A New Three-dimensional Supramolecular Polymer Built from Non-covalent Bonding Interactions

A new complex, [Ni2（L）4（H2O）8]（1, L1 = 4-（1H-imidazol-4-yl）benzoic acid）, has been hydrothermally prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and PXRD. Complex 1 crystallizes in monoclinic, space group P21/c with α = 22.281（2）, b = 7.3959（7）, c = 24.978（3） ？, β = 90.876（10）, V = 4115.6（7） ？3, Z = 8, C20H22N4O8Ni, Mr = 505.13, Dc = 1.630 g/cm3, μ = 1.001 mm-1, S = 1.080, F（000） = 2096, the final R = 0.452 and wR = 0.1152 for 9380 observed reflections （I 〉 2σ（I））. The result of X-ray diffraction analysis revealed three different kinds of Ni（II） centre mononuclear molecules in the asymmetric unit. The independent mononuclear units are bridged to form a three-dimensional supramolecular polymer by extensive hydrogen bonds and C–H… non-covalent bonding interactions.

Factors resisting protein adsorption on hydrophilic/hydrophobic self-assembled monolayers terminated with hydrophilic hydroxyl groups

The hydroxyl-terminated self-assembled monolayer(OH-SAM),as a surface resistant to protein adsorption,exhibits substantial potential in applications such as ship navigation and medical implants,and the appropriate strategies for designing anti-fouling surfaces are crucial.Here,we employ molecular dynamics simulations and alchemical free energy calculations to systematically analyze the factors influencing resistance to protein adsorption on the SAMs terminated with single or double OH groups at three packing densities(∑=2.0 nm^(-2),4.5 nm^(-2),and 6.5 nm^(-2)),respectively.For the first time,we observed that the compactness and order of interfacial water enhance its physical barrier effect,subsequently enhancing the resistance of SAM to protein adsorption.Notably,the spatial hindrance effect of SAM leads to the embedding of protein into SAM,resulting in a lack of resistance of SAM towards protein.Furthermore,the number of hydroxyl groups per unit area of double OH-terminated SAM at ∑=6.5 nm^(-2) is approximately 2 to 3 times that of single OH-terminated SAM at ∑=6.5 nm^(-2) and 4.5 nm^(-2),consequently yielding a weaker resistance of double OH-terminated SAM towards protein.Meanwhile,due to the structure of SAM itself,i.e.,the formation of a nearly perfect ice-like hydrogen bond structure,the SAM exhibits the weakest resistance towards protein.This study will complement and improve the mechanism of OH-SAM resistance to protein adsorption,especially the traditional barrier effect of interfacial water.

Tailoring the Self-assembly of Melamine on Au（111） via Doping with Cu Atoms

The doping effect of Cu on the self-assembly film of melamine on an Au（111） surface has been investigated with scanning tunneling microscopy （STM）. The evaporated Cu adatoms occupy the positions underneath the amino groups and change the hydrogen bonding pat- tern between the melamine molecules. Accordingly, the self-assembly structure has changed stepwise from a well-defined honeycomb into a track-like and then a triangular structure depending on the amount of Cu adatoms. The interaction between Cu adatom and melamine is moderate thus the Cu adatoms can be released upon mild heating to around 100 ℃. These findings are different from previous observations of either the coordination assembly or the physically trapped metal adatoms.

Recent progress in polymerization-induced self-assembly:From the perspective of driving forces

Polymerization-induced self-assembly(PISA)enables the simultaneous growth and self-assembly of block copolymers in one pot and therefore has developed into a high-efficiency platform for the preparation of polymer assemblies with high concentration and excellent reproducibility.During the past decade,the driving force of PISA has extended from hydrophobic interactions to other supramolecular interactions,which has greatly innovated the design of PISA,enlarged the monomer/solvent toolkit,and endowed the polymer assemblies with intrinsic dynamicity and responsiveness.To unravel the important role of driving forces in the formation of polymeric assemblies,this review summarized the recent development of PISA from the perspective of driving forces.Motivated by this goal,here we give a brief overview of the basic principles of PISA and systematically discuss the various driving forces in the PISA system,including hydrophobic interactions,hydrogen bonding,electrostatic interactions,andπ-πinteractions.Furthermore,PISA systems that are driven and regulated by crystallization or liquid crystalline ordering were also highlighted.

