1,2,4-triazine derived binuclear lead(ii) complexes: synthesis, spectroscopic and structural investigations and application in organic light-emitting diodes (OLEDs).

Two novel binuclear complexes of Pb(ii) were synthesized by reacting a 3-(2-pyridyl)-5-(4-methoxyphenyl)-1,2,4-triazine (PMPT) ligand with different anionic co-ligands (1: bromide, 2: acetate and isothiocyanate) in a 1 : 1 molar ratio of PMPT ligands to lead(ii) salts. The complexes, [Pb2(µ-PMPT)2Br4] (1) and [Pb2(µ-PMPT)2((µ-CH3COO)2(NCS)2] (2), were characterized using various physicochemical techniques such as CHN analysis, FT-IR spectroscopy, and 1H NMR spectroscopy. Additionally, their structures were determined using single-crystal X-ray diffraction. Based on the obtained structural parameters, complex 1 exhibited a PbN3Br2 environment, while complex 2 displayed a PbN4O3 environment, with holodirected and hemidirected coordination spheres, respectively. Within the crystal network of the complexes, there were interactions involving C-H⋯X (X: O, S, N) as well as π-π stacking. The Pb(ii) complexes were further investigated for their potential use as the emitting layer in organic light-emitting devices (OLEDs). The current-voltage and luminescence-voltage characteristics, as well as the electroluminescence (EL) properties of the complexes, were studied.

Using Coordination Chemistry to Control "Click" Reactions: The Selective Formation of Asymmetrically Ligated Polyoxometalates.

The Cu(I)-catalyzed azide-alkyne cycloaddition reaction between (NBu4)2[V6O13((OCH2)3CCH2N3)2] and 3-ethynylpyridine led to the formation of products capable of forming poorly soluble coordination compounds with transition metal ions such as Cu(I) and Zn(II). The formation of these poorly soluble phases is an important feature that was used to determine the course of reactions, allowing the selective preparation of symmetric bis-pyridyltriazolyl and asymmetric monopyridyltriazolyl derivatives with relatively high yields and high substrate conversions. The asymmetric compound (NBu4)2[V6O13((OCH2)3CCH2-N3C2H-C5H4N)((OCH2)3CCH2N3)] (V6asym) was utilized in the subsequent "click" postfunctionalization reaction with 1,4-diethynylbenzene, resulting in a covalently bound V6asym-V6asym dimer. This dimeric compound was subjected to scanning probe microscopy studies on gold surfaces, which revealed no electronic coupling between the hexavanadate cores within the dimer upon potential-induced switching. This observation indicates that such dimers and higher-order oligomers composed of polyoxometalate-ligand-polyoxometalate bridges can be exploited as active capacitor/memristor units, relevant to increase the data storage capacity of standard memory devices with innovative molecular switching mechanisms.

Exploring Defect-Engineered Metal-Organic Frameworks with 1,2,4-Triazolyl Isophthalate and Benzoate Linkers.

Synthesis and characterization of DEMOFs (defect-engineered metal-organic frameworks) with coordinatively unsaturated sites (CUSs) for gas adsorption, catalysis, and separation are reported. We use the mixed-linker approach to introduce defects in Cu2-paddle wheel units of MOFs [Cu2(Me-trz-ia)2] by replacing up to 7% of the 3-methyl-triazolyl isophthalate linker (1L2-) with the "defective linker" 3-methyl-triazolyl m-benzoate (2L-), causing uncoordinated equatorial sites. PXRD of DEMOFs shows broadened reflections; IR and Raman analysis demonstrates only marginal changes as compared to the regular MOF (ReMOF, without a defective linker). The concentration of the integrated defective linker in DEMOFs is determined by 1H NMR and HPLC, while PXRD patterns reveal that DEMOFs maintain phase purity and crystallinity. Combined XPS (X-ray photoelectron spectroscopy) and cw EPR (continuous wave electron paramagnetic resonance) spectroscopy analyses provide insights into the local structure of defective sites and charge balance, suggesting the presence of two types of defects. Notably, an increase in CuI concentration is observed with incorporation of defective linkers, correlating with the elevated isosteric heat of adsorption (ΔHads). Overall, this approach offers valuable insights into the creation and evolution of CUSs within MOFs through the integration of defective linkers.

