₂H₄NH₃)₂]₂[Mo₅P₂O₂₃] (2) have been hydrothermally synthesized and characterized by IR, UV-Vis, XPS spectra, TG analyses, and single crystal X-ray diffraction. Crystal data for 1: monoclinic, space group C2/c, a = 24.651(5) Å, b = 10.822(2) Å, c = 22.413(5) Å, β = 120.37(3)°, and V = 5158.7(18) ų; for 2: triclinic, space group P-1, a = 9.821(2) Å, b = 9.948(2) Å, c = 14.687(3) Å, α = 95.490(3)°, β = 98.870(3)°, γ = 95.710(3)°, and V = 1401.7(5) ų. The crystal structure analyses reveal complex hydrogen bonds in both 1 and 2 in 3-D supramolecular arrays constructed from different polyoxoanions and organic ligands.     

High impact resistance epoxy resins by incorporation of quadruply hydrogen bonded supramolecular polymers

A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-(propylene glycol) bis(2-aminopropyl) ether chains and 2-ureido-4[1H]-pyrimidinone moieties (UPy) self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.     

Synthesis,structure and luminescent properties of Cd(II) and Zn(II) complexes constructed from 3,5-dimethyl-2, 6-pyrazinedicarboxylic acid

[Cd₂(phen)₂(DPZDA)₂(H₂O)₂] · 8H₂O (1) and [Zn(phen)(DPZDA)(H₂O)] · 2H₂O (2) have been synthesized by reaction of Cd(NO₃)₂/Zn(NO₃)₂ with phen and DPZDA (where phen = 1,10-phenanthroline, H₂DPZDA = 3,5-dimethyl-2,6-pyrazinedicarboxylic acid) in aqueous ethanol solution. Elemental analysis, IR spectra, thermal analyses and X-ray single crystal diffraction were carried out to determine the composition and crystal structure of 1 and 2. In 1, a 2D supramolecular network containing a novel metal-water decamer were formed by hydrogen bonds. In 2, a 2D supramolecular structure was constructed from hydrogen bonds and π·· · π interactions. Moreover, 1 and 2 displayed photoluminescent properties in the blue range at room temperature.     

Two new hydrogen bond-supported supramolecular compounds assembly from arsenic vanadates and [M(H2O)6] cations (MCo, Ni)

Two new supramolecular compounds based on arsenic vanadates formulated as [H₂As₆V₁₅O₄₂(H₂O)][Co(H₂O)₆]₂·2H₂O (1) and [H₂As₆V₁₅O₄₂(H₂O)][Ni(H₂O)₆]₂·2H₂O (2) have been prepared by reacting V₂O₅, H₂C₂O₄·2H₂O, As₂O₃,·H₂SO₄, CoCl₂·6H₂O (NiSO₄·6H₂O) and enMe (enMe=1,2-diaminopropane) under mild hydrothermal conditions and characterized by elemental analyses, IR, ESR, XPS and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compounds 1 and 2 are isostructural and exhibit novel 2-D supramolecular layer structures constructed from arsenic-vanadium clusters and two different types of secondary building units (SBUs), respectively, the different SBUs are formed by joint of two adjacent [Co(H₂O)₆]²⁺ cations in compounds 1 and [Ni(H₂O)₆]²⁺ cations in 2, respectively.     

A new polar supramolecular 3D framework [Zn(pyz)(H2O)4]pht

A new Zn(II) complex, [Zn(pyz)(H₂O)₄]pht (1) (pyz=pyrazine; pht=1,2-benzenedicarboxylate) has been hydrothermally synthesized and characterized. Complex 1 features a novel polar 3D framework with a 1D polycationic chain , between which pht²⁻ dianions are encapsulated via the supramolecular interaction. Its powder SHG is of about three times as large as that of KH₂PO₄.     

Microscopic and macroscopic anisotropy in supramolecular hydrogels of histidine-based surfactants

The synthesis of novel histidine-based surfactants and their self-assembling properties into anisotropic microscopic and macroscopic spaces are reported. Below pH 8, surfactant molecules self-assemble into micelles whereas hydrogelation occurs above pH 8 even at very low concentrations (0.3%w/v). Structure, size, and morphology of the fiber-like lamellar aggregates were determined by SAXS and WAXS measurements, polarized optical microscopy, transmission and scanning electron microscopy, and linear and circular dichroism.     

Chiral supramolecular metal-organic architectures from dinuclear copper complexes

Two new chiral dinuclear Cu(II) complexes [Cu₂(μ-Cl)₂(HL¹)₂] · C₂H₅OH (1) and [Cu₂(μ-Cl)₂(HL²)₂] · CH₃OH (2), have been synthesized and structurally characterized, where the chiral ligands H₂L¹ and H₂L² are derived from the chiral amino alcohols (S)-(−)-2-amino-3-phenyl-1-propanol and (S)-(+)-2-phenylglycinol. Single-crystal X-ray crystallographic analyses revealed that in these complexes, the dominant hydrogen bonding property of metal bound chloride anion directs the self assembly of complex molecules through C–H···Cl hydrogen bonding interactions leading to the formation of intriguing hydrogen bonded metallo-supramolecular architectures in their respective crystal lattices. The supramolecular systems described here belong to the rare class of metal-organic architectures that are formed as a result of metal directed hydrogen bonding interactions among chiral complex molecules. Complexes 1 and 2 are further characterized by IR, ESR, UV–Vis and CD spectroscopy.     

