Infrared evidence for the transmission of electronic effects through a metal atom in a series of new cadmium complexes

A series of novel cadmium complexes has been synthesized from the reaction of cadmium chloride, bromide and iodide with primary aromatic amines. The complexes are either mononuclear or polynuclear according to the nature of the halide and amine employed. A possible mechanism for their formation is proposed. The N - H stretching and bending frequencies are linearly related to the electronegativity of the co-ordinated halogen, indicating that the electron withdrawing capacity of the halogen is transmitted through the cadmium atom

Synthesis, electrochemical and spectroscopic properties of molybdenum complexes bearing 5-alkoxy-thiophenic or- bithiophenic groups

Trans-[FMo{NN=CH(5´-R-thienyl)}(dppe)2][BF4] (R = OMe and OEt) and trans[FMo{NN=CH(5’-R-2,2’-bithienyl)}(dppe)2][BF4] (R = OMe, OEt and O(iPr)) were synthesised in good yields by reacting 2-formyl-5-alkoxylthiophenes and 5-formyl-5’-alkoxy-2,2-’bithiophenes respectively, with hydrazido(2-) complex, trans-[MoF(NNH2)(dppe)2][BF4]. The electrochemical, spectroscopic and solvatochromic properties of these compounds were studied. These results suggest that efficient π conjugated systems were obtained due to the low energy charge transfer between the metal and the heterocyclic moieties.Fundação para a Ciência e a Tecnologia (FCT

Integrated ‘omics’ characterization of conserved nectar production mechanisms using floral and extrafloral eudicot nectaries

Floral and extrafloral nectar, produced by nectaries, is offered as a reward to foster plant-animal mutualisms with pollinators and invertebrate predators. Attraction of pollinators through floral nectar improves fruit set in 87 out of 115 global food crops. Meanwhile extrafloral nectar, reported in 745 genera, attracts invertebrate predators, such as ants, as an indirect defense mechanism to reduce herbivory. Nectar quality (i.e. volume and composition) strongly correlates with the efficiency of these plant-animal mutualistic interactions, yet nectar composition has typically only been defined by targeted analyses of the two most predominant classes of metabolites, carbohydrates and amino acids. Other less abundant components of nectar are often unaccounted (i.e. vitamins, alkaloids, phenolics, terpenoids, lipids, metal ions, hormones, and proteins). Furthermore, molecular understanding of nectar synthesis and secretion is limited to a few reports of genes directly affecting the de novo production or quality of floral nectar. Comprehensive GC-MS based metabolomics techniques capable of quantifying trace components of nectar were used to characterize nectar composition from species, spanning three eudicot families (Cucurbitaceae, Malvaceae, and Solanaceae). This enabled examination of relationships between nectar composition and biological factors such as the sex of the flower, plant-animal mutualisms, and functional role of the nectar regarding plant reproductive success and defense (i.e. floral and extrafloral nectar). These analyses contributed the metabolomics portion of a comprehensive systems network-based project to define the conserved molecular mechanisms of nectar synthesis and secretion among floral and extrafloral nectaries of the core eudicots. Through the analysis of the transcriptomes and proteomes of nectaries from a broad range of phylogenetic plant clades, we identified core sets of genes conserved within eudicots required for nectary synthesis and secretion. These results also supply a foundation for targeted studies of nectar quality improvement, which will benefit pollinator health, promote plant reproductive success, and enhances biological control of crop pests

Molybdenum complexes bearing thiophenic or- arylthiophenic groups : synthesis, electrochemical, spectroscopic and nonlinear optical properties

A series of complexes trans-[FMo(N=NCHL)(dppe)2][BF4] (L = (bi)thienyl or arylthienyl), were synthesized and fully characterized by 1H, 13C, 31P NMR, IR and UV–Vis spectroscopies. The electronic spectra and electrochemical behavior of the complexes were investigated. The electronic absorption spectra of these complexes display a broad low-energy band in the visible region attributable to metal-to ligand charge transfer (MLCT) transitions. The electron conjugated effect with the heterocyclic nucleus led to a notable improvement of visible light absorption and marked changes in the electrochemical behavior. The hyperpolarizabilities beta of the synthesized compounds were evaluated using the hyper-Rayleigh scattering technique.Fundação para a Ciência e a Tecnologia (FCT

