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In this work, electrochromic devices were prepared using the redox couple ethyl viologen diperchlorate and 1,1'-diethyl ferrocene in propylene carbonate as an aprotic solvent to facilitate ions separation and diffusion inside the devices. Electrochromic devices were made using electrochromic gel mixtures at the concentrations of 55%, 60% and 65% with respect to the bisphenol A polymer. In particular, two sets of gels were made: one set contained the bisphenol A not-polymerized while and the second one contained the polymerized polymer. Different techniques, such as cyclic voltammetry, UV-vis-NIR, and Raman spectroscopy, were used to study such systems to understand the differences in terms of performances between the different sets of electrochromic devices. Cyclic voltammetry confirmed that the oxidation process of the 1,1'-diethyl ferrocene and the reduction of the ethyl viologen diperchlorate occurred at about 0.4 V. Interesting variations in the transmittances were found between the two groups of samples. The best values of CE were provided by the electrochromic devices based on the polymerized electrochromic gel mixture at a concentration of 60% (EM 60 ). The EM 60 device result was CE = 92.82 C/cm 2 in the visible region and CE = 80.38 C/cm 2 in the near-infrared region, confirming that these devices can be used for energy-saving applications. A structural characterization of the materials used in the two sets of electrochromic devices was made using Raman spectroscopy, and the analysis supports the electrochemical models used to explain the processes involved during operation of the electrochromic systems.

Vitamin D deficiency is a common deficiency worldwide, particularly among women of reproductive age. During pregnancy, it increases the risk of immune-related diseases in offspring later in life. However, how the body remembers exposure to an adverse environment during development is poorly understood. Herein, we explore the effects of prenatal vitamin D deficiency on immune cell proportions in offspring using vitamin D deficient mice established by dietary manipulation. We found that prenatal vitamin D deficiency alters immune cell proportions in offspring by changing the transcriptional properties of genes downstream of vitamin D receptor signaling in hematopoietic stem and progenitor cells of both the fetus and adults. Moreover, further investigations of the associations between maternal vitamin D levels and cord blood immune cell profiles from 75 healthy pregnant women and their term offspring also confirm that maternal vitamin D levels in the second trimester significantly affect immune cell proportions in the offspring. These findings imply that the differentiation properties of hematopoiesis act as long-term memories of prenatal vitamin D deficiency exposure in later life., (© 2024. The Author(s).)

