Steric structure and thermodynamic aspects of the complexes of dysprosium(iii) with aminobenzoic acids in aqueous solutions

Steric structures of dysprosium(III) aminobenzoate complexes with the 11 and 12 molar ratio in aqueous solutions were determined on the basis of pH-metric and paramagnetic birefringence data. An increase in conjugation observed for the series of the acids,viz., benzoic,meta-, ortho-, andpara-aminobenzoic acids, results in the increased stability of the complexes with the 11 and 12 composition. In the case ofpara-aminobenzoic acid, the polyhedra [DyL(H₂O)₆]²⁺ and [DyL₂(H₂O)₄]⁺ are cubes with the ligands coordinated to one and two edges, respectively. In the case ofmeta-aminobenzoic acid, the polyhedra [DyL(H₂O)₆]²⁺ and [DyL₂(H₂O)₄]⁺ are a dodecahedron with the ligand coordinated to one edge and a square anti-prism with the ligands coordinated to two edges, respectively. In the case ofortho-aminobenzoic acid, both the 11 and 12 complexes have structures that are intermediate between the structures ofmeta- andpara-aminobenzoic acids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1767–1770, October, 1994.     

Substrate-induced luminescence response of terbium-containing polymeric vesicles doped with the tetra- and bis-1,3-diketone derivatives of calix[4]arenes bearing nonyl substituents at the lower rims

Russian Chemical Bulletin - Polymeric aggregates (~100 nm) based on polydiacetylenic acid doped with the luminescent TbIII complexes with the tetra- and bis-1,3-diketonate derivatives of...     

Reactions of heteroaromatic chromophores with lanthanide complexes of p-sulfonatothiacalix[4]arene

The conditions for the formation of heteroleptic complexes of a lanthanide(iii) ion (Ln = La, Gd, and Tb) with p-sulfonatothiacalix[4]arene and a heteroaromatic chromophore in water were found using X-ray diffraction analysis, pH-metry, ¹H NMR and UV—Vis spectroscopy, and nuclear magnetic relaxation. In the resulting complexes, the heteroaromatic chromophore is in the calix[4]arene cavity and the lanthanide ion is coordinated by the electron-donating groups of the upper or lower calix[4]arene rim. Emission spectroscopic studies revealed changed emission properties of Tb^III ions in the terbium(iii)—p-sulfonatothiacalix[4]arene—bipy complex. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1871–1878, September, 2008.     

Electroswitchable binding of [Co(dipy)<Subscript>3</Subscript>]<Superscript>3+</Superscript> and [Fe(dipy)<Subscript>3</Subscript>]<Superscript>2+</Superscript><Emphasis Type="Italic">n</Emphasis>-sulfonato(thia)calix[4]arenas

The methods of cyclic voltammetry, electrolysis, and spectrophotometry were used to study electrochemical properties of (TCAS + Fe³⁺ + dipy), (CCAS + Fe³⁺ + dipy), and (CCAS + Fe³⁺ + [Co(dipy)₃]³⁺) triple systems (where TCAS is n-sulfonatothiacalix[4]arene, CCAS is tetracarboxylate n-sulfonatocalix[4]arene, and dipy = α,α′-dipyridyl) in an aqueous solution. One-electron reduction of Fe(III) in the (TCAS + Fe³⁺ + dipy) system at pH 2.5 results in electroswitching of iron ions from the lower TCAS ring to the upper ([Fe(dipy)₃]²⁺). Reverse electrochemical switching of the system is impossible due to mediator ([Fe(dipy)₃]^2+/3+) oxidation of TCAS. Reverse electroswitching of Fe(III) ions from unbound to bound state as ([Fe(dipy)₃]²⁺) with CCAS has been revealed in the system (CCAS + Fe³⁺ + dipy) (pH 1.7) upon single-electron transfer, whereas reversible electroswitching by the upper rim of CCAS from one complex ion ([Co(dipy)₃]³⁺) to another ([Fe(dipy)₃]²⁺) has been demonstrated in the system ([Co(dipy)₃]³⁺ + CCAS + Fe³⁺ upon double-electron transfer. In all systems, electric switching was accompanied by synchronous color switching.     

Electricoswitchable bonding of metal ions and complexes by calixarenes

The results of authors on designing electroswitchable supramolecular systems based on calix[4]arenes, calix[4]resorcinols, and transition metal ions and complexes are summarized. We consider systems in which the switching is performed owing to electrochemical reactions both of groups grafted to the macrocycle and bound substrates. Examples of electrochemically switchable luminescence are given.     

Solubility, Acid–Base and Complexation Properties of Calix[4]resorcinarene in Aqueous Solutions of Nonionic Surfactants

Solubility and acid–base properties of calix[4]resorcinarene (H₈L) in aqueous solutions of nonionic surfactants Triton X-100, Triton X-405, and Brij-35, as well as isopropanol were studied by pH-potentiometry. The dependence of the amount of a nonionic surfactant necessary to dissolve H₈L on the length of ethylene oxide chain was found. The dissociation constants of macrocycle for the first four steps are low sensitive to the medium nature (micellar or water–alcohol solutions). Complexation ability of the [H_{8 – n} L] ^n– anions with respect to tetramethyl- and tetraethylammonium, N-methylpyridinium, and [Co(En)₂(C₂O₄)]⁺ cations was studied by pH-potentiometry. A noticeable increase in the selectivity of guest–host binding was found on going from aqueous or water–alcohol to micellar solutions.     

Phenolic compounds,essential oil composition,and antioxidant activity of Angelica purpurascens (Avé-Lall.) Gill

In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•⁺), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•⁺, DPPH•, and FRAP activities (IC₅₀: 0.05 ± 0.0001 mg/mL, IC₅₀: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC₅₀: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source.     

Activation of the S-S bond in diphenyl disulfide by nickel complexes and its reaction with butadiene

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, p. 747, March, 1989.     

The Inclusion Properties of a New Watersoluble Sulfonated Calix[4]resorcinarene towards Alkylammonium and N-Methylpyridinium Cations

The inclusion behaviour of a new water-soluble sulfonated calix[4]resorcinarene towards alkylammonium and N-methylpyridinium cations has been investigated on the basis of ¹H NMR spectroscopy and pH-potentiometry data. The inclusion of the N-methylpyridinium cation has been found to be dependent on pH with the preferable inclusion of the methyl substituent in alkaline and the aromatic ring in neutral aqueous media.