Size Of Macrocyclic Cavity Research Articles

Precision ion separation via self-assembled channels

Selective nanofiltration membranes with accurate molecular sieving offer a solution to recover rare metals and other valuable elements from brines. However, the development of membranes with precise sub-nanometer pores is challenging. Here, we report a scalable approach for membrane fabrication in which functionalized macrocycles are seamlessly oriented via supramolecular interactions during the interfacial polycondensation on a polyacrylonitrile support layer. The rational incorporation of macrocycles enables the formation of nanofilms with self-assembled channels holding precise molecular sieving capabilities and a threshold of 6.6 ångström, which corresponds to the macrocycle cavity size. The resulting membranes provide a 100-fold increase in selectivity for Li+/Mg2+ separation, outperforming commercially available and state-of-the-art nanocomposite membranes for lithium recovery. Their performance is further assessed in high-recovery tests under realistic nanofiltration conditions using simulated brines or concentrated seawater with various Li+ levels and demonstrates their remarkable potential in ion separation and Li+ recovery applications.

DFT studies on the structure and stability of tetraaza macrocyclic nickel(II) complexes containing dicarbinolamine ligand moiety

Density functional theory calculations at M052X/6-311++G** level were performed to understand the structure and stability of Ni(II) tetraaza macrocyclic dicarbinolamine complex 1. The preferential stability of 1 over the hitherto unknown Ni(II) complex having fully conjugated macrocyclic ligand 2, is examined by analyzing geometric and electronic structures and energy considerations. The present calculations predict that in the trans (C2) structure, 1 is 102 kcal/mol more stable than its components 2 and 2(OH) at M062X-D3/def2-QZVP//M052X/6-311++G** level. This significant stabilization explains the formation of 1 as experimentally observed. The calculations support a distorted square planar environment for Ni in 1, in agreement with the observed spectral and magnetic properties. In order to understand the stability of 1, we examined the second-order stabilizing interactions in natural bond orbital (NBO) basis, the role of the noncovalent dispersion energy, macrocyclic cavity size, Ni-ligand covalent bond strength, natural electronic population on the atomic centers and the nature of the frontier molecular orbitals in the complexes. The present study reveals that the higher stability of 1 over 2 is primarily due to the stronger covalent bonds between the Ni(II) centre, and two of the coordinating nitrogen atoms in 1 than in 2 and significant second-order stabilizing interactions originating from the NBOs involving the oxygen atoms. Density functional theory calculations at M052X/6-311++G** level explains the structure and stability of Ni(II) tetraaza macrocyclic dicarbinolamine complex.

Selective Interactions of Cyclodextrins with Isomeric 1,2,4-Thiadiazole Derivatives Displaying Pharmacological Activity: Spectroscopy Study

Complex formation of α-, β- and γ-cyclodextrins with 1,2,4-thiadiazole derivatives, which are structural isomers displaying an activity in the treatment of Alzheimer’s disease, was examined by the use of 1H NMR and UV-spectroscopy. Stability constants of the complexes formed between cyclodextrins and thiadiazoles in two different buffers (pH 1.2 and 7.4) were calculated and analyzed. The temperature dependences of the stability constants were used to evaluate the enthalpy and entropy changes of complex formation. It was demonstrated that selectivity of the interactions between cyclodextrins and isometric 1,2,4-thiadiazole derivatives is determined by the size of macrocyclic cavity and relative position of the side groups in the benzene ring of the guest molecules. Higher stability of the complexes in the acidic medium (pH 1.2) in comparison with the slightly alkaline solution (pH 7.4) is caused by the important role of surface interactions.

Structural Control of Kinetics for Macrocycle Threading by Fluorescent Squaraine Dye in Water.

While the general concept of steric speed bumps has been demonstrated in rotaxane shuttles and macrocycle threading systems, the sensitivity of speed bump effects has not been evaluated as a function of structural geometry. Values of Ka and kon for macrocycle threading in water are reported for a series of homologous squaraine dyes with different substituents (speed bumps) on the flanking chains and two macrocycles with different cavity sizes. Sensitivity to a steric speed bump effect was found to depend on (a) structural location, being lowest when the speed bump was near the end of a flanking chain, and (b) macrocycle cavity size, which was enhanced when the cavity was constricted. This new insight is broadly applicable to many types of molecular threading systems.

