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The interaction of 1,8‐diaminonaphthalene with o‐xylylene dibromide leads to two topologically relevant isomeric products, 1,8‐di(isoindolin‐2‐yl)naphthalene (reported previously), and its structural isomer with the bridgehead nitrogens in a bicyclic system (reported for the first time). This is the first case of isolating two heterocyclic analogs of 1,8‐bis(dimethylamino)naphthalene (proton sponge or DMAN) in one reaction. Both isomers are formed in parallel reactions and are not interconverted upon acid treatment. The first representative of heterocyclic "amide proton sponges", which is still able to participate in intramolecular protonation due to the amide nitrogen atom, was synthesized by direct oxidation of the corresponding isoindoline derivative. Using p‐xylylene dibromide as a bridging bielectrophile, a macroheterocyclization was effectively realized to construct the first paracyclophane extended by two DMAN subunits. Mostly driven by the proximity effect, the molecular structure, unusual protonation trends and reactivity of peri‐diaminonaphthalenes N‐linked with o‐ and p‐xylylene fragments are also discussed. [ABSTRACT FROM AUTHOR]

In this study, we employed several experimental techniques to investigate structure and magnetic properties of poly(p-xylylene)–MnSb composites synthesized by low-temperature vapor deposition polymerization technique and MnSb films deposited at various temperatures. The presence of MnSb nanocrystallites in the studied films was verified by the results of X-ray diffraction, electron microscopy and Raman spectroscopy studies. The obtained data revealed the formation of Sb-rich sublayer with well-oriented Sb grains near the susbtrate, which seems to act as a buffer for the consequent poly(p-xylylene)–MnSb or MnSb layer growth. Increasing the polymer content results in qualitative change of surface morphology of studied films. At high polymer content the hybrid nanocomposite with MnSb nanoparticles embedded into poly(p-xylylene) matrix is formed. All investigated samples demonstrated detectable ferromagnetic response at room temperature, while the parameters of this response revealed a complex correlation with nominal composition, presented crystal phases and surface morphology of studied films. Estimated values of the Curie temperature of the samples are close to that of bulk MnSb. [ABSTRACT FROM AUTHOR]

The structure and conductivity of hybrid nanocomposite poly(p-xylylene) films containing iron nanoparticles are studied. The films are obtained by the method of polymerization on a surface from the gas phase, and the concentration of the filler is 4 and 11 vol %. According to the analysis of microphotographs of nanostructures obtained by transmission electron microscopy, the particles are distributed evenly (with a size in the nanometer range and a rather narrow distribution). Studies of the frequency dependence of conductivity show that the transport of the charge carriers is realized by the hopping mechanism with a jump length of ~3.5 nm. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Radicals feature close lying multiple electronic states. • Quasi-degeneracy causes the breakdown of the standard hierarchy of SR-methods. • IVO-SSMRPT describe quantitatively the energy gaps of the states of interest. • Order of the states can be tuned by using suitable substituents. • IVO-SSMRPT is nearly as accurate as established methods. Abstract The effect of substituents on the electronic states ordering in trimethylenemethane and m -xylylene diradicals, has been studied at the quantitative level through the estimations of separate individual state energies and the gap between them using our computationally economical perturbative ab initio method directed at describing one specific state, in contrast to multistate treatments. To provide reliable and chemically accurate estimates for energy differences between multiple states of different nature appropriate computational protocol is needed which is built on a democratic and consistent description of target electronic states of different spin-multiplicity. As the energy gap between electronic states of the radicals treated here is relatively small, order of the states can be tuned by using suitable substituents. Our present estimates are well supported by the experimental findings. Present work may serve as a guide for the study of similarly large radicaloid systems for which the use of wavefunction methods becomes challenging. [ABSTRACT FROM AUTHOR]

Abstract: We report the synthesis of biomass‐derived functionalized aromatic chemicals from furfural, a building block nowadays available in large scale from low‐cost biomass. The scientific strategy relies on a Diels–Alder/aromatization sequence. By controlling the rate of each step, it was possible to produce exclusively the meta aromatic isomer. In particular, through this route, we describe the synthesis of renewably sourced meta‐xylylenediamine (MXD). Transposition of this work to other furfural‐derived chemicals is also discussed and reveals that functionalized biomass‐derived aromatics (benzaldehyde, benzylamine, etc.) can be potentially produced, according to this route. [ABSTRACT FROM AUTHOR]