We report a semiconducting triindole-based discotic liquid crystal ( TRISMe ) functionalized with six p -methylthiophenyl groups at its periphery. While initially a crystalline solid at room temperature, TRISMe transitions to a columnar hexagonal mesophase upon heating and retains this supramolecular organization upon subsequent cooling, despite having only three flexible alkyl chains attached to the core's nitrogens. The incorporation of methylthio groups effectively hinders tight molecular packing, stabilizing the columnar arrangement of this disk-shaped molecule. Single crystal analysis confirmed the high tendency of this compound to organize into a columnar architecture and the role played by the methylthio groups in reinforcing such structure. The mesomorphic behavior of TRISMe provides an opportunity for processing from its molten state. Notably, our research reveals significant differences in charge transport depending on the processing method, whether solution drop-casting or melt-based. TRISMe shows hole mobility values averaging 3 × 10 -1 cm 2 V -1 s -1 when incorporated in diode-type devices from the isotropic melt and annealed at the mesophase temperature, estimated by SCLC (space-charge-limited current) measurements. However, when integrated into solution-processed organic field-effect transistors (OFETs), crystalline TRISMe exhibits a hole mobility of 3 × 10 -4 cm 2 V -1 s -1 . The observed differences can be attributed to a beneficial supramolecular assembly achieved in the mesophase in spite of its lower order. These results emphasize the material's potential for applications in easy-to-process electronic devices and highlight the potential of methylthio moieties in promoting columnar mesophases., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Organic semiconductors with well-defined architectures pose a suitable alternative to amorphous silicon-based inorganic semiconductors. Encouraged by the development of organic semiconductors based on columnar liquid crystals, herein, we report on a family of C 3 -symmetric star-shaped mesogens based on triphenylamine (TPA), a functional unit with strong electron donor character. Highly stable columnar phases with high hole mobility values were obtained out of this nonplanar functional unit, and this was achieved by using flexible amide spacers to join the TPA units to a tris(triazolyl)triazine (T) star-shaped core, allowing the formation of intermolecular hydrogen bonds. The presence of hydrogen bonds results in a stabilization of the columnar architectures either in bulk or in the presence of solvents by reinforcing π-stacking and van der Waals interactions, as deduced by Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) studies. Furthermore, the introduction of a stereogenic center in the flexible spacer prompts the formation of chiral aggregates in the liquid crystal state and in the organogel formed in 1-octanol, as demonstrated by circular dichroism spectroscopy., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Objectives: We validated a screening protocol in which thoracic ultrasound (TUS) acts as a first-line complementary imaging technique in selecting patients which may deserve a second-line low-dose high resolution computed tomography (HRCT) scan among a population of asymptomatic high-risk subjects for interstitial lung abnormalities (ILA) and lung cancer. Due to heavy environmental pollution burden, the district Tamburi of Taranto has been chosen as "case study" for this purpose., Methods: From July 2018 to October 2020, 677 patients aged between 45 and 65 year and who had been living in the Tamburi district of Taranto for at least 10 years were included in the study. After demographic, clinical and risk factor exposition data were collected, each participant underwent a complete TUS examination. These subjects were then asked to know if they agreed to perform a second-level examination by low-dose HRCT scan., Results: On a total of 167 subjects (24.7%) who agreed to undergo a second-level HRCT, 85 patients (50.9%) actually showed pleuro-pulmonary abnormalities. Interstitial abnormalities were detected in a total of 36 patients on HRCT scan. In particular, 34 participants presented subpleural ILAs, that were classified in the fibrotic subtype in 7 cases. The remaining 2 patients showed non-subpleural interstitial abnormalities. Subpleural nodules were observed in 46 patients. TUS showed an overall diagnostic accuracy of 88.6% in detecting pleuro-pulmonary abnormalities in comparison with HRCT scan, with a sensitivity of 95.3%, a specificity of 81.7%, a positive predictive value of 84.4% and a negative predictive value of 94.4%. The matched evaluation of specific pulmonary abnormalities on HRTC scan (i.e., interstitial abnormalities or pulmonary nodules) with determinate sonographic findings revealed a reduction in both TUS sensibility and specificity. Focusing TUS evaluation on the assessment of interstitial abnormalities, a thickened pleural line showed a sensitivity of 63.9% and a specificity of 69.5%, hypoechoic striae showed a sensitivity of 38.9% and a specificity of 90.1% and subpleural nodules showed a sensitivity of 58.3% and a specificity of 77.1%. Regarding to the assessment of subpleural nodules, TUS showed a sensitivity of 60.9% and a specificity of 81.0%. However, the combined employment of TUS examination and HRCT scans allowed to identify 34 patients with early subpleural ILA and to detect three suspicious pulmonary nodules (of which two were intraparenchymal and one was a large subpleural mass), which revealed to be lung cancers on further investigations., Conclusion: A first-line TUS examination might aid the identification of subjects highly exposed to environmental pollution, who could benefit of a second-line low-dose HRCT scan to find early interstitial lung diseases as well as lung cancer., Protocol Registration Code: PLEURO-SCREENING-V1.0_15 Feb, 17., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Quarato, Dama, Maggi, Feragalli, Borelli, Del Colle, Taurchini, Maiello, De Cosmo, Lacedonia, Barbaro, Carpagnano, Scioscia, Graziano, Termine, Frongillo, Santamaria, Venuti, Grimaldi, Notarangelo, Saponara, Copetti, Colangelo, Cuttano, Macrodimitris, Mazzarelli, Talia, Mirijello, Pazienza, Perna, Simeone, Vergara, Varriale, Carella, Bianchi and Sperandeo.)

To gain insights into the molecular interactions of an intracellular pathogen and its host cell, we studied the gene expression and chromatin states of human fibroblasts infected with the Apicomplexan parasite Toxoplasma gondii. We show a striking activation of host cell genes that regulate a number of cellular processes, some of which are protective of the host cell, others likely to be advantageous to the pathogen. The simultaneous capture of host and parasite genomic information allowed us to gain insights into the regulation of the T. gondii genome. We show how chromatin accessibility and transcriptional profiling together permit novel annotation of the parasite's genome, including more accurate mapping of known genes and the identification of new genes and cis-regulatory elements. Motif analysis reveals not only the known T. gondii AP2 transcription factor-binding site but also a previously-undiscovered candidate TATA box-containing motif at one-quarter of promoters. By inferring the transcription factor and upstream cell signaling responses involved in the host cell, we can use genomic information to gain insights into T. gondii's perturbation of host cell physiology. Our resulting model builds on previously-described human host cell signalling responses to T. gondii infection, linked to induction of specific transcription factors, some of which appear to be solely protective of the host cell, others of which appear to be co-opted by the pathogen to enhance its own survival., Competing Interests: The authors have declared that no competing interests exist.

