bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a Fractional Q-Switched Ruby Laser for Treatment of Facial Lentigines
Authors: Chipps Lisa K. , Diehl Joseph W. , Schouest Jonathan M. , Moy Ronald L.
Published: February 2012

Introduction:

Fractional laser technology is associated with decreased posttreatment morbidity but has not been applied to Q-switched ruby lasers (694 nm). Standard Q-switched ruby lasers have been used effectively for the treatment of pigmented lesions but require postoperative wound care and significant recovery time. The objective is to report on the suitability of a new fractional handpiece for a Q-switched ruby laser for the treatment of facial lentigines.

Materials and Methods:

Five patients with facial lentigines were treated with or without topical anesthetic with a fractional Q-switched ruby laser at a fluence that caused tissue whitening.

Results:

Patients were treated 1 to 2 times. All patients experienced clinical improvement in hyperpigmentation with minimal posttreatment erythema and crusting.

Conclusions:

The fractional Q-switched ruby laser is an ideal treatment for facial lentigines, causing clinical improvement with minimal posttreatment morbidity.
Temperature Monitoring during Laser-Assisted Liposculpture in Males
Authors: Burke Robert H.
Published: February 2012

Skin and subdermal temperatures were compared before and after laser-assisted liposculpture treatment in males. Subdermal temperatures were recorded using an autoclavable temperature probe specifically developed for internal temperature monitoring directly at the point of laser energy output. There were 60 temperature recordings made in 15 treatment areas. These included before and after readings of skin and subdermal temperatures in each treatment area. The endpoint of tissue resistance and ease of cannula insertion was used as a guide for laser energy application in this study rather than a specific temperature endpoint. The application of laser energy to the subdermal tissues resulted in temperature elevation of both the skin and subdermal regions. Variable temperature elevations occurred in each region with differences that were not predictable. Maximum temperature increases recorded at the skin surface and in the subdermal region were 11.8°C. and 15.0°C, respectively. No complications were encountered. Statistical analysis using standard paired tests showed the temperature differences to be significant.
Use of Urinary Bladder Matrix, a Bioactive, Acellular Scaffold, in Transplant Donor Scars and Androgenetic Alopecia: Initial Clinical Experience
Authors: Hitzig Gary
Published: February 2012

Introduction:

Emerging regenerative medicine technologies have yet to be utilized in hair restoration surgery. Urinary bladder extracellular matrix (UBM) has shown promise in a wide variety of applications, inducing site-specific remodeling of injured tissue. This case series describes one clinician's experience in the first use of this regenerative material in hair restoration surgery.

Materials and Methods:

Twenty subjects underwent one of several protocols: (1) Treatment of 3-mm biopsies within donor site scars with UBM versus untreated controls, (2) Removal of a strip of donor site scar tissue and treatment of the site with UBM, (3) Soaking of occipital hair follicle grafts in a solution of UBM, or (4) Soaking of beard or temple hair follicle grafts.

Results:

At 6 months, hair was observed in biopsy sites that contained UBM, including donor scar areas that would not normally regrow hair, in contrast to the control biopsy sites. Similar results were observed for the strip excisions. UBM-soaked occipital, beard, and temple hair grafts consistently yielded higher than expected numbers of hair follicles.

Conclusions:

These cases provide anecdotal support for the hypothesized benefits of UBM regenerative technology in restoration therapy for men and women with androgenetic hair loss.
Direct Knee Lift following Bariatric Surgery
Authors: Cuzalina Angelo , Copty Tarek
Published: February 2012

We are presenting a case report of a direct anterior knee-lift as an adjunct to thigh-lift surgery on a patient with massive weight loss. Our literature review resulted in numerous thigh-lifting articles, but no success in finding an article that discusses skin laxity directly over the knee or any specific procedure to correct skin laxity in this region. We have tried various inverted T-type incisions at the inferior end of an extended vertical thigh-lift but have had less than ideal results because this incision wraps around the knee. Therefore, during a recent live American Academy of Cosmetic Surgery surgical workshop on post bariatric surgery, a patient who desired maximum lift of the entire thigh, as well as the skin above the knee, volunteered for a direct anterior knee-lift to attempt significant improvement of her cutis laxis just above her knees.
Supramolecular Interactions
Authors: Varshey Dushyant B. , Sander John R. G. , Friščić Tomislav , MacGillivray Leonard R.
Published: February 2012