Light-fueled dissipative self-assembly at molecular and macro-scale enabled by a visible-light-responsive transient hetero-complementary quadruple hydrogen bond

The development of out-of-equilibrium self-assembly systems using light as input fuel is highly desirable and promising for the fabrication of smart supramolecular materials. Herein, we report the construction of new artificial light-fueled dissipative molecular and macroscopic self-assembly systems based on a visible-light-responsive transient quadruple H-bonding array, which consists of an azobenzene-modified ureidopyrimidinone(UPy) module(Azo-O-UPy) and a nonphotoactive diamidonaphthyridine(DAN) derived competitive binder(Napy-1). The visible light(410 nm) irradiation can induce the E to Z isomerization of the azobenzene unit of E-Azo-O-UPy to produce Z-Azo-O-UPy with an opened UPy binding site, which can complex with Napy-1 to form a quadruply H-bonded heterodimer. The heterodimer is metastable and can be quickly disassembled in dark, owing to the fast thermal relaxation of Z-Azo-O-UPy to E-Azo-O-UPy. While introducing such transient quadruple H-bonding interaction into a linear polymer system or a polymeric gel system, light-fueled out-of-equilibrium polymeric assembly both at molecular and macro-scale can be achieved.

Hydrogen-bonding-driven self-assembly nonporous adaptive crystals for the separation of benzene from BTX and cyclohexane

Benzene is a volatile organic compound that can seriously harm human health,while it can serve as a precursor to produce chemicals of more complex structures in chemical industry.Capturing benzene using adsorbents is of great importance for human health,when the separation of hydrocarbons including benzene from crude oil was referred to as one of the“seven chemical separations to change the world”.In this work,we reported the efficient and selective separation of benzene from BTX and cyclohexane by hydrogen bonding self-assembly nonporous adaptive crystals AdaOH for the first time under mild and user-friendly conditions.Separation of benzene and cyclohexane(v/v=1:1)can be achieved by AdaOH with a purity of benzene up to 96.8%.Separation of BTX(v/v;benzene:toluene:o-xylene:m-xylene:pxylene=1:1:1:1:1)can be achieved by AdaOH with a purity of benzene increased from 20%to 82.9%.Our results suggest that separation of benzene using the activated AdaOH as a non-porous adaptive crystal for selectively and efficiently capturing benzene can solve the challenge in separation of benzene from other chemicals such as cyclohexane in chemical industry,and can be helpful for removal of benzene that is released from the vehicles to air.The advantages of commercially availability,easy preparation,high separation efficiency and selectivity for benzene might endow this material with enormous potential for practical uses in areas like petrochemical industry.

Chain-Length-Dependent Hydrogen-Bonded Self-Assembly of Terminally Functionalized Discrete Polyketones

Here,we report the synthesis and the chain-lengthdependent self-assembling behaviors of discrete di-,tetra-,and hexaketones terminally functionalized with hydrogen-bonding carboxyl(C1,C2,and C3)and 3-acylaminopyridine groups(P1,P2,and P3).These polyketones were prepared by the coupling reactions of silylated analogues of 3,3-dimethylpentane-2,4-dione and t-butyl 2,2-dimethyl-3-oxobutanoate and the subsequent hydrolysis or amidation with 3-aminopyridine.Single-crystal Xray diffraction analysis revealed that C1 and C2 form helical assemblies in which the components are connected by the dimerization of terminal carboxyl groups,whereas the longer C3 showed infinite hydrogen-bonded chains mediated by 1,4-dioxane used as a crystallization solvent.Pyridine-terminated P1 exhibited a three-dimensional hydrogen-bonded network owing to multiple NH…N(pyridine)hydrogen bonds in the solid state.P2 generated a double-helix-like fiber structure in the crystalline state.Among the pyridine-terminated polyketones P1−P3,only P2 showed gelation behavior in chloroform(100 mM concentration)at 25℃.The scanning electron microscopy measurement of xerogel P2 revealed the formation of rod-like structures with a thickness of approximately 0.5−3.5μm.These results demonstrate that the precise control of the polyketone chain length can significantly alter hydrogen-bonded self-assembly in the solid state and in solution even with the same terminal structures.

