Synthesis of lariat ether carboxylic acids based on dibenzo‐16‐crown‐5

Synthetic routes to forty‐seven dibenzo‐16‐crown‐5 compounds with pendant carboxylic acid groups are reported. When taken together with previously described lariat ether carboxylic acids, these new compounds provide several series with systematic structural variations including changes in the identity and attachment site(s) of one or more lipophilic groups and the length of the spacer that connects the carboxylic acid group to the polyether framework.     

Lariat ether alcohols based on dibenzo‐16‐crown‐5

Synthetic routes to forty‐four dibenzocrown ether alcohols are reported. The new crown ether com pounds are based on a sym‐dibenzo‐16‐crown‐5 platform. Most have a hydroxy group and an alkyl, aryl, aralkyl, alkenyl, alkynyl, or perfluoroalkyl group on the central carbon of the three‐carbon bridge. Others have substituted benzene rings and either a hydroxy or ‐O(CH₂)_nOH group attached to the central carbon of the three‐carbon bridge.     

Sonochemical reformatsky reactions of α‐bromoesters with sym‐(keto)dibenzo‐16‐crown‐5

Reactions of sym‐(keto)dibenzo‐16‐crown‐5 with ethyl α‐bromoesters, zinc dust and iodine in dioxane and/or tetrahydrofuran under irradiation by high intensity ultrasound (HIU) provide β‐hydroxy lariat ether esters in 79‐91% yields. HIU‐promoted Reformatsky reactions offer several advantages over customary thermal reaction conditions.     

Aqueous solution and solid state interactions of lanthanide ions with a methacrylic ester polymer bearing pendant 15‐crown‐5 moieties

The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H₂O and D₂O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M^?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H₂O and D₂O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M^?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007     

Photochromic LC copolymers containing azobenzene and crown‐ether groups

An approach for the creation of a novel family of multifunctional crown‐ether‐containing comb‐shaped copolyacrylates consisting of chromophoric (azobenzene), ionophoric (crown‐ether), and mesogenic groups in the same macromolecule was developed. Phase behavior of the copolymers was studied, and correlation between their molecular structure and thermal properties was established. The increase of crown‐ether‐containing groups' concentration up to 26 mol % leads to disruption of nematic order and formation of amorphous phase. Influence of copolymers complexation with potassium perchlorate on mesomorphic properties of such systems was investigated. It was shown that complexation leads to decrease in mesophase thermostability due to the significant reducing of the side group anisometry by perchlorate counter ion. The comparative investigations of photooptical properties and photoorientation processes of copolymers and their complexes were also performed. An essential difference in kinetics of photooptical behavior was revealed; the bulky crown‐ether substituents decrease rotational mobility and prevent photoorientation process of azobenzene fragments diminishing photoinduced orientation and order parameter. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6532–6541, 2008     

Synthesis of helical polyisocyanides bearing aza‐crown ether groups as pendant

We, herein, present a novel synthesis of responsive helical poly(aryl isocyanide)s bearing aza‐crown ethers as pendant groups. Chiral aryl isocyanide monomers bearing an aza‐crown ether as a pendant were designed and synthesized, piror to polymerization using a Pd‐Pt µ‐ethynediyl complex as an initiator to give the corresponding polymers in good yield. The resulting polyisocyanides adopted a stable helical structure in solution, as confirmed by circular dichroism spectroscopic analysis. In addition, the polymers were soluble in various solvents. Furthemore, the addition of suitable alkali metal ions to the crown ether of the sidechain on the helical polyisocyanide to form host‐gest complexes resulted in deformation of the helix due to electrostatic repulsion, and these phenomena depended on the size of metal cations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 496–504.     

Synthesis and complexing properties of double armed diaza‐15‐crown‐5 and diaza‐18‐crown‐6 ethers having 4′‐hydroxy‐3′,5′‐disubstituted benzyl groups

A series of double armed diaza‐15‐crown‐5 ethers (9a ‐ 16a) and diaza‐18‐crown‐6 ethers (9b ‐ 16b) have been prepared by the Mannich reaction of 2,6‐disubstituted phenols with the corresponding N,N'‐dimethoxymethyldiaza‐crown ethers in benzene. The crystal structures of the diaza‐18‐crown‐6 ethers having iso‐propyl (10b) , tert‐butyl (11b) , and mixed methyl and tert‐butyl groups (12b) at positions 3′ and 5′ of the phenolic side arms were determined using X‐ray diffraction methods. Competitive transport by these ligands for sodium, potassium and cesium cations were measured under basic‐source phase and acidic‐receiving phase conditions.     

4‐Methoxyanilinium tetrafluoroborate–dibenzo‐18‐crown‐6 (1/1)

In the structure of the complex of dibenzo‐18‐crown‐6 [systematic name: 2,5,8,15,18,21‐hexaoxatricyclo[20.4.0.0^9,14]hexacosa‐1(26),9,11,13,22,24‐hexaene] with 4‐methoxyanilinium tetrafluoroborate, C₇H₁₀NO⁺·BF₄⁻·C₂₀H₂₄O₆, the protonated 4‐methoxyanilinium (MB‐NH₃⁺) cation forms a 1:1 supramolecular rotator–stator complex with the dibenzo‐18‐crown‐6 molecule via N—H...O hydrogen bonds. The MB‐NH₃⁺ group is attached from the convex side of the bowl‐shaped crown, in contrast with similar ammonium cations that nest in the curvature of the bowl. The cations are associated via C—H...π interactions, while the cations and anions are linked by weak C—H...F hydrogen bonds, forming cation–crown–anion chains parallel to [011].     

Synthesis of photopolymers with pendant cyclic carbonate and cinnamic ester groups

Photopolymers with both pendant cyclic carbonate groups and cinnamic ester groups were synthesized by the addition reaction of poly(glycidyl methacryalte-co-styrene)[poly(GMA-co-AN)] with carbon dioxide and then with cinnamoyl chloride. Soluble quaternary ammonium salt catalysts showed good yield of cinnamoyl chloride addition to the glycidyl methacrylate groups. Quaternary salt catalysts of longer alkyl chain length and of more nucleophilic anion offered higher yield of cinnamoyl chloride addition. Photochemical reaction test showed that poly(CNMA-co-DOMA-co-St) had a good photosensitivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

(Borohydrido)(18‐crown‐6)potassium and (borohydrido)(dibenzo‐18‐crown‐6)(tetra­hydro­furan)potassium

In the two compounds (borohydrido)(1,4,7,10,13,16‐hexa­oxacyclo­octa­decane‐κ⁶O)potassium, [K(BH₄)(C₁₂H₂₄O₆)], (I), and (borohydrido)(1,4,7,10,13,16‐hexa­oxa‐2,3:11,12‐di­benzo­cyclo­octa­deca‐2,11‐diene‐κ⁶O)(tetra­hydro­furan)­potassium, [K(BH₄)(C₄H₈O)(C₂₀H₂₄O₆)], (II), the K atom is bound to the six O atoms of the crown ether and to a tridentate borohydride group, with further coordination to a tetra­hydro­furan mol­ecule in (II). The alkali metal ion environment is thus distorted hexa­gonal–pyramidal in (I) and bipyramidal in (II).     

Synthesis of cyanine dyes derived from benzotellurazo‐15‐crown‐5

A series of crown ether cyanine dyes including crown ether styryl cyanine dyes, crown ether merocyanine dyes and crown ether squarylium cyanine dyes (unsymmetric and symmetric) derived from key intermediate 2‐methyl‐5,6(15‐crown‐5)benzotellurazole ( 1 ) were prepared.     

An efficient and new protocol for the Heck reaction using palladium nanoparticle‐engineered dibenzo‐18‐crown‐6‐ether/MCM‐41 nanocomposite in water

Palladium nanoparticle‐incorporated mesoporous organosilica (MCM‐41‐Crown.Pd) was synthesized via the grafting of dibenzo‐18‐crown‐6‐ether moieties on the MCM‐41 surface, followed by reaction of the nanocomposite with palladium acetate and then its reduction in ethanol. The cavity of the immobilized dibenzo‐18‐crown‐6 as host material can stabilize the palladium nanoparticles effectively and prevent their aggregation and separation from the surface. The structure of the nanocomposite was characterized using various techniques. The catalytic properties of the nanocomposite in the Heck coupling reaction, one of the most useful transformations in organic synthesis, between aryl halides and olefins in water were also explored. The main advantages of the method are low cost, high yields, easy work‐up and short reaction time. The nanocatalyst can be easily separated from a reaction mixture and was successfully examined for seven runs, with a slight loss of catalytic activity.     

Polymer monolayers with a photosensitive crown‐ether

The mixed monolayers of a photosensitive crown‐ether (CE) and poly(maleic acid hexadecyl monoamide‐alt‐propylene) (P12) have been prepared and studied. Fluorescence spectra of CE have a strong band at 530–535 nm in solution (monomer) or at 593–603 nm in transferred monolayers (aggregates). Due to the interaction with polymer the fluorescence maximum of CE is shifted to 530 nm in the mixed monolayers with P12.     

A Spectrophotometric Investigation of the Interaction of Iodine with Dibenzyldiaza‐18‐crown‐6, Aza‐15‐crown‐5 and N‐phenylaza‐15‐crown‐5 in Chloroform Solution

The complex formation reactions between iodine and DBzDA18C6, A15C5 and N‐phenylA15C5 have been studied spectrophotometrically in chloroform solution. In the case of DBzDA18C6 is the resulting 1:2 (ligand…I⁺)I₃^?, while, in the case of A15C5 and N‐phenylA15C5 a 2:2 molecular complex of [(ligand)₂…I⁺]I₃^? type was formed. The spectrophotometric results indicate that gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate‐determining step of the reaction. The kinetic rate constants for the complexation reactions were determined at different temperatures, and activation parameters were calculated from Arrhenius and Eyring equations.     

