Cryptand

About: Cryptand is a research topic. Over the lifetime, 1897 publications have been published within this topic receiving 45534 citations. The topic is also known as: cryptands.

Anion Recognition and Sensing: The State of the Art and Future Perspectives

Abstract: Anion recognition chemistry has grown from its beginnings in the late 1960s with positively charged ammonium cryptand receptors for halide binding to, at the end of the millennium, a plethora of charged and neutral, cyclic and acyclic, inorganic and organic supramolecular host systems for the selective complexation, detection, and separation of anionic guest species. Solvation effects and pH values have been shown to play crucial roles in the overall anion recognition process. More recent developments include exciting advances in anion-templated syntheses and directed self-assembly, ion-pair recognition, and the function of anions in supramolecular catalysis.

Cyclodextrins and their uses: a review

Abstract: Cyclodextrins are a family of cyclic oligosaccharides composed of α-(1,4) linked glucopyranose subunits. Cyclodextrins are useful molecular chelating agents. They possess a cage-like supramolecular structure, which is the same as the structures formed from cryptands, calixarenes, cyclophanes, spherands and crown ethers. These compounds having supramolecular structures carry out chemical reactions that involve intramolecular interactions where covalent bonds are not formed between interacting molecules, ions or radicals. The majority of all these reactions are of ‘host–guest’ type. Compared to all the supramolecular hosts mentioned above, cyclodextrins are most important. Because of their inclusion complex forming capability, the properties of the materials with which they complex can be modified significantly. As a result of molecular complexation phenomena CDs are widely used in many industrial products, technologies and analytical methods. The negligible cytotoxic effects of CDs are an important attribute in applications such as rug carrier, food and flavours, cosmetics, packing, textiles, separation processes, environment protection, fermentation and catalysis.

Design principles of fluorescent molecular sensors for cation recognition

Abstract: The main classes of fluorescent molecular sensors for cation recognition are presented: they differ by the nature of the cation-controlled photoinduced processes: photoinduced electron transfer, photoinduced charge transfer, excimer formation or disappearance. In each class, distinction is made according to the structure of the complexing moiety: chelators, podands, coronands (crown ethers), cryptands, calixarenes. The most representative examples are presented in each subclass with special attention given to selectivity.