This chapter provides an overview of noncovalent interactions in the field of supramolecular chemistry. The use of noncovalent forces to form supramolecular structures is documented. Supramolecular interactions can be both directional and nondirectional and can enable chemists to develop discrete assemblies and networks of molecules and/or ions with prescribed properties and functions. Concepts of host‐guest chemistry, molecular recognition, and self‐assembly emerge from an understanding of how supramolecular interactions control assembly processes. Examples that highlight the utility of employing supramolecular interactions to form functional structures and materials are given.
Solvation Effects in Supramolecular Recognition
Authors: Rekharsky Mikhail , Inoue Yoshihisa
Published: February 2012

Solvent, or solvation, effect arises from various non–covalent weak interactions of solvent molecules with supramolecular host, guest, and complex, and the supramolecular host‐guest association process can be significantly affected or even totally altered by solvation. The solvent effect is a critical function of the host, guest, and solvent involved, and therefore neutral hydrophobic organic guests and hydrophilic metal cations show entirely different solvent dependencies upon complexation. Apparently complicated solvation/desolvation behavior of diverse supramolecular host‐guest systems can be rationally understood through the analysis by the Grunwald theory of the compensatory enthalpy–entropy relationship observed for a large set of experimental complexation thermodynamic parameters. The enthalpy–entropy compensation analysis is applicable not only to supramolecular host–guest interactions but also to biological assembling processes as a general tool for globally understanding the solvation behavior in chemistry and biology.
Competition Experiments
Authors: You Lei , Anslyn Eric V.
Published: February 2012

Competition assays, particularly indicator displacement assays (IDAs), are now a popular approach for supramolecular detection and sensing. Contrary to the traditional indicator–spacer–receptor approach, an IDA is based on guest competition between an analyte and an indicator for binding of the receptor (host). As a result, synthesis to incorporate the indicator is avoided in the creation of an IDA, and the selection of indicators can be used to impact the assay. IDAs have been utilized to detect and sense various kinds of analytes, including anions, cations, and neutral molecules. Moreover, both synthetic and biological hosts have been explored in IDAs, thereby expanding the scope of IDAs. Besides utilization in individual analyte sensing, IDAs are amenable to pattern‐recognition‐based differential sensing. Recently, IDAs have been explored to discriminate structurally similar analytes, generating diagnostic fingerprints for complex mixtures. Enantioselective indicator displacement assays (eIDAs) have also been explored and have great potential for application in asymmetric catalyst discovery. IDAs with different detection methods, different kinds of guests, and different kinds of hosts are discussed in this chapter.
Chirality
Authors: Keene F. Richard
Published: February 2012

This chapter addresses stereochemical consequences in supramolecular chemistry in terms of both the components and the ultimate assembly. In particular, it discusses the important (and sometimes elusive) concept of chirality in supramolecular aggregates—its origin, the practical aspects of separation of chiral forms and their identification and quantification. The examples taken are predominantly from metallosupramolecular systems: the deliberate construction of chiral oligonuclear assemblies as well as the principles that guide the phenomenon of self‐assembly of the components, which give rise to (inter alia) helicates, catenanes, knots, and polygons—many of which are inherently chiral. Because of the possible variations of structural motifs—in terms of both metal centers and their geometries, and of ligand types—metallosupramolecular chemistry can realize an extraordinary range of assemblies, which are not only elegant in design and varied in nature but also provide the potential for the development of new materials in nanoscience.
Luminescent Spectroscopy in Supramolecular Chemistry
Authors: Erbas‐Cakmak Sundus , Guliyev Ruslan , Akkaya Engin U.
Published: February 2012

Luminescence phenomena are highly sensitive to microenvironment. Consequently, supramolecular processes may induce remarkable changes in the emission character of the interacting molecular species. These changes could be useful in designing functional luminophores, such as luminescent molecular sensors for ions and neutral molecules, or just for probing supramolecular interactions. In this chapter, the photophysical processes, such as internal charge transfer (ICT), excitation energy transfer, and photoinduced electron transfer (PeT), are presented, since they are modulated by supramolecular interactions.
Uses of Differential Sensing and Arrays in Chemical Analysis
Authors: Adams Michelle M. , Joyce Leo A. , Anslyn Eric V.
Published: February 2012

