The Stability of Hydrogen-Bonded Ion-Pair Complex Unexpectedly Increases with Increasing Solvent Polarity.

The generally observed decrease of the electrostatic energy in the complex with increasing solvent polarity has led to the assumption that the stability of the complexes with ion-pair hydrogen bonds decreases with increasing solvent polarity. Besides, the smaller solvent-accessible surface area (SASA) of the complex in comparison with the isolated subsystems results in a smaller solvation energy of the latter, leading to a destabilization of the complex in the solvent compared to the gas phase. In our study, which combines Nuclear Magnetic Resonance, Infrared Spectroscopy experiments, quantum chemical calculations, and molecular dynamics (MD) simulations, we question the general validity of this statement. We demonstrate that the binding free energy of the ion-pair hydrogen-bonded complex between 2-fluoropropionic acid and n-butylamine (CH3CHFCOO-…NH3But+) increases with increased solvent polarity. This phenomenon is rationalized by a substantial charge transfer between the subsystems that constitute the ion-pair hydrogen-bonded complex. This unexpected finding introduces a new perspective to our understanding of solvation dynamics, emphasizing the interplay between solvent polarity and molecular stability within hydrogen-bonded systems.

Seasonal and weekly fluctuations in alcohol use in the Czech Republic.

Sezónní a týdenní výkyvy v uzívání alkoholu patrí mezi doposud neanalyzované aspekty epidemiologického výzkumu uzívání alkoholu ceskou dospelou populací. Cílem studie je nabídnout deskriptivní a analytický pohled na sezónní a týdenní vzorce uzívání alkoholu u ceské dospelé populace. Výzkum byl realizován na reprezentativním vzorku 809 osob v rámci on-line setrení v prostredí Ceského národního panelu. Sledovanými promennými jsou uzívání alkoholu, sezónní uzívání a uzívání alkoholu v rámci dní v týdnu. Výsledky ukazují, ze nejcastejsí je konzumace v pátek, prípadne v sobotu, s výjimkou lidí v duchodovém veku, kterí alkohol uzívání rovnomerneji v rámci celého týdne. Z hlediska mesícu v roce je nejvyssí spotreba uvádena v léte (cerven, cervenec, srpen) a v prosinci. Respondenti s vyssím skóre dotazníku AUDIT uzívají alkohol více v letních mesících nez v prosinci. Výsledky výzkumu mohou prispet k lepsímu casovému zacílení preventivních i klinických aktivit.

Helicene-based π-conjugated macrocycles: their synthesis, properties, chirality and self-assembly into molecular stripes on a graphite surface.

Fully aromatic helicenes are attractive building blocks for the construction of inherently chiral π-conjugated macrocyclic nanocarbons. These hitherto rare molecular architectures are envisaged to exhibit remarkable (chir)optical properties, self-assembly, charge/spin transport, induced ring current or a fascinating Möbius topology. Here the synthesis of helically chiral macrocycles that combine angular dibenzo[5]helicene units as corners and linear trans-stilbene-4,4'-diyl linkers as edges is reported. By subjecting a racemic or enantiopure divinyl derivative of dibenzo[5]helicene to olefin metathesis, which was catalysed by a 2nd generation Piers catalyst under kinetic control, a π-conjugated helicene cyclic trimer (33%) and a tetramer (22%) were obtained, which were separated by GPC. Combining racemic/asymmetric synthesis with the resolution of enantiomers/diastereomers by SFC/HPLC on a chiral column, both homochiral (+)-(M,M,M)/(-)-(P,P,P) and heterochiral (+)-(M,M,P)/(-)-(M,P,P) stereoisomers of the helicene cyclic trimer could be obtained in an enantio- and diastereomerically enriched form. The complete energy profile of their interconversion was compiled on the basis of kinetic measurements and numerical solution of the proposed kinetic model. In equilibrium, the heterochiral diastereomer predominates over the homochiral one (ca. 75 : 25 at 76 °C). π-Conjugation along a large, twisted circuit in the helicene cyclic trimer is rather disrupted, stabilising this formally antiaromatic molecule. Using an optimised PeakForce mode of ambient AFM, the self-assembly of otherwise highly mobile stereoisomers of the helicene cyclic trimer on the HOPG surface could be studied. Irrespective of the stereochemistry, strong preferences for the edge-to-edge interaction of these macrocycles were found to form very long parallel 1D molecular stripes in ordered 2D nanocrystals, a result also supported by molecular dynamics simulations. Six trityl groups, initially introduced to the macrocycle to enhance solubility, serve as a key "molecular Velcro" system in the self-assembly of macrocycles to maximise their mutual van der Waals interactions.