Control of Intermediates and Products by Combining Droplet Reactions and Ion Soft-Landing.

Despite being recognized primarily as an analytical technique, mass spectrometry also has a large potential as a synthetic tool, enabling access to advanced synthetic routes by reactions in charged microdroplets or ionic thin layers. Such reactions are special and proceed primarily at surfaces of droplets and thin layers. Partial solvation of the reactants is usually considered to play an important role for reducing the activation barrier, but many mechanistic details still need to be clarified. In our study, we showcase the synergy between two sequentially applied "preparative mass spectrometry" methods: initiating accelerated reactions within microdroplets during electrospray ionization to generate gaseous ionic intermediates in high abundance, which are subsequently mass-selected and soft-landed to react with a provided reagent on a substrate. This allows the generation of products at a nanomolar scale, amenable to further characterization. In this proof-of-concept study, the contrasting reaction pathways between intrinsically neutral and pre-charged reagents, respectively, both in microdroplets and in layers generated by ion soft-landing are investigated. This provides new insights into the role of partially solvated reagents at microdroplet surfaces for increased reaction rates. Additionally, further insights into reactions of ions of the same polarity under various conditions is obtained.

A stable lanthanum hydroxamate metal-organic framework with radical character and electrical conductivity.

Metal-organic frameworks with hydroxamate linkers are an emerging new class of stable porous crystalline materials. Due to the difficulty in controlling reversible formation of strong metal-hydroxamate bonds and the limitation of available hydroxamate ligands, hydroxamate MOFs are rarely reported and their applications are underexplored. Herein, we report on a lanthanum MOF, La-ONDI, containing the redox-active hydroxamate ligand ONDI2-. Due to the presence of strong coordinative bonds of chelating hydroxamate groups to metal nodes, La-ONDI not only displays high framework stability in aqueous solutions ranging from pH 3 to pH 13, but also exhibits good structural integrity in common organic solvents and harsh reagents. In addition, La-ONDI shows paramagnetic behaviour due to the presence of unpaired electrons. The amount of unpaired electrons can be modified by the reducing environment during synthesis. Although without π-π interactions between neighbouring ligands, La-ONDI still exhibits good electrically conductive performance with the conductivity reaching 10-6 S cm-1.

Dataset for trailer angle estimation using radar point clouds.

The automotive industry is interested in the estimation of vehicle trailer rotation (trailer angle or hitch angle) due to its use in trailer control algorithms. We present an experimental dataset collected in a study of the estimation problem [1] and a MATLAB code implementation of the study. The data collection apparatus is a truck mock-up that is attached to a flatbed trailer at the hitch ball. Two radars are installed in the taillight fixtures of the truck and a camera is installed in the truck's tailgate like a typical backup camera installation. A rotary motion sensor is also installed at the hitch ball to provide ground truth measurement of the trailer angle. To aid analysis of the dataset, both radar detections are transformed onto a vehicle coordinate system (VCS) having its origin at the hitch ball i.e. the different radar viewpoints are combined into one with respect to the hitch ball. The MATLAB code presented with this article has two major functionalities. The first functionality is the visualization of both radar detections, the combined radar detections in the VCS, the camera images, and the ground truth angles, as the trailer rotates. The second functionality of the code is the replication of the estimation results in [1], which used only the radar detections from the dataset.

Ethereal Hydroperoxides: Powerful Reagents for S-Oxygenation of Bridging Thiophenolate Functions.