Small changes in the length of diselenide bond-containing linkages exert great influences on the antitumor activity of docetaxel homodimeric prodrug nanoassemblies

Homodimeric prodrug-based self-assembled nanoparticles,with carrier-free structure and ultrahigh drug loading,is drawing more and more attentions.Homodimeric prodrugs are composed of two drug molecules and a pivotal linkage.The influence of the linkages on the self-assembly,in vivo fate and antitumor activity of homodimeric prodrugs is the focus of research.Herein,three docetaxel(DTX)homodimeric prodrugs are developed using different lengths of diselenide bond-containing linkages.Interestingly,compared with the other two linkages,the longest diselenide bond-containing linkage could facilitate the self-delivery of DTX prodrugs,thus improving the stability,circulation time and tumor targeting of prodrug nanoassemblies.Besides,the extension of linkages reduces the redox-triggered drug release and cytotoxicity of prodrug nanoassemblies in tumor cells.Although the longest diselenide bond-containing prodrug nanoassemblies possessed the lowest cytotoxicity to 4T1 cells,their stable nanostructure maintained intact during circulation and achieve the maximum accumulation of DTX in tumor cells,which finally“turned the table”.Our study illustrates the crucial role of linkages in homodimeric prodrugs,and gives valuable proposal for the development of advanced nano-DDS for cancer treatment.

Facile synthesis and characterization of novel thermo-chromism cholesteryl-containing hydrogen-bonded liquid crystals

Two series of novel cholesteryl-containing H-bonded liquid crystals were prepared through facile self-assembly between cholesteryl isonicotinate （proton acceptor） exhibiting a monotropic cholesteric phase, and the 4-alkoxy-benzoic acid or 4-alkoxy cinnamic acid （proton donor）. It was found that the increase of the conjugate length as well as the terminal length can contribute to enhance the interaction of molecules and thus significantly influenced the thermal behaviors of H-bonded LCs. The cholesteric reflection spectra of the induced mesogenic complexes were located in the visible region with the color tuneable thermo-sensitivity, which could be used for display application.

Investigating the crucial roles of aliphatic tails in disulfide bond-linked docetaxel prodrug nanoassemblies

Disulfide bond-bridging strategy has been extensively utilized to construct tumor specificity-responsive aliphatic prodrug nanoparticles(PNPs) for precise cancer therapy. Yet, there is no research shedding light on the impacts of the saturation and cis-trans configuration of aliphatic tails on the self-assembly capacity of disulfide bond-linked prodrugs and the in vivo delivery fate of PNPs. Herein, five disulfide bond-linked docetaxelfatty acid prodrugs are designed and synthesized by using stearic acid, elaidic acid, oleic acid, linoleic acid and linolenic acid as the aliphatic tails, respectively. Interestingly, the cistrans configuration of aliphatic tails significantly influences the self-assembly features of prodrugs, and elaidic acid-linked prodrug with a trans double bond show poor self-assembly capacity. Although the aliphatic tails have almost no effect on the redox-sensitive drug release and cytotoxicity, different aliphatic tails significantly influence the chemical stability of prodrugs and the colloidal stability of PNPs, thus affecting the in vivo pharmacokinetics, biodistribution and antitumor efficacy of PNPs. Our findings illustrate how aliphatic tails affect the assembly characteristic of disulfide bond-linked aliphatic prodrugs and the in vivo delivery fate of PNPs, and thus provide theoretical basis for future development of disulfide bond-bridged aliphatic prodrugs.

Supramolecular Sheet Co(Ⅱ) Complex Assembled by Hydrogen Bond

The title complex, [ [ Co （Py） 2 （H20） 2 （ NO3 ）2 ] ] n （ 1 ） was synthesized by liquid/liquid diffusion method at room temperature. The complex crystallizes in monoclinic, space group P2 （1）/C, with a = 0.8775（6）nm, b=1.171 5（8）nm, c=0.7518（5）nm, V=0.739 3（9）nm3, C10H14CoN4O8, Mr= 377.18, Dc=1.694g/cm^3, μ=1.210mm^-1, F（000）=386, Z=2, the final R=0.0229 and wR= 0.066 1 for 3 137 observed reflections （I〉2σ（I））. In the structure of 1, the center atom of cobalt revealed a centrosymmetric, six-coordinate structure, with two Py ligands, two monodentate nitrate groups and two water molecules. It is notable that a series of hydrogen bonds （O-H…O） formed two kinds of rings exist in the structure, which linked neighboring six-coordinate polymer into a two-dimensional H-bonding network, and then assembled into a three-dimensional supramolecular architecture through electrostatic and hydrophobic interaction. In the structure, supramolecular sheet was observed, which contains alte .rnative organic and inorganic layers.

