Perfluoro macrocycles

Perfluorinations of many ethers [155], cryptands [156], polyethers [119, 157], including the largest perfluoro-macrocycle [158], perfluoro [60]-crown-20 [123, 159], and the first perfluorinated sugar [160], orthocarbonates [161, 162], ketones [163, 164], esters [124, 165], phosphanes [166] and alkyl halides [167, 168] have been successfully accomplished by the LaMar or aerosol processes (Table 2.4). 

Perfluoro macrocycles are a new development in organic and inorganic chemistry which has occurred in the last five years. The synthesis of perfluoro crown ethers and perfluorocryptands forecast the synthesis of many more perfluoro macrocycles in the next few years. The most surprising development to date with these new very chemically and thermally stable macrocycles has been the findings that they coordinate anions rather than cations and that they are extremely biocompatible materials. Perfluoro macrocycles have the potential for development as a new class of very thermally stable oxygen carriers which reversibly bind oxygen. 

Perfluoro crown ethers are very thermally and chemically stable. The reactions to produce perfluoro macrocycles are all illustrated in Figure 1. There are potential applications of such perfluoro macrocycles in biomedical... 

The high oxygen-carrying capacity of some perfluorocarbons makes them viable as artificial blood components (23), and yet to date the mechanism of oxygen binding to fluoro ethers is not well understood. Thus, it was of considerable interest to probe the ability of perfluoro macrocycles to bind molecular oxygen and other small molecules in the gas phase in order to obtain new information about the binding afflnities of these compounds (11). For these studies, each perfluoro macrocycle was admitted into the source of a triple... 

Each perfluoro macrocycle was ionized to form M then allowed to react with 02to successfully form + O2) adducts (11). lon/molecule reactions involving an acyclic perfluoro ether and hydrogenated crown ethers were also examined to determine whether the cyclic and/or perfluoro nature of the macrocycles played a role in the formation of the (M + O2)" adducts. Neither the perfluoro acyclic analog nor hydrogenated crown ethers reacted with 02to form (M + O2)" adduct ions. This result confirmed that the macrocyclic nature of the perfluoro crown ethers enhanced their ability to bind O2. 

Whether the perfluoro macrocycles are also capable of binding cations is still not certain. Two talented collaborators on this project have not been successful in obtaining cationic complexes with the alkali metals. One complication was that the perfluoro macrocycles are not soluble in common organic solvents. On the other hand, both organometallic compounds and organic species as well as these perfluoro macrocycles are soluble in... 

Tikhonova, I. A., Dolgushin, F. M., Yanovsky, et al, Crown compounds for anions. A polymeric complex of cyclic trimeric perfluoro-o-phenylenemercury with thiocyanate anion containing an infinite helical chain of alternating molecules of mercury-containing macrocycle and SCN- ions. J. Organomet. Chem. 1996, 508, 271-273. 

These systems exhibit considerable affinity for halide anions. X-ray analysis ascertained the formation of an anionic 2 1 chloride adduct of (1) where the chloride is simultaneously bound by four mercury atoms. In the crystal structures of (2) Cl and (2) l2, the anions are located within the macrocycle and complexed cooperatively by the four mercury(II) centers. Several anionic complexes of (3), including bromide, iodide, and thiocyanide salts, have been isolated. The compounds adopt multidecker stmctures with the hexacoordinated anions effectively sandwiched between two successive molecules of (3). The Lewis acidity of perfluoro-ortAo-phenylenemercury (3) has also been substantiated by its ability to form stable adducts with neutral substrates (HMPA, DMSO, ethyl acetate, and acetonitrile) and arenes. The (3) -CeHe adduct exists as extended stacks of nearly parallel, staggered molecules of (3), which sandwich benzene molecules. Similar structures have been reported for the corresponding adducts with biphenyl, naphthalene, pyrene, and triphenylene. 

For example, perfluoro-4-/ 6>-propylpyridine was found to be an excellent building block for macrocycle synthesis.Nucleophilic substitution reaction with di-oxyanions, prepared in situ from bis-trimethylsilyl derivatives of appropriate alkyl and aryl diols and catalytic quantities of fluoride ion, firstly give bridged systems, in... 

An allosteric carrier consisting of three crown ether subunits in which conformational information is transferred through the two biphenyl linkages has been prepared <94JOC2939>. New synthetic approaches to large (30 - 72-membered) crown ethers and perfluoro-O-macrocycles <94JA5172> have been reported. 

Complexes with bound perfluoro groups are well defined high spin derivatives independent of the porphyrin macrocycle, the temperature, the solvent, and the sample preparation. This behavior is very close to that described for halogenated ferriporphyrins and demonstrates the electron withdrawing character of this type of ligand. 

The replacement of an alkyl ligand by an aryl ligand on Fe(Por)(R) for a given porphyrin macrocycle increases the fraction of the complex present in a high spin form. This is shown in Table 4 and explains why the only high spin states are seen for Fe(Por)(R) with perfluoro ligands. 

Perfluoro crown ethers have been synthetically inaccessible by conventional reactions of fluorocarbons and outside the capability of synthesis by fluorination using selective fluorination reagents. Examples of this potentially useful class of macrocycles have been prepared recently in our laboratory. These syntheses have been initially accomplished using the broadly applicable technique for controlling reactions of elemental fluorine (the La Mar process) developed in our laboratory. The reactions were conducted in the previously described cryogenic fluorination reactor (2),... 

The ability to form and characterize new types of macrocyclic ion complexes involving perfluoro ethers holds great promise for future studies of host-guest complexation in the gas phase. Comparisons to the gas-phase chemistry of hydrogenated macrocycles may allow further insight into the influence of thermochemical and structural properties on the binding interactions of host molecules. All of the perfluoro crown ethers and perfluorocryptands to date have been found to coordinate 02 and F as well as some otii c anions (24). 

A mixture of isomeric perfluoro-dimethyldiphenyltetrahydrobiphenyls, such as (274), has been formed by the reaction of pentafluorobenzoyl peroxide with octafluorotoluene. Macrocyclic hydrocarbons (275) have resulted from the sulphides (276) by oxidation to the sulphones followed by pyrolysis. 

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