Macrocyclic Platforms for the Construction of Tetranuclear Oxo and Hydroxo Zinc Clusters

The design of ligands that can act as platforms for the controlled, “bottom-up” synthesis of transition-metal clusters is a promising approach to accessing enzymatic mimics and new small-molecule reaction chemistry. This approach is exemplified here through the coordination chemistry of two compartmental Schiff-base calixpyrroles (H4L) that usually act as dinucleating ligands for transition metals. While reactions between H4L and Zn{N(SiMe3)2}2 form the expected dinuclear Zn “Pacman” complexes Zn2(L), reactions with ZnEt2 result in the tetranuclear Zn alkyl complexes Zn4Et4(THF)4(L), in which open, “bowl-shaped” structures are adopted due to the flexibility of the macrocyclic platform. The outcome of hydrolysis reactions of these tetranuclear complexes is found to depend on the macrocyclic cavity size, with the smaller macrocycle favoring oxo formation in Zn4(μ4-O)Et2(L) and the larger macrocycle favoring complete hydrolysis to form the hydroxide-bridged cluster Zn4(μ2-OH)4(L). This latter complex reacts ...

Synthesis and comparative biological evaluation of bifunctional ligands for radiotherapy applications of 90Y and 177Lu

Zevalin® is an antibody-drug conjugate radiolabeled with a cytotoxic radioisotope (90Y) that was approved for radioimmunotherapy (RIT) of B-cell non-Hodgkin’s lymphoma. A bifunctional ligand that displays favorable complexation kinetics and in vivo stability is required for effective RIT. New bifunctional ligands 3p-C-DE4TA and 3p-C-NE3TA for potential use in RIT were efficiently prepared by the synthetic route based on regiospecific ring opening of aziridinium ions with prealkylated triaza- or tetraaza-backboned macrocycles. The new bifunctional ligands 3p-C-DE4TA and 3p-C-NE3TA along with the known bimodal ligands 3p-C-NETA and 3p-C-DEPA were comparatively evaluated for potential use in targeted radiotherapy using β-emitting radionuclides 90Y and 177Lu. The bifunctional ligands were evaluated for radiolabeling kinetics with 90Y and 177Lu, and the corresponding 90Y or 177Lu-radiolabeled complexes were studied for in vitro stability in human serum and in vivo biodistribution in mice. The results of the comparative complexation kinetic and stability studies indicate that size of macrocyclic cavity, ligand denticity, and bimodality of donor groups have a substantial impact on complexation of the bifunctional ligands with the radiolanthanides. The new promising bifunctional chelates in the DE4TA and NE3TA series were rapid in binding 90Y and 177Lu, and the corresponding 90Y- and 177Lu-radiolabeled complexes remained inert in human serum or in mice. The in vitro and in vivo data show that 3p-C-DE4TA and 3p-C-NE3TA are promising bifunctional ligands for targeted radiotherapy applications of 90Y and 177Lu.

Cyclodextrins adsorbed onto activated carbons: Preparation, characterization, and effect on the dispersibility of the particles in water

We have investigated the adsorption equilibrium of selected cyclodextrins onto activated carbons. A number of parameters were examined including the type of carbon material, the size of macrocyclic cavity, and the chemical nature of the oligosaccharide (e.g., neutral, anionic, or cationic cyclodextrin). Adsorption isotherm studies revealed that the maximum amount of cyclodextrin immobilized on the carbon surface is obtained for the native β-CD, while the adsorption capacity of the ionic cyclodextrins derivatives strongly depends on the net surface charge of the activated carbon. The affinity of cyclodextrins for activated carbons was further utilized to prepare modified activated carbons containing controlled amounts of cyclodextrins through an adsorption process. The resulting materials were characterized by N2 adsorption–desorption volumetric measurements, FTIR and Raman spectroscopy, while the quantitative determination of the oligosaccharide content on activated carbons was performed by gravimetric measurements. On the basis of the Turbiscan results, it was found that the chemical structure of cyclodextrins, which are incorporated in the carbon framework, had significant influence on the dispersibility and stabilization of the solid particles in water. Agglomeration and precipitation of the carbon particles were markedly suppressed with substituted cyclodextrins whose hydroxyl groups were partially substituted by methyl or alkylammonium groups.