A novel PtII–dibenzo‐18‐crown‐6 (DB18C6) complex

The novel Pt^II–dibenzo‐18‐crown‐6 (DB18C6) title complex, μ‐[tetrakis­(thio­cyanato‐S)­platinum(II)]‐N:N′‐bis{[2,5,8,­15,18,21‐hexa­oxa­tri­cyclo­[20.4.0.1^9,14]­hexa­cosa‐1(22),9(14),10,12,23,25‐hexaene‐κ⁶O]­potassium(I)}, [K(C₂₀H₂₄O₆)]₂[Pt(SCN)₄], has been isolated and characterized by X‐ray diffraction analysis. The structure analysis shows that the complex displays a quasi‐one‐dimensional infinite chain of two [K(DB18C6)]⁺ complex cations and a [Pt(SCN)₄]^2? anion, bridged by K⁺?π interactions between adjacent [K(DB18C6)]⁺ units.     

Invariom‐model refinement and Hirshfeld surface analysis of well‐ordered solvent‐free dibenzo‐21‐crown‐7

Crown ethers and their supramolecular derivatives are well‐known chelators and scavengers for a variety of cations, most notably heavier alkali and alkaline‐earth ions. Although they are widely used in synthetic chemistry, available crystal structures of uncoordinated and solvent‐free crown ethers regularly suffer from disorder. In this study, we present the X‐ray crystal structure analysis of well‐ordered solvent‐free crystals of dibenzo‐21‐crown‐7 (systematic name: dibenzo[b ,k ]‐1,4,7,10,13,16,19‐heptaoxacycloheneicosa‐2,11‐diene, C₂₂H₂₈O₇). Because of the quality of the crystal and diffraction data, we have chosen invarioms, in addition to standard independent spherical atoms, for modelling and briefly discuss the different refinement results. The electrostatic potential, which is directly deducible from the invariom model, and the Hirshfeld surface are analysed and complemented with interaction‐energy computations to characterize intermolecular contacts. The boat‐like molecules stack along the a axis and are arranged as dimers of chains, which assemble as rows to form a three‐dimensional structure. Dispersive C—H…H—C and C—H…π interactions dominate, but nonclassical hydrogen bonds are present and reflect the overall rather weak electrostatic influence. A fingerprint plot of the Hirshfeld surface summarizes and visualizes the intermolecular interactions. The insight gained into the crystal structure of dibenzo‐21‐crown‐7 not only demonstrates the power of invariom refinement, Hirshfeld surface analysis and interaction‐energy computation, but also hints at favourable conditions for crystallizing solvent‐free crown ethers.     

Synthesis,characterization, and metal complexes of polyacetylenes with pendant 2,2′‐bipyridyl groups

5‐Ethynyl‐2,2′‐bipyridine ( 1 ; bpyC≡CH) polymerized in the presence of catalytic amounts of [RhF(COD)(PPh₃)] or [Rh(μ‐OH)(COD)]₂ (COD = 1,5‐cyclooctadiene) in 74–91% yields. In contrast, [Rh(μ‐X)(NBD)]₂ (X = Cl or OMe; NBD = norbornadiene) did not catalyze the polymerization of 1 or gave low yields of the polymer. The obtained polymer, poly(5‐ethynyl‐2,2′‐bipyridine) [ 2 ; (bpyC?CH)_n], was highly stereoregular with a predominant cis–transoidal geometry. Random copolyacetylenes containing the 2,2′‐bipyridyl group with improved solubility in organic solvents were obtained by the treatment of a mixture of 1 and phenylacetylene ( 3 ) or 1‐ethynyl‐4‐n‐pentyl‐benzene with catalytic amounts of [RhF(COD)(PPh₃)]. A block copolymer of 1 and 3 was prepared by the addition of 1 to a poly(phenylacetylene) containing a living end. The reaction of 2 with [Mo(CO)₆] produced an insoluble polymer containing [Mo(CO)₄(bpy)] groups, whereas with [RuCl₂(bpy)₂] or [Ru(bpy)₂(CH₃COCH₃)₂](CF₃SO₃)₂, it gave soluble metal–polymer complexes containing [Ru(bpy)₃]²⁺ groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3167–3177, 2005     

Synthesis and properties of poly(aryl ether ether ketone) copolymers with pendant methyl groups

Polyether ether ketone and polyether ether ketone copolymers were prepared by the nucleophilic substitution reaction of 4,4′-difluorobenzophenone with hydroquinone and with varying mole proportions of hydroquinone and methyl hydroquinone using sulfolane solvent in the presence of anhydrous K₂CO₃. The polymers were characterised by different physico-chemical techniques. The crystallinity of the polymers was found to decrease with increase in concentration of the methyl hydroquinone units in the polymer. Thermogravimetric studies showed that all the polymers were stable upto 430 °C with a char yield above 49% at 900 °C in N₂ atmosphere. The glass transition temperature was found to increase and the crystalline melting temperature and activation energy were found to decrease with increase in concentration of the methyl hydroquinone units in the polymer.