Correction: Miranda et al. Anion Binding by Fluorescent Ureido-Hexahomotrioxacalix[3]arene Receptors: An NMR, Absorption and Emission Spectroscopic Study. 2022, , 3247.

In the original publication [...

Critical Analysis of Association Constants between Calixarenes and Nitroaromatic Compounds Obtained by Fluorescence. Implications for Explosives Sensing.

The binding behaviour of two ureido-hexahomotrioxacalix[3]arene derivatives bearing naphthyl () and pyrenyl () fluorogenic units at the lower rim towards selected nitroaromatic compounds (NACs) was evaluated. Their affinity, or lack of it, was determined by UV-Vis absorption, fluorescence and NMR spectroscopy. Different computational methods were also used to further investigate any possible complexation between the calixarenes and the NACs.

Anion Binding by Fluorescent Ureido-Hexahomotrioxacalix[3]arene Receptors: An NMR, Absorption and Emission Spectroscopic Study.

Fluorescent receptors (-) based on (thio)ureido-functionalized hexahomotrioxacalix[3]arenes were synthesised and obtained in the partial cone conformation in solution. Naphthyl or pyrenyl fluorogenic units were introduced at the lower rim of the calixarene skeleton via a butyl spacer. The binding of biologically and environmentally relevant anions was studied with NMR, UV-vis absorption, and fluorescence titrations.

Experimental and Computational Study of a Tetraazamacrocycle Bis(aryloxide) Uranyl Complex and of the Analogues {E═U═NR} (E = O and NR).

The reaction of [U(κ-{(ArO)Me-cyclam})I][I] (H{(ArO)Me-cyclam} = 1,8-bis(2-hydroxy-3,5-di--butyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane) with 2 equiv of NaNO in acetonitrile results in the isolation of the uranyl complex [UO{(ArO)Me-cyclam}] () in 31% yield, which was fully characterized, including by single-crystal X-ray diffraction. Density functional theory (DFT) computations were performed to evaluate and compare the level of covalency within the U═E bonds in and in the analogous -bis(imido) [U(κ-{(ArO)Me-cyclam})(NPh)] () and -oxido-imido [U(κ-{(ArO)Me-cyclam})(O)(NPh)] () complexes. Natural bond orbital (NBO) analysis allowed us to determine the mixing covalency parameter λ, showing that in , where both U-O and U-N bonds are present, the U-N bond registers more covalency with regard to , and the opposite is seen for U-O with respect to .

Conventional vs. Microwave- or Mechanically-Assisted Synthesis of Dihomooxacalix[4]arene Phthalimides: NMR, X-ray and Photophysical Analysis.

Direct -alkylation of -butyldihomooxacalix[4]arene () with -(bromopropyl)- or -(bromoethyl)phthalimides and KCO in acetonitrile was conducted under conventional heating (reflux) and using microwave irradiation and ball milling methodologies. The reactions afforded mono- and mainly distal di-substituted derivatives in the cone conformation, in a total of eight compounds. They were isolated by column chromatography, and their conformations and the substitution patterns were established by NMR spectroscopy (H, C, COSY and NOESY experiments).

Dihomooxacalix[4]arene-Based Fluorescent Receptors for Anion and Organic Ion Pair Recognition.

Fluorescent dihomooxacalix[4]arene-based receptors -, bearing two naphthyl(thio)ureido groups at the lower rim via a butyl spacer, were synthesised and obtained in the cone conformation in solution. The X-ray crystal structures of 1,3- () and 3,4-dinaphthylurea () derivatives are reported. Their binding properties towards several anions of different geometries were assessed by H-NMR, UV-Vis absorption and fluorescence titrations.

Ditopic Receptors Based on Dihomooxacalix[4]arenes Bearing Phenylurea Moieties With Electron-Withdrawing Groups for Anions and Organic Ion Pairs.

Two bidentate dihomooxacalix[4]arene receptors bearing phenylurea moieties substituted with electron-withdrawing groups at the lower rim via a butyl spacer (CF-Phurea and NO Phurea ) were obtained in the cone conformation in solution, as shown by NMR. The X-ray crystal structure of is reported. The binding affinity of these receptors toward several relevant anions was investigated by H NMR, UV-Vis absorption in different solvents, and fluorescence titrations.

Synthesis and Characterization of Isosorbide-Based Polyurethanes Exhibiting Low Cytotoxicity Towards HaCaT Human Skin Cells.