Theoretical Study of Alkali Metal Complexes of Porphyrin (М2Р), Porphyrazine (М2Рz) and Phthalocyanine (М2Рc), М=Li, Na, K

The information about geometrical and electronic structure of free molecules M 2 Pz, Na 2 Pc, K 2 Pc is not available. The data concerning structure of Li 2 P complex are not definite. The electronic spectra of M 2 P, M 2 Pz, Na 2 Pc and K 2 Pc are not reported. Here the systematic study of the electronic and geometrical structures of M 2 P, M 2 Pz and M 2 Pc complexes is performed. Density functional theory (three-parameter hybrid functional B3LYP), MollerPlesset perturbation theory (MP2) and correlation-consisted valence triple-zeta basis sets (cc-pvtz) are used. All calculations are carried out using PC GAMESS program. For all molecules several geometrical configurations with different positions of alkali atoms relatively the macrocycle plane are optimized. The structures with alkali atoms adjacent to the same side of the macrocycle (C 2v symmetry) and with alkali atoms lying inside of the macrocycle (D 2h ) correspond to saddle points on PES and possess high relative energies (>150 kJ/mol). More energetically favourable configuration of all complexes excepting Li 2 P possesses D 4h symmetry with alkali atoms taking up symmetrical positions at different sides of the macrocycle. According to B3LYP method the equilibrium structure of Li 2 P is the C 2h geometry originating from distorted D 4h configuration. However MP2 calculation leads to the conclusion about D 4h symmetry of equilibrium structure. Perhaps more sophisticated calculations are needed to determine shape equilibrium configuration in the case of Li 2 P. Analysis of all trends is performed for D 4h configuration and is based on the data obtained at B3LYP level. The geometrical parameters of the macrocycle change systematically in the line Li 2 L → Na 2 L → K 2 L (L=P, Pz, Pc): R e (N-C α ) and ϕ e (C α NC α ) increase by ~0.01 A and ~2o, respectively; R e (C α C β ) decreases by ~0.01 A. R e (C α -X m ) value and the macrocycle cavity size (R e (N⋅⋅⋅N)) increase by 0.011÷0.016 A and 0.11÷0.15 A, respectively. R e (Li-Li) does not change practically in the row Li 2 P → Li 2 Pz → Li 2 Pc (increasing 0.006A). Unlike the R e (Li-Li) trend the magnitudes of R e (Na-Na) and R e (K-K) distances in the similar rows increase by 0.134 and 0.249 A. Perhaps, so different trends can be explained by decreasing of the macrocycle cavity size in M 2 P → M 2 Pc → M 2 Pz line and increasing of the alkali atom radius. Natural net charges on the alkali atoms in all studied compounds are situated in the small range 0.90 ÷ 0.96 ē. Extra negative charge (~2ē) of the macrocycle is located on four pyrrol cycles in M 2 P complexes or on four nitrogen meso-atoms in M 2 Pc and M 2 Pz complexes. According to NBO analysis the bond orders of M-M and М-N are close to zero. Thus the М-N bond is ionic bond. The

CMPO-calix[4]arenes and the influence of structural modifications on the Eu(III), Am(III), Cm(III) separation

The syntheses of new calix[4]arenes featuring CMPO groups on the wide rim are reported and the extraction of Am(III) and Eu(III) from concentrated HNO3 aqueous phases are discussed with reference to the properties of the symmetric tetra-CMPO derivative 1 . All extraction studies were conducted in the same experimental conditions which allows to directly compare the dependence of the distribution coefficients of various calixarenes on the acid concentration (0.1 M < [HNO3] < 5 M). Calix[4]arene 1 becomes a very poor extractant if the length of the aliphatic chain between the amide and phosphine oxide groups of CMPO is increased, if the bridging methylene groups are replaced by sulfur atoms or if the macrocyclic cavity size is increased. By contrast, mixed amide — CMPO calix[4]arenes are nearly as effective than 1 . Moreover, Am(III)/Cm(III) separation coefficients between 1.5 and 3 have been obtained with unsymmetrical calix[4]arenes of type 1 with different aliphatic chains grafted on the narrow rim. Guidelines to anticipate the extraction ability of calix[4]arenes remain elusive because of the intricate solution behavior of these compounds.

