Novel Thiourea Ligands-Synthesis, Characterization and Preliminary Study on Their Coordination Abilities.

Two series of polydentate ,,-ligands containing thiourea fragments attached to a -cresol scaffold, unsymmetrical mono-acylated bis-amines and symmetrical bis-thioureas, are obtained by common experiments. It is observed that the reaction output is strongly dependent on both bis-amine and thiocarbamic chloride substituents. The products are characterized by 1D and 2D NMR spectra in solution and by single crystal XRD.

Aliquat 336 in Solvent Extraction Chemistry of Metallic ReO Anions.

A study of the liquid-liquid extraction of ReO anions from hydrochloric acid solutions using the ionic liquid Aliquat 336 (QCl: trialkyl(C-C)methylammonium chloride) via the well-known method of slope analysis along with the determination of the process parameters is presented. This study employs CCl, CHCl and CH as diluents. This study was carried out at room temperature (22 ± 2) °C and an aqueous/organic volumetric ratio of unity.

Functionalization of 2-Mercapto-5-methyl-1,3,4-thiadiazole: 2-(ω-Haloalkylthio) Thiadiazoles vs. Symmetrical Bis-Thiadiazoles.

A study on the functionalisation of 2-mercapto-5-methyl-1,3,4-thiadiazole has been conducted, yielding two series of products: 2-(ω-haloalkylthio)thiadiazoles and symmetrical bis-thiadiazoles, with variable chain lengths. The experimental conditions were optimised for each class of compounds by altering the base used and the reagents' proportions, leading to the development of separate protocols tailored to their specific reactivity and purification needs. The target halogenide reagents and bis-thiadiazole ligands were obtained either as single products or as mixtures easily separable by chromatography.

New Sustainable Solvent Extraction Pathways for Rare Earth Metals via Oximes Molecules.

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid-liquid extraction, commonly applied in the separation science of 4f and 5f-ions acidic chelating compounds, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), and 2-thenoyltrifluoroacetone (HTTA) alone and in combination with two synergistic agents, -hexamethylpropyleneamine oxime (S2: HM-PAO) and its bis-imine precursor (S1: pre-HM-PAO), are presented. The interaction between the two extractants (acidic/neutral) in deuterochloroform was studied using H, C, and H-H NOESY experiments.

Polydentate ,-Ligands Possessing Unsymmetrical Urea Fragments Attached to a -Cresol Scaffold.

In this study, three series of polydentate ,-ligands possessing unsymmetrical urea fragments attached to a -cresol scaffold are obtained, namely mono- and bi-substituted open-chain aromatics, synthesised using a common experiment, as well as fused aryloxazinones. Separate protocols for the preparation of each series are developed. It is found that in the case of open-chain compounds, the reaction output is strongly dependent on both bis-amine and carbamoyl chloride substituents, while oxazinones can be effectively obtained via a common protocol.

Mutual Solubilities between Ethylene Glycol and Organic Diluents: Gas Chromatography and NMR.

In this work, the mutual solubilities of sets of organic diluents (CHCl, CH, CHCl, CCl, CH, and n-hexane) with the organic compound ethylene glycol are investigated via gas chromatography (GC). The experimental data measured for these binary organic systems are used to adjust the future nonaqueous systems for the solvent extraction of various metals with ligands. The obtained results showed that the solubility of ethylene glycol decreased in the order CHCl > CH > CHCl > CCl(0%) ≈ CH ≈ n-hexane.

Optical Rotation-A Reliable Parameter for Authentication of Honey?

The controversial question of whether optical rotation data can be used to distinguish floral from honeydew honey was investigated. Specific optical rotation angles were determined for 41 honey samples, including floral, honeydew, and adulterated honey, indicating that moderate to high positive optical rotation angles were found for all adulterated samples measured. A strong correlation between the sugar profile and the specific optical rotation angle of honey was confirmed, and a method based on C NMR metabolomics was proposed to calculate specific optical rotation angles with good correlation with the experimental values.

