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This study focuses on synthesizing and characterizing supramolecular cocrystals derived from 4-cyano-1-methylpyridinium iodide and 18-crown-6. The synthesis employed a solvent evaporation technique, followed by a thorough structural analysis utilizing XRD methods. The compound's purity is confirmed by powder XRD analysis, while single-crystal XRD confirms its triclinic system packing with a centrosymmetric space group ( P 1 ‾ ). The findings unveiled the emergence of unique cocrystals characterized by distinct molecular configurations supported by hydrogen bonding and ion-dipole interactions. Through diffuse reflectance spectral measurements, the direct band gap energy was assessed at 2.36 eV. Thermogravimetric analysis was utilized to evaluate the thermal properties of the compound across varying temperatures. The compound's elemental composition and surface morphology were analyzed through investigations using EDS and SEM. [ABSTRACT FROM AUTHOR]

The title complex, (1,4,7,10,13,16-hexaoxacyclooctadecane-1κ6O)(μ-oxalato-1κ²O¹,O²:2κ²O1′,O2′)triphenyl-2κ³C-potassium(I)tin(IV), [KSn(C6H5)3(C2O4)(C12H24O6)] or K[18-Crown-6][(C6H5)3SnO4C2], was synthesized. The complex consists of a potassium cation coordinated to the six oxygen atoms of a crown ether molecule and the two oxygen atoms of the oxalatotriphenylstannate anion. It crystallizes in the monoclinic crystal system within the space group P21. The tin atom is coordinated by one chelating oxalate ligand and three phenyl groups, forming a cis-trigonal–bipyramidal geometry around the tin atom. The cations and anions form ion pairs, linked through carbonyl coordination to the potassium atoms. The crystal structure features C—H⋯O hydrogen bonds between the oxygen atoms of the oxalate group and the hydrogen atoms of the phenyl groups, resulting in an infinite chain structure extending along a-axis direction. The primary inter-chain interactions are van der Waals forces. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, hexaaquanickel(II) dichloride–1,4,7,10,13,16-hexaoxacyclooctadecane–water (1/2/2), [Ni(H2O)6]Cl2·2C12H24O6·2H2O, is reported. The asymmetric unit contains half of the Ni(OH2)6 moiety with a formula of C12H32ClNi0.50O10 at 105 K and triclinic (P1) symmetry. The [Ni(OH2)6]2+ cation has close to ideal octahedral geometry with O—Ni—O bond angles that are within 3° of idealized values. The supramolecular structure includes hydrogen bonding between the water ligands, 18-crown-6 molecules, Cl− anions, and co-crystallized water solvent. Two crown ether molecules flank the [Ni(OH2)6]2+ molecule at the axial positions in a sandwich-like structure. The relatively symmetric hydrogen-bonding network is enabled by small Cl− counter-ions and likely influences the more idealized octahedral geometry of [Ni(OH2)6]2+.

The title complex, (1,4,7,10,13,16-hexaoxacyclooctadecane-1κ6O)(μ-oxalato-1κ2O1,O2:2κ2O1′,O2′)triphenyl-2κ3C-potassium(I)tin(IV), [KSn(C6H5)3(C2O4)(C12H24O6)] or K[18-Crown-6][(C6H5)3SnO4C2], was synthesized. The complex consists of a potassium cation coordinated to the six oxygen atoms of a crown ether molecule and the two oxygen atoms of the oxalatotriphenylstannate anion. It crystallizes in the monoclinic crystal system within the space group P21. The tin atom is coordinated by one chelating oxalate ligand and three phenyl groups, forming a cis-trigonal–bipyramidal geometry around the tin atom. The cations and anions form ion pairs, linked through carbonyl coordination to the potassium atoms. The crystal structure features C—H...O hydrogen bonds between the oxygen atoms of the oxalate group and the hydrogen atoms of the phenyl groups, resulting in an infinite chain structure extending along a-axis direction. The primary inter-chain interactions are van der Waals forces.

This study utilizes single‐crystal X‐ray diffraction in a diamond anvil cell (DAC) to explore the structural response of [Cs(18‐Crown‐6)][SbCl6] under high pressure (HP). Notably, the pressure drives large Cs atoms closer to the center of the crown ether cavity, ultimately requiring pressures of 3 GPa for its complete encapsulation. Remarkably, the absence of short contacts in the crystal classifies the material as a "loose crystal" offering a unique model for understanding compression mechanisms. The crystal exhibits highly anisotropic compression behavior with an impressive volume reduction and non‐linear pressure – unit‐cell parameters relationships facilitated by the absence of short CH⋅⋅⋅Cl contacts up to 0.9 GPa. Beyond this pressure, steric repulsion due to shortening H⋅⋅⋅Cl and H⋅⋅⋅H interactions hinders further effective compression, so pressure dependence on unit cell parameters and volume becomes more linear. The behavior of [Cs(18‐Crown‐6)][SbCl6] at different conditions was studied using Raman spectroscopy and supplemented by DFT calculations. [ABSTRACT FROM AUTHOR]

