V-Shaped 4,6-Bis(arylvinyl)pyrimidine Oligomers: Synthesis and Optical Properties

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Luminescence Behavior of Protonated Methoxy-Substituted Diazine Derivatives: Toward White Light Emission

White light-emitting diodes (WOLEDs) are an efficient alternative to conventional lighting sources. Nevertheless, approaches to obtain WOLEDs still require complex processes that lead to high costs. In this sense, the use of a single emitting material that can take two forms of complementary emitting colors has emerged as a new strategy for the fabrication of WOLEDs. In this paper we describe the luminescent behavior upon protonation of a series of D-π-A push–pull molecules based on a methoxyphenyl or methoxynaphthyl donor unit and a diazine acceptor unit with different π-bridges. The effect of protonation on the emission properties depends on the nature of the diazine ring. The addition of trifluoroacetic acid (TFA) to pyrazine and quinoxaline derivatives led to quenching of the fluorescence whereas pyrimidine derivatives remained luminescent after protonation, which prompted a color change in the emission due to the appearance of a new red-shifted band in the spectra. These results were rationalized with the help of TD-TFT calculations. White photoluminescence could be obtained in solution by the controlled protonation of some pyrimidines, which resulted in the formation of an orange emissive acidified form. This phenomenon opens up the possibility of exploiting these materials for the fabrication of WOLEDs

Theoretical and experimental study of the influence of (de)protonation of phenol-substituted diazine for White OLEDs

International audienceIn recent years, lighting has become more and more energy consuming, now reaching 20% of the global electricity consumption. Thus, there is need to properly design new environment friendly lighting devices and organic light emitting devices (OLEDs), in particular White OLEDs (WOLEDs), are more relevant than ever.[1] The major issue is that obtaining white light is not an easy task, and is in most cases achieved by using multilayer devices or a combination of different emissive molecules.[1,2] In this contribution, we present an innovative way of obtaining white light emission by modulating the protonation[3,4] and deprotonation of organic fluorophores. To this end, a series of 8 push-pull phenol substituted hydroxystyrildiazines has been designed by varying the nature of the acceptor diazinic heterocycle (pyrimidine/pyrazine) to be protonatedand of the linker moieties (thiophene, vinylene, thienylenevinylene, vinylphenylene). The photo-physical investigation of this series of compounds in solution showed a systematic bathochromic shift of the emission compared to the neutral form, not only upon the protonation, but also after deprotonation. Extensive Density Functional Theory (DFT) and TD-DFT calculations were performed to rationalize this behavior and understand the impact of (de)protonation on the different optical transitions characteristic of this family of fluorophores. Such computations showed that the (de)protonation impacts not only the energies of the vertical transitions, but also the nature of these transitions, with a significant increase in the Intramolecular Charge Transfer (ICT) character of the (de)excitations. Furthermore, playing with the nature of the diazinic moiety and the linker in the push-pull skeleton allows to fine tune the emission wavelength of the two forms and reach a complementary emission in solution.To the best of our knowledge, modulation of the emission by deprotonation has not yet been reported as an alternative strategy for obtaining WOLEDs. Our experimental and theoretical results on the phenol-substituted diazinic chromophores demonstrate that this approach proves successful, at least in solution. Thus, it opens a new route for the design of efficient WOLEDs and shall prompt further investigations up to device fabrication

PPV–PAMAM Hybrid Dendrimers: Self-Assembly and Stabilization of Gold Nanoparticles

Different generations of PPV–PAMAM hybrid dendrimers have been prepared and characterized. Our initial studies showed the high tendency of these materials to aggregate and form nanoassemblies in different media. Nile Red experiments and DLS measurements allowed us to determine the critical aggregation concentration (CAC) and the size of the aggregates, which have also been used to stabilize small gold nanoparticles. The nanoparticles influence the assembly and optical properties of the dendrimer molecules and lead to strong quenching of their intrinsic fluorescence. Nevertheless, these gold particles will be very useful as biomarkers in living cells by means of electron microscopy because of their high electron contrast

pH-Sensitive Fluorescence Lifetime Molecular Probes Based on Functionalized Tristyrylbenzene

The dependence of the fluorescence on pH for two 1,3,5-tristyrylbenzenes decorated with polyamine (compound <b>1</b>) and poly­(amidoamine) (compound <b>2</b>) chains at the periphery was investigated. The highest fluorescence intensities were observed under acidic conditions because electrostatic repulsions between positively charged molecules reduce the fluorescence quenching. The slopes observed in the fluorescence pH titration curves were associated with deprotonation of the different types of amine groups, which results in quenching by photoinduced electron transfer and aggregation processes. The linear dependence of fluorescence lifetime observed for different pH ranges is a valuable property for applications in the field of fluorescence lifetime sensors and imaging microscopy. The influence of the pH and the peripheral chains on the aggregation processes was also analyzed by absorption and emission spectroscopy, dynamic light scattering measurements, and transmission electron microscopy. For compound <b>1</b>, bands associated with the formation of aggregates were detected along with micrometric aggregates surrounded by fibers with lattice fringes typical of columnar mesophases. For compound <b>2</b>, which contains longer peripheral chains with a higher degree of branching, aggregates with lower internal order were observed. In this case, the peripheral chains hindered aggregation by π-stacking although the amine groups did allow hydrogen bonding