Self-assembly behavior of disaccharide-containing supra-amphiphiles

In this paper,supra-amphiphilic compounds containing disaccharides and azobenzene ends have been constructed via dynamic covalent bond.It was found that the slight structural difference of the disaccharides made significant difference in the self-assembled morphologies.Namely,three kinds of azodisaccharide supra-amphiphiles were found to assemble into different morphologies,with the only difference in chemical structure from the disaccharides.More importantly,the structural difference between the disaccharides,including lactoside,maltoside and cellobioside was trivial.Molecular simulation revealed the packing of molecules was due to the different contribution from hydrogen bonds.The above results clearly indicated the contribution of saccharide packing,especially the related hydrogen bonding,to the final morphology of the assembled structures.

Supramolecular polymers fabricated by orthogonal self-assembly based on multiple hydrogen bonding and macrocyclic host–guest interactions

Supramolecular polymers constructed by orthogonal self-assembly based on multiple hydrogen bonding and macrocyclic host-guest interactions have received increasing attention due to their elegant structures,outstanding properties,and potential applications.Hydrogen bonding endows these supramolecular polymers with good adaptability and reversibility,while macrocyclic host-guest interactions give them good selectivity and versatile stimuli-responsiveness.Therefore,functional supramolecular polymers fabricated by these two highly specific,noninterfering interactions in an orthogonal way have shown wide applications in the fields of molecular machines,electronics,soft materials,etc.In this review,we discuss the recent advances of functional supramolecular polymers fabricated by orthogonal self-assembly based on multiple hydroge n bonding and host-guest interactions.In particular,we focus on crown ether-and pillar[n]arene-based supramolecular polymers due to their compatibility with multiple hydrogen bonds in organic solution.The fabrication strategies,interesting properties,and potential applications of these advanced supramolecular materials are mainly concerned.

ESI-MS study on non-covalent bond complex of rhFKBP12 and new neurogrowth promoter

An ESI-MS method for studying the non-covalent bond complex of rhFKBP12 with its nonimmunosuppressive ligands was developed. The method was used to screen out three com-pounds capable of binding to rhFKBP12 non-covalently from 52 compounds. By competing binding experiment, the binding site and the relative binding strength of these three compounds 000107, 000308 and A2B12 with rhFKBP12 were measured. All of them have the same binding site as FK506 does. X-ray crystalline diffraction experiment of non-covalent bond complex of 000107, 000308 with rhFKBP12 by Tsinghua University showed the same results. Among them 000308 has good effect on stimulating neurite to grow in chicken sensory neuronal cultures.

Self-assembly of Pyrene-modified Rhomboidal Metalloden- drimers via Directional Metal-ligand Bonding Approach

The design and self-assembly of pyrene-modified rhomboidal metallodendrimers R1--R6 via directional metal-ligand bonding approach is described. By employing pyrene-containing 120° di-Pt（II） acceptor and appropri- ate 60° dendritic dipyridyl donors, a variety of [G-1]--[G-3] pyrene-modified rhomboidal metallodendrimers with well-defined shape and size were prepared under mild conditions in high yields. The supramolecular dendrimers were characterized with multinuclear NMR （1H and 31p） and mass spectrometry （CSI-TOF-MS）. lsotopically re- solved mass spectrometry data support the existence of the pyrene-modified dendrimers with rhomboidal cavities, and NMR data were consistent with the formation of all ensembles. The shape and size of all rhomboidal den- drimers were investigated with the PM6 semiempirical molecular orbital method. Their primary photochemical properties were studied as well.