Push-pull amino-nitro helicenes: synthesis, (chir)optical properties and self-assembly into thin films.

A series of regioisomeric push-pull amino-nitro [6]helicenes and a related [7]helicene derivative were prepared and their racemates resolved into enantiomers. Compared to the parent helicenes, they exhibit red-shifted UV-Vis spectra, pronounced dipole moments, altered chiroptical properties such as remarkable optical rotatory power, and can form nanocrystalline Langmuir-Blodgett films.

Nonaqueous capillary electrophoresis and quantum chemical calculations applied to investigation of acid-base and electromigration properties of azahelicenes.

Nonaqueous capillary electrophoresis (NACE) using methanol (MeOH) as a solvent of the BGEs and quantum mechanical density functional theory (DFT) have been applied to determine the thermodynamic acidity (ionization) constants (pKa ) of mono- and diaza[5]helicenes, mono- and diaza[6]helicenes, and their dibenzo derivatives in MeOH and water. First, the mixed acidity constants, pKa,MeOHmix${\rm{p}}K_{{\rm{a,MeOH}}}^{{\rm{mix}}}$ , of ionogenic pyridinium groups of azahelicenes and their derivatives in MeOH were obtained by nonlinear regression analysis of pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by NACE in a large series of methanolic BGEs within a wide conventional pH range (pHMeOH 1.6-12.0) and at ambient temperature (21-26°C) in a home-made CE device. Prior to mixed acidity constant calculation, the effective mobilities were corrected to reference temperature (25°C) and constant ionic strength (25 mM). Then, the mixed acidity constants were recalculated to the thermodynamic acidity constants pKa,MeOH by the Debye-Hückel theory of nonideality of electrolyte solutions. Finally, from the methanolic thermodynamic pKa,MeOH values, the aqueous thermodynamic pKa,H2O${\rm{p}}{K_{{\rm{a,}}{{\rm{H}}_{\rm{2}}}{\rm{O}}}}$ constants were estimated using the empirical relations between methanolic and aqueous acidity constants derived for structurally related pyridine derivatives. Depending on the number and position of the nitrogen atoms in their molecules, the analyzed azahelicenes were found to be weak to moderate bases with methanolic pKa,MeOH in the range 2.01-8.75 and with aqueous pKa,H2O${\rm{p}}{K_{{\rm{a,}}{{\rm{H}}_{\rm{2}}}{\rm{O}}}}$ in the range 1.67-8.28. The thermodynamic pKa,MeOH obtained by the DFT calculations were in a good agreement with those determined experimentally by NACE.

Measuring Parental Behavior towards Children's Use of Media and Screen-Devices: The Development and Psychometrical Properties of a Media Parenting Scale for Parents of School-Aged Children.

Children's excessive screen use is associated with health risks such as obesity, sleep problems, attention problems, and others. The effect of parental regulative efforts focused on screen/media use (media parenting) is currently unclear and difficult to examine given the heterogeneity of measuring tools used for its assessment. We aimed to develop an inventory that would enable reliable and valid measurement of media parenting practices (especially active and restrictive mediation) in parents of primary school children. The inventory builds on existing tools, it is comprehensive, yet easy to use in research setting. The original MEPA-36 (36 items) and revised MEPA-20 (20 items) inventories were examined using data from 341 Czech and Slovak parents of children aged between 6 and 10 years. Psychometrical properties were estimated using confirmatory factor and reliability analyses. Model fit was better for MEPA-20 and similar to other currently available tools. Both active and restrictive mediation subscales demonstrated high internal consistency. The internal consistency of newly constructed risky mediation subscales (risky active, risky restrictive, and over-protective mediation) was low. MEPA-20, especially active and restrictive mediation subscales, can be recommended for research on media parenting in context of screen/media use of school-aged children.

The effects of parental control and warmth on problematic internet use in adolescents: A prospective cohort study.

