New calсium β-diketonate complexes: The monomeric complexes [Ca(PhCOCHCOCF3)2(15-crown-5)], [Ca(AdCOCHCOCF3)2(15-crown-5)] and the binuclear hydrated complex [{Ca(adtfa)(18-crown-6)(H2O)}{Ca(adtfa)3(H2O)}(EtOH)]. Synthesis, characterization and crystal structure

The preparation of the Ca-β-diketonate complexes with crown-ethers, [Ca(btfa)₂(15-crown-5)] (1), [Ca(adtfa)₂(15-crown-5)] (2), [Ca(adtfa)₂(15-crown-5)](C₆H₅CH₃)_0.5 (3) and [{Ca(adtfa)(18-crown-6)(H₂O)}{Ca(adtfa)₃(H₂O)}(EtOH)] (4) (btfa = 1,1,1-trifluoro-4-phenyl-butanedionato-2,4; adtfa = 1,1,1-trifluoro-4-(1-adamantyl)butanedionato-2,4; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), is described. Complex 1 has been prepared from the reaction of metallic Ca with 2 eq. of Hbtfa and 1 eq. of 15-crown-5 in toluene; complex 2 has been prepared from the reaction of metallic Ca with 2 eq. of Hadtfa and 1 eq. of 15-crown-5 in ethanol. The solvated complex 3 was obtained by cooling of a toluene-hexane solution of 2. The hydrated complex 4 was prepared from the reaction of metallic Ca with 2 eq. of Hadtfa and 1 eq. of 18-crown-6, followed by addition of excess H₂O to the resulting reaction mixture. The all complexes were characterized by elemental analyses, IR-spectroscopy, NMR-spectroscopy, single-crystal X-ray diffraction methods, DSC and TGA. A single-crystal X-ray study of 1 and 3 has show that complexes 1 and 3 are monomeric and contain the calcium atom bonded with two β-diketonate ligands and one molecule of crown-ether. Complex 4, as shown by X-ray analyses, is an ion-paired solvated adduct, containing the cation {Ca(adtfa)(18-crown-6)(H₂O)}⁺ and the anion {Ca(adtfa)₃(H₂O)}⁻. The monomeric complexes 1-3 are volatile and thermally stable in the temperature range 100-260 °C. Complex 4 undergoes decomposition above 110 °C with consecutive loss of ethanol, H₂O, 18-crown-6 and some evaporization of 4.     

Yttrium thiocyanate-based supramolecular architectures: Synthesis, crystal structures, and thermal properties

The reaction of [Y(H₂O)₅(NCS)₃]·H₂O (1) with crown ether (18-crown-6) and KNCS in methanol afforded the complexes [Y(H₂O)₄(NCS)₃]·1.5(18-crown-6) (2) and [K(18-crown-6)(H₂O)_1.25]_2n{[K(18-crown-6)]₂[Y(NCS)₆]}_n·n(NCS) (3). In mononuclear complex 1, yttrium has a coordination number 8 and forms the coordination unit YO₅N₃. Complexes 1 are linked by hydrogen bonds to form a framework. The crystal structure of 2 contains the centrosymmetric ensembles [Y(H₂O)₄(NCS)₃]₂(18-crown-6)₃ formed via hydrogen bonds. In the crystal structure of 3, the [Y(NCS)₆]³⁻ anions and the [K(18-crown-6)]⁺ cations form one-dimensional polymeric chains (-Y-NCS-K-)_n. The thermal behavior of compounds 1 and 2 was investigated. It was shown that the supramolecular assembly has an effect on the temperature range for the removal of coordinated water molecules from the thiocyanate complex. The oxidative decomposition of the acido ligands in 1 and 2 occurs in a similar way to give Y₂O₂SO₄ as the final product (700 °С).     

