Self-assembled Supramolecular Structures Research Articles

Fibrous aggregates from dinuclear zinc(ii) salphen complexes

Metal complexes composed of two zinc(II) salphen units that are bridged by a flexible hydrocarbon chain have been synthesized and characterized. Their self-assembled supramolecular structures were studied with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that all of the complexes displayed nanofibrillar morphology and that the surface texture and diameter can be altered by the addition of 4,4'-bipyridine and hydrophobic effects, respectively.

Photoinduced electron transfer from rail to rung within a self-assembled oligomeric porphyrin ladder

Photoinduced electron transfer in a self-assembled supramolecular ladder structure comprising oligomeric porphyrin rails and ligated dipyridyltetrazine rungs was characterized by transient absorption spectroscopy and transient direct current photoconductivity to be mainly from an oligomer (rail) to the center of a terminal tetrazine (rung), with the remaining hole being delocalized on the oligomer and subsequent charge recombination in 0.19 ns.

Supramolecular Assembly of Carbohydrate‐Functionalized Salphen–Metal Complexes

Metallosalphen complexes with peripheral glucose and galactose substituents were synthesized and characterized. Their self-assembled supramolecular structures were then studied with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that all of the complexes displayed aggregation in the solid-state. Zinc-salphen complexes showed a remarkably homogeneous helical nanofibrillar morphology, whereas the other metal complexes only displayed micron-sized clusters.

Focused ion beam processing and engineering of devices in self-assembled supramolecularstructures

Self-assembled supramolecular structures such as optical wires, films and 2D slabs offer anew generation of electronic and optical devices. In particular, self-assembled porphyrindevices, including those integrated onto silica and silicon platforms, open new opportunitiesin photonic applications spanning molecular biosensing, photovoltaics and telecommunications.All reports to date, however, largely highlight the potential but have not established a clearpathway to the actual implementation of more complex device prototypes. In this paper,we propose and demonstrate the use of a focused ion beam (FIB) to process andfabricate devices in porphyrin-based supramolecular structures. These self-assembledstructures have an initial root mean squared (rms) values for surface roughness of<0.5 nm as measured by atomic force microscopy. Under appropriate FIBprocessing and cutting conditions, the rms value for surface roughness falls to<0.4 nm, comparable with some of the best optical flatnesses obtained within,for example, structured optical fibres and integrated optical waveguides.The milling rate of the porphyrin structures was estimated to be∼70% of that of silica. The versatility of a FIB as a tool for rapid processing and fabricating1D and 2D photonic waveguide structures within supramolecular self-assembledplatforms is demonstrated by fabricating a 2D coupler, setting the groundwork fortrue optical device engineering and integration using these new organic systems.

Construction of Endo-Functionalized Two Dimensional Metallacycles via Coordination-Driven Self-Assembly

The synthesis of three endofunctionalized two-dimensional supramolecular metallacycles including two [2 + 2] rhomboids (5 and 6) and a [3 + 3] hexagon (7) is reported. The resulting self-assembled supramolecular structures, containing several nitrobenzyl moieties at their interior surface, have been fully characterized by multinuclear NMR ((31)P and (1)H) and electrospray ionization mass spectrometry. A significant C-H...O hydrogen bonding between the nitrobenzyl acceptor and the edge molecules of the supramolecular architecture is observed in the small rhomboid 5 and this interaction gradually decreases upon the enlargement of the resulting polygonal structures from a small rhomboid 5 through a large rhomboid 6 to a hexagon 7. Molecular modeling with the MMFF force field gives a possible conformation of each self-assembly in different solvents and shows that the hydrophilic nitrobenzyl moiety prefers to be buried in the cavity of the resulting polygonal structures in nonpolar solvents, thus forming hydrogen bonds with the peripheral component building units.