Vitamin D, a fat-soluble vitamin, plays a critical role in calcium homeostasis, the immune system, and normal development. Many epidemiological cohort studies globally have found high prevalence rates of vitamin D deficiency and insufficiency, recognized as an important health issue that needs to be solved. In particular, reproductive age and pregnant women low in vitamin D status may confer risks of diseases like obesity on their offspring. While observational studies have suggested associations between prenatal vitamin D deficiency and metabolic phenotypes in offspring, not yet determined is whether prenatal vitamin D deficiency permanently alters the development of the liver, a major metabolic organ. We tested the histopathology and the transcriptomic profiles of livers from male C57BL/6J mice exposed to prenatal vitamin D deficiency through a maternal dietary intervention model. We found that prenatal vitamin D deficiency increases the prevalence of histopathological changes in the liver, and alters its gene expression profile. Cell subtype proportion analysis showed that the liver of prenatal vitamin D deficiency alters non-parenchymal cells of the liver, specifically macrophages, a subset of endothelial cells, and dendritic cells. Our results indicate the long-term memory of prenatal vitamin D deficiency exposure in the adult liver, a potential contributor to offspring health risks., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lundy, Greally, Essilfie-Bondzie, Olivier, Doña-Termine, Greally and Suzuki.)

We have synthetized two classes of dibenzofulvene-arylamino derivatives with an H-shape design, for a total of six different molecules. The molecular structures consist of two D-A-D units connected by a thiophene or bitiophene bridge, using diarylamino substituents as donor groups anchored to the 2,7- (Group A) and 3,6- (Group B) positions of the dibenzofulvene backbone. The donor units and the thiophene or bithiophene bridges were used as chemico-structural tools to modulate electro-optical and morphological-electrical properties. A combination of experiments, such as absorption measurements (UV-Vis spectroscopy), cyclic voltammetry, ellipsometry, Raman, atomic force microscopy, TD-DFT calculation and hole-mobility measurements, were carried out on the synthesized small organic molecules to investigate the differences between the two classes and therefore understand the relevance of the molecular design of the various properties. We found that the anchoring position on dibenzofulvene plays a crucial key for fine-tuning the optical, structural, and morphological properties of molecules. In particular, molecules with substituents in 2,7 positions (Group A) showed a lower structural disorder, a larger molecular planarity, and a lower roughness.

The synthesis and the electrochemical, photophysical, structural, and photoconductive properties of three new heteroleptic Pd(II) complexes with various 3',5'- disubstituted-2-(2'-pyridil) pyrroles H(N^N) as coordinated ligands are reported. The coordination of the metal center was completed by a functionalized Schiff base H(O^N) used as an ancillary ligand. The [(N^N)Pd(O^N)] complexes showed highly interesting photoconductive properties which have been correlated to their electronic and molecular structures. Theoretical density functional theory (DFT) and time-dependent DFT calculations were performed, and the results were confronted with the organization in crystalline phase, allowing to point out that the photoconductive properties are mainly a consequence of an efficient intramolecular ligand-to-metal charge transfer, combined to the proximity between the central metal and the donor moieties in the solid-state molecular stacks. The reported results confirm that these new Pd(II) complexes form a novel class of organometallic photoconductors with intrinsic characteristics suitable for molecular semiconductors applications.

Discotic (disk-shaped) molecules or molecular aggregates may form, within a certain temperature range, partially ordered phases, known as discotic liquid crystals, which have been extensively studied in the recent past. On the one hand, this interest was prompted by the fact that they represent models for testing energy and charge transport theories in organic materials. However, their long-range self-assembling properties, potential low cost, ease of processability with a variety of solvents and the relative ease of tailoring their properties via chemical synthesis, drove the attention of researchers also towards the exploitation of their semiconducting properties in organic electronic devices. This review covers recent research on the charge transport properties of discotic mesophases, starting with an introduction to their phase structure, followed by an overview of the models used to describe charge mobility in organic substances in general and in these systems in particular, and by the description of the techniques most commonly used to measure their charge mobility. The reader already familiar or not interested in such details can easily skip these sections and refer to the core section of this work, focusing on the most recent and significant results regarding charge mobility in discotic liquid crystals.