Coordination Chemistry of Macrocyclic Compounds

Abstract: 1. General Introduction.- 1. Introductory Comments.- 2. General Comments.- 2.1. Definition of a Macrocyclic Compound.- 2.2. Historical Background.- 2.3. Abbreviations of Macrocyclic Compounds.- 2.4. Units.- 2.5. Chapter Layout.- References.- 2. Synthesis of Macrocyclic Complexes.- 1. Introduction.- 2. Tridentate Ligands.- 3. Tetradentate Ligands.- 3.1. N4 Donor Atoms.- 3.2. N2O2 Donor Atoms.- 3.3. N2S2 Donor Atoms.- 3.4. S4 Donor Atoms.- 3.5. P4 and P2S2 Donor Atoms.- 4. Pentadentate Ligands.- 5. Sexadentate Ligands.- 6. Binucleating Ligands.- 7. Clathrochelates.- 8. Conclusions.- References.- 3. Thermodynamics and Kinetics of Cation-Macrocycle Interaction.- 1. Introduction.- 2. Parameters Determining Cation Selectivity and Complex Stability.- 2.1. Relative Sizes of Cation and Ligand Cavity.- 2.2. Arrangement of Ligand Binding Sites.- 2.3. Type and Charge of Cation.- 2.4. Type of Donor Atom.- 2.5. Number of Donor Atoms.- 2.6. Substitution on the Macrocyclic Ring.- 2.7. Solvent.- 3. Macrocyclic Effect.- 3.1. Tetramines.- 3.2. Cyclic Polyethers.- 3.3. Solvation Effects.- 3.4. Mixed Donor Groups.- 3.5. Multiple Juxtapositional Fixedness.- 3.6. Cryptate Effect.- 3.7. Summary.- 4. Table of Thermodynamic Data.- 5. Kinetics.- 5.1. Antibiotic Macrocycles.- 5.2. Cyclic Polyethers.- 5.3. Macrobicyclic Ligands.- References.- 4. Structural Aspects.- 1. Introduction.- 1.1. Scope and Organization.- 1.2. Order of Tabulation.- 2. Class 1: Cyclic Amines-Saturated Polyaza Macrocycles.- 2.1. Introduction.- 2.2. Configurations and Conformations of Coordination Cyclic Tetramines.- 2.3. Metal-Ion-Nitrogen Distances.- 2.4. Substituents on the Macrocycle.- 2.5. Chelate Angles.- 2.6. Listing of Structures of Compounds of Cyclic Amines.- 3. Class 2: Cyclic Imines and Cyclic Amine-Imines (Unsaturated Polyaza Macrocycles with all Nitrogen Atoms Coordinated).- 3.1. Discussion of Structures.- 3.2. Conformation of Macrocycles.- 3.3. Substituents on the Macrocycle.- 3.4. Metal Ion-Nitrogen Distances.- 3.5. Listing of Reported Structures of Cyclic Imine and Cyclic Amine-Imine Compounds.- 4. Class 3: Macrocycles Including a 2,6-Pyridyl Group.- 4.1. Discussion of Structures.- 4.2. Listing of Reported Structures of Compounds of Macrocycles Including a 2,6-Pyridyl Group.- 5. Class 4: Tetraazamacrocycles with 2-Imino(or 2-amido)-benzaldimine Chelate Rings.- 5.1. Discussion of Structures.- 5.2. Listing of Structures of Tetraazamacrocycles with l-Imino(or l-amido)-2-aldiminobenzene Chelate Rings (o-Iminobenzaldimine and o-Amidobenzaldimine Derivatives).- 6. Class 5: Dibenzo[b,i]-l,4,8,11-tetraazacyclotetradec-2,4,6,9,11-hexaenato(2-) Compounds.- 6.1. Discussion of Structures.- 6.2. Listing of Structures of Bzo2[14]hexaenato(2-)N4 Compounds.- 7. Class 6: Cyclic Hydrazines and Hydrazones.- 7.1. Discussion of Structures.- 7.2. Listing of Structures of Cyclic Hydrazine and Hydrazone Compounds.- 8. Class 7: Cyclic Tetraethers and Tetrathiaethers (Tetraoxo- and Tetrathiamacrocycles).- 8.1. Discussion of Structures.- 8.2. Listing of Structures of Tetraoxa- and Tetrathiamacrocycles.- 9. Class 8: Macrocycles with More Than One Type of Heteroatom.- 9.1. Discussion of Structures.- 9.2. Listing of Structures of Compounds.- 10. Class 9: Binucleating Macrocycles.- 10.1. Discussion of Structures.- 10.2. Listing of Structures of Binucleating Macrocycles.- 11. Class 10: Cyclic Phosphazenes.- 11.1. Discussion of Structures.- 11.2. Listing of Structures of Cyclic Phosphazene Compounds.- 12. Class 11: Clathrochelates.- 12.1. Discussion of Structures.- 12.2. Listing of Structures of Clathrochelate Compounds.- 13. Conclusion.- References.- 5. Ligand Field Spectra and Magnetic Properties of Synthetic Macrocyclic Complexes.- 1. Introduction.- 2. Nickel Complexes.- 2.1. Nickel(II) Macrocyclic Complexes.- 2.2. Macrocyclic Complexes of Nickel(I) and Nickel(III).- 3. Copper Complexes.- 3.1. Macrocyclic Copper(II) Complexes.- 3.2. Magnetic Interactions in Binuclear Macrocyclic Copper Complexes.- 3.3. Macrocyclic Complexes of Copper(I) and Copper(III).- 4. Cobalt Complexes.- 4.1. Cobalt(II) Macrocyclic Complexes.- 4.2. Macrocyclic Cobalt(III) Complexes.- 4.3. Cobalt(I) Macrocyclic Complexes.- 5. Iron Complexes.- 5.1. Low-Spin (S = 0) Iron(II) Macrocycles.- 5.2. High-Spin (S = 2) Iron(II) Macrocycles.- 5.3. Intermediate Spin (S = 1) Iron(II) Macrocycles.- 5.4. Low-Spin (S = 1/2) Iron(III) Macrocycles.- 5.5. High-Spin (5 = 5/2) and Intermediate-Spin (S = 3/2) Iron(III) Macrocycles.- 5.6. Other Iron-Containing Macrocycles.- 6. Manganese Complexes.- 6.1. Macrocyclic Complexes of Manganese(II).- 6.2. Macrocyclic Complexes of Manganese(III).- References.- 6. Chemical Reactivity in Constrained Systems.- 1. Introduction.- 2. Predominantly Metal-Centered Reactions.- 2.1. Coordinative Lability.- 2.2. Oxidation-Reduction Reactions of Simple Stoichiometry.- 3. Reactions of the Macrocyclic Ligands.- 3.1. Oxidative Dehydrogenations..- 3.2. Hydrogenation.- 3.3. Substitutions into the Macrocyclic Ligand.- 3.4. N-Alkylations.- 3.5. Additions.- 4. Reactions Involving Free Radicals, Unusual Oxidation States, and Excited States.- 4.1. Free Radical Reactions.- 4.2. Complexes Containing Metals in Unusual Oxidation States.- 4.3. Photochemical Reactions.- 4.4. Photochemistry of Cobalt-Alkyl Complexes.- References.- 7. Metal Complexes of Phthalocyanines.- 1. Introduction.- 2. Molecular Structure.- 3. Electronic Structure.- 4. Spectral Properties.- 5. Synthesis of New Derivatives.- 6. Redox Reactions.- 7. Aggregation of Complexes.- 8. Chromium Complexes.- 9. Manganese Complexes.- 10. Iron Complexes.- 11. Cobalt Complexes.- 12. Group IV Metal Complexes.- 13. Catalytic Activity.- 14. Comparison of Chemistry of Chromium, Manganese, Iron, and Cobalt Complexes.- References.- 8. Coordination Chemistry of Porphyrins.- 1. Introduction.- 2. Synthesis.- 3. Structure.- 4. Reactions.- 5. Chlorins and Corrins.- References.- 9. Physicochemical Studies of Crown and Cryptate Complexes.- 1. Introduction.- 2. Synthetic Methods.- 2.1. Crown Polyethers.- 2.2. [2]-Cryptands.- 2.3. [3]- and [4]-Cryptands.- 3. Metal-Cation Complexes: Preparation and Structure.- 3.1. Monocyclic Ligands (Crowns).- 3.2. Macropolycyclic Ligands (Cryptands).- 4. Complexes in Solutions: Experimental Techniques.- 4.1. General Considerations.- 4.2. Electrochemical Techniques.- 4.3. Spectroscopic Techniques.- 4.4. Extraction Studies.- 4.5. Calorimetric Techniques.- 4.6. Relaxation Techniques.- 5. Conclusion.- References.- 10. Natural-Product Model Systems.- 1. Introduction.- 1.1. Model Systems-Criticisms, Objectives, and Definitions.- 1.2. Importance of X-Ray Structural Analyses.- 1.3. Evolution of Models.- 2. Macrocyclic Complexes as Models.- 2.1. Macrocyclic Ethers and Thiaethers in Model Systems.- 2.2. Synthetic Tetraazamacrocyclic Systems.- 2.3. Fundamental Studies of Synthetic Macrocyclic Ligand Complexes.- 3. Modeling of Heme Proteins.- 3.1. Studies Involving Metals Other than Iron.- 3.2. Iron(II) Carbon Monoxide Complexes.- 3.3. Dioxygen Complexes.- 3.4. Cytochromes.- 4. Binuclear Systems.- 4.1. Cofacial Diporphyrins.- 4.2. Unsymmetrical Binuclear Systems.- 5. Comments on Vitamin B12 and Related Inorganic Systems.- References.