Regional Differences in Fan Preferences for Minor League Hockey: The AHL

Regional differences in fan preferences for minor league hockey in the United States are explored using simple linear regression models. The top-level minor league for the NHL, the American Hockey League (AHL), was studied for the 2008-09 season. Key attributes with respect to attendance are studied for hockey including population, income per capita, promotions, scoring, and winning percentage. In addition, a key socio-economic variable, fighting is also investigated. Major differences are found for fan preferences across geographic regions in relation to population, income per capita, a variety of promotions, and team success. In addition, fan reaction to fighting tends to differ greatly by region, with it having a positive effect in the Mid-Atlantic (East Division) and Western (West Division) regions, but having a negative and significant effect in the New England-area (Atlantic division). An attendance model for the top minor hockey league in North America, the American Hockey League (AHL), is specified and a variety of factors which may influence fan attendance are studied. Game-by-game attendance figures were gathered from the AHL website, www.theahl.com, along with the day of the game, team records, team scoring, and per-game fight data. Demographic data were gathered for the cities which host AHL franchises and, in addition, promotional data from individual team websites and pocket calendars were collected and converted into dummy variables representing different types of promotions. Upon gathering the data, it became apparent that substantial regional differences appeared to exist in fan preferences for certain attributes. Therefore, regressions for the overall league and for each individual division, to account for regional differences, were run and the results are presented. A focus is placed on a variety of factors to attempt to determine what influences fan decisions to attend AHL hockey games. One key variable examined is the role of fighting, which has been explored in the NHL before in Jones, Stewart, and Sunderman (1996) and Paul (2003). In these papers, fighting was shown to have a positive and significant effect on attendance. The importance of winning, which may or may not be as important at a minor-league level as compared to a major-league level, was also studied on a game-by-game basis throughout the season. A proxy for in-game excitement, scoring in these games, was also tested. Promotions were also studied which include events, merchandise giveaways, reduced food and beverage prices, group nights, etc. These data were used to determine how much of an impact, if any, these promotions have on attendance. Upon gathering and studying the data, it became apparent that there are some key regional differences in fan preferences for AHL games. To illustrate this, the regression model for the AHL as a whole is also run for each of the four divisions. The four divisions consist of the Eastern Division (Mid- Atlantic Region), Atlantic Division (New England), North Division (Canada, Western NY, Ohio), and West Division (Midwest US – both Northern and Southern). A full listing of the team cities and their division is given in Appendix I at the conclusion of this paper. These regional distinctions illustrate where certain performance-based variables and demographic variables differ for AHL Fans in relation to attendance. The paper proceeds as follows. A simple game-by-game attendance model for the AHL is set up and the dependent and independent variables are explained. The regression results are presented and explained in the context of their relationship with per-game attendance. Regional differences are then explored by division. Discussion of the results and conclusions occur in the final section

Versatile Coordination of Cyclopentadienyl-Arene Ligands and Its Role in Titanium-Catalyzed Ethylene Trimerization

Cationic titanium(IV) complexes with ansa-(η5-cyclopentadienyl,η6-arene) ligands were synthesized and characterized by X-ray crystallography. The strength of the metal-arene interaction in these systems was studied by variable-temperature NMR spectroscopy. Complexes with a C1 bridge between the cyclopentadienyl and arene moieties feature hemilabile coordination behavior of the ligand and consequently are active ethylene trimerization catalysts. Reaction of the titanium(IV) dimethyl cations with CO results in conversion to the analogous cationic titanium(II) dicarbonyl species. Metal-to-ligand backdonation in these formally low-valent complexes gives rise to a strongly bonded, partially reduced arene moiety. In contrast to the η6-arene coordination mode observed for titanium, the more electron-rich vanadium(V) cations [cyclopentadienyl-arene]V(NiPr2)(NC6H4-4-Me)+ feature η1-arene binding, as determined by a crystallographic study. The three different metal-arene coordination modes that we experimentally observed model intermediates in the cycle for titanium-catalyzed ethylene trimerization. The nature of the metal-arene interaction in these systems was studied by DFT calculations.

Estimation of anthropogenic organo-chlorine, bromine and iodine compounds in apolar lipid fractions of bovine milk by solid-phase extraction and neutron activation analysis (SPE–NAA)

Articulo cientifico publicado en: Journal of Radioanalytical and Nuclear Chemistry (2018) 318:247–257 https://doi.org/10.1007/s10967-018-6086-8Milk lipids were separated using a hexane:isopropanol mixture; then they were fractionated into apolar, medium polar and polar portions by SPE using a LC-Si column. The apolar fraction was further separated into 4 more portions depending on their polarity by another SPE method using a Florosil column. Levels of Cl, Br and I were measured by NAA. Halogens were detected in all separated fractions; but their highest levels were found in the most apolar fraction containing hydrocarbons which strongly indicates the presence of anthropogenic organohalogen compounds in milk. In addition, iodide and iodate ions in whole milk samples were measured

A Broadly Applicable Strategy for Entry into Homogeneous Nickel(0) Catalysts from Air-Stable Nickel(II) Complexes

A series of air-stable nickel complexes of the form L[subscript 2]Ni(aryl) X (L = monodentate phosphine, X = Cl, Br) and LNi(aryl)X (L = bis-phosphine) have been synthesized and are presented as a library of precatalysts suitable for a wide variety of nickel-catalyzed transformations. These complexes are easily synthesized from low-cost NiCl[subscript 2]·6H[subscript 2]O or NiBr[subscript 2]·3H[subscript 2]O and the desired ligand followed by addition of 1 equiv of Grignard reagent. A selection of these complexes were characterized by single-crystal X-ray diffraction, and an analysis of their structural features is provided. A case study of their use as precatalysts for the nickel-catalyzed carbonyl-ene reaction is presented, showing superior reactivity in comparison to reactions using Ni(cod)[subscript 2]. Furthermore, as the precatalysts are all stable to air, no glovebox or inert-atmosphere techniques are required to make use of these complexes for nickel-catalyzed reactions.National Institute of General Medical Sciences (U.S.) (GM63755)National Science Foundation (U.S.). Graduate Research Fellowshi