Polyether Bridge Research Articles

Rational Design and Synthesis of OEP and TPP Centered Phosphorus(V) Porphyrin-Naphthalene Conjugates: Triplet Formation via Rapid Charge Recombination.

Six new "axial-bonding" type "phosphorus(V) porphyrin-naphthalene" conjugates have been prepared consisting of octaethylporphyrinatophosphorus(V) (POEP+)/tetraphenylporphyrinatophosphorus(V) (PTPP+) and naphthalene (NP). The distance between the porphyrin and NP was systematically varied using polyether bridges. The unique structural topology of the octaethylporphyrinatophosphorus(V) (POEP+) and tetraphenylporphyrinatophosphorus(V) (PTPP+) enabled construction of mono- and disubstituted phosphorus(V) porphyrin-naphthalene conjugates, respectively. The steady-state and transient spectral properties were investigated as a function of redox properties, distance, and molecular topology. Strong electronic interactions between the phosphorus(V) porphyrin and NP in directly bound conjugates were observed. The established energy diagrams predicted reductive electron transfer involving singlet excited phosphorus(V) porphyrin and NP to generate high-energy (∼1.83-2.11 eV) charge-separated states (POEP/PTPP)•-(NP)•+. Femtosecond transient absorption spectral studies revealed rapid deactivation of singlet excited phosphorus(V) porphyrin due to charge separation wherein the estimated forward rate constants were in the range of 109-1010 s-1 and were dependent on the distance between the NP and porphyrins units, as well as the redox potentials of the type of the phosphorus(V) porphyrin. Additionally, due to high exothermicity and low-lying triplet states, the charge recombination process was found to be rapid, leading to populating the triplet states of phosphorus(V) porphyrins.

Anion, cation and ion-pair recognition by bis-urea based receptors containing a polyether bridge

ABSTRACTTwo bis-urea type receptors were synthesized containing a polyether bridge and two 4-nitrophenyl groups as chromogenic units, R1 and R2. Molecular recognition studies of receptors towards different tetraalkylammonium and alkali metal salts were carried out in DMSO by UV-Vis and 1H-NMR spectroscopy. The receptors were found to have high affinity for diverse anions and ion-pairs, showing the highest affinities towards the tetramethylammonium and sodium salts. The cation binding ability of the receptors was evidenced by means 1H NMR, mass spectrometric ESI+ studies and the crystal structures of some precursors. Additionally, the molecular modelling at the DFT level of the tetramethylammonium acetate complexes illustrates the potential ion-pair binding ability of the receptors: the anion is recognized through strong hydrogen bonds from the NH─ groups from the two urea sites, while the cation is bound by a combination of cation─π, C-H···O and C-H···π interactions.

Influence of polyether chain on the non-covalent interactions and stability of the conformers of calix[4]crown ethers

Conformational preferences of the calix[4]crown-(4,5,6,7)-ethers were studied utilizing HF/6-31G(d), B3LYP/6-31G(d), B3LYP/6-311G(d), MPWB95/6-31G(d), MPWIPW91/6-31G(d) and M062X/6-31G(d) methods. DFT-D3 (Becke–Johnson) dispersion correction method was also employed. The results acquired from the analysis of the computational data indicated that the stability of conformers of calix[4]crown-(4,5,6,7)-ethers follows the order; cone conformer > partial cone conformer > 1,3-alternate conformer. It was initially assessed, in general, that both hydrogen bond and OH⋯π interactions play a crucial role in determining the stability of the different conformers. It was further observed that the strength of both H-bond and OH⋯π interactions, are dependent on the length of the polyether bridge. Hence, in order to comprehend them better, the effect of these interactions was studied systematically on the conformational stability of different isomers. It is found that both intramolecular hydrogen bonds and O–H⋯π interactions are mainly responsible for relative stabilities of these conformers, which in turn is also dependent on the length of the polyether bridges. The computational study reported here demonstrate that the size of the polyether bridge along with non-covalent interactions such as hydrogen bond and OH⋯π interactions play an important role in determining the stability of the conformers of calix[4]crown ethers.

