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The regioselective nitration of 9,9′-spirobifluorene under mild conditions is reported for the first time by operating under Menke’s and Crivello’s conditions. The optimized protocol allows obtaining 2-nitro and 2,2′-dinitro-9,9′-spirobifluorene in yields of 79 and 95% and, for the first time, 2,2′,7-trinitro-9,9′-spirobifluorene with 66% yield. Besides, the role of dinitrate salt in Crivello’s protocol has been now clarified, which opens novel scenarios in the preparation of functional materials.

An easy and cost-effective method is presented to functionalize graphene through thermally activated dimerization of 2,5-diaryltetrazoles. Consistently with the experimental spectroscopic results, theoretical calculations demonstrate that during the thermal treatment a dimerization process to tetrazine is energetically more favorable than covalent grafting. Since both the functionalization method by thermal activation and the use of tetrazoles have never been considered before to prepare graphene-based chemiresistors, this represents a promising approach to develop graphene-related sensing platforms. Five different 2,5-diaryltetrazoles have been tested here for the effective functionalization of low-defect graphene layers on silicon nitride. Based on these layers, an array of sensors has been prepared for testing upon ammonia exposure. The tests on the sensing performances clearly show sensitivity to ammonia, extending the current range of ammonia detection with a graphene-based chemiresistor down to the sub-ppm range, as results from a benchmarking with data available in the literature. Furthermore, all sensors perform better than bare graphene. Density functional theory (DFT) calculations, carried out on a model of the best performing layer of the array, provided the theoretical framework to rationalize the sensing mechanism and disclose a dual role played by the tetrazine molecules, (i) acting as ammonia concentrators and (ii) mediating the electron transfer between ammonia and graphene.

During infection, bacteria use an arsenal of resistance mechanisms to negate antibiotic therapies. In addition, pathogenic bacteria form surface-attached biofilms bearing enriched populations of metabolically dormant persister cells. Bacteria develop resistance in response to antibiotic insults; however, nonreplicating biofilms are innately tolerant to all classes of antibiotics. As such, molecules that can eradicate antibiotic-resistant and antibiotic-tolerant bacteria are of importance. Here, we report modular synthetic routes to fluorine-containing halogenated phenazine (HP) and halogenated acridine (HA) agents with potent antibacterial and biofilm-killing activities. Nine fluorinated phenazines were rapidly accessed through a synthetic strategy involving (1) oxidation of fluorinated anilines to azobenzene intermediates, (2) S(N)Ar with 2-methoxyaniline, and (3) cyclization to phenazines upon treatment with trifluoroacetic acid. Five structurally related acridine heterocycles were synthesized using S(N)Ar and Buchwald–Hartwig approaches. From this focused collection, phenazines 5g, 5h, 5i, and acridine 9c demonstrated potent antibacterial activities against Gram-positive pathogens (MIC = 0.04–0.78 μM). Additionally, 5g and 9c eradicated Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis biofilms with excellent potency (5g, MBEC = 4.69–6.25 μM; 9c, MBEC = 4.69–50 μM). Using real-time quantitative polymerase chain reaction (RT-qPCR), 5g, 5h, 5i, and 9c rapidly induce the transcription of iron uptake biomarkers isdB and sbnC in methicillin-resistant S. aureus (MRSA) biofilms, and we conclude that these agents operate through iron starvation. Overall, fluorinated phenazine and acridine agents could lead to ground-breaking advances in the treatment of challenging bacterial infections.

Anionic electrolyzers are expected to play a major role in the future massive production of green hydrogen. In this context, anionic membranes are still a bottleneck for their low conductivity and insufficient long-term chemical stability. In this paper we discussed and demonstrated the use of chemically modified, Aquivion®-based anionic membranes for water electrolysis. The membranes were subjected to different ageing treatments up to 3 M at 80 °C and showed better performance and durability than commercial Aemion™. Current density values around 130 mA cm−2 at 2 V were obtained with nickel foam as a benchmark electrode material.

