Thermodynamic stability of solid phases in the system Cu–O–Al2O3 by means of the EMF and DSC-TGA techniques

Journal of Solid State Electrochemistry - Thermodynamic properties of solid phases in the Cu–O–Al2O3 system were measured by means of the EMF method with oxygen concentration galvanic...     

Common Structural Elements in the Chromophore Binding Pocket of the Pfr State of Bathy Phytochromes

Phytochromes are bimodal photoreceptors which, upon light absorption by the tetrapyrrole chromophore, can be converted between a red‐absorbing state (Pr) and far‐red‐absorbing state (Pfr). In bacterial phytochromes, either Pr or Pfr are the thermally stable states, thereby constituting the classes of prototypical and bathy phytochromes, respectively. In this work, we have employed vibrational spectroscopies to elucidate the origin of the thermal stability of the Pfr states in bathy phytochromes. Here, we present the first detailed spectroscopic analysis of RpBphP6 (Rhodopseudomas palustris), which together with results obtained for Agp2 (Agrobacterium tumefaciens) and PaBphP (Pseudomonas aeruginosa) allows identifying common structural properties of the Pfr state of bathy phytochromes, which are (1) a homogenous chromophore structure, (2) the protonated ring C propionic side chain of the chromophore and (3) a retarded H/D exchange at the ring D nitrogen. These properties are related to the unique strength of the hydrogen bonding interactions between the ring D N‐H group with the side chain of the conserved Asp194 (PaBphP numbering). As revealed by a comparative analysis of homology models and available crystal structures of Pfr states, these interactions are strengthened by an Arg residue (Arg453) only in bathy but not in prototypical phytochromes.     

The Graovac–Pisanski index of zig-zag tubulenes and the generalized cut method

The Graovac–Pisanski index, which is also called the modified Wiener index, was introduced in 1991 by Graovac and Pisanski. This variation of the classical Wiener index takes into account the symmetries of a graph. In 2016 Ghorbani and Klav?ar calculated this index by using the cut method, which we generalize in this paper. Moreover, we prove that in some cases the automorphism group of a zig-zag tubulene is isomorphic to the direct product of a dihedral group and a cyclic group. Finally, the closed formulas for the Graovac–Pisanski index of zig-zag tubulenes are calculated.     

A Self‐Improved Water‐Oxidation Catalyst: Is One Site Really Enough?

The homogeneous catalysis of water oxidation by transition‐metal complexes has experienced spectacular development over the last five years. Practical energy‐conversion schemes, however, require robust catalysts with large turnover frequencies. Herein we introduce a new oxidatively rugged and powerful dinuclear water‐oxidation catalyst that is generated by self‐assembly from a mononuclear catalyst during the catalytic process. Our kinetic and DFT computational analysis shows that two interconnected catalytic cycles coexist while the mononuclear system is slowly and irreversibly converted into the more stable dinuclear system: an extremely robust water‐oxidation catalyst that does not decompose over extended periods of time.     

Synthesis and Characterization of the New Heterocycle 5‐(4‐Amino‐1,2,4‐triazol‐3‐on‐5′‐yl)‐1H‐tetrazole and Some Ionic Nitrogen‐Rich Derivatives

A new heterocycle consisting of a tetrazole ring attached to an amino‐triazolone ring, namely 5‐(4‐amino‐1,2,4‐triazol‐3‐on‐5′‐yl)‐1H‐tetrazole ( 3 ) as well as its ammonium ( 2 ), hydroxylammonium ( 3 ), and sodium salt ( 4 ), is introduced. Its ammonium salt ( 2 ) is formed starting from tetrazole‐5‐carboxamide oxime ( 1 ), which is reacted with diaminourea (carbonyldihydrazide) in aqueous media. All compounds 2 , 3 , 4 , 5 were structurally characterized by single crystal X‐ray diffraction. The thermal behavior was investigated using differential scanning calorimetry, and the sensitivities towards impact, friction, and electrostatic discharge were determined. Furthermore, several detonation parameters were calculated with the program EXPLO5 to determine the potential use of these compounds as highly energetic materials.