Thermal stability of macrocyclic complexes with alkaline earth metal salts is of crucial importance for their applicability as the components of new electrolytes, ionic liquids and precursors in chemical vapor deposition processes. The complexes of 18-crown-6 and stereoisomeric dicyclohexano-18-crown-6 with alkaline earth metal halides were synthesized and studied by the combination of simultaneous DSC/TGA and FTIR-spectroscopy. The stability of these compounds depended on the size of the cation and anion as follows: Ba2+ < Sr2+ < Ca2+ and Cl− < Br− ≈ I−. The two-stage mechanism of destruction was found for the complexes with CaCl2, SrBr2, SrI2. This implies, most probably, the coexistence of two conformationally nonequivalent forms of the macrocycles with different thermal stability rather than the destruction of the macrocycle at high temperatures. The revealed trends, in our opinion, were caused by changes in the interaction energy between macrocycle and metal cation. [ABSTRACT FROM AUTHOR]

N,N'-Di-tert-butyl-carbodi-imide, Me3CN=C=NCMe3, undergoes reductive cleavage in the presence of the GdII complex, [K(18-crown-6)2][GdII(NR 2)3] (R = SiMe3), to form a new type of ligand, the tert-butyl-cyanamide anion, (Me3CNCN)-. This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal containing potassium salts of both end-on and side-on bound tert-butyl-cyanamide anions, (Me3CNCN)-. The crystal contains [K(18-crown-6)(H2O)][NCNCMe3-kN], in which one ( t BuNCN)- anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η2-NCNCMe3], in which an 18-crown-6 potassium is coordinated side-on to the terminal N-C linkage. This single crystal also contains one equivalent of 1,3-di-tert-butyl urea, (C9H20N2O), which is involved in hydrogen bonding that may stabilize the whole assembly, namely, aqua-(tert-butyl-cyanamidato)(1,4,7,10,13,16-hexa-oxa-cyclo-octa-deca-ne)potas-sium(I)-(tert-butyl-cyanamidato)(1,4,7,10,13,16-hexa-oxa-cyclo-octa-deca-ne)potas-sium(I)-N,N'-di-tert-butyl-carbodi-imide (1/1/1) [K(C5H9N2)(C12H24O6)]·[K(C5H9N2)(C12H24O6)(H2O)]·C9H20N2.

Kinetic and energy characteristics of reversible intermolecular processes for [Pr(DPM)3], [Pr(DPM)3(18-crown-6)], and [(Pr(DPM)3)2(18-crown-6)] complexes in the CDCl3 solution (DPM=dipivaloylmethane anion) are characterized by dynamic 1H NMR. [ABSTRACT FROM AUTHOR]

To date, the world has accumulated a large amount of long-lived radioactive materials that need to be disposed of or reprocessed. Such materials include nuclear legacy objects containing 226Ra, which is an important material for obtaining a wide range of isotopes for nuclear medicine via irradiation in reactors, cyclotrons, and electron accelerators. For the selective recovery of 226Ra from waste materials, crown-ether (CE) 18-crown-6 (18C6) or its derivatives can be used, which, however, have not been widely studied for these purposes. In our work, the key property of 18C6 and its derivatives, the phase distribution, was studied using tritium labeling. The possibility of introducing a tritium label into CEs molecules using thermal activation of tritium has been demonstrated; a high specific activity of the obtained compounds was achieved (from 18 to 108 TBq/mol). Methods for chromatographic purification of the studied CEs were developed. The distribution of 18C6 and its derivatives between various organic solvents and water was studied in detail for the first time. Subsequently, the obtained data will allow us to choose conditions for the selective recovery of 226Ra from aged sources. [ABSTRACT FROM AUTHOR]

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We have investigated the behaviour of change of molar conductivity of mixtures of two crown ethers (CE) (18-Crown-6; 18C6 and 24-Crown-8; 24C8) and metal ions (Mn+) (Zn2+ and Cu2+) and the complexation between CE and Mn+ in water + acetonitrile binary solvent system (20, 40, 60 and 80%; v/v) at 298.15 K to 328.15 K by conductometric technique. Kf values for all complexes were found to be decreased with enhancement of temperature. Complexes associated with Zn2+ exhibit a trend of Kf: 24C8 + Zn2+ > 18C6 + Zn2+ in 20% solvent composition (water-acetonitrile) and order of 18C6 + Zn2+ > 24C8 + Zn2+ was found for 80% solvent composition. However, logarithm values of Kf for the Cu2+ complexes were found to obey the order of 24C8 > 18C6 almost for all compositions except with a few exceptions. Δ G o was found to be negative indicating spontaneous complexation between CE and Mn+. [ABSTRACT FROM AUTHOR]