New cyclophanes containing two imidazole-2-thione moieties linked by two xylylene groups have been synthesized by the reaction of imidazolium-linked cyclophanes with sulfur in the presence of K 2 CO 3 . The conformational behaviour of the new cyclophanes was explored by NMR spectroscopy and X-ray diffraction studies. In cyclophanes containing o -xylylene or 2,4,6-trimethyl- m -xylylene linking groups, the imidazole-2-thione groups were mutually syn in both the solid state and in solution, the cyclophanes adopting a conformation reminiscent of the cone conformation of calix[4]arenes. Cyclophanes containing p -xylylene or m -xylylene linking groups exhibited two conformations in solution, one in which the imidazole-2-thione groups are mutually syn , the other in which they are mutually anti , and these conformations did not interconvert on the NMR timescale. Both conformations co-crystallised in the m -xylylene linked cyclophane, while for the p -xylylene-linked cyclophane the anti conformation crystallised separately. [ABSTRACT FROM AUTHOR]

The polymerization kinetics of chloro- p -xylylene in condensed state was studied by in situ non-isothermal DSC measurements conducted at different heating rates in the range from 1.1 to 6.3 °C min −1 , using a custom-made heat-flux calorimeter integrated into a vacuum vapor deposition polymerization reactor. The total exothermal effect of polymerization reaction ( Q  = 71 ± 9 kJ mol −1 ) and its temperature range (−140 to −80 °C) were determined. The differential isoconversional method by Friedman was applied for the kinetics analysis. The effective activation energy increases monotonically with the degree of conversion from about 36 to 55 kJ mol −1 . Such behavior was associated with transition to diffusion-limited regime of the polymerization reaction. The reaction model f ( α ) was evaluated using a model-free method based on the use of the compensation effect. The calculated f ( α ) values were independent on the heating rate and correspond to the second-order reaction model f ( α ) = (1 −  α ) 2 in the conversion degrees interval of 30–90%. [ABSTRACT FROM AUTHOR]

Abstract: Diquats with extremely high racemization barriers with ΔG≠theor of 233 kJ mol−1 at 180 °C are described. Reported configurational robustness is due to a combination of two structural features: the rigid o‐xylylene tether connecting the nitrogen atoms and the presence of two substituents in the bay region of the bipyridinium scaffold. The straightforward synthesis of diquats, plus facile resolution and derivatization make them attractive for chiral application studies. This is demonstrated by: 1) synthesis of the first non‐racemic diquat dyes with pronounced chiroptical properties, and 2) capability of diquats to interact stereospecifically with chiral molecules. This suggests potential for diquat derivatives to be used as chiral selectors in separation methods. [ABSTRACT FROM AUTHOR]

Lithiation of the calix[6]arene methyl ether 2 followed by reaction with O2 yields derivatives with two opposite methylene groups hydroxylated. Calix[6]arenes with two opposite bridges functionalized with alkoxy, azido, and m-xylyl groups were prepared via reaction of a dichlorocalix[6]arene derivative with nucleophiles. [ABSTRACT FROM AUTHOR]

Poly(o-xylylene) (POX) has long been a challenging synthetic target despite its simple structure and potentially useful physical properties. In this report, we demonstrate a valence isomer strategy that leads to the formation of high molecular weight POX via an intermediate polymer of a unique structure, namely poly(Dewar-o-xylylene) (PDOX). We show that the free radical polymerization of highly strained Dewar-o-xylylene (DOX) monomer afforded PDOX, a material with a high density of Dewar benzene units in the backbone through ring-retaining propagation. The thermal- and photoinduced isomerizations of PDOX to produce POX were investigated. This chemistry yields POXs that are difficult to obtain using traditional methods. Moreover, it also provides a potential entry into new reconfigurable materials featuring highly efficient postpolymerization main chain structural transformations. [ABSTRACT FROM AUTHOR]

