Physical mechanisms responsible for the water-induced degradation of PC61BM P3HT photovoltaic thin films

We show that [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM) at the surface of thin film blends of poly(3-hexylthiophene) (P3HT):PC₆₁BM can be patterned by water. Using a series of heating and cooling steps, water droplets condense onto the blend film surface. This is possible due to the liquid-like, water swollen layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. Breath pattern water deformation and subsequent drying on the film surface results in isolated PC₆₁BM structures, showing that migration of PC₆₁BM takes place. This was confirmed by selective wavelength illumination to spatially map the photoluminescence from the P3HT and PC₆₁BM. Within a device, redistribution of the surface PC₆₁BM into aggregates would be catastrophic, as it would markedly alter device performance. We also postulate that repeated volume change of the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate layer by water swelling may be, in part, responsible for the delamination failure mechanism in thin film solar cells devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 141–146     

Electronic modification of an aminotroponiminate zinc complex leading to an increased reactivity in the hydroamination of alkenes

The electronically modified zinc complex 5-phenylsulfanyl-N-isopropyl-2-(isopropylamino)troponiminate zinc methyl, [(PhS-ATI(iPr)2)ZnMe], was synthesized. It showed an increased reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to a previously-reported, non-substituted complex.     

Anion Storage Chemistry of Organic Cathodes for High-Energy and High-Power Density Divalent Metal Batteries

Multivalent batteries show promising prospects for next-generation sustainable energy storage applications. Herein, we report a polytriphenylamine (PTPAn) composite cathode capable of highly reversible storage of tetrakis(hexafluoroisopropyloxy) borate [B(hfip)₄] anions in both Magnesium (Mg) and calcium (Ca) battery systems. Spectroscopic and computational studies reveal the redox reaction mechanism of the PTPAn cathode material. The Mg and Ca cells exhibit a cell voltage >3 V, a high-power density of ∼∼3000 W kg⁻¹ and a high-energy density of ∼∼300 Wh kg⁻¹, respectively. Moreover, the combination of the PTPAn cathode with a calcium-tin (Ca−Sn) alloy anode could enable a long battery-life of 3000 cycles with a capacity retention of 60 %. The anion storage chemistry associated with dual-ion electrochemical concept demonstrates a new feasible pathway towards high-performance divalent ion batteries.     

Catalytic Alkyne Semihydrogenation with Polyhydride Ni/Ga Clusters

The bimetallic, decanuclear Ni₃Ga₇-cluster of the formula [Ni₃(GaTMP)₃(μ²-GaTMP)₃(μ³-GaTMP)] ( 1 , TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2 . Low-temperature 2D NMR experiments at −80 °C show that 2 consist of a mixture of a di- ( 2_Di ), tetra- ( 2_Tetra ) and hexahydride species ( 2_Hexa ). The structures of 2_Di and 2_Tetra are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis.     

Pyridyl‐Endcapped Polyynes: Stabilized Wire‐like Molecules

A 4‐ethynylpyridyl derivative with sterically shielding phenyl groups in the 3‐ and 5‐positions has been synthesized and used to terminate a series of polyynes. This approach allows for the synthesis of stable polyynes up to an octayne, twice as long as previous accessible for “unstabilized” pyridyl‐endcapped polyynes. The potential of these polyynes as wire‐like linkers to metal centers is demonstrated by axial coordination of pyridyl groups to zinc‐ and ruthenium‐metalloporphyrins.     

Double-bridge bonding of aluminium and hydrogen in the crystal structure of gamma-AlH3

Aluminum trihydride (alane) is one of the most promising among the prospective solid hydrogen-storage materials, with a high gravimetric and volumetric density of hydrogen. In the present work, the alane, crystallizing in the gamma-AlH3 polymorphic modification, was synthesized and then structurally characterized by means of synchrotron X-ray powder diffraction. This study revealed that gamma-AlH3 crystallizes with an orthorhombic unit cell (space group Pnnm, a = 5.3806(1) A, b = 7.3555(2) A, c = 5.77509(5) A). The crystal structure of gamma-AlH3 contains two types of AlH6 octahedra as the building blocks. The Al-H bond distances in the structure vary in the range of 1.66-1.79 A. A prominent feature of the crystal structure is the formation of the bifurcated double-bridge bonds, Al-2H-Al, in addition to the normal bridge bonds, Al-H-Al. This former feature has not been previously reported for Al-containing hydrides so far. The geometry of the double-bridge bond shows formation of short Al-Al (2.606 A) and Al-H (1.68-1.70 A) bonds compared to the Al-Al distances in Al metal (2.86 A) and Al-H distances for Al atoms involved in the formation of normal bridge bonds (1.769-1.784 A). The crystal structure of gamma-AlH3 contains large cavities between the AlH6 octahedra. As a consequence, the density is 11% less than for alpha-AlH3.     

On the Role of the Excitation/Inhibition Balance of Homeostatic Artificial Neural Networks

Homeostatic models of artificial neural networks have been developed to explain the self-organization of a stable dynamical connectivity between the neurons of the net. These models are typically two-population models, with excitatory and inhibitory cells. In these models, connectivity is a means to regulate cell activity, and in consequence, intracellular calcium levels towards a desired target level. The excitation/inhibition (E/I) balance is usually set to 80:20, a value characteristic for cortical cell distributions. We study the behavior of these homeostatic models outside of the physiological range of the E/I balance, and we find a pronounced bifurcation at about the physiological value of this balance. Lower inhibition values lead to sparsely connected networks. At a certain threshold value, the neurons develop a reasonably connected network that can fulfill the homeostasis criteria in a stable way. Beyond the threshold, the behavior of the artificial neural network changes drastically, with failing homeostasis and in consequence with an exploding number of connections. While the exact value of the balance at the bifurcation point is subject to the parameters of the model, the existence of this bifurcation might explain the stability of a certain E/I balance across a wide range of biological neural networks. Assuming that this class of models describes the self-organization of biological network connectivity reasonably realistically, the omnipresent physiological balance might represent a case of self-organized criticality in order to obtain a good connectivity while allowing for a stable intracellular calcium homeostasis.     

Catalytic Asymmetric Cycloaddition of Ketenes and Nitroso Compounds: Enantioselective Synthesis of α‐Hydroxycarboxylic Acid Derivatives

The appropriate choice of chiral catalyst and starting materials leads to the synthesis of 1,2‐oxazetidin‐3‐ones by cycloadditions of ketenes with nitroso compounds with very good regioselectivity and enantioselectivity. In addition to serving as potentially bioactive target molecules, the products can be transformed into other important classes of compounds, such as α‐hydroxycarboxylic acid derivatives.