This paper reports the synthesis, liquid-crystal behavior, and charge-transport properties in the mesophase of triphenylene Schiff bases and their copper(II), nickel(II), and oxovanadium(IV) complexes. The thermal and electronic properties of the Schiff bases are modulated by coordination to the corresponding metal moieties, which have the ability to self-assemble into linear structures and help the alignment of the triphenylene columns. This produces two kinds of electronically nonconnected columnar regions, one purely organic and one more inorganic. The most remarkable effect is a striking charge mobility enhancement in the metal-containing mesophases, due to the contribution of the more inorganic columns: in comparison to values of hole mobility along the columnar stacking for the purely organic columnar mesophases, on the order of 10 -7 cm 2 V -1 s -1 , these values jump to 1-10 cm 2 V -1 s -1 in these hybrid inorganic/organic columnar materials.

Invasive species can encounter environments different from their source populations, which may trigger rapid adaptive changes after introduction (niche shift hypothesis). To test this hypothesis, we investigated whether postintroduction evolution is correlated with contrasting environmental conditions between the European invasive and source ranges in the Asian tiger mosquito Aedes albopictus . The comparison of environmental niches occupied in European and source population ranges revealed more than 96% overlap between invasive and source niches, supporting niche conservatism. However, we found evidence for postintroduction genetic evolution by reanalyzing a published ddRADseq genomic dataset from 90 European invasive populations using genotype-environment association (GEA) methods and generalized dissimilarity modeling (GDM). Three loci, among which a putative heat-shock protein, exhibited significant allelic turnover along the gradient of winter precipitation that could be associated with ongoing range expansion. Wing morphometric traits weakly correlated with environmental gradients within Europe, but wing size differed between invasive and source populations located in different climatic areas. Niche similarities between source and invasive ranges might have facilitated the establishment of populations. Nonetheless, we found evidence for environmental-induced adaptive changes after introduction. The ability to rapidly evolve observed in invasive populations (genetic shift) together with a large proportion of unfilled potential suitable areas (80%) pave the way to further spread of Ae. albopictus in Europe., Competing Interests: None declared., (© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

Computational and experimental studies unravel the structural and electronic properties of a novel supramolecular liquid crystal built through a hierarchical assembly process resulting in an H-bonded melamine rosette decorated with peripheral triphenylenes. The six-fold symmetry of the mesogen facilitates the formation of a highly organized hexagonal columnar mesophase stable at room temperature. X-ray diffraction and electron density maps confirm additional intra- and intercolumn segregation of functional subunits, and this paves the way for 1D charge transport. Indeed, hole mobility has been measured and found to be higher than for related mesogens. DFT calculations of HOMO and LUMO levels and parameters such as reorganization energy and transfer integral of the rosette structure have been achieved, and not only validate the columnar organization but also establish the way it translates into a favorable electronic architecture and molecular orbital interactions to promote charge carrier mobility., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Highly conductive coaxial supramolecular wires are prepared by using a new family of Janus dendrimers that combines two rigid aromatic parts and two flexible aliphatic parts. The two external regions consist of a promesogenic block based on a third generation Percec-type dendron with four terminal dodecyloxy alkyl chains, whereas the two internal regions are formed by one, two, or three carbazole units bearing flexible spacers. These functional Janus dendrimers self-organize in columnar liquid crystal phases with a strong coaxial segregation within each column. Interestingly, the charge mobility studies revealed that these Janus dendrimers display semiconductor properties with hole mobility values up to 0.5 cm 2 V -1 s -1 , depending on the packing within the columns which can be tuned by the number of carbazole functional units. The high hole mobility values measured in these materials are among the highest values reported for columnar liquid crystals.

