RESUMO
Quantum interference (QI) of electron waves passing through a single-molecule junction provides a powerful means to influence its electrical properties. Here, we investigate the correlation between substitution pattern, conductance, and mechanosensitivity in [2.2]paracyclophane (PCP)-based molecular wires in a mechanically controlled break junction experiment. The effect of the meta versus para connectivity in both the central PCP core and the phenyl ring connecting the terminal anchoring group is studied. We find that the meta-phenyl-anchored PCP yields such low conductance levels that molecular features cannot be resolved; in the case of para-phenyl-coupled anchoring, however, large variations in conductance values for modulations of the electrode separation occur for the pseudo-para-coupled PCP core, while this mechanosensitivity is absent for the pseudo-meta-PCP core. The experimental findings are interpreted in terms of QI effects between molecular frontier orbitals by theoretical calculations based on density functional theory and the Landauer formalism.
RESUMO
Neurodegenerative diseases significantly impact individuals' nutritional status. Therefore, nutritional education plays a crucial role in enhancing the understanding of food and nutrition, preventing or minimizing malnutrition, promoting well-being, and empowering patients and caregivers. Educommunication is a methodology that utilizes communication as a pedagogical tool, with the potential to positively enhance the teaching-learning process. This study aims to identify and map educommunication strategies designed to educate caregivers and patients with neurodegenerative diseases about food and nutrition. METHODS: This scoping review followed the JBI Institute Reviewer's Manual. The search was conducted between June 2022 and March 2023 in databases including PubMed/MEDLINE, Embase, Scopus, and Web of Science. RESULTS: Out of 189 studies identified, 29 met the eligibility criteria, and only 3 were suitable for inclusion in this review. CONCLUSION: Studies using educommunication for food and nutrition education are scarce. Despite the limited number of studies included in this review, various educommunication strategies utilizing communication and information technologies were used. Educommunication strategies can facilitate knowledge acquisition in food and nutrition and change behaviors, resulting in health benefits for the participants. More studies on this subject are needed.
Assuntos
Doenças Neurodegenerativas , Humanos , Estado Nutricional , Educação em Saúde/métodos , Comunicação , Ciências da Nutrição/educaçãoRESUMO
Break-junction techniques provide the possibility to study electric and thermoelectric properties of single-molecule junctions in great detail. These techniques rely on the same principle of controllably breaking metallic contacts in order to create single-molecule junctions, whilst keeping track of the junction's conductance. Here, we compare results from mechanically controllable break junction (MCBJ) and scanning tunneling microscope (STM) methods, while characterizing conductance properties of the same novel mechanosensitive para- and meta-connected naphtalenophane compounds. In addition, thermopower measurements are carried out for both compounds using the STM break junction (STM-BJ) technique. For the conductance experiments, the same data processing using a clustering analysis is performed. We obtain to a large extent similar results for both methods, although values of conductance and stretching lengths for the STM-BJ technique are slightly larger in comparison with the MCBJ. STM-BJ thermopower experiments show similar Seebeck coefficients for both compounds. An increase in the Seebeck coefficient is revealed, whilst the conductance decreases, after which it saturates at around 10 µV K-1. This phenomenon is studied theoretically using a tight binding model. It shows that changes of molecule-electrode electronic couplings combined with shifts of the resonance energies explain the correlated behavior of conductance and Seebeck coefficient.
RESUMO
Herein, we report the isolation of new heterobimetallic complexes [Ni(0.6)Pd(1.4)(EtCS(2))(4)] (1), [NiPt(EtCS(2))(4)] (2) and [Pd(0.4)Pt(1.6)(EtCS(2))(4)] (3), which were constructed by using transmetallation procedures. Subsequent oxidation with iodine furnished the MM'X monodimensional chains [Ni(0.6)Pt(1.4)(EtCS(2))(4)I] (4) and [Ni(0.1)Pd(0.3)Pt(1.6)(EtCS(2))(4)I] (5). The physical properties of these systems were investigated and the chain structures 4 and 5 were found to be reminiscent of the parent [Pt(2)(EtCS(2))(4)I] species. However, they were more sensitively dependent on the localised nature of the charge on the Ni ion, which caused spontaneous breaking of the conduction bands.
RESUMO
The solvothermal reactions between pyrimidinedisulfide (pym(2)S(2)) and CuI or CuBr(2) in CH(2)Cl(2):CH(3)CN lead to the formation of [Cu(11)I(7)(pymS)(4)](n) (pymSH = pyrimidine-2(1H)-thione) (1) and the dimer [Cu(II)(µ-Br)(Br)L](2) (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde) (2). In the later reaction, there is an in situ S-S, S-C(sp(2)), and C(sp(2))-N multiple bond cleavage of the pyrimidinedisulfide resulting in the formation of 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde. Interestingly, similar reactions carried out just with a change in the solvent (H(2)O:CH(3)CN instead of CH(2)Cl(2):CH(3)CN) give rise to the formation of coordination polymers with rather different architectures. Thus, the reaction between pym(2)S(2) and CuI leads to the formation of [Cu(3)I(pymS)(2)](n) (3) and [CuI(pym(2)S(3))] (pym(2)S(3) = pyrimidiltrisulfide) (4), while [Cu(3)Br(pymS)(2)](n) (5) is isolated in the reaction with CuBr(2). Finally, the solvothermal reactions between CuI and pyrimidine-2-thione (pymSH) in CH(2)Cl(2):CH(3)CN at different ratios, 1:1 or 2:1, give the polymers [Cu(2)I(2)(pymSH)(2)](n) (6) and [Cu(2)I(2)(pymSH)](n) (7), respectively. The structure of the new compounds has been determined by X-ray diffraction. The studies of the physical properties of the novel coordination polymers reveal that compounds 3 and 5 present excellent electrical conductivity values at room temperature, while compounds 1, 3, and 5-7 show luminescent strong red emission at room temperature.