New dioxadiaza- and trioxadiaza-macrocycles containing one dibenzofuran unit with two amino pendant arms: synthesis, protonation and complexation studies

New dioxadiaza- and trioxadiaza-macrocycles containing one rigid dibenzofuran unit (DBF) and N-(2-aminoethyl) pendant arms were synthesized, N,N'-bis(2-aminoethyl)-[17](DBF)N(2)O(2) (L(1)) and N,N'-bis(2-aminoethyl)-[22](DBF)N(2)O(3) (L(2)), respectively. The binding properties of both macrocycles to metal ions and structural studies of their metal complexes were carried out. The protonation constants of both compounds and the stability constants of their complexes with Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Pb(2+) were determined at 298.2 K, in aqueous solutions, and at ionic strength 0.10 mol dm(-3) in KNO(3). Mononuclear complexes with both ligands were formed, and dinuclear complexes were only found for L(2). The thermodynamic binding affinities of the metal complexes of L(2) are lower than those of L(1) as expected, but the Pb(2+) complexes of both macrocycles exhibit close stability constant values. On the other hand, the binding affinities of Cd(2+) and Pb(2+) for L(1) are very high, when compared to those of Co(2+), Ni(2+) and Zn(2+). These interesting properties were explained by the presence of the rigid DBF moiety in the backbone of the macrocycle and to the special match between the macrocyclic cavity size and the studied larger metal ions. To elucidate the adopted structures of complexes in solution, the nickel(II) and copper(II) complexes with both ligands were further studied by UV-vis-NIR spectroscopy in DMSO-H(2)O 1 : 1 (v/v) solution. The copper(II) complexes were also studied by EPR spectroscopy in the same mixture of solvents. The crystal structure of the copper complex of L(1) was also determined. The copper(II) displays an octahedral geometry, the four nitrogen atoms forming the equatorial plane and two oxygen atoms, one from the DBF unit and the other one from the ether oxygen, in axial positions. One of the ether oxygens of the macrocycle is out of the coordination sphere. Our results led us to suggest that this geometry is also adopted by the Co(2+) to Zn(2+) complexes, and only the larger Cd(2+) and Pb(2+) manage to form complexes with the involvement of all the oxygen atoms of the macrocyclic backbone.

13- and 14-membered macrocyclic ligands containing methylcarboxylate or methylphosphonate pendant arms: Chemical and biological evaluation of their 153Sm and 166Ho complexes as potential agents for therapy or bone pain palliation

The stability constants of La 3+, Sm 3+ and Ho 3+ complexes with 13- and 14-membered macrocycles having methylcarboxylate (trita and teta) or methylphosphonate (tritp and tetp) arms were determined. All the ligands were labelled with 153Sm and 166Ho in order to evaluate the effect of the macrocyclic cavity size and type of appended arms on their in vitro and in vivo behaviour. The radiolabelling efficiency was found to be higher than 98% for all the complexes, except for those of tetp. All radiocomplexes studied are hydrophilic with an overall negative charge and low plasmatic protein binding. Good in vitro stability in physiological media and human serum was found for all complexes, except the 153Sm/ 166Ho–teta, which are unstable in phosphate buffer (pH 7.4). In vitro hydroxyapatite (HA) adsorption studies indicated that 153Sm/ 166Ho–tritp complexes bind to HA having the 166Ho complex the highest degree of adsorption (>80%, 10 mg). Biodistribution studies in mice demonstrated that 153Sm/ 166Ho–trita complexes have a fast tissue clearance with more than 95% of the injected activity excreted after 2 h, value that is comparable to the corresponding dota complexes. In contrast, the 153Sm–teta complex has a significantly lower total excretion. 153Sm/ 166Ho–tritp complexes are retained by the bone, particularly 166Ho–tritp that has 5–6% (% I.D./g) bone uptake and also a high rate of total excretion. Thus, these studies support the potential interest of 153Sm/ 166Ho–trita complexes for therapy when conjugated to a biomolecule and the potential usefulness of the 166Ho–tritp complex in bone pain palliation.

Anion Recognition by Neutral Macrocyclic Amides

Although amides often serve as anchoring groups in natural and synthetic anion receptors, the structure-affinity relationship studies of amide-based macrocyclic receptors are still very limited. Therefore, we decided to investigate the influence of the size of the macroring on the strength and selectivity of anion binding by uncharged, amide-based receptors. With this aim, we synthesized a series of macrocyclic tetraamides derived from 2,6-pyridinedicarboxylic acid and aliphatic alpha,omega-diamines of different lengths. X-ray analysis shows that all ligands studied adopt expanded conformations in the solid state with the convergent arrangement of all four hydrogen-bond donors. 1H NMR titrations in DMSO solution revealed a significant effect of the ring size on the stability constants of anion complexes; the 20-membered macrocyclic tetraamide 2 is a better anion receptor than its both 18- and 24-membered analogues. This effect cannot be interpreted exclusively in terms of matching between anion diameter and the size of macrocyclic cavity, because 2 forms the most stable complexes with all anions studied, irrespective of their sizes. However, geometric complementarity manifests in extraordinarily high affinity of 2 towards the chloride anion. The results obtained for solutions were interpreted in the light of solid-state structural studies. Taken together, these data suggest that anion binding by this family of macrocycles is governed by competitive interplay between their ability to adjust to a guest, requiring longer aliphatic spacers, and preorganization, calling for shorter spacers. The 20-membered receptor 2 is a good compromise between these factors and, therefore, it was selected as a promising leading structure for further development of anion receptors. Furthermore, the study of an open chain analogue of 2 revealed a substantial macrocyclic effect. X-ray structure of the acyclic model 14 suggests that this may be due to its ill-preorganized conformation, stabilized by two intramolecular hydrogen bonds.

