http://www.sciencemadness.org/talk/files.php?pid=302583&aid=26587

Azole-based energetic salts.

Key parameters that influence the specific energy of electrochemical double-layer capacitors (EDLCs) are the double-layer capacitance and the operating potential of the cell. The operating potential of the cell is generally limited by the electrochemical window of the electrolyte solution, that is, the range of applied voltages within which the electrolyte or solvent is not reduced or oxidized. Ionic liquids are of interest as electrolytes for EDLCs because they offer relatively wide potential windows. Here, we provide a systematic study of the influence of the physical properties of ionic liquid electrolytes on the electrochemical stability and electrochemical performance (double-layer capacitance, specific energy) of EDLCs that employ a mesoporous carbon model electrode with uniform, highly interconnected mesopores (3DOm carbon). Several ionic liquids with structurally diverse anions (tetrafluoroborate, trifluoromethanesulfonate, trifluoromethanesulfonimide) and cations (imidazolium, ammonium, pyridinium, piperidinium, and pyrrolidinium) were investigated. We show that the cation size has a significant effect on the electrolyte viscosity and conductivity, as well as the capacitance of EDLCs. Imidazolium- and pyridinium-based ionic liquids provide the highest cell capacitance, and ammonium-based ionic liquids offer potential windows much larger than imidazolium and pyridinium ionic liquids. Increasing the chain length of the alkyl substituents in 1-alkyl-3-methylimidazolium trifluoromethanesulfonimide does not widen the potential window of the ionic liquid. We identified the ionic liquids that maximize the specific energies of EDLCs through the combined effects of their potential windows and the double-layer capacitance. The highest specific energies are obtained with ionic liquid electrolytes that possess moderate electrochemical stability, small ionic volumes, low viscosity, and hence high conductivity, the best performing ionic liquid tested being 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

Ionic Liquids as Electrolytes for Electrochemical Double-Layer Capacitors: Structures that Optimize Specific Energy.

Metal–organic frameworks, particularly those coordinated with nitrogen-rich ligands, are extremely versatile materials. Here the structural factors and performances of 1D and 2D energetic MOFs are compared briefly with those of 3D species. Advantages of hydrothermal in situ synthesis, properties of azole-based ligands, and choices of environmentally friendly metal ions for 3D energetic MOFs are also explored.

3D Nitrogen-rich metal–organic frameworks: opportunities for safer energetics

Eight new metal coordination complexes, namely, [Co(BTA)2(H2O)4]·6H2O (1), [Ni(BTA)2(H2O)4]·6H2O (2), [Cu2(HBTA)4(BTA)2]·2H2O (3), [Ag(BTA)(H2O)]n (4), [Zn(BTA)2(H2O)]n (5), [Cd(BTA)2(H2O)]n (6), [Cu2(μ3-OH)(BTA)3]n (7), and [Mn(BTA)2(H2O)2]n (8) [HBTA = 2-(1H-benzotriazol-1-yl)acetic acid], were obtained under hydrothermal conditions, by reacting the different metal salts with HBTA. The ligand HBTA was characterized by melting point (m.p.), elemental analysis (EA), infrared spectroscopy (IR), 1H NMR, and X-ray single-crystal diffraction. Complexes 1–8 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes all display low-dimensional features displaying various zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) coordination motifs. Complexes 1 and 2 are isostructural and mononuclear; they show unique decamer water clusters with bis-boat conformations, which further extend to a 1D metal–water chain. Through intermolecular hydrogen bonds, these 1D metal–water chains extend to 3D supramolecular networks. Complex 3 shows a bi-nuclear structure. Complex 4 displays a 1D tape structure. There exist weak interactions between Ag⋯Ag. Complexes 5 and 6 form a 1D linear chain bridged by BTA anions. Complex 7 exhibits a 2D layer containing tetranuclear butterfly [Cu4(CO2)4(μ3-OH)] secondary building units (SBUs). