bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission Electron Microscopy (
TEM
)
Authors: Kikuchi Jun‐ichi , Yasuhara Kazuma 
Published: February 2012

Abstract
Transmission electron microscopy (TEM) is a powerful tool for imaging supermolecules on a nanometer scale. In TEM apparatus, the specimen is illuminated using electron beams in high‐vacuum conditions, and the transmitted beam makes the image magnified from about fifty to over one million times. In principle, contrast of the TEM image arises because of the differences in electron density of the elements constituting the specimen. Three types of specimen preparation techniques — negative staining, freeze‐fracture, and cryogenic TEM — are generally employed for imaging supermolecules. TEM tomography showing the three‐dimensional structure and the electron diffraction providing information on the periodic ordered structure of the specimen are described. In addition, two spectroscopic measurements performed by using the TEM apparatus, electron energy‐loss spectroscopy (EELS) and energy dispersive X‐ray spectroscopy (EDS), are effective for structural analysis of the specimen. Principles and protocols for these techniques and measurements are described, and potential of TEM for micro‐/nanoimaging in supramolecular chemistry is discussed with reference to the TEM imaging examples that have been reported recently.
Isothermal Titration Calorimetry in Supramolecular Chemistry
Authors: Schmidtchen Franz P. 
Published: February 2012

AbstractAmong the many options to measure molecular interactions in solution, isothermal titration microcalorimetry (ITC) stands out as an almost universal, label‐free, operationally fast, fully computer‐operated, and thus quite robust method to acquire all thermodynamic parameters necessary to characterize the energetics of intermolecular association. Provided that there is an enthalpic response accompanying the mutual molecular interaction, the free energy, molar enthalpy, and, by using the Gibbs–Helmholtz equation, also the molar entropy can be determined in a single run. The present review describes the fundamental concept, the methodological aspects concerning the range accessible to direct determinations, and its potential expansion. Special focus is on data evaluation and the intrinsic limits to translate the macroscopic instrumental output into the illumination of the microscopic events happening on the molecular scene. The scope of ITC as a means to characterize thermodynamic equilibria is illustrated with the help from recent applications spanning from low‐molecular host–guest chemistry to multimeric assembly of surfactants observable as phase changes.
Circular Dichroism Spectroscopy*Dedicated to Professor Koji Nakanishi on the occasion of his 85th birthday.
Authors: Taniguchi Tohru , Usuki Toyonobu 
Published: February 2012

Abstract
Circular dichroism (CD) spectroscopy has been a powerful technique in the structural analysis of various chiral supramolecular systems. In order to obtain correct structural information it is essential to understand the basic concepts of CD, to optimize the measurement condition, and to properly interpret the data. This chapter addresses the following topics in order for the readers to use CD spectroscopy more efficiently: (i) the fundamental principles of CD spectroscopy and the technical point of the measurements; (ii) the exciton chirality method and its use in the configurational and conformational analysis of supermolecules; (iii) the introduction of basic concepts of induced CD; and (iv) the recent developments of computational simulation of CD spectra. We show that these basic concepts are applicable to the interpretation of CD data of further complicated supramolecular systems, by showing examples of a broad range of chiral supermolecules such as host‐guest systems, mechanically interlocked molecules, molecular machines, foldamer, polymers, and self‐assembled molecules. This chapter also briefly introduces the applications of a newly emerged CD (vibrational circular dichroism (VCD) spectroscopy) to supermolecules.
Rheology
Authors: Chassenieux Christophe , Bouteiller Laurent 
Published: February 2012

Abstract
Rheology is the obvious method of choice when one wants to characterize viscous solutions or gels. This technique is often used in the field of supramolecular chemistry in a rather qualitative manner, in order to probe, for example, if a particular assembly is larger than a reference system. However, the technique of rheology can yield significantly more information. We show through selected examples that rheology can yield useful information not only about the size of the assemblies but also about their structure (linear, cyclic, star shaped, etc.), dynamics (self‐healing), and self‐assembly mechanisms.
Langmuir–Blodgett Films
Authors: Ramsden Jeremy J. 
Published: February 2012

