Synthesis and complexation properties of novel triazoyl-based ferrocenyl ligands

Two new ligand derivatives of ferrocene, namely N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbimine (L1) and N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbamide (L2), were synthesised in good yields by reacting the known compound 3,5-di-pyridine-2-yl-[1,2,4]triazol-4-ylamine (1) with ferrocenecarbaldehyde and chlorocarbonyl ferrocene, respectively. The structures of L1 and L2 were determined by X-ray crystallography. The complexation of L1 and L2 with Cu^I, Ag^I, Zn^II and Cd^II was studied by NMR and UV-vis spectroscopies, as well as by electrochemistry, with titrations used to determine metal:ligand stoichiometries. The cyclic voltammograms of L1 and L2 and their respective complexes indicated reversible one-electron transfers corresponding to the Fc^0/+ redox couple (Fc 0;= 0;ferrocene), with formal electrode potentials shifting to more positive values upon metal complexation.     

Evaluation of 1.0 mm i.d. column performances on ultra high pressure liquid chromatography instrumentation

The present study focuses on the evaluation of 1.0 0;mm i.d. (internal diameter) columns on a commercial Ultra-High Pressure system. These systems have been developed specifically to operate columns with small volumes, typically 2.1 0;mm i.d., by reducing extra-column volume dispersion. The use of columns with smaller i.d. results in a reduced solvent consumption and required sample volume. The evaluation of the columns was carried out with samples containing neutral and pharmaceutical compounds. In isocratic mode, the extra-column volume produced additional band broadening leading to poor performances compared to equivalent 2.1 0;mm i.d. columns. By increasing the length of the column, the influence of the extra-column bandspreading could be reduced and 75,000 plates were obtained when four columns were coupled. In gradient mode, the effect of the extra-column contribution on efficiency was limited and about 80% of the performance of the 2.1 0;mm i.d. columns was obtained. Optimum conditions in gradient mode were further investigated by changing flow rate, gradient time and column length. A different approach of the calculation of peak capacity was also considered for the comparison of the influence of these different parameters.     

Supercritical fluid chromatography hyphenated with twin comprehensive two-dimensional gas chromatography for ultimate analysis of middle distillates

This paper reports the conditions of online hyphenation of supercritical fluid chromatography (SFC) with twin comprehensive two-dimensional gas chromatography (twin-GC 0;× 0;GC) for detailed characterization of middle distillates; this is essential for a better understanding of reactions involved in refining processes. In this configuration, saturated and unsaturated compounds that have been fractionated by SFC are transferred on two different GC 0;× 0;GC columns sets (twin-GC 0;× 0;GC) placed in the same GC oven. Cryogenic focusing is used for transfer of fractions into the first dimension columns before simultaneous GC 0;× 0;GC analysis of both saturated and unsaturated fractions. The benefits of SFC–twin-GC 0;× 0;GC are demonstrated for the extended alkane, iso-alkane, alkene, naphthenes and aromatics analysis (so-called PIONA analysis) of diesel samples which can be achieved in one single injection. For that purpose, saturated and unsaturated compounds have been separated by SFC using a silver loaded silica column prior to GC 0;× 0;GC analysis. Alkenes and naphthenes are quantitatively recovered in the unsaturated and saturated fractions, respectively, allowing their identification in various diesel samples. Thus, resolution between each class of compounds is significantly improved compared to a single GC 0;× 0;GC run, and for the first time, an extended PIONA analysis of diesel samples is presented.     

Convex hull: A new method to determine the separation space used and to optimize operating conditions for comprehensive two-dimensional gas chromatography

It is important to develop methods of optimizing the selection of column sets and operating conditions for comprehensive two-dimensional gas chromatography. A new method for the calculation of the percentage of separation space used was developed using Delaunay's triangulation algorithms (convex hull). This approach was compared with an existing method and showed better precision and accuracy. It was successfully applied to the selection of the most convenient column set and the geometrical parameters of second column for the analysis of 49 target compounds in wastewater.     

Quantitative assessment of moisture damage for cacao bean quality using two-dimensional gas chromatography combined with time-of-flight mass spectrometry and chemometrics

Quality control of cacao beans is a significant issue in the chocolate industry. In this report, we describe how moisture damage to cacao beans alters the volatile chemical signature of the beans in a way that can be tracked quantitatively over time. The chemical signature of the beans is monitored via sampling the headspace of the vapor above a given bean sample. Headspace vapor sampled with solid-phase micro-extraction (SPME) was detected and analyzed with comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC 0;× 0;GC–TOFMS). Cacao beans from six geographical origins (Costa Rica, Ghana, Ivory Coast, Venezuela, Ecuador, and Panama) were analyzed. Twenty-nine analytes that change in concentration levels via the time-dependent moisture damage process were measured using chemometric software. Biomarker analytes that were independent of geographical origin were found. Furthermore, prediction algorithms were used to demonstrate that moisture damage could be verified before there were visible signs of mold by analyzing subsets of the 29 analytes. Thus, a quantitative approach to quality screening related to the identification of moisture damage in the absence of visible mold is presented.     