A 1,2-cis-(α)-selective glycosylation has been developed. An ortho-xylylene group bridged between 3-O and 6-O of D-glucosyl fluoride, which straddles the β-face of the pyranose ring, hinders the approach of glycosyl acceptors from that face. The determination of the three-dimensional structure of the bridged glucosyl fluoride, the optimization process of the reaction conditions oriented toward kinetic control to realize the high α-selectivity, and the scope of the reaction are described. [ABSTRACT FROM AUTHOR]

The relationship between structure, electrical and magnetic properties of thin poly( p -xylylene) - nickel nanocomposite films with Ni concentrations from 5 to 30 vol% was studied. It was found that metal concentration strongly affects size and oxidation state of the nanoparticles and composites morphology. At nickel concentration below 5 vol% the nanoparticles are oxidized to NiO and homogeneously distributed within fine-grained polymer matrix. An increase of Ni concentration up to 10 vol% results in the development of coarse-grained morphology with preferable localization of the nanoparticles at the boundaries of polymeric grains. And finally, in the composite films with nickel concentration above 20 vol%, the fine-grained morphology is observed again, but the nanoparticles are mainly metallic. Effect of the filler content on electrical and magnetic properties of the nanocomposites was elucidated showing that they are determined by percolation phenomenon with the threshold value of about 10 vol%. The well-pronounced magnetic hysteresis as well as ferromagnetic ordering were observed at Ni content above the percolation threshold. The diagrams of magnetic properties of these composites as a function of composition and temperature were elaborated. It was demonstrated that film annealing can be used to control magnetic properties of the composites and strongly enhance magnetoresistance. [ABSTRACT FROM AUTHOR]

The meta-xylylene diradical m-C8H8 is a prototypical organic triplet that represents a building block for organic molecule-based magnets and also serves as a model compound for test and refinement of quantum chemical calculations. Flash vacuum pyrolysis of 1,3-bisiodomethyl- benzene (m-C8H8I2) produces m-C8H8 in gas phase; we used photoelectron spectroscopy to probe the first two electronic states of the radical cation, and resolve the vibrational fine structure of the ground state band. The determined adiabatic ionization energy of m-C8H8 is (7.27 ± 0.01) eV. Heat of formation of the diradical was established measuring C-I bond dissociation thresholds in the precursor cation and utilizing a thermochemical cycle to yield ΔHf,298K = (325 ± 8) kJ mol-1, ca. 10 kJ mol-1 below the previous value. [ABSTRACT FROM AUTHOR]

We report a vapor-phase deposition of poly( p -xylylene) (parylene) membranes for gas separations. Three parylene membranes, poly[(2-chloro- p -xylylene)] (parylene C), poly[(4-amino- p -xylylene)- co -( p -xylylene)] (parylene A), and poly[(2-carboxylic acid N-hydroxysuccinimide ester)- co -( p -xylylene)] (parylene NHS ester), were evaluated. These membranes were deposited on a support of porous poly(vinylidene fluoride) with a dense layer of poly(vinyl alcohol) cast on its top surface. The as-synthesized parylene membranes were characterized by scanning electron microscopy, FT-IR spectroscopy, and the measurements of water contact angle. Single-gas permeation with hydrogen, nitrogen, methane, and carbon dioxide was performed on the parylene membranes for assessing their molecular transport properties. These parylene membranes showed gas permeability of up to hundreds of barrer. To further enhance the gas separation performance of the parylene membranes, polyethylenimine (PEI) was used for modifying the surface of the membranes composed of parylene NHS ester. [ABSTRACT FROM AUTHOR]