Calix[4]arene‐Based Single‐Molecule Magnets

Calix[4]arene Based Single-Molecule Magnets** Georgios Karotsis, Simon J. Teat, Wolfgang Wernsdorfer, Stergios Piligkos, Scott J. Dalgarno* and Euan K. Brechin* Mr. G. Karotsis, Dr. E. K. Brechin, School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK. Fax: (+44)-131-650-6453 E-mail: ebrechin@staffmail.ed.ac.uk Dr. S. J. Dalgarno, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS. Fax: (+44)-131-451-3180 E-mail: S.J.Dalgarno@hw.ac.uk Prof. Dr. W. Wernsdorfer, Institut Neel, CNRS, Grenoble Cedex 9, France. Dr. S. Piligkos, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Denmark. Dr. S. J. Teat, Advanced Light Source, Berkeley Laboratory, 1 Cyclotron Road, MS6R2100, Berkeley, CA 94720, USA. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231. Single-molecule magnets (SMMs) [1] have been the subject of much interest in recent years because their molecular nature and inherent physical properties allow the crossover between classical and quantum physics to be observed. [2] The macroscopic observation of quantum phenomena - tunneling between different spin states, [3] quantum interference between tunnel paths [4] - not only allows scientists to study quantum mechanical laws in great detail, but also provides model systems with which to investigate the possible implementation of spin- based solid state qubits [5] and molecular spintronics. [6] The isolation of small, simple SMMs is therefore an exciting prospect. To date almost all SMMs have been made via the self-assembly of 3d metal ions in the presence of bridging/chelating organic ligands. [7] However, very recently an exciting new class of SMMs, based on 3d metal clusters (or single lanthanide ions) housed within polyoxometalates, [8] has appeared. These types of molecule, in which the SMM is completely encapsulated within (or shrouded by) a “protective” organic or inorganic sheath have much potential for design and manipulation: for example, for the removal of unwanted dipolar interactions, the introduction of redox activity, or to simply aid functionalisation for surface grafting. [9] Calix[4]arenes are cyclic (typically bowl-shaped) polyphenols that have been used extensively in the formation of versatile self-assembled supramolecular structures. [10] Although many have been reported, p- t But-calix[4]arene and calix[4]arene (TBC4 and C4 respectively, Figure 1A) are frequently encountered due to a) synthetic accessibility, and b) vast potential for alteration at either the upper or lower rim of the macrocyclic framework. [11] Within the field of supramolecular chemistry, TBC4 is well known for interesting polymorphic behavior and phase transformations within anti-parallel bi-layer arrays, while C4 often forms self-included trimers. [12] The polyphenolic nature of calix[n]arenes (where n = 4 – 8) also suggests they should be excellent candidates as ligands for the isolation of molecular magnets, but to date their use in the isolation of paramagnetic cluster compounds is rather limited. [13] Herein we present the first Mn cluster and the first SMM to be isolated using any methylene bridged calix[n]arene - a ferromagnetically coupled mixed-valence [Mn III2 Mn II2 ] complex housed between either two TBC4s or two C4s. Reaction of MnBr 2 with TBC4 and NEt 3 in a solvent mixture of MeOH/DMF results in the formation of the complex [Mn III2 Mn II2 (OH) 2 (TBC4) 2 (DMF) 6 ] (1) which crystallises as purple blocks that are in the monoclinic space group P2 1 /c. The cluster (Figure 1B) comprises a planar diamond or butterfly-like [Mn III2 Mn II2 (OH) 2 ] core in which the wing tip Mn ions (Mn1) are in the 3+ oxidation state and the body Mn ions (Mn2) in the 2+ oxidation state. This is a common structural type in Mn SMM chemistry, [14] but the oxidation state distribution here is highly unusual, being “reversed” from the norm in which the body Mn ions are almost always 3+. Indeed the “reversed” core has been seen only once before, in the cluster [Mn III2 Mn II2 (teaH) 2 (acac) 4 (MeOH) 2 ] 2+ (2) (teaH 3 = triethanolamine) and its analogues. [15] The Mn 3+ ions are in distorted octahedral geometries with the Jahn-Teller axes defined by O5(DMF)-Mn1-O6(OH). The four equatorial sites are occupied by the oxygen atoms (O1-O4) of the TBC4, two of which bridge in a µ 2 -fashion to the central Mn 2+ ions (Mn1-O4-Mn2, 103.5°; Mn1-O1-Mn2, 105.4°). These are connected to each other (Mn2-O6-Mn2’, 94.7°) and to the Mn 3+ ions (Mn1-O6-Mn2, 100.4°; Mn1- O6-Mn2’, 98.8°) via two µ 3 -bridging OH - ions, with the two remaining equatorial sites (completing the distorted octahedral geometry on Mn2) filled by terminal DMF molecules. There are no inter-molecular H-bonds between symmetry equivalents of 1, with the closest

Shape and Size Effects of ZnO Nanocrystals on Photocatalytic Activity

A wet-chemical method was employed to prepare zinc oxide nanocrystals having controlled morphology through thermal decomposition of a zinc precursor in self-assembled supramolecular structures in solvent under mild conditions. This solution method offers finer tailoring of the size and shape of the nanocrystals and is complementary to most reported physical methods. Understanding the morphological effects of pure or modified zinc oxide nanocrystals on photocatalytic activity is important in regard to enhanced solar energy capture and utilization but has been scarcely addressed in the past. The photocatalytic rate was found to have no dependence on ZnO particle size, but the shape factor seems to be of overriding importance. Hexagonal platelike nanocrystals were found to display at least 5 times higher activity than rod-shaped crystals, which clearly suggests that the polar (001) and (001) faces are more active surfaces than the nonpolar surfaces perpendicular to them.

