Dibenzo- crown

Perfluoro crown ethers from the hydrocarbon dibenzo crown ethers have also been synthesized (58) and the first perfluorocryptand molecule [2.2.2] has been reported (59). The perfluorocryptand is a stable, inert, high boiling clear oil. 

Polymeric pseudocrown ether networks have been generated in situ by the photopolymerization of poly(ethylene glycol) diacrylate transition metal complexes <00CM633>, and the effect of metal ion templation was evaluated. The 1,6,13,18-tetraoxa[6.6]paracyclophane-3,15-diyne (termed pyxophanes) was prepared from hydroquinone and l,4-dichlorobut-2-yne it forms size-selective 7i-complexes with alkali metal cations <00CC2377>. Dibenzo[ ]crown-m have been used in numerous elegant studies in which they were the needles that were threaded by diverse reagents the resultant... 

Dibenzene chromium(O), physical properties, 6 528t Dibenzo-crown-6, 5 710 molecular formula, 5 713t Dibenzo[18]crown-6, 7 576 24 40, 41 Dibenzo[30]crown-10, 24 43 Dibenzocrown ethers, 24 50 Dibenzofurans, 27 152 Dibenzopyrenquinone dyes, 9 336 Dibenzothiophenes, 27 152 Dibenzoyl peroxide (BPO), 74 283-284 78 427... 

Figure 25 Plots of log K, (in MeOH at 25 °C) for complex formation between alkali metal cations and several cyclohexano- and dibenzo-crown ethers (reproduced with permission from reference 31)...

Casnati, A., Sansone, F., Dozol, J.F. 2001. New calyx[4]arene-monobenzo- and dibenzo-crown-6 as cesium selective ionophores in the radioactive waste treatment Synthesis, complexation and extraction properties. J. Inch Phenom. Macro. Chem, 41 (1-4) 193-200. 

Additionally, substantial effects on the fullerene-centered reduction steps due to cation complexation by the tangential and proximal dibenzo-crown ether were observed by cyclic voltammetry (CV) for ( )-37 [30,55] (Figure 16). The CV was recorded both in the presence of one equivalent of [2.2.2]cryptand and in the presence of ten equivalents of KPF6. The cryptand was added to ensure that the species observed initially was uncomplexed, since peaks corresponding with the Na+ and K+ complexes were observed in the FAB mass spectrum of... 

Low-symmetry crown ethers, possessing (3m + )-crown- z scaffolds, show a less pronounced binding ability than symmetrical crown ethers, but display much higher selectivities for specific cations . For instance, polymer membrane thallium(l)-selective electrodes based on dibenzo-crown ether derivatives 67 have been developed <1996CCR171>, because of the environmental and biological implications associated with the poisoning of Tl+ ions. 

Crown ether-functionalized polyphenylenes are a class of electroactive polymers obtained by electropolymerization (anodic coupling) of (di)benzo- or (bi)naphthalene-crown ethers <1998CCR1211, 1998PAC1253>. Tricyclic triphenyl-ene derivatives, such as 78, can be electrogenerated from benzo-15-crown-5 <1989NJC131> and benzo-18-crown-6 <1992JEC399>. Similarly, the anodic oxidation of dibenzo-crown ethers has produced poly(dibenzo-crown ethers), best represented by 79, where triphenylene moieties are presumably two-dimensionally linked via polyether bridges. 

The trimethylsilyloxy (TMSO) group is stable under the coupling conditions in acetonitrile (Table 4, number 11). After oxidative dimerization the TMS ether can be mildly hydrolyzed (H and H2O) to the phenol or converted to a dibenzofuran. 1,2-Dialkoxybenzenes have been trimerized to triphenylenes (Table 4, numbers 9, 12, and 13). The reaction product is the triphenylene radical cation, which is reduced to the final product either by zinc powder or in a flow cell consisting of a porous anode and cathode [60]. Dibenzo-crown ethers are converted by anodic oxidation to electroactive polymers. Films of these polytriphenylenes exhibit unusual doping properties 62-64]. 

Macrocycllc compounds (some crown ethers and cryptands) are selective reagents for extractive separation of alkali metals [22-27]. These ligands form cationic complexes with alkali metal ions, and these can be extracted as ion-pairs with suitable counter-ions e.g., picrate) [28], most often into chloroform. For potassium, p-nitrophenoxide was used as counter-ion [29]. In cases, where a coloured anionic complex is a counter-ion [30], the extract may serve as a basis for determining the alkali metal. The effect of the structure of the dibenzo-crown ether rings upon the selectivity and effectiveness of isolation of alkali metals has been studied in detail [31]. Chromogenic macrocyclic reagents applied for the isolation and separation of alkali metals have been discussed [32]. 