Background and aims: Problematic internet use (PIU) is a highly prevalent condition with severe adverse effects. The literature suggests that parent-child bonding and parental behavioral control exert protective effects against PIU. However, the most relevant studies rely on simplistic measurement of parenting, cross-sectional designs and mixed-aged samples. Our study analyzed the effect of maternal and paternal parenting on PIU by using a prospective design and a cohort sample of same-aged children. Methods: Data from 1,019 Czech 12-year-old sixth-graders who were followed until ninth grade were used. Maternal and paternal responsiveness and strictness were reported by children using the Parental Acceptance-Rejection Questionnaire (PARQ) and the Parental Control Scale (PCS). PIU was measured by the Excessive Internet Use Scale (EIUS). Results: The self-reported PIU prevalence in nine-graders (15-year-old) was 8.1%. Parenting, reported by adolescents 18 months before PIU screening, showed significant relationships with PIU: parental responsiveness was negatively and moderately associated, while maternal strictness showed a weak positive association; the authoritative parenting style in both parents decreased PIU, with a PIU probability of 3.21%, while a combination of maternal authoritarian and paternal neglectful parenting was associated with PIU probability as high as 20.9%. Discussion and conclusions: The self-reported prevalence of PIU in Czech adolescents was found to be high. The effects of parenting on PIU were similar to the effects of parenting on other problematic behavior among adolescents. Our findings showed the need for interventions to prevent PIU by helping parents to apply optimal parenting styles.

Interaction of Socioeconomic Status with Risky Internet Use, Gambling and Substance Use in Adolescents from a Structurally Disadvantaged Region in Central Europe.

BACKGROUND AND AIMS: The current level of knowledge concerning the effect of socioeconomic status (SES) on internet use, gambling, and substance use in structurally disadvantaged regions is scarce. The objective of this study was an investigation of the relationship between SES and risky internet use, gambling and substance use in a structurally disadvantaged region in Central Europe. METHODS: A cross-sectional survey was conducted among high school students (n = 1063) in a Czech structurally disadvantaged region in autumn 2017. Binary Logistic Regression models were applied to data from the modified Excessive Internet Use scale (mEIUS), a standard tool for measuring the risk of addictive behavior on the internet and the risk of excessive gaming. Other data were collected using the Lie/Bet (problematic gambling), CAGE (acronym of the key words: cut, angry, guilty and eye-opener), and the Cannabis Abuse Screening Test (CAST) (problematic alcohol/cannabis use) tools. RESULTS: There were statistically significant differences between at-risk and not-at-risk groups in addictive behavior on the internet and gaming, while none were found in problematic gambling. Individual dimensions of SES showed significant effects on substance use. Regarding parenting styles, significant differences were found only in the risk of addictive behavior on the internet or gaming between the authoritarian and authoritative styles. Being engaged in behavioral addictions with one´s parents increased the odds of the behavioral addiction risk and decreased the odds of the substance addiction risk. Engagement with one´s parents in substance addictions decreased the odds of the behavioral addiction risk and increased the odds of the substance addiction risk. DISCUSSION AND CONCLUSIONS: The results point at specific relations between SES and the risk of addictive behaviors on the internet and gaming within structurally disadvantaged regions. The results of SES and/or structurally disadvantaged region measures obtained in research, policy-making, and care-provision may improve the focus of actions taken.

Synthesis of Racemic, Diastereopure, and Enantiopure Carba- or Oxa[5]-, [6]-, [7]-, and -[19]helicene (Di)thiol Derivatives.

A series of carba- or oxa[5]-, [6]-, [7]-, and -[19]helicene (di)thiols was prepared. The Miyazaki-Newman-Kwart rearrangement of (dimethylcarbamothioyl)oxy (oxa)helicenes in a flow reactor or nucleophilic substitution of dichloro (oxa)helicenes with alkanethiolates were used in the sulfanylation step. Despite the high temperatures employed in this key step, no conformational scrambling was observed during the asymmetric synthesis of the diastereo- and enantiopure oxahelicenes. Single-molecule conductivity of the longest oxa[19]helicene dithiol derivative was studied by the scanning tunneling microscopy break-junction method.

Chirality-Controlled Self-Assembly of Amphiphilic Dibenzo[6]helicenes into Langmuir-Blodgett Thin Films.

Racemic and highly enantioenriched 3-methoxycarbonyl, 3-carboxy, and 3-hydroxymethyl derivatives of dibenzo[6]helicene were prepared. The Langmuir layers of these helicenes were formed at the air-water interface and transferred onto solid substrates to afford Langmuir-Blodgett films, which were then studied by ambient atomic force microscopy and (chir)optical spectroscopy. Significant differences were found in the behaviour of the Langmuir layers as well as in the morphology, UV/Vis, electronic circular dichroism (ECD), and fluorescence spectra of the Langmuir-Blodgett thin films depending on the molecular chirality and nature of the polar group. The experimental results were supported by molecular dynamics simulations.

