Complexation of Macrocyclic Compounds with Nicotinamide in Dimethylsulphoxideand its Water Mixture

The complexation behavior of nicotinamide with macrocyclic polyethers viz, 15-crown-5, benzo-15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dibenzo-24-crown-8, 1,4,7,10,13,16-hexathiacyclooctadecane, monoaza-15-crown-5, 1,4,10-trioxa-7,13-diaza-cyclopentadecane, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane, 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, 1,4,7-tritosyl-1,4,7-triazacyclononane, 1,4,7,10-tetratosyl-1,4,7,10-tetraazacyclododecane and 1,4,8,11-tetraazacyclooctadecane has been studied in dimethylsulphoxide (DMSO) and 90% DMSO + water using differential pulse polarography and complexation constants have been reported. Nicotinamide forms stable complexes with six-membered coronand rings of the crown ethers. The nature of the atoms (oxygen, sulfur and nitrogen) in the coronand ring is observed to affect the stability of the complex. The stoichiometry and stability constants of the complexes were determined by monitoring the shifts in peak potentials of the polarograms of nicotinamide against the ligand concentration. The Gibbs free energy change turns out to be negative at 25°C, which indicates the spontaneity of the binding of nicotinamide with crown ethers. The mole ratio of nicotinamide to the macrocyclic compound was also determined and it was found that the complexes were of 1:1 type with respect to crown ethers. The tendency of nicotinamide to form complexes with macrocycles is found to be greater in DMSO than in DMSO + water.     

Crystal Structure and Properties of a New Copper(II) Complex of Dioxocyclam Appended with 8-Methylquinoline (Dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione)

The IR spectra of the crystalline complexes of 3-and 4-nitrophenol with crown ethers were studied, viz.,18-crown-6 (18C6), benzo-18-crown-6 (B18C6),dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DC18C6) and dibenzo-24-crown-8 (DB24C8). The spectra of uncomplexed crown ethers showed water absorption bands which indicate the presence of two types of bound water molecules, viz., cavitant water enclosed by the strong ether-cavity field and outer-layer hydrogen-bonded water molecules. Upon complexation with 3- and 4-nitrophenol, the bands attributed to cavitant water disappeared, leaving the outer layer water to act as a bridge between the host crown ether and the guest phenols. The results further showed that of the crown ethers and of the phenols, B18C6 and DC18C6 and 3-nitrophenol, have the strongest interaction. The behaviour of the phenols was explained by the increased contribution of the inductive-moment over the resonance -moment in thecomplexes.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.     

Allylation of phenoxides by crown ethers and their polymers

Allylation of sodium phenoxide in the presence of crown ethers produces a high ratio of O/O + C allylation when conducted in water, phenol, benzene, or diethyl ether. The striking increase in the product ratios is attributed to specific complexation of the crown ethers that facilitate the dissociation of the ion pair aggregate of the sodioderivative in benzene or diethyl ether. The crown ethers may act as a phase transfer catalyst when the reaction is run in water. Furthermore, the O/O + C ratios of the allylation strongly depend on the kind of crown ethers used. To examine their effect the allylation of sodium phenoxide was studied with various crown ethers, such as 18-crown-6, benzo-18-crown-6, benzo-15-crown-5, poly(vinylmonobenzo-15-crown-5), and poly(vinylmono-benzo-18-crown-6), as catalysts. It was found that among these crown ethers poly(vinylmono-benzo-15-crown-5) was the most effective catalyst.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.Graphical Abstract Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali CationsYU LIU*, JIAN-RONG HAN, ZHONG-YU DUAN and HENG-YI ZHANG This revised version was published online in July 2005 with a corrected issue number.     

Thermodynamics of Amino Acid Methyl Ester Hydrochlorides—Crown Ether Complexes in Methanol at 25°C

Stability constants, free energies, and enthalpies and entropies of the complexation of L-alanine methyl ester hydrochloride (L-Ala-HCl), L-phenylalanine methyl ester hydrochloride (L-Phe-HCl), and valine methyl ester hydrochloride (L-Val-HCl) with 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), 18-crown-6 (18C6), benzo-18-crown-6 (B18C6), dicyclohexano-18-crown-6 (DC18C6), and dicyclohexano-24-crown-8 (DC24C8) in methanol are reported for 20°C. No significant variation in the stability constants and free energies of complexation is observed, indicating that the various crown ethers are poorly selective in binding the amino acids. However, the nature of the crown ether and the amino acid and their pattern of substitution cause a remarkable variation in the enthalpies and entropies of complexation. This indicates a strong enthalpy–entropy compensation effect. The enthalpy–entropy compensation effect for the crown ether complexes of the amino acid methyl ester hydrochlorides reported herein is compared with that of the crown ethers complexes of the amino alcohols and the free amino acid. It is found that the enthalpy–entropy compensation effect holds equally for the three classes of complexes.     

