Polarized basis sets of Slater-type orbitals: H to Ne atoms

We present three Slater-type atomic orbital (STO) valence basis (VB) sets for the first and second row atoms, referred to as the VB1, VB2, and VB3 bases. The smallest VB1 basis has the following structure: [3, 1] for the H and He atoms, [5, 1] for Li and Be, and [5, 3, 1] for the B to Ne series. For the VB2 and VB3 bases, both the number of shells and the number of functions per shell are successively increased by one with respect to VB1. With the exception of the H and Li atoms, the exponents for the VB1 bases were obtained by minimizing the sum of the Hartree-Fock (HF) and frozen-core singles and doubles configuration interaction (CISD FC) energies of the respective atoms in their ground state. For H and Li, we minimized the sum of the HF and CISD FC energies of the corresponding diatoms (i.e., of H(2) or Li(2)) plus the ground-state energy of the atom. In the case of the VB2 basis sets, the sum that was minimized also included the energies of the positive and negative ions, and for the VB3 bases, the energies of a few lowest lying excited states of the atom. To account for the core correlations, the VBx (x = 1, 2, and 3) basis sets for the Li to Ne series were enlarged by one function per shell. The exponents of these extended (core-valence, CV) basis sets, referred to, respectively, as the CVBx (x = 1, 2, and 3) bases, were optimized by relying on the same criteria as in the case of the VBx (x = 1, 2, and 3) bases, except that the full CISD rather than CISD FC energies were employed. We show that these polarized STO basis sets provide good HF and CI energies for the ground and excited states of the atoms considered, as well as for the corresponding ions.     

Micellar liquid chromatography: suitable technique for screening analysis

The screening capability of micellar liquid chromatography (MLC) is discussed using the reported chromatographic data of several sets of compounds (amino acids, beta-blockers, diuretics, phenethylamines, phenols, polynuclear aromatic hydrocarbons, steroids and sulfonamides) and new results (sulfonamides and steroids). The chromatographic data are treated with an interpretive optimisation resolution procedure to obtain the best separation conditions. Usually, the pH and the concentration of surfactant (sodium dodecyl sulfate, SDS, or cetyltrimethylammonium bromide) for the optimal mobile phase were 2.5-3 and < 0.12 M, respectively. The nature and concentration of organic solvent depended on the polarity of the eluted compounds: a low volume fraction of propanol (approximately 1%, v/v) was useful to separate the amino acids, with log P(o/w) < -1 (where P(o/w) is the octanol-water partition coefficient). A greater concentration of this solvent (approximately 5-7%) was needed for compounds in the range -1 < log P(o/w) < 2, as with the studied diuretics and sulfonamides, and a high concentration of propanol (approximately 15%) or a low concentration of butanol (< 10%) had to be used for less polar compounds with 1 < log P(o/w) < 3, such as the beta-blockers. Pentanol (< 6%) was more suitable for the even less polar compounds with log P(o/w) > 3, such as the steroids. For basic drugs such as the phenethylamines (0 < log P(o/w) < 1.7), eluted with a micellar eluent of anionic SDS, propanol was too weak. A study is also shown for mixtures of sulfonamides (log P(o/w) = -1.2 to 1.7) and steroids (log P(o/w) = 3.0-8.1) eluted from conventional C18 columns with SDS mobile phases containing acetonitrile and 1-pentanol, respectively, which are compared with classical acetonitrile-water and methanol-water mixtures. The results complement a previous study on beta-blockers (log P(o/w) = -0.03 to 2.8) and reveal that MLC is a very competitive technique for the screening of compounds against conventional RPLC, due to its peculiar behaviour with regard to the selectivity and elution strength. The concentration of organic solvent needed to obtain sufficiently low retention times (even for highly hydrophobic steroids with log P(o/w) = 7-8) is also appreciably smaller for MLC, which reduces the environmental impact of the mobile phases.     

An NMR study of merocyanine-type dyes derived from barbituric acid

The 13C NMR of two solvatochromic dyes derived from a barbituric acid acceptor and dimethylaminophenyl donor fragments, compound 1 and the related merocyanine 2, were recorded in various solvents. The observed chemical-shift variations were used to interpret their structural differences and solvatochromic behavior in solution.     

Spectroscopic and electrochemical studies on (2-hydroxypicolinate)-bis(2,2′-bipyridine)ruthenium(II) and related complexes

Summary The synthesis, spectra and electrochemistry of [Ru(bipy)₂-(picOH)]⁺ and -picO-[Ru(bipy)₂]₂ ²⁺ (bipy = 2,2-bipyridine and picOH = 3-hydroxypicolinate ion) are described. The spectroscopic properties in the visible region are dominated by the intense Ru bipy chargetransfer transitions. In the binuclear complex, the two [Ru(bipy)₂L]²⁺ moieties are nonequivalent, exhibiting E _1/2 = 0.69 and 1.20 V versus s.h.e. The partially oxidized species exhibits a weak intervalence transfer band at 1085 nm, and is consistent with a Robin-Day class II mixed valence complex.     