The synthesis of four samples of new polyurethanes was evaluated by changing the ratio of the diol monomers used, poly(propylene glycol) (PPG) and D-isosorbide, in the presence of aliphatic isocyanates such as the isophorone diisocyanate (IPDI) and 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI). The thermal properties of the four polymers obtained were determined by DSC, exhibiting values in the range 55⁻70 °C, and their molecular structure characterized by FTIR, ¹H, and C NMR spectroscopies. The diffusion coefficients of these polymers in solution were measured by the Pulse Gradient Spin Echo (PGSE) NMR method, enabling the calculation of the corresponding hydrodynamic radii in diluted solution (1.

Selective Binding of Spherical and Linear Anions by Tetraphenyl(thio)urea-Based Dihomooxacalix[4]arene Receptors.

Three novel tetra(thio)ureido dihomooxacalix[4]arene anion receptors (phenylurea 4a, phenylthiourea 4b, and tert-butylurea 4c) were synthesized and obtained in the cone conformation in solution, as shown by NMR studies. The X-ray crystal structure of 4c is reported. The host-guest properties of these receptors toward several anions were investigated by H NMR titrations.

Competition between Hydrogen Bonding and Proton Transfer during Specific Anion Recognition by Dihomooxacalix[4]arene Bidentate Ureas.

Competition between hydrogen bonding and proton transfer reactions was studied for systems composed of electrogenerated dianionic species from dinitrobenzene isomers and substituted dihomooxacalix[4]arene bidentate urea derivatives. To analyze this competition, a second-order ErCrCi mechanism was considered where the binding process is succeeded by proton transfer and the voltammetric responses depend on two dimensionless parameters: the first related to hydrogen bonding reactions, and the second one to proton transfer processes. Experimental results indicated that, upon an increase in the concentration of phenyl-substituted dihomooxacalix[4]arene bidentate urea, voltammetric responses evolve from diffusion-controlled waves (where the binding process is at chemical equilibrium) into irreversible kinetic responses associated with proton transfer.

Site-Specific Description of the Enhanced Recognition Between Electrogenerated Nitrobenzene Anions and Dihomooxacalix[4]arene Bidentate Ureas.

Electron transfer controlled hydrogen bonding was studied for a series of nitrobenzene derivative radical anions, working as large guest anions, and substituted ureas, including dihomooxacalix[4]arene bidentate urea derivatives, in order to estimate binding constants (Kb) for the hydrogen-bonding process. Results showed enhanced Kb values for the interaction with phenyl-substituted bidentate urea, which is significantly larger than for the remaining compounds, e.g.

Chemical, radiochemical and biological studies of new gallium(III) complexes with hexadentate chelators.

New N4O2-donor acyclic chelators 2-[[2-[2-(3,5-dimethylpyrazol-1-yl)ethyl-[2-[(2-hydroxyphenyl)methylamino]ethyl]amino]ethylamino]methyl]phenol (H2L(pz*,NH)) and 2-[[2-[2-[(2-hydroxyphenyl)methylamino]ethyl-(2-pyridylmethyl)amino]ethylamino]methyl]phenol (H2L(py,NH)) were obtained upon introduction of pyridyl or pyrazolyl coordinating units at the central nitrogen atom of diethylenetriamine (dien) and by functionalization of its terminal amines with phenol groups. The coordination behavior of H2L(pz*,NH) and H2L(py,NH) was evaluated towards (nat)Ga/(67)Ga, aiming to assess their suitability to obtain Ga(iii) chelates relevant for biomedical applications. Single crystal X-ray diffraction analysis of the complexes [GaL(pz*,NH)](ClO4) and [GaL(py,NH)](ClO4) confirmed the presence of N4O2-hexadentate chelators with the phenoxide groups coordinated cis relatively to the pyridyl/pyrazolyl arms.

Bidentate urea derivatives of p-tert-butyldihomooxacalix[4]arene: neutral receptors for anion complexation.

Three new bidentate ureidodihomooxacalix[4]arene derivatives (phenyl 5a, n-propyl 5b, and tert-butyl 5c) were synthesized in four steps from the parent compound p-tert-butyldihomooxacalix[4]arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by (1)H NMR and UV-vis titrations. The structures and complexation energies of some complexes were also studied by DFT methods.

Quantitative 1H-NMR-metabolomics reveals extensive metabolic reprogramming and the effect of the aquaglyceroporin FPS1 in ethanol-stressed yeast cells.

A metabolomic analysis using high resolution 1H NMR spectroscopy coupled with multivariate statistical analysis was used to characterize the alterations in the endo- and exo-metabolome of S. cerevisiae BY4741 during the exponential phase of growth in minimal medium supplemented with different ethanol concentrations (0, 2, 4 and 6% v/v). This study provides evidence that supports the notion that ethanol stress induces reductive stress in yeast cells, which, in turn, appears to be counteracted by the increase in the rate of NAD+ regenerating bioreactions.