Syntheses and Fully Diastereospecific Photochromic Reactions of Thiophenophan‐1‐enes with Chiral Bridges

Thiophenophan-1-enes with chiral polyether bridges were prepared and their diastereospecific photochromic reactions were studied. The coupling reaction of substituted dithienylethenes and various chiral synthons afforded thiophenophan-1-enes, namely, bridged dithienylethenes, as single enantiomers without optical resolution, thus indicating that these reactions occurred diastereoselectively. Upon UV irradiation, each optically active thiophenophan-1-ene isomerized to the corresponding enantiomer of the closed form and returned to the initial enantiomer of the open form upon visible irradiation. Because thiophenophan-1-enes never isomerized to other diastereomers even at a high temperature, they underwent diastereospecific photochromic reactions. Large changes were observed in the measurement of the optical rotations of the solutions of thiophenophan-1-enes at 588 nm according to their photochromic reactions. As there was no absorption at this wavelength for both isomers of each thiophenophan-1-enes, the nondestructive readout of the photochromic reaction could be carried out by using these chiral thiophenophan-1-enes.

Cation binding resorcinarene bis-crowns: the effect of lower rim alkyl chain length on crystal packing and solid lipid nanoparticles

A group of seven resorcinarene bis-crown ethers (CNBC5) with two polyether bridges at the upper rim and either propyl, butyl, pentyl, heptyl, nonyl, decyl or undecyl groups at the lower rim were synthesized and their binding properties with Cs+ were investigated by NMR titration. The bis-crowns form 1 : 2 complexes with Cs+ with binding constants of log K 4–5. Crystal structures of bis-crowns and their Cs+ and K+ complexes were studied and different packing motifs were found depending on the alkyl chain length. Short ethyl, propyl and butyl alkyl chains gave a layer or pillar packing where the polar and non-polar regions cannot be distinguished, whereas longer pentyl and decyl chains formed bilayers. Amphiphilic properties and self-assembly in water were studied by preparing solid lipid nanoparticles (SLNs) from the bis-crowns. All investigated compounds formed stable SLNs showing amphiphilic character, which in the case of the short chain bis-crowns probably arises from their locked boat conformation separating the polar face of the molecule from the non-polar face.

Bis{5-[(2-propyn-1-yl-oxy)meth-yl]-1,3-phenyl-ene}-32-crown-10.

The mol­ecule of the title compound {systematic name: 17,35-bis­[(2-propyn-1-yl­oxy)meth­yl]-2,5,8,11,14,20,23,26,29,32-deca­oxatricyclo­[31.3.1.115,19]octa­triaconta-1(37),15,17,19 (38),33,35-hex­a­­ene}, C36H48O12, has crystallographic inversion symmetry and adopts a chair-like conformation. The polyether bridges of the macrocycle adopt gauche conformations and the cavity of the macrocycle is collapsed. In the crystal structure, there are weak inter­molecular C—H⋯O hydrogen bonds driven in part by the elevated acidity of acetylenyl H atoms.

Electrochemical copolymerization and characterization of dianilines linked by polyether bridge with aniline

Copolymer of aniline and triethylene glycol bis(o-aminophenyl) ether was synthesized by constant potential electrolysis. Cyclic voltammogram of the copolymer films recorded in the monomer-free electrolytic solution revealed that the redox behavior of the films approaches to that of poly(triethylene glycol bis(o-aminophenyl) ether) with increasing amount of triethylene glycol bis(o-aminophenyl) in the feed ratio. Copolymerization was investigated by in situ recording the changes in the electronic absorption spectrum during electrolysis. The free standing copolymer film was characterized utilizing Fourier transform infrared spectrometer, and spectroelectrochemical behavior of the copolymer was investigated via in situ UV–vis spectroscopic technique. Besides the electron spin resonance study of the copolymer film, the different morphologies of the polymers were examined by scanning electron microscopy and the copolymerization was confirmed. The temperature dependence conductivity of the copolymer film was measured by four-probe technique in the temperature range of 100–300 K, and the calculated parameters showed that conduction mechanism fits to variable range hopping.

Synthesis and photochromic properties of thiophenophan-1-enes containing a polyether bridge

[2.n]Thiophenophan-1-ene derivatives containing a polyether bridge have been synthesized by the coupling reaction of bis(iodomethyl)dithienylethene with polyethylene glycols under high dilution conditions. All prepared [2.n]thiophenophan-1-enes were photochromic, as photocyclization of the open forms took place by UV irradiation to give a yellow solution of the closed form and their ring opening reactions occurred upon visible irradiation. There were significant differences in the quantum yields for the photocyclization reactions and the photo ring-opening reactions due to the difference in their structures since their electric properties are similar. The kinetic parameters of the thermal ring opening reaction of the closed forms of thiophenophan-1-enes were estimated and they were also dependent on their bridges.