AbstractLangmuir (floating) monolayers, the precursors to Langmuir–Blodgett (LB) films, are outlined before dealing with the monolayer transfer to create the LB films themselves. The Langmuir–Schaefer (LS) transfer technique is presented as a subtype of the LB approach. A guide to the metrology of the films is given. Posttransfer modifications of LB films are covered as a useful ways to extend the range of obtainable materials and structures. Finally, applications are surveyed. Most current interest is in using LB films as research tools rather than as a means of high volume nanoscale fabrication, although the potential offered by the use of novel molecules to build up precise supramolecular structures is emphasized.
Dynamic Light Scattering in Supramolecular Materials Chemistry
Authors: Braun Jörg , Renggli Kasper , Razumovitch Julia , Vebert Corinne 
Published: February 2012

AbstractThis chapter reviews the use of dynamic light scattering (DLS) in the wide field of supramolecular materials chemistry through nonexhaustive yet representative examples. Aside from demonstrating the broad field of applicability of DLS, the basic principle of light scattering with reference to excellent publications on the theoretical background is recalled to highlight the major limitations of the technique to prevent misuse.
Brewster Angle Microscopy
Authors: Stine Keith J. 
Published: February 2012

AbstractBrewster angle microscopy (BAM) is the technique of choice for imaging monolayers of supramolecular systems at the water–air interface. BAM is based on the optical principle of the Brewster angle, in whichp‐polarized light incident on the water surface at the Brewster angle is nearly completely extinguished. The presence of a monolayer violates this condition and provides the basis for imaging. BAM is a general method for imaging either spread or adsorbed monolayers. BAM can be applied to study phase transitions, characterize domain microstructure, study phase separation in mixed monolayers, follow changes due to complex formation, and observe collapse or multilayer formation. The method is also sensitive to the presence of optical anisotropy in monolayer films due to variations in molecular orientation. BAM has been applied to monolayers of a range of macrocyclic compounds, especially calixarene and cyclodextrin derivatives. BAM has been applied to study chiral phase separation in monolayers of chiral amphiphiles. It is possible to apply BAM in a quantitative manner to estimate variations in monolayer thickness.
X‐Ray Diffraction: Addressing Structural Complexity in Supramolecular Chemistry
Authors: Enright Gary D. , Takeya Satoshi , Ripmeester John A. 
Published: February 2012

AbstractOver the past 15 years, significant advances in X‐ray diffraction instrumentation have completely transformed how chemists make use of this technique. This is particularly evident in the field of supramolecular chemistry, where characterizing the structural motifs of molecular crystals is crucial to the understanding of the weak intermolecular forces that are responsible for crystal stability. This chapter describes the advances that are typical of instrumentation available in most chemistry departments as well as the advances in data treatment, structure solution, and refinement that have become possible.
Atomic Force Microscopy (
AFM
)
Authors: Hyotyla Janne T. , Lim Roderick Y. H. 
Published: February 2012

Abstract
Atomic force microscopy (AFM) is a stylus‐based technique that uses sub‐nanonewton force sensitivity to image surfaces at sub‐nanometer resolution. As a surface‐sensitive tool, AFM is ideal for investigating the properties and local morphology of surface‐grafted supramolecules and (bio)polymers, which play important roles in mediating interfacial processes ranging from tribology to colloidal stability and biology. Moreover, the versatility of AFM to operate in diverse environments (i.e., air, liquid, or vacuum) adds to its appeal in comparison to other surface methods. Given its capability for high‐resolution imaging, force measurements, and nanomechanical manipulation, AFM is directly applicable to studies of stimuli‐responsive polymers, biomaterials, and polymeric nanostructures.
Scanning Electron Microscopy
Authors: Li Zhan‐Ting , Zhao Xin 
Published: February 2012