Hdgberg and Cram (1975) and Biernat and Luboch (1984) prepared some dibenzodiaza-, triaza-, and tetraaza-crowns from a bis-tosylanilide derivative prepared from o-nitrophenol (method V-7). This procedure allows the synthesis of dibenzo-crowns containing from two to four nitrogen atoms de-... 

Tabic 9.6. Dibenzo-crown Ethers with Five Heteroatoms. 515... 

TABLE 9.4. DIBENZO-CROWN ETHERS WITH FOUR HETEROATOMS... 

Dibenzoaza-crown macrocycles (miscellaneous), table. 454 Dibenzo-18-crown-6, 4, 19, 79, 86 Dibenzo-crown ethers with four heteroatoms, table, 508... 

Dibenzo-crown ethers with five heteroatoms, table, 515... 

The ionizable crown ethers which were utilized in the metal ion transport studies include a series of dibenzo crown ether carboxylic acids 1-6 and a series of crown ether phosphonic acid monoethyl esters"2, (Figure 2). Within the first series, the crown ether ring sizeTs systematically varied from 14-crown-4 to 16-crown-5 to 19-crown-6 in compounds 1, 2 and 2 respectively. For compounds 2, 4 and 5, the crown etfier ring size is held constant but tTie attachment site of the lipophilic alkyl group is altered. Finally, for compounds 2 and 6, the crown ether ring size and lipophilic... 

Figure 8 (a) Dibenzo-lS-crown-6 (12), uncomplexed (b) Dibenzo- -crown-6 (12), in the complexed form. The metal is in the centre approximately equidistant from the six oxygen atoms. In both drawings oxygen atoms are represented by the larger and carbon atoms by the smaller circles... 

In addition to PPy and PTh derivatives, numerous reports have focused on the synthesis and the properties of electroactive polymer films electrogenerated from the oxidation of crown ether-substituted benzenes [273-286] and naphthalenes [17, 287-293]. Among them, poly(dibenzo-crown ether)s and, especially, poly(dibenzo-18-crown-6) have been the most extensively studied, owing to their remarkable structural, electrochemical, and complexing properties [278-280]. Furthermore, their affinity for a large variety of cations, including heavy metal and precious metal cations, was greatly improved when they were previously undoped [281-286]. 

The three crown ethers which have been most widely used are dibenzo-18-crown-6 [39], dicyclohexyl-18-crown-6 [39] and 18-crown-6 [46]. The dibenzo crown (7) owes its popularity to the fact that a straightforward and efficient preparation of this stable and readily handled substance was published early and a detailed procedure is available in Organic Syntheses [43]. The difficulties with this compound are two-fold. First, it is not one of the better cation complexing crowns [40, 47],... 

Perfluoro cis-syn-cis- and cis-anti-cis-Dicyclohexyl[18]Crown-6 Ether. Very recently we have synthesized perfluoro crown ethers from the hydrocarbon dibenzo crown ether (see Figure 8) (10). We have prepared two interesting isomers of perfluorodicyclohexyl[18]crown-6 ethers fi0),the cis-syn-cis and cis-anti-cis isomers. Their structures have also been established by X-ray crystallography. 

Figure 8. The dibenzo crown ether hydrocarbon starting material.

In anionic ROP, kp and kp were determined for a number of monomer/ counterion/solvent systems [24]. Results obtained for CL polymerization was typical for a majority of other systems namely, alkoxide macroions were much more reactive than alkoxide macroion pairs for example kp = 3.5xl0 mol ls, whereas = 4.8 and 5moT Is" for the K [144] and K /18-dibenzo-crown-6 ether (DEC) [102] counterions, respectively (THF solvent, 20°C). Interestingly, the enthalpy of activation for the macroions [AHp(-) = 39.2 kj mol" ] was higher than that for macroion pairs [AHp( ) = 13.7kJmol" j. Therefore, below a certain temperature-the temperature of inversion (TJ-the reactivity of macroions should be lower than that of the macroion pairs (Equation 1.26). The T calculated from the thermodynamic parameters of activation for macroions and macroion pairs... 

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