Diaza crown ethers bearing heterocyclic ligating groups on nitrogen atoms and their complexing properties with divalent inorganic cations

Two nitrogen-substituted 4,13-diaza-I8-crown-6 compounds, bearing 2-methylquinolyl and 2-methylquinolyl-1-oxide groups, have been prepared. Ionophore-cation selectivities with a range of inorganic divalent cations have been investigated by means of membrane techniques, demonstrating their high selectivity for the Hg(II) cation.     

An NMR study of the stoichiometry and stability of lithium ion complexes with 12-crown-4, 15-crown-5 an 18-crown-6 in binary Acetonitrile-Nitrobenzene mixtures

Proton NMR spectroscopy was used to study the complexation reaction between lithium ion and 12-crown-4, 15-crown-5 and 18-crown-6 in a number of binary acetonitrile-nitrobenzene mixtures. In all cases the exchange between free and complexed crowns was fast on the NMR time scale and only a single population average¹H signal was observed. Formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and the amount of acetonitrile in the mixed solvent. It was found that, in all solvent mixtures used, 15-crown-5 forms the most stable complex with Li⁺ ion in the series.     

Arjunolic Acid in Molecular Recognition: First Synthesis and Cation Binding Studies of a novel Arjuna-18-crown-6

Arjunolic acid, a functionally rich chiral triterpenoid with a rigid pentacyclic backbone, has the potential to be used as a structural framework for the design of molecular receptors and supramolecular architectures. The design and synthesis of the first arjunolic acid-derived 18-crown-6 and its binding studies with metal and tert-butylammonium ions are reported.     

Inclusion compounds ofcis-syn-cis andcis-anti-cis diastereoisomers of dicyclohexano-18-crown-6 with amidosulfuric acid

Both title complexes were prepared by reacting a methanol solution of the respective isomer of dicyclohexano-18-crown-6 (DCH18C6) with an aqueous solution of amidosulfuric acid. Crystals suitable for X-ray crystallography were obtained by recrystallization from methanol.Crystals of [cis-syn-cis-DCH18C6][NH₂SO₂OH·CH₃OH] (1) are monoclinic, space groupP2₁ln,a = 21.700(8),b = 13.725(5),c = 9.118(6) Å, = 76.29(2) Å. Refinement led to a final conventionalR value of 0.065 for 2083 reflections. [Cis-anti -cis-DCH18C6][NH₂SO₂OH] (2) crystallizes in the orthorombic space groupPna2₁ with unit cell dimensionsa = 17.154(7),b = 16.051(7),c =8.630(5) Å. Refinement was terminated at anR value of 0.067 for 1936 reflections.     

Complexation of Amino Acid Methylesters and Amino Alcohols by 18-Crown-6 and Benzo-18-crown-6 in Methanol

The complexation of protonated amino acid methylesters and amino alcohols bythe ligands 18-crown-6 (18C6) and benzo-18-crown-6 (B18C6) has been studiedin methanol using calorimetric titrations. No influence of the anions upon thestability constants and thermodynamic data for the reaction of protonated aminoacid methylesters with both ligands has been noticed, which indicates the completedissociation of the salts employed. A similar effect has been observed for thecomplexation of protonated and unprotonated amino alcohols with 18C6 andB18C6. The values obtained of the reaction enthalpies for the complexation ofprotonated amino acid methylesters with 18C6 are larger than those correspondingto the complexation with B18C6. The results demonstrate that the complex formationof unprotonated amino alcohols is favored by entropic contributions, while thecomplexation of protonated amino alcohols is favored by enthalpic contributionswith both ligands. The influence of various substituents on the complexation behaviorof amino acid and amino alcohol has also been investigated.     

1H NMR and spectrophotometric study of alkaline metal ion complexes with N-dansyl aza-18-crown-6

Formation of complexes of A18C6-Dns and metal cations (Ca²⁺, Sr²⁺, Ba²⁺ and Mg²⁺) in acetonitrile has been studied by NMR, absorption and fluorescence spectroscopy and PM5 semi-empirical methods. A18C6-Dns forms stable complexes with Ca²⁺, Sr²⁺ and Ba²⁺ cations. The stability constants of various complexes are determined by different methods and their structures are visualised by the PM5 semi-empirical calculations.     

Molecular design of crown ethers .18.~1 Cationextractability and selectivities of selena-13- to 14-crown-4

Three selena-crown-4 derivatives have been prepared and their cation binding abilities and selectivities with alkali and heavy metal ions have been evaluated by solvent extraction of aqueous metal picrates to show the highest Ag extractability for novel benzo-selena-14-crown-4 (2,3-benzo-7,12-diselena-1, 4-dioxacyclotetradecane-2-ene) over any other crown ethers.     