Synthesis, transport, and ionophoric properties of α,ω-diphosphorylated aza podands: IV. Induced membrane transport of alkali and alkaline-earth metal ions

Membrane transport of alkali and alkaline-earth metal ions by polyether podands containing terminal α-(phosphinoylalkylamino) fragments is studied. Some features of the relationship between the structure of the polyether bridge and substituents at the phosphorus atom, on the one hand, and transport properties of the carrier, on the other, are revealed. Transport efficiency is found to tend to correlate with transported ion size and distance between carrier donor centers.

Electrochemical polymerization and characterization of polyether‐substituted aniline derivatives

AbstractNew compounds consisting of aniline units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis and cyclic voltammetry in an aqueous solution containing 3.0 mol L−1 H2SO4. Chemical polymerization was carried out using (NH4)2S2O8 as oxidizing agent. It was found that both methods gave the same polymer product without any cleavage of the polyether bridge between aniline rings. The polymers were characterized using the Fourier transform infrared spectroscopic technique and the thermal behavior of electrochemically prepared polymers was investigated using thermogravimetric analysis. Spectroelectrochemical properties of the films were investigated using the in situ UV‐visible spectroscopic technique. Copyright © 2007 Society of Chemical Industry

Anodic Oxidation of N‐Substituted Dipyrrolyl Linked by Polyether Bridge

Electroactive polymer containing polyether pseudo‐cages has been synthesized by anodic oxidation of 1,11‐bis(1,1‐pyrrole)‐3,6,9‐trioxaundecane (I) using acetonitrile (ACN) as solvent and tetrabutylammonium perchlorate (TBAClO4) as supporting electrolyte. Electrochemical behavior of monomer I and its polymer, poly‐I, were studied using cyclic voltammetry (CV) and UV‐VIS spectroscopic techniques. Also, a doping/dedoping study was carried out using electron spin resonance (ESR) and UV‐VIS spectroscopic techniques. Thermal behavior of the product was studied using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).

A macrocyclic chiral manganese(III) Schiff base complex as an efficient catalyst for the asymmetric epoxidation of olefins

A new chiral macrocyclic Mn(III)-salen complex has been prepared with two salicylidene moieties linked together to their 3 and 3′ positions by an aliphatic polyether bridge. This complex provides a highly enantioselective (up to 93%) catalyst for epoxidation of cis-disubstituted olefins with sodium hypochlorite as an oxygen atom donor and can be recycled up to three times without significant loss in performance.

Electrochemical copolymerization of 2-substituted thiophene derivative linked by polyether bridge with thiophene

New conducting copolymers have been synthesized via electrochemical oxidation of thiophene (Th) in the presence of monomer bis(2-thienyl)ethyl ( I). Cyclic voltammetry (CV) studies showed that the presence of monomer I in the electrolytic solution greatly changes the CV behaviour of the formation of the polythiophene films. It is found that the increasing ratio of I was found to decrease electroactivity of copoly( I-Th). Electrochemical synthesis of copolymer films was achieved via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6) dissolved in CH 3CN. Spectroelectrochemical (SPEL) properties of the films were investigated using UV–vis spectroscopic technique.

Synthesis and activity of macrocyclized chiral Mn(III)–Schiff-base epoxidation catalysts

A series of chiral macrocyclic Mn(III)Salen complexes has been prepared with two salicylidene moieties linked in their 3 and 3′ positions by aliphatic polyether bridges of variable lengths or by a more rigid aromatic junction arm. X-ray structures of ligand precursors and of complex 8 have been performed. All complexes have been used in the asymmetric epoxidation of 1,2-dihydronaphthalene with NaOCl as oxygen atom donor and exhibited modest enantiomeric excesses. Complex 10 was selected to be tested with two cis-disubstituted olefins and several oxidants, namely NaOCl, PhIO and n-Bu 4NHSO 5. 2,2′-Dimethylchromene oxide was obtained from 2,2′-dimethylchromene with ee values of 56% and 74% when using 10 and NaOCl and PhIO, respectively.

Synthesis of a regular polymer containing pseudo-polyether cages

A new compound consisting of 2-thienyl units linked by polyether bridge has been synthesized and its electrochemical polymerization was performed via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6) dissolved in CH 3CN. Chemical polymerization was carried out using FeCl 3 as oxidizing agent. It is found that both methods gave the same polymer product without any cleavage of the polyether bridge between thiophene (Th) rings. Although as synthesized polymers exhibited no conductivity, they gain conductivity via chemical doping using I 2 vapor exposure. The polymers were characterized using FT-IR spectroscopic technique and I 2 doping was monitored using in-situ electron spin resonance (ESR) spectroscopy. Thermal behavior of electrochemically prepared polymer was investigated using differential scanning calorimetry, DSC and thermogravimetric analysis, TGA.

