Synthesis,Structure and Light‐Harvesting Properties of Some New Transition‐Metal Dithiocarbamates Involving Ferrocene

Nine new transition‐metal dithiocarbamates involving ferrocene (Fc), namely, [M(FcCH₂Bzdtc)₂] (M=Ni^II ( 1 ), Cu^II ( 2 ), Cd^II ( 3 ), Hg^II ( 4 ), Pd^II ( 5 ), Pt^II ( 6 ) and Pb^II ( 7 ); Bzdtc=N‐benzyl dithiocarbamate) and [M(FcCH₂Bzdtc)₃] (M=Co^II ( 8 ) and UO₂^VI ( 9 )), have been synthesised and characterised by micro analyses, IR spectroscopy, ¹H and ¹³C NMR spectroscopy, and in three cases by single‐crystal X‐ray analysis. The peak broadening in the ¹H spectrum of the copper complex indicates the paramagnetic behaviour of this compound. A square‐planar geometry around the nickel and copper complexes and distorted linear geometry around the mercury complex have been found. The latter geometry is attributed to the bulkiness of the methylferrocenyl and benzyl groups. The observed single quasi‐reversible cyclic voltammograms for complexes 2 , 8 and 9 indicate the stabilisation of a metal centre other than Fe in their characteristic oxidation state. These complexes have been used as a photosensitiser in dye‐sensitised solar cells.     

Strategies for the synthesis of fluorinated liquid crystal derivatives from perbromofluoroaromatic systems

The use of perbromofluorobenzene derivatives as starting materials for the synthesis of a variety of model liquid crystal systems by a combination of nucleophilic aromatic substitution, debromolithiation/trapping, dehydration and reduction processes is described.     

Tandem catalysis in ionic liquids: a recyclable catalytic synthesis of benzofuran derivatives

A convenient, recyclable catalytic synthesis of benzofuran-2-acetic esters 2 by sequential Pd(0)-catalyzed deallylation—Pd(II)-catalyzed carbonylative heterocyclization of 1-(2-allyloxyphenyl)-2-yn-1-ols 1 in ionic liquids is presented. Reactions were typically carried out in BmimBF₄ as the solvent at 100 °C and under 30 atm of CO, in the presence of catalytic amounts (1 mol %) of PdI₂ in conjunction with KI (1 equiv), PPh₃ (4 mol %), MeOH (28 equiv), and H₂O (2 equiv). The solvent-catalyst system could be recycled several times without appreciable loss of catalytic activity.     

The distribution of dissolved thallium in the different water masses of the western sector of the Ross Sea (Antarctica) during the austral summer

Vertical profiles for total dissolved thallium were obtained at five sites in the western sector of the Ross Sea (Southern Ocean), Antarctica. Thallium is estimated to have a natural mean seawater concentration between 50 and 65 pmol L^{− 1} with higher values in the North Pacific (65 ± 5 pmol L^{− 1}) and lower in the Bay of Biscay and Irish Sea (49 ± 3 pmol L^{− 1}). Our samples show a concentration varying from 22 to 55 pmol L^{− 1} with a mean value of 46 pmol L^{− 1}, depending on depth, dissolved oxygen, salinity and local topographic characteristics. The analyses were performed using an ICP-SFMS that has enabled us to obtain reliable Tl concentration measurements with a relative standard deviation of better than 2.5% and a detection limit, calculated as three times the standard deviation of the “blank signal” of 0.69 pmol L^{− 1} (1.60 pmol L^{− 1}, obtained analysing four blank solutions (n = 5) prepared with the same water and acid used for the dilution/acidification steps). Thallium appears to have a nearly conservative distribution in seawater as highlighted also from the comparison with the profiles of two seawater conservative elements: molybdenum and uranium; however it also highlights the presence of a reactive component of thallium, which is more influenced by the presence of particulate matter, oxygen content and fluorescence.     

Experimental assessment of a large sample cell for laser ablation-ICP-MS, and its application to sediment core micro-analysis

The coupling of laser ablation (LA) to inductively coupled plasma-mass spectrometry (ICP-MS) enables the direct analysis of solid samples with micrometric resolution. Analysis is often restricted to relatively small samples owing to the dimensions of conventional ablation cells. Here, we assess the performance of a large rectangular, commercially-available sample cell which enables analysis over a 10.2?×?5.2 cm² area. Comparison with the conventional cell shows a small to moderate performance decrease for the large cell resulting from the dilution of ablated particles in a larger volume with a 4–31% lower signal output and longer signal tailings. The performance of this cell is however sufficient for the determination of both major and trace elements in many kinds of samples. The applicability of the large cell LA-ICP-MS setup was demonstrated by the determination of Al, Si, Mn, Fe, Cu, Zn Pb and U in sediment core sections at a resolution of 0.6 mm. Detection limits for sediment analysis were 7 mg Al kg^?1, 68 mg Si kg^?1, 0.5 mg Mn kg^?1, 20 mg Fe kg^?1, 0.2 mg Cu kg^?1, 0.3 mg Zn kg^?1, 0.08 mg Pb kg^?1 and 0.003 mg U kg^?1. Cyclic patterns, which would have been overlooked by conventional analysis at cm resolution, were observed in analysed sediments. This study demonstrates the potential of LA-ICP-MS in environmental analysis, with the large sample cell setup offering the possibility to analyse a wider range of samples without sectioning.     