Synthesis, structural characterization and solvent effect of copper(II) complexes with a variational multidentate Salen-type ligand with bisoxime groups

Four new solvent-induced Cu(II) complexes with the chemical formulae [{Cu(HL)(CH 3OH)} 2Cu] · CH 3OH ( 1), [{(Cu(HL)) 2(CH 3CH 2OH) 2}Cu] ( 2), [{CuL(H 2O)} 2Cu 2] · 2CH 3CH 2CH 2OH ( 3) and [{(Cu(HL)) 2(CH 3CH 2CH 2CH 2OH) 2}Cu] ( 4), where H 4L = 6,6′-dihydroxy-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol, have been synthesized and characterized by elemental analyses, 1H NMR, FT-IR, UV–Vis spectra, TG-DTA, molar conductances and X-ray crystallography. Complexes 1, 2 and 4 have an elongated square-pyramidal geometry with an unusually long bond from the penta-coordinated Cu(II) centres to the oxygen atoms of the apically coordinated solvent (methanol, ethanol or n-butanol) molecules for the terminal Cu(II) ions, and a square planar geometry distorted tetrahedrally for the central Cu(II) ion. In complex 3, the terminal Cu(II) ions have trigonal bipyramidal coordination geometries constituted by equatorial O 2N donor sites, with one oxygen atom from one of the coordinated water molecules and one nitrogen atom from a completely deprotonated L 4− ligand unit in the axial positions, and the central Cu(II) ions are in slightly tetrahedrally distorted square planar geometries constituted by four phenoxo oxygen donors from two completely deprotonated L 4− ligand units, and these form a tetrametal Cu–O–Cu–O–Cu–O–Cu–O eight-membered ring. These four complexes exhibit strong hydrogen bonding interactions in the solid state. Moreover, co-crystallizing n-propanol molecules link two other adjacent complex molecules into a self-assembled infinite 2D supramolecular structure via the intermolecular hydrogen bonds in complex 3.

A new tripodal poly-imine indole-containing ligand: Synthesis, complexation, spectroscopic and theoretical studies

A novel flexible tripodal ligand derived from 3-methylindole, (“InTREN” L), and its mononuclear Zn(II), Cu(II), Ni(II), Hg(II) and Pd(II) complexes are described. All compounds gave analytically pure solid samples. Characterisation of the compounds was accomplished by 1H NMR, IR and absorption spectroscopies, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and elemental analysis and their geometry optimized using density functional theory (DFT). Time-dependent–density functional theory (TD–DFT) calculations have been used to assign the lowest energy absorption bands of the free ligand and the Zn(II) complex. The system is a very good candidate for in situ recognition/coordination effects by MALDI-TOF-MS spectrometry and absorption spectroscopy. The presence of three indole groups in InTREN opens up the possibility to synthesize new three-dimensional self-assembly supramolecular structures.

Understanding Self-Assembled Amphiphilic Peptide Supramolecular Structures from Primary Structure Helix Propensity

Small amphiphilic peptides are attractive building blocks to design biocompatible supramolecular structures via self-assembly, with applications in, for example, drug delivery, tissue engineering, and nanotemplating. We address the influence of systematical changes in the amino acid sequence of such peptides on the self-assembled macromolecular structures. For cationic-head surfactant-like eight-residue peptides, the apolar tail amino acids were chosen to systematically vary the propensity to form an alpha-helical secondary structure while conserving the overall hydrophobicity of the sequence. Characterization of the supramolecular structures indicates that for short peptides a beta-sheet secondary structure correlates with ribbonlike assemblies while random-coil and alpha-helical secondary structures correlate with assembly of rods.