81,82mRb and trace amount 44mSc were produced by irradiation of potassium bromide target with 36 MeV alpha particle beam via natBr(α,xn)81,82mRb and 41K(α,n)44mSc reactions respectively. Different liquid–liquid extraction (LLX) studies were performed to determine best separation condition for Rb and Sc. In LLX (1) cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane, (2) 18-crown-6 in nitrobenzene were used as organic phase and various concentration of HCl, HNO3 and HClO4 were used as aqueous phase. Radiochemical separation with high separation factor has been achieved. [ABSTRACT FROM AUTHOR]

The conductometric study of ligand structure influence on the Pb(II) complexation with crown ethers in different solvents has been investigated. In this paper, the complexation reaction of macrocyclic ligand, 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), and Pb(II) cation was studied in different solvents: dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE). The effects of surfactant structure (Triton X-100 and Triton X-45) on the conductivity of the Pb(II) complex with 18-crown-6 and dibenzo-18-crown-6 ether have been investigated. The conductance data showed that the stoichiometry of the complexes in most cases is 1:1(ML). It is also demonstrated that the influence of crown ethers is deeply affected by the organic solvent used. In the solvents studied, the stability of the resulting complexes showed higher stability in dichloromethane comparing with 1,2- dichloroethane. Macrocyclic ligand 18-crown-6 showed more suitable for complexation of Pb(II) ions compared to dibenzo-18-crown-6. Adding a surfactant affected the higher absolute values of the conductivity of systems, but not the change in the stoichiometric ratio between a metal ion and macrocyclic ligand.

N,N′-Di-tert-butylcarbodiimide, Me3CN=C=NCMe3, undergoes reductive cleavage in the presence of the GdII complex, [K(18-crown-6)2][GdII(NR2)3] (R = SiMe3), to form a new type of ligand, the tert-butylcyanamide anion, (Me3CNCN)−. This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal containing potassium salts of both end-on and side-on bound tert-butylcyanamide anions, (Me3CNCN)−. The crystal contains [K(18-crown-6)(H2O)][NCNCMe3-kN], in which one (tBuNCN)− anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η2-NCNCMe3], in which an 18-crown-6 potassium is coordinated side-on to the terminal N—C linkage. This single crystal also contains one equivalent of 1,3-di-tert-butyl urea, (C9H20N2O), which is involved in hydrogen bonding that may stabilize the whole assembly, namely, aqua(tert-butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)–(tert-butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)–N,N′-di-tert-butylcarbodiimide (1/1/1) [K(C5H9N2)(C12H24O6)]·[K(C5H9N2)(C12H24O6)(H2O)]·C9H20N2.

Theoretical study of the electronic structure, NonLinear Optical (NLO) properties, and natural bonding orbital (NBO) analysis of 18-crown-6were investigated using Density Functional Theory DFT) calculations at the B3LYP/6-311G (d,p) level of theory. The optimized structure is a nonlinear compound indicated from the dihedral angles. Natural bonding orbital analysis has been analyzed in terms of the hybridization of each atom, natural charges (Core, Valence, and Rydberg), bonding and antibonding orbital's second-order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the title molecule can be used to explain the charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), softness(S), global electrophilicity index (w), and electronegativity (χ). The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα), first-order hyperpolarizability (βtot) and third-order hyperpolarizability ⟨γ⟩), of the studied molecule have been calculated at the same level of theory.The Molecular Electrostatic Potential (MEP) and ElectroStatic Potential (ESP) for the title molecule were investigated and analyzed. Also, the electronic absorption spectra were discussed by time-dependent density functional theory (TD-DFT) calculations in ethanol and water solvents. From the experimental conductance measurements, the association thermodynamic parameters (KA, ∆GA, ∆HA, and ∆SA) and complex formation thermodynamic parameters (Kf, ∆Gf, ∆Hf, and ∆Sf) of nano-CuSO4 in presence of 18-crown-6 as a ligand in 10% ethanol-waterer solvents at different temperatures (298.15, 303.15, 308.15 and 313.15K) were applied and calculated.

The title complex, (1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-1κ 6 O )(μ-oxalato-1κ 2 O 1 , O 2 :2κ 2 O 1' , O 2' )triphenyl-2κ 3 C )] or K[18-Crown-6][(C 6 H 5 ) 3 (C 2 O 4 )(C 12 H 24 O 6 )] or K[18-Crown-6][(C 6 H 5 ) 3 SnO 4 C 2 ], was synthesized. The complex consists of a potassium cation coordinated to the six oxygen atoms of a crown ether mol-ecule and the two oxygen atoms of the oxalatotri-phenyl-stannate anion. It crystallizes in the monoclinic crystal system within the space group P 2 1 . The tin atom is coordinated by one chelating oxalate ligand and three phenyl groups, forming a cis -trigonal-bipyramidal geometry around the tin atom. The cations and anions form ion pairs, linked through carbonyl coordination to the potassium atoms. The crystal structure features C-H⋯O hydrogen bonds between the oxygen atoms of the oxalate group and the hydrogen atoms of the phenyl groups, resulting in an infinite chain structure extending along a -axis direction. The primary inter-chain inter-actions are van der Waals forces., (© Song et al. 2024.)

