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The formation of perylene films with improved crystalline quality was achieved by using nanoscale ionic liquids under vacuum as a media for increased control of the nucleation and subsequent growth of perylene crystals.

Energetic analyses based on homodesmotic reactions show a surprising ability of crowded biphenyls to achieve significant stabilization through intramolecular dispersive interactions, which is underestimated even by state-of-the-art DFT calculations.

Chlorins are highly interesting compounds due to their spectroscopic properties in both UV-Vis and NIR regions. Upon coordination to a metal ion, the corresponding metallochlorins exhibit more valuable physicochemical properties that enable a broader range of applications, such as in photodynamic therapy (PDT), water splitting catalysis, optical sensor devices and dye-sensitized solar cells. Synthetic chemistry has been in a continuous quest to fulfil most green chemistry requirements through the development of efficient reactions. Being a heating process that does not depend on heat transfer to the reaction medium, ohmic heating accomplishes the mentioned requirements and allows a fast and uniform heating regime thanks to the ionic conductivity of the reaction medium. Herein, we report the metallation of pyrrolidine- and isoxazolidine-fused chlorins with Zn(II), Cu(II) and Pd(II) salts by ohmic heating, using non-toxic aqueous solutions, and their corresponding physico-chemical characterization. All pyrrolidine-fused chlorins showed higher yields, when compared with isoxazolidine ones. From the thermogravimetric analysis performed it is possible to infer that the metal enhances the steadiness of the macrocycle, making it easier to cause the thermal decomposition of the pyrrolidine- and isoxazolidine-fused chlorins. The Zn(II) complexes showed high absorption in the NIR spectral region, a low fluorescence quantum yield and a short excited singlet state, which indicate the high efficiency of intersystem crossing to the triplet state, making them very promising candidates as photosensitizers for PDT.

Typical distal symptoms in anti-myelin-associated glycoprotein (anti-MAG) neuropathy are believed to be due to the binding of immunoglobulin M to distal nerve terminals. We describe the case of a 56-year-old man diagnosed with immunoglobulin M anti-MAG neuropathy in the setting of Waldenström macroglobulinemia, which developed acute neurological worsening presenting as cauda equina syndrome. Lumbosacral magnetic resonance imaging revealed enlarged nerve roots with diffuse heterogeneous gadolinium enhancement. Treatment with steroids resulted in substantial clinical improvement. Increased recognition of atypical presentations may lead to improved characterization of anti-MAG neuropathy as a more widespread disease.

In this study, a homogeneous thin film growth of pentacene onto indium tin oxide (ITO) coated glass surfaces is explored using a high-resolution and reproducible vapor deposition methodology. Moreover, vacuum thermal evaporation of ionic liquids (ILs) ([C2 C1 im][NTf2 ] and [C2 C1 im][OTF]) onto ITO, gold/palladium (AuPd) and pentacene surfaces were performed. A greater wettability behavior of ILs is observed for surfaces containing AuPd. Sequential and simultaneous depositions of ILs and pentacene were explored. Simultaneous depositions lead to the formation of nanocomposites films, consisting of IL micro- and nanodroplets covered by pentacene layers. Plasma surface treatment was used to induce the ILs droplets coalescence and explore the dynamics and phase separation of the nanocomposites. The [C2 C1 im][OTF] droplets were found to be completely covered with pentacene, which suggests a great affinity between cation-anion pairs and the aromatic moiety. Pentacene films and their nanocomposites with ILs exhibit a typical optical band gap of Egap =1.77 eV, indicating that the nanocomposite phase domains are large enough to behavior as the bulk.

This work aims to provide reliable heat capacities for ethylene glycol and selected oligo(ethylene glycol)s (diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and h...

The chain-length dependence of the thermodynamic properties associated with the solid-to-liquid, liquid-to-gas, and solid-to-gas phase equilibria is analyzed and discussed for homologous families o...

This investigation concerns about of fatigue behavior under controlled loading and under strain control for hybrid specimens with parts produced with conventional processes in steel AISI H13 and the stainless steel AISI 420 and the rest part produced by laser powder bed fusion in AISI 18Ni300 steel. The controlled loading tests were performed in constant and variable amplitude. Fatigue failure of hybrid samples occurs mostly in laser-melted parts, initiated around the surface, in many cases with multi-nucleation and propagated predominantly between the deposited layers. Fatigue strength of hybrid parts, tested under displacement control is similar, but for specimens tested under load control the fatigue strength the fatigue strength of hybrid specimens is progressively lesser than laser powder bed fusion samples. Despite a tendency to obtain conservative predictions, Miner’s law predicts reasonably the fatigue lives under block loadings. The interface between materials presented an excellent joining and fatigue strength because the fatigue failure of hybrid samples occurred mostly in laser melted parts out of the interface.