Abstract
The chapter first introduces the SEM (scanning electron microscopy) method and the characteristics of different SEM techniques. Then, its applications in investigating supramolecular systems — including supramolecular organogels; liquid crystals and polymers; nanoscaled self‐assembled tubes, rods, ribbons, and spheres; and supramolecular chirality — are provided, which stresses the usefulness of SEM in observing their morphologies and helping to establish the self‐assembling mechanisms.
Scanning Near‐Field Optical Microscopy (
SNOM
)
Authors: Kaupp Gerd 
Published: February 2012

Abstract
The successful artifact‐free scanning near‐field optical microscopy (SNOM) for rough surfaces with the versatile apertureless internal reflection in the shear‐force gap technique is reviewed and compared with the difficulties associated with apertureless scattering and aperture SNOM techniques. The most economical technique requires sharp, economically self‐pulled, tapered waveguide tips and is enabled by a unique reflection enhancement in the shear‐force gap that depends linearly on the damping settings. Owing to numerous factors that determine the enhancement, strong chemical contrasts are obtained even between similar materials on composite materials. Unlike aperture SNOM, the contrast in an internal‐reflection SNOM is precisely at the site of the chemical interface and the optical resolution is below 10 nm, which is equal to or better than the simultaneous AFM resolution at tip radii of about 10 nm. This enables efficient local spectroscopy (fluorescence, Raman, SERS), industrial (dental alloys, textile dyeing, nanoparticle dyes, sustainable chemical production, etc.), and medicinal applications (organelles, cancer prediagnosis, etc.), and helps in the elucidation of supramolecular mechanisms, all at the nanometric level. SNOM analyses of waste‐free supramolecular gas–solid and solid–solid reactions secure far‐reaching anisotropic molecular migrations within crystals, and also in solid‐state photoreactions. Such mechanistic foundation was not possible with previous “topochemistry” hypotheses, which impeded the maturing of the unparalleled sustainable supramolecular productions, by forbidding these migrations.
Scanning Tunneling Microscopy (STM)
Authors: Stöhr Meike 
Published: February 2012

AbstractThe scanning tunneling microscope (STM) offers the unique possibility to gain information on structural and electronic properties of a conducting surface down to the atomic scale. It was only a question of time until this potential was discovered for the investigation of molecules adsorbed on a substrate surface. Moreover, it was realized that invaluable information on surface‐supported supramolecular architectures can be obtained which complements the knowledge on supramolecular systems in solution as well as in the solid state in a beneficial way. In addition, supramolecular engineering on solid substrates is expected to contribute to the development of functional nanomaterials, which boosted the research activities in this field substantially. In the beginning, the main focus of STM investigations was on the mere visualization of the adsorbed molecules, whereas now it addresses a variety of questions that comprises research on intermolecular and molecule–substrate interactions including electronic properties, the determination of the adsorption site, surface dynamics, and reactions. Especially, spectroscopy and manipulation techniques were important advancements for the development of the field.
Crown and Lariat Ethers
Authors: Cragg Peter J. , Vahora Rafik 
Published: February 2012

AbstractCrown ethers first came to prominence in the late 1960s through the pioneering work of Charles Pedersen. The discovery that they bind cations based on complementarity between the crown ether cavity and the size of the cation has been a driving force in macrocyclic and supramolecular chemistry ever since. Many derivatives have been synthesized, including those with side arms known collectively as lariat ethers, and their cation selectivity used in molecular sensors. The history of crown and lariat ethers is discussed together with their syntheses, structural and binding evidence for size selectivity, and their industrial and clinical applications. Crown and lariat ethers have found use as phase‐transfer catalysts, modifiers for chromatographic media, sensors for numerous chemical species, critical analyte detectors, and can even enhance insecticide activity. They have been used to probe important biological phenomena, including enzyme specificity, the nature ofin vivocation‐π interactions in proteins and transmembrane ion transport, through the synthesis of model compounds.
Azacoronands and Azacyclophanes
Authors: Bianchi Antonio , García‐España Enrique 
Published: February 2012

