Click chemistry meets polymerization: Controlled incorporation of an easily accessible ruthenium(II) complex into a PMMA backbone via RAFT copolymerization

The copper(I)-catalyzed azide-alkyne cycloaddition provided an easy and efficient access to a functionalized heteroleptic ruthenium(II) complex monomer. A grafted copolymer with the heteroleptic ruthenium(II) complex and methyl methacrylate (MMA) as comonomer was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The product was characterized by means of ¹H NMR spectroscopy, UV/vis spectroscopy and size exclusion chromatography coupled with a photodiode array detector. The RAFT process itself led to a grafted copolymer with a low polydispersity index.     

Quantitative analysis of graded Cu(In1−x,Gax)Se2 thin films by AES, ICP-OES, and EPMA

The overall composition and the compositional profile of the quaternary semiconductor Cu(In_1−x,Ga_x)Se₂ (CIGS) have strong effects on the performance of photovoltaic devices based on it. Recent work that has yielded ∼20% efficient solar cells based on CIGS has forced extra attention on quantitative analysis of the absorber layers. In this paper we present details of the procedures used to generate detailed compositional profiles of graded Cu(In_1−x,Ga_x)Se₂ thin films by Auger electron spectroscopy (AES) that when integrated, agree quantitatively with inductively-coupled plasma optical emission spectrometry (ICP-OES) data on the same films. The effects of sample rotation during sputter depth profiling on the quantification results are described. Details of the procedures used for the ICP-OES and wavelength-dispersed electron probe microanalysis (EPMA) analyses are also presented. Finally, we show why X-ray microanalysis techniques alone should not be used to argue that specific windows of copper and gallium concentrations can yield high performance devices.     

Prediction of Carbon Dioxide Adsorption via Deep Learning

Porous carbons with different textural properties exhibit great differences in CO₂ adsorption capacity. It is generally known that narrow micropores contribute to higher CO₂ adsorption capacity. However, it is still unclear what role each variable in the textural properties plays in CO₂ adsorption. Herein, a deep neural network is trained as a generative model to direct the relationship between CO₂ adsorption of porous carbons and corresponding textural properties. The trained neural network is further employed as an implicit model to estimate its ability to predict the CO₂ adsorption capacity of unknown porous carbons. Interestingly, the practical CO₂ adsorption amounts are in good agreement with predicted values using surface area, micropore and mesopore volumes as the input values simultaneously. This unprecedented deep learning neural network (DNN) approach, a type of machine learning algorithm, exhibits great potential to predict gas adsorption and guide the development of next‐generation carbons.     

Self-gravitating static non-critical black holes in 4<Emphasis Type="Italic">D</Emphasis> Einstein–Klein–Gordon system with nonminimal derivative coupling

We study static non-critical hairy black holes of four dimensional gravitational model with nonminimal derivative coupling and a scalar potential turned on. By taking an ansatz, namely, the first derivative of the scalar field is proportional to square root of a metric function, we reduce the Einstein field equation and the scalar field equation of motions into a single highly nonlinear differential equation. This setup implies that the hair is secondary-like since the scalar charge-like depends on the non-constant mass-like quantity in the asymptotic limit. Then, we show that near boundaries the solution is not the critical point of the scalar potential and the effective geometries become spaces of constant scalar curvature.     

Efficient Cu(I) acetate‐catalyzed cycloaddition of multifunctional alkynes and azides: From solution to bulk polymerization

“Click” chemistry is an effective and commonly used technique in polymer chemistry for the synthesis and modification of polymers. In this study, the bulk polymerization of multifunctional alkynes and azides was achieved by the copper(I)‐catalyzed alkyne–azide 1,3‐dipolar cycloaddition. The influence of different catalyst systems on the polymerization kinetics of the “click”reaction were evaluated by differential scanning calorimetry. Surprisingly, Cu(I) acetate showed the most efficient catalytic behavior among the applied Cu(I) salts. The polymerization kinetics in solution were investigated by 1H NMR spectroscopy and size exclusion chromatography. According to the 1H NMR investigation the copper(I)‐catalyzed cycloaddition follows a second‐order kinetics with external catalysis. Additionally, the mechanical properties of the resulting polymers were investigated by depth sensing indentation. Thereby the polymerizations of the alkyne tripropargylamine with the azides 1,3‐bis(azidomethyl)benzene and 1,4‐bis(azidomethyl)benzene resulted in mechanical hard materials. Furthermore, the combination of the alkynes tripropargylamine and di(prop‐2‐yn‐1‐yl) isophorone dicarbamate and polymerization with 1,2‐bis(2‐azidoethoxy)ethane resulted in high indentation moduli. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 239–247     

