Confined crystallization of polymers within anodic aluminum oxide templates

In this article, a review of recent literature on confined crystallization within nanoporous anodic aluminum oxide (AAO) templates is presented. For almost all infiltrated polymeric materials, crystal orientation within the nanopores is a function of pore diameter. T_c and T_m usually decrease and are a function of pore size. When no pore interconnection remains, the crystallization occur at large supercoolings in heterogeneity free environments. Hence, the nucleation mechanism changes from heterogeneous to surface or homogeneous nucleation. The crystallization kinetics of infiltrated polymers should be close to first order, since in confined environments nucleation is the determining step of the overall crystallization and Avrami indexes (n) of ～1 (or lower in some cases) should be obtained. Examples are provided where these conditions have been met and first order kinetics (n = 1) were measured as opposed to higher orders (n = 3?4) for the same polymer in the bulk. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1179–1194     

A polysaccharide/tetraphenylethylene-mediated blue-light emissive and injectable supramolecular hydrogel

A luminescent and injectable supramolecular hydrogel was successfully constructed through the non-covalent cross-linking of polymers mediated by tetraphenylethylene-bridged cyclodextrin oligomers, presenting the strong blue fluorescence, the reversible gelation behavior responsive to various external stimuli and the good mechanical property of shear thinning.     

Clip[5]arenes: A new family of molecular clips

Here we report the design and syntheses of two new triptycene-based rigid acyclic C-shaped hosts, clip[5]arenes C[5]OH and C[5]ME, and the strong host–guest complexation between C[5]OH and an electron-poor bipyridinium salt, paraquat G. The K_a value for the host–guest complex C[5]OH???G was calculated to be (1.09?±?0.36)??×??10⁵?M^?1 in acetone by using a non-linear curve-fitting method based on the UV–vis absorption titration experiments. Furthermore, based on this new host–guest recognition motif, a novel pseudopolyrotaxane-like supramolecular structure was constructed with C[5]OH threaded on polyviologen polymer VP-10.     

Syntheses,crystal structures,and properties of two dinuclear iron(III) complexes constructed with 1,2,3,5-benzenetetracarboxylic acid and chelating N-donor auxiliary coligands

Two dinuclear Fe(III) metal–organic complexes with tetracarboxylate and chelating N-donor ligands, [Fe(Hbtec)(phen)(H₂O)]₂·2H₂O (1) and [Fe(Hbtec)(bpy)(H₂O)]₂·2H₂O (2) (H₄btec = 1,2,3,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been prepared and characterized by elemental analysis, IR spectroscopic, and X-ray diffraction methods. Both complexes crystallize in the monoclinic space group P2₁/c with two Fe(III) ions bridged by two Hbtec^3? ligands into a dinuclear unit. Hydrogen bonding connects the dinuclear units into a 3-D framework. The dinuclear units are 10-connected nodes that produce a 3-D framework with topology Schläfli symbol as (3¹²·4²⁸·5⁵). Thermal stabilities and luminescent properties of the two complexes have also been investigated.     

A 2D Supramolecular Network Based on Aromatic π···π Stacking Interactions

Using ferrocenecarboxylic acid (FcCOOH) as organometallic ligand in the synthesis of heterometallic complexes led to the isolation of the compound [(FcCOO)Cu(bpy)₂](BF₄) · bpy · CH₃OH. It was characterized by IR spectroscopy, EA, powder XRD, UV, and TGA measurements. Single‐crystal X‐ray structural analysis revealed that a unique 2D supramolecular network purely formed by aromatic π ··· π stacking interactions was observed, namely, {[(FcCOO)Cu(bpy)₂](BF₄) · bpy · CH₃OH}_∞ ( 1 ). The solid UV/Vis diffuse reflectance spectrum revealed the optical energy gap of 1 to be 3.54 eV, which is dramatically blue shifted compared with the value of ferrocene. Experimental results of thermal analysis and electrochemical analysis show that 1 has good thermal and better electrochemical stability.     

Coordination‐directed and Hydrogen‐bonded Assembly of Supramolecular Architectures Constructed from Diverse Coordination of Linear,Triangular, Tetragonal Pyramid,Trigonal Bipyramid,and Octahedral Mononuclear Units

Reaction of a imidazole phenol ligand 4‐(imidazlo‐1‐yl)phenol (L) with 3d metal salts afforded four complexes, namely, [Ni(L)₆] · (NO₃)₂ ( 1 ), [Cu(L)₄(H₂O)] · (NO₃)₂ · (H₂O)₅ ( 2 ), [Zn(L)₄(H₂O)] · (NO₃)₂ · (H₂O) ( 3 ), and [Ag₂(L)₄] · SO₄ ( 4 ). All complexes are composed of monomeric units with diverse coordination arrangements and corresponding anions. All the hydroxyl groups of monomeric cations are used as hydrogen‐bond donors to form O–H ··· O hydrogen bonds. However, the coordination habit of different metal ions produces various supramolecular structures. The Ni^II atom shows octahedral arrangement in 1 , featuring a 3D twofold inclined interpenetrated network through O–H ··· O hydrogen bond and π–π stacking interaction. The Cu^II atom of 2 displays square pyramidal environment. The O–H ··· O hydrogen bond from the [Cu(L)₄(H₂O)]²⁺ cation and lattice water molecule as well as π–π stacking produce one‐dimensional open channels. NO₃^– ions and lattice water molecules are located in the channels. 3 is a 3D supramolecular network, in which Zn^II has a trigonal bipyramid arrangement. Two different rings intertwined with each other are observed. The Ag^I in 4 has linear and triangular coordination arrangements. The mononuclear units are assembled into a 1D chain by hydrogen bonding interaction from coordination units and SO₄^2– anions.     