Gear-like array of （H2O）12 as building blocks one-dimensional supramolecular assembly

The preparation and crystal structure of complex Co（Hsae）2·2H2O （1, H2sae = N-salicylidene-2-iminoethanol） are reported. X- ray analysis revealed that every six Co（Hsae）2 forms a cyclic chip and every 12 water forms a novel gear-like cluster. Acting as building blocks, the gear-like water cluster and complex chip are connected in A-B fashion and extend into one-dimensional supramolecular chain. Hydrogen bond is the primary bridging force in the formation of supramolecular framework.     

Synthesis, structure and non-linear optical property of a copper(II) thiocyanate three-dimensional supramolecular compound

A novel copper(II) thiocyanate complex [Cu(im)₂(NCS)₂] 1 (im=imidazole) has been prepared and characterized by spectroscopic analysis and crystallographic method. This supramolecular compound exhibits a three-dimensional solid state structure constituted by N–HS hydrogen bonds and π–π stacking interactions. The compound in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with absorption coefficient and refractive index ₂=1.18×10⁻¹¹ mw⁻¹, n₂=−9.00×10⁻¹⁶ m²w⁻¹, respectively, and third-order NLO susceptibility χ⁽³⁾ of 7.00×10⁻¹⁰ esu.     

基于均苯三甲酸与对羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料, 采用简便方法合成了一种新的凝胶因子, 并采用1H NMR、IR和元素分析确认其结构. 红外光谱中2849和1894 cm－1处出峰证明羧基与吡啶基间形成了氢键. 在凝胶化过程中, 凝胶因子可自组装形成纤维状网络结构. 随着凝胶因子浓度的增加, 纤维搭接逐渐致密, 凝胶网络密度逐渐增大, 可冻结水含量逐渐增加. 因此, 通过改变凝胶因子浓度可有效控制凝胶的结构及性能. 该凝胶因子在较低浓度下形成的超分子水凝胶在100 ℃下也能够稳定存在.     

Two new hydrogen bond-supported supramolecular compounds assembly from polyoxovanadate and organoamines

Two novel organic-inorganic hybrid compounds based on organoamines and polyoxovanadates formulated as (H₂dien)₄[H₁₀V₁₈O₄₂(PO₄)](PO₄)·2H₂O (1) (dien=diethylenetriamine) and (Him)₈[HV₁₈O₄₂(PO₄)] (2) (im=imidazole) have been prepared under hydrothermal conditions by using different starting materials, and characterized by elemental analyses, IR, ESR, XPS, TGA and single-crystal X-ray diffraction analyses. Crystal data for compound 1: C₁₆H₇₄N₁₂O₅₂V₁₈P₂, Monoclinic, space group C2/c, a=23.9593(4) Å, b=13.0098(2) Å, c=20.1703(4) Å, β=105.566(3)°, V=6056.6(19) Å³, Z=4; for compound 2, C₂₄H₄₁N₁₆O₄₆V₁₈P, Tetragonal, space group I4/mmm, a=13.5154(8) Å, b=13.5154(8) Å, c=19.1136 Å, β=90°, V=3491.4(3) Å³, Z=2. Compound 1 consists of protonated diens together with polyoxovanadates [H₁₀V₁₈O₄₂(PO₄)]⁵⁻. Compound 2 is composed of protonated ims and polyoxovanadates [HV₁₈O₄₂(PO₄)]⁸⁻. There are hydrogen-bonding interactions between polyoxovanadates and different organoamines in 1 and 2. Polyoxovanadates are linked through H₂dien into a three-dimensional network via hydrogen bonds in 1, while polyoxovanadates are linked by Him into a two-dimensional layer network via hydrogen bonds in 2. The crystal packing patterns of the two compounds reveal various supramolecular frameworks.     

Gel formation and photopolymerization during supramolecular self-assemblies of α-CDs with LA-PEG-LA copolymer end-capped with methacryloyl groups

A novel gelation occurs in water during supramolecular self-assemblies of α-cyclodextrins being threaded onto amphiphilic LA-PEG-LA copolymer end-capped with methacryloyl groups. The rheologic studies show that the gels are thixotropic and reversible. While exposed to UV irradiation with a photoinitiator added in advance, they can be photopolymerized in situ to give rise to chemically cross-linked biodegradable hydrogels with the markedly improved mechanical strength. The gels formed prior to and after UV irradiation are characterized using FTIR, ¹H NMR, WAXD and TGA techniques. The swelling ratio and in vitro degradation of the photocured hydrogels are also investigated. It appears that both physical and chemical gels have the potential to be used as injectable biomaterials.     

基于均苯三甲酸与4-羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料,采用简便方法合成了一种新的凝胶因子,并采用1H NMR、IR和元素分析确认其结构.红外光谱中2849和1894cm-1处出峰证明羧基与吡啶基间形成了氢键.在凝胶化过程中,凝胶因子可自组装形成纤维状网络结构.随着凝胶因子浓度的增加,纤维搭接逐渐致密,凝胶网络密度逐渐增大,可冻结水含量逐渐增加.因此,通过改变凝胶因子浓度可有效控制凝胶的结构及性能.该凝胶因子在较低浓度下形成的超分子水凝胶在100℃下也能够稳定存在.