Depositing a film via chemical vapor deposition results in superior conformity compared with other deposition techniques, primarily due to the unique chemical interactions between the surface and the reactive compounds. This technique requires a readily accessible surface and so, if the transport of the reactive species is impeded, irrespective of whether this depletion is caused by diffusion or convective flow, a homogeneous layer thickness cannot be achieved. This is often the case when applying films to the interiors of tubes, especially tubes with a dead-end, such that the inevitable loss of film-building components leads to a drop in thickness along the deposition length. The present work examined the deposition of the organic polymer poly-p-xylylene, using a reactor with dimensions that were large compared with the mean free path and tubes in which this factor (the Knudsen number) becomes unity, such that the deposition can be approximately described with the continuum model. A so-called temperature seesaw was employed to mitigate variations in layer thickness by generating an opposing temperature gradient. It was found that, under a vacuum of several tens of mTorr, the polymer could be deposited on the interior wall of a tube with an aspect ratio of at least 100 with an accuracy of ±7.5 %. The true ceiling temperature for the N derivate of this polymer was also determined to be 70 ± 2 °C. [ABSTRACT FROM AUTHOR]

Particle foams and open cell sponges play nowadays an important role in academia and industrial research. The fabrication of new high-performance foams is one of the challenges. Until now, it is impossible to visualise the quality of particle foams, and the quantification is only possible with expensive analytical methods like scanning electron microscopy. In this work, we demonstrate a simple method for the visualisation of void sizes and defects inside particle foams on the basis of expanded polystyrene. The concept was transferred to porous materials, which work as templates for the formation of ultralight poly(para-xylylene) foams with stunning properties. [ABSTRACT FROM AUTHOR]

Photochemical properties of bis(styrylbenzoquinoline) dyads in which two styrylbenzoquinoline (SBQ) moieties are bridged by an o-xylylene group linked to their styryl groups via oxy- and carboxy-functional groups have been studied. Two competitive reactions, photoisomerization of the SBQ moieties and stereoselective [2 + 2] photocycloaddition ( PCA) to give tetrasubstituted cyclobutane, occur under irradiation. It is assumed that PCA occurs with participation of an intramolecular excimer, in which the photochemical process of dimerization to cyclobutane dominates over the photophysical process of fluorescence, because the emission band of the excimer is not observed in an explicit form in the fluorescence spectra of dyads. [ABSTRACT FROM AUTHOR]

Persistent π-radicals such as MV+• (MV refers to methyl viologen, i.e., N,N'-dimethyl-4,4'-bipyridinum) engage in weak radical-radical interactions. This phenomenon has been utilized recently in supramolecular chemistry with the discovery that MV+• and [cyclobis(paraquat-p-phenylene)]2(+•) (CBPQT2(+•)) form a strong 1:1 host-guest complex [CBPQT MV]3(+•). In this full paper, we describe the extension of radical-pairing-based molecular recognition to a larger, square-shaped diradical host, [cyclobis(paraquat-4,4'-biphenylene)]2(+•) (MS2(+•)). This molecular square was evaluated for its ability to bind an isomeric series of possible diradical cyclophane guests, which consist of two radical viologen units that are linked by two ortho-, meta-, or para-xylylene bridges to provide different spacing between the planar radicals. UV-Vis-NIR measurements reveal that only the m-xylylene-linked isomer (m-CBPQT2(+•)) binds strongly inside of MS2(+•), resulting in the formation of a tetraradical complex [MS m-CBPQT]4(+•). Titration experiments and variable temperature UV-Vis-NIR and EPR spectroscopic data indicate that, relative to the smaller trisradical complex [CBPQT MV]3(+•), the new host-guest complex forms with a more favorable enthalpy change that is offset by a greater entropic penalty. As a result, the association constant (Ka = (1.12 ± 0.08) x 105 M-1) for [MSm-CBPQT]4(+•) is similar to that previously determined for [CBPQT MV]3(+•). The (super)structures of MS2(+•), m-CBPQT2(+•), and [MS m-CBPQT]4(+•) were examined by single-crystal X-ray diffraction measurements and density functional theory calculations. The solid-state and computational structural analyses reveal that m-CBPQT2(+•) is ideally sized to bind inside of MS2(+•). The solid-state superstructures also indicate that localized radical-radical interactions in m-CBPQT2(+•) and [MS m-CBPQT]4(+•) disrupt the extended radical-pairing interactions that are common in crystals of other viologen radical cations. Lastly, the formation of [MS m-CBPQT]4(+•) was probed by cyclic voltammetry, demonstrating that the radical states of the cyclophanes are stabilized by the radical-pairing interactions. [ABSTRACT FROM AUTHOR]