Barium bis(5,5-dimethyl-1,1,1-trifluorohexane-2,4-dionate)(crown-ether) complexes: Synthesis,characterization and crystal structure

The preparation of the barium β-diketonate complexes with crown-ethers [Ba(pta)₂(18-crown-6)] (1), [Ba(pta)₂(18-crown-6)] (THF) (2), [Ba(pta)₂(18-dibenzocrown-6)](C₆H₅CH₃) (3), [Ba(pta)₂(18-dibenzocrown-6)] (4) (pta = 1,1,1-trifluoro-5,5-dimethylhexanedionato-2,4; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; 18-dibenzocrown-6 = 6,7,9,10,17,18,20,21-octahydrodibenzo[b,k][1,4,7,10,13,16]-hexaoxacyclooctadecane) is described. The complexes 1 and 2 have been synthesized from reaction of metallic barium with 2 molar equiv. of Hpta and 1 molar equiv. of 18-crown-6 in toluene; the complexes 3 and 4 from reaction of Ba(OH)₂·8H₂O with 1 molar equiv. 18-dibenzocrown-6 and 2 molar equiv. Hpta. The complexes were characterized by elemental analyses, IR-spectroscopy, ¹H NMR spectroscopy. The crystal structures of 2 and 3 were determined by means of single-crystal X-ray diffraction methods. A single-crystal X-ray study of 2 and 3 has shown it be monomeric. The coordination number of Barium cation in 2 and 3 is nine owing to nine oxygen atoms from two pta ligands and crown-ether molecule.     

An efficient synthesis of 4,4′,5,5′-tetraiododibenzo-24-crown-8 and its highly conjugated derivatives

4,4′,5,5′-Tetraiododibenzo-24-crown-8 (9), a practical building block, was prepared under efficient and mild reaction conditions starting from the simple starting material, catechol (1). Highly conjugated 4,4′,5,5′-tetraethynyldibenzo-24-crown-8 (10a,b) were prepared via a Sonogashira coupling reaction from tetraiodocrown ether 9. These highly conjugated crown ethers form complexes in CD₂Cl₂ with dibenzylammonium hexafluorophosphate in a 1:1 ratio. Emission spectrum of pseudorotaxane 11 shows a dramatic shift from the non-complexed precursor.     

Synthesis and evaluation of bipendant-armed (oligo)thiophene crown ether derivatives as new chemical sensors

Three new (oligo)thiophene bipendant-armed ligands 2a-c, derived from 2-(aminomethyl)-15-crown-5, have been synthesized and characterized. Compounds 2a-c were prepared by reductive amination of the corresponding macrocycle with formyl thiophene derivatives 1a-c in the presence of NaBH(OAc)₃ in fair to good yields. The photophysical properties of ligands 2a-c were studied and they were also evaluated as chemosensors in the presence of Na(I), Ag(I), Pd(II) and Hg(II) cations in acetonitrile solution.     

Periphery-modified crown ethers. Synthesis of bis-5,8-dimethoxy-1,4-methanonaphthalene-fused crown ethers

The easily accessible and multi-functionalized 5,8-dimethoxy-6,7-dihydroxy methyl-1,4-dihydro-1,4-methanonaphthalene (1) has been utilized as the basic building material to synthesize the symmetric bis-methanonaphthalene-fused crown ethers 14a-d (BMN-16-crown-4, BMN-22-crown-6, BMN-28-crown-8, and BMN-34-crown-10), that are constructed based on the connection between the α,β-bis-benzylic carbon atoms of diol 1 and oligoethylene glycols (9a-d) via two synthetic routes keyed upon the method of Williamson ether synthesis.     

The synthesis, spectroscopic properties and X-ray structure of Zn(II) complexes with amino derivatives of chromone

Three new Zn(II) complexes containing the ligands 5-amino-8-methyl-4H-chromen-4-one (1), 6- or 7-amino-2-phenyl-4H-chromen-4-one (2, 3) were prepared. The new synthesised compounds were characterised by IR, ¹H NMR and MS spectroscopy. The crystal structure of complex 4 was determined with the use X-ray diffraction. The Zn(II) centre of 4 is linked by two chlorido and two N-bound aminochromone ligands, 1, in a strongly distorted tetrahedral configuration with the dissymetric point group C₂. The protonation constants of the ligands 1, 2 and 3 corresponded to 3.68, 3.88 and 6.83, respectively. The stability constants of the Zn(II) complexes were calculated from the potentiometric titration data. The complexes were found to have the formulae ML and ML₂ for ligands 1 and 2, and ML for ligand 3. Fluorescence spectroscopic properties were also studied; the strongest fluorescence in solution was exhibited by complex 6.     