The aim of this chapter is to introduce the reader to differential sensing, to detail the history of the electronic nose and tongue that led to the development of differential sensing, and to provide a spectrum of examples where differential sensing has been employed to classify and/or detect single analytes and mixtures of analytes. Using the information presented in this chapter, we hope to provide a solid background for the reader so that the differential sensing approach can be extrapolated to any desired chemical sensing purpose.
Transmission Electron Microscopy (
TEM
)
Authors: Kikuchi Jun‐ichi , Yasuhara Kazuma
Published: February 2012

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

Among 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

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

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

Langmuir (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

This 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

Brewster 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

Over 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

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

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

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

The 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

Crown 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

Azacycloalkanes 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

Supramolecular 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

The 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

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

Nature 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

Synthetic 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

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.
Receptors for Zwitterionic Species
Authors: Luis Santiago V. , Alfonso Ignacio , Galindo Francisco
Published: February 2012

The recent developments in the design of receptors for zwitterionic species are reviewed in this chapter. Different types of receptors are compiled, attending to their structural properties. The difficulties in obtaining efficient and selective ditopic hosts for zwitterionic guest are discussed.
Ion‐Pair Receptors
Authors: Dalla Cort Antonella
Published: February 2012

This 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.
Boronic Acid‐Based Receptors
Authors: Fossey John S. , James Tony D.
Published: February 2012

The ability to monitor analytes within physiological, environmental, and industrial scenarios is of prime importance. As recognition events occur on a molecular level, gathering and processing the information poses a fundamental challenge. Therefore, robust chemical molecular sensors, known as “chemosensors,” with the capacity to detect chosen molecules selectively and signal this presence continue to attract considerable attention. Real‐time monitoring of saccharides is of particular interest, such as
D
‐glucose in blood. Toward that end, the covalent coupling interaction between boronic acids and saccharides has been exploited with some success to monitor the presence of such saccharides. The boronic acid–and Lewis acid base interaction is also suitable for the capture and recognition of anions. Anions are involved in fundamental processes in all living things. Our aim as synthetic chemists is to mimic nature s level of sophistication in designing and producing chemosensors capable of determining the concentration of a target analyte (i.e., saccharides and anions) in any medium.
Template Strategies in Self‐Assembly
Authors: Amabilino David B.
Published: February 2012

The use of templates in supramolecular science is one of the most universally applicable concepts, from the synthesis of large organic molecules to the preparation of nanomaterials. The review traces the uses of different types of template from the pioneering work with metal cations, the more recent anion‐directed syntheses, to the use of molecular and macromolecular templates. The concepts developed initially from solution‐based synthesis can be applied to the preparation of surface‐based supramolecular systems, which are so interesting as nanomaterials, and the preparation of macroscopic systems, which have a variety of applications, including porous materials of both organic and inorganic characters for sequestering and separation. It is demonstrated that supramolecular templates are essential for the preparation of these materials and many others and that a wide range of opportunities lie untapped still in the use of bottom‐up and top‐down techniques guided by the same underlying concepts that have led to such an advance in template‐directed synthesis.
Self‐Assembly of Coordination Compounds: Design Principles
Authors: Alvarez Santiago , Ruiz Eliseo
Published: February 2012

The terminology and basic concepts of coordination chemistry are presented, in view of their potential application in the design of supramolecular systems based on transition metals. We describe the main features of the metal ions, mostly in relation to atomic size and oxidation state, and those of the ligands, such as denticity, topology, and flexibility. Polyhedra as stereochemical descriptors and the relationships of nested polyhedra are analyzed. The dependence of stereochemical preferences of the most common six‐ and four‐coordinate metal centers on the electron configuration is systematically studied, and a brief description of the common stereochemistries for other coordination numbers is presented. Finally, basic criteria for understanding the choice of coordination number by a particular combination of metal and ligands are discussed, and ways to describe the stereochemistries of coordination centers with ill‐defined coordination numbers are proposed.
Self‐Assembly of Coordination Chains and Helices
Authors: Imaz Inhar , Maspoch Daniel
Published: February 2012