Synthesis and polymerization of 2- and 3-substituted thiophene derivatives linked by polyether bridges

New compounds consisting of 2- and 3-thienyl units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) dissolved in CH3CN. 2-Thienyl monomers (I and II), but not 3-thienyl monomers (III and IV), were also polymerized via chemical oxidation, which yielded broken π-conjugated polymer products. The polymers were characterized using 1H NMR and FT-IR spectroscopic techniques. It was found that both chemical and electrochemical oxidation of 2-thienyl monomers gave mainly poly(2,2′-bithiophenemethylene) due to elimination of polyether chains during the polymerization reaction. On the other hand, electrochemical oxidation of 3-thienyl monomers resulted in corresponding polymers without any cleavage of polyether bridges. Spectroelectrochemical (SPEL) properties of the products were investigated using UV–Vis spectroscopic techniques.

Synthesis and polymerization of 2- and 3-substituted thiophene derivatives linked by polyether bridges

New compounds consisting of 2- and 3-thienyl units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6) dissolved in CH 3CN. 2-Thienyl monomers ( I and II), but not 3-thienyl monomers ( III and IV), were also polymerized via chemical oxidation, which yielded broken π-conjugated polymer products. The polymers were characterized using 1H NMR and FT-IR spectroscopic techniques. It was found that both chemical and electrochemical oxidation of 2-thienyl monomers gave mainly poly(2,2′-bithiophenemethylene) due to elimination of polyether chains during the polymerization reaction. On the other hand, electrochemical oxidation of 3-thienyl monomers resulted in corresponding polymers without any cleavage of polyether bridges. Spectroelectrochemical (SPEL) properties of the products were investigated using UV–Vis spectroscopic techniques.

Enlarging the size of calix[4]arene-crowns-6 to improve Cs +/K + selectivity: a theoretical and experimental study

Ab initio calculations in the gas-phase indicate that the substitution of an ethylene with a propylene moiety in the polyether bridge of 1,3-di- iso-propoxycalix[4]arene-crowns-6 could result in an enhanced Cs +/K + selectivity which is of particular interest in nuclear waste treatment. We therefore synthesised two novel calix[4]arene-crown-6 compounds ( 1 and 2 ) having a propylene moiety in their structure and for this named calix[4]arene-propylene-crown-6. The structures of compounds 1 and 2 were elucidated by NMR in solution and for 1 also by X-ray diffraction studies in the solid state. Association constants ( K a) in CHCl 3 of the two novel calix-crowns were measured and pointed out a plateau selectivity towards alkali metal ions which was not predicted by molecular modelling calculations. These results indicate the important role played by the solvent molecules and counter-anions in binding for this class of ionophores.

A Copper(II) Complex of a Macrocyclic Schiff Base Ligand with a Polyether Bridge

In the structure of aquachloro[7,10,13-trioxa­3,17,23-triazabicyclo[17.3.1]tricosa-1 (23),2,17,19,21-pentaene-N,N',N′′]copper(II) hexafluorophosphate acetonitrile solvate, the CuII ion is pentacoordinate with square-pyramidal coordination geometry, with a relatively long axial bond to water [2.244 (5) Å] and with the shortest Cu-N bond being to the pyridine N atom. The water molecule is also hydrogen bonded to two O atoms of the ligand. The complex is folded about the N-Cu-N axis, the polyether chain being nearly planar and making an angle of about 135° with the pyridine ring.

Alkali-metal ion catalysis and inhibition of acetyl transfer from p-nitroaryl acetates to hexanoate ion

Deacetylation of 2-acetoxy-5-nitro-1,3-xylylene-18-crown-5 (21 -acetoxy-18-nitro-2,5,8,11,14-pentaoxa[18]metacyclophane) by hexanoate ion in DMF is strongly inhibited by Li+ ion, slightly retarded by Na+ ion, and significantly promoted by the larger alkali-metal ions. In contrast, the analogous reaction of the simple model p-nitrophenyl acetate is inhibited by all of the alkali-metal ions. These effects are discussed in terms of differential binding of metal ions to reactants and transition states. In line with conclusions from previous works, it is confirmed that coordinative binding of metal ions with the oxygen donors of the polyether bridge of the crown-ether substrate is an effective force for catalysis.