Electrophilic reactivity of tetrabromorhodamine 123 is bromine induced: convergent interpretation through complementary molecular descriptors.

Nucleophilic addition of water and of methanol to 3,6-diamino-2,4,5,7-tetrabromo-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, 4BrR123, yields respectively 2-(3,6-diamino-2,4,5,7-tetrabromo-9-hydroxy-9H-xanthen-9-yl)xanthyl benzoate, HO4BrR123 and 2-(3,6-diamino-2,4,5,7-tetrabromo-9-methoxy-9H-xanthen-9-yl)xanthyl benzoate, MeO4BrR123. The novel experimental results are addressed theoretically. The linear free energy relationship, LFER, second-order perturbation theory analysis of the natural bond orbital, NBO, and quantum theory of atoms in molecules, QTAIM, lead to the same conclusion: the electron-withdrawing effect of bonded Br atoms in 4BrR123 extremely enhances the molecular electrophilicity, as compared to 3,6-diamino-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, R123.

Alkylammonium cation complexation into the narrow cavity of dihomooxacalix[4]arene macrocycle.

How big should a calixarene macrocycle be for endo-cavity complexation to occur or to allow through-the-annulus threading? To answer these questions, a complete study on the complexation of primary and secondary (di)alkylammonium cations by 18-membered p-tert-butyldihomooxacalix[4]arene macroring has been performed in the presence of the "superweak" TFPB counterion. Thus, it was found that this macrocycle is currently the smallest calixarene able to host linear and branched alkylammonium guests inside its aromatic cavity. Molecular mechanics calculations revealed that this recognition event is mainly driven by a H-bonding interaction between the guest ammonium group and the host CH(2)OCH(2) bridge.

Amido/amine triazacyclononane-based zirconium complexes: syntheses, reactivity, and structures.

The reactions of [Zr(NMe2)4]2 with triamido-triazacyclonane ligand precursors, {NH(Ph)SiMe2}3tacn (H3N3[9]N3) and {NH(C6H4F)SiMe2}3tacn (H3N3-F[9]N3), led to the formation of complexes [Zr(NMe2)2{N(Ph)SiMe2}2{NH(Ph) SiMe2}tacn], 1, and [Zr(NMe2)2{N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2} tacn], 2, where the zirconium is coordinated to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [{N(Ph')SiMe2}2{NH(Ph')SiMe2}tacn]2-, that formed from deprotonation of two amine pendent arms of the ligands' precursors. The third pendent arm of H3N3[9]N3 and H3N3-F[9]N3 remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the synthesis of [Zr(NMe2){N(Ph)SiMe2}2tacn], 3, that results from the cleavage of the N-Si bond of the original neutral pendent arm.

Euphoportlandols A and B, tetracylic diterpene polyesters from Euphorbia portlandica and their anti-MDR effects in cancer cells.

Two new tetracyclic diterpene polyesters, euphoportlandols A (1) and B (2), have been isolated along with 12 known tetracyclic triterpenes from an acetone extract of Euphorbia portlandica. Their structures were established as 5alpha,11alpha,14alpha,17-tetraacetoxy-3beta-benzoyloxy-6beta,15beta-dihydroxy-9-oxoseget-8(12)-ene (1) and 5alpha,11alpha,14alpha,17-tetraacetoxy-3beta-benzoyloxy-6beta,15beta-dihydroxy-9-oxosegetane (2), respectively, by spectroscopic data interpretation. Compounds 1 and 2 were evaluated for their ability to inhibit multidrug resistance in cancer cells.

Titanium(III) trisamidotriazacyclononane: reactions with C60 and radicals.

The reaction of titanium trisamidotriazacyclononane, [Ti{N(Ph)SiMe2}3tacn] (1), with C60 led to the synthesis of [Ti{N(Ph)SiMe2}3tacn]C60 (2) in high yield. Treatment of 2 with PhCH2Br led to the formation of [Ti{N(Ph)SiMe2}3tacn]Br and the radical PhCH2C60 (3). The reaction of CH3I with 1 gives two products.

Ion pairing in Ti(IV) trisamidotriazacyclononane compounds.