When Robson introduced for the first time the design of coordination polymers (CPs) in 1989, nobody could imagine that this concept would open a fascinating new world in the field of chemistry, materials science, and nanotechnology. Although based on the very simple concept that “multifunctional organic molecules can connect metal ions through the space,” this synthetic strategy has become an invaluable source of new materials with exceptional structures, properties and applications. In fact, since 1989, the progress made on the design, synthesis, and characterization of CPs as well as on the study of their properties and applications has been spectacular. Today, chemists seem to do magic when they use coordination chemistry to connect metal ions through bridging organic ligands, allowing the continuous discovery of novel CPs. In addition, the coordination chemistry has not walked alone! The development of CPs has also been closely accompanied by the rapid evolution and sophistication of the supramolecular chemistry and the crystal engineering. Today, a CP cannot be considered as an isolated object. Their structures, shapes, and properties depend not only on the metal‐organic association but also on the supramolecular interaction, such as hydrogen bonds and π–π interactions, existing between each coordination entity. Among the highly diverse family of CPs, the one‐dimensional (1D) systems represent the simplest and undoubtedly one of the most abundant topologies in the literature. The simplicity of these topologies confers to these systems high degrees of freedom, and consequently, a large panel of interchains interactions and self‐association leading to original architectures with a variety of properties. Thus, in the last years, a large number of novel materials, such as chains and helices, based on the self‐assembly of 1D CPs have been reported. In this section, we attempt to give not an exhaustive but a representative overview of self‐assembled coordination chains and helices.
Self‐Assembly of Coordination Cages and Spheres
Authors: Sato Sota , Murase Takashi , Fujita Makoto
Published: February 2012

Self‐assembly employing coordination bonds provides symmetric, huge, hollow cages and spheres that are not attained by conventional synthetic methodologies based on covalent bonds. The self‐assembled architectures are not merely aesthetically attractive; they offer fruitful functions, which otherwise cannot be realized in normal bulk conditions. For example, self‐assembled host cages serve as nanometer‐sized molecular flasks where cavity‐directed chemical transformations are performed and as nanometer‐sized sealed chamber where reactive species are stabilized. The shell frameworks of hollow spherical complexes are versatile scaffolds for precisely accumulating functional groups outside/inside the spheres where the functional groups work cooperatively and thus new functions emerge. Therefore, the chemistry of coordination cages and spheres will further expand the skeleton toward much more large, complex systems; and the implanted functions through elaborated molecular designs will afford creative innovations based on the well‐defined structures.
Self‐Assembly of Organic Supramolecular Capsules
Authors: Scarso Alessandro , Borsato Giuseppe
Published: February 2012

The present contribution is aimed at illustrating to the reader the state of the art on the construction of artificial, finite supramolecular assemblies characterized in solution by capsular shape held together by means of weak intermolecular noncovalent forces in solution, except metal‐ligand coordination. These supramolecular assemblies provide cavities of correct size and shape where molecules of guests present in solution can be hosted if the available space is appropriately filled. Guests within the cavity are held for lifetimes ranging from milliseconds to hours, depending on the number and quality of weak intermolecular forces and the number of subunits that compose the capsule.

The in–out process of exchange of guests influences their behavior profoundly, enabling a series of applications spanning from molecular recognition of one up to several guests at a time with creation of new forms of isomerism derived by guest–guest interactions to supramolecular catalysis, which is the ultimate goal of such kind of assemblies.

A further intriguing aspect of self‐assembled capsules is chirality that can be implemented in the subunits, that forms the capsule, or that can be the result of a particular arrangement of achiral units. In the latter case, the presence of strong attractive forces between the subunits enables to template the formation of enantiomerically enriched capsules with enantiopure guests based on achiral units via the chiral memory effect.
Self‐Assembly of Supramolecular Wires
Authors: Weiss Jean , Koepf Matthieu , Wytko Jennifer A.
Published: February 2012

This review focuses on the strategies available for the construction of persistent linear species from monomers. The scope is mostly restricted to wires, but also includes some selected examples illustrating the fast developing area of fibers and tubular structures, given that their linearity is governed by supramolecular interactions. Strategies are primarily limited to those that are based on noncovalent assembly obtained by iterative interactions that range from coordination bonds to π‐interactions and hydrogen bonding. Each approach is illustrated by a selection of either pioneering or recent examples. The use of supramolecular templates to assemble molecules into linear wires, whose structures are sometimes covalently locked, is also briefly presented.
Organic Foldamers and Helices
Authors: Huc Ivan , Jiang Hua
Published: February 2012