Synthesis of 5,6-indolo-12-crown-4 ethers

o-Alkyl derivatives of N-acetylaminobenzo-12-crowns-4 4a—f were prepared by Pd—Cu-catalyzed alkynylation of 5"-N-acetylamino-4"-iodobenzo-12-crown-4 (2). Cyclization of compounds 4a—f afforded the corresponding substituted 5,6-indolo-12-crowns-4 5a—c.     

12-Membered crown ethers. Derivatives of benzo-and naphtho-12-crown-4 and their membrane electrode properties. Part II

A series of lipophilic derivatives of benzo-12-crown-4 and naphtho-12-crown-4 has been synthesized. The behavior of the prepared derivatives in membrane ion-selective electrodes has been studied. Selectivity changes dependent on the position and number of substituents have been observed.     

Potentiometric study of complexation of phenylaza-15-crown-5, 4-nitrobenzo-15-crown-5 and dibenzopyridino-18-crown-6 and other derivative of 18-crowns-6 with Na+ ion in methanol

The complexation reaction of phenylaza-15-crown-5, and 4-nitrobenzo-15-crown-5, benzo-15-crown-5 and dibenzopyrdino-18-crwon-6, dibenzo-18-crown-6,dicyclohexyl-18-crown-6(cis and trans), and 18-crown-6 with Na⁺ ion in methanol have been studied by potentiometric method. The Na⁺ ion-selective electrode has been used both as indicator and reference electrode. The stoichiometry and stability constants of complexes of these crown ethers with sodium ion were evaluated by MINIQUAD program. The major trend of stability of resulting complexes of these macrocycle with Na⁺ ion varied in the order DCY18C6 > DB18C6 > 18C6 > DBPY18C6 > phenylaza-15C5 > benzo-15C5 > 4-nitrobenzo-15C5. The obtained results in particular stability constant of complexes of DBPY18C6, phenylaza-15C5 and 4-nitrobenzo-15C5 with sodium ion in comparison with other crowns ether are novel, and interesting.     

Computer modelling studies of 18-crown-6 with urea and thiourea

Abstract

Computer modelling studies have been carried out on the interaction of 18-crown-6 with a variety of guest molecules, including urea, thiourea and substituted ureas. The five known crystal structures of these host/guest systems were used as models. We were interested to establish whether the arrangement of guest molecules around a host molecule in the crystal was indicative of the lowest energy configuration for a host/guest fragment or was a consequence of packing effects. Two models were therefore considered for each structure and the structures minimised via molecular mechanics. In the first mode, the structure consisted of one unit cell and periodic boundary conditions were used in the calculation. Coulombic effects were calculated using the Ewald summation. In the second model, the structure consisted of an 18-crown-6 molecule surrounded by two hydrogen-bonded guest molecules. Both models were minimised using the CERIUS package using the DreidingII forcefield.

The crystal structure minimisations reproduced the structures very well with an average change in cell volume of 3.6% and a mean r.m.s. positional deviation of 0.20 Å. The fits for the fragment models were significantly larger for all structures (mean 0.30 Å) but even so it can be concluded that the arrangement in the crystal gave a good indication of the lowest energy configuration of the host/guest in vacuo.     

The structure of a 1:4 adduct between 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) and thiourea

The structure of 18-crown-6·4 thiourea has been determined by single crystal X-ray methods. The unit cell is monoclinic and the space group isP2₁, witha=9.251(3),b=19.285(8),c=16.556(7) Å and =90.85(6)°. There are two formula units, C₁₂H₂₄O₆·4CH₄N₂S, in the asymmetric unit; finalR=0.086. One thiourea is attached at either side of the macrocycle (biangular conformation) via N–N...O bonds and the patterns in the two crystallographically-independent adductsA andB differ slightly, involving two bifurcated hydrogen bonds inA. Core adducts are linked by additional thiourea molecules via N–H...S bonds. As compared to the analogous 18-crown-6·5 urea, the present 1:4 stoichiometry might be attributed to the longer S...N hydrogen bonding distance, i.e., to the bigger van der Waals radius of sulphur. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82004 (31 pages). To obtain copies, see p. ii of this issue.     

Synthesis and complexation of molecular clips based on diphenylglycoluril and dibenzocrown ethers with alkali metal cations and paraquat

A new synthetic route to the molecular clip with diphenylglycoluril and dibenzo-18-crown-6 using protection-deprotection protocol is proposed. Yield of desired compound has increased from 10-15% to 41%. Starting from 4,5-dibromobenzene-1,2-diol 4,5-dibromodibenzo-18-crown-6 and then tetrabromo-substituted molecular clip were obtained. The target molecular clip was obtained by bromine cleavage by hydrogenolysis. Stability constants were determined by spectrophotometric titration with alkali metal cations and paraquat. Quantum-chemical calculations confirm the assumption of additional stabilization of complex with K⁺ by π–π stacking between the terminal aromatic fragments with formation of a “pseudocryptand” type structure. The structures of complexes of the molecular clips with paraquat were determined by X-ray crystallography.     