Flash vacuum pyrolysis at 600 °C through glass wool coated with freshly sublimed magnesium is examined as a preparative method for dehalogenative coupling in organic synthesis. Substituted benzylidene chlorides give predominantly the corresponding stilbenes and in some cases these are readily isolated in pure form. With an ortho -halogen substituent, additional cyclisation gives phenanthrenes but the method is not compatible with the presence of several reactive groups. An ortho- methoxy substituent leads to unexpected formation of mono- and dimethyl products. With 1,4-bis(dihalomethyl)benzenes, halogenated polymers are deposited directly from the gas phase via generation of halogenated p -xylylenes. The 1,2- and 1,3-isomers lead respectively to benzocyclobutadiene, isolated as a dimer, and to pyrene. The 1,4-bis(trihalomethyl)benzenes give more highly halogenated polymers directly from the gas phase via halogenated p -xylylenes. While halobenzenes generally give the corresponding benzenes and biphenyls, 1,2-dihalobenzenes additionally produce triphenylene in preparatively useful yield by a process not involving intermediacy of free benzyne. [ABSTRACT FROM AUTHOR]

Catheter associated urinary tract infections (CAUTI), caused by several strains of bacteria, are a common complication for catheterized patients. This may eventually lead to a blockage of the catheter due to the formation of a crystalline or amorphous biofilm. Inhibiting bacteria should result in a longer application time free of complaints. This issue has been investigated using an innovative type of silver-coated catheter with a semipermeable cap layer to prevent CAUTI. In this work, two different types of silver catheters were investigated, both of which were capped with poly(p-xylylene) (PPX-N) and exhibited different surface properties that completely changed their wetting conduct with water. The contact angle of conventionally deposited PPX-N is approximately 80°. After O2 plasma treatment, the contact angle drops to approximately 30°. These two systems, Ag/PPX-N and Ag/PPX-N-O2, were tested in synthetic urine at a body temperature of 37 °C. First, the optical density and the inhibition zones of both bacteria strains (Escherichia coli and Staphylococcus cohnii) were examined to confirm the antibacterial effect of these silver-coated catheters. Afterward, the efficacy of silver catheters with different treatments of biofilm formed by E. coli and S. cohnii were tested with crystal violet staining assays. To estimate the life cycles of silver/PPX-catheters, the eluted amount of silver was assessed at several time intervals by anodic stripping voltammetry. The silver catheter with hydrophilic PPX-N coating limited bacterial growth in synthetic urine and prevented biofilm formation. The authors attribute the enhanced bacteriostatic effect to increased silver ion release detected under these conditions. With this extensive preparatory analytic work, the authors studied the ability of the two different cap layers (without silver), PPX-N and oxygen plasma treated PPX-N, to control the growth of a crystalline biofilm by measuring the concentrations of the Ca2+ and Mg2+ ions after exposure of the catheters to saturated urine for 24 h. The higher concentrations of Ca2+ and Mg2+ in the precipitates on the PPX-N catheters indicates that the hydrophilic PPX-N coating is superior to the simple PPX-N coating, with regard to the formation of a crystalline biofilm. Moreover, hydrophilic PPX-N as a cap layer may promote wettability and increase silver ion release rate and thus reduce the adhesion of suspended crystals to the catheter. Reduced bacterial growth and reduced adhesion may help to prevent CAUTI. [ABSTRACT FROM AUTHOR]