The iodido bismuthates [Bi(18-crown-6)I2][BiI4] (1) and [Bi(18-crown-6)I2][Bi3I10] (2), the neutral complex [Bi(C6H14O4)I3](18-crown-6) (3) as well as the polyiodides [Bi(18-crown-6)I2][I5](18-crown-6) (4), [Bi(18-crown-6)I2]2[I14] (5) and [Bi(18-crown-6)I2]2[I19] (6) were prepared by reaction of BiI3, 18-crown-6, and I2 at T = 60–120 °C. The compounds 1–5 were prepared in [n-Bu3MeN][N(Tf)2] as an ionic liquid ([n-Bu3MeN]: tributylmethylammonium, [N(Tf)2]: bis(trifluoromethylsulfonyl)imide), whereas 6 was obtained only by direct reaction of the starting materials. The title compounds exhibit two different constitutions of the [Bi(18-crown-6)I2]+ cation as well as a non-charged, molecular [Bi(C6H14O4)I3] unit with a triethylene glycol ligand generated in situ by cleavage of the crown ether. Infinite chain-like [ BiI 2 / 1 I 4 / 2 ] − ∞ 1 ${}_{\infty }{}^{1}\left[{{\text{BiI}}_{2/1}{\text{I}}_{4/2}\right]}^{-}$ and [ Bi 6 I 18 / 1 I 4 / 2 ∞ 1 ] − ${{}_{\infty }{}^{1}\left[{\text{Bi}}_{6}{\text{I}}_{18/1}{\text{I}}_{4/2}\right]}^{-}$ anions occur in 1 and 2, whereas various polyiodide anions (e.g. [I3]−, [I5]−, [I7]−, [I9]−) with partly complex interaction are observed in 4, 5, and 6. The title compounds were characterized by single-crystal X-ray diffraction analysis and infrared spectroscopy. In the case of 1 and 2, the optical band gap was determined to be Eg = 1.91 and 1.62 eV, respectively. Especially, the ionic-liquid-based synthesis affords the different metastable compounds with variable composition and structure in a narrow temperature range. [ABSTRACT FROM AUTHOR]

The iodido bismuthates [Bi(18-crown-6)I2][BiI4] (1) and [Bi(18-crown-6)I2][Bi3I10] (2), the neutral complex [Bi(C6H14O4)I3](18-crown-6) (3) as well as the polyiodides [Bi(18-crown-6)I2][I5](18-crown-6) (4), [Bi(18-crown-6)I2]2[I14] (5) and [Bi(18-crown-6)I2]2[I19] (6) were prepared by reaction of BiI3, 18-crown-6, and I2 at T = 60–120 °C. The compounds 1–5 were prepared in [n-Bu3MeN][N(Tf)2] as an ionic liquid ([n-Bu3MeN]: tributylmethylammonium, [N(Tf)2]: bis(trifluoromethylsulfonyl)imide), whereas 6 was obtained only by direct reaction of the starting materials. The title compounds exhibit two different constitutions of the [Bi(18-crown-6)I2]+ cation as well as a non-charged, molecular [Bi(C6H14O4)I3] unit with a triethylene glycol ligand generated in situ by cleavage of the crown ether. Infinite chain-like [ BiI 2 / 1 I 4 / 2 ] − ∞ 1 ${}_{\infty }{}^{1}\left[{{\text{BiI}}_{2/1}{\text{I}}_{4/2}\right]}^{-}$ and [ Bi 6 I 18 / 1 I 4 / 2 ∞ 1 ] − ${{}_{\infty }{}^{1}\left[{\text{Bi}}_{6}{\text{I}}_{18/1}{\text{I}}_{4/2}\right]}^{-}$ anions occur in 1 and 2, whereas various polyiodide anions (e.g. [I3]−, [I5]−, [I7]−, [I9]−) with partly complex interaction are observed in 4, 5, and 6. The title compounds were characterized by single-crystal X-ray diffraction analysis and infrared spectroscopy. In the case of 1 and 2, the optical band gap was determined to be Eg = 1.91 and 1.62 eV, respectively. Especially, the ionic-liquid-based synthesis affords the different metastable compounds with variable composition and structure in a narrow temperature range. [ABSTRACT FROM AUTHOR]

To date, the world has accumulated a large amount of long-lived radioactive materials that need to be disposed of or reprocessed. Such materials include nuclear legacy objects containing 226Ra, which is an important material for obtaining a wide range of isotopes for nuclear medicine via irradiation in reactors, cyclotrons, and electron accelerators. For the selective recovery of 226Ra from waste materials, crown-ether (CE) 18-crown-6 (18C6) or its derivatives can be used, which, however, have not been widely studied for these purposes. In our work, the key property of 18C6 and its derivatives, the phase distribution, was studied using tritium labeling. The possibility of introducing a tritium label into CEs molecules using thermal activation of tritium has been demonstrated; a high specific activity of the obtained compounds was achieved (from 18 to 108 TBq/mol). Methods for chromatographic purification of the studied CEs were developed. The distribution of 18C6 and its derivatives between various organic solvents and water was studied in detail for the first time. Subsequently, the obtained data will allow us to choose conditions for the selective recovery of 226Ra from aged sources.