大环疏水效应: 冠醚在DMF+H2O混合物中的焓对作用

利用等温滴定微量热法测定了298.15 K时12-冠-4、15-冠-5、18-冠-6和4,13-二氮杂-18-冠-6四种冠醚在纯水及不同质量分数(w=0-0.3)的N,N-二甲基甲酰胺(DMF)+H₂O混合物中的稀释焓, 根据McMillan-Mayer理论计算得到相应的焓对作用系数(h_xx). 实验发现, h_xx均为较大的正值, 表明在冠醚-冠醚自相互作用中疏水性成分占绝对优势, 主要表现为两种机制: (1) 当疏水-疏水作用发生时, 共球交盖使得水结构形成减少, 对h_xx有正的贡献; (2) 当疏水-亲水作用发生时, 共球交盖使得水结构破坏增加, 对h_xx有正的贡献. 此外, 四种冠醚h_xx的大小关系为: h_xx(18-冠-6)>h_xx(4,13-二氮杂-18-冠-6)≈h_xx(15-冠-5)>h_xx(12-冠-4), 表明冠醚环越大, 疏水-疏水作用越强, 存在显著的大环疏水效应.     

Extraction of strontium from nitric acid solutions by selected crown ethers

The extraction of Sr from nitric acid solutions by the crown ethers, 12-crown-4, 15-crown-5, 18-crown-6 and DB 18-crown-6 dissolved in chloroform has been investigated. Sr is reasonably well extracted by 18-crown-6 compared to other crown ethers from different nitric acid solutions. The extraction is strongly dependent on the concentration of HNO₃ and nitrate salts. Preliminary studies indicate that¹³⁷Cs is also extracted to a limited extent by 18-crown-6 from nitrate medium. Stripping of Sr was achieved by an aqueous solution of low acidity, the crown ether being regenerated for subsequent extraction.     

Novel C1-symmetric chiral crown ethers bearing rosin acids groups: synthesis and enantiomeric recognition for ammonium salts

Four types of novel C₁-symmetric chiral crown ethers including 28-crown-8, 20-crown-6, 17-crown-5 and 14-crown-3 (9a–m) were synthesized and their enantiodiscriminating abilities with protonated primary amines (10–14) were examined by ¹H NMR spectroscopy. 20-crown-6 crown ethers exhibited good chiral recognition properties toward these guests and showed different complementarity to some chiral guests, indicating that 20-crown-6 crown ethers could be used as a chiral NMR solvating agent to determine the enantiopurity of these guests. In addition, the binding model and binding site between the hosts and guests were also studied by the computational modeling and experimental calculation.     

Temperature and solvent effects on the experimental dipole moments of three crown ethers

Dipole moments of 12-crown-4, 15-crown-5 and 18-crown-6 have been measured for solutions in benzene and in cyclohexane at 15, 20 , 25, and 30°, using the Guggenheim-Smith method. The dipole moments of the more common conformers of these crown ethers have also been calculated. The results indicate that these crown ethers exist in solution as mixtures of conformers. The conformational equilibria shift toward the more polar conformers as temperature increases. There is evidence that the more polar conformers of 12-crown-4 and 15-crown-5 are somewhat more favored in benzene solution than in cyclohexane, possibly as the result of a weak complexation with the former solvent.     

Study of complexation of phenylaza-15-crwon-5, 4-nitrobenzo- 15-crown-5, and benzo-15-crown-5 with Ag+, Tl+ and Pb2+ ions in methanol by competitive potentiometry

The complexation reaction of phenylaza-15-crwon-5, 4- nitrobenzo- 15-crown-5, and benzo-15-crown-5 with Ag⁺, Tl⁺ and Pb²⁺ ions in methanol solution have been studied by a competitive potentiometric method. The Ag⁺/Ag electrode used both as an indicator and reference electrode in a concentration cell. The emf of cell monitored as the crown ethers concentration varies through the titration. The stoichiometry and stability constants of resulting complexes have been evaluated by MINIQUAD. The stoichiometry for all resulting complexes was 1:1. The stability of these metal ions with derivatives of 15-crown-5 are in order phenylaza-15-crown-5 > Benzo-15-crown-5 > 4-nitrobenzo-15-crown-5, and for the each used crown ethers are as Pb²⁺ > Ag⁺ > Tl⁺. The effect of the substituted group on the stability of resulting complexes was considered. The obtained results are novel and interesting.     