Imidazo-benzo-15-crown-5 ethers bearing arylthienyl and bithienyl moieties as novel fluorescent chemosensors for Pd and Cu

Novel fluorescent ionophores bearing imidazo-arylthienyl or imidazo-bithienyl π-conjugated bridges functionalized with one or two fused benzo-15-crown-5 ethers as receptor units are reported. The sensing ability of the compounds in the presence of metallic cations (Li⁺, Na⁺, K⁺, Ca²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Pd²⁺, and Hg²⁺) and fluoride ion was studied in MeCN/DMSO solutions by absorption and emission spectroscopy. The experimental results indicate that all compounds could act as selective fluorimetric sensors for Cu²⁺ and Pd²⁺ and also for the fluoride ion, in the case of the bis-substituted crown ether derivatives.     

Synthesis, complex-formation, and extracting ability of new derivatives of dithia-13(16)-crown-4(5) ethers

Various methods of synthesizing functional derivatives of dithia-13(16)-crown-4(5) ethers are proposed. Complex-formation of the obtained compounds with Ag⁺ and Pb²⁺ ions has been studied using ¹H NMR. A radiometric method was used to investigate the extracting ability of substituted dithia-13(16)-crown-4(5) ethers in relation to Ag⁺ and Cd²⁺ ions from aqueous solution in the presence of anions of various degree of hardness, with determination of the metal content. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 233–243, February, 2006.     

A thermodynamic study of the association of alkali metal cations with dicyclohexano-18-crown-6

A thermodynamic study of the association of Na⁺, K⁺, Rb⁺, and Cs⁺ with dicyclohexano-18-crown-6 in acetonitrile has been carried out at 308, 303, 298, 293, and 288 K using a conductometric technique. The observed molar conductivities, A, were found to decrease significantly for mole ratios less than unity. A model involving 11 stoichiometry has been used to analyze the conductivity data. The stability constant,K, and the limiting molar conductivity, A _c , for each 11 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of logK at 298 K, as derived from this study is K⁺>Na⁺>Rb⁺>Cs⁺. Values of H ^o and S ^o are reported and their significance is discussed.     

Complexation of niobium(V) with some bis-(β-diketones)

The complexes of niobium(V) with 2-phenyl-1,1,3,3-tetraacetylpropane and 2-phenyl-1,3-diacetyl-1,3-dibenzoylpropane were investigated by IR, UV,¹H-NMR, and magnetic measurements. Together with analytical data and determination of molecular weights a trimeric structure is proposed for both 1:1 complexes.

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Komplexierung von Niob(V) mit einigen Bis(-diketonen)

Zusammenfassung Es wurden die Komplexe von Niob(V) mit 2-Phenyl-1,1,3,3-tetraacetylpropan und 2-Phenyl-1,3-diacetyl-1,3-dibenzoylpropan untersucht. IR-, UV- und¹H-NMR-Spektren sowie magnetische Messungen zusammen mit analytischen Daten und Molekulargewichtsbestimmungen ergaben für beide 1:1 Komplexe eine trimere Struktur.

     

Synthesis and structure of supramolecular complexes between 1-alkynyl(phenyl)(tetrafluoroborato)-λ-iodanes and 18-crown-6

Slow evaporation of a solution of 1-decynyl(phenyl)(tetrafluoroborato)-λ³-iodane and 18-crown-6 in dichloromethane-diethyl ether-hexane gave a supramolecular 1:1 complex, while 3,3-dimethyl-1-butynyl- and phenylethynyl(phenyl)(tetrafluoroborato)-λ³-iodanes afforded 2:1 complexes. Complexation with 18-crown-6 increased the thermal stability of the phenylethynyl-λ³-iodane. Solid state and solution structures of these complexes were examined by single crystal X-ray analyses, ¹H and ¹³C NMR spectra, and cold-spray ionization MS. Binding constants were measured by ¹H NMR titrations.     

The structure of the uncharged-molecule complex between a dinaphthopyridino-18-crown-6 host and acetonitrile (1 : 2)

Single crystal X-ray analysis of a 1 : 2 complex between the dinaphthopyridino-l8-crown-6 host (1) and acetonitrile is reported. Crystals of the complex are monoclinic,P2₁/c witha = 12.178(5),b = 8.186(1),c = 30.873(1) Å, = 96.86(1)°, andD _c = 1.25 g cm^–3 forZ = 4. The host molecule reveals an approximate mirror symmetry and exists in a so-called dentist's chair conformation. One of the acetonitrile guest molecules is involved in possible weak interactions to two oxygen atoms of the host macroring, while the other fills free lattice space only.