Benzocrown Ether Moiety Research Articles

Ethynylpyrene Linked Benzocrown Ethers as Fluorescent Sensors for Metal Ions.

Substances containing ethynylpyrenes linked to either one or four benzocrown ethers were synthesized, and their absorption and fluorescence spectroscopic responses to metal ions were assessed. Addition of metal perchlorates to solutions of these substances promotes short wavelength shifts in their absorption and fluorescence maxima and increases in their fluorescence intensities. The magnitudes of the fluorescence intensity increases are dependent on the ring size and number of the crown ether and the nature of the metal cation. Association constants for complex formation were calculated using fluorescence intensity versus concentration data. Analysis using Job's plots showed that the substances containing one benzocrown ether moiety form 1:1 complexes with metal ions. Results of experiments employing repeated addition and removal of Mg(ClO4 )2 demonstrate that the ON-OFF fluorescence response can be repeated at least three times. Results of molecular orbital calculations show that complexation with metal ions lowers the energies of both the π and π* levels of the ethynylpyrene moiety and that in some cases the vacant orbital on the metal becomes the LUMO of the complex. An explanation of the spectroscopic changes promoted by metal ions is proposed in terms of electrostatic repulsion and structural regulation.

Synthesis, Structure, and Properties of Supramolecular Photoswitches Based on Ammonioalkyl Derivatives of Crown Ether Styryl Dyes

The synthesis of new styryl dyes derived from 4-pyridine and 4-quinoline and having an ammonioalkyl N-substituent and benzocrown ether moieties of different sizes and with different sets of heteroatoms was developed. Spontaneous "head-to-tail" dimerization of these dyes via the formation of numerous hydrogen bonds between the terminal NH3(+) groups and crown ether moieties was detected in MeCN solutions. The stability constants of the dimeric complexes having pseudocyclic structure were studied by (1)H NMR titration. The most stable complexes (log Kd up to 8.2) were found in the case of dyes with the 18-crown-6 ether moiety, which is most complementary for binding a primary ammonium group. Stacking interaction of the conjugated systems in the dimeric complexes contributes to their stability to a much lesser extent. In dimeric complexes, the ethylene bonds of the dyes are preorganized for stereospecific [2 + 2] photocycloaddition (PCA) induced by visible light. PCA yields only rctt isomers of bis-crown-containing cyclobutane derivatives. The dyes were studied by X-ray diffraction; it was found that the dimeric arrangement is also retained in the crystalline state. The possibility of topochemical PCA of the dyes in single crystals without their destruction was demonstrated. The possibility of retro-PCA of the obtained cyclobutane derivatives to give the starting dyes was shown. The elucidated regularities of PCA can be used to fabricate optical data recording systems based on ammonioalkyl derivatives of crown ether styryl dyes.

Synthesis, crystal structure, and alkali metal picrate extraction capabilities of molecular clips based on diphenylglycoluril and benzocrown ethers

A convenient method for the synthesis of a series of molecular clips based on the diphenylglycoluril framework and benzocrown ether moieties by the reaction of bis(cyclomethoxymethylene)diphenylglycoluril with benzocrown ethers in polyphosphoric acid is proposed. X-ray diffraction analysis of molecular clips with the benzo-12-crown-4 and benzo-15-crown-5 fragments showed that both compounds are chloroform solvates with the stoichiometry clip:chloroform 1:1. By theoretical and experimental methods the existence of obtained clips in an anti–anti conformation was proved. The complexation properties of the obtained molecular clips were examined toward alkali metal and ammonium ions by FABMS spectrometry and extraction experiments.

Membrane Potential Photoresponse of Crowned Malachite Green Derivatives Affording Perfect Photoswitching of Metal Ion Complexation

Photoirradiation effect on potential response to metal ion concentrations and photoinduced potential change were investigated with poly(vinyl chloride) membranes based on a Malachite Green derivative carrying a bis(monoaza-15-crown-5) moiety, by comparing other Malachite Green derivatives. The Malachite Green carrying a bis(crown ether) moiety caused a potential response to potassium ion concentration changes under dark condition. In the membrane potential response, a clear-cut photoinduced switching of potential response was realized by the membrane of Malachite Green carrying a bis(crown ether) moiety, which exhibited no potential response to potassium ion concentrations (0 mV/decade) on UV irradiation. On the other hand, a Malachite Green carrying a monocyclic benzocrown ether moiety showed a considerable dependence of the membrane potential on the metal ion concentrations under both dark and UV irradiation conditions.