The photon upconversion based on triplet–triplet annihilation (TTA) is a mechanism that converts the absorbed low-energy electromagnetic radiation into higher energy photons also at extremely low excitation intensities, but its use in actual technologies is still hindered by the limited availability of efficient annihilator moieties. We present here the results obtained by the synthesis and application of two new fluorinated chromophores based on phenazine and acridine structures, respectively. Both compounds show upconverted emission demonstrating their ability as TTA annihilator. More interesting, the acridine-based chromophore shows an excellent TTA yield that overcomes the one of some of best model systems. By correlating the experimental data and the quantum mechanical modeling of the investigated compound, we propose an alternative efficient pathway for the generation of the upconverted emissive states involving the peculiar high-energy triplet levels of the dye, thus suggesting a new development strategy for TTA annihilators based on the fine tuning of their high-energy excited states properties.Graphical abstract

In this paper we performed the deposition and self-assembly of a Pd-cyclometallated compound on Ag(1 1 0) surface for the first time. The system is investigated from the morphological and chemical point of view by scanning tunneling microscopy and x-ray photoemission spectroscopy, respectively, and the results are validated by ab-initio calculations. Our combined experimental and theoretical study aims at elucidating the atomistic details of the chemical steps following Pd cyclometallate deposition on the metallic substrate. To do that, we analyze the electronic and chemical properties of the species present on the surface at the end of the preparation process at room temperature and at 150 degrees C. We observe an unexpected complex chemistry: on one side, the organometallic molecules are found to dissociate into fragments, forming a well-ordered metal-carbon network; on the other side, Pd atoms become buried in the bulk of the metal substrate following metal exchange with surface Ag atoms. The details of this mechanistic study reveal the active role played by the metal substrate in promoting the chemistry of the deposited Pd cyclometallates and could open new perspectives for the application of this class of materials in heterogeneous catalysis.

The Pd cyclometallated complex [(5-bromo-2-phenylpyridine)Pd(μ-Cl)]2 is deposited on Ag(1 1 0) at room temperature by sublimation in ultra-high vacuum. The thermal evolution of the system is followed by scanning tunnelling microscopy and X-ray photoemission spectroscopy, while the initial and final configurations are validated by ab-initio calculations. We observe the surface induced dissociation of the molecule and the occurrence of a cross coupling reaction between the two organic fragments, leading to the surface assisted synthesis of diphenyl-bipyridine molecules. Such a process, occurring with low probability at RT, is thermally activated and competes with desorption. At variance with most cross-coupling reactions at surfaces reported in literature, in this case the reactants come from the dissociation of the same compound so that only one precursor is employed, leading to a simplified preparation protocol. The Br and Cl atoms dissociated from the molecule bind to the surface and promote an extended surface reconstruction upon annealing, which was not observed previously upon deposition of halogenated aromatic compounds.

Gelatin is a costless polypeptide material of natural origin, able to form hydrogels that are potentially useful in biomaterial scaffold design for drug delivery, cell cultures, and tissue engineering. However, gelatin hydrogels are unstable at physiological conditions, losing their features only after a few minutes at 37 °C. Accordingly, treatments to address this issue are of great interest. In the present work, we propose for the first time the use of bi- and trifunctional tetrazoles, most of them unknown to date, for photoinduced gelatin cross-linking towards the production of physiologically stable hydrogels. Indeed, after UV-B irradiation, aryl tetrazoles generate a nitrilimine intermediate that is reactive towards different functionalities, some of them constitutively present in the amino acid side chains of gelatin. The efficacy of the treatment strictly depends on the structure of the cross-linking agent used, and substantial improved stability was observed by switching from bifunctional to trifunctional cross-linkers.

A high ortho regioselectivity in nucleophilic aromatic substitution in low polar solvents is reported in the reaction of polyfluorinated azobenzenes with anilines. o-Anilino substituted derivatives could be easily transformed into non-symmetric phenazines by acid catalyzed electrocyclization. Phenazines are interesting compounds for their important properties as bioactive molecules. In addition, these fluorinated phenazines manifest interesting spectroscopic and electronic properties that make them candidates for n-type organic semiconductor. Furthermore, the prepared phenazines show reversible reduction with the LUMO and HOMO energy level controlled by the electronic nature of the substituent on the non-fluorinated ring of the system.