Selection of synthetic receptors capable of sensing the difference in binding of d-Ala-d-Ala or d-Ala-d-Lac ligands by screening of a combinatorial CTV-based library

Screening of a combinatorial CTV-based artificial, synthetic receptor library 1 {1-13, 1-13, 1-13} for binding of a variety d-Ala-d-Ala and d-Ala-d-Lac containing ligands (6-11) was carried out in phosphate buffer (0.1 N, pH=7.0). After screening and Edman sequencing, synthetic receptors were found containing amino acid sequences, which are either characteristic for binding dye labeled d-Ala-d-Ala or d-Ala-d-Lac containing ligands. For example, receptors capable of binding d-Ala-d-Ala containing ligands 6, 7, 9 and 11 contained—almost in all cases—at least one basic amino acid residue—predominantly Lys—in their arms. This was really a striking difference with the arms of the receptors capable of binding d-Ala-d-Lac containing ligands 8 and 10, which usually contained a significant number of polar amino acids (Gln and Ser), especially in ligand 8, but hardly any basic amino acids. Use of different (fluorescent) dye labels showed that the label has a profound, albeit not decisive, influence on the binding by the receptor. A hit from the screening of the CTV-library with FITC-peptidoglycan (6) was selected for resynthesis and validation.     

Di(1H,1H,2H,2H-perfluorooctyl)-dibenzo-18-crown-6: A “light fluorous” recyclable phase transfer catalyst

A series of dibenzo-18-crown-6 lariat ethers containing two C₇H₁₅ (11), (CH₂)₂C₆F₁₃ (14), (CH₂)₂C₈F₁₇ (15), NHC₇H₁₅ (18) and NHCH₂C₆F₁₃ (19) sidearms were prepared and the single crystal X-ray structure of cis-4,4′-di(1H,1H,2H,2H-perfluorodecyl)-dibenzo-18-crown-6 (15a) is reported. The “light fluorous” dibenzo-18-crown-6 ether (14) has emerged as a stable and robust PTC catalyst, which can be recycled efficiently by fluorous solid-phase extraction, and gives better PTC catalytic activity compared to the parent, non-fluorinated PTC catalyst, dibenzo-18-crown-6, and the alkylated derivative (11) in aliphatic and aromatic nucleophilic substitutions.     

Nickel (II) complexes bearing 2-ethylcarboxylate-6-iminopyridyl ligands: synthesis, structures and their catalytic behavior for ethylene oligomerization and polymerization

A series of nickel (II) complexes (L)NiCl₂ (7-9) and (L)NiBr₂ (10-12) were prepared by the reactions of the corresponding 2-carboxylate-6-iminopyridine ligands 1-6 with NiCl₂ · 6H₂O or (DME)NiBr₂ (DME = 1,2-dimethoxyethane), respectively. All the complexes were characterized by IR spectroscopy and elemental analysis. Solid-state structures of 7, 8, 10, 11 and 12 were determined by X-ray diffraction. In the cases of 7, 8 and 10, the ligands chelate with the nickel centers in tridentate fashion in which the carbonyl oxygen atoms coordinate with the metal centers, while the carbonyl oxygen atoms are free from coordinating with the nickel centers in 11 and 12. Upon activation with methylaluminoxane (MAO), these complexes are active for ethylene oligomerization (up to 7.97 × 10⁵ g mol⁻¹ (Ni) h⁻¹ for 11 with 2 equivalents of PPh₃ as auxiliary ligand) and/or polymerization (1.37 × 10⁴ g mol⁻¹ (Ni) h⁻¹ for 9). The ethylene oligomerization activities of 7-12 were significantly improved in the presence of PPh₃ as auxiliary ligands. The effects of the coordination environment and reaction conditions on the ethylene catalytic behaviors have been discussed.     