Structure−Property Relationship for Two-Photon Absorbing Multiporphyrins: Supramolecular Assembly of Highly-Conjugated Multiporphyrinic Ladders and Prisms

Two-photon absorption (TPA) phenomena of a series of single-strand as well as supramolecular self-assembled ladders and prisms of highly conjugated ethyne bridged multiporphyrin dimer, trimer, and star shaped pentamer have been investigated. The ligand mediated self-assembled supramolecular structures were characterized by UV-visible spectroscopy and small- and wide-angle X-ray scattering (SAXS/WAXS) analysis. The TPA cross section values of multiporphyrins increase nonlinearly from approximately 100 to approximately 18000 GM with an increased number of porphyrin units and elongated pi-conjugation length by virtue of charge transfer and excited-state cumulenic configurations. The observed opposite TPA behavior between their supramolecular ladder and prism configurations necessitates the importance of interstrand interactions between the multiporphyrinic units and the overall shape of the assembly. Furthermore, the diminished TPA cross section of the pentamer, despite the increased pi-conjugation resulting from duplex formation suggests that destabilizing the essential functional configurations at the cost of elongation of pi-delocalization pathway must cause unfavorable effects. We have also shown that one- and two-photon allowed energy-levels of linear multiporphyrins are nearly isoenergetic and the latter transition originates exclusively from the extent of pi-delocalization within the molecule. The identical TPA maximum position of the trimer and pentamer indicates that the TPA of the pentamer arises only from its basic trimer unit in spite of its extended two-dimensional pi-conjugation pathway involving five porphyrinic units.

Diversity Oriented High-Throughput Screening of 1,3,4-Oxadiazole Modified Chlorophenylureas and Halogenobenzamides by HPLC with Peptidomimetic Calixarene-Bonded Stationary Phases

Retention profiles in series of the neutral and highly hydrophobic 1,3,4-oxadiazoles containing chlorophenylurea and halogenobenzamide moiety and indicating analgesic activity were determined in the isocratic standard- and narrow-bore HPLC systems employing, respectively, various octadecylsilica and different calixarene bonded stationary phases. When acetonitrile - 2.65 mM phosphoric acid (55 : 45, %, v/v), pH* 3.25, mobile phase was applied retention of these compounds increased with decline of their overall hydrophobicity according to the general preference of more polar compounds by calixarene cavity in time of its non-specific host-guest supramolecular interactions with halogenated substances. The size of calixarene nanocavity and its upper-rim substitution did not change the observed retention order, resolution and selectivity of separation for oxadiazoles. Compared to the retention on the non-end-capped and the highly-end-capped octadecylsilica HPLC column a most improved separation of some regioisomers of halogenated 1,3,4-oxadiazoles were observed on both used calixarene-type HPLC supports. In addition, preliminary data on the self-assembled supramolecular crystal structure of exemplary 1,3,4-oxadiazolchlorophenylurea with cis-elongated conformation was reported and formation of the monovalent inclusion host-guest complexes between 1,3,4-oxadiazoles and each calixarene-type stationary phase was studied with molecular modelling MM+ and AM1 methods. The structural, isomeric and energetic factors leading to the hydrogen bond stabilized inclusion complexes between these species were considered and used for explanation of observed retention sequence and selectivity of 1,3,4-oxadiazoles separation in applied calixarene-based HPLC systems. All these data would be useful in future development of optimized procedures enabling encapsulation of 1,3,4-oxadiazolurea-type drugs with calixarenes.

Large photoactive supramolecular ensembles prepared from C60–pyridine substrates and multi-Zn(ii)–porphyrin receptors

Fullerene derivatives bearing a pyridine sub-unit have been prepared. Their ability to form self-assembled supramolecular structures with mono- and polytopic Zn(II)–porphyrin receptors has been first evidenced by UV-vis studies. These supramolecular complexes are multi-component photoactive devices, in which the emission of the porphyrinic receptor is dramatically quenched by the fullerene units. This new property, resulting from the association of the different molecular sub-units, also allowed us to investigate in detail the self-assembly process using fluorescence titrations. The binding studies revealed positive cooperative effects for the assembly of the C60–pyridine derivatives with polytopic receptors as a result of intramolecular C60–C60 interactions between the different guests assembled onto the multi-Zn(II)–porphyrin hosts.