The thermodynamic properties and band gap energies were evaluated for six ortho- and peri-fused polycyclic aromatic hydrocarbons (PAHs): triphenylene; benzo[a]pyrene; benzo[e]pyrene; perylene; benz...

Introduction Point mutations in the Peripheral Myelin Protein 22 (PMP22) gene comprise less than 5% of the Charcot-Marie-Tooth (CMT) type 1 cases, and individualize either the CMT 1E subtype, or Hereditary Neuropathy with Liability to Pressure Palsy. The phenotype of CMT 1E presents with a severe early-onset polyneuropathy associated with deafness, although the clinical spectrum is broad. Case report We describe a novel PMP22 gene point mutation (c.84G>T;p.(Trp28Cys)) in three patients of a Portuguese family with variable phenotypes, ranging from asymptomatic to mild complaints of distal limb numbness and gait difficulties, with the age of onset of symptoms ranging from mid-twenties to late-sixties, and no associated disability. In all affected patients, there was evidence of diffuse demyelinating sensorimotor polyneuropathy. Hearing loss does not seem to be associated with this variant, albeit neuropathic pain was reported. Conclusions These findings suggest that this particular point mutation in the PMP22 gene is associated with a mild phenotype, further emphasizing that there are still unknown mechanisms (genetic and/or epigenetic) that may play a role in the clinical spectrum of CMT1E patients. Next generation sequencing panels including commonly mutated genes in CMT should be considered in CMT1 cases negative for PMP22 gene duplication.

Due to the continuous improvement of technology, nearly all the companies and entrepreneurs explore its benefits, to increase their income and enhance their businesses, reducing costs and work time [1]. Thus, technology is also starting to take root in less developed countries, helping with their growth in several areas. This project strives to enhance those countries' legislation, by presenting tools that improve all the inherent mechanics, by following specific requirements that must integrate such systems. The platform combines many elements that work towards several needs, depending on the internal business logic and their parliamentary workflows. Since the solution aims to serve different parliaments, the focus of the implemented project will be on building dynamic components that can adapt to different scenarios.

In this study, a homogeneous thin film growth of pentacene onto indium tin oxide (ITO) coated glass surfaces is explored using a high-resolution and reproducible vapor deposition methodology. Moreover, vacuum thermal evaporation of ionic liquids (ILs) ([C

This work presents an extended study of the thermal behavior of the alkyl and dialkylpyridinium derivatives of the bis(trifluoromethylsulfonyl)imide ionic liquid series, using high resolution power...

Oxidative treatment of Multi-Walled Carbon Nanotubes (MWCNT’s) was done by chemical functionalization by using the mixture acid, which is a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3). Functionalization was governed by four parameters namely mixture acid concentration, temperature(T), time of heating(t) and the amount of MWCNTs used. After functionalization, functionalized MWCNT’s were then diluted in dimethylformamide (DMF) to analyse the percentage of soluble MWCNT’s. Also, by increasing the time of functionalization, it was observed that overall yield decreases but the percentage of functionalized product inside the yield quantity remains the same. Material characterization was also carried out at several steps to validate this theory. Chemical functionalization of MWCNT’s is generally significant for the manufacturing of polymer-based nanocomposites. Oxidative treatment enhances the dispersion and interfacial bonding within the epoxy matrix. In this research work, a bio-based epoxy resin was selected for the manufacturing of nanocomposite samples with various concentrations of pristine and functionalized MWCNTs. Mechanical and electrical characterization was finally carried out to increase the knowledge on the interaction of MWCNT’s with the selected green epoxy matrix system and their influence on the original properties of the resin.