Assuntos
Complexos de Coordenação/química , Cobre/química , Polímeros/química , Pirimidinas/química , Sulfetos/química , Cristalografia por Raios X , Condutividade Elétrica , Ligantes , Luminescência , Modelos MolecularesRESUMO
The synthesis and characterization of compound [Rh(2)(O(2)CEt)(4)(H(2)O)(2)] (1) and one-dimensional heterobimetallic polymers K(n){Rh(2)(O(2)CEt)(4)[Au(CN)(2)]}(n) (2) and K(n){Rh(2)(O(2)CMe)(4)[Au(CN)(2)]}(n)·4nH(2)O (3), constructed from dirhodiumtetracarboxylato units, [Rh(2)(O(2)CR)(4)](+), and dicyanoaurate, [Au(CN)(2)](-), fragments are described. In both compounds 2 and 3 the resulting polymeric chains are nonlinear and have in common similar structural parameters, although the solid state supramolecular arrangement is very different. These structural differences explain the fact that complex 2 displays aurophilic interactions while this type of interactions are absent in complex 3. As a result, compound 2 shows rich blue luminescent properties whereas compound 3 is not luminescent. The electrical conductivity in solid state of compounds 2 and 3 is also studied.
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An accurate, rapid and sensitive high-performance liquid chromatographic (HPLC) method is reported for the determination of four biogenic amines in red and white wine samples. The method involves derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) followed by liquid chromatography gradient elution analysis without any other sample pretreatment. The procedure developed permitted the determination of the four amines in 40 min. The relative standard deviation (RSD) values ranged from 3.1% to 6.1% in peak areas and the response was linear (R2>0.994) in a range from 0.1 to 4 mg/l. Leaving aside putrescine in Tempranillo wines, the malolactic fermentation did not exert any effect on the concentration of these compounds. On the contrary, the influence of the grape variety was important, and Tempranillo wines showed higher levels of tyramine and histamine and lesser of putrescine and cadaverine (p<0.05) than wines made with Cabernet Sauvignon.
Assuntos
Aminoquinolinas/química , Aminas Biogênicas/análise , Carbamatos/química , Ácido Láctico/metabolismo , Malatos/metabolismo , Vinho/análise , Cadaverina/análise , Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , Fermentação , Histamina/análise , Ácido Láctico/química , Malatos/química , Putrescina/análise , Reprodutibilidade dos Testes , Especificidade da Espécie , Tiramina/análise , Vitis/químicaRESUMO
Direct sublimation of a Cu4Cl4 metal-organic cluster on Cu(110) under ultra-high vacuum allows the formation of ultra-large well-organized metal-organic supramolecular wires. Our results show that the large monomers assemble with each other by π-π interactions connecting dipyrimidine units and are stabilized by the surface.
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Two oligomers, that is, para-phenylenevinylene with either pendant Pd(ii)Pc or Zn(ii)Pc units, have been synthesized and their interactions with SWCNTs and peapods - C60@SWCNT - have been probed by complementary spectroscopy and microscopy. Spectroscopy assisted mainly in shedding light onto electronic interactions in the ground and excited state, while microscopy enabled insights into the degree of individualizing SWCNTs/C60@SWCNTs and their stabilization.
RESUMO
A coordination polymer is fully exfoliated by solvent-assisted interaction only. The soft-delamination process results from the structure of the starting material, which shows a layered structure with weak layer-to-layer interactions and cavities with the ability to locate several solvents in an unselective way. These results represent a significant step forward towards the production of structurally designed one-molecule thick 2D materials with tailored physico-chemical properties.
RESUMO
An unprecedented in situ multiple bond cleavage of S-S, S-C(sp(2)) and C-N in the pyrimidinedisulfide (pym(2)S(2)) ligand is observed by the reaction of CuCl(2)·2H(2)O with this ligand under solvothermal and solvothermal-microwave conditions. In this process the formation of the compound [Cu(II)(µ-Cl)(Cl)L](2), where L represents the new ligand (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde), is observed. This ligand has been further isolated and X-ray characterized. The similar reaction carried out under solvothermal-microwave conditions gives, in addition to the latter compound, the complex {9·[Cu(pym(2)S(3))(µ-Cl)(Cl)](2)·[Cu(pym(2)S(2))(µ-Cl)(Cl)](2)}. Coordination of a pyrimidinetrisulfide ligand (pym(2)S(3)) is reported for the first time. This work represents an illustrative example of the novel synthetic perspectives attainable via solvothermal-microwave procedures.