Complexation of metal ions with the novel diazadithia crown ethers carrying two pyrene pendants in acetonitrile-tetrahydrofuran

Two crown ethers carrying pyrene side arms with nitrogen-sulfur donor atom were designed and synthesized by the reaction of the corresponding macrocyclic compounds and 1-bromomethyl-pyrene. The influence of metal cations such as Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ on the spectroscopic properties of the ligands was investigated in acetonitrile-tetrahydrofuran (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Al³⁺, Zn²⁺, Fe²⁺, Ni²⁺, Cu²⁺, and Pb²⁺ with 16-membered crown ether. Similar results were obtained for Al³⁺, Fe²⁺, Hg²⁺, Cu²⁺ and Pb²⁺ with 14-membered crown ether. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constants of the novel ligands with these cations. According to spectrofluorimetric titration measurements the 14-membered diazadithia crown ether showed sensitivity for Pb²⁺ with linear range and detection limit of 1.3 × 10^?6 to 5.2 × 10^?5 M and 5.2 × 10^?7 M, respectively. The 16-membered diazadithia crown ether showed sensitivity for Ni²⁺ with linear range and detection limit of 1.3 × 10^?7 to 5.2 × 10^?6 M and 4.1 × 10^?8 M, respectively.     

Enantiomeric recognition of amino acids by amphiphilic crown ethers in Langmuir monolayers

Four new chiral, amphiphilic crown ethers differing by the hydrophobic tailgroups were synthesized, and their capacity to recognize enantiomeric amino acids was examined using Langmuir films. Surface pressure and surface potential measurements performed on the subphases containing L or D enantiomers of alanine, valine, phenylglycine, and tryptophane indicate that the crown ethers forming the monolayer interact with the amino acids. The effects observed are ascribed to the formation of host-guest complexes. The differences in the magnitude of the effects measured show that the crown ethers are capable of discriminating between different amino acids as well as the enantiomers. Our results demonstrate that the structure of the monolayer plays a decisive role in the molecular recognition process including chiral recognition.     

Complexation properties of monoaza crown ethers

A series of five monoaza crown ethers with 12-crown-4 and 15-crown-5 rings were studied with respect to their complexation of Li⁺, Na⁺, K⁺, Ca²⁺ and Sr²⁺ ions in 95/5 (v/v) methanol/ water. The complexes were studied by potentiometric titrations, with pH and sodium ion-selective electrodes. The acidity constants of the protonated ligands, and the stability constants of the 1:1 metal complexes were determined. The results show that the stability constants increase with the total number of oxygen atoms in the ligand, and mostly also in the sequence Li⁺ < K⁺ < Na⁺ < Ca²⁺ < Sr²⁺.     

The complexation of alkali metal ions by crown ethers,aza crown ethers,and cryptands in propylene carbonate

The reactions between alkali metal ions and crown ethers, aza crown ethers, and cryptands in propylene carbonate were studied by potentiometric and calorimetric titrations. The most stable complexes formed by macrocyclic and macrobicyclic ligands are when the ligand and cation dimensions are comparable. On comparing the complex stabilities of crown ethers and aza crown ethers of the same size, crown ethers were, on the whole, found to form the most stable complexes, with the exception of the lithium cation. Enthalpic factors are responsible. Substitution of the amino group protons of the aza crown ethers by benzyl groups leads to a high increase in values of the reaction enthalpy. This effect is partly compensated by entropic contributions. The bulky benzyl groups reduce the ligand solvent interactions and induce a ligand conformation with the lone pair of electrons from the nitrogen donor atoms which are more or less directed inside the cavity. The thermodynamic data for the transfer from methanol to propylene carbonate indicate that the ligands containing nitrogen show specific interactions with methanol.This paper is dedicated to Professor H. Strehlow on the occasion of his 70th birthday.     