Anion-exchange membranes (AEMs) are of growing interest for electrochemical devices such as fuel cells and electrolyzers because the alkaline medium allows avoiding the use of platinum and platinum-group metals as the electrocatalysts. Perfluorinated polymers are a good starting point to prepare AEMs because of their chemical stability and potential high conductivity resulting from the coexistence of hydrophobic main chains and flexible hydrophilic side chains. Here, we report a facile and simple chemical modification of Aquivion® performed in aqueous environment. We obtained a chemically stable membrane with ionic conductivity exceeding 2.5×10−2 S cm−1 at 80 °C and 100 RH% that was used in a polymer fuel cell.

Medical-grade poly(methyl methacrylate) (PMMA) is widely employed in the fabrication of intraocular lenses (IOLs), but suffers from opacification, a postoperative complication that leads to the failure of the implanted intraocular lenses. The opacification occurs when inorganic-based deposits accumulate on the surface of the IOL and are prevalent in hydrophilic materials. Here, the surface of medical-grade PMMA has been fluorinated by sulphur hexafluoride (SF6) plasma treatment to increase surface hydrophobicity thus improving the material lifetime in optical applications. Hydrophobic properties of the treated PMMA were investigated by means of contact angle measurements, while chemical modification was assessed by X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR/FTIR) spectroscopy. Surface morphological changes due to possible etching effects were investigated by Atomic Force Microscopy (AFM). The transparency of the treated PMMA was assessed by UV/VIS spectroscopy. Finally, the influence of the plasma treatment on the inorganic salts deposition was investigated by immersion in Simulated Aqueous Humour (SAH), followed by XPS analysis. The modified samples showed less deposition on the surface than the unmodified sample, moreover, a decrease of the transmittance in the UV-violet range (300&ndash, 430 nm) was detected, open the possibility of interesting applications of this treatment for the creation of a UV filter in ophthalmic optical devices.

Non-symmetric phenazines were synthesized via the Buchwald-Hartwig amination of ortho-bromoazobenzenes with anilines under micellar conditions, using the commercially available surfactant Kolliphor EL in water, followed by an acid-promoted 6π-electrocyclization-aromatization process. Two different synthetic pathways to obtain the ortho-bromo azo intermediates were explored, namely the palladium catalysed selective ortho bromination of azobenzenes and the diazo coupling of ortho-bromo diazonium salts with N,N-dimethylaniline, imidazole, phenol, sodium methanesulfinate and ethyl chloroformate.

Graphene nanoribbons (GNRs) are at the frontier of research on graphene materials since the 1D quantum confinement of electrons allows for the opening of an energy gap. GNRs of uniform and well-defined size and shape can be grown using the bottom-up approach, i.e. by surface assisted polymerization of aromatic hydrocarbons. Since the electronic properties of the nanostructures depend on their width and on their edge states, by careful choice of the precursor molecule it is possible to design GNRs with tailored properties. A key issue for their application in nanoelectronics is their stability under operative conditions. Here, we characterize pristine and oxygen-exposed 1.0 nm wide GNRs with a well-defined mixed edge-site sequence (two zig-zag and one armchair) synthesized on Ag(110) from 1,6-dibromo-pyrene precursors. The energy gap and the presence of quantum confined states are investigated by scanning tunneling spectroscopy. The effect of oxygen exposure under ultra-high vacuum conditions is inferred from scanning tunneling microscopy images and photoemission spectra. Our results demonstrate that oxygen exposure deeply affects the overall system by interacting both with the nanoribbons and with the substrate; this factor must be considered for supported GNRs under operative conditions.

A solventless mechanochemical methodology for the oxidation of electron-poor fluorinated anilines to the corresponding symmetrical azo compounds has been developed. In this process phenyliodine(III)diacetate and inexpensive calcium hypochlorite demonstrate to be good oxidants, providing the desired fluorinated azobenzenes in satisfactory yields, within short reaction times and avoiding the use of environmental unfriendly metal reagents.

