A Raman technique applicable for the analysis of the working principle of promoters and inhibitors of gas hydrate formation

We report a Raman technique applicable for the in situ analysis of the development of hydrogen bonds in the liquid water‐rich phase just before the onset of gas hydrate formation. Herewith, the phase transition as well as the working principle of hydrate formation inhibitors and promoters can be analyzed. © 2015 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.     

Random k‐SAT and the power of two choices

We study an Achlioptas‐process version of the random k‐SAT process: a bounded number of k‐clauses are drawn uniformly at random at each step, and exactly one added to the growing formula according to a particular rule. We prove the existence of a rule that shifts the satisfiability threshold. This extends a well‐studied area of probabilistic combinatorics (Achlioptas processes) to random CSP's. In particular, while a rule to delay the 2‐SAT threshold was known previously, this is the first proof of a rule to shift the threshold of k‐SAT for . We then propose a gap decision problem based upon this semi‐random model. The aim of the problem is to investigate the hardness of the random k‐SAT decision problem, as opposed to the problem of finding an assignment or certificate of unsatisfiability. Finally, we discuss connections to the study of Achlioptas random graph processes. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 163–173, 2015     

Thermally Activated Delayed Fluorescence in a Y3N@C80 Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

The endohedral fullerene Y₃N@C₈₀ exhibits luminescence with reasonable quantum yield and extraordinary long lifetime. By variable‐temperature steady‐state and time‐resolved luminescence spectroscopy, it is demonstrated that above 60 K the Y₃N@C₈₀ exhibits thermally activated delayed fluorescence with maximum emission at 120 K and a negligible prompt fluorescence. Below 60 K, a phosphorescence with a lifetime of 192±1 ms is observed. Spin distribution and dynamics in the triplet excited state is investigated with X‐ and W‐band EPR and ENDOR spectroscopies and DFT computations. Finally, electroluminescence of the Y₃N@C₈₀/PFO film is demonstrated opening the possibility for red‐emitting fullerene‐based organic light‐emitting diodes (OLEDs).     

A di‐tert‐butyl acrylate monomer for controlled radical photopolymerization

A new di‐tert‐butyl acrylate (diTBA) monomer for controlled radical polymerization is reported. This monomer complements the classical use of tert‐butyl acrylate (TBA) for synthesis of poly(acrylic acid) by increasing the density of carboxylic acids per repeat unit, while also increasing the flexibility of the carboxylic acid side‐chains. The monomer is well behaved under Cu(II)‐mediated photoinduced controlled radical polymerization and delivers polymers with excellent chain‐end fidelity at high monomer conversions. Importantly, this new diTBA monomer readily copolymerizes with TBA to further the potential for applications in areas such as dispersing agents and adsorbents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 801–807     

A short,highly efficient synthesis of coenzyme Q(10)

The most efficient synthesis reported to date of ubiquinone (CoQ10) is described. A sequence consisting of six operations is involved which leads to crystalline material in an overall yield of >64%.     

Liquid-phase EPR, ENDOR, and TRIPLE resonance studies on corrole and isocorrole cation radicals

The “Contracted Porphyrins” corrole and the recently synthesized isocorrole (as octaethyl derivatives) represent novel porphyrinoid macrocycles of biochemical interest. The radical cations of the free-bases of both corrole and its isomer are studied by EPR, ENDOR, and TRIPLE resonance in liquid solution to measure isotropic hyperfine couplings including signs. They yield detailed information of the electronic structure of the radical cations. The experimental findings are compared with results of all-valence-electrons self-consistent field molecular orbital calculations (RHF-INDO/SP). The comparison shows that the free-bases of corrole and isocorrole undergo protonation when oxidized to cation radicals in CH₂Cl₂ solution. Excellent agreement of the measured and calculated spin density distributions is achieved for the protonated dication radicals, which exhibit the C₂ symmetry observed for the hyperfine structure. The analysis of the hyperfine data discriminates against NH tautomerism as the sole source for an effective C₂ symmetry of the macrocycle.     

Shape change and fast M1 transitions in Kr

A shape transition from a probably asymmetric shape at low excitation to a more axial-symmetric shape above 21/2⁺ has been found in ⁸¹Kr. This shape change and the drastic increase of the M1 transition probabilities above spin 21/2 are attributed to the alignment of two g_9/2 protons.