Spectroscopic study of J aggregates of amphiphilic merocyanine dyes formed in their pure Langmuir films

It is known that an amphiphilic merocyanine dye, 3-carboxymethyl-5-[2-(3-octadecyl-2(3H)- benzothiazolylidene)ethylidene]-2-thioxo-4-thiazolidinone (DS) and its derivatives DSe and 6MeDS form J aggregates under the presence of metallic cations, although the dyes' static dipole moments must be favorable for H aggregates. A metal-free J aggregate of 6MeDS has been generated in its pure Langmuir films and transferred onto CaF2 substrates to investigate the molecular environment around the carboxylic group born by the dye. Combining visible and infrared spectroscopy, geometrical consideration based on ab initio calculations, and simulation of the excitation energy, a structural model of this J aggregate has been proposed. With this model, formation of intermolecular carboxyl-keto hydrogen bonds, which can compensate the electrostatic disadvantage of the J aggregate under the presence of water, has been suggested. As for another derivative of DS, DO, similar discussion has been made for its Mg2+ -containing J aggregate, which is found in this work. In addition, the proposed structural model can tell the cause of the difference in the tendency to J aggregate among 6MeDS, DSe, DS, and DO.     

Synthesis of chromogenic crown ethers and liquid-liquid extraction of alkali metal ions

New crown ethers carrying a pendent phenolic chromophore were synthesized. These crown ethers, on dissociation of the phenolic proton, provide lipophilic anions which can extract alkali metal cations into 1,2-dichloroethane by forming highly-colored uncharged metal complexes. Structural effects on the extraction were studied for possible use of these crown ethers as extraction—spectrophotometric reagents selective for alkali metals. The following factors are discussed in detail: (i) nature of the crown ether ring (ring size. aza-crown or standard crown ether), (ii) nature of the pendent phenolic group, and (iii) geometry between the crown ether center and pendent phenolic group. 15-Crown-5 or smaller ring-sized reagents favored the extraction of lithium ion when the basicity of the pendent phenolate was relatively high and a six-membered “chelate” ring was possible for the phenolate and the crown ether-bound metal. 15-Crown-5 type reagents were sodium-selective when an eight-membered “chelate” ring was possible between the phenolate and the crown ether-bound metal. 18-Crown-6 type reagents were generally potassium-selective. However, these selectivities were not absolute, and other structural parameters, steric and conformational, must be considered to explain in detail the selectivities of the individual reagents.     

Langmuir and Langmuir-Blodgett films of amphiphilic bistable rotaxanes

A series of amphiphilic bistable [2]rotaxanes--in which a ring-shaped component, the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), has been assembled around two recognition sites, a tetrathia-fulvalene (TTF) unit and a 1,5-dioxynaphthalene (DNP) ring system, situated apart at different strategic locations within the central polyether section of an amphiphilic dumbbell component that is terminated by a hydrophobic tetraarylmethane-based stopper (near the TTF unit) at one end and by a hydrophilic tetraarylmethane-based stopper (near the DNP ring system) at the other end--has been designed and synthesized. The effects of systematic changes in the constitutions of the three ethylene glycol tails (diethylene or tetraethylene glycol) and end groups (hydroxyl or methoxyl functions) attached to the hydrophilic stoppers on Langmuir film balance and surface rheology experiments at 20 degreesC were examined to determine the monolayer stabilities and co-conformations of the [2] rotaxanes and their free dumbbell counterparts. These experiments allow us to propose a model for the rotaxane's structures at different surface pressures. All the [2]rotaxanes form stable Langmuir films. These films typically pass from a liquid-expanded region to a liquid-condensed region. The transition between the two regions was either directly observed or ascertained using film stability experiments. Film balance and surface rheology experiments showed that the addition of the tetracationic cyclophane component and hydroxyl end groups markedly increased the stabilities and viscoelasticity of the films.     

Complexation of crown ethers and heteroanalogs of 18-crown-6 with alkali and alkaline earth metal cations in dichloroethane

Data on the complexing ability of a series of crown ethers and heteroanalogs of 18-crown-6, containing S-, SO-, SO₂- and SONH fragments at the 1- and 10-positions of the macrocyclic ring, with Li, Na, K, Mg and Ba picrates in dichloroethane were obtained from the solubility of the salts in the presence of the crown compounds. It was found that 18-crown-6 is the best but the least selective ligand of all the picrates, while polyethers with SO- and SONH fragments show an appreciable selectivity toward Li⁺, and to a lesser extent, toward Mg⁺. The complexing ability of the disulfone ligand is inappreciable under the conditions studied. A 11 stoichiometry of the complexes has been found for the individual crown-picrate pairs.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 191–196, March–April, 1988.     