A series of Donor-Acceptor-Donor (D-A-D) and Acceptor-Donor-Acceptor (A-D-A) compounds have been prepared exploiting the relative ability of polyfluorinated azobenzenes and benzophenone to undergo aromatic nucleophilic substitution reactions with aromatic amines. A high para-regioselectivity is obtained when fluorene and carbazole-based diamines have been used in a high Donor Number solvent environment such as DMSO. The prepared triads have been employed in the synthesis of oligomers with the aim of evaluating them as photovoltaic material additives in optoelectronic applications.

The surface-assisted synthesis of gold-organometallic hybrids on the Au(111) surface both by thermo- and light-initiated dehalogenation of bromo-substituted tetracene is reported. Combined X-ray photoemission (XPS) and scanning tunneling microscopy (STM) data reveal a significant increase of the surface order when mild reaction conditions are combined with 405 nm light irradiation.

Intraocular lenses can be manufactured from a wide variety of polymers, but due to the lost cost associated with the use of Poly(methyl methacrylate) (PMMA), it is still the preferred material used in the developing countries. However, a major drawback to its use is the build-up of calcium containing deposits that are formed on the intraocular lens over a period of time. In an attempt to hinder this deposition, surface modification of medical grade PMMA has been carried out using perfluoroalkyl chain (1,2,4-trifluoro-3- (C10F21CH2O)-7-(N,N)-dimethylaminoacridine) segregation. The segregation was explored using a 1% 1,2,4-trifluoro-3-(C10F21CH2O)-7-(N,N)-dimethyla- minoacridine in two methods: film casting and spin-coating, a thin film onto preformed PMMA discs. Both methods were compared against control PMMA to determine which method provided the best hindrance against calcium containing deposits when immersed in a simulated aqueous humour solution. Characterisation of the surface using scanning electron microscopy coupled with energy; dispersive x-ray analysis indicated that the surface segregation of perfluoroalkyl chains had hindered calcification in both methods. This pleminary research shows promising results of employing perfluoroalkyl chains in the surface segregation of biomaterials that can be employed in intraocular lenses.

[EN] The MOSCAB experiment (Materia OSCura A Bolle) uses the "geyser technique", a variant of the superheated liquid technique of extreme simplicity. Operating principles of the new dark matter detector and technical solutions of the device are reported in detail. First results obtained in a series of test runs taken in laboratory demonstrate that we have successfully built and tested a geyser-concept bubble chamber that can be used in particle physics, especially in dark matter searches, and that we are ready to move underground for extensive data taking., We gratefully acknowledge support from Istituto Nazionale di Fisica Nucleare (INFN) and Spanish Ministerio de Economia y Competitividad (MINECO), Grants FPA-2015-65150-C3-2-P (MINE-CO/FEDER), and Consolider MultiDark CSD2009-00064. We are grateful to Laboratori Nazionali delGran Sasso (LNGS) for hosting and supporting the MOSCAB project. We thank Massimo Locatelli, Tecnologia Meccanica, Treviolo (BG), Italy, for supporting our project with hard work, competence and passion, and Francesco Boccardo, Vincenzo Caglioti and Dario Menasce for fruitful discussions and their contribution in preparing the manuscript.

The synthesis of a novel electron-deficient derivatives of pyrrolo[3,4-c]pyrrole-1,4 (2H,5H)-dione, (DPP), 1,4-bis-(4-butyl-phenyl)-3,6-di-thiophen-2-yl-pyrrolo[3,2-b]pyrrole-2,5 – (1H,4H)-dione and 1,4-bis-(4-(pentyloxy)phenyl)-3,6-bis(thiophen-2-yl-pyrrolo[3,2-b]pyrrole-2,5-(1H,4H)-dione are reported. This new building block was copolymerized with bistannanes of thiophene and bithiophene and fluorene by using Stille or Suzuki polymerization, affording the corresponding copolymers ( P1 – P4 , respectively). These exhibit small energy band gaps combined with low-lying HOMO energy levels. Energy band gaps of P1 and P2 , calculated from absorption spectra, are 1.63 and 1.73 eV, respectively. The HOMO and LUMO energy levels of P1 and P2 are −5.12, −3.50, −5.09 and −3.50 eV respectively, as determined by cyclic voltammetry. The power conversion efficiency of P1:PC 61 BM-based photovoltaic cells illuminated by AM 1.5G was 1.24%, without optimization of materials, significantly higher than for P2 :PC 61 BM, 0.33%. These results demonstrate that thiophene-pyrrolo[3,2-b]pyrrole-2,5-dione conjugated copolymers are promising materials for bulk heterojunction solar cell applications.