Hydrogen Bonded Supramolecular Polymers in Both Apolar and Aqueous Media： Self-Assembly and Reversible Conversion of Vesicles and Gels

In a preliminary letter （Tetrahedron Lett. 2010, 51, 188）, we reported two new hydrazide-based quadruple hydrogen-bonding motifs, this is, two monopodal （la and lb） and five dipodal （2a, 2b and 3a--3c） aromatic hydrazide derivatives, and the formation of supramolecular polymers and vesicles from the dipodal motifs in hydrocarbons. In this paper, we present a full picture on the properties of these hydrogen-bonding motifs with an emphasis on their self-assembling behaviors in aqueous media. SEM, AFM, TEM and fluorescent micrographs indicate that all the dipodal compounds also form vesicles in polar methanol and water-methanol （up to 50% of water） mixtures. Control experiments show that lb does not form vesicles in same media. Addition of lb to the solution of the dipodal compounds inhibits the latter＇s capacity of forming vesicles. At high concentrations, 3b and 3c also gelate discrete solvents, including hydrocarbons, esters, methanol, and methanol-water mixture. Concentration-dependent SEM investigations reveal that the vesicles of 3b and 3c fuse to form gels and the gel of 3c can de-aggregate to form the vesicles reversibly.

Solid state self-assembly of triptycene-based catechol derivatives by multiple O-H…O hydrogen bonds

Single crystals of two triptycene-based catechol derivatives 1 and 2 were obtained,and their X-ray crystal structural studies showed that the two tecton molecules had different conformations in the solid state,and they could self-assemble into interesting 3D networks with solvent molecules included inside, in which multiple O-H…O hydrogen bonds played important roles.

Supramolecular Self-assembly Behaviors of Asymmetric Diblock Copolymer Blends with Hydrogen Bonding Interactions between Shorter Blocks Modelled by Yukawa Potentials

We employed the extended self-consistent field theory to investigate the supramolecular self-assembly behaviors of asymmetric diblock copolymer blends(AB/B’C)with hydrogen bonding interactions between shorter B and B’blocks.The hydrogen bonding interactions are described by Yukawa potentials,where the hydrogen bonding donors and acceptors were modelled as two blocks smeared with opposite screened charges.The hierarchical microstructures with parallelly packed lamellae-in-lamellae(Lam)and 4.8.8 Archimedean tilting pattern(4.8.8)were observed at lower and higher hydrogen bonding density(θ),respectively.The hierarchy of Lam and 4.8.8 were demonstrated by the one-and two-dimensional density profiles and the underlying order of the large-length-scale and small-length-scale microstructures were also clarified.It was found that the 4.8.8 is favorable to the stronger hydrogen bonding density or interactions.Asθincreases,the microphase transition from Lam to 4.8.8 occurs atθ=0.34,which is mainly attributed to the optimization of the electrostatic energy and conformational entropy with sacrificing the interfacial energy.This work can provide a new strategy to understand the supramolecular self-assembly as well as the mechanism behind the formation of complex hierarchical microstructures.

Artificial stepwise light harvesting system in water constructed by quadruple hydrogen bonding supramolecular polymeric nanoparticles

Stepwise energy transfer is ubiquitous in natural photosynthesis,which greatly promotes the widespread use of solar energy.Herein,we constructed a supramolecular light harvesting system based on sequential energy transfer through the hierarchical self-assembly of M,which contains a cyanostilbene core flanked by two ureidopyrimidinone motifs,endowing itself with both aggregation-induced emission behavior and quadruple hydrogen bonding ability.The monomer M can self-assemble into hydrogen bonded polymers and then form supramolecular polymeric nanoparticles in water through a mini-emulsion process.The nanoparticles were further utilized to encapsulate the relay acceptor ESY and the final acceptor NDI to form a two-step FRET system.Tunable fluorescence including a white-light emission was successfully achieved.Our work not only shows a desirable way for the fabrication of efficient two-step light harvesting systems,but also shows great potential in tunable photoluminescent nanomaterials.

Self-assembly of Hydrazide-based Heterodimers Driven by Hydrogen Bonding and Donor-Acceptor Interaction

A new series of hydrogen bonding-driven heterodimers have been self-assembled in chloroform from hydrazide-based monomers. Additional intermolecular donor-acceptor interaction between the electron-rich bis（p-phenylene）-34-crown-10 unit and the electron-deficient naphthalene diimide unit has been utilized to increase the stability of the dimmers, and pronounced cooperativity of the two discrete non-covalent forces to stabilize the dimer has been revealed by the quantitative ^1H （2D） NMR and UV-Vis experiments.