Application of chiral tetrahydropentalene ligands in rhodium-catalyzed 1,4-addition of (E)-2-phenylethenyl- and (Z)-propenylboronic acids to enones

Chiral tetrahydropentalenes (3aR,6aR)-1 have been prepared and used as ligands in the Rh-catalyzed 1,4-addition of 1-alkenylboronic acids to cyclic enones 5. It has been discovered that the stereochemistry of the reaction was controlled by the steric properties of the aryl groups in 1 rather than their electronic nature. In the vinylation with (E)-2-phenylethenylboronic acid 5, ligands (3aR,6aR)-1 provided enantioselectivity up to 87% ee and gave high yields of ethenylketones 6 in the presence of 1 (6.6 mol %). The configuration of all ketone products obtained with (3aR,6aR)-1 is (S). Rh-catalyzed reaction of cyclopentenone 4a and (Z)-propenylboronic acid 7 in the presence of ligands (3aR,6aR)-1 yielded at 50 °C an inseparable mixture of (Z)- and (E)-ketones 8 with (Z)-8 as the major product and both in only moderate enantiomeric excess.     

Complexing properties of two benzocrown-ether moieties arranged at a cyclobutane ring system

Biscrown ethers 2a-c and 3a-c arranged at a cyclobutane ring were prepared by intermolecular [2+2] photocycloaddition of vinylated benzocrown ethers. The complexing behavior of 2a-c toward alkali metal cations was evaluated by ESI-MS analysis, liquid-liquid extraction, and the comparison of complexing stability constant. An intramolecular sandwich-type 1:1 (host/guest) complexation was observed by ESI-MS analysis in the competitive system where 2a-Na⁺, 2b-K⁺, and 2c-Cs⁺ were formed selectively. In the liquid-liquid extraction, however, 2a hardly extracted any cation, while both 2b and 2c efficiently extracted larger cations such as K⁺, Rb⁺, and Cs⁺. It was found that the complexing stability constant of 2a-Na⁺ is lower than that of benzo-15-crown-5-Na⁺ though extraordinarily high values were obtained for 2b-K⁺ and 2c-Cs⁺ complexes compared with those of 18-crown-6-K⁺ and dibenzo-24-crown-8-Cs⁺ complexes, respectively. Hence, the excellent complexing ability was achieved by using the cyclobutane ring, which strongly preorganized two benzocrown-ether moieties for the larger alkali metal cations.     

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.     

Syntheses, structures and photoluminescence of a series of coordination frameworks based on dicarboxylate anion and bis(imidazole) ligand