The electronic structure of a isomeric series of ruthenophanes containing NHC-cyclophanes derived from imidazolium-linked cyclophanes was studied in the light of energy decomposition analysis and natural bond orbitals. The relative stability, bridge tensions and the metal-ligand bonding situation in a set complexes ( 1 – 9 ) formed by isomers of the i , j -xylylene-linked bis(NHC)cyclophane ligand were determined. Isomers containing aromatic moieties in both anti and syn conformations were evaluated. The relative stability of the isomeric series was evaluate by means of electronic structure calculations at DFT level, including the already synthesized and characterized Baker's complex 1 , which was identified as the most stable, followed by complex 4 . Our calculations reveal that by using as starting material a imidazolium-linked- m , o -cyclophane salt under similar conditions as used by Baker [1], the complex 4 can be likewise obtained. The calculated strain energies imposed on the ligand tether revealed that the strain in NHC-cyclophanes bridges is considerably high. The EDA-NOCV results concerning metal-ligand bonding situation reveal that the stabilization between the cyclophanes and the {RuCl} + fragments is mainly due to the orbital term, followed by the electrostatic interaction. The orbital stabilization is comprised mainly of σ -donation from carbenes to ruthenium(II) ion, which is the most significant contribution, followed by the metal→ligand π -backdonation. [ABSTRACT FROM AUTHOR]

The p-xylylene monomers of parylene N, C and D have similar high polymerization reactivity. For effective copolymerization processes this fact is basically a drawback and for instance the copolymerization with styrene doesn't go at all (Corley et al. J Pol Sc 13(68):137-156, [15]). Substitution of terminal hydrogen atoms by chlorine atoms reduces reactivity dramatically. 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene can be isolated as yellow crystals. These crystals can be kept without any change in temperature below 0 C, but they polymerize slowly at room temperature. Perchloro-p-xylylene is stable even at elevated temperatures and does not polymerize under any conditions. Both 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene copolymerize with various vinyl monomers, such as styrene and others. In this work the polymerization reactions of different chloro-derivatives of p-xylylene were modeled by means of the DFT method with hybrid correlation functionals (B3LYP and PBE0) and, for comparison, by means of the Hartree Fock methods. We inquired both initiation as well as elongation polymeric reactions for each of the reactants. We survied their reactivity analytically examining energetics and configurations in Szwarc-like process. The quantitative influence of chlorine atoms on the reactivity in polymerization steps, their location in the reactants' structure (aromatic and/or aliphatic) as well as their number, were reviewed. The polymerizations of p-xylylenes with chlorine atoms as terminal aliphatic substituents yet revealed one more access path for parylenes' in situ functionalization. [ABSTRACT FROM AUTHOR]

Multifunctional biomaterial surfaces can be created by controlling the competing adsorption of multiple proteins. To demonstrate this concept, bone morphogenetic protein 2 (BMP-2) and fibronectin were adsorbed to the hydrophobic surface of polychloro- para -xylylene. The resulting adsorption properties on the surface depended on the dimensional and steric characteristics of the selected protein molecule, the degree of denaturation of the adsorbed proteins, the associated adsorption of interphase water molecules within the protein layers, and the aggregation of proteins in a planar direction with respect to the adsorbent surface. Additionally, a defined surface composition was formed by the competing adsorption of multiple proteins, and this surface composition was directly linked to the composition of the protein mixture in the solution phase. Although the mechanism of this complex competing adsorption process is not fully understood, the adsorbed proteins were irreversibly adsorbed and were unaffected by the further adsorption of homologous or heterologous proteins. Moreover, synergistic biological activities, including cell osteogenesis and proliferation independently and specifically induced by BMP-2 or fibronectin, were observed on the modified surface, and these biological activities were positively correlated with the surface composition of the multiple adsorbed proteins. These results provide insights and important design parameters for prospective biomaterials and biointerfaces for (multi)functional modifications. The ability to control protein/interface properties will be beneficial for the processing of biomaterials for clinical applications and industrial products. [ABSTRACT FROM AUTHOR]

The polymerization kinetics of p -xylylene in condensed state was studied by in situ non-isothermal DSC measurements, using a custom-made heat-flux calorimeter integrated into a vacuum vapor deposition polymerization reactor. The temperature range (−110 to −75 °C) and the total heat effect ( Q = 86 ± 8 kJ mol −1 ) of the polymerization reaction were found to be almost identical to the values previously measured ex situ with a commercial Perkin Elmer DSC7 calorimeter. The differential isoconversional method by Friedman was applied for the kinetics analysis. The effective activation energy exhibits variation with the degree of conversion in the range from 30 kJ mol −1 to 50 kJ mol −1 indicating the complexity of the reaction mechanism. To evaluate the reaction model f ( α ) a model-free method based on the use of the compensation effect has been employed. The calculated f ( α ) values are adequately fitted to the Avrami–Erofeev A2 model in the conversion degrees interval of 20–80%. The discrepancy observed at the end of the reaction is probably due to diffusion control of the reaction, whereas the complexity of the reaction mechanism can be a reason of the discrepancy at low degrees of conversion. [ABSTRACT FROM AUTHOR]