The synthesis, self-assembly, and semiconducting properties of a series of disk-like truxenone derivatives, functionalized with three peripheral long alkyl chains, either directly attached or distanced by linking phenyl or ethynyl groups, are reported. The strategy of distancing the alkyl chains from the central aromatic cores induces in these discotics well-ordered columnar assemblies and has a favorable effect on their charge-carrier mobility. Electron mobility values above 1 cm 2  V -1  S -1 were determined for a truxenone functionalized with three peripheral decynyl chains by means of the space charge-limited current technique. DFT calculations help to rationalize the high mobility values found for these new truxenone-based systems, indicating efficient intermolecular electronic couplings (fostered by a favorable stacking configuration) and moderate intramolecular reorganization energies for electrons in the origin of such high mobilities., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Plasmonic quasi-periodic structures are well-known to exhibit several surprising phenomena with respect to their periodic counterparts, due to their long-range order and higher rotational symmetry. Thanks to their specific geometrical arrangement, plasmonic quasi-crystals offer unique possibilities in tailoring the coupling and propagation of surface plasmons through their lattice, a scenario in which a plethora of fascinating phenomena can take place. In this paper we investigate the extraordinary transmission phenomenon occurring in specifically patterned Thue-Morse nanocavities, demonstrating noticeable enhanced transmission, directly revealed by near-field optical experiments, performed by means of a scanning near-field optical microscope (SNOM). SNOM further provides an intuitive picture of confined plasmon modes inside the nanocavities and confirms that localization of plasmon modes is based on size and depth of nanocavities, while cross talk between close cavities via propagating plasmons holds the polarization response of patterned quasi-crystals. Our performed numerical simulations are in good agreement with the experimental results. Thus, the control on cavity size and incident polarization can be used to alter the intensity and spatial properties of confined cavity modes in such structures, which can be exploited in order to design a plasmonic device with customized optical properties and desired functionalities, to be used for several applications in quantum plasmonics.

A nanoplatform for simultaneous cellular imaging, and photodynamic and photothermal therapies has been designed and realized by embedding a purposely synthesized highly luminescent water soluble iridium(iii) compound into gold core-silica shell nanoparticles. These multifunctionalities arise mainly from the photophysical properties of the cyclometalated complex: (i) the heavy atom promotes, through excited triplet state formation, energy transfer processes towards molecular oxygen, with the generation of 1 O 2 (photodynamic effect); (ii) the overlap of the iridium(iii) complex emission band with the plasmonic resonance of gold nanostructures allows excitation energy transfer towards the metallic core (photothermal effect); (iii) the remarkable iridium(iii) complex luminescence feature, which is preserved despite energy transfer processes, makes the whole system an efficient luminescent bio-probe (imaging). Photophysical and photothermal investigations have been carried out, whereas in vitro photo-cytotoxicity tests have been performed on human glioblastoma cells (U87MG), highlighting significant cancer cell death at a very low photosensitizer concentration (<0.5 μM), by means of a synergistic photodynamic and photothermal effect.

We report a new family of multifunctional liquid-crystalline porphyrin-core dendrimers that have coumarin functional groups around the porphyrin core. Porphyrin metalation strongly affects the photophysical properties, and therefore Zn II and Cu II derivatives have also been prepared. All the synthesized dendrimers form a nematic discotic mesophase. Their high tendency for homeotropic alignment makes these dendrimers excellent candidates for device applications, owing to their easy processability, spontaneous alignment between electrodes, and self-healing of defects because of their dynamic nature. The charge mobility values of these materials are the highest ever reported for a nematic discotic phase. Moreover, these values are similar to the highest values reported for ordered columnar mesophases, and this shows that a supramolecular organization in columns is not necessary to achieve high charge mobility., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The p-type semiconducting properties of a triphenylene-fused triindole mesogen, have been studied by applying two complementary methods which have different alignment requirements. The attachment of only three flexible alkyl chains to the nitrogen atoms of this π-extended core is sufficient to induce columnar mesomorphism. High hole mobility values (0.65 cm 2 V -1 s -1 ) have been estimated by space-charge limited current (SCLC) measurements in a diode-like structure which are easily prepared from the melt, rendering this material a good candidate for OPVs and OLEDs devices. The mobility predicted theoretically via a hole-hopping mechanism is in very good agreement with the experimental values determined at the SCLC regime. On the other hand the hole mobility determined on solution processed thin film transistors (OFETs) is significantly lower, which can be rationalized by the high tendency of these large molecules to align on surfaces with their extended π-conjugated core parallel to the substrate as demonstrated by SERS. Despite the differences obtained with the two methods, the acceptable performance found on OFETs fabricated by simple drop-casting processing of such an enlarged aromatic core is remarkable and suggests facile hopping between neighboring molecular columns owing to the large conducting/isolating ratio found in this discotic compound.