In this article, ten new coordination frameworks, namely, [Ni(H₂O)₆]·(L3) (1), [Zn(L3)(H₂O)₃] (2), [Cd(L3)(H₂O)₃]·5.25H₂O (3), [Ag(L1)(H₂O)]·0.5(L3) (4), [Ni(L3)(L1)] (5), [Zn(L3)(L1)_0.5]·H₂O (6), [Cd(L3)(L1)_0.5(H₂O)] (7), [CoCl(L3)_0.5(L1)_0.5] (8), [ZnCl(L3)_0.5(L2)_0.5] (9), and [CoCl(L3)_0.5(L2)_0.5] (10), where L1 = 1,1′-(1,4)-butanediyl)bis(imidazole), L2 = 1,1′-(1,4-butanediyl)bis(2-ethylbenzimidazole) and H₂L3 = 3,3′-(p-xylylenediamino)bis(benzoic acid), have been synthesized by varying the metal centers and nitrogen-containing secondary ligands. These structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses and IR spectra. In 1, the L3 anion is not coordinated to the Ni(II) center as a free ligand. The Ni(II) ion is coordinated by water molecules to form the cationic [Ni(H₂O)₆]²⁺ complex. The hydrogen bonds between L3 anions and [Ni(H₂O)₆]²⁺ cations result in a three-dimensional (3D) supramolecular structure of 1. In compounds 2 and 3, the metal centers are linked by the organic L3 anions to generate 1D infinite chain structures, respectively. The hydrogen bonds between carboxylate oxygen atoms and water molecules lead the structures of 2 and 3 to form 3D supramolecular structures. In 4, the L3 anion is not coordinated to the Ag(I) center, while the L1 ligands bridge adjacent Ag(I) centers to give 1D Ag-L1 chains. The hydrogen bonds among neighboring L3 anions form infinite 2D honeycomb-like layers, in the middle of which there exist large windows. Then, 1D Ag-L1 chains thread in the large windows of the 2D layer network, giving a 3D polythreaded structure. Considering the hydrogen bonds between the water molecules and L3 anions, the structure is further linked into a 3D supramolecular structure. Compounds 5 and 7 were synthesized through their parent compounds 1 and 3, respectively, while 6 and 9 were obtained by their parent compound 2. In 5, the L3 anions and L1 ligands connect the Ni(II) atoms to give a 3D 3-fold interpenetrating dimondoid topology. Compound 6 exhibits a 3D three-fold interpenetrating α-Po network structure formed by L1 ligands connecting Zn-L3 sheets, while compound 7 shows a 2D (4,4) network topology with the L1 ligands connecting the Cd-L3 double chains. In compound 8, the L1 ligands linked Co-L3 chains into a 2D layer structure. Two mutual 2D layers interpenetrated in an inclined mode to generate a unique 3D architecture of 8. Compounds 9 and 10 display the same 2D layer structures with (4,4) network topologies. The effects of the N-containing ligands and the metal ions on the structures of the complexes 1-10 were discussed. In addition, the luminescent properties of compounds 2-4, 6, 7 and 9 were also investigated.     

Zinc(II) complexes with novel 1,3-thiazine/pyrazole derivative ligands: Synthesis, structural characterization and effect of coordination on the phagocytic activity of human neutrophils

The new ligands 2-(1-pyrazolil)-1,3-thiazine (PzTz), 2-(3,5-dimethyl-1-pyrazolil)-1,3-thiazine (DMPzTz) and 2-(3,5-diphenyl-1-pyrazolil)-1,3-thiazine (DPhPzTz) and the complexes [ZnCl₂(H₂O)(PzTz)] (1), [ZnCl₂(DMPzTz)] (2) and [ZnCl₂(DPhPzTz)] (3) have been isolated and then characterized by elemental analysis, IR spectra and UV-Vis spectroscopy. Besides, the crystal structure of ligands PzTz and DPhPzTz and complexes 1-3 have been determined by single-crystal X-ray diffraction. In 1, the geometry around the Zn(II) atom can be considered a highly distorted trigonal bipyramid, with the metallic atom bonded to two chlorine atoms, one water molecule and one bidentate PzTz ligand. In 2 and 3, the environment around the metal ion can be described as a distorted tetrahedron with the zinc atom coordinated to one bidentate organic ligand molecule and two chloro ligands. In addition, the phagocytic function of human neutrophils treated with complexes 1-3, their organic ligands and ZnCl₂ has been evaluated. The activity of cells enhanced in samples treated with 1, 2 and 3 with respect to the ones to which the inorganic salt, PzTz, DMPzTz or DPhPzTz were added.     

Trimethyl borate/magnesium halide complex-induced one-pot homologation reactions of isoquinoline with dialkyl-TMP-zincate

Novel one-pot homologation reactions of isoquinoline with lithium dialkyl-TMP-zincate⋅2MgBrCl/trimethyl borate are described. 1-Alkylisoquinolines (2, 3A, 4A, 5A, 6, and 7) and 1-alkyl-3,4-dihydroisoquinolines (3B, 4B, and 5B) are easily prepared under the presented reaction conditions. The role of the B(OMe)₃/MgBrCl complex is examined in these homologation reactions. The specific reaction mechanisms, including 1,2-migration of the alkyl ligands from 1-isoquinolylzincates, are proposed. The migratory aptitudes of ligands of 1-isoquinolylzincates are also discussed.     