[Ti[N(Ph)SiMe2]3-tacn]X complexes (X = Cl, 1; I, 2; PF6, 3; BPh4, 4) were studied by NMR and electron absorption and emission methods, which showed that these compounds exist in bromobenzene and dichloromethane solutions as ion pairs. The significant modifications observed in the proton resonances of tacn in C6D5Br, which follow the sequence BPh(4-) > or = PF(6-) > or = I- approximately Cl-, are a qualitative indication of the strength of the interactions that depend on the anion. The reaction of 2 with LiNMe2 led to [Ti(NPh)[NPh(SiMe2)]2-tacn], 5, that forms upon attack of Me2N- at one SiMe2 group.

Euphopubescenol and euphopubescene, two new jatrophane polyesters, and lathyrane-type diterpenes from Euphorbia pubescens.

The structures of euphopubescenol and euphopubescene, two new macrocyclic jatrophane diterpene polyesters, isolated from the whole dried plant of Euphorbia pubescens, were established as 5alpha,8alpha,15beta-triacetoxy-3alpha-benzoyloxy -4alpha-hydroxy -9,14-dioxo-13beta H-jatropha-6(17),11 E-diene ( 1) and 3beta,7beta,8beta,9alpha,14alpha,15beta-hexaacetoxy-2beta H-jatropha-5 E,11 E-diene ( 2) by 1D- and 2D-NMR (COSY, HMQC, HMBC and NOESY), IR, EI-MS and EI-FTICR-MS. Two known lathyrane derivatives, jolkinol A ( 3) and jolkinol A ( 4), whose (13)C-NMR spectra were assigned, were also isolated. Compounds 1 - 3 have been evaluated for their ability to inhibit the in vitro growth of three human tumour cell lines representing different tumour types, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer).

Rearranged jatrophane-type diterpenes from euphorbia species. Evaluation of their effects on the reversal of multidrug resistance.

The rearranged jatrophane-type diterpenes ( 1 - 3), isolated from the Me (2)CO extracts of Euphorbia portlandica and Euphorbia segetalis, were examined for their effects on multidrug resistance (MDR) in mouse lymphoma cells. Compounds 2 and 3 revealed to be active with the latter being more active than the positive control verapamil, a known resistance modifier. The new compound 1, named portlandicine, was isolated from Euphorbia portlandica and its structure characterised by high-field NMR spectroscopic methods including 2D NMR techniques: COSY, HMQC, HMBC and NOESY.

Coordination of 2,2'-bipyridyl and 1,10-phenanthroline to yttrium and lanthanum complexes based on a scorpionate ligand.

Reaction of yttrium and lanthanum trichloride with 1 equiv of sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate and 1 equiv of 2,2'-bipyridine gives good yields of the complexes [MCl(2)(Tp(Me2))(C(10)H(8)N(2))] (M = Y (1), La (2)). The analogous compounds with 1,10-phenanthroline, [MCl(2)(Tp(Me2))(C(12)H(8)N(2))] (M = Y (3), La (4)), have been obtained by a similar procedure. The solid-state structures of 2-4 were determined by single-crystal X-ray diffraction and revealed that the compounds are all seven-coordinate with capped octahedral geometry.

Triamidotriazacyclononane complexes of group 3 metals. Synthesis and crystal structures.

Reaction of yttrium and lanthanide trichlorides (Ln = La, Eu, Yb) with 1 equiv of the trisodium salt of 1,4,7-tris(dimethylsilylaniline)-1,4,7-triazacyclononane (Na(3)[(SiMe(2)NPh)(3)-tacn](THF)(2)) gives good yields of the compounds [M[(SiMe(2)NPh)(3)-tacn]] (M = Y (1), Eu (3), Yb (4)) and [La[(SiMe(2)NPh)(3)-tacn](THF)] (2). Reduction of 3 with Na/Hg followed by recrystallization in the presence of diglyme yielded crystals of [Eu[(SiMe(2)NPh)(3)-tacn]][Na(diglyme)(2)] (5). Synthesis of the uranium(III) complex [U[(SiMe(2)NPh)(3)-tacn]] (6) is achieved by reaction of 1 equiv of Na(3)[(SiMe(2)NPh)(3)-tacn](THF)(2) with uranium triiodide.

Li, Ti(III), and Ti(IV) trisamidotriazacyclononane complexes. Syntheses, reactivity, and structures.

The preparations of 1,4,7-(NHPhSiMe(2))(3)-1,4,7-triazacyclononane (H(3)N(3)-tacn) and its lithium and sodium derivatives are described. The X-ray structure of the THF adduct of the lithium derivative, Li(3)N(3)-tacn(THF)(2), shows that one of the macrocycle pendant arms is bent to allow the coordination of the its lithium ion to two tacn amines. In solution, a fluxional process makes all the pending arms magnetically equivalent.