We report the synthesis of a new asymmetric azacryptand (L1), characterized by three p-xylyl spacers, one of which carries a dansyl side arm. The fluorescent sensor has been studied by potentiometric, UV-Vis, and emission studies in MeOH : water 3 : 2 mixture (0.07 M NaNO3), determining, in particular, the protonation constants of the free ligand and metal ion complexation equilibria. Interestingly, the obtained results revealed that the new receptor is fluorescent at neutral pH with a typical emission band of the dansyl group. Metal addition induced a partial quenching of the dansyl emission band; this behavior is more pronounced with Cu(II) that reduces the receptor’s emission by 60%. With all the studied cations, quenching follows the formation of a dimetallic complex. Similar studies on the model compound L2 confirmed that fluorescence quenching is mainly driven by a static mechanism, attributable to the formation of the inclusion dicopper complex [L1Cu2]4+. In order to test the stability of copper complexes under physiological conditions, spectrofluorimetric titrations with Cu(II) were performed in water buffered at pH = 8 (HEPES 0.07 M) and the values of binding constants, K11 and K12, were determined. [ABSTRACT FROM AUTHOR]

Intramolecular cycloadditions of aza-o-xylylenes generated via excited state intramolecular proton transfer (ESIPT) to furanacetic acid-based unsaturated pendants was shown to overcome the unfavorable energetics of the azetidinone ring formation, offering rapid access to β-lactams as primary photoproducts. These 2,3- and 3,4-dihydrofuran-containing reactive intermediates are suitable for a broad spectrum of postphotochemical transformations yielding complex polyheterocyclic molecular architectures possessing the β-lactam moiety. [ABSTRACT FROM AUTHOR]

Hierarchically structured poly(alkyl- p-xylylene) (alkyl-PPX) nonwovens are prepared by specific parameter variation during the electrospinning process. The investigated parameters are changes in solutions properties and ambient humidity level, which lead to the formation of different fiber architectures and surface morphologies. The characterization of the nonwovens by scanning electron microscopy confirms the formation of hierarchically structured fibers, comprising bead-on-string architecture if spun from tetra­hydrofuran (THF) solutions, and porous surfaces at relative humidity (RH) levels > 30% for both chloroform and THF solutions. The wetting properties of nonwovens spun from THF and chloroform solutions are analyzed by water contact angle (CA) measurements, roll-angle determination, and high speed imaging. PPX-heptyl and PPX-butyl fiber mats spun from 2.5 wt% THF and PPX-heptyl spun from 3 wt% chloroform solutions at RH > 75% show superhydrophobic and self-cleaning properties with CA > 153° and roll-off angles of 10-15°. The nonwovens maintain their fiber morphology and water-repellent properties after thermal and mechanical stress. [ABSTRACT FROM AUTHOR]

A new method was developed for the photoinduced dearomatization of arenes through an intramolecular cycloaddition with aza- o-xylylenes generated by excited-state intramolecular proton transfer (ESIPT) in the readily available photoprecursors. The [2+4] topology of this cycloaddition is unprecedented for photo-dearomatizations of benzenoid aromatic carbocycles. It provides rapid access to novel heterocycles, cyclohexadieno-oxazolidino-quinolinols, as valuable synthons for a broad range of post-photochemical transformations. [ABSTRACT FROM AUTHOR]

A new route has been reported for the synthesis of densely oxygenated polycyclic aromatic compounds via cycloaddition approach. This strategy involves the Dötz benzannulation and Diels-Alder reaction as key steps. Naphthalene synthons required here were generated by Dötz benzannulation between aryl chromium carbene complexes and symmetrical internal alkyne. [ABSTRACT FROM AUTHOR]