Extraction of alkali metal picrates with poly- and bis(crown ether)s

Extraction of alkali metal picrates by new poly- and bis(crown ether)s containing benzo-15-crown-5 and benzo-18-crown-6 moieties was carried out with chloroform as water-immiscible solvent. The poly- and bis(crown ether)s were found to extract the picrates more effectively than the corresponding monocyclic crown ethers. In particular, poly- and bis(benzo-15-crown-5), and bis(benzo-18-crown-6) are remarkably effective extracting reagents for potassium and rubidium, and for caesium, respectively. Extraction equilibrium constants and the complexation constants in the chloroform phase were also evaluated and the contribution of the complexation constants to the extractability is discussed.     

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

Host-guest complexation has demonstrated potential for controlling hybrid organic-inorganic metal halide perovskite materials. In particular, crown ethers have been used due to their capacity to interact with metal cations (e. g., Pb²⁺) and small organic cations (e. g., methylammonium (MA)), which can affect hybrid perovskite materials and their solar cells. However, this strategy has been underexploited in perovskite photovoltaics, and the underlying mechanisms are not well understood. In this study, we investigate the influence of 15-crown-5 ( 15C5 ) and its benzannulated derivative (benzo-15-crown-5, B15C5 ), as well as amino-functionalized analogues (15-crown-5)-2-methylamine, 2A-15C5 , and 4′-aminobenzo-15-crown-5, 4A-B15C5 , on MAPbI₃ perovskite crystallization and inverted solar cell performance. We demonstrate the propensity of crown ether modulators to interact with Pb²⁺ cations at the perovskite interface by density functional theory calculations. This has been shown to facilitate oriented crystal growth and homogeneous film formation, as revealed by X-ray diffraction analysis complemented by scanning electron microscopy. As a result, we demonstrate an increase in the power conversion efficiency of the solar cells of interest to advancing hybrid photovoltaics.     

以2-苯氧乙基为氮支链的[18]和[15]环系氮支套索冠醚的合成及其络合性能

以2-苯氧乙醇为起始剂, 合成了两种新型氮支套索冠醚: N-(2-苯氧乙基)单氮杂-18-冠-6 (18CE)与N-(2-苯氧乙基)单氮杂-15-冠-5 (15CE). 通过红外光谱、核磁共振氢谱和紫外光谱表征了新冠醚及其中间体的结构. 用电导滴定法研究了两冠醚与Na^＋, K^＋, Ag^＋, NH^4＋, Ni^2＋, Cu^2＋, Pb^2＋和Co^2＋在25 ℃的配位作用, 计算了1∶1配合物的稳定常数. 实验结果表明, 由于N-(2-苯氧乙基)引入氮杂冠醚环和参与配位, 18CE和15CE配合物的稳定常数分别比单氮杂-18-冠-6, N-(2-羟基乙基)单氮杂-18-冠-6, N-(2-甲氧基乙基)单氮杂-18-冠-6和单氮杂-15-冠-5, N-(2-甲氧乙基)单氮杂-15-冠-5, N-(2-甲氧乙基)单氮杂-15-冠-5的对应配合物明显提高. 配合物的稳定常数和紫外光谱皆提供了支链的苯氧基参与配位的信息.     

Syntheses and properties of arenediazonium and anilinium cation lariat ether complexes: an “ostrich molecule” complex and evidence for intramolecular sidearm - macroring interaction

The preparation of several novel lariat ethers (macrocyclic crown polyethers having sidearms bearing pendant donor groups) is reported, These compounds are ethers derived from known 2-hydroxymethyl-15-crown-5 or -21-crown-7. The sidearms Include 2-aminophenyl, 2,4-diaminophenyl, 2-nitrophenyl, 2-(3'-nitrobiphenyl), and 2-(3'-aminobiphenyl). In several cases, the amino groups were converted into ammonium salts which showed substantial stabilization by intramolecular hydrogen bonding. Likewise, an -NH₂^+.,BF₃^- complex showed evidence of intramolecular hydrogen bonding. Diazotization of the aminobiphenyl residue produced an arenediazonium cation which underwent intramolecular crown complexation, as judged by infrared spectroscopic studies to form what we call an “ostrich molecule” complex. Addition of N,N-dimethylaniline to the intramolecular arenediazonium cation complex afforded an azo compound, but europium shift reagent studies showed clearly that the diazonium cation reacted outside the macroring.     