Complexes [(Pr(DPM)3)2], [Pr(DPM)3(18-crown-6)], [(Pr(DPM)3)2(18-crown-6)], [Pr(DPM)(PTA)(18-crown-6)]+ and the temperature sensitivity of paramagnetic lanthanidine-induced shifts of these complexes in CDCl3 solution are characterized by 1H NMR. The NMR methods are used to estimate the possibility of forming inclusive complexes in CDCl3 solution upon the interaction of lanthanide tris-β-diketonates with 18-crown-6 in the case of a more branched ligand than PTA (e.g., DPM). Upon the interaction of [(Pr(DPM)3)2] and 18-crown-6, the [Pr(DPM)3(18-crown-6)] forms prevail in solution. The obtained results indicate that the studied coordination compounds can be considered as 1H NMR paramagnetic lanthanide probes for local temperature control in organic solutions using the analysis of paramagnetic lanthanidine-induced shifts. [ABSTRACT FROM AUTHOR]

A Cloud point extraction (CPE) procedure was presented for preconcentration of lead(II) ions, after complexation by 18-crown-6 (18C6) and extraction with Triton X-100 at proposed experimental conditions. After separation of surfactant - rich phase, content of Pb(II) ions in remaining solution was measured by Flame Atomic Absorption Spectrometry (FAAS). The experimental conditions such as pH, temperature, concentration of Triton X-100, concentration of 18C6, incubation time, type and concentration of added electrolyte, were evaluated. Results showed that among investigated electrolytes (NaCl, Na2SO4 and Na2CO3) the amount of 0.9 mol/L Na2CO3 lowers cloud point temperature of Triton X-100 to 22°C (room temperature during the experiment), thus simplifying the extraction procedure. After an incubation time of 5 minutes and using the concentration of 1.2•10-3 mol/L Triton X-100 and 1.5•10-4 mol/L 18C6 (1:1 stoichiometric ratio for 18C6:Pb), 60% of lead (II) ions were efficiently removed from investigated solution.

Application of 1-butyl-3-metyhlimidazaolium hexafluorophosphate ([C4mim][PF6]), in the extraction of rubidium and cesium from brine solutions using 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) as extractant was investigated. Parameters that affect the extraction including pH of aqueous phase, equilibration time, dosage of the ionic liquid, phase ratio, concentration of 18C6 were studied. Under the optimal conditions, the single extraction efficiency of rubidium ions and cesium ions were up 84.11% and 94.99%, respectively. The stripping of alkali metal ions from the loaded organic phase with different stripping agents and concentrations were also investigated. The initial value of the K/Cs and K/Rb ratios were 93.0 and 104.3, respectively, which have dropped 91.21% and 88.01%, respectively, after the extraction and stripping experiments. It was taken a big step in the separation and enrichment of cesium (rubidium) ion and potassium ion. The extraction mechanism was revealed most likely to be a cation exchange mode in this system.

The analysis of the ratios of entropy and enthalpy characteristics and their contributions to the change in the Gibbs energy of intermolecular interactions of crown ethers and cyclodextrins with amino acids is carried out. Two different types of macrocycles were chosen for examination: crown ethers with a hydrophilic interior and cyclodextrins with a hydrophobic inner cavity and a hydrophilic exterior. The thermodynamics of complex formation of crown ethers and cyclodextrins with amino acids in water and aqueous-organic solvents of variable composition was examined. The contributions of the entropy solvation of complexes of 18-crown-6 with glycine, alanine, phenylalanine to the change in the entropy of complexation in water-ethanol and water-dimethyl sulfoxide solvents was calculated and analyzed. It was found that the ratios of the entropy and enthalpy solvation of the reagents for these systems have similar trends when moving from water to aqueous-organic mixtures. The relationship between the thermodynamic characteristics and structural features of the complexation processes between cyclodextrins and amino acids has been established. The thermodynamic enthalpy–entropy compensation effect was revealed, and its features for complexation of cyclodextrins and 18-crown-6 were considered. It was concluded that, based on the thermodynamic parameters of molecular complexation, one could judge the mode of the formation of complexes, the main driving forces of the interactions, and the degree of desolvation.