AbstractAzacycloalkanes and azacyclophanes are among the first macrocyclic ligands developed in the field of supramolecular chemistry. Since they are polyamines, they show dual nature in the coordination of both metal cations, when they are in the free‐base form, and anionic species, when they are protonated. As a matter of fact, they played a key role in the birth of macrocyclic chemistry of transition metal complexes and anion coordination chemistry. Furthermore, azacyclophanes fostered also the birth of apolar complexation in aqueous solution, since their aromatic units act as binding sites for apolar substrates.
Schiff Base and Reduced Schiff Base Ligands
Authors: Sreenivasulu Bellam 
Published: February 2012

AbstractSupramolecular chemistry of Schiff base ligands and their reduced homologues is rapidly growing and gaining increased attention due to their convenient and straightforward synthetic methods and a wide range of complexation modes with almost all types of metal ions. In fact, the phenomenon of molecular recognition, self‐organization and self‐assembly, and host–guest chemistry through covalent and noncovalent interactions is pivotal to the understanding and development of supramolecular chemistry. In this direction, several forms of acyclic and macrocyclic Schiff bases and their reduced forms are employed to gain more insights and correctly ascertain the effect of different donor atoms, their relative position, the number and size of the chelating rings formed, the flexibility, and the geometry around the coordinating moiety on the molecular recognition process and selective binding of cations, anions, and/or neutral species. In this connection, this chapter deals with the supramolecular and molecular recognition properties and interesting host–guest complexes and metalla–supramolecular network structures derived from several acyclic and cyclic Schiff bases and reduced Schiff base ligands. Various solid‐state metalla‐supramolecular network structures are delineated ranging from hydrogen‐bonded linear polymers and helical coordination polymers, and 2D sheets to 3D network architectures constructed via N H⋯O, C O⋯H Osolvent, O H⋯O, N H⋯O C, hydrogen bonds and C O⋯π, C H⋯π, and π–π stacking interactions. This review gives an account of the observed structural diversity in relation to the role of different donors and acceptors, aqua ligands and solvents, nature of the ligands and metal ions, and the coordination geometry around the metal ions.
Podands
Authors: Swinburne Adam N. , Steed Jonathan W. 
Published: February 2012

AbstractThe term podand, originally applied to alkali metal cation‐binding ligands with two or more pendant polyether arms, has expanded in usage and concept to encompass a vast range of cation‐ and anion‐binding receptors as well as hosts for molecular guests based on a multibinding‐site, acyclic structure. The multiarmed podands lead naturally into the key concept of multivalency and they are the conceptual precursors of dendrimers. This chapter covers the core concepts behind classical alkali metal cation‐binding podands and surveys the basics of a range of cation‐binding podands as well as highlights the huge diversity of anion‐binding podands that has arisen in recent years. A flavor of the state of the art and future direction of podands for molecular guests is also noted.
Supramolecular Phthalocyanine‐Based Systems
Authors: Claessens Christian G. , Martínez‐Díaz M. Victoria , Torres Tomás 
Published: February 2012

Abstract
Phthalocyanines (Pcs) represent one of the most widely studied macrocyclic aromatic ring systems. Their intrinsic electronic delocalization, the presence of central metals, and the introduction of appropriate peripheral and/or axial functionalization give rise to numerous features that allow the organization of these macrocycles at a supramolecular level. Noncovalent interactions have a strong influence on Pc properties, including photoinduced electron‐ and energy‐transfer events that have inspired the development of supramolecular Pc‐based systems as photosynthetic model systems. In this chapter, the propensity of Pcs to self‐aggregate by strong π–π interactions, as well as the influence of the central metal ion and the solvent in the preferential aggregation modes, is highlighted. The π‐stacking as a basic feature for the self‐assembling of Pcs, particularly the donor–acceptor (D–A) interactions between complementary electron‐deficient and electron‐donor molecular components, is analyzed. Further attention is devoted to the strong and directional metal–ligand interactions that are among the most popular molecular recognition tools for the construction of well‐defined supramolecular architectures based on Pcs. The discussions are mainly centered on zinc(II) and ruthenium(II) phthalocyanines. Concerning Pc‐analogs, subphthalocyanines (SubPcs) containing pyridyl substituents have been assembled into supramolecular capsules through peripheral pyridine–Pd–pyridine complexation. On the other hand, electrostatic interactions are also presented as a simple way to form Pc face‐to‐face hetero‐ensembles by self‐assembly of adequate components bearing oppositely charged substituents. The introduction of crown‐ether subunits at the periphery of the macrocycle also allows complexation of exocyclic metals, which may be used for supramolecular organization of these systems. The influence of hydrogen‐bonding interactions on the aggregation properties of Pcs has also been highlighted. Finally, the noncovalent interactions that allow the organization at the nanoscale level of Pcs and SubPcs on different surfaces are analyzed utilizing a wide range of scanning probe microscopies.
Guanidinium‐Based Receptors for Oxoanions
Authors: Conley Matthew P. , Valero Julián , de Mendoza Javier 
Published: February 2012