The principle of operation, concepts and recent developments of the Knudsen effusion methodology for the vapour pressure measurement of ionic liquids and other low volatile liquids and solids are presented. A new version of a Knudsen effusion apparatus, coupled with a quartz crystal microbalance, which is used for a reliable measurement of the mass flow from a Knudsen effusion cell, is described in detail. In the new system, designed and optimized for the vapour pressure measurement of ionic liquids, it is possible to measure the vapour pressure of small samples using very short effusion time over a wide temperature range. This apparatus allows the vapour pressure measurements using step-temperature and continuous-temperature modes that have the advantage of reducing the measurement time interval and minimize the effect of a sample degradation. A significant number of improvements on the performance and capability for the vapour pressure measurements of ionic liquids has been implemented: in situ temperature control of the vacuum chamber for a better stability of background signal; a new design of a stainless steel effusion cell to decrease the reactivity and sample decomposition; dual temperature control ensuring a positive temperature gradient between bottom and top of the cell in order to avoid the ionic liquids condensation on the effusion cell lid and significantly improved stability of the time frequency derivative at high temperatures; Installation and test of a mass flow tube, on the top of the outlet of the cell lid oven block in order to increase the mass sensitivity coefficient of QCM. The tests and benchmarking concerning the measurement of vapour pressures of ionic liquids performed with [C2mim][NTf2] indicate that the described Knudsen effusion apparatus and methodology is able to produce reproducible and reliable experimental vapour pressure data with an accuracy and quality similar than the achieved in the measurements with low volatile solids. The effect of the improvements on the performance of the Knudsen effusion apparatus was tested and evaluated by the comparison of the vapour pressure results of 1,3,5-triphenylbenzene and 1-ethyl-3-methylimidazolium with the available literature data.

Seismic design of concentrically X-braced steel frames to Eurocode 8 entails several difficulties to practitioners, often resulting in excessively heavy structural solutions. The main objective of the research presented in this paper is to propose modifications to the existing provisions of the code aiming to achieve more efficient designs. A number of possible amendments to the European seismic code are examined, concerning the non-dimensional slenderness parameter and the homogenous dissipative behaviour criterion. It is found that the relaxation of the design criteria leads to identical frame behaviour in comparison to frames fully designed to Eurocode 8. This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Earthquake Engineering on 16/10/2018, available online: http://www.tandfonline.com/10.1080/13632469.2018.1528912.

A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium tin oxide, fluorine-doped tin oxide, and TiO2 surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films.

Herein, we present experimental evidence that protic ionic liquids (PILs), derived from 1 : 1 liquid mixtures of the organic superbases 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with carboxylic acids, form azeotropic mixtures with acid/base molar fractions different from 1 : 1. The ability of the carboxylic acids to form strong hydrogen bonds with the PIL ion pair leads to an azeotropic composition richer in the acid component. The results show that the azeotropic composition is ruled by the extent of acid-base equilibrium and the relative volatility of the neutral species in the PIL medium. The PILs show marked negative deviations from Raoult's Law with the stronger superbase (DBU) leading to an azeotropic composition closer to the equimolar 1 : 1 ratio.

Aromatic diamines and naphthyl-substituted benzidines (BDB, TPB, TPD, NPB, alpha-NPD, beta-NPB, TNB) are listed as one of the best series available of hole transport materials used as thin films in organic electronics (OLEDs, OPVs). High-quality, homogeneous and compact thin films (ae 300 nm of thickness) of this compound series were prepared by a physical vapor deposition procedure. SEM and XRD characterizations evidence the amorphous nature of the thin films of NPB, alpha-NPD, beta-NPB and TNB, prepared onto ITO and gold surfaces by a controlling mass flow rate. The semiconducting behavior of this class of pi-conjugated materials was investigated through UV-vis characterization by the determination of optical band gaps (ae 3 eV). According to DSC, SEM and XRD analyses, the materials evidenced an amorphous structure and high thermal stability in the glassy state. Analyzing the melting properties, the ratio T (g)/T (m) = 2/3 was observed for TPB and NPB, which have a higher molecular symmetry, while T (g)/T (m) = 3/4 was observed for the asymmetric beta-NPB and TPD. The first accurate measurements of the vapor pressures and thermodynamic properties of phase transition were obtained for the most common hole transport material (NPB) in OLEDs. The relative stability of the crystalline phases of the diamine derivatives (BDB, TPB, NPB) was found to be enthalpically driven, increasing linearly with the molar volume of the compound.

