Benzo- 15-crown

Benzo[15]crown-5, potassium complex X-ray, 7, 735 (B-78MI52102) 10H-Benzo[5,6]cyclohepta[l,2-b]furan, 4,5-dihydro-... 

H-Benzo[a]carbazole, 4,4a,5,l 1,1 la,l Ib-hexahydro-synthesis, 4, 283 Benzo[b]carbazole, N-acetyl-photochemical rearrangements, 4, 204 Benzo[/]chroman-4-one, 9-hydroxy-2,2-dimethyl-synthesis, 3, 851 Benzochromanones synthesis, 3, 850, 851, 855 Benzochromones synthesis, 3, 821 Benzocinnoline-N-imide ring expansion, 7, 255 Benzocinnolines synthesis, 2, 69, 75 UV, 2, 127 Benzocoumarins synthesis, 3, 810 Benzo[15]crown-5 potassium complex crystal stmcture, 7, 735 sodium complex crystal stmcture, 7, 735 Benzo[ 18]cr own-6 membrane transport and, 7, 756 Benzo[b]cyclohepta[d]furans synthesis, 4, 106 Benzocycloheptathi azoles synthesis, 5, 120... 

Benzo-15-crown-5 [14098-44-3] M 268.3, m 78-80. Recrystd from n-heptane. IRRITANT. 

The first method is shown in Eq. (3.1). This corresponds to the so-called one plus one synthesis of crowns. The notion is that a single diol unit is allowed to react with a single polyethylene glycol having leaving groups at each end. An example of this would be the synthesis of benzo-15-crown-5 from catechol and tetraethylene glycol dichloride. Note that the stoichiometry of this method is identical to that of method X which is shown below in Eq. (3.3). 

Frensch and Vdgtle have recently appended three crown ether units to the cyclo-triveratrylene unit . Note that Hyatt had previously prepared the open-chained relatives of this structure (see Sect. 7.3 and Eq. 7.6). Whereas Hyatt prepared the cyclo-triveratrylene skeleton and then appended polyethyleneoxy arms to it, Frensch and Vogtle conducted the condensation reaction (formaldehyde/HCl) on the preformed benzocrown. Thus benzo-15-crown-5 was converted into the corresponding tris-crown (IS) (mp 203.5—205.5°) in 4% yield. The yield was somewhat higher for the condensation of benzo-18-crown-6, but in both cases, yield ranges were observed. These species formed 1 3 (ligand/salt) complexes with sodium and potassium ions. 

For the purpose of our discussion, a polycrown is here defined as a polymer system arising by polymerization of a crown monomer unit. Extensive work has been done in this field by Kopolow, Hogen Esch and Smid and the examples presented here are taken from a paper by all three of these workers. A typical preparation of vinylbenzo-15-crown-5 is accomplished according to the scheme shown as Eq. (6.25). One might also have utilized a formylation/Wittig sequence on benzo-15-crown-5 to accomplish the same end. 

Figure 5.7 Molecular structure of benzo-15-crown-5-Ca(NCS)2.MeOH.

Charge transfer reactions at ITIES include both ET reactions and ion transfer (IT) reactions. One question that may be addressed by nonlinear optics is the problem of the surface excess concentration during the IT reaction. Preliminary experiments have been reported for the IT reaction of sodium assisted by the crown ether ligand 4-nitro-benzo-15-crown-5 [104]. In the absence of sodium, the adsorption from the organic phase and the reorientation of the neutral crown ether at the interface has been observed. In the presence of the sodium ion, the problem is complicated by the complex formation between the crown ether and sodium. The SH response observed as a function of the applied potential clearly exhibited features related to the different steps in the mechanisms of the assisted ion transfer reaction although a clear relationship is difficult to establish as the ion transfer itself may be convoluted with monolayer rearrangements like reorientation. 

FIG. 2 Structures of the ionophores 1-4. 1 =dibenzyl-14-crown4 2 = bis(benzo-15-crown-5) 3 =dibenzo-18-crown-6 4 = dibenzo-24-crown-8 these ionophores are selective for Li+, K+, and Na, respectively. (From Ref 15.)... 