Advanced surface functionalization of periodic mesoporous silica: Kinetic control by trisilazane reagents

The surface reactions of mesoporous silica MCM-41 with a series of new trisilylamines (trisilazanes) (SiHMe2)2NSiMe2R and (SiMe2Vin)2NSiMe2R (R = indenyl, norpinanyl, chloropropyl, 3-(N-morpholin)propyl; Vin = vinyl), disilylalkylamine (SiHMe2)iPrNSiMe2(CH2)3Cl, and monosilyldialkylamines Me2NSiMe2R (R = indenyl, chloropropyl, 3-(N-morpholin)propyl) were investigated. 1H, 13C, and 29Si MAS NMR spectroscopy, nitrogen adsorption/desorption, infrared spectroscopy, and model reactions with calix[4]arene as a mimic for an oxo surface were used to clarify the chemical nature of surface-bonded silyl groups. The trisilylamines exhibited a comparatively slow surface reaction, which allowed for the adjustment of the amount of silylated and nonreacted SiOH groups and led to a stoichiometric distribution of surface functionalities. The 2:1 integral ratio of SiHMe2 and SiMe2R moieties of such trisilazanes was found to be preserved on the silica surface as indicated by microanalytical as well as 13C and 29Si MAS NMR spectroscopic data of the hybrid materials. For example, the reaction of MCM-41 with (SiHMe2)2NSiMe2(CH2)3Cl, (SiHMe2)iPrNSiMe2(CH2)3Cl, and Me2NSiMe2(CH2)3Cl provided bi- and monofunctional hybrid materials with one-third, one-half, or all chemically accessible silanol groups derivatized by chloropropyl groups, respectively. Thus, a molecular precursor strategy was developed to efficiently control the relative amount of three different surface species, SiHMe2 (or SiVinMe2), SiMe2R, and SiOH, in a single reaction step. The reaction behavior of indenyl-substituted monosilazanes and trisilazanes (R = Ind) with calix[4]arene proved that the indenyl substituent can act as a leaving group forming a dimethylsilyl species, which is anchored bipodally on the silica surface, that is, via two Si-O bonds.     

Syntheses and structures of magnesium and zinc boraamidinates: EPR and DFT investigations of Li, Mg, Zn, B, and In complexes of the [PhB(NtBu)2].- anion radical

The first magnesium and zinc boraamidinate (bam) complexes have been synthesized via metathetical reactions between dilithio bams and Grignard reagents or MCl2 (M = Mg, Zn). The following new classes of bam complexes have been structurally characterized: heterobimetallic spirocycles {(L)mu-Li[PhB(mu-NtBu)2]}2M (6a,b, M = Mg, L = Et2O, THF; 6c, M = Zn, L = Et(2)O); bis(organomagnesium) complexes {[PhB(mu3-NtBu)2](MgtBu)2(mu3-Cl)Li(OEt2)3} (8) and {[PhB(mu3-NtBu)2](MgR)2(THF)2} (9a, R = iPr; 9b, R = Ph); mononuclear complex {[PhB(mu-NDipp)2]Mg(OEt2)2} (10). Oxidation of 6a or 6c with iodine produces persistent pink (16a, M = Mg) or purple (16b, M = Zn) neutral radicals {Lx-mu-Li[PhB(mu-NtBu)2]2M}. (L = solvent molecule), which are shown by EPR spectra supported by DFT calculations to be Cs-symmetric species with spin density localized on one of the bam ligands. In contrast, characterization of the intensely colored neutral radicals {[PhB(mu-NtBu)2]2M}. (5c, M = In, dark green; 5d, M = B, dark purple) reveals that the spin density is equally delocalized over all four nitrogen atoms in these D2d-symmetric spirocyclic systems. Oxidation of the dimeric dilithio complex {Li2[PhB(mu4-NtBu)2]}2 with iodine produces the monomeric neutral radical {[PhB(mu-NtBu)2]Li(OEt2)x}. (17), characterized by EPR spectra and DFT calculations. These findings establish that the bam anionic radical [PhB(NtBu)2].- can be stabilized by coordination to a variety of early main-group metal centers to give neutral radicals whose relative stabilities are compared and discussed.     

Rotational spectra of 1-chloro-2-fluoroethylene. I. Main isotopologues and deuterated species of the trans isomer

Guided by theoretical predictions, the rotational spectra of the mono- and bideuterated species of trans-1-chloro-2-fluoroethylene, CH35Cl=CDF, CH37Cl=CDF, CD35Cl=CHF, CD37Cl=CHF, CD35Cl=CDF, and CD37Cl=CDF, have been recorded for the first time. Assignment of the Delta J = 0 and Delta K(-1) = +1 bands with K(-1) = 3,4,5,... (all isotopic species) as well as of several Delta J = +/-1 and Delta K(-1) = +1 transitions (all isotopic species except CH37Cl=CDF, CD37Cl=CHF, and CD37Cl=CDF) led to the accurate determination of the ground-state rotational constants, the quartic, and some sextic centrifugal distortion constants, as well as the nuclear quadrupole coupling constants for both 35Cl and 37Cl in good agreement with corresponding theoretical predictions based on high-level coupled-cluster calculations. Inconsistencies of the present spectroscopic parameters with respect to those reported earlier for the two main isotopologues, i.e., CH35Cl=CHF and CH37Cl=CHF, necessitated a reinvestigation of the rotational spectra for these two isotopic species. Supported by quantum chemical calculations, the previously recorded spectra are reassigned to a vibrationally excited state, while analysis of the Delta J = 0 and Delta K(-1) = +1 as well as some Delta J = +/-1 and Delta K(-1) = +1 transitions provided a revised set of spectroscopic parameters for the vibrational ground state of these two isotopic species.