Abstract. With the attempt to synthesize Nb‐enclosed germanium Zintl cluster ion in ethylenediamine (en) / toluene solution, the reaction of K4Ge9/Na4Ge9 with Nb(mes)2 (mes = mesitylene) gives unexpected 18‐crown‐6 cleavage product of [K14Na2(NbO2)2(C8H16O5)8](Ge5) (en)·solv in the form of very air‐sensitive, light‐brown, plate‐like crystals. This unique compound crystallizes in monoclinic Pn (No. 7) space group, the cleavage of crown linked the 14 potassium, 2 sodium, and 2 niobium atoms into the bulky 2+ charged cation, which balances the [Ge5]2– anion. This compound represents the rare example of heteronuclear metal alkoxide / Zintl ion hybrid. [ABSTRACT FROM AUTHOR]

The effect of 18-crown-6 ether (18C6) on the anionic polymerization of ε-caprolactone (ε -CL) using potassium tert-butoxide (t-BuOK) as the initiator was studied. The experimental results showed that 18C6 in combination with t-BuOK exhibited high selectivity for ring opening relative to trans-esterification and improved control toward the ROP of ε-CL, producing poly(ε- caprolactone) (PCL) with much higher molecular weight and relatively narrow distribution compared to those using t-BuOK alone as the initiator.The influences of reaction conditions, such as monomer concentration, monomer/initiator molar ratio, and [18C6]/[t-BuOK] molar ratio, as well as reaction temperature and time on the polymerization have been examined in detail. The resulting hopolymers were characterized by various analytical techniques, such as GPC, FTIR, 1H NMR, DSC, TGA, and MALDI-ToF MS, to monitor the structures and property changes of PCLs. [ABSTRACT FROM AUTHOR]

Triple cation perovskites (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) have received lots of attention owing to the excellent stability and photovoltaic performance. However, the development toward efficient solar cells has been significantly impeded by its intrinsic precursor instability, as well as defective crystal surface. Herein, a strategy for introducing the additive of 1,4,7,10,13,16‐hexaoxacyclooctadecane (18C6) in the precursor solution, rendering an excellent stability of more than one month, and the defect passivation effect on the crystal surface are demonstrated. In those perovskite solar cells, a power conversion efficiency of 20.73% has been achieved with a substantially improved open‐circuit voltage and fill factor. As evidenced by the density functional theory calculations, the fundamental reason relating to the enhanced performance is found to be the interaction effect between the 18C6 and cations, and in particular the formation of the 18C6/Pb complex. This finding represents an alternative strategy for achieving a stable precursor solution and efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

The crystal and molecular strutures of two solvated forms of [K(18c6)]OAc (18c6 = 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane and OAc = acetate) were determined by single-crystal X-ray diffraction, namely (acetato-κ2O,O′)(1,4,7,10,13,16-hexaoxacyclooctadecane-κ6O)potassium dihydrate, [K(CH3COO)(C12H24O6)]·2H2O (1) and (acetato-κ2O,O′)aqua(1,4,7,10,13,16-hexaoxacyclooctadecane-κ6O)potassium acetic acid monosolvate [K(CH3COO)(C12H24O6)(H2O)]·CH3COOH (2). In both compounds, the acetate anion is bonded to the potassium ion in a chelating fashion and the metal atom is consequently slightly displaced from the O6 plane of the crown ether. In the crystals, O—H...O hydrogen bonds lead to a polymeric ladder structure in the dihydrate 1, while the acetic acid hydrate 2 features inversion dimers.

Purpose. Study of reactions of obtaining anion-radical of oxygen: one-electron oxygen reduction and complex formation in the system of crown-ether - potassium superoxide - solvent. Investigation of the possibility of regulating the activity of two different supramolecular structures containing oxygen anion radical to create new antioxidant systems. Methodology. The oxygen anion radical in solution was obtained by the method of electrochemical oxygen reduction, as well as by complexation in the system of crown ether – potassium superoxide – solvent. The amount of oxygen radical anion obtained was monitored spectrophotometrically using a high-quality reaction with tetrazolium blue and the potentiometric method using an exchange reaction with butyl bromide. Results. The activity of two different supramolecular structures containing oxygen anion radical is compared. It is shown that in the transition from the chemical method of generation of oxygen anion radical to electrochemical, the activity of the anion radical in the reaction with alkyl halide increases slightly. Spectrophotometrically and potentiometrically determined the kinetic parameters of the electrochemical oxygen reduction in the aprotic medium, as well as the process of complexation in the system of crown ether – potassium superoxide – solvent. Scientific novelty. The activity of two different supramolecular structures containing anion-radical of oxygen with the (Crown-K)+ and (tetraethylammonium)+ ions in reaction with propyl bromide in acetonitrile was compared. Practical significance. The conducted studies allow us to choose the optimal mode and structure of the complex - the sources of oxygen anion radical, depending on the task and goals of the experiment. The study of the complexation reaction in the system of crown ethers - potassium superoxide - solvent, along with the electrochemical method of obtaining active oxygen, is necessary not only in terms of obtaining the most stable form of oxygen anion radical, but also the creation of model systems that allow to analyze the mechanisms and patterns of the processes in biological systems. The obtained results indicate the prospect of using the investigated supramolecular complexes containing oxygen anion radical to create new antioxidant systems that can be used as new classes of antioxidants for engineering, medicine and pharmacy purposes. [ABSTRACT FROM AUTHOR]