Nitro derivatives of <Emphasis Type="Italic">N</Emphasis>-alkylbenzoaza-15-crown-5: synthesis,structures, and complexation with metal and ammonium cations

A number of N-alkylnitrobenzoaza-15-crown-5 with the macrocycle N atom conjugated with the benzene ring were obtained. The structural and complexing properties of these compounds were compared with those of model nitrobenzo- and N-(4-nitrophenyl)aza-15-crown-5 using X-ray diffraction, ¹H NMR spectroscopy, and DFT calculations. The macrocyclic N atom of benzoazacrown ethers are characterized by a considerable contribution of the sp3-hybridized state and a pronounced pyramidal geometry; the crownlike conformation of the macrocycle is preorganized for cation binding, which facilitates complexation. The stability constants of the complexes of crown ethers with the NH₄ ⁺, EtNH₃ ⁺, Na⁺, K⁺, Ca²⁺, and Ba²⁺ ions were determined by 1H NMR titration in MeCN-d₃. The most stable complexes were obtained with alkaline-earth metal cations, which is due to the higher charge density at these cations. The characteristics of the complexing ability of N-alkylnitrobenzoaza-15-crown-5 toward alkaline earth metal cations are comparable with analogous characteristics of nitrobenzo-15-crown-5 and are much better than those of N-(4-nitrophenyl)aza-15-crown-5.     

Formation Constants of Complexes of Monovalent Cations with Benzocrown Ethers in Nitromethane

The complexation reactions between the macrocyclic polyethers dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5 and polyethers bearing a stilbene unit with alkali metal and silver cations have been studied conductometrically in nitromethane. The formation constants of 1 : 1 and 1 : 2 (metal : ligand) complexes were determined and found to decrease with increasing cation diameter. The stability of the stilbene crown – metal cation complexes is lower than for complexes of other investigated crown ethers with analogous cations. There seem to be some effects of double bond-silver ion interactions.     

DFT calculation of benzoazacrown ethers and their complexes with calcium perchlorate

The complexation constants of several azacrown ethers with Ca(ClO₄)₂ were determined and turned out to be the higher, the large the macrocycle. The structures of free ligands and their complexes and the complexation energies were calculated by the DFT method. In the aza-12(15)-crown-4(5) ether complexes with Ca(ClO₄)₂, the metal cations lie outside the averaged plane of heteroatoms of the macrocycle, and the coordination of both counterions is V-like. In the complexes of aza-18-crown-6 ethers, the counterions are in the axial position relatively to the macrocycle in the center of which the Ca²⁺ ion is localized. The complexation energies increase with an increase in the size of the azacrown ether macrocycle. The involvement of the nitrogen atom in binding with the Ca²⁺ ion decreases with the expansion of the macrocycle. Two methods for quantitative estimation of the degree of pre-organization of ligands to complexation were considered: geometric and energetic methods. Benzoaza-15-crown-5 ether is a ligand which is more pre-organized to complexation than N-phenylaza-15-crown-5 ether.     

Two-component polymer films of palladium and fullerene with covalently linked crown ether voids: effect of cation binding on the redox behavior

Redox active films have been generated via electrochemical reduction in a solution containing palladium(II) acetate and fulleropyrrolidine with covalently linked crown ethers, viz., benzo-15-crown-5 and benzo-18-crown-6. In these films, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. Films show ability to coordinate alkali metal cations from the solution. Therefore, in solutions containing salts of alkali metal cations, benzo-15-crown-5-C₆₀/Pd and benzo-18-crown-6-C₆₀/Pd films are doped with cations coordinated by crown ether moiety and anions of supporting electrolyte which enter the film to balance positive charge. These films are electrochemically active in the negative potential range due to the reduction of the fullerene moiety. Reduction of the polymer is accompanied by the transport of supporting electrolyte ions between solution and solid phase. In solution containing alkali metal salts, the process of film reduction is accompanied by the transport of anions from the film to the solution. In the presence of tetra(alkyl)ammonium salts, transport of cations from the solution to the film takes place during the polymer reduction.     

Study of complexation of an ionic liquid inside into crown ethers in aqueous environments by physicochemical techniques

Inclusion complexation between crown ethers (CEs) (viz., 15-crown-5, 18-crown-6) and an ionic liquid (IL) (viz., 1-ethyl-3-methylimidazolium tosylate) in aqueous medium have been demonstrated by conductivity, surface tension and ¹Proton Nuclear Magnetic Resonance (H NMR) study. The results show the formation of 1:1 complexes between CEs and the IL through electron-deficient imidazolium cation and electron pairs of oxygen atoms of the CEs. Hydrogen bonding is the key factor responsible for complexation, while, the ion–dipole interactions also contribute towards the complex formation. The formation constants have been derived from conductivity study and the complexes have been analysed by ¹H NMR study.