IV. MOLECULAR PROBE FOR ISE MEMBRANE POTENTIALS BASED ON PHOTOSWITCHABLE AZOBIS(BENZO-15-CROWN-5) lONOPHORES [17]... 

If the photoequilibrium concentrations of the cis and trans isomers of the photoswitchable ionophore in the membrane bulk and their complexation stability constants for primary cations are known, the photoinduced change in the concentration of the complex cation in the membrane bulk can be estimated. If the same amount of change is assumed to occur for the concentration of the complex cation at the very surface of the membrane, the photoinduced change in the phase boundary potential may be correlated quantitatively to the amount of the primary cation permeated to or released from the membrane side of the interface under otherwise identical conditions. In such a manner, this type of photoswitchable ionophore may serve as a molecular probe to quantitatively correlate between the photoinduced changes in the phase boundary potential and the number of the primary cations permselectively extracted into the membrane side of the interface. Highly lipophilic derivatives of azobis(benzo-15-crown-5), 1 and 2, as well as reference compound 3 were used for this purpose (see Fig. 9 for the structures) [43]. Compared to azobenzene-modified crown ethers reported earlier [39 2], more distinct structural difference between the cis... 

When a membrane based on a derivative of azobis(benzo-15-crown-5) in contact with a solution of a primary cation is exposed to visible light, we assume that the iono-phore within the membrane phase is exclusively in the trans isomer and forms a 1 1 ionophore (I)-cation (M+) complex with a stability constant, trans. According to Eq. (10), the corresponding charge density at the membrane side of the interface, o is > can be expressed as... 

As stated in Section II, the SHG responses to primary cations of ISEs based on several crown ether ionophores could be correlated to the number of primary ion complexes at the phase boundary, which contributed to the membrane potential. We have now incorporated the K+ ionophore bis[(benzo-15-crown-5)-4-methyl]pimelate into 1,2-dichloroethane and nitrobenzene membranes and determined EMF and SHG responses to KCl in presence and absence of ionic sites. 

In a way related are the complexes formed by Hg salts and multicrown dendrimers of different generations (dendrimers with a polypropylene amine interior of different volume and benzo[15]-crown-5 ether periphery), studied by extraction methods using radioactive 203Hg2+.210 Up to 12 Hg2+ ions were found to be bound per dendrimer molecule, obviously in the amine-dominated interior, not in the crown-ether periphery. 

A similar study was undertaken on the related crown ether systems 201 <2001PS29>. They all showed moderate extraction of both Ag(l) and Hg(ll) ions and so were less selective than compounds 184a and 184b from the previous study. However, the presence of the benzo-15-crown-5 substituent offered the simultaneous complexation of the hard alkali cation Na(l) as well as the thiophilic metals Ag(l) and Hg(n) by the thieno sulfur. Interestingly, this second extraction was not influenced by the presence of the other metal. 

Polytopic macrocyclic receptors 1, 2 (Figure 10.1) are able to complex the zwitterionic form of the amino acids by a double non-covalent charge interaction [28,29]. The unsymmetrical benzocrown sulfonamide derivative, 2 which contains benzo-18-crown-6 and benzo-15-crown-5 moieties was used as a ditopic receptor for multiple molecular recognition of the amino acids, by combining two non-covalent interactions ammonium-crown hydrogen bonding and carboxylate- complexed Na+-benzo-15-crown-5 charge interactions [28,33]. 

Barboiu, M., Supuran, C.T., Luca, C., Popescu, G. and Barboiu, C. (1996) Functionalized derivatives of benzocrown-ethers. Part I. Ionophores containing amino and pyridinium groups derived from benzo-15-crown-5, benzo-18-crown-6 and dibenzo-18-crown-6. Liebigs Annalen der Chemie, 959-963. 

Ag2(C=C)-7AgCF3C02-3(Me3NCH2-C02)-H20]-2H20 139 [Ag2(C=C)-5AgCF3C02-(benzo-15-crown-5) 2H2O]-0.5H2O 140... 

Figure 4.4. Structure of the bis-ligand potassium complex of benzo-15-crown-5. The complex shown is cationic (Mallinson Truter, 1972).

The mechanistic basis of 3 and 4 is a double application of the argument used for the YES operation with 1. Each receptor in 3 is capable of launching a PET process if the lumophore is powered up by ultraviolet excitation. In other words, the fluorescence of the 9-cyanoanthracene unit is efficiently quenched by either the amine or the 1,2-dioxybenzene group within the benzo-15-crown-5 ether unit. These quenching processes are predictable from thermodynamic calculations or from related bimolecular quenching experiments in the literature. The small separation of the amine from the lumophore ensures rapid PET kinetics. On the other hand, the presence of four bonds between the benzo-15-crown-5 ether and the lumophore is probably responsible for the incomplete quenching seen between this pair. No information is yet available regarding possible folded conformations of 3. 

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