Energy law preserving C finite element schemes for phase field models in two-phase flow computations

We use the idea in [33] to develop the energy law preserving method and compute the diffusive interface (phase-field) models of Allen–Cahn and Cahn–Hilliard type, respectively, governing the motion of two-phase incompressible flows. We discretize these two models using a C⁰ finite element in space and a modified midpoint scheme in time. To increase the stability in the pressure variable we treat the divergence free condition by a penalty formulation, under which the discrete energy law can still be derived for these diffusive interface models. Through an example we demonstrate that the energy law preserving method is beneficial for computing these multi-phase flow models. We also demonstrate that when applying the energy law preserving method to the model of Cahn–Hilliard type, un-physical interfacial oscillations may occur. We examine the source of such oscillations and a remedy is presented to eliminate the oscillations. A few two-phase incompressible flow examples are computed to show the good performance of our method.     

The microwave spectrum of methyl chlorodifluoroacetate: Methyl internal rotation and chlorine nuclear electric quadrupole coupling

A chirped pulse microwave spectrometer has been used to record microwave spectra of the ³⁵Cl and ³⁷Cl isotopologues of methyl chlorodifluoroacetate, CClF₂C(0" alt="double bond; length as m-dash" src="http://cdn.els-cdn.com/sd/entities/dbnd" class="glyphImg">O)OCH₃, between 8 0;GHz and 16 0;GHz. The target compound was spectroscopically examined as it participated in a supersonic expansion of argon. Only one conformer was observed. The rotational spectra were recorded with sufficient resolution to observe (i) splittings due to the internal rotation of the methyl group, and (ii) splittings from the coupling of the chlorine quadrupolar nucleus. A total of 785 transitions have had quantum numbers assigned. Analysis of the spectra observed has produced an experimental barrier to the methyl group internal rotation, V₃, of 370(2) 0;cm⁻¹. It is noted that this barrier is a little lower than that determined for methyl acetate [V₃ 0;= 0;425 0;cm⁻¹, J. Sheridan, W. Bossert and A. Bauder, J. Mol. Spectrosc., 80 (1980) 1-11], and this is rationalized through a comparison of molecular structures. Lastly, all components of both the ³⁵Cl and ³⁷Cl chlorine nuclear electric quadrupolar coupling tensor have been determined.     

Growth and characterization of Nd:Lu3ScxGa5 − xO12 series laser crystals

A new series Nd:Lu₃Sc_xGa_{5 0;− 0;x}O₁₂ (x 0;= 0;0.5, 0.8, 1, 1.2 and 1.5) laser crystals have been successfully grown by the optical floating zone method. Their absorption and luminescence spectra were measured at room temperature and spectral parameters were systemically calculated using Judd-Ofelt (JO) theory. The fluorescence τ_f lifetimes were experimentally measured and compared with the theoretical results. Diode-pumped continuous-wave (CW) laser performance at 1.06 0;μm with mixed crystals was demonstrated. The influence of different x values on laser performance and spectral parameters was also discussed. All the results show that Nd:Lu₃Sc_xGa_{5 0;− 0;x}O₁₂ series crystals should be suitable for laser application.     

Multi-wavelength operation of LD side-pumped Nd:YAG laser

A dual-wavelength laser at 1064 0;nm and 1319 0;nm is obtained by a single Nd:YAG crystal rod. On the basis of 1064 0;nm and 1319 0;nm dual-wavelength laser installation, the second harmonic waves at 532 0;nm and 660 0;nm can be achieved by using non-linear frequency conversion technology. When 1064 0;nm and 1319 0;nm lasers oscillate simultaneously, the maximum output power is 30.5 0;W and 8.78 0;W, respectively. When the 1319 0;nm laser is restrained, we obtain a 35.6 0;W maximum output power at 1064 0;nm and by contrary 11.2 0;W at 1319 0;nm. The maximum output powers of 532 0;nm and 660 0;nm lasers are 5.34 0;W and 1.353 0;W when oscillating simultaneously. With one of them restrained, the maximum output power is 6.72 0;W at 532 0;nm and 1.90 0;W at 660 0;nm. The optimum repetition rate of the acousto-optic Q-switch is 10.5 0;KHz and 20.5 0;KHz for 532 0;nm and 660 0;nm lasers, respectively. The optical-to-optical conversion efficiency from the fundamental waves to the harmonic waves is 17.5% and 15.4%. The instability is less than 2%.     

~ 1.2 μm near-infrared emission and gain anticipation in Ho doped heavy-metal gallate glasses

Ho³⁺-doped low-phonon-energy heavy-metal gallate glasses (LKBPBG) have been prepared and efficient 1.199 0;μm emission originating from the ⁵I₆ 0;→ 0;⁵I₈ radiative transition has been observed under 900 0;nm excitation. The spontaneous emission probability and the maximum stimulated emission cross-section were derived to be 294.31 0;s^{− 0;1} and 3.46 0;× 0;10^{− 0;21} 0;cm², respectively. The ratio of quantum yields between ~ 0;1.2 and ~ 0;2.0 0;μm emissions was identified to be 16%, demonstrating that the ⁵I₆ 0;→ 0;⁵I₈ transition is favorable for optical amplification. The maximum gain coefficient of 1.84 0;dB/cm at 1.199 0;μm wavelength was anticipated in the ideal status. These results indicate that the Ho³⁺-doped LKBPBG glasses have a promising potential for the development of ~ 0;1.2 0;μm signal amplifier devices.