Anthocyanins are potential food colorants due to their color, low toxicity and biological properties. However, the low chemical stability of anthocyanins has limited their use. In this work, the thermal stability of cyanidin-3-O-glucoside (cy3glc) (major blackberry anthocyanin) and blackberry purees through molecular inclusion with β-cyclodextrin (β-CD) was assessed. Complexation with β-CD showed a thermal stabilization of cy3glc, resulting on a decrease of the degradation rate constant (k) and in several alterations in the cy3glc-β-CD DSC thermogram. To assess the bioaccessibility of blackberry anthocyanins, the stability of blackberry purees through simulated in vitro digestion was also studied. Despite the rapid degradation of anthocyanins observed within the first minutes of simulated intestinal digestion, complexation with β-CD allowed anthocyanins degradation to be slowed down. The results obtained demonstrate the ability of β-CD to increase blackberry anthocyanins thermal stability and also to decrease the rate of degradation of these pigments under simulated gastrointestinal conditions.

The heat capacity and thermal behavior trend along the 1-alkyl-3-methylimidazolium hexafluorophosphate [C n C 1 im][PF 6 ] (with n = 2–10, 12) ionic liquids series, is used to explore the effect of the alkyl chain length in the nanostructuration. The heat capacities of the studied ILs were measured with an uncertainty better than ± 0.15% and are in excellent agreement with the available data in the literature. An odd-even effect for the specific and volumic heat capacities of the [C n C 1 im][PF 6 ] series was found. The observed odd-even effect in the liquid heat capacity was rationalized considering the preferential orientation of the terminal CH 3 group. The higher specific/volumic heat capacities shown for the [C 6 C 1 im][PF 6 ] and [C 8 C 1 im][PF 6 ] are an indication of an additional conformational disorder increase in the liquid phase that could be related with a weaker alkyl chain interdigitation capability of the even number chain ILs. The melting temperatures and consequent ∆ s l H m o and ∆ s l S m o trend along the alkyl series present a V-shape profile that is explained based on the analysis of the balance between the initial decrease of the electrostatic interaction potential and the increase of the van der Waals interactions with the increasing size of the alkyl side chain of the cation. The inhibition of crystallization for intermediate alkyl chain size (from [C 5 C 1 im][PF 6 ] to [C 8 C 1 im][PF 6 ]) seems to arise from the overlapping of the hypothetical cold crystallization temperature by the melting temperature. Above the critical alkyl size, CAS, a regular increase in the entropy and enthalpy profiles presents a similar shape than the observed in other alkane series and is a strong support of the intensification of the ILs nanostructuration.

A systematic isobaric vapor-liquid equilibrium (VLE) study of seven binary mixtures of 1-butyl-3-methylimidazolium chloride, [C4C1im][Cl], and methanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, tert-butanol (2-methylpropan-2-ol), iso-butanol (2-methylpropan-1-ol) and pentan-1-ol, was carried out at three different system pressures (0.1, 0.07 and 0.05 MPa). Activity coefficients were estimated from the boiling temperatures of the binary mixtures. soft-SAFT equation of state was used to describe the experimental VLE data and all together, allowed to infer and understand the effect of the alcohol alkyl chain length and structural isomerism on the molecular interactions between the IL and the alcohols.

The ohmic heating also known as direct Joule heating, is an advanced thermal processing method, mainly used in the food industry to rapidly increase the temperature for either cooking or sterilization purposes. Its use in organic synthesis, in the heating of chemical reactors, is an emerging method that shows great potential, the development of which has started recently. This Concept article focuses on the use of ohmic heating as a new tool for organic synthesis. It presents the fundamentals of ohmic heating and makes a qualitative and quantitative comparison with other common heating methods. A brief description of the ohmic reactor prototype in operation is presented as well as recent examples of its use in organic synthesis at laboratory scale, thus showing the current state of the research. The advantages and limitations of this heating method, as well as its main current applications are also discussed. Finally, the prospects and potential implications of ohmic heating in future research in chemical synthesis are proposed.