A Self-assembled, Drug-deliverable Nanomaterial for Cartilage Tissue Engineering

AbstractThe current clinical treatment of cartilage defects involves autologous chondrocyte implantation into cartilage defect sites. However, one of the complications associated with this method is the lack of bonding between the implanted materials and natural tissue. Helical rosette nanotubes (HRNs) are novel biomimetic self-assembled supramolecular structures whose basic building blocks are DNA base-pairs. HRNs are similar in size to collagen in cartilage. Moreover, previous studies have shown that HRNs are biocompatible and increase the adhesion of numerous cells compared to other commonly used cartilage implant materials (like hydrogels and Ti). In addition, HRNs can solidify into a viscous gel at body temperatures under short periods of time. Thus, it is hoped that HRNs can serve as a novel in situ tissue implant to improve cartilage cell adhesion and functions. In this study, in order to heal cartilage rupture and regenerate cartilage during possible implantation, the mechanical properties of select hydrogel/HRN composites were tested. In addition, electro-spinning was used to generate three-dimensional, implantable, composite fibers encapsulated with chondrocytes and fibroblast-like type-B synoviocytes (SFB cells, a type of mesenchymal stem cell). Importantly, results showed that drug-delivered HRNs enhanced hydrogel adhesive strength and created a scaffold with nanometer-rough surface structures pertinent for cartilage regeneration. In this manner, this study provided an alternative cartilage regenerative material which relies on nanotechnology that can be injected as a liquid, solidify at body temperatures under short periods of time, have suitable mechanical properties to collagen, and promote cell functions.

Backbone‐modified amylin derivatives: implications for amyloid inhibitor design and as template for self‐assembling bionanomaterials

This report reviews our approach to the design, synthesis and structural/morphological analysis of backbone-modified amylin(20-29) derivatives. Depending on the position in the peptide backbone and the type of amide bond isostere/modification, the amylin(20-29) peptides behave either as inhibitors of amyloid fibril formation, which are able to retard amyloid formation of native amylin(20-29), or as templates for the formation of self-assembled supramolecular structures. Molecular fine-tuning of the hydrogen-bond accepting/donating properties allows the control over the morphology of the supramolecular aggregation motifs such as helical ribbons and tapes, ribbons progressing to closed peptide nanotubes, (twisted) lamellar sheets or amyloid fibrils.

Biological Soft Materials

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Biological Soft Materials

With one or two exceptions, biological materials are "soft", meaning that they combine viscous and elastic elements. This mechanical behavior results from self-assembled supramolecular structures that are stabilized by noncovalent interactions. It is an ongoing and profound challenge to understand the self-organization of biological materials. In many cases, concepts can be imported from soft-matter physics and chemistry, which have traditionally focused on materials such as colloids, polymers, surfactants, and liquid crystals. Using these ideas, it is possible to gain a new perspective on phenomena as diverse as DNA condensation, protein and peptide fibrillization, lipid partitioning in rafts, vesicle fusion and budding, and others, as discussed in this selective review of recent highlights from the literature.

Self-Assembled Supramolecular Architecture Based on an Achiral Bolaamphiphilic Diacid in Binary System

A new family of polymers that includes topologically complex polymers and self-assembled nanostructures has recently attracted much attention. The non-covalent selfassembly technique, unlike chemical reaction or polymerization methods, has the advantage of directly producing well-defined twoand three-dimensional structures such as sheets, rod, fibers, tubes, disks, and spheres. Notably, these nanostructures can be constructed with high efficiency and accuracy, and yet with minimum energy. Organic amphiphiles typically possess a chiral moiety as well as functional groups with potential to form multiple hydrogen bonds, such as sugars, peptides, or nucleotide bases. However, only a few examples for self-assembled supramolecular structures of organic amphiphiles consisting of achiral moieties have been described. Therefore, our initial motivation to prepare bolaamphiphilic diacids was to develop self-organized pseudo-linear polymers stabilized by intermolecular hydrogen-bonds, and that incorporated suitable guest additives with achiral functional groups. With this idea in mind, we employed a simple bola-form amphiphile (“bolaamphiphile”) 1, consisting of one diphenyl ether group as a hydrophobic moiety at the center, flanked by two carboxylic acids as the terminal hydrophilic groups. In 1, the linkage we introduce between the hydrophobic and the hydrophilic moieties is an amide group, known to form a linear hydrogen bond chain. We herein report the assembling behavior of 1 with and without guest additives. The additives such as 4,4'-dipyridyl (4,4'-bpy) and 2,2'-dipyridyl (2,2'-bpy) are so common that their interaction behaviors have been well-defined especially in the coordination polymer networks. We have investigated the influence of the dipyridyl additives on the morphologies of self-assembled 1 and self-assembled 1 combined by bpy which are denoted with [1] and [1+bpy], respectively, by optical microscopy, SEM, FT-IR, powder-XRD and differential scanning calorimetry (DSC). Achiral bolaamphiphile 1 was synthesized in three steps (Scheme 1). The monomethyl sebacate 2 was chlorinated with oxalyl chloride to give methyl-10-chloro-10-oxadecanoate 2. Reaction of 3 with 4,4'-oxydianiline afforded diamide derivative 4. Treatment of 4 with NaOH gave the desired product 1 as a brown powder. The self-assembly reactions of 1 (3-5 mg) with and without dipyridyl additives (3 equiv) were accomplished by dissolving the reactants in acidic, neutral, and basic conditions in water/ethanol (4:1 v/v, 50 mL) at 80 C, respectively. The pH of each solution was adjusted with 0.1 M NaOH or 0.1 M HCl aqueous solution. After the incubation of the solutions at room-temperature for several hours, the formation of stable supramolecular assemblies was confirmed. In the absence of additives, SEM pictures for [1] (0.50 mM) obtained at pH = 4 show a film-like structure (Figure 1a) whereas at pH = 7, the structures are comprised of bundles Scheme 1. Synthetic route for achiral bolaamphiphilic diacid 1.