Chemistry of crown ethers: Complexation with alkali metal trichloro(ethylene)platinum(II) salts

A novel method has been developed for the determination of the complexation constants of crown ethers with alkali salts. It comprises the equilibration of crown ether (1–7) solutions in deuterochloroform with solid trichloro(ethylene)platinum(II) salts (Na⁺, K⁺, Rb⁺, Cs⁺) and the PMR spectroscopic determination of the equilibrium ratio of complex to free crown ether from the relative intensities of the ethylene and crown ether protons. The solubility of uncomplexes salt was determined independently by atomic absorption spectrometry.The major advantages of this method over others are: (i) complexation constants in apolar solvents are obtained from a direct solid-liquid transition, (ii) the cation in the salt can be varied, and (iii) a simple detection technique can be used for monitoring the complexation.The PMR spectra indicate that there are three types of complex, depending on the ratio of the diameter of the crown ether cavity to that of the cation. If this ratio is small (<1), the aromatic ring is almost perpendicular to the flat polyether ring. With increasing ratio (～1.0) the flat polyether ring and the aromatic ring become almost coplanar in the complex. If the ratio is large (>1.0) the polyether ring is twisted around the cation.     

Order in amphiphilic polyimides: Cast and Langmuir films

Amphiphilic polyimides with side methylene tails and various chemical structure of the backbones have been studied in the “bulk” state (cast films) and in the form of multilayered molecular films (Langmuir films) by means of calorimetry, X-ray scattering and pressure-area diagrams.     

Langmuir monolayer and Langmuir–Blodgett films of amphiphilic triblock copolymers with water-soluble middle block

Langmuir monolayers and Langmuir–Blodgett (LB) film morphology of amphiphilic triblock copolymers are studied using surface pressure-area measurements and atomic force microscopy (AFM), respectively. The triblock copolymers are composed of long water-soluble poly(ethylene oxide) (PEO) chains as middle block with very short poly(perfluorohexylethyl methacrylate) (PFMA) end blocks. The surface pressure-area isotherms show phase transitions in the brush regime. This phase transition is due to a rearrangement of PFMA block at the air–water interface. It becomes more significant with increasing PFMA content in the copolymer. LB films transferred at low surface pressures from the air–water interface to hydrophilic silicon substrates show surface micelles in the size range of 50–100 nm. A typical crystalline morphology of the corresponding PEO homopolymer is observed in LB films of copolymers with very short PFMA blocks, transferred in the brush region at high surface pressure. This crystallization is hindered with increasing PFMA content in the copolymer.     

Fabrication of metal nanoparticle monolayers on amphiphilic poly(amido amine) dendrimer Langmuir films

A newly designed 1.5th generation poly(amido amine) dendrimer with an azacrown core, hexylene spacers, and octyl terminals was spread on gold nanoparticle (Au-NP) suspension. The surface pressure-area isothermal curves indicated that the molecular area of dendrimer on Au-NP suspension was significantly smaller than that on water, indicating the formation of dendrimer/Au-NP composites. The dendrimer Langmuir films on the Au-NP suspension were transferred to copper grids at various surface pressures and observed by transmission electron microscopy. The transferred films consisted of a fractal-like network of nanoparticles at low surface pressure and of a defect-rich monolayer of nanoparticles at high surface pressure. From these results, it was suggested that the dendrimers bind Au-NPs, and dendrimer/Au-NP composites formed networks or monolayers at the interface. From the intensity decrease of the Au plasmon band of Au-NP suspension after the formation of composite, it was estimated that some (approximately 14) dendrimer molecules bind to one Au-NP. Furthermore, neutron reflectivity at the air/suspension interface and X-ray reflectivity of the film transferred on a silicon substrate revealed that the dendrimer molecules are localized on the upper-half surface of Au-NP. Metal affinity of azacrown, flexibility of hexylene spacer, and amphiphilicity of dendrimer with octyl terminals played important roles for the formation of dendrimer/Au-NP hybrid films. The present investigation proposed a new method to fabricate the self-assembled functional polymer/nanoparticle hybrid film.     

Complexation of polymethacrylopiperidide with transition metal ions in aqueous solution

The interactions of polymethacrylopiperidide with Cu²⁺, Ni²⁺, Co²⁺ and Fe³⁺ ions have been investigated by potentiometric and conductometric titration, ESR and u.v. spectroscopy, viscometry and sedimentation. The average number of ligands coordinating with the central metal ions and the stability constants of polymeric metal complexes were determined. It is assumed that the polymethacrylopiperidide interacts with transition metal ions through the nitrogen atoms. The influence of spatial arrangement of donor atoms on the coordination ability of polyligand is discussed.     