Small Heterocyclic Ligands as Anticancer Agents: QSAR with a Model G-Quadruplex.

G-quadruplexes (GQs) have become valid targets for anticancer studies in recent decades due to their multifaceted biological function. Herewith, we aim to quantify interactions of potential heterocyclic ligands (Ls) with model GQs. For seven 4-aminoquinazolines and three 2-heteroaryl perimidines, seven of this ten-membered group so far unknown, we use routine quantum chemical modeling.

Recent Progress in Metal-Free Direct Synthesis of Imidazo[1,2-]pyridines.

This Mini-Review highlights the most effective protocols for metal-free direct synthesis of imidazo[1,2-]pyridines, crucial target products and key intermediates, developed in the past decade. The emphases is given on the ecological impact of the methods and on the mechanistic aspects as well. The procedures efficiently applied in the preparation of important drugs and promising drug candidates are also underlined.

Spontaneous conversion of -tosylates of 2-(piperazin-1-yl)ethanols into chlorides during classical tosylation procedure.

A direct conversion of piperazinyl ethanols into chlorides via a classical -tosylation protocol is observed. The acceleration of the transformation by the piperazine unit is demonstrated. It is found that the reaction goes via the corresponding -tosylate, which converts spontaneously into chloride with different rate depending on the substrate structure.

Data on the synthesis and characterization of two novel polydentate ligands possessing unsymmetrical NH-urea fragment.

The data represent the synthesis and structural characterization of two novel polydentate ligands possessing unsymmetrical NH-urea fragment: an open-chain substituted aromatic compound with unsymmetrical urea and secondary amine units () and fused aryloxazinone with unsymmetrical urea fragment (). The data include the analyzed NMR spectra, turbo-spray mass spectra, melting points and R-values. 1D and 2D NMR spectra are given in the article.

Prenylated β-diketones, two new additions to the family of biologically active Hypericum perforatum L. (Hypericaceae) secondary metabolites.

Two novel β-diketones, 2,6,9-trimethyl-8-decene-3,5-dione (A) and 3,7,10-trimethyl-9-undecene-4,6-dione (B), were identified from the renowned medicinal plant Hypericum perforatum L. The structures of β-diketones A and B were corroborated by syntheses (4 steps starting from methyl acetoacetate, overall yields 30% and 23%, respectively). In solution, these β-diketones predominantly exist as two rapidly interconverting β-keto-enol tautomers.

Synthesis of Chiral Cyclopentenones.

The cyclopentenone unit is a very powerful synthon for the synthesis of a variety of bioactive target molecules. This is due to the broad diversity of chemical modifications available for the enone structural motif. In particular, chiral cyclopentenones are important precursors in the asymmetric synthesis of target chiral molecules.

Coordination Chemistry of Europium(III) Ion Towards Acylpyrazolone Ligands.

Two Eu(III) complexes were synthesized using 4-acylpyrazolone ligands: 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one (HPMMBP) and 3-methyl-1-phenyl-4-(4-phenylbenzoyl)-pyrazol-5-one (HPPMBP). The composition of the obtained solid complexes was determined as Eu(PMMBP)3·C2H5OH and Eu(PPMBP)3·3H2O based on elemental analysis and was further studied by IR, NMR and TG-TSC data. The lanthanoid complexation in solid state and in solution during liquid-liquid extraction (molecular diluent and ionic liquid) is discussed.

Controlled tautomeric switching in azonaphthols tuned by substituents on the phenyl ring.

A series of new tautomeric azonaphthols are synthesized and the possibilities for molecular switching are investigated using molecular spectroscopy, X-ray analysis and density functional theory quantum chemical calculations. Two opposite effects that influence switching are studied: attaching a piperidine sidearm, and adding substituents to the phenyl ring. On the one hand, the attached piperidine moiety stabilizes the enol form leading to a controlled shift of the equilibrium upon protonation.