Supramolecular Self-Assembly of Architecturally Variant α-Cyclodextrin Inclusion Complexes as Building Blocks of Hexagonally Aligned Microfibrils

Inclusion complexes (ICs) were prepared by the host−guest reaction between α-cyclodextrin (α-CD) and four poly(ε-caprolactone)s (PCLs) with different molecular architectures: star-shaped PCL (SPCL) with a radial architecture, random branched PCL (RPCL) with a conical architecture, poly(propylene glycol)−PCL block copolymer (PPG−PCL) with a diblock architecture, and PCL−diol (LPCL) with a linear architecture. Then, the ICs were self-assembled by treatment with suitable polar solvent such as THF. From WAXD, it was found that both the ICs and the self-assembled ICs (SA-ICs) obtained from THF treatment of ICs had hexagonally organized channel-type crystalline structure, resulting from inclusion complexation between α-CD and PCL chain. Combined results of WAXD, FE-SEM, and SAXS further revealed that ICs had the microfibril structure in which single IC strands were hexagonally aligned in the horizontal direction. The microfibrils in ICs were then reorganized by THF treatment, thereby developing well-defined supramolecular structure for ICs with RPCL (R−IC), PPG−PCL (P−IC), and LPCL (L−IC), except IC with SPCL (S−IC). From SAXS experiments, it was verified that the self-assembled supramolecular structures were attributed to continuous alignment of the microfibril by THF. Furthermore, SA-ICs with RPCL, PPG−PCL, and LPCL (R−SA-IC, P−SA-IC, and L−SA-IC, respectively) exhibited the different supramolecular structure, depending on the architecture of the respective polymeric guests. In particular, both R−SA-IC and P−SA-IC showed the microphase separated supramolecular structure because of block-selected inclusion complexation of α-CD as confirmed by 1H NMR. However, the radial architecture of SPCL was considered to hinder the continuous packing of microfibril, thereby supramolecular structure being not accomplished in S−SA-IC. Interestingly, the development of the supramolecular structures was found to be obtained only by treatment with the THF among the various polar solvents.

Using theory and computation to model nanoscale properties

This article provides an overview of the use of theory and computation to describe the structural, thermodynamic, mechanical, and optical properties of nanoscale materials. Nanoscience provides important opportunities for theory and computation to lead in the discovery process because the experimental tools often provide an incomplete picture of the structure and/or function of nanomaterials, and theory can often fill in missing features crucial to understanding what is being measured. However, there are important challenges to using theory as well, as the systems of interest are usually too large, and the time scales too long, for a purely atomistic level theory to be useful. At the same time, continuum theories that are appropriate for describing larger-scale (micrometer) phenomena are often not accurate for describing the nanoscale. Despite these challenges, there has been important progress in a number of areas, and there are exciting opportunities that we can look forward to as the capabilities of computational facilities continue to expand. Some specific applications that are discussed in this paper include: self-assembly of supramolecular structures, the thermal properties of nanoscale molecular systems (DNA melting and nanoscale water meniscus formation), the mechanical properties of carbon nanotubes and diamond crystals, and the optical properties of silver and gold nanoparticles.