The impact of structural differentiation between phenylcarbazoles (PhC, mCP, CBP, TCB) and phenylamines (TPA, BDB, TPB, TDAB) on the phase equilibria, optical spectrum, band gap, and thin-film morphology is evaluated and discussed. The carbazolyl units lead to a lower electronic conjugation contributing to a wide band gap when compared with the diphenylamine analogs. The fusion and sublimation equilibria indicate that entropic contribution is the key factor for the distinguished melting behavior and solid-phase volatility between phenylcarbazole derivatives and phenylamine analogs. The molecular differentiation between the two classes of compounds is not reflected in the crystal packing and intermolecular interactions. However, compared with the diphenylamino groups, the incorporation of carbazolyl moieties contributes to a less flexible molecule. Moreover, the results evidence that intermolecular bonding disruption along the fusion transition is more extensive for phenylamine derivatives. Due to the asymmetric nonplanar structure, mCP is characterized by a ratio of {Tg/Tm ≈ 3/4} while the more symmetric CBP and TCB molecules display ratios closer to {Tg/Tm ≈ 2/3}. Vapor-deposited thin films of mCP, CBP, and TCB are amorphous and their morphology is highly dependent on the substrate roughness. The lower flexibility of nonplanar phenylcarbazoles induces the formation of a glassy state due to the harder packing mechanism leading to the lower ability of the crystallization process.

This work presents a new Knudsen effusion apparatus employing continuous monitoring of sample deposition using a quartz-crystal microbalance sensor with internal calibration by gravimetric determination of the sample mass loss. The apparatus was tested with anthracene and 1,3,5-triphenylbenzene and subsequently used for the study of sublimation behavior of several proteinogenic amino acids. Their low volatility and thermal instability strongly limit possibilities of studying their sublimation behavior and available literature data. The results presented in this work are unique in their temperature range and low uncertainty required for benchmarking theoretical studies of sublimation behavior of molecular crystals. The possibility of dimerization in the gas phase that would invalidate the effusion experiments is addressed and disproved by theoretical calculations. The enthalpy of sublimation of each amino acid is analyzed based on the contributions in two hypothetical sublimation paths involving the proton transfer in the solid and in the gas phase.

Highlights • Mycobacterium chelonae infection may occur in chronic treatment with steroids. • The most common presentation form is disseminated cutaneous infection. • First-line treatment should be a triple antibiotics association for at least 4 months. • Macrolides, fluoroquinolones and other antibiotics may exacerbate myasthenia gravis., Mycobacterium chelonae can cause chronic skin, soft-tissue or bone infections. and is often associated with the immunocompromised state.We describe a case of a 58-year-old male patient with myasthenia gravis, chronically immunosuppressed, with a four month progression of growing erythematous, nodular and hard cutaneous lesions in the left forearm, leg and foot. He was receiving immunoglobulin every four weeks (2 g/kg) and prednisolone 25 mg/day and had an important previous history of several opportunistic infections while he was receiving corticosteroids. Histopathological examination of a biopsy showed acid-fast bacilli and tissue culture identified a Mycobacterium spp. within seven days of incubation, with Mycobacterium chelonae being identified by polymerase chain reaction assay. Antimicrobial susceptibility testing was performed showing no resistance and the patient was successfully treated during four months with ciprofloxacin, clarithromycin and trimethoprim-sulfamethoxazole with regression of the lesions, leaving some hyperpigmentation scars and without unbalancing his neurological disease. Patients with myasthenia gravis should be closely monitored because first line treatments for M. chelonae infection may be associated with myasthenic crisis.

Selective Laser Melting (SLM) is an additive manufacturing technology, ideal for the production of complex-shaped components. Design against fatigue is fundamental in the presence of cyclic loads, particularly for these materials which typically have significant porosity, high surface roughness and residual stresses. The main objective here is to study fatigue crack growth (FCG) in the 18Ni300 steel obtained by SLM. Typical da/dN-&Delta, K curves were obtained in C(T) specimens, indicating that cyclic plastic deformation may be the controlling mechanism. A complementary analysis, based on plastic CTOD range, showed a relatively low level of crack tip plastic deformation, and consequently a reduced level of plasticity induced crack closure. The curve da/dN versus plastic CTOD range is clearly above the curves for other materials.