Lanthanide complexes of macrocyclic derivatives useful for medical applications

Abstract The protonation constants of two series of tetraazamacrocyclic ligands with acetate and methylphosphonate pendant arms, as well as their stability constants with Cu2+, La3+, Sm3+, and Ho3+, were determined. All the values were determined in aqueous solution at 298.0 K and 0.10 mol dm–3 in N(CH3)4NO3. In the first series, the effect of both types of pendant arms was observed by appending them in the same macrocyclic backbone, a 14-membered tetraazamacrocycle containing pyridine (ac3py14, p2py14, and p3py14). In the second series, two effects were taken into account, the increase of the cavity size of the macrocycle, from 12- to 14-membered, and the appending of acetate (dota, trita, and teta) or methylphosphonate (dotp, tritp, and tetp) arms. The ligands containing methylphosphonate arms have higher thermodynamic stability compared to the corresponding ones with acetate arms, especially in the series of compounds containing pyridine, even upon correction of the different basicity values of the ligands. On the other hand, the ligands with smaller macrocyclic cavity size, namely, dota and dotp, exhibit the largest values of stability constants. In contrast, ac3py14 presents low stability constants with lanthanides. An interpretation of these features based on the known adopted arrangement of dota and teta when free or coordinated with lanthanides is evaluated.

X-Ray diffraction and molecular mechanics studies of 12-, 13-, and 14-membered tetraaza macrocycles containing pyridine: effect of the macrocyclic cavity size on the selectivity of the metal ion

The single crystal structures of complexes [CuL1Br]ClO41, [CuL2Br]PF62, and [NiL2][ClO4]23 were determined (L1 is 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene and L2 is 3,6,10,16-tetraazabicyclo[10.3.1]hexadeca-1(16),12,14-triene). The asymmetric unit of 1 contains two [CuL1Br]+ cations having different five-co-ordinated environments. One (A) exhibits a distorted square pyramidal arrangement, with the basal plane defined by three nitrogen atoms of the macrocycle and the bromine, and the apical position occupied by the nitrogen opposite to the pyridine ring. In the other (B) the donor atoms are distorted from this geometry towards a trigonal bipyramid with the equatorial plane formed by two nitrogen atoms of the macrocycle and Br, and the axial positions occupied by the nitrogen atoms contiguous to the pyridine ring. The complex cation [CuL2Br]+2 exhibits a distorted square pyramidal environment with the basal plane defined by the four nitrogen atoms of the macrocycle and the apical co-ordination by the bromine atom. In [NiL2]2+3 the four nitrogen atoms of the macrocycle form a distorted square planar environment around the nickel centre. Molecular mechanics calculations are used to determine the best-fit sizes for metal ions accommodated into L1 and L2 by evaluation of all sterically allowed conformers for five-co-ordination geometry. The results obtained, together with those of L3 (3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene), published previously, clearly establish the effect of macrocyclic cavity size on metal ion selectivity. These macrocycles prefer a planar conformation to accommodate small metal ions but folded conformations are preferred for longer M–N distances. The increase of the macrocyclic cavity size leads to an increase of the M–N(sp3) distances at which the folded conformer(s) become the most stable form: 1.90, 2.14 and 2.18 A for 12-, 13- and 14-membered macrocycles, respectively.

The Remarkable Structural Diversity of Alkali Metal Pyridine-2-thiolates with Mismatched Crown Ethers

A rich diversity of structural motifs have been uncovered in a family of crown-ether-coordinated alkali metal pyridine-2-thiolates, featuring a templated dimer and polymer (depicted below), an asymmetrically coordinated monomer, and an unprecedented separated ion quadruple with two unusual sodium metalates. Crown ether/alkali metal pairings based on a mismatch between macrocycle cavity size and cationic radius can have profound consequences for the solid-state structural chemistry of the product.