Gelatin is a biopolymer with interesting properties that can be useful for biomaterial design for different applications such as drug delivery systems, or 3D scaffolds for tissue engineering. However, gelatin suffers from poor mechanical stability at physiological temperature, hence methods for improving its properties are highly desirable. In the present work, a new chemical cross-linking strategy based on triazolinedione ene-type chemistry towards stable hydrogel is proposed. Two different homobifunctional 1,2,4-triazoline-3,5(4H)-diones, namely 4,4&prime, hexane-1,6-diylbis(3H-1,2,4-triazoline-3,5(4H)-dione) 1 and 4,4&prime, [methylenebis(4,1-phenylene)]bis(3H-1,2,4-triazoline-3,5(4H)-dione) 2 were used as cross-linkers in different ratio to tyrosine residues in gelatin. The reaction was proved effective in all experimented conditions and hydrogels featured with different thermal stability were obtained. In general, the higher the cross-linker/tyrosine ratio, the more thermostable the hydrogel. The swelling properties are strictly dependent upon the chemical nature of the cross-linker.

On-surface synthesis of thin organic and organometallic films in a bottom-up fashion has become a promising approach for the development of new nanotechnologies. In this work we studied 5,11-dibromotetracene (C18H10Br2) as a prototypical case of rodlike polyaromatic molecules functionalized with two bromine atoms on the sides. The adsorption and temperature-stimulated transformations of dibromotetracene assemblies on Ag(110) have been investigated by a combination of synchrotron radiation X-ray photoemission spectroscopy (XPS), near-edge X-ray absorption spectroscopy (NEXAFS), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Upon the contact with the Ag substrate, the Br-C bonds are promptly cleaved at room temperature, and Ag-coordinated protopolymers are formed along the [001] substrate direction. The organometallic diners and trimers remain on the surface up to 523 K. The stabilization of the protopolymers is driven by the substrate anisotropy and weak interactions with nearby Br atoms. The short oligomers formed at elevated temperatures are weakly bounded to the substrate and desorb before covalent structures can be formed.

By a combination of scanning tunneling microscopy, X-ray spectroscopic techniques and density functional theory calculations, we prove the formation of extended patterns of parallel, graphene nanoribbons with alternate zig-zag and armchair edges and selected width by surface-assisted Ullmann coupling polymerization and dehydrogenation of 1,6-dibromopyrene (C16H8Br2). Besides the relevance of these nanostructures for their possible application in nanodevices, we demonstrate the peculiarity of halogenated pyrene derivatives for the formation of nanoribbons, in particular on Ag(110). These results open the possibility of tuning the shape and dimension of nanoribbons (and hence the correlated electronic properties) by choosing suitably tailored or on-purpose designed molecular precursors.

Bones are potentially the best age indicators in a stratigraphic study, because they are closely related to the layer in which they are found. Collagen is the most suitable fraction and is the material normally used in radiocarbon dating. Bone contaminants can strongly alter the carbon isotopic fraction values of the samples, so chemical pretreatment for 14∈C dating by accelerator mass spectrometry (AMS) is essential. The most widespread method for collagen extraction is based on the Longin procedure, which consists in HCl demineralization to dissolve the inorganic phase of the samples, followed by dissolution of collagen in a weak acid solution. In this work the possible side effects of this procedure on a modern bone are presented; the extracted collagen was analyzed by ATR-IR spectroscopy. An alternative procedure, based on use of HF instead of HCl, to minimize unwanted degradation of the organic fraction, is also given. A study by ATR-IR spectroscopic analysis of collagen collected after different demineralization times and with different acid volumes, and a study of an archaeological sample, are also presented. © 2011 Springer-Verlag.