Extraction of macro- and microamounts of lanthanides by D2EHPA

The effect of macroconcentration (Ma) lanthanide extraction on the microcomponent (Mi) extraction by D2EHPA was investigated. The investigation corroborated that the macrocomponent suppresses the microcomponent extraction. The extractability of Mi decreases with increasing Ma concentration and with increasing proton lanthanide number in macroconcentrations. Semi-empirical relations were derived describing lanthanide extraction in lanthanide macro- and microconcentrations as a function of the extraction of lanthanide macroconcentrations. Under the conditions discussed, these relations can be used to estimate for any lanthanide the distribution ratios for the lanthanide applied as a macrocomponent and for Eu applied as a microcomponent.     

Kinetic determination of tellurium based on its inhibitory effect on the palladium(II)-catalysed reaction between pyronine G and hypophosphite ion

A kinetic method for the determination of Te based on its inhibitory effect on the PdII-catalysed reaction between pyronine G and H2PO2- is described. The influence of experimental variables on the rate of the process and the potential interfering effect of a large number of ions has been studied. Under the selected experimental conditions: 6 x 10(-5) M pyronine G; 0.6 M H2PO2-; pH 2.6, adjusted with Britton-Robinson buffer; 0.80 microgram ml-1 of PdII; and a temperature of 22 +/- 0.2 degrees C, Te was determined in the concentration range 0.08-0.85 microgram ml-1. The method was applied to the determination of Te in waters and lead concentrates.     

Applications of the dicarbollylcobaltate(III) anion in the water/nitrobenzene extraction system

The fundamental properties of the polyhedral sandwich dicarbollylcobaltate(III) anion {[pi-(3)-1,2-B(9)C(2)H(11)](2)Co(III)}(-) are given, together with results for extraction of alkali-metal, alkaline-earth metal and some other cations (e.g., H(+), Pb(2+), Pd(2+) and Ce(3+)) into nitrobenzene and corresponding analytical applications. Considerable attention is paid to charge-transfer through the water-nitrobenzene interface in the presence of this hydrophobic anion.     

Hydrophobic interaction chromatography of proteins on Separon hema. I. The effect of an initial salt concentration on the separation of proteins

The influence of an initial salt concentration, phi(0), on the gradient separation of proteins using hydrophobic interaction chromatography on Separon HEMA 1000 was investigated. The results obtained were compared with the retention times and peak widths calculated according to a mathematical model.     

Thermochemical aspects of proton transfer in the gas phase

The beginning of the twentieth century saw the development of new theories of acidity and basicity, which are currently well accepted. The thermochemistry of proton transfer in the absence of solvent attracted much interest during this period, because of the fundamental importance of the process. Nevertheless, before the 1950s, few data were available, either from lattice energy evaluations or from calculations using the emerging molecular orbital theory. Advances in mass spectrometry during the last 40 years allowed studies of numerous systems with better accuracy. Thousands of accurate gas-phase acidities or basicities are now available, for simple atomic and molecular systems and for large biomolecules. The intrinsic effect of structure on the Br?nsted basic or acidic properties of molecules and the influence of solvents have been unravelled. In this tutorial, the basics of the thermodynamic principles involved are given, and the mass spectrometric techniques are briefly reviewed. Advances in the design and measurements of gas-phase superacids and superbases are described. Recent studies concerning biomolecules are also evoked.     

Synthesis,Spectral and Magnetic Properties,and Crystal Structures of Copper(II) Pyridinecarboxylate Adducts with N‐Heterocyclic Ligands

Synthesis and characterization of seven new complexes [Cu(2‐MeSnic)₂(CH₃OH)]₂ (where 2‐MeSnic is 2‐methylthionicotinate), [Cu(2‐MeSnic)₂L₂]₂ (where L is pyridine — py, ethylnicotinate — Etnic and butylnicotinate — Bunic), [Cu(2‐MeSnic)₂L₂(H₂O)₂] (where L is py and nicotinamide — nia) and [Cu(2‐MeSnic)₂(N‐Menia)₂(H₂O)₂]·2H₂O (where N‐Menia is N‐methylnicotinamide) are reported. The characterization were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic susceptibility measurements over a temperature range of 1.8 — 300 K or 70 — 300 K. Three complexes of different type were studied by X‐ray analysis. The molecule of [Cu(2‐MeSnic)₂(CH₃OH)]₂ has dimeric paddle‐wheel cage structure with a tetragonal pyramidal arrangement around Cu^II. The dimer results from the fact that carboxyl groups of four 2‐MeSnic anions function as bridging in a syn‐syn arrangement. On the other hand [Cu(2‐MeSnic)₂(py)₂]₂ forms dimers with hexacoordinated Cu^II atoms in highly distorted coordination octahedra, each with two oxygen atoms of bridging carboxyl groups in an anti‐anti arrangement of two 2‐MeSnic anions, with two oxygen atoms of one asymmetrically chelating 2‐MeSnic anion and with two nitrogen atoms of two pyridine ligands. The temperature independent EPR spectrum for this complex exhibits an axial signal which corresponds to almost isolated S = ¹/₂ magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic interaction between the two metal ions with J = —0.65 cm^—1. The Cu^II atom in complex [Cu(2‐MeSnic)₂(py)₂(H₂O)₂] is hexacoordinated in an elongated centrosymmetrical tetragonal‐bipyramidal arrangement (4 + 2). Based on the molecular structure the electronic, infrared, electron paramagnetic resonance spectra and magnetic properties are discussed and stereochemistry as well as the mode of ligand coordination in new solid complexes under study have been determined.