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2016 | Buch

The Encapsulation Phenomenon

Synthesis, Reactivity and Applications of Caged Ions and Molecules

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This fundamental book presents the most comprehensive summary of the current state of the art in the chemistry of cage compounds. It introduces different ways of how ions and molecules can be encapsulated by three-dimensional caging ligands to form molecular and polymeric species: covalent, supramolecular, and coordination capsules. The authors introduce their classification, reactivity, and selected practical applications. Because encapsulation can isolate caged ions and molecules from external factors, the encapsulated species can exhibit unique physical and chemical properties. The resulting specific reactivity and selectivity can open up a range of applications, including chemical separation, recognition, chiral separation, catalysis, applications as sensors or probes, as molecular or supramolecular devices, or molecular carriers (cargo).A particularly strong emphasis in this book is on the summary and review of the synthesis of various types of cage compounds. Readers will find over 850 literature references summarized and clearly represented in over 600 schemes and illustrations. The book is structured by the types of caging ligands (covalent, supramolecular, or coordination capsules). The authors further arranged the chapters by ligand classes and types of encapsulated species (neutral molecules, anions, or cations). Readers will hence find an exhaustive reference resource and summary of the current state of research into encapsulated species, nowadays almost a separated realm of modern chemistry.

Inhaltsverzeichnis

Frontmatter
1. General Considerations
Abstract
Before going into any details, we should identify molecular and supramolecular compounds that are considered cage complexes with encapsulated species (organic or inorganic anions, cations, and neutral molecules). The main criteria for the formation of such a complex are (i) 3D cavity in a caging ligand (capsule, cage framework) and (ii) inclusion (encapsulation) of chemical species within this cavity via coordination (donor–acceptor) bonds or supramolecular interactions (hydrogen bonds, electrostatic (Coulombic) and dipole–dipole interactions, etc).
Yan Voloshin, Irina Belaya, Roland Krämer
2. Encapsulation by Covalent Capsules
Abstract
Overwhelming majority of covalent capsules are neutral compounds that have been prepared using classical organic reactions and synthetic approaches from classical [1–9] and modern [10–12] macrocyclic chemistry. Those are based on “bottom-to-up” principle, such as imine condensations (in many cases, followed by reduction of the cage Schiff bases formed to their amine analogs) and condensations in high-dilution conditions of diamine- or dihydroxyl-containing components (mostly the reactive macrocyclic precursors) with terminal dihalogenoalkanes or chloroanhydrides of suitable dicarboxylic acids. In contrast to supramolecular and coordination capsules (Chaps. 3 and 4), the template effect of encapsulated species is less pronounced, but in several cases, templation of these reactions by alkali or alkali-earth metal cations, neutral guests, and caged anions is reported.
Yan Voloshin, Irina Belaya, Roland Krämer
3. Encapsulation by Hydrogen-Bonded and Other Supramolecular Capsules
Abstract
Most of the supramolecular capsules are neutral compounds that are self-assembled by hydrogen bonding between complementary organic ligand syntones to form unimolecular, dimeric, tetrameric, or hexameric hydrogen-bonded cage frameworks. In several cases, electrostatic (Coulombic) and stacking interactions have been used for self-assembly of the corresponding supramolecular capsules. The template effect of encapsulated species (mostly of neutral guests or co-guests) has been observed in many systems. Moreover, co-encapsulation of various guests caused the specific types of stereoisomerism (so-called social isomerism and isomeric (diastereomeric) constellation, see Sect. 3.1.1) to appear, which are characteristic of these “soft” capsules. Another important feature of these capsules is the so-called Rebek’s rule postulating the encapsulation to proceed efficiently at the packing coefficient of the guest of approximately 55 % (see below).
Yan Voloshin, Irina Belaya, Roland Krämer
4. Encapsulation by Coordination Capsules
Abstract
Coordination capsules are the species that typically self-assembled from ligand syntones with appropriate terminal donor groups and the coordinate transition and non-transition metal ions or their labile and coordination-unsaturated complexes. The resulting cage frameworks can be divided into three main structural types: (i) tetrahedral capsules and their analogs, such as cuboid frameworks, containing 4n end-capping metal ion, (ii) octahedral and TP capsules and their analogs with 6n end-capping metal ions, and (iii) coordination capsules with bridging (cross-linking) metal ions. Most of these caging ligands are positively or negatively charged (cationic and anionic coordination capsules, respectively); templation of their formation by anionic or cationic guests of appropriate size and shape has been observed in many cases.
Yan Voloshin, Irina Belaya, Roland Krämer
5. Reactivity of Encapsulated Species
Abstract
Unusual chemical and photochemical reactivity (or, in contrast, incredible stability) of encapsulated species and the unexpected products of such reactions within the confined cavities of molecular capsules have been observed in many cases. This can be explained by steric restrictions due to relative rigidity of covalent and coordination capsules, by isolation of these guests from external factors such as solvent effects, and by relatively strong supramolecular host–guest interactions.
Yan Voloshin, Irina Belaya, Roland Krämer
6. Practical Applications of Molecular Capsules and Their Cage Complexes
Abstract
A cascade of dicobalt-containing capsule shown in Scheme 6.1 has been proposed [1] as an oxygen carrier: spectrophotometrical studies of its oxygenation, deoxygenation, and degradation showed to be a suitable encapsulating reagent for separation of O2 from gaseous mixtures.
Yan Voloshin, Irina Belaya, Roland Krämer
Backmatter
Metadaten
Titel
The Encapsulation Phenomenon
verfasst von
Yan Voloshin
Irina Belaya
Roland Krämer
Copyright-Jahr
2016
Electronic ISBN
978-3-319-27738-7
Print ISBN
978-3-319-27737-0
DOI
https://doi.org/10.1007/978-3-319-27738-7

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