Tuning the Porosity and Photocatalytic Performance of Triazine-Based Graphdiyne Polymers through Polymorphism.

Crystalline and amorphous organic materials are an emergent class of heterogeneous photocatalysts for the generation of hydrogen from water, but a direct correlation between their structures and the resulting properties has not been achieved so far. To make a meaningful comparison between structurally different, yet chemically similar porous polymers, two porous polymorphs of a triazine-based graphdiyne (TzG) framework are synthesized by a simple, one-pot homocoupling polymerization reaction using as catalysts CuI for TzGCu and PdII /CuI for TzGPd/Cu . The polymers form through irreversible coupling reactions and give rise to a crystalline (TzGCu ) and an amorphous (TzGPd/Cu ) polymorph. Notably, the crystalline and amorphous polymorphs are narrow-gap semiconductors with permanent surface areas of 660 m2 g-1 and 392 m2 g-1 , respectively. Hence, both polymers are ideal heterogeneous photocatalysts for water splitting with some of the highest hydrogen evolution rates reported to date (up to 972 µmol h-1 g-1 with and 276 µmol h-1 g-1 without Pt cocatalyst). Crystalline order is found to improve delocalization, whereas the amorphous polymorph requires a cocatalyst for efficient charge transfer. This will need to be considered in future rational design of polymer catalysts and organic electronics.

Exploring the "Goldilocks Zone" of Semiconducting Polymer Photocatalysts by Donor-Acceptor Interactions.

Water splitting using polymer photocatalysts is a key technology to a truly sustainable hydrogen-based energy economy. Synthetic chemists have intuitively tried to enhance photocatalytic activity by tuning the length of π-conjugated domains of their semiconducting polymers, but the increasing flexibility and hydrophobicity of ever-larger organic building blocks leads to adverse effects such as structural collapse and inaccessible catalytic sites. To reach the ideal optical band gap of about 2.3 eV, A library of eight sulfur and nitrogen containing porous polymers (SNPs) with similar geometries but with optical band gaps ranging from 2.07 to 2.60 eV was synthesized using Stille coupling. These polymers combine π-conjugated electron-withdrawing triazine (C3 N3 ) and electron donating, sulfur-containing moieties as covalently bonded donor-acceptor frameworks with permanent porosity. The remarkable optical properties of SNPs enable fluorescence on-off sensing of volatile organic compounds and illustrate intrinsic charge-transfer effects.

Helicenes as Chirality-Inducing Groups in Transition-Metal Catalysis: The First Helically Chiral Olefin Metathesis Catalyst.

Helical chirality is a novel enantioselectivity-inducing property in transition-metal-catalyzed transformations. The principle is illustrated herein for the example of asymmetric olefin metathesis. This work reports the synthesis of the first helically chiral Ru-NHC alkylidene complex from an aminohelicene-derived imidazolium salt, which was ligated to the first generation Hoveyda-Grubbs catalyst. Kinetic data were acquired for benchmark test reactions and compared to an achiral catalyst. The helically chiral Ru-catalyst was evaluated in asymmetric ring-closing metathesis (RCM) and ring-opening metathesis-cross-metathesis (ROM/CM) reactions, which proceeded with promising levels of enantioselectivity. Extensive NMR-spectroscopic investigations and a DFT geometry optimization were performed. These results led to a topographic steric map and calculation of percent-buried-volume values for each quadrant around the metal center.

Large Converse Piezoelectric Effect Measured on a Single Molecule on a Metallic Surface.

The converse piezoelectric effect is a phenomenon in which mechanical strain is generated in a material due to an applied electrical field. In this work, we demonstrate the converse piezoelectric effect in single heptahelicene-derived molecules on the Ag(111) surface using atomic force microscopy (AFM) and total energy density functional theory (DFT) calculations. The force-distance spectroscopy acquired over a wide range of bias voltages reveals a linear shift of the tip-sample distance at which the contact between the molecule and tip apex is established. We demonstrate that this effect is caused by the bias-induced deformation of the spring-like scaffold of the helical polyaromatic molecules. We attribute this effect to coupling of a soft vibrational mode of the molecular helix with a vertical electric dipole induced by molecule-substrate charge transfer. In addition, we also performed the same spectroscopic measurements on a more rigid o-carborane dithiol molecule on the Ag(111) surface. In this case, we identify a weaker linear electromechanical response, which underpins the importance of the helical scaffold on the observed piezoelectric response.

Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor.

A series of oxahelicenes composed of ortho/meta-annulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2] cycloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene.

A Successful Strategy for Linking Anonymous Data from Students' and Parents' Questionnaires Using Self-Generated Identification Codes.

We conducted a feasibility study for matching children (N = 2571, average age 12 years, 50.4% female) and their parents (N = 1931, average age 41 years, 83.3% female) represented by an anonymous self-generated identification code (SGIC) and assessed its methodological properties. We used a nine-character SGIC with the children and a mirrored version of the same code with the parents. The average overall error rate in generating the SGIC was 9.7% (4.0% in the parents and 13.9% in the children). We were able to link a total of 1765 parents' and children's codes uniquely (94.9% of all possible dyads) with any four-character combination and the employment of the "school" variable. The overall matching quality of linking using the SGIC only is characterized by precision (positive predictive value) of 0.979, recall (sensitivity, true positive rate) of 0.934, and an F-measure (harmonic mean of precision and recall) of 0.956. The analysis of the discrepant characters in the dyads identified the paternal grandmother's name and eye color as those varying most often. This study is the first to look at SGIC match rates and error and omission rates in linking different subjects into dyads in prevention research. We identified a high number of unique child-parent matches while guaranteeing anonymity to the participants. We provided evidence that our SGIC is a suitable tool for between-group linking procedures and has a highly successful matching rate, while maintaining anonymity in the school-based prevention study samples.

From helical to planar chirality by on-surface chemistry.

The chirality of molecular structures is paramount in many phenomena, including enantioselective reactions, molecular self-assembly, biological processes and light or electron-spin polarization. Flat prochiral molecules, which are achiral in the gas phase or solution, can exhibit adsorption-induced chirality when deposited on surfaces. The whole array of such molecular adsorbates is naturally racemic as spontaneous global mirror-symmetry breaking is disfavoured. Here we demonstrate a chemical method of obtaining flat prochiral molecules adsorbed on the solid achiral surface in such a way that a specific adsorbate handedness globally dominates. An optically pure helical precursor is flattened in a cascade of on-surface reactions, which enables chirality transfer. The individual reaction products are identified by high-resolution scanning-probe microscopy. The ultimate formation of globally non-racemic assemblies of flat molecules through stereocontrolled on-surface synthesis allows for chirality to be expressed in as yet unexplored types of organic-inorganic chiral interfaces.

"It can't happen to me": Alcohol drinkers on the 2012 outbreak of methanol poisonings and the subsequent prohibition in the Czech Republic.

BACKGROUND: In September 2012, a series of methanol poisonings occurred in the Czech Republic as a result of an influx of illicit alcohol into (predominantly) cheap alcoholic beverages on the retail market. The public authorities decided to prevent public health risks by prohibiting sales of liquors that contained more than 20% alcohol (> 20% liquor). The "partial" prohibition lasted for almost two weeks, but the poisonings still continued. This article assesses the impact of the methanol poisoning risks and the (partial) prohibition on alcohol drinking patterns, and describes the understanding of risks and their mitigation in vulnerable groups. METHODS: The rapid assessment and response method (RAR) was used during the (partial) alcohol prohibition. Semi-structured interviews were conducted with respondents recruited for the study in alcohol-intake settings (e.g., bars and restaurants, street alcohol outlets) in six regions. In total, 107 alcohol users were interviewed, mostly with risky drinking patterns (69% scored ≥ 1 on the CAGE scale), and 53 alcohol retailers/staff members serving alcohol. RESULTS: About one third of the alcohol users in the study (35%) drank > 20% liquors during the prohibition; a higher score on the CAGE scale was associated with a lower probability of drinking > 20% liquors during the period of the prohibition, probably because of the perception of being at high risk of poisoning. There was some increase in drinking liquors with an alcohol content less than 20%. Those who continued drinking > 20% liquors typically did so in the belief that some sources of these were safe. CONCLUSIONS: Public policies aimed at reducing the risk of methanol poisonings in emergency situations should adopt broader measures than those focusing on market control. These measures include increased access to brief interventions, addressing the strategies that alcohol consumers adopt to prevent risk, and, in general, helping consumers make informed choices to prevent further fatalities.