AbstractNature frequently uses guanidinium–anion interactions for stabilization of protein structure or for catalytic reactivity in enzyme active sites. Studies of artificial guanidinium receptors show that strong hydrogen‐bonded ion pairs with oxoanion substrates are formed in apolar media. This property has been used for the efficient extraction or membrane transport of racemic amino acids to give enantio‐enriched products. However, inclusion of additional hydrogen‐bond donors, or guanidinium functionalities, in the receptor molecule can stabilize the ion‐pair interaction in polar protic solvents, allowing the detection of oxoanions near biologically relevant conditions. This approach has been used to recognize simple carboxylates and complex structures, such as proteins and DNA, in buffered water. Recent examples of catalysts containing guanidiniums show that this exceptional functional group can give both cooperative and regioselective reactivity to the system.
Synthetic Peptide‐Based Receptors
Authors: Kubik Stefan 
Published: February 2012

AbstractSynthetic receptors that are solely or at least partly constructed from peptide segments can be regarded as conceptual links between supramolecular chemistry and biochemistry. Many of these receptors therefore share properties characteristic of both these fields. They can be easily modified by using rational design or combinatorial methods, for example. In addition, binding properties are sensitively dependent on receptor conformation, which is in turn controlled by the sequence of the (amino acid) subunits. In this chapter, successful work in the area of synthetic peptide‐derived receptors is presented to illustrate general design principles and the properties that can be achieved. To this end, the receptors are divided into four types: cyclic peptides and cyclic pseudopeptides, conformationally constrained cyclic peptides containing rigid nonnatural subunits, linear peptides with natural and/or nonnatural subunits, and conjugates of abiotic receptors and peptide‐based subunits. The examples demonstrate that not only are peptide‐derived receptors excellent mimics for natural ligands but in some cases they also possess outstanding binding properties when compared to the other types of synthetic receptors studied in supramolecular chemistry.
Biological Small Molecules as Receptors
Authors: Godoy‐Alcántar Carolina , Yatsimirsky Anatoly K. 
Published: February 2012

Abstract
Structures, recognition, and some relevant physicochemical properties of small biological molecules, as well as their applications in analysis, are described. The following classes of compounds are discussed: biological ionophores, glycopeptide antibiotics, rifamycins, bile acids and their salts, aminoglycosides, cyclic polypeptide (including thiopeptide) antibiotics, and cinchona and bisbenzylisoquinoline alkaloids. In some cases, interaction of antibiotics with their biological targets is also discussed. Generally, in spite of already several successful practical applications of biological small molecules as receptors, studies on their recognition of analytically important compounds are limited and many biomolecules of appropriate structures have never been tested as receptors yet.
Ion‐Pair Receptors
Authors: Dalla Cort Antonella 
Published: February 2012

AbstractThis chapter focuses on the emerging field of supramolecular chemistry concerning ion‐pair recognition. The recent progress in the design of receptors that simultaneously bind both cationic and anionic guests is reported here. The different synthetic strategies adopted to accommodate ion pairs within receptors are discussed, and the advantages in terms of affinity and selectivity that can be obtained by this approach are compared with those of simple ion receptors.