This chapter gives an overview of the rapidly developing field of foldamers defined as artificial folded molecular architectures. Research in the field of synthetic foldamers aims at designing, preparing, and characterizing nonnatural oligomers that are able to adopt well‐defined conformations often inspired by, but not necessarily identical to, those of biopolymers. Hence, foldamers offer hope to rival their natural counterparts in terms of their functions and applications. Folding at the molecular level is a self‐process that is governed by a variety of internal and external parameters, including monomer structure, linkage orientation, local or remote intramolecular interactions, solvent effects, aggregation, and host‐guest complexation. Foldamers may form diverse secondary structures, in particular, helices, tertiary and even quaternary structures, and some
super
structures such as nanofibers. They show high potential as scaffolds for molecular recognition and catalysis; they also show potential for biological applications, though this latter aspect is not detailed here.
Self‐Assembly of Nucleic Acids
Authors: Carneiro Karina M. M. , Lo Pik Kwan , Sleiman Hanadi F.
Published: February 2012

DNA has emerged as a powerful building block for the construction of supramolecular materials, because of its molecular recognition specificity, programmability through sequence selection, ease of functionalization, an array of enzyme‐assisted modifications, and automated synthesis. This molecule has been used to create a variety of constructs, ranging from extended materials, such as two‐dimensional (2D) lattices and networks and one‐dimensional (1D) fibers and nanotubes, to controlled and discrete three‐dimensional (3D) nanostructures, such as polygons and cages, and it has also been used to compose bulk materials such as hydrogels and crystals. This review focuses on the different approaches in DNA nanotechnology, the resulting 2D‐ and 3D‐DNA nanostructures, and their emerging applications in biology and materials science.
Peptide Self‐Assembly
Authors: Cavalli Silvia , Robson Marsden Hana , Albericio Fernando , Kros Alexander
Published: February 2012

The formation of well‐ordered nanostructures by a process of self‐association in aqueous media or at interfaces represents the core of modern nanotechnology. Processes of molecular recognition and self‐assembly direct the way in which relatively simple building blocks recognize each other, associate, and form ordered one‐, two‐, and three‐dimensional structures with a wide range of applications in nanoscience. The manner in which molecules self‐assemble and their interaction energies, shapes, and ultimate functions can be programmed at the molecular level by a careful and rational design. Peptides are among the most powerful building blocks available for constructing “smart” well‐ordered nanostructures in a “bottom‐up” approach, as they possess the biocompatibility and chemical diversity that are commonly found in proteins, but they are much more stable and robust and can be readily synthesized on a large scale. In this chapter, the main categories of peptide amphiphiles are discussed for their ability to spontaneously associate to form a variety of nanostructures (e.g., tubes, spheres, fibrils, tapes, and hydrogels at the nanometerscale) and some key features of this processes are outlined by describing a selection of relevant published works.
Photoprocesses of Relevance to Supramolecular Chemistry
Authors: Spänig Fabian , Haefele Alexandre , Castellano Felix N.
Published: February 2012

This contribution focuses exclusively on the application of photophysical methods that can be applied toward signaling a variety of supramolecular chemistry events using examples from the recent literature. It is not intended to be comprehensive but rather to illustrate how specific photo techniques can be used to glean insight into supramolecular phenomena. Given the widespread availability of fluorescence technologies worldwide, the current study reflects its dominant usage in supramolecular chemistry while exemplifying a range of techniques within the discipline. Nondestructive transient absorption spectroscopy is also discussed in light of how it can be utilized in conjunction with supramolecular photochemistry, specifically in the identification of intermediates that cannot be interrogated otherwise. Relevant aspects of molecular photochemistry and photophysics are briefly introduced below and developed further where necessary. Given the number of comprehensive reviews in the general area of supramolecular photochemistry and photophysics, we attempt to highlight only recent examples using a conceptual framework most relevant to the authors of this contribution, largely involving combinations of metal‐ and organic‐based chromophores.