The solid state magnetic properties of two new molecular organic materials based on polyfluoro- acridines functionalised with the 2,2,6,6-tetramethyl piperidine-1-oxyl radical (TEMPO) have been ana- lyzed. After a first characterisation of the two materials by electron paramagnetic resonance and by X-ray diffraction, magnetisation measurements were performed from room temperature down to 2 K and the paramagnetic behaviour due to the unpaired spin on the radical TEMPO observed. Both compounds show some ferro-magnetic interactions down to 40 K, while at lower temperatures an antiferro-magnetic contribution switches on, possibly related to the reduction of intermolecular distances.

Blue amplified spontaneous emission at room temperature is demonstrated from the exposed face of the strongly emitting organic semiconductor 1,1,4,4-tetraphenyl-1,3-butadiene in single crystal form. The symmetry of the crystal and calculation of lattice sums indicate the J-type organization of the molecular transition moments. The minimum in the lowest exciton dispersion branch, from which emission takes place, is found at the edge of the Brillouin zone leading to a dominant vibronic emission since the zero-phonon line is forbidden. The observed gain narrowed line is attributed to the vibronic replica which becomes amplified with increased pumping. The reported emission is along the normal to the exposed crystal face, important for the development of vertical cavity geometry lasers based on organic single crystals. The threshold excitation fluence of 400 microJ cm(-2) is comparable to other organic crystalline systems, even if the amplification path is much reduced as a consequence of the vertical geometry. Considering these relevant aspects, the optical characterization of this material is provided. The polarized absorption spectra are reported and the properties of the lowest-energy excitonic state investigated. Calculation of the electronic transitions for the isolated molecule, lattice sums for the transition at lowest energy, and the symmetry of the crystal allow attributing the largest face of the samples and the observed optical bands in the spectra. Polarized time-resolved spectra are also reported allowing to identify the intrinsic excitonic emission.

The synthesis of a new DO3A -based macrocyclic ligand bearing a 8-hydroxyquinoline residue together with the preparation of its Eu 3+ and Er 3+ neutral complexes are described. In a previous report [F. Rizzo, A. Papagni, F. Meinardi, R. Tubino, M. Ottonelli, G.F. Musso, G. Dellepiane, Synth. Met. 147 (2004) 143], we have shown that lanthanide complexes display very high stability combined with a good luminescence in aqueous solution under UV radiation, which indicate an energy transfer process from the excited 8-hydroxyquinoline moiety to the metal. In this work, we correlate the ability to transfer the energy from the sensitizer to lanthanide ion with pH behaviour of the antenna. Furthermore, the variation of pH in Eu 3+ complex supports the hypothesis of presence of charge-transfer transitions. The good solubility and sensitized emission in different solvents (organic and water) are very important aspects for their technologic applications as luminescent probes or NIR-emitting devices.

The transmittance, reflectance, and photoluminescence optical spectra of lamellar cadmium phosphorus trisulfide ?(CdPS 3 ) crystals are reported, as measured before and after intercalation with quaterthiophene (4T) molecules. The optical properties of pristine CdPS 3 and 4T intercalates have been characterized in the 2-6 eV spectral region by the full complex refractive index. This latter has been deduced from transmittance and reflectance measurements and by Kramers-Kronig relations. The comparison of optical properties of CdPS 3 and its 4T intercalate provide information on the arrangement of the molecules inside the inorganic layers and on the interactions between the organic molecules and between the organic and inorganic components.

Here we describe the synthesis of polyfluoro-acridines functionalised with perfluoro-alkyl and perfluoro-alkoxy chains, obtained by Ullmann coupling reaction or aromatic nucleophilic substitution. Surface wettability of PMMA is changed by doping with tetrafluoro-perfluorodecyl-acridine, as shown by AFM and contact angle measurements.