Langmuir and Langmuir-Blodgett films of multifunctional, amphiphilic polyethers with cholesterol moieties

Langmuir films of multifunctional, hydrophilic polyethers containing a hydrophobic cholesterol group (Ch) were studied by surface pressure-mean molecular area (π-mmA) measurements and Brewster angle microscopy (BAM). The polyethers were either homopolymers or diblock copolymers of linear poly(glycerol) (lPG), linear poly(glyceryl glycidyl ether) (lPGG), linear poly(ethylene glycol) (lPEG), or hyperbranched poly(glycerol) (hbPG). Surface pressure measurements revealed that the homopolymers lPG and hbPG did not stay at the water surface after spreading and solvent evaporation, in contrast to lPEG. Because of the incorporation of the Ch group in the polymer structure, stable Langmuir films were formed by Ch-lPG(n), Ch-lPGG(n), and Ch-hbPG(n). The Ch-hbPG(n), Ch-lPEG(n), Ch-lPEG(n)-b-lPG(m), Ch-lPEG(n)-b-lPGG(m), and Ch-lPEG(n)-b-hbPG(m) systems showed an extended plateau region assigned to a phase transition involving the Ch groups. Typical hierarchically ordered morphologies of the LB films on hydrophilic substrates were observed for all Ch-initiated polymers. All LB films showed that Ch of the Ch-initiated homopolymers is able to crystallize. This strong tendency of self-aggregation then triggers further dewetting effects of the respective polyether entities. Fingerlike morphologies are observed for Ch-lPEG(69), since the lPEG(69) entity is able to undergo crystallization after transfer onto the silicon substrate.     

生色冠醚研究 I: 双偶氮开链冠醚的合成和与金属离子的配位性能

本文用邻苯二酚经过先桥接后偶联,用愈创木酚,水杨醛经过先偶联后桥接的方法,合成了三类双偶氮开链冠醚1,2和3.方法简便,产率较高,借助于可见光谱测定,考查了它们在溶液中与碱金属和碱士金属盐等的配位性能.结果表明,1在95:5四氢呋喃-水(v/v)中,对高氯酸锂和高氯酸钙有良好的选择性变色作用.本文对变色作用的反应机理进行了详细的讨论.可以认为,变色作用的产物是分子内配盐,这已由1与高氯酸钙制成的配合物的元素分析,可见光谱和红外光谱的测定所证明.     

Synthesis of chromogenic crown ethers and liquid—liquid extraction of alkaline earth metal ions

New crown ether dyes carrying two pendent anionic side-arms were synthesized for the extraction-spectrophotometry of alkaline earth metal ions. In the extraction of alkaline earth metal ions by these dianionic reagents, size recognition by the crown ether ring was more remarkable than in the case of alkali metal ion extraction by a similar type of monoanionic reagents. Dramatic changes in metal selectivity were observed when the nature of the anionic side-arm was changed while the crown ether skeleton was kept the same. The structure/selectivity relationship is discussed in terms of “chelate” and “intramolecular ion-pair” formation. Typically, when the basicity of the pendent anions was relatively high and a six-membered chelate was structurally possible for the pendent anions and the crown-bound metal, the extraction of calcium was favored by up to a factor of 3000 in the ratio of the Ca/Ba extraction constants for reagents of the diaza-18-crown-6 type. In contrast, the reagents which had pendent anions with only poor coordination ability for metal ions seemed to form complexes of the ion-pair type, and calcium ion was 10⁵ times less extractable than barium ion for the same diaza-18-crown-6-skeleton. Strontium ion seemed to be extracted most effectively when the extracted complex assumed properties intermediate between the chelate and intramolecular ion-pair.     

含硫氮杂套索冠醚的合成及应用研究

合成了一系列分别带有香豆素基和α—萘胺基套索冠醚，用紫外光谱法测定了 这些套索冠醚与Cu^2+，Pb^2+，Cd^2+，Hg^2+，Cr^3+，Ni^2+，Mg^2+，Zn^2+金属 离子的络合作用，及所形成络合物的λmax及摩尔消光系数ε，发现其中一些化合 物对Pb^2+，Hg^2+，Cr^3+金属离子具有较高的灵敏度和选择性．