Benzocrown ether

Barboiu, M., Hovnanian, N., Luca, C., Popescu, G. and Cot, L. (1998) Functionalized derivatives of benzocrown-ethers, III, New macrocydic derivatives containing chiral and linear lateral amino-acid moieties. European Journal of Organic Chemistry, 1705—1708. 

The reaction of diselena-benzocrown ether with Li2PdCU afforded a novel cationic palladium tetraselena complex<99JCS(D)1039>. 

The predictive power of the luminescent PET sensor principle is again apparent here. Further, the benzocrown ether and the amine receptors would selectively bind Na" and H, respectively. A remarkable feature here is that no molecular wiring is needed to allow the human operation of this two-input molecular device. The device self-selects its own ion inputs into the appropriate signal channels by means of the chemoselective receptor modules. Since the output signal is fluorescence, even a single molecule can interface with detectors in the human domain, including the dark-adapted eye. Tanaka s 45 is another example where fluorescence quenching is achieved only when Ba and SCN are present. This was mentioned in Section 6. Similarly, several sensor systems—1,17, and 21—could be employed... 

A series of azobis(benzocrown ethers) called butterfly crown ethers such as 9 and 10 were synthesized [11-15]. The photoresponsive molecular motion is... 

It was found that the linking of styryl dye fragment to benzocrown ether results in novel photochromic compounds CESD (Crown Ether Styryl Dyes) possessing interesting physico-chemical properties (Scheme 1) [13], The dyes are intensively colored and show significant hypsochromic shifts upon complexation with alkaline earth metal cations in acetonitrile solution. Reversible photochemical reaction E,Z-isomerization is observed for both dyes and their complexes. 

Shinkai et al.111-151 synthesized a series of azobis(benzocrown ethers) called butterfly crown ethers , of which compounds 9 and 10 are examples. Their photoresponsive molecular motion resembles that of a flying butterfly. It was found that the proportion of their Z forms at the photostationary state increases remarkably with increasing concentration of Rb+ and Cs+, which interact with two crown rings in a 1 2 sandwich fashion. This is clearly due to the bridge effect of the metal cations with the two crowns, results that support the view that the Z forms make an intramolecular 1 2 complex with these metal cations. As expected, the Z forms extracted alkali metal cations with large ion radii more efficiently than did the corresponding E forms. In particular, the photoirradiation effect on 9 is quite remarkable for example, ( )-9 (n= 2) extracts Na+ 5.6 times more efficiently than (Z)-9 (n= 2), whereas (Z)-9(n= 2) extracts K+ 42.5 times more efficiently than ( )-9(n= 2). l ... 

Shifting our attention to the fluorophore, we consider anthracene derivatives because of our prior experience with them [18] and (more importantly) because of the wealth of data available on them in both the electrochemical and photophysical spheres. Even at an intuitive level, anthracenes are a good starting point because such rigid, well-delocalized systems are usually efficient fluorophores [32]. It is also important that the benzocrown ether receptor is transparent to the communication wavelengths of the fluorophore in excitation and in emission. Anthracene derivatives satisfy this criterion very well in this instance. Further progress can be made via three avenues and the most general path is explored first. 

Importantly, the goodness-of-fit parameters are satisfactory and the coefficient of the term involving (M +tolal) is near unity in all cases. Also, it must be noted that the stability constants for the alkali cation-benzocrown ether interaction available in the literature [30,48] agree closely with the values extracted from Fig. 5 for the alkali cation (14) association. All of this very gratifyingly support the expectations of the fluorescent PET sensor design logic in terms of a supermolecule with modular behaviour [43],... 

In contrast with the dibenzo-18-crown-6 integrated fluorophore-receptor system 4,33,34 the first use of PET systems with benzocrown ether receptors arrived a decade later in the form of 22.59 Receptor 22 shows fluorescence switching on by Na+ with excellent selectivity against protons. Earlier PET systems employed azacrown... 

Poly(methylsilylene-/>-phenylene)s carrying Si-linked benzocrown ether and ethoxy pendant groups 86 (parameters x and y are associated with the benzo crown vs. ethoxy ratio present in the polymer) showed ionochromic behavior, and responded selectively to alkali and alkaline earth metal ions in the emission spectra, depending on the crown ether ring size. These polymers also display solvatochromic properties by changing the solvent polarity in the absence of metal ions <2006OM2225>. 

The bicyclic heteroaromatic bases 191 possess arrays of complementary donor-donor-acceptor and acceptor-acceptor-donor hydrogen bond sites and an additional benzocrown ether moiety. Structure and dimension of the nanotubes were determined by NMR, dynamic light scattering, small-angle X-ray scattering, and transmission electron microscopy. Addition of sodium or potassium ions did not interfere with the stability of the multichannel... 

In order to elucidate the primary electrostatic through bond mode of electrochemical communication between a ferrocene redox centre and the heteroatoms of the crown ionophore, a variety of conjugated ferrocene benzocrown ether systems such as 60 and 61 [83, 84], 62 and 63 [85, 86], and 64 or 65 [87, 88] were synthesized and their complex formation with mono- and divalent cations studied by multinuclear NMR, X-ray crystallography and cyclic voltammetry. 

Carbenes, generated by photolysis of di- and tetrachloro-o-quinone diazides, react with oxetane in a 1 3 ratio to afford 15-membered crown ethers. Benzocrown ether 675 was obtained in 16% yield (91CB1865). Derivatives of macrocyclic crown ethers with four or five oxygen atoms in a ring were synthesized by Cu(acac)2-catalyzed cyclization of a,polyethylene glycols. 20-26-Membered crown-4(5) ethers 676 were prepared from the above-mentioned diazo ketones with tri- or tetra-ethylene glycols in 7-26% yields. Treatment of l,8-bis(diazoacetyl)octane with dodecane-l,12-diol under the same conditions results in a mixture of 52-membered tetraether 646 (40%) and compound 645 (81CC616). 

Eight regioisomers are possible for doubly bridged calix[6]arenes (Figure 7) from which examples (mainly crown and benzocrown ethers) for five types have been realized (1,4 2,3-, 1,2 3,5-, 1,2 4,5- and the 1,3 2,5- and l,4 2,5-derivatives with crossed bridges). The situation may be even more complicated since two stable conformational isomers (all-up and uuuddd u = up, d = down) have been obtained from the 1,4-diallyl ether by the introduction of diethylene glycol bridges . ... 

S. Shinkai, K. Shigematsu, M. Sato and O. Manabe, Photoresponsible crown ethers. Part 6. Ion transport mediated by photoinduced cis-trans interconversion of azobis-(benzocrown ether), J. Chem. Soc., Perkin Trans. I, 1982, 2735-2739 J. Anzai, H. Sasaki, A. Ueno and T. Osa, Photo-induced potential changes across poly(vinyl chloride)-crown ether membranes, J. Chem. Soc., Chem. Commun., 1983, 1045 J. Anzai, H. Sasaki, K. Shimokawa, A. Ueno and T. Osa, Photocontrol of alkali metal ion permeability through the poly(vinyl chloride)/crown ether membranes, Nippon Kagaku Zasshi, 1984, 338. 

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