Cryptands and cryptates

Of these terms, the names crown ether, cryptand and cryptate are in general usage. 

Wipff, G. (1992) Molecular Modeling Studies on Molecular Recognition - Crown Ethers, Cryptands and Cryptates - from Static Models in Vacuo to Dynamic Models in Solution, J. Coord. Chem. 27, 7-37 and chapter in this volume. 

Cryptands and Cryptates Cages Made to Measure for s-Block Metals. 139... 

Due to its facility yielding abundant data, NMR is the most often used technique to reveal structural information on cryptands and cryptates. NMR determination structure is straightforward, but does not give as much structural detail as X-ray crystallography. 

Soft ionization MS techniques, such as matrix-assisted laser desorption ionization (MALDI), ESI, and fast atom bombardment (EAB), allow cryptand and cryptate molecular ions to be seen. The choice of matrix is important because many of the cryptands easily bind alkali metals, even displacing a cryptate s guest species. 

T is the temperature, at which the NMR-signals coalesce due to line broadening. The exchange rate (k) was determined from the associated frequency distances of the cryptand and cryptate resonances. The rate k refers to the coalescence temperature. The data favour an exchange mechanism of the type. 

A D a-symmetric hydrogen-bonded capsule 420 with a cavity volume of approximately 950 is reported in [77] to encapsulate suitable cryptand and cryptate guests (including their ionic associates with SCN and CN" anions) having the volumes of 390-420 thus forming the host-homoguest and host-heteroguest 1 1 and 1 1 1 Matreshka complex-in-complex assemblies by Scheme 3.80. 

Podates AcycHc analogues of crown ethers /coronands and cryptands (podands, eg, (11) (30) are also capable of forming inclusion compounds (podates) with cations and uncharged organic molecules, the latter being endowed with a hydrogen bond fiinctionahty. Podates normally are less stable than coronates and cryptates but have favorable kinetics. 

Complexes Tlie term cryptate is now accepted to mean the complex formed between a cryptand and a substrate. Tlie corresponding complex with a coronand would be a coronate, a term suggested some years ago by the same authors . Presumably, a complex between a podand and some substrate would be a podate . 

An additional nuance in the nomenclature of these compounds concerns their complexes. The open-chained compounds are often referred to as podands and their complexes as podates. The cyclic ethers may also be called coronands and their complexes are therefore coronates. Complexed cryptands are cryptates. The even more complicated structures known as spherands, cavitands, or carcerands are called spherates, cavitates, or carcerates, respectively, when complexed. The combination of a macrocycle (crown ether or coro-nand) and a sidechain (podand) is typically called a lariat ether. 

Menif, R. Reibenspies, J. Martell, A. E. Synthesis, protonation constants, and copper(II) and cobalt(II) binding constants of a new octaaza macrobicylic cryptand (MX)3crystal structures of the cryptand and of the carbonato-bridged dinuclear copper(II) cryptate, Inorg. Chem. 1991, 30, 3446-3454. 

Dietrich, B. Lehn, J.-M. Guilhem, J. Pascard, C. Anion receptor molecules synthesis of an octaaza-cryptand and structure of its fluoride cryptate, Tetrahedron Lett. 1989, 30, 4125-4128. 

Laser flash photolysis has also been used to study the photophysics and photochemistry of metallocene-containing cryptands and their complexes with rare earth eations [69]. The metallocene moiety was shown to act as an efficient centre for the radiationless deactivation of the lanthanide excited state. Detailed time-resolved studies permitted the characterisation of the coordination chemistry about Dy " within the cryptate and showed, once again, that the functions within the host cryptand primarily responsible for coordination of the guest cation were the amide carbonyl groups. 

Polyaza macrobicyclic cryptands synthesis, crystal structures of a cyclophane type macrobicyclic cryptand and of its dinuclear copper(I) cryptate, and anion binding features, J. Jazwinski, J.-M. Lehn, D. Lilienbaum, R. Ziessel, J. Guilhem and... 

---