Polyamide 6 (PA6) nanotibers were prepared from formic acid solutions by using electrospinning technique. The fibers were smooth, defects free and with diameters smaller than 200 nm. Small amounts of a perfluorinated acridine were added as dopant to the feed solution to modify the wettability of the fibers. The effect of doping on the contact angle values is well apparent. The contact angle values go from 50 degrees of pure PA6 to 120 degrees when 6% of acridine is added. A comparison between fibers and films of pure and doped polyamide 6 was carried out in order to determine the effect of morphology on wettability. Thermal annealing near the T, of the polymer promoted the segregation of the molecules to the surface, reaching contact angles of 131 degrees with smaller amounts (4%) of acridine. The surface segregation was also promoted by time aging. (c) 2007 Elsevier B.V. All rights reserved.

Materials Science represents the natural convergence of hard scientific disciplines such as Physics Mathematics and Chemistry whom synergic contribution to its definition and evolution is at the basis of huge technologic development observed during the last few decades. The wide variety of materials under investigation by this discipline is both strategic for the economy of a Nation as well as a fundamental aspect of everyday life. Among the most relevant ones so far proposed, many advanced materials are organic-based or, in other words, constituted by molecules or organic polymers, not only for their application potential, low costs and preparation flexibility but also for their processability and limited environmental impact.

Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions.

The absorption spectra of different oligothiophene single crystals without saturation effects in a wide spectral range are reported and compared. The origin of the main ac polarized broad band is discussed in terms of Frenkel excitons. Exploiting experimental configurations which correspond to the excitation of the weak dielectric tensor components, bands of different nature are also detected at different positions for orthogonal polarizations and attributed to transitions of charge-transfer character. (c) 2006 Elsevier B.V. All rights reserved.

Hot-wall epitaxy and molecular-beam epitaxy have been employed for growing quaterthiophene thin films on the (010) cleavage face of potassium hydrogen phthalate, and the results are compared in terms of film properties and growth mode. Even if there is no geometrical match between substrate and overlayer lattices, these films are epitaxially oriented. To investigate the physical rationale for this strong orientation effect, optical microscopy, atomic force microscopy, and X-ray diffraction are employed. A clear correlation between the morphology of the thin films and the crystallographic orientation is found. The results are also validated by surface potential calculations, which demonstrate the primary role played by the corrugation of the substrate surface.

In this study, we have shown the intracellular distribution of choline and phosphatidylcholine fluorescent derivatives in human breast carcinoma cells using confocal microscopy. The fluorescent choline derivatives ethanamimium 2-hydroxy-NN-dimethyl-N-[2N-(2,1,3-benzoxadiazol-4-amine,-N-methyl,-7-nitro)-ethyl] bromide (NBD-choline) and C-6-NBD-phosphatidylcholine (C-6-NBDPC) were used in this work. NBD-choline was easily internalised into drug sensitive MCF-7 and in multidrug resistant MCF-7/DX cells. The probe was found to localise in the endoplasmic reticulum of sensitive cells and in the Golgi of multidrug resistant cells. In contrast, very low accumulation was found in normal MCF10A cells. For C-6-NBD-PC, a similar pattern of localisation was found in tumour cells, but a significant uptake was also observed in normal cells. Unlike NBD-choline, C6-NBD-PC appears not to discriminate between normal and tumour cells. These results are consistent with previously published results showing higher levels of C-11-choline uptake in malignant lesions seen with positron emission tomography (PET) in vivo imaging. Our results suggest that using NBD-choline and laser scanning confocal fluorescence microscopy (LSCFM) could be a useful tool to study choline metabolism in cancer cells and to consolidate PET imaging findings. (c) 2005 Elsevier Ltd. All rights reserved.

We examine absorption of light in quaterthiophene crystals for different directions of the ray and wave-normal vector after refraction on the vacuum/crystal interface. Experimental non-normal incidence spectra are reported where different absorption bands show different behaviour as a function of the angle of incidence. This allows to identify those originating from the b(u) Frenkel exciton state. (C) 2004 Elsevier B.V. All rights reserved.

