Tubular conjugated polymer for chemosensory applications

In this paper, we present the concept of a soluble tubular conjugated polymer (TCP). We report on a fluorescent 5,5'-Bicalixarene-based polymer where the calixarene units are seamlessly incorporated in the conjugated polymeric chain that can respond to a small molecule complexation inside the hydrophobic cavity. In particular, our system demonstrated a reversible rapid fluorescence quenching upon interaction of gaseous nitric oxide with the calixarene moiety.     

Fluorescent Calixarene Scaffolds for NO Detection in Protic Media

We present the first fluorescent water‐soluble conjugated calixarene scaffolds that are capable of NO gas detection. Two different scaffolds, one based on a 5,5′‐bicalixarene structure and its isomer bearing two distantly conjugated calixarene moieties, were synthesized. While the fluorescence of both isomers is quenched upon either passing of NO gas or generating it in situ from diethylamine NONOate, the bicalixarene‐based scaffold showed a significantly stronger response. We also present an example of a dye encapsulation strategy to achieve the detection of NO at longer wavelengths than in the parent calixarene host. Finally, a conjugated polymer bearing a 5,5′‐bicalixarene scaffold has also been prepared and demonstrated enhanced sensitivity compared to the monomer due to the molecular wire effect.     

Insertion of nano-crystalline cellulose into epoxy resin via resilin to construct a novel elastic adhesive

Development of high-performance bio-nanocomposite adhesives is of high interest due to their environmentally friendly nature and superior mechanical properties in outdoor environments. Nano-crystalline cellulose (NCC) and resilin are among the most promising bio-nanofillers, providing strength and elasticity, respectively. A novel bio-nanocomposite comprised of NCC and resilin fused to a cellulose binding domain (Res.-CBD) is presented. As a case study, commercial epoxy adhesive was chosen as a matrix for the bio-nanocomposite adhesive. Insertion of hydrophilic NCC into hydrophobic resins, such as epoxy, is typically performed using solvent exchange, chemical modification, emulsifier addition or mixing with water-borne resins, techniques which either limit the material’s application range or which are considered environmentally unfriendly. The unique approach presented here employed Res.-CBD as a surfactant-like agent supportive of the direct insertion of water-suspended NCC into an epoxy resin. The presented approach involves binding of Res.-CBD to NCC through its CBD domain and a chemical reaction between the resin epoxide groups and Res.-CBD amine moieties. The resulting bio-nano material shows a 50 % increase in the Young’s modulus and a 20 % decrease in the tan(δ), compared to pristine epoxy. This novel epoxy adhesive can be advantageous in applications where higher elasticity and Young’s modulus are required.     

Metal-mediated formation of carbon-halogen bonds

Organic halides represent basic starting materials for numerous metal-catalyzed organic transformations. Generally, the carbon-halogen is broken in the first step, that is, an oxidative addition reaction, of the catalytic cycle. On the other hand, very little is known about the reverse reaction, carbon-halogen reductive elimination from a transition-metal center. In this Concept article, we describe the examples of C(sp(3))-halide and C(sp(2))-halide reductive-elimination reactions which demonstrate that this type of reactivity can be quite common in organometallic chemistry. Although the thermodynamic driving force for the formation of carbon-halogen bonds is relatively small, the kinetic barrier for these reactions can also be low. Thus, C-halide reductive elimination can compete favorably with the more established organic transformations, such as C-C reductive elimination.     

Competitive aryl-iodide vs aryl-aryl reductive elimination reactions in Pt(IV) complexes: experimental and theoretical studies

The platinum(IV) complex trans-(dmpe)Pt(IV)(Ar)2I2 (2, dmpe = 1,2-dimethylphosphinoethane, Ar = 4-FC6H4) rapidly reacts, upon moderate heating in solution under ambient light, via two distinct pathways: isomerization to the corresponding cis-isomer (3) and Ar-I reductive elimination to give (dmpe)Pt(II)(Ar)I (4). Complex 3 undergoes, upon prolonged heating at high temperatures, an exclusive Ar-Ar reductive elimination reaction to give (dmpe)Pt(II)I2. Experimental and DFT studies showed that the 2-to-3 isomerization proceeds via three pathways: photochemical or thermal phosphine chelate opening and a mechanism involving cleavage of the Pt-I bond. The isomerization reaction is significantly slowed down but not stopped in the absence of light or in the presence of an excess of tetra-n-butylammonium iodide. On the other hand, the Ar-I reductive elimination from 2 proceeds via the Pt(delta+)-I(delta-) ion pairlike transition state. Use of the rigid dmpe analogue 1,2-dimethylphosphinobenzene (dmpbz) as the ligand shuts down the chelate ring-opening isomerization pathway and enables faster Ar-I reductive elimination thus making the latter reaction the major reaction route for the dmpbz supported trans-diiodo Pt(IV) complex 8.     

Xenon difluoride induced aryl iodide reductive elimination: a simple access to difluoropalladium(II) complexes

Palladium(II) aryliodo complexes bearing chelating diphosphine ligands react with XeF2, giving iodoarene and rare palladium(II) difluoro complexes. The reaction is general with regard to the aryl group, with even C6F5-I undergoing facile reductive elimination from a Pd center.     

Some limitations on optical communication reliability through Kolmogorov and non-Kolmogorov turbulence

In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received signal, affecting link performance.Influence of Kolmogorov and non-Kolmogorov turbulence statistics on laser communication links are analyzed for different propagation scenarios, and effects of different turbulence spectrum models on optical communication links are presented. Statistical estimates of the communication parameters such as the probability of fade (miss) exceeding a threshold dB level, the mean number of fades, and BER are derived and examples provided. The presented quantitative data suggest that the non-Kolmogorov turbulence effects on lasercom channels are more severe in many situations and need to be taken into account in wireless optical communication. Non-Kolmogorov turbulence is especially important for elevations above the boundary layer as well as for even low elevation paths over water.     

On the non-emptiness of the fuzzy core

The seminal contribution of Debreu and Scarf (Int Econ Rev 4:235–246, 1963) connects the two concepts of core and competitive equilibrium in exchange economies. In effect, their core-equilibrium equivalence result states that, when the set of economic agents is replicated, the set of core allocations of the replica economy shrinks to the set of competitive allocations. Florenzano (J Math Anal Appl 153:18–36, 1990) defines the fuzzy core as the set of allocations which cannot be blocked by any coalition with an arbitrary rate of participation and then shows the asymptotic limit of cores of replica economies coincides with the fuzzy core. In this note, we provide an elementary proof of the non-emptiness of the fuzzy core for an exchange economy. Hence, in motivation, our result is similar to the contribution of Vohra (On Scarf’s theorem on the non-emptiness of the core: a direct proof through Kakutani’s fixed point theorem. Brown University Working Paper, 1987) and Shapley and Vohra (Econ Theory 1:108–116, 1991) for the core. Unlike the classical Debreu–Scarf limit theorem (Debreu and Scarf in Int Econ Rev 4:235–246, 1963) and its numerous extensions our result does not require any asymptotic intersection—or limit—of the set of core allocations of replica economies. The author would like to thank the Netherlands Organisation for Scientific Research (NWO) for financial support.