Subtle C–H···Hal (Hal = Cl, Br) Bonding as Predominant Synthon in the Assembly of Supramolecular Architectures Based on Luminescent Tin(IV) Complexes. Crystallography, Hirshfeld Surfaces, DFT Calculations, and Fluorescence

This report illustrates a successful C–H···Hal synthon-directed strategy to promote supramolecular aggregation of molecular luminescent complexes <b>1</b>–<b>6</b> into two- or three-dimensional supramolecular architectures. The tin complexes were prepared from the reaction of R_<i>n</i>SnHal_4–<i>n</i> compounds (R = <i>n</i>-Bu, Ph; Hal = Cl, Br; <i>n</i> = 0, 1) with (C₅H₄N)­HCN­(C₆H₄)­EH Schiff bases by either step-by-step synthesis [E = O (PyNO)] or multicomponent reaction [E = S (PyNS)]. Compounds <b>1</b>–<b>6</b> were characterized by IR, Raman, and ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopic studies as well as by X-ray diffraction studies. In addition, the fluorescent properties of all compounds were also investigated in the solid state and in THF solutions; the emission wavelengths ranged from orange to red (λ_max = 591–626 nm). Detailed structural characterization of the supramolecular organization of ordered solids revealed overall 2D and 3D interlinked networks driven by extensive C–H···Hal–Sn (Hal = Cl, Br) weak hydrogen bonds as primordial synthon and further stabilized by π···π stacking interactions as well as C–H···π, C–H···O, or C–H···N contacts. Hirshfeld surface analysis and DFT calculations were used to asses additional insights into crystal structural features

Individualised, perioperative open-lung ventilation strategy during one-lung ventilation (iPROVE-OLV): a multicentre, randomised, controlled clinical trial

Background: It is uncertain whether individualisation of the perioperative open-lung approach (OLA) to ventilation reduces postoperative pulmonary complications in patients undergoing lung resection. We compared a perioperative individualised OLA (iOLA) ventilation strategy with standard lung-protective ventilation in patients undergoing thoracic surgery with one-lung ventilation. Methods: This multicentre, randomised controlled trial enrolled patients scheduled for open or video-assisted thoracic surgery using one-lung ventilation in 25 participating hospitals in Spain, Italy, Turkey, Egypt, and Ecuador. Eligible adult patients (age ≥18 years) were randomly assigned to receive iOLA or standard lung-protective ventilation. Eligible patients (stratified by centre) were randomly assigned online by local principal investigators, with an allocation ratio of 1:1. Treatment with iOLA included an alveolar recruitment manoeuvre to 40 cm H2O of end-inspiratory pressure followed by individualised positive end-expiratory pressure (PEEP) titrated to best respiratory system compliance, and individualised postoperative respiratory support with high-flow oxygen therapy. Participants allocated to standard lung-protective ventilation received combined intraoperative 4 cm H2O of PEEP and postoperative conventional oxygen therapy. The primary outcome was a composite of severe postoperative pulmonary complications within the first 7 postoperative days, including atelectasis requiring bronchoscopy, severe respiratory failure, contralateral pneumothorax, early extubation failure (rescue with continuous positive airway pressure, non-invasive ventilation, invasive mechanical ventilation, or reintubation), acute respiratory distress syndrome, pulmonary infection, bronchopleural fistula, and pleural empyema. Due to trial setting, data obtained in the operating and postoperative rooms for routine monitoring were not blinded. At 24 h, data were acquired by an investigator blinded to group allocation. All analyses were performed on an intention-to-treat basis. This trial is registered with ClinicalTrials.gov, NCT03182062, and is complete. Findings: Between Sept 11, 2018, and June 14, 2022, we enrolled 1380 patients, of whom 1308 eligible patients (670 [434 male, 233 female, and three with missing data] assigned to iOLA and 638 [395 male, 237 female, and six with missing data] to standard lung-protective ventilation) were included in the final analysis. The proportion of patients with the composite outcome of severe postoperative pulmonary complications within the first 7 postoperative days was lower in the iOLA group compared with the standard lung-protective ventilation group (40 [6%] vs 97 [15%], relative risk 0·39 [95% CI 0·28 to 0·56]), with an absolute risk difference of -9·23 (95% CI -12·55 to -5·92). Recruitment manoeuvre-related adverse events were reported in five patients. Interpretation: Among patients subjected to lung resection under one-lung ventilation, iOLA was associated with a reduced risk of severe postoperative pulmonary complications when compared with conventional lung-protective ventilation. Funding: Instituto de Salud Carlos III and the European Regional Development Funds