A series of pyridyl analogues of rosamines was prepared by employing two methodologies: (i) the conventional-heating condensation of a pyridinecarboxaldehyde with 3-(diethylamino)phenol in propionic acid, and (ii) the novel ohmic-heating assisted condensation under "on water" conditions, followed by oxidation. The 4-pyridyl substituted rosamine was further converted into the N-methylpyridinium derivative through N-alkylation using methyl iodide. The influence of the position and cationization of the nitrogen atom of the pyridyl ring in the physicochemical properties of fluorophores was investigated by 1 H, 13 C, 15 N NMR spectral analysis, UV/Vis and fluorescence spectroscopy, single-crystal X-ray diffraction (4-pyridyl and N-methylpyridinium derivatives) and thermal-behavior analysis. Curiously, for ethanolic solutions of 4-pyridyl and N-methylpyridinium derivatives an extinction of color and fluorescence over time was observed. This phenomenon was further studied and the data revealed that it is the result of nucleophilic addition of ethoxide ion to the central 9-position of the xanthene. The kinetics of the process is slower for the 4-pyridyl rosamine, which emphasizes the importance of the charge in the N-methylpyridinium analogue in the reactivity of the molecule towards a nucleophile agent. This phenomenon is reversible, meaning that the compounds can be rapidly recovered by decreasing the pH, opening new avenues in the sensing applications of this class of rosamines.

International audience; The volatility and cohesive energy of fluorinated ionic liquids, FILs, was evaluated and used to explored and understand the effect of fluorination of the ILs cations and anions on the cohesive interaction and structuration. For this, the vapour pressures at different temperatures using a Knudsen effusion apparatus coupled with a quartz crystal microbalance were measured for three fluorinated imidazolium-based ionic liquids. The enthalpies and entropies of vaporization were derived from the temperature dependence of the vapour pressures. The degree of fluorination of the ions leads to an increase of the IL volatility following the order: [C8mim][NTf2]

A comprehensive thermodynamic study of the whole ortho-polyphenylbenzenes series from biphenyl (n = 1) to hexaphenylbenzene (n = 6) is presented. Combustion calorimetry and phase equilibria measurements for 1,2,3,4-tetraphenylbenzene (n = 4) and pentaphenylbenzene (n = 5) together with literature data were used to understand and quantify the constraint effect of ortho-substitution on the molecular energetics and phase stability of polyaromatic compounds. All of the derived thermodynamic properties (enthalpy of sublimation, entropy of sublimation, and gas phase molecular energetics) show a marked trend shift at n = 4 to 5, which is related to the change of the degree of molecular flexibility after 1,2,3,4-tetraphenylbenzene (n = 4). The greater intramolecular constraint in the more crowded members of the series (n = 5 and 6) leads to a significant change in the molecular properties and cohesive energy. The trend shift in the molecular properties is related with the decrease in molecular flexibility, which leads to lower molecular entropy and destabilization of the intramolecular interaction potential due to the increased hindrance in a confined molecular space.

The molecular and supramolecular structure and energetics of tetracene and rubrene were investigated by a combined experimental and theoretical study. Accurate equilibrium vapour pressures at various temperatures were measured for both compounds. For rubrene the energetic analysis evidences lower crystal packing efficiency, strong molecular destabilization and confirms the non-planar twisted equilibrium structure in the gas phase. The results also indicate that phenyl internal rotation in rubrene is highly hindered. The intra- and intermolecular interactions in crystal tetracene and rubrene were evaluated by computational methods. The representative stacked dimer of the tetracene...tetracene interaction in rubrene has lower ionization energy than the one modelling the same interaction in tetracene, due to stronger cation...pi interactions in the cation-radical of rubrene. Charge distribution in the cation dimer is symmetrical in rubrene, whereas in tetracene it is largely localized on the C-H center dot center dot center dot pi donor partner of the herringbone dimer. These findings highlight the impact of cation...pi interactions on the semiconducting properties of OSCs.

The synthesis and reactivity of 2-[(1E,3E)-4-arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones as dienes in Diels–Alder (DA) reactions with several electron-poor and electron-rich dienophiles under microwave irradiation was studied. The optimized reaction conditions were achieved with N-methylmaleimide as the dienophile and Sc(OTf)3 (OTf = triflate) as a Lewis acid under microwave-assisted and solvent-free conditions. The Lewis acid improved the reaction yields as it prevented the adducts obtained from undergoing a second DA reaction; thus, the formation of a bisadduct was avoided. The α,β:γ,δ-diene of the starting chromones was the most reactive, and the computational results confirmed the experimental findings. Theoretical calculations also provided a rationale for the unexpected lack of reactivity shown by some dienophiles. The adducts prepared were dehydrogenated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); however, the aza adducts were sensitive to the highly energetic reaction conditions necessary for the aromatization.