A novel approach to ambipolar semiconductors based on hydrogen-bonded complexes between a star-shaped tris(triazolyl)triazine and triphenylene-containing benzoic acids is described. The formation of 1:3 supramolecular complexes was evidenced by different techniques. Mesogenic driving forces played a decisive role in the formation of the hydrogen-bonded complexes in the bulk. All of the complexes formed by nonmesogenic components gave rise to hexagonal columnar (Colh) liquid crystal phases, which are stable at room temperature. In all cases, X-ray diffraction experiments supported by electron density distribution maps confirmed triphenylene/tris(triazolyl)triazine segregation into hexagonal sublattices and lattices, respectively, as well as remarkable intracolumnar order. These highly ordered nanostructures, obtained by the combined supramolecular H-bond/columnar liquid crystal approach, yielded donor/acceptor coaxial organization that is promising for the formation of ambipolar organic semiconductors with high mobilities, as indicated by charge transport measurements.

The complete characterization of novel electropolymerizable organometallic complexes is presented. These are newly synthesized cyclometalated complexes of general formula (PPy)M(O ∧ N)(n) (H(PPy) = 2-phenylpyridine, M = Pd(II) or Pt(II), H(O ∧ N)(n) = Schiff base). Polymeric thin films have been obtained from these complexes by electropolymerization of the triphenylamino group grafted onto the H(O ∧ N)(n) ancillary ligand. The redox behavior and the photoconductivity of both of the monomers (PPy)M(O ∧ N)(n) and the electropolymerized species have been investigated. The polymeric films of (PPy)M(O ∧ N)(n) have shown a very significant enhancement of photoconductivity when compared to their monomeric amorphous counterparts. The high stability of the obtained films strongly suggests that electropolymerization of cyclometalated complexes represents a viable deposition technique of quality thin films with improved photoconduction properties, hence opening the door to a new class of materials with suitable properties for optoelectronic applications.

The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole-containing 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) dendrons are reported. The liquid-crystal behaviour was investigated by means of differential scanning calorimetry, polarised-light optical microscopy and X-ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel liquid crystal (LC) dendrimers have been synthesised by hydrogen bonding between an s-triazine as the central core and three peripheral dendrons derived from bis(hydroxymethyl)propionic acid. Symmetric acid dendrons bearing achiral promesogenic units have been synthesised to obtain 3:1 complexes with triazine that exhibit LC properties. Asymmetric dendrons that combine the achiral promesogenic unit and an active moiety derived from coumarin or pyrene structures have been synthesised in order to obtain dendrimers with photophysical and electrochemical properties. The formation of the complexes was confirmed by IR and NMR spectroscopy data. The liquid crystalline properties were investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffractometry. All complexes displayed mesogenic properties, which were smectic in the case of symmetric dendrons and their complexes and nematic in the case of asymmetric dendrons and their dendrimers. A supramolecular model for the lamellar mesophase, based mainly on X-ray diffraction studies, is proposed. The electrochemical behaviour of dendritic complexes was investigated by cyclic voltammetry. The UV/Vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers were also investigated., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50 degrees C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (sigma/I approximately 8x10(-13) S cm W(-1) with E = 10 V microm(-1) at lambda = 370 nm). Moreover, complex 2 shows a normalized photoconductivity sigma/I = 8.5x10(-13) S cm W(-1) at lambda = 760 nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors.

Nanocrystals (50-250 nm) of a Palladium complex within a polyisobutylmethacrylate matrix were prepared by a phase separation method. In these dispersions, a light-induced birefringence with Deltan approximately 10(-3) was induced, without the application of an electric field. This effect was related to the photoconducting properties of the dispersion. Evidence for charge photogeneration without any applied field was obtained. The photorefractive behaviour of the material confirmed that the nanocrystals reorientation is a consequence of photoconducting properties. A light-generated electric field approximaely E 3 V/microm was estimated. These results illustrate the potential of materials with a nano-crystalline dispersion morphology as light-responsive media.

We present results on the photorefractive properties of chiral smectic A liquid-crystal phases dispersed in cylindrical cavities in a photoconducting polymer. The refractive-index modulation is due to the electroclinic effect, which is linear in the electric field, in contrast with the effect that is due to the dielectric anisotropy that is typical of nematic phases. We obtained grating buildup times of ~25 ms , limited by the speed of the space-charge field formation in the photoconducting matrix.