S-Oxygenation of thiophenolate bridges by ethereal hydroperoxides was studied. [NiII2LS(PhCO2)]+ (1), where LS = macrocyclic aminethiolate supporting ligand, is S-oxygenated readily in a mixed methanol/acetonitrile solution with ether/dioxygen at room temperature in the presence of daylight. The reactions were found to depend strongly on the choice of the ether. Uptake of two O atoms occurs in dioxane to give a mixed thiolate/sulfinate complex [NiII2LSO2(PhCO2)]+ (2) containing the rare five-membered Ni(µ1,1-S)(µ1,2-OS)Ni core. In tetrahydrofuran, four O atoms are taken up by 1 to generate the bis(sulfinate) species [NiII2LSO4(PhCO2)]+ (3). A mono-S-oxygenated sulfenate intermediate can be detected by electrospray ionization mass spectrometry. The oxygenation reactions proceed in high yields without complex disintegration and invariably provide µ1,2-bridging sulfinates as established by spectroscopy (IR and UV/vis), X-ray crystallography, and accompanying density functional theory calculations. The oxygenation of the S atoms has a strong impact on the electronic structures of the nickel complexes. The monosulfinate complex 2 has an S = 2 ground state resulting from moderate ferromagnetic exchange coupling interactions (J = +15.7 cm-1; H = -2JS1S2), while an antiferromagnetic exchange interaction in 3 shows the presence of a ground state with spin S = 0 (J = -0.56 cm-1).

Bis(2-pyridyl) and Tris(2-pyridyl) Compounds of Gallium and Indium via a Redox-Transmetalation Route.

Reactions of the tris(2-pyridyl)lead(II) compound [LiPb(2-py6OtBu)3] (1) with trialkyl compounds of the group 13 elements gallium and indium resulted in the bis(2-pyridyl) and tris(2-pyridyl) gallate complexes [LiGaEt2(2-py6OtBu)2]2 (2), [LiGaR2(2-py6OtBu)2(THF)] (R = iPr (3), tBu (4)), [LiGatBu2(2-py6OtBu)2]2 (4'), and [LiGaMe(2-py6OtBu)3] (6), as well as corresponding indium complexes of general composition [LiInR(2-py6OtBu)3] (R = Me (7), Et (8)). The formation of these compounds can be assumed as a rapid degradation of initially formed Pb-M adducts (M = Ga or In) as found for [tBu3Ga{Pb(2-py6OtBu)3Li}] (5). In addition, the redox transmetalation route was used for the synthesis of [LiInI(2-py6OtBu)3(THF)] (9). The structures of all compounds have been verified by single-crystal X-ray diffraction analysis, NMR spectroscopy, and mass spectrometry.

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands.

The synthesis of mixed-ligand complexes of the type [M2L(µ-L')]+, where L represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, L' is an azobenzene carboxylate co-ligand, and M = Cd(II), Ni(II) or Zn(II), is reported. A series of new complexes were synthesized, namely [M2L(µ-L')]+ (L' = azo-H, M = Cd (1), Ni (2); L' = azo-OH, M = Zn (3), Ni (4); L' = azo-NMe2, M = Zn (5), Cd (6), Ni (7); L' = azo-CO2Me, M = Cd (8), Ni (9)), and characterized by elemental analysis, electrospray ionization mass spectrometry (ESIMS), IR, UV-vis and NMR spectroscopy (for diamagnetic Zn and Cd complexes) and X-ray single crystal structure analysis. The crystal structures of 3' and 5-8 display an isostructural series of compounds with bridging azobenzene carboxylates in the trans form. The paramagnetic Ni complexes 2, 4 and 7 reveal a weak ferromagnetic exchange interaction with magnetic exchange coupling constant values between 21 and 23 cm-1 (H = -2JS1S2). Irradiation of 1 with λ = 365 nm reveals a photoisomerization of the co-ligand from the trans to the cis form.

Zinc Tin Chalcogenide Complexes and Their Evaluation as Molecular Precursors for Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe).

A series of five heteronuclear zinc tin chalcogenide complexes with the general formula [(tmeda)Zn(SnR2)2E3] (1-R, E = S; R = Me, Ph, tBu; 2-R, E = Se; R = Ph, tBu) have been synthesized and characterized by X-ray crystal structure analysis. In all cases, the six-membered ZnSn2E3 rings exhibit twist boat conformation. The presence of the molecular structures in solution is confirmed by 119Sn and 77Se NMR spectroscopy. Cothermolysis experiments using a mixture of complexes 1-R or 2-R and [(iPr3PCu)2(EC2H4E)]2 as a copper source were monitored by thermogravimetry and temperature dependent X-ray powder diffraction to examine the thermolysis reaction. According to Rietveld refinement, the solid residue consists of Cu2ZnSnS4 (up to 78 wt %) or Cu2ZnSnSe4 (up to 43 wt %) as the main product, respectively.