Crown Ethers and Cryptands

Abstract: Part 1 Introduction to macrocycle chemistry: crown ether precursor work Pedersen's discovery of crown ethers Simmons' in-out bicyclic amines Lehn's cryptands cram and carbanions classes of crown ethers and cryptands naturally occurring relatives of crown ethers nomenclature and its problems toxicity of crown ether compounds. Part 2 Syntheses of crowns, cryptands and their relatives: Pedersen's first crowns the ethylencoxy structural unit the template effect early syntheses of crowns syntheses of crown ethers incorporation of aromatic subunits nitrogen-containing macrocycles crown ethers containing sulfur syntheses of cryptands spherands, cavitands, and carcerands. Part 3 Complexation by crowns and cryptands: the extraction technique homogeneous cation binding constants binding dynamics cation transport complexation of organic cations anions. Part 4 Structural aspects of crowns, cryptands, and their complexes: uncomplexed crown and cryptand ligands simple crown ether complexes of metal cations complexes of cryptands crown ether complexes of other ions and molecules podand complexes. Part 5 Applications of crowns and cryptands: solubilization phenomena cation deactivation anion activation - phase transfer catalysis sensors and switching polymeric crown systems membranes and channels chirality, complexation and enzyme models receptor molecules miscellaneous applications and developments the future of crown ether chemistry. Part 6 Additional reading: books crown ethers cryptands, and polyethers monographs on phase transfer catalysis reviews and articles.