Computational study of the structure, dynamics, and photophysical properties of conjugated polymers and oligomers under nanoscale confinement

Computational simulations were used to investigate the dynamics and resulting structures of several para-phenylenevinylene (PPV) based polymers and oligomers (PPV, 2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene --> MEH-PPV and 2,5,2',5'-tetrahexyloxy-7,8'-dicyano-p-phenylenevinylene --> CN-PPV). The results show how the morphology and structure are controlled to a large extent by the nature of the solute-solvent interactions in the initial solution-phase preparation. Secondary structural organization is induced by using the solution-phase structures to generate solvent-free single molecule nanoparticles. Isolation of these single molecule nanostructures from microdroplets of dilute solution results in the formation of electrostatically oriented nanostructures at a glass surface. Our structural modeling suggests that these oriented nanostructures consist of folded PPV conjugated segments with folds occurring at tetrahedral defects (sp3 C-C bonds) within the polymer chain. This picture is supported by detailed experimental fluorescence and scanning probe microscopy studies. We also present results from a fully quantum theoretical treatment of these systems which support the general conclusion of structure-mediated photophysical properties.     

Regioselective palladium-catalyzed arylation of 3-carboalkoxy furan and thiophene

[reaction: see text] The regioselective palladium(0)-catalyzed arylation of 3-furoate and 3-thiophenecarboxylate esters with aryl bromides is described. Conditions were developed that allow for the selective synthesis of either 2-aryl or 5-aryl products.     

Synthesis, characterization, and physicochemical properties of manganese(III) and manganese(V)-oxo corrolazines

The structural and physicochemical properties of the manganese-corrolazine (Cz) complexes (TBP8Cz)Mn(V)O (1) and (TBP8Cz)Mn(III) (2) (TBP = p-tert-butylphenyl) have been determined. Recrystallization of 2 from toluene/MeOH resulted in the crystal structure of (TBP8Cz)Mn(III)(CH3OH) (2 x MeOH). The packing diagram of 2 x MeOH reveals hydrogen bonds between MeOH axial ligands and meso N atoms of adjacent molecules. Solution binding studies of 2 with different axial ligands (Cl-, Et3PO, and Ph3PO) reveal strong binding, corroborating the preference of the Mn(III) ion for a five-coordinate environment. High-frequency and field electron paramagnetic resonance (HFEPR) spectroscopy of solid 2 x MeOH shows that 2 x MeOH is best described as a high-spin (S = 2) Mn(III) complex with zero-field splitting parameters typical of corroles. Structural information on 1 was obtained through an X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure (EXAFS) study and compared to XANES/EXAFS data for 2 x MeOH. The XANES data for 1 shows an intense pre-edge transition characteristic of a high-valent metal-oxo species, and a best fit of the EXAFS data gives a short Mn-O bond distance of 1.56 A, confirming the structure of the metal-oxo unit in 1. Detailed spectroelectrochemical studies of 1 and 2 were performed revealing multiple reversible redox processes for both complexes, including a relatively low potential for the Mn(V) --> Mn(IV) process in 1 (near 0.0 V vs saturated calomel reference electrode). Chemical reduction of 1 results in the formation of a Mn(III)Mn(IV)(mu-O) dimer as characterized by electron paramagnetic resonance spectroscopy.     

Univalent transition metal complexes of arenes stabilized by a bulky terphenyl ligand: differences in the stability of Cr(I), Mn(I) or Fe(I) complexes

Two univalent transition metal complexes, (micro-eta6:eta6-C7H8){MnAr*-3,5-Pri2}2 () and (eta6-C6H6)FeAr*-3,5-Pri2 () (Ar*-3,5-Pri2=C6H-2,6-(C6H(2)-2,4,6-Pri3)(2)-3,5-Pri2), that have eta6 arene coordination were synthesized by reduction of the corresponding metal halides. The complexes are thermally stable in contrast to the corresponding Cri complexes of benzene or toluene which decompose at room temperature.