Di- and tetracarboxylate ligands for highly luminescent terbium(III) complexes on the basis of sulfonylcalix[4]arene scaffold

New di- (2) and tetracarboxylate ligands (4) were prepared on a sulfonylcalix[4]arene platform by O-alkylation of thiacalix[4]arene with ethyl bromoacetate, followed by hydrolysis of the ester function and oxidation of the sulfide bridges. The sulfonyl-based ligands 2 and 4 formed luminescent 1:1 complexes with terbium(III) ion having higher luminescent quantum yield (Φ = 0.29₁ and 0.28₇, respectively) than 1:1 complexes of the corresponding thiacalix[4]arene-based di- (1) and tetracarboxylate ligands (3) (Φ = 0.03₈ and 0.00₃, respectively), implying higher efficiency of sulfonyl ligands (2 and 4) than those of thia ligands (1 and 3) in the energy transfer process.     

Syntheses and coordination chemistry of methylpyridylphosphine oxide ligands with copper(II)

The coordination properties of three heterofunctional phosphine oxide ligands, 2-methylpyridyldiphenylphosphine oxide (L1), phenylphosphino-bis-2-methylpyridine oxide (L2) and phenylphosphino-bis-2-methylpyridine N,N′,P-trioxide (L3) with Cu(II) is described. The X-ray crystal structures of the compounds display a distorted octahedral geometry, which exhibit Jahn–Teller distortions. In compounds 1 and 2, the L1 and L2 ligands react with Cu(BF₄)₂ in a 2:1 ligand to metal ratio, respectively, with the BF₄ anions interacting with the metal center. L3 reacts with Cu(BF₄)₂ in 1:1 and 2:1 ligand/metal ratios to form compounds 3 and 4, respectively. Addition of either 2,2′-bipyridine or 4,4′-bipyridine to reaction solutions containing Cu(BF₄)₂ and L3 produces a discrete molecule (5) and a polymeric structure (7), respectively. The reaction of both bipyridines in the presence of Cu(BF₄)₂ and L3 gives rise to a discrete molecule (6) characterized by two octahedral coppers interconnected by the 4,4′-bipyridine. The electrochemical and photophysical properties of all compounds were investigated by cyclic voltammetry (CV) and UV–Vis, as they exhibited no emission or excitation in fluorimetric experiments.     

Selective recognition of sodium cyanide and potassium cyanide by diaza-crown ether-capped Zn-porphyrin receptors in polar solvents

Two new ditopic porphyrin receptors Zn1, incorporating a diaza-15-crown-5 unit, and Zn2, incorporating a diaza-18-crown-6 unit, have been prepared and characterized. UV-vis study in polar methanol has revealed that Zn1 is able to selectively recognize sodium cyanide over potassium cyanide (the ratio of their binding constant is ca. 56), whereas Zn2 exhibits a higher binding affinity for potassium cyanide over sodium cyanide (the ratio of their binding constant is ca. 12). In contrast, both receptors display substantially weaker binding affinity for sodium thiocyanate and potassium thiocyanate presumably due to a monotopic binding fashion.     

Syntheses, spectroscopic and structural characterizations and metal ion binding properties of Schiff bases derived from 4′-aminobenzo-15-crown-5

A series of benzyloxybenzaldehyde derivatives (1-4) were synthesized by the reactions of 4-(bromomethyl)benzonitrile with 4-hydroxy-3-methoxybenzaldehyde (vanillin), 2-hydroxy-3-methoxybenzaldehyde (o-vanillin), 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-5-methoxybenzaldehyde. Condensation reactions among the new benzyloxybenzaldehyde derivatives (1-4) with 4′-aminobenzo-15-crown-5 yielded the new Schiff base compounds (5-8). Sodium complexes (5a-8a) and potassium complexes (5b-8b) were prepared with NaClO₄ and KI, respectively. All of these synthesized compounds were characterized on the basis of FT-IR, ¹H and ¹³C NMR, mass spectrometry and elemental analyses data. The solid state structures of compounds 8 and 5a were determined by X-ray crystallography. The extraction abilities of compounds 5-8 were also evaluated in CH₂Cl₂ by using several main group and transition metal picrates, such as Na⁺, K⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cu²⁺ and Zn²⁺.