Family history density of substance use problems among undergraduate college students: Associations with heavy alcohol use and alcohol use disorder.

PURPOSE: A family history of alcoholism has been found associated with problematic alcohol use among college students, but less research has examined the effects of family history density of substance use problems in this population. This study examined the prevalence of family history density of substance use problems and its associations with heavy alcohol use, negative alcohol consequences, and alcohol use disorder in a college sample. METHODS: Based on a secondary analysis of a probability sample, data were analyzed from 606 undergraduate students. Family history density of substance use problems included both first and second degree biological relatives. Heavy alcohol use was the total number of days in which participants drank five/four or more drinks for men/women, negative alcohol consequences were derived from items commonly asked in college student surveys, and an alcohol use disorder was defined as meeting diagnostic criteria for alcohol abuse or dependence. Point prevalence estimated rates of family history density of substance use problems, and negative binomial, ANCOVA, and logistic regression models examined associations between family history density and the alcohol variables while adjusting for sociodemographic variables. RESULTS: Family history density of substance use problems was not significantly associated with total days of heavy alcohol use. Having a second degree, a first degree, or both a first and second degree relative(s) with a substance use problem, however, was significantly associated with experiencing negative alcohol consequences. In addition, having both a first and second degree relative(s) with a substance use problem significantly increased the odds of having an alcohol use disorder. CONCLUSIONS: Family history density of substance use problems may play a role in experiencing negative alcohol consequences and in having an alcohol use disorder among undergraduate college students and may be an important risk factor to assess by college health professionals.

Copper Zinc Thiolate Complexes as Potential Molecular Precursors for Copper Zinc Tin Sulfide (CZTS).

Five copper zinc thiolate complexes [(iPr3 PCu)2 (ZnEt2 )(edt)]2 (1-Et), [(iPr3 PCu)2 (Zn(iPr)2 )(edt)]2 (1-iPr), [(iPr3 PCu)4 (edt)2 (ZnMe2 )]2 (2), [(iPr3 PCu)3 (ZnPh2 )(ZnPh)(edt)2 ]2 (3), and [(iPr3 PCu)2 Zn2 (edt)3 ]6 (4) were prepared by the reaction of [(iPr3 PCu)2 (edt)]2 with ZnR2 (R=Me, Et, Ph, iPr) with or without addition of ethanedithiol (edt2- =ethane-1,2-dithiolate). The molecular structures of these complexes were determined by single crystal X-ray diffraction. The ethanedithiolate ligands coordinate in µ3 -η1 :η2 :η1 (2, 4), µ4 -η1 :η1 :η2 :η1 (1-R, 3), and µ5 -η1 :η1 :η2 :η1 :η1 (2) bridging modes, each sulfur atom binds to two or three metal atoms. Evidence for the presence of the weak Zn-S bonds in solution was provided by NMR spectroscopy. Mixtures of 1-Et, 1-iPr, or 3 with Sn(edt)2 were examined by thermogravimetry up to 600 °C, whereupon volatile thermolysis products were identified by mass spectrometry. In all thermolysis experiments, the formation of Cu2 ZnSnS4 as main product, besides small amounts of binary metal sulfides, was confirmed by X-ray powder diffraction (PXRD) and EDX (energy dispersive X-ray spectroscopy) analysis.

Quantitative two-dimensional measurement of oil-film thickness by laser-induced fluorescence in a piston-ring model experiment.

This paper describes advances in using laser-induced fluorescence of dyes for imaging the thickness of oil films in a rotating ring tribometer with optical access, an experiment representing a sliding piston ring in an internal combustion engine. A method for quantitative imaging of the oil-film thickness is developed that overcomes the main challenge, the accurate calibration of the detected fluorescence signal for film thicknesses in the micrometer range. The influence of the background material and its surface roughness is examined, and a method for flat-field correction is introduced. Experiments in the tribometer show that the method yields quantitative, physically plausible results, visualizing features with submicrometer thickness.

Synthesis and Structural Elucidation of Triazolylmolybdenum(VI) Oxide Hybrids and Their Behavior as Oxidation Catalysts.