Simulation of optical response to complex formation of crown-containing 2-styrylbenzothiazoles with alkaline-earth metals

The photochromic properties and complex formation of 2-styrylbenzothiazoles containing different crown ether moieties with alkaline-earth metals were described using optical methods, NMR spectroscopy, and HPLC. The large ionochromic effect and fluorescence quenching on complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the phenylazacrown ether moiety. The small ionochromic effect and fluorescence enhancement of complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the benzocrown ether moiety. cis-Isomers of 2-styrylbenzothiazoles were stable in the dark in acetonitrile. The method for separation of cis-isomers of 2-styrylbenzothiazoles by HPLC was proposed.

New bis-ferrocenyl dibenzo-18-crown-6 ligands that can electrochemically sense group 1 and 2 metal cations

New bis-ferrocenyl dibenzo-18-crown-6 ligands have been prepared in which the ferrocene redox centre is appended to the benzo crown ether moiety by unsaturated imine (Schiff bases) and saturated methylene amine bond linkages (secondary amine derivatives). 1H and 13C NMR titration studies reveal that both types of ligand form 1:1 complexes with sodium and potassium cations. Magnesium cations from 2Mg 2+: Schiff base complexes in which 1H NMR and electronic spectral evidence suggest that the divalent metal cation primarily interacts with the imine bond. Electrochemical investigations have demonstrated that, whereas the respective ferrocene redox couples of all ligands are insensitive to K +, the electrochemical sensing of Na + guest cations is only observed with ligands (Schiff bases) that contain the conjugated metallocene cyclopentadienyl-imine-p observed with Mg 2+, except electrochemical observations with 1,2-dimethoxy-4-(iminoferrocenyl)benzene indicate that the crown ether recognition site is not required for the detection of this metal dication.

New cholesterol-based gelators with light- and metal-responsive functions

Cholesterol derivatives containing a benzocrown ether moiety or an azobenzene moiety coupled to C-3 of a steroidal moiety through an ester linkage are synthesized; some of them act as thermally reversible gelators of organic fluids and show novel light- and metal-responsive functions.

Synthesis and complexation properties of a novel potassium-selective trisanisyl bis(benzo-crown ether)

The condensation of 2,2′2″-trimethoxy-5,5′,5″-trimethyl-1,1′:3′,1″-terphenyl-3,3″-di(carbonyl chloride)(2) with two equivalents of 4-aminobenzo-15-crown-5 (15-amino-2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecine)(3) gave a novel bis(crown ether)(4) containing a rigid preorganised trisanisyl chain backbone. Titrations of this new host with alkali-metal cations and the ammonium ion monitored by 13C n.m.r. spectroscopy suggested that the benzo crown ether moieties alone provided the co-ordinating sites for the cationic guests, forming a 1:2 [(4):M+] complex with sodium ions, while potassium, rubidium, and ammonium ions formed 1:1 intramolecular sandwich complexes. The association constants (K/dm3 mol–1) of the bis(crown ether)(4) with picrate salts of potassium (7.93 × 106), rubidium (0.19 × 106), caesium (0.03 × 106), and ammonium (0.02 × 106) in CDCl3 were measured by deuteriochloroform–water extraction and spectroscopic techniques, indicating a high degree of selectivity for potassium over the other cations [K(K+)/K(Rb+)= 42, K(K+)/K(Cs+)= 264, and K(K+)/K(NH4+)= 397]. This result is in agreement with fast-atom-bombardment mass spectrometric competition experiments.

Synthesis and cation‐binding properties of poly‐and bis(thiacrown ether)s

AbstractPoly‐ and bis(thiacrown ether) derivatives in which some oxygen atoms of benzocrown ether moiety are replaced by sulfur atoms have been synthesized. Their cation‐binding abilities were investigated by using the solvent extraction method. The poly‐ and bis(benzothiacrown ether)s showed great affinity for silver ion, being more excellent in the affinity than the corresponding monocyclic analogs. They, however, possess very poor cation‐binding ability for alkali and alkaline‐earth metal ions. The poly‐ and bis(thiacrown ether)s also bind mercuric ions effectively, whereas the corresponding monomeric analogs do not at all.