Electronic structure of substituted benzoquinones and quinonechloroimides

The electronic structures of several halogen substituted bezoquinones and benzoquinoneimines have been studied by HeI/HeII photoelectron spectroscopy and Green's function calculations. The information on the electronic structure is discussed in the context of their electron-transfer properties and biological activity.     

Assembly between gold-thiolate nanoparticles and the organometallic cluster [Fe(eta5-C5H5)(mu3-CO)]4 toward redox sensing of oxo-anions

Covalent assembly between gold-thiolate nanoparticles (AuNPs) and the cluster [Fe(eta(5)-C(5)H(5))(mu(3)-CO)](4), 1, can be achieved either by direct Brust-Schriffin-type synthesis using a mixture of undecanethiol and a thiol functionalized with , or by substitution of undecanethiolate ligands in AuNPs by thiolate ligands functionalized with ; cyclic voltammetry of these AuNPs functionalized with allows us to recognize and titrate the oxo-anions H(2)PO(4)(-) and ATP(2-).     

Separation of chlorins and carotenoids in capillary electrophoresis

The present study reports the investigation of capillary electrophoresis (CE) for the separation of the photosynthetic pigments (chlorophyll derivatives as well as carotenoids) together. Various CE methods, such as micellar electrokinetic chromatography, capillary electrokinetic chromatography, and nonaqueous capillary electrophoresis (NACE) are tested, with coated and uncoated capillary columns to evaluate optimal separation conditions using diode array detection. The effect of different type and composition of organic solvents and surfactants on the separation is discussed. Detection limits are found in the range of 1.14-2.45 ppm. According to the system suitability results, the most effective separation is observed using NACE with Aliquat 336 as cationic surfactant in coated capillary and mixture of MeOH-ACN-THF (5:4:1, v/v/v) as solvent. Quantitative evolution is investigated, and recovery percentage values are found to be 96.7-102%.     

Second generation of primaquine ureas and bis-ureas as potential antimycobacterial agents

Molecular Diversity - Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of...     

Two cubic polymorphs of AlGeLi

Aluminium germanium lithium, AlGeLi, crystallizes in two cubic dimorphs. The structure of the F3m form, already inferred from powder data, has been confirmed by both powder and single‐crystal X‐ray diffraction studies. The second dimorph, not previously identified, adopts a disordered centrosymmetric structure with space group Fmm.     

Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid?Cbase equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(??⁶-p-cymene)Ru (L^1?3)Cl₂] where L¹?=?3-acetylpyridine (1), L²?=?4-acetylpyridine (2) and L³?=?2-amino-5-chloropyridine (3), then [(??⁶-p-cymene)Ru(HL⁴)Cl₂] with HL⁴?=?isonicotinic acid (4); [(??⁶-p-cymene)Ru(HL^5?8)Cl] where H₂L⁵?=?2,3-pyridine dicarboxylic acid (5), H₂L⁶?=?2,4-pyridine dicarboxylic acid (6), H₂L⁷?=?2,5-pyridine dicarboxylic acid (7) and H₂L⁸?=?2,6-pyridine dicarboxylic acid (8) have been studied. pK _a values were determined by potentiometry at 25?°C and constant ionic strength of 0.1?M NaNO₃. The assumed equilibria were confirmed by UV and ¹H-NMR spectroscopy.     

Electronic structures of methylated azaferrocenes and their borane adducts: photoelectron spectroscopy and electronic structure calculations

The preparation and crystal structure of a new 2,5-dimethylazaferrocene (DMAF) adduct of borane (DMAF-BH(3)) are reported. The electronic structures of 1,2,3,4,5-pentamethylazaferrocene (PMAF), its borane adduct 1,2,3,4,5-pentamethylazaferrocene-BH(3) (PMAF-BH(3)) and of DMAF-BH(3) have been studied by HeI-HeII UV photoelectron spectroscopy (UPS) and high-level DFT methods. UPS data reveal the influence of borane and methyl substitution on the electronic structures of azaferrocenes, which have been rationalized by inductive and hyperconjugative effects. UPS data also allow for the estimation of azaferrocene lone-pair stabilization upon coordination to borane, and suggest that pyridine is a slightly stronger sigma donor toward BH(3) than either azaferrocene studied. UV-Vis spectroscopic data for the radical cation of PMAF were also obtained and compared with the UPS data.     

Catalytic activity of halohydrin dehalogenases towards spiroepoxides

A novel activity of halohydrin dehalogenases towards spiroepoxides has been found. The enzyme from Arthrobacter sp. (HheA) catalysed highly regioselective azidolysis of spiroepoxides containing 5, 6 and 7-membered cycloalkane rings, while the enzyme from Agrobacterium radiobacter (HheC), besides high regioselectivity, also displayed moderate to high enantioselectivity (E up to >200) that can be applied for the kinetic resolution of chiral spiroepoxides. The orientations of spiroepoxides in the active site of halohydrin dehalogenases were studied by quantum-chemical calculations and docking simulations. Analyses of the complexes obtained revealed the origins of diastereoselectivity and enantioselectivity of the investigated biotransformations.     

Prediction of diesel fuel properties by vibrational spectroscopy using multivariate analysis

Partial least squares regression (PLS) calibration models based on Fourier transform infrared (FTIR-ATR) and Raman spectra (FT-Raman) were applied to the rapid and accurate simultaneous determination of the main properties of diesel fuels. Training sets were composed of over ninety commercial diesel fuel samples. The methods use baseline-uncorrected, raw FTIR-ATR and FT-Raman spectra. Two spectral regions were studied: full spectral region and “fingerprint” region. The models were validated using the cross-validation process. Based on the correlation coefficient and root mean square error of cross validation (RMSECV) values the both developed calibration models, PLS/FTIR-ATR and PLS/FT-Raman, were very accurate and comparable with standard testing methods. The following diesel fuel properties may be confidently estimated: cetane number, cetane index, density, viscosity, distillation temperatures at 10% (T10), 50% (T50) and 90% (T90) recovery, as well as the contents of total aromatics and polycyclic aromatic hydrocarbons. As compared to the “fingerprint” spectral region, the PLS/FTIR-ATR model using full spectral region displayed slightly better performances with the most of the correlation coefficient values above 0.98.     

Trans-annular interactions in morpholines: A photoelectron spectroscopic study

The He I and He II photoelectron spectra of 4-methylmorpholine, 4-morpholinecarbonitrile, and 4-morpholinepropionitrile have been measured. The electronic structure and heteroatom lone pair interactions, in particular, were analyzed with the aid of HeII/HeI intensity variations, comparison with the spectra of related compounds, and AM1 semiempirical calculations. We present an example of combined inductive and resonance interactions operating in the morpholine ring system.