The photophysical processes leading to sensitised green emission of a blend made by a host polymer poly(vinyl-carbazole) doped with a fluorinated acridine are investigated by means of steady-state and time-resolved luminescence. The large overlap between the donor emission and the acceptor absorption produces an efficient resonant energy transfer process from the host to the dye. At low dopant concentration, the dependence of the Förster radius on the temperature is consistent with a thermally activated hopping process of the exciton within the donor prior to the resonant energy transfer to the acceptor. The activation energy for the hopping process is around 20 meV. © 2004 Elsevier B.V. All rights reserved.

The stereoselective [2+2] cycloaddition reaction between the chiral tricarbonyl(eta(6)arene) chromium(0) complexed imines 1 and 6 and phthalimidoketene affords tricarbonyl (eta(6)arene)chromium(0) complexed 3-phthalimido-2-azetidinones 3, 7 and 8, both in racemic and enantiopure form. Decomplexation and the cleavage of the phthalimido group give 3-amino-4-substituted-2-azetidinones 5 and 10. Some insights into the stereochemical outcome of the [2+2] cycloaddition process are discussed. (C) 2003 Elsevier Ltd. All rights reserved

This paper describes a convenient preparation of tetrathia-[7]-helicene (TH[7]), the generation of the alpha-anion on the terminal thiophene ring, and the synthesis of the 2-formyl-tetrathia-[7]-helicene (2-CHO-TH[7]). The key intermediate trans-1,2-dibenzodithiopheneethene, prepared in 97% yield by McMurry coupling of the 2-formyl-benzo[1,2-b;4,3-b']dithiophene, was transformed into TH[7] using a known procedure. The described method affords TH[7] in 46% overall yield, which is more than four times the yield previously reported in the literature. The alpha-anion of TH[7], which is easily generated on the alpha-position of one of the terminal thiophene rings, reacts with electrophilic reagents such as D2O and DMF. The latter reaction proved to be the best way to prepare 2-CHO-TH[7], a key intermediate for the preparation of new substituted heterohelicenes. (C) 2003 Elsevier Ltd. All rights reserved.

Photoluminescence (PL) emission spectra of sexithiophene (6T) thin films grown on different substrates by organic molecular beam deposition (OMBD) are studied in the range of temperature from 300 to 7 K. Besides the two vibronic progressions detectable between 300 and 50 K, related to the radiative recombination of the free exciton and to a structural defect state, a new emission is observed at temperatures lower than 40 K, whose origin is discussed in terms of exciton bound to a structural defects. (C) 2002 Elsevier Science B.V. All rights reserved.

Phloem, a plant tissue responsible for long-distance molecular transport, harbours specific junctions, sieve areas, between the conducting cells. To date, little is known about the molecular framework related to the biogenesis of these sieve areas. Here we identify mutations at the CHER1/AtCTL1 locus of Arabidopsis thaliana. The mutations cause several phenotypic abnormalities, including reduced pore density and altered pore structure in the sieve areas associated with impaired phloem function. CHER1 encodes a member of a poorly characterized choline transporter-like protein family in plants and animals. We show that CHER1 facilitates choline transport, localizes to the trans-Golgi network, and during cytokinesis is associated with the phragmoplast. Consistent with its function in the elaboration of the sieve areas, CHER1 has a sustained, polar localization in the forming sieve plates. Our results indicate that the regulation of choline levels is crucial for phloem development and conductivity in plants. © 2014 Macmillan Publishers Limited. All rights reserved.

Despite the relevance of carbohydrates as cues in eliciting specific biological responses, the covalent surface modification of collagen-based matrices with small carbohydrate epitopes has been scarcely investigated. We report thereby the development of an efficient procedure for the chemoselective neoglycosylation of collagen matrices (patches) via a thiol-ene approach, between alkene-derived mono-saccharides and the thiol-functionalized material surface. Synchrotron radiation-induced X-ray photoelectron spectroscopy (SR-XPS), Fourier transform-infrared (FT-IR), and enzyme-linked lectin assay (ELLA) confirmed the effectiveness of the collagen neoglycosylation. Preliminary biological evaluation in osteoarthritic models is reported. The proposed methodology can be extended to any thiolated surface for the development of smart biomaterials for innovative approaches in regenerative medicine.