A large family of bifunctional 1,2,4-triazole molecular tectons (tr) has been explored for engineering molybdenum(VI) oxide hybrid solids. Specifically, tr ligands bearing auxiliary basic or acidic groups were of the type amine, pyrazole, 1H-tetrazole, and 1,2,4-triazole. The organically templated molybdenum(VI) oxide solids with the general compositions [MoO3(tr)], [Mo2O6(tr)], and [Mo2O6(tr)(H2O)2] were prepared under mild hydrothermal conditions or by refluxing in water. Their crystal structures consist of zigzag chains, ribbons, or helixes of alternating cis-{MoO4N2} or {MoO5N} polyhedra stapled by short [N-N]-tr bridges that for bitriazole ligands convert the motifs into 2D or 3D frameworks. The high thermal (235-350 °C) and chemical stability observed for the materials makes them promising for catalytic applications. The molybdenum(VI) oxide hybrids were successfully explored as versatile oxidation catalysts with tert-butyl hydroperoxide (TBHP) or aqueous H2O2 as an oxygen source, at 70 °C. Catalytic performances were influenced by the different acidic-basic properties and steric hindrances of coordinating organic ligands as well as the structural dimensionality of the hybrid.

The utility of collateral student drinking reports: Evidence from a biomarker study.

INTRODUCTION: Researchers have increasingly used collateral informants to validate the reports provided by primary research subjects. We assessed the utility of collateral informants for college students in a study that incorporates biomarkers to validate student reports of recent drinking behavior. METHODS: Students from a Midwestern university were randomly selected for a study in which they provided 90-day Timeline Followback data, hair and fingernail specimens for ethylglucuronide (EtG) testing, and information about collateral (friends or peers) informants who were familiar with their drinking behavior. We compared summary measures of recent drinking to collateral informant reports for the subset of 72 students who were selected to participate in the collateral validation process who had complete measures. Kappa, weighted kappa, and McNemar tests were performed to evaluate levels of agreement. We compared levels of use indicated by each informant within the context of EtG findings. We also compared respondent and collateral reports with respect to heavy drinking directly to EtG test results. RESULTS: There was considerable overlap between the reports provided by the student participants and their collateral informants. Within the context of EtG-informed analyses, collaterals rarely provided new information about heavy use beyond that provided by the study subjects. CONCLUSIONS: Collateral informants have limited utility in non-clinical studies of heavy drinking in randomly selected college students.

Ethyl glucuronide in hair and fingernails as a long-term alcohol biomarker.

AIMS: This study aimed to evaluate the performance of ethyl glucuronide (EtG) in hair and fingernails as a long-term alcohol biomarker. DESIGN: Cross-sectional survey with probability sampling. SETTING: Midwestern United States. PARTICIPANTS: Participants were 606 undergraduate college students between the ages of 18 and 25 years at the time of selection for potential study participation. MEASUREMENTS: EtG concentrations in hair and fingernails were measured by liquid chromatography-tandem mass spectrometry at three thresholds [30 picograms (pg) per milligram (mg); 20 pg/mg; and 8 pg/mg]. Any weekly alcohol use, increasing-risk drinking and high-risk drinking on average during the past 12 weeks was assessed by participant interview using the time-line follow-back method. FINDINGS: In both hair and fingernails at all three EtG thresholds, sensitivity was greatest for the high-risk drinking group [hair: 0.43, confidence interval (CI)=0.17, 0.69 at 30 pg/mg, 0.71, CI=0.47, 0.95 at 20 pg/mg; 0.93, CI=0.79, 1.00 at 8 pg/mg; fingernails: 1.00, CI=1.00-1.00 at 30, 20 and 8 pg/mg] and specificity was greatest for any alcohol use (hair: 1.00, CI=1.00, 1.00 at 30 and 20 pg/mg; 0.97, CI=0.92-0.99 at 8 pg/mg; fingernails: 1.00, CI=1.00-1.00 at 30, 20 and 8 pg/mg). Areas under the receiver operating characteristic curves were significantly higher for EtG concentration in fingernails than hair for any weekly alcohol use (P = 0.02, DeLong test, two-tailed) and increasing-risk drinking (P = 0.02, DeLong test, two-tailed). CONCLUSIONS: Ethyl glucuronide, especially in fingernails, may have potential as a quantitative indicator of alcohol use.