A Schiff-base cross-linked supramolecular polymer containing diiminophenol compartments and its interaction with copper(II) ions

We report here the preparation of a Schiff-base linked organic polymer 1 based on linkages containing the potent supramolecular aggregator benzene-1,3,5-tricarboxamide, connected through 2,6-diiminophenol metal binding pockets into a cross-linked polymer. The morphological and physical properties of this material are studied using electron microscopy techniques, thermal analysis, NMR, fluorescence spectroscopy and gas adsorption studies. The interaction of the polymer 1 with Cu^II ions is then investigated by soaking the material with methanolic copper acetate solution, and studying the resulting aggregates using EDX microscopy and FTIR spectroscopy. A small-molecule model compound 2 is also prepared and crystallographically characterised to act as a spectroscopic comparison, providing strong evidence that 1 interacts with copper ions through a nucleation/seeding mechanism for the growth of microcrystalline copper acetate deposits, rather than via chemisorption of the copper ions within the diiminophenol binding pockets. Preliminary results suggest a similar mechanism for Co^II adsorption, while Zn^II ions exhibit a separate interaction mode.     

Supramolecular polymers from coronene multicarboxylates and multipyridiniums in water stabilized by ion-pair attraction and aromatic stacking

Coronene tatracarboxylate CTC and octacarboxylate COC have been utilized to interact with dipyridinium DP and tetrapyridinium TP to assemble new supramolecular polymers in water. It was revealed that CTC interacted with DP and TP in 1:2 and 1:1 stoichiometry, whereas the binding between COC and DP and TP occurred in 1:4 and 1:2 stoichiometry. For all complexations, DP and TP behaved as a uni- or siamesed tweezers to clamp CTC or COC driven by ion-pair attraction and hydrophobically driven stacking of the pyridinium and coronene units. Apparent association constants were determined to be 33400 (CTC/DP), 9400 (COC/DP), 151000 (CTC/TP), and 89000 (COC/TP) M^?1, respectively, for the single clamping binding motif of the four complexes. Dynamic light scattering and isothermal titration calorimetric experiments supported that the mixtures of CTC and COC with TP formed linear and cross-linked supramolecular polymers.     

Investigation of the retention mechanism of naphthol and benzenediol on calix[4]arene stationary phase based on quantum chemistry calculations

Calixarenes are macrocyclic oligomers having the shape of a conical vase. Their inner cavity can accommodate various guest molecules, i. e. form supramolecules. Thus, calixarenes can be employed to manipulate selectivity in separation sciences. The essential step of separation is the interaction between calixarene and analytes. Therefore, in the present work, the retention mechanisms of benzenediol and naphthol positional isomers on a calix[4]arene column were investigated. The optimized supramolecular structures showed that there exist hydrogen bonding and pi-pi interactions for benzenediol, and for naphthol the pi-pi interactions dominate. Thermodynamic results from quantum chemistry calculations using DFT-B3LYP/STO-3G** basis set were consistent with the retention behaviors of benzenediol and naphthol positional isomers on the calix[4]arene column. This work will provide theoretical support for the design of new calixarene stationary phases.     

Synthesis and Characterization of Intercluster Compounds Consisting of Various Gold Clusters and Differently Charged Keggin Anions

The crystal structures of five intercluster compounds consisting of gold clusters and Keggin anions have been determined by single‐crystal x‐ray diffraction: [Au₉(PPh₃)₈][PMo₁₂O₄₀] (P4/n, Z = 2, a = 24.0195(13), c = 13.6818(10) Å), [Au₉(PPh₃)₈][HSiMo₁₂O₄₀] (P4/n, Z = 2, a = 24.270(3), c = 13.752(2) Å), [Au₉(PPh₃)₈][H₃CoW₁₂O₄₀] (P4/n, Z = 2, a = 24.4776(16), c = 13.7759(13) Å), [Au₈(PPh₃)₈]₂[SiMo₁₂O₄₀] (Pbca, Z = 4, a = 36.269(4), b = 24.488(3), c = 38.612(4) Å) and (nBu₄N)[Au₉(Ptol₃)₈][SiMo₁₂O₄₀] (Cc, Z = 4, a = 24.832(5), b = 24.955(5), c = 40.096(8) Å, β = 106.744(3)°). In these compounds, the charges of the building blocks were varied. Altering the charge on the Keggin anion in combination with the [Au₉(PPh₃)₈]³⁺ cluster gave rise to isostructural compounds as the charge is compensated by protonation of the polyoxometalate anion. Varying the charge or the ligand type of the gold cluster led to compounds with a completely different packing principle.