Anion Selective Recognition and Sensing by Novel Macrocyclic Transition Metal Receptor Systems. 1H NMR, Electrochemical, and Photophysical Investigations

A series of novel redox-active and photoactive ruthenium(II) and osmium(II) bipyridyl-, ferrocene-, and cobaltocenium-containing macrocyclic receptors with the dual capability of selectively sensing anionic guest species via electrochemical and optical methodologies have been prepared. Single-crystal X-ray structures of 7·Cl-, 7·2Br-, and 13·2OAc- highlight the importance of hydrogen bonding and respective macrocyclic cavity size to the anion recognition process in the solid state. Proton NMR titration studies in deuterated DMSO solutions reveal these receptors form strong and remarkably selective complexes with Cl-, H2PO4-, and OAc- anions dependent upon the flexibility, topology, and size of the receptor cavity. Cyclic and square-wave voltammetric investigations have demonstrated these receptors to electrochemically recognize Cl-, H2PO4-, and OAc- anions. Photophysical studies reveal emission spectral recognition of Cl- in acetonitrile solutions is displayed by 7−12. With the hetero-dinuclear receptors 8, 9, and 12, the rate constants of the energy transfer process responsible for the quenching of the luminescent ruthenium excited state significantly decreased in the presence of chloride anion.

Polymeric and immobilized crown compounds, material for ion separation

We describe the synthesis of ionoselective polymers bearing different pendant crown ethers. The synthesis was applied to various macrocycles. We discuss the influence of macrocyclic cavity size and rigidity of the polymers on the extraction behavior. Accessibility of active sites can be achievied with immobilized functionalized polyurethanes chemically bound to an inorganic solid support, with no change of ionoselective properties.

Acidity Constants, Dioxygen Affinity, UV–Visible, ESR, and Electrochemical Studies of Some Cobalt(II) (N- or C-Monosubstituted) Tetraazamacrocycles Complexes: Development of an Electrochemical Dioxygen Generator

The use of Cobalt(II)-(N- or C-monosubstituted)-tetraazamacrocycle complexes as potential dioxygen carriers is studied. The physicochemical properties (pKa, half lifetime of the oxygenated complex, dioxygen affinity, redox potentials) depend on the macrocyclic cavity size and on the nature and place of the substituent in the macrocycle. A whole range of macrocycles substituted by a pendent arm bearing a terminal amine,o- or m-picolyl, or a terminal carboxylic function have been synthesized. Their studies connected the physicochemical properties of their cobalt complexes with the ring size and the substituent. TheKO2determination, ESR spectra, and electrochemical studies afford particularly important insights into the nature of the dioxygen adduct that is obtained. In order to synthesize a ligand suitable for the development of an industrial electrochemical dioxygen generator, we have undertaken to understand the influence of the pendent arm for substituted macrocycles. Through UV–visible and electrochemical studies, it turns out that macrocycles substituted by functions bearing terminal carboxylic groups exhibit more efficient properties than their parent compounds bearing amine terminated substituents. The redox potential depends more on the size of the macrocycle than on the nature of the substituent, but this influence is reversed within the half lifetime.

Lipophilic polythiamacrocycles as palladium extracting agents

Six new lipophilic thiacrown ethers ( 1 – 6 ), abbreviated as 2-octyl-9S3, 2-octyl-10S3, 2-octyl-12S4, 6-octyl-14S4, 3-octyl-16S4 and dioctyl-18S6, were synthesized starting from different dithiols and dihalides. Cs 2CO 3 is used for the cyclizations. The extraction behavior of palladium (II) from nitric acid media with these reagents in chloroform has been studied in terms of extraction equilibrium constants K ex. The influence of parameters such as lipophilicity brought by alkyl chains, macrocyclic cavity size and number of sulfur donor atoms on the extraction behavior was investigated.

Coordination Compounds of Phosphoryl Containing Pendant Macrocyclic Ligands with Alkali and Transition Metals

Abstract Electroneutral phosphoryl-containing pendant polyaza- macrocycles LI -LIV, proved to be efficient complexing agents for alkali and transition metal ions The ligands involve different coordination sites: the “hard” base, oxygen atoms, and less “hard” nitrogen atoms in aminogroups. The stability constants (K) of [ML]+ complexes (M is “hard” acid Li, Na, K, Cs ions) were detected in the THF. The discrimination coefficients, which characterize the selectivity of ligands, were calculated. The value of K was found to depend on the macrocycle cavity size and the pendant chain length.