Alcohol mixed with energy drinks: are there associated negative consequences beyond hazardous drinking in college students?

OBJECTIVE: The consumption of alcohol mixed with energy drinks (AmED) is prevalent among college students as is hazardous drinking, a drinking pattern that places one at risk for alcohol-related harm. The present study, therefore, examined associations between AmED use, hazardous drinking, and alcohol-related consequences in college students. METHODS: Based on a probability sample conducted in 2010, participants were 606 undergraduate students aged 18-25. AmED consumption included lifetime and past year use. Hazardous drinking and alcohol-related consequences were measured during the past year. Point prevalence was used to estimate rates of AmED use, and chi-square, ANOVA, and logistic regression were used to examine associations between AmED use, hazardous drinking, and alcohol-related consequences. RESULTS: Lifetime and past year AmED use prevalence rates were 75.2% and 64.7%, respectively. Hazardous drinkers who engaged in AmED use were significantly more likely than past year hazardous drinkers who did not engage in AmED use to have had unprotected sex (OR=2.35, CI 1.27-4.32). CONCLUSIONS: AmED use appears to be highly prevalent among college students, and AmED use may confer additional risk for unprotected sex beyond hazardous drinking. Unprotected sex has implications for public health, and students who drink hazardously and consume AmED may be at greater risk.

Liquid Chromatography-Tandem Mass Spectrometry Assay to Detect Ethyl Glucuronide in Human Fingernail: Comparison to Hair and Gender Differences.

Over the past decade, the use of hair specimens for the long-term detection of the alcohol biomarker ethyl glucuronide has been increasing in popularity and usage. We evaluated the usefulness of fingernail clippings as a suitable alternative to hair for ethyl glucuronide detection. A liquid chromatography-tandem mass spectrometry method for the detection of ethyl glucuronide in fingernail clippings was fully validated and used to analyze the hair and/or fingernail specimens of 606 college-aged study participants. The limit of detection was 2 pg/mg, the limit of quantitation was 8 pg/mg and the method was linear from 8 to 2000 pg/mg. Intra- and inter-assay imprecision studies at three different concentrations (20, 40, 200 pg/mg) were all within 7.8% and all intra- and inter-assay bias studies at these levels were within 115.1% of target concentration. Ethyl glucuronide levels in fingernail (mean = 29.1 ± 55.6 pg/mg) were higher than ethyl glucuronide levels in hair (mean = 9.48 ± 22.3 pg/mg) and a correlation of the matched pairs was observed (r = 0.552, P < 0.01, n = 529). Evaluating each gender separately revealed that the correlation of male fingernail to male hair was large and significant (r = 0.782, P < 0.01, n = 195) while female hair to female fingernail was small yet significant (r = 0.249, P < 0.01, n = 334). The study results demonstrated that fingernail may be a suitable alternative to hair for ethyl glucuronide detection and may be the preferred sample type due to the lack of a gender bias.

Software for automated analysis of DNA fingerprinting gels.

Here we describe software tools for the automated detection of DNA restriction fragments resolved on agarose fingerprinting gels. We present a mathematical model for the location and shape of the restriction fragments as a function of fragment size, with model parameters determined empirically from "marker" lanes containing molecular size standards. Automated identification of restriction fragments involves several steps, including: image preprocessing, to put the data in a form consistent with a linear model; marker lane analysis, for determination of the model parameters; and data lane analysis, a procedure for detecting restriction fragment multiplets while simultaneously determining the amplitude curve that describes restriction fragment amplitude as a function of mobility. In validation experiments conducted on fingerprinted and sequenced Bacterial Artificial Chromosome (BAC) clones, sensitivity and specificity of restriction fragment identification exceeded 96% on restriction fragments ranging in size from 600 base pairs (bp) to 30,000 bp. The integrated suite of software tools, written in MATLAB and collectively called BandLeader, is in use at the BC Cancer Agency Genome Sciences Centre (GSC) and the Washington University Genome Sequencing Center, and has been provided to the Wellcome Trust Sanger Institute and the Whitehead Institute. Employed in a production mode at the GSC, BandLeader has been used to perform automated restriction fragment identification for more than 850,000 BAC clones for mouse, rat, bovine, and poplar fingerprint mapping projects.