Abstract The effect of solvation on the stability of the complexes of silver(I) ion with 18-crown-6 ([Ag18C6]+) upon the change of the solvent composition (EtOH → (EtOH-DMSO)) was investigated. Gibbs energy of transfer of both silver(I) ion and the macrocyclic ligand employed (18-crown-6) from pure ethanol to ethanol-dimethyl sulfoxide mixtures (DMSO) were obtained by potentiometry and by determining the distribution between two immiscible phases at 25 °C, respectively. An increase of DMSO content in the binary mixture results in an increase of the differences in the solvation of the central ion and the complex. This shifts the equilibrium of complex formation towards the formation of products. We show that the relationship between changes in the stability of the coordination compound and changes in the solvate state of the reactants is sufficiently regular to allow for the prediction of changes in the stability of [Ag18C6]+ when a non-aqueous solvent is increasingly replaced by another non-aqueous solvent. Highlights • Influence of EtOH-DMSO solvents on the reaction of [Ag18C6]+ formation was studied. • Shift in complexation equilibrium is defined by changes in solvation state of Ag+. • Values of lg K [Ag18C6]+ were estimated on basis of Gibbs transfer energies of Ag+. [ABSTRACT FROM AUTHOR]

In this work, we describe a 2-min direct injection electrospray tandem quadrupolar mass spectrometric method for ethyl carbamate (EC) detection in Brazilian sugar cane spirit (SCS). Analyses were carried out with 18-crown-6/trifluoracetic acid (30 ppm/0.1%) additives to sequester metal cations by eliminating unwanted [EC + Na]+ and [EC + K]+ ions, favoring analyte detection as sole [EC + H]+ ions. Standard addition of EC was carried out with 18-crown-6/trifluoracetic acid (30 ppm/0.1%), resulting in spiked SCS samples (0, 75, 150, 300, 450, 600, 750, and 900 μg L−1). A carrier solution of methanol:18-crown-6:trifluoroacetic acid (99.9:30 ppm:0.10, v/v/v) was pumped to the mass spectrometer using positive ion mode and multiple reaction monitoring of 90 > 62 for EC. The limits of detection and quantification were 7.5 and 75.0 μg L−1, respectively, and the dynamic range used was 75-900 μg L−1. The validation results and application of the method to the analysis of real samples and certified SCS demonstrate its applicability to quality control and regulatory analysis. [ABSTRACT FROM AUTHOR]

A novel colorimetric sensor array based on boron-dipyrromethene (BODIPY) dyes was developed to monitor the volatile organic compounds (VOCs) of rice at different storage times. The VOCs of rice at different storage times were analyzed through GC–MS combined with multivariate analysis, and the compound 18-crown-6 was found significantly changed during rice aging process. Aimed at 18-crown-6 with particular macrocyclic structure, a series of BODIPYs were targeted synthesized for the selection of sensitive chemically responsive dyes. Four dyes were chosen to construct colorimetric sensor array based on sensitivity to VOCs of aged rice samples. Data acquired from the interactions of dyes and rice VOCs were subjected to the principal components analysis (PCA) and linear discriminant analysis (LDA). The optimal performance obtained by the LDA model was 98.75% in prediction set. Application of BODIPYs in this work has improved the sensitivity and expanded the choices of colorimetric dyes for the specific detection. [ABSTRACT FROM AUTHOR]

Complexes of 18-crown-6 with BaCl2, Ba(NO3)2 and Ba(NTf2)2 salts were synthesized and irradiated with X-rays to simulate the radiation degradation of a macrocyclic component of extractants based on crown ether solutions in commonly used solvents. Structures and post-irradiation transformations of radical products stabilized in these complexes at 77 K were studied using EPR spectroscopy, and the mechanism of their formation and decay was proposed. Differences in ionization potentials of the macrocycle and the anions and reactivity of the intermediates generated from the anions are of importance for radiation stability of the studied compounds. The nitrate-anions was demonstrated to protect 18C6 from destruction whereas Cl− and bis(trifluoromethylsulfonyl)imide-anions can impair the radiation stability of the macrocycle. The results of the present study offer an opportunity to predict the radiation stability of the crown ether extractants and their applicability for liquid radioactive waste reprocessing. [ABSTRACT FROM AUTHOR]

The complexation reaction between hydroxyl ammonium (HONH3+ ) cation with 18-crown-6 (18C6) ligand was studied in dimethylsulfoxide – water (DMSO-H2O), methanol – water (MeOH-H2O) and dimethylformamid – methanol (DMF-MeOH), binary solutions at different temperatures using conductometric method. The obtained results show that the stoichiometry of the complex formed between HONH3+ cation with (18C6 ) in all of the binary mixed solvents is 1:1[ML], as well as, these results show that the nature and the composition of the solvent systems are important factors that are effective on the stability of the complex formed between the macrocyclic ligand and metal cation in solutions. A non-linear behavior was observed for changes of stability constants of the complex versus the composition of the binary mixed solvents. The values of thermodynamic parameters show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents and the complex is entropy stabilized, but enthalpy destabilized in most compositions of binary solutions.