A series of o -xylylene-type chiral 1,4-amino alcohols with an aminal structure was synthesized starting from ( S )-2-(arylaminomethyl)pyrrolidine, o -bromobenzaldehyde, and a diaryl ketone. The enantioselective addition of diethylzinc to aldehydes was examined by using the 1,4-amino alcohols, and the corresponding chiral secondary alcohols were obtained with high enantioselectivities (up to 98% ee). [ABSTRACT FROM AUTHOR]

Quantum chemical investigations on symmetrical polyradicals of meta -xylylene chains are done using unrestricted DFT – broken symmetry formalism, to determine whether the polymers are quasi-linear or helical, and their possible magnetic characteristics. As more radical centers are added, successively placed phenyl rings become twisted in the same direction to form a coiled chain. Each polyradical possesses a high-spin ground state with large adiabatic as well as vertical coupling constants. The adiabatic coupling constant exponentially decays with an increasing number of radical centers. Also, the Heisenberg–Dirac–Van Vleck coupling constants are generally large. The polymers are predicted to be very strong paramagnets. [ABSTRACT FROM AUTHOR]

In this study, poly- para -xylylene-based multifunctional nanoparticles (PPX-NPs) were fabricated. Based on the solubility characteristics determined for asymmetrically substituted poly- para -xylylenes in polar solvents, well-dispersed nanocolloids with a controllable size ranging from 50 to 800 nm were produced in solution by the displacement of the solvent (water). These size ranges were found to have acceptable cellular compatibility through examinations of cultured 3T3 fibroblasts and adipose-derived stem cells treated with the PPX-NPs. In addition, these nanoscale PPX-NPs exhibited versatile bioconjugation properties in that a variety of available functional groups can be adopted from their counterpart, thin-film poly- para -xylylenes, during the production of these nanoparticles. For instance, bifunctional PPX-NPs with maleimide and benzoyl moieties were produced to enable immobilization via a maleimide-thiol reaction concurrent with a photochemical reaction. A cleavable PPX-NP was also produced with a thiol-exchangeable surface property. Additionally, by performing electrohydrodynamic jetting of parallel polymer solutions of selected poly- para -xylylenes, Janus-type or multicompartment PPX-NPs were created. The PPX-NPs can potentially be used for various biomedical applications such as combined diagnostics and drug delivery, multiplexing of detection, multiple-drug loading, and the targeted delivery of biomolecules or drugs. [ABSTRACT FROM AUTHOR]

The bottom-up patterning approach provides intrinsic advantages associated with unlimited resolution but is limited by the materials available for selection. A general and simple approach towards the selective deposition of poly-para-xylylenes is introduced in this communication. The chemical vapour deposition (CVD) of poly-para-xylylenes is inhibited on the high-energy surfaces of electrically charged conducting substrates. This technology provides an approach to selectively deposit poly-para-xylylenes irrespective of the substituted functionality and to pattern these polymer thin films from the bottom up. [ABSTRACT FROM AUTHOR]

In this paper, a novel positively charged membrane was prepared through interfacial polymerization technique between polyethyleneimine in aqueous phase and trimesoyl chloride in organic phase. Next, cross-linking of polyamide (PA) layer using ρ-xylylene dichloride (XDC) and glutaraldehyde (GA) was studied. The influences of cross-linking concentrations on the separation and permeation performance of membrane were also investigated. Membranes were characterized in terms of their chemical structure, the cross-sectional and surface morphologies, contact angles, molecular weight cut-off (MWCO) and effect of pH feed solution. The salt rejection sequence of CaCl2 >NaCl>Na2SO4 showed a positive charge at the membrane surface after cross-linking reaction. The MWCO of primary PA membrane decreased from 1,135 to 775 and 885 Da for XDC and GA, respectively. XDC membrane shows highest CaCl2 divalent cationic rejection (95.5%) and lowest water flux (21.1 L/m2.h). This study illustrates a promising method for fabrication of positively charged membrane in cation separation. [ABSTRACT FROM AUTHOR]