Crown-6 Derivatives Research Articles

Tuning liquid crystalline phase behaviour in columnar crown ethers by sulfur substituents

Sulfur-containing side chains in the periphery ofo-terphenyl or triphenylene units of crown ethers induce room-temperature columnar mesophases.

Separation of silver(I) and copper(II) by polymer inclusion membranes with aza[18]crown-6 derivatives as ion carriers

Separation of silver(I) and copper(II) by polymer inclusion membranes with aza[18]crown-6 derivatives as ion carriers

Cation−π Interaction in Complex Formation Between Tl+ Ion and Calix[4]crown-6 and Some Calix[4]biscrown-6 Derivatives: Thallium-203 NMR, Proton NMR, and X-ray Evidence

Metallocapped complexation of the thallium(I) ion with calix[4]crown-6 (1) and three different calix[4]biscrown-6 derivatives (2-4) has been investigated by a combination of (203)Tl and (1)H NMR in a CD(3)CN/CDCl(3) (4:1 v/v) solution. The results clearly revealed the formation in solution of mono- and dithallium(I) complexes in which the metal cations are held in the ligands' cavities close to the calix[4]arene ring. In addition, a solid state mononuclear complex between 1,3-calix[4]bis-o-benzo-crown-6 (3) and TlClO(4) was prepared, and its X-ray crystal structure was determined. The results of the structural data in solution and the solid state suggested that the calix[4]crown-6 derivatives considered provide pi cavities as active sites for the complexation of thallium(I) ions.

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Dibenzo[18]crown-6 derivatives 1 with two lateral tetraalkyloxy o-terphenyl units were prepared and converted to the corresponding complexes KX1 (X = halide, BF(4), PF(6), SCN) and NH(4)PF(6)1. Complexation was probed by MALDI-TOF spectrometry and NMR spectroscopy. Downfield shifts of (1)H NMR signals for complexes with soft anions Br, I, SCN, and PF(6) indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF(4) showed no or little shifts. In (13)C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX1 (M = K, NH(4)), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1. Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 degrees C phase widths in the case of KI1, KPF(6)1, and NH(4)PF(6)1. For complexes KSCN1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase.

Facilitated transport of Zn(II), Cd(II) and Pb(II) ions through polymer inclusion membranes with calix[4]-crown-6 derivatives

Competitive transport of an equimolar mixtures of Zn(II), Cd(II), and Pb(II) ions from aqueous nitrate source phase ( c Me = 0.001 M, each) through polymer inclusion membranes (PIMs) using calix[4]crown-6 derivatives, as ion carriers, has been investigated. The influence of the group attached type to the calix[4]-crown-6 molecule on the selectivity and efficiency of Zn(II), Cd(II), and Pb(II) transport across polymer inclusion membranes containing cellulose triacetate as the support was studied. The transport selectivity orders for the PIM with 4 and 5 was: Pb(II) > Zn(II) > Cd(II), whereas for 3 was: Pb(II) > Zn(II) ≥ Cd(II). The metal cations transport results can be explained by their tendency as the Lewis acids in chemical interaction with the bases. The selectivity coefficients of Pb(II)/Zn(II) and Pb(II)/Cd(II) decrease with the hydrochloric acid concentration increase in receiving phase. Also the influence of the plasticizers nature, i.e. o-nitrophenyl pentyl ether ( o-NPPE), o-nitrophenyl octyl ether ( o-NPOE), and bis(2-ethylhexyl)adipate (DOA) on the ion transport through PIMs is presented. The initial flux of metal ions insignificantly increases in the following order: DOA < o-NPOE < o-NPPE, i.e. with decrease of plasticizers viscosity. The stability of PIM with calix[4]crown-6 derivatives was confirmed in replicate experiments.

Self-assembled monolayers of different conformers of p- tert-butylcalix[4]crown-6 derivatives and their metal cation recognition properties

Two isomers of p- tert-butylcalix[4]crown-6 derivatives form stable self-assembled monolayers (SAMs) by taking advantage of the adsorption of bis-thioctic ester on gold electrodes, and their Cs + recognition is completely dependent on the conformational orientation of the compounds.

Synthesis of chiral 1,3-calix[4](crown-6) ethers as potential mediators for asymmetric recognition processes

Novel chromogenic 1,3-calix[4](crown-6) derivatives comprised of 1,1′-binaphthyl-, methyl-α- d-glucoside-and d-mannitol moieties in the crown ether ring have been synthesized. UV–vis spectroscopic measurements of the 2,4-dinitrophenylazo chromogenic molecules indicated noticeable chiral discrimination associated with coloration towards primary amine enantiomers.

Synthesis and complexation properties of 1,3-alternate calix[4]arene-bis(crown-6) derivatives

Calix[4]arene-bis(crown-6) was converted into its di- and tetra-carboxy and hydroxy derivatives as water-soluble receptors. The complexation properties of these ionophores were studied for alkali cations in methanolic and aqueous media. Stability constants were calculated by UV–Vis spectroscopy. All ligands showed a more or less pronounced affinity for the larger cations. Cs+/Na+ selectivity is enhanced by the number and the nature of the substituents. Compound 7 represents the most selective ligand for the Cs+ cation in methanol and in basic aqueous media. For selective Cs+/Na+ separation, the efficiency of the ligands was evaluated by means of a nanofiltration system.

Novel Macrocycles. Part 6. Synthesis, Structures and Cation Binding from Optical Spectroscopy of 9,10-Anthraquinone-crown Ethers

The 9,10-anthraquinone-[12]crown-4, [15]crown-5 and [18]crown-6 derivatives were synthesized from 1,2-dihydroxy-9,10-anthraquinone and 1,8-dihydroxy-9,10-anthraquinone which were condensed with dihalides or ditosylates of polyethylene glycols in alkali carbonate/DMSO. The 9,10-anthraquinone derived polyoxacyclo-alkanes were characterized with IR, mass spectrometry, 1H, 13C spectroscopy and elemental analysis. The cation binding properties were studied with UV-vis spectroscopy. The association constants found in acetonitrile were selectively dependent on the cation radius and macrocycle size as well as the molecular structures. The observed results from UV-vis studies, however, showed the stronger complexing role of 1,2-derived macrocycles compared to those of 1,8-derivatives. The theoretical conformational analysis and the energy optimisations of the 9,10-anthraquinone-macrocycles carried out with MM+ method explained the binding results.

New synthetic receptors based on calix[4]arenes for the selective recognition of ions and neutral molecules

Abstract

ChemInform Abstract: Synthesis and Antiviral Activity of Phosphorus‐Containing Diaza‐18‐ crown‐6 Derivatives.

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