Tautomerism of 4,4'-dihydroxy-1,1'-naphthaldazine studied by experimental and theoretical methods.

Background: The title compound belongs to the class of bis-azomethine pigments. On the basis of comparative studies on similar structures, insight into the complex excited state dynamics of such compounds has been gained. It has been shown, for example, that only compounds that possess hydroxyl groups are fluorescent, and that the possibility for cis-trans isomerisation and/or bending motions of the central bis-azomethine fragment allows for different non-radiative decay pathways.

(E)-1-(4-Meth-oxy-anthracen-1-yl)-2-phenyl-diazene.

The title compound, C(21)H(16)N(2)O, has an E-conformation about the diazene N=N bond. It is reasonably planar with the phenyl ring being inclined to the mean plane of the anthracene moiety [planar to within 0.077 (3) Å] by 6.

Gas-phase study of molecular switches based on tautomeric proton transfer.

The keto-enol tautomeric equilibrium in two newly developed molecular switches was studied by using various mass spectral techniques. In these two compounds, namely 4-(phenyldiazenyl)-2-(piperidin-1- ylmethyl)naphthalen-1-ol and 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4- (phenyldiazenyl)naphthalen-1-ol, the switching on/off states are achieved by a controlled shift of the tautomeric equilibrium. In the first compound, electron impact-mass spectrometry confirms that the unprotonated dye exists as an enol tautomer, while the electrospray ionization tandem mass spectrometry (ESI-MS/MS) experiment proves the clear shift to the keto tautomeric form under switching with acid addition.

Gas-phase tautomerism in hydroxy azo dyes - from 4-phenylazo-1-phenol to 4-phenylazo-anthracen-1-ol.

The tautomeric constants of a series of azo dyes were estimated in the gas phase by using electron ionization mass spectrometry. It was shown that the relative amount of the keto tautomer increases from 4-phenylazo-1-phenol to 4-phenylazo-anthracen-1-ol, thus confirming the quantum-chemical predictions. The existence of the enol tautomer of 4-phenylazo-anthracen-1-ol is shown for the first time by mass spectrometry in the gas phase.

Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol: verification of the responses of individual tautomers.

Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol (1) was studied by using electron ionization (EI) mass spectrometry on the basis of the fragmentations of the model enol and keto tautomers, where the movable proton is replaced by a methyl group. These fixed tautomers were obtained as an easy separable mixture by simple methylation of the cheap and easily accessible diazene (1). It was found that their EI mass spectral fragmentations are in full congruence with the already published theoretical predictions.

Simple transformation of crystalline chiral natural anions to liquid medium and their use to induce chirality.

New chiral ionic liquids can be prepared simply by combining the tetra-n-hexyl-dimethylguanidinium cation with readily available chiral anions and used as an asymmetric inducing agent as demonstrated for catalytic Rh(II) carbenoid C-H insertion and Sharpless dihydroxylation.

Microwave accelerated facile synthesis of fused polynuclear hydrocarbons in dry media by intramolecular Friedel-Crafts alkylation.

Fused polynuclear tetrahydro arenes are synthesised in a fast, simple, high yielding and regiospecific procedure by an intramolecular Friedel-Crafts alkylation in dry media under microwave irradiation of the corresponding 1-bromo-4-arylbutanes immobilised on silica. The observed reactivity is rationalised by molecular modelling studies which suggest the occurrence of a concerted mechanism.

Determination of the diastereoisomeric purity of D,L- and meso-HM-PAO by 13C-NMR spectroscopy.

D,L-hexamethylpropyleneamine oxime (HM-PAO) is well known to be the effective isomer when HM-PAO is used as a radiopharmaceutical. Its diastereoisomeric purity is of great importance because meso-impurity decreases the concentration of the 99mTc-complex in the brain. The described investigation shows that 13C-NMR spectroscopy is a suitable analytical method for the determination of the diastereoisomeric purity of HM-PAO.