The reaction of bis(anthracene)cobaltate(−I) with excess cycloheptatriene, C7H8, resulted in a new 18-electron cobaltate containing two different seven-membered ring ligands, based on single-crystal X-ray diffraction. The asymmetric unit of this structure contains two independent cation–anion pairs of the title complex, [K(18-crown-6)][Co(η3-C7H7)(η5-C7H9)], where 18-crown-6 stands for 1,4,7,10,13,16-hexaoxacyclooctadecane (C12H24O6), in general positions and well separated. Each (18-crown-6)potassium cation is in contact with the η3-coordinating ligand of one cobaltate complex. Each η3-coordinating ligand behaves as an allylic anion whose exo-diene moiety is bent away from the allylic plane, and thus is not involved directly in the bonding. The metal-coordinating portions of the anionic η5 ligands are planar and one of these ligands is modeled as disordered over two positions, with occupancy ratio 0.699 (5):0.301 (5), such that one orientation is rotated by one carbon atom with respect to the other. The diffraction intensities were integrated according to non-merohedral twin law [-1 0 0/0 -1 0/0.064 0 1], a 180° rotation about reciprocal lattice axis [001], and the masses of the twin domains refined to equal amounts. As both ligands are formally coordinated as anions, the cobalt atom is best considered to be CoI. This compound is of interest as the first to possess cycloheptatrienyl and cycloheptadienyl ligands in an anionic metal complex.

A new complex of the title system ([2(H 3 O + )·18-crown-6]·2[BF 4 − ]), which was induced by external magnetic field, has been prepared and characterized. When compared with other two members of the same system, the proton transfer induced by magnetic field from HBF 4 to H 2 O has leads to the co-plane of six oxygen atoms in the crown and stronger H F and O F intermolecular interactions, which can be attributed to the closer contacts between 18-crown-6, oxonium ion H 3 O + and counterion BF 4 − . In addition, a compression effect of crystals stacking has been observed. These results are of importance for the evaluation the effect of magnetic field on the host–guest systems. [ABSTRACT FROM AUTHOR]

An improved ion chromatographic method including two elution procedures was proposed for the quantitative determination of atmospheric alkylamines in field atmospheric samples involving high levels of inorganic cations by using 18-crown-6 as mobile phase additive. When 18-crown-6 was added to the mobile phase, the retention times increased significantly for Na + , NH 4 + , K + and primary alkylamines but decreased for secondary and tertiary alkylamines due to the complexation with certain cations and interaction with both stationary and mobile phases of 18-crown-6. As a result, the separation of the cations was greatly promoted, which reduced the interference of peak distortion of overloaded inorganic cations on the quantitation of adjacent alkylamines. By using the presented method, five inorganic cations (Na + , NH 4 + , K + , Mg 2+ , Ca 2+ ) and six alkylamines (dimethylamine (DMAH + ), trimethylamine + diethylamine (TMAH +  + DEAH + ), propylamine (MPAH + ), triethylamine (TEAH + ), ethanolamine (MEOAH + ) and triethanolamine (TEOAH + )) were effectively separated and determined, and the relative standard derivations (RSDs) of objective cations were all less than 1% for retention time and 3.1% for peak area (n = 9), respectively. The linearity was excellent for each cation (R 2  > 0.993) except for NH 4 + and TEOAH + showing a non-linear response (R 2  > 0.998 for theoretical non-linear fitting), and the detection limit of these cations were 0.03–1.19 ng. The proposed method was successfully used in the determination of both alkylamines and inorganic cations in ambient particulate matters and gaseous alkylamines in ceiling duct exhaust. The annual average concentrations of DMAH + , TMAH +  + DEAH + and TEAH + were 15.56, 4.35 and 16.00 ng m −3 in PM 2.5 over Shanghai in 2013. The concentrations of gaseous DMA and TMA + DEA in ceiling duct exhaust reached a maximum of 940.0 and 112.7 μg m −3 , and were positively correlated with the human activity intensity, suggesting that human excreta emissions was a potential important source of atmospheric alkylamines in urban area of Shanghai. [ABSTRACT FROM AUTHOR]

This paper reports the result of process development studies on separation of Sr(II) from Eu(III) in 4 M nitric acid using supported liquid membrane (SLM). The process utilizes addition of 18-crown-6 for masking of Sr(II), followed by their transport across SLM with TEHDGA as carrier molecule. The optimized process shows complete transport of Eu(III) in about 60 min, leaving pure Sr(II) in the feed compartment. The Sr(II) and Eu(III), both in pure form are valuable in medical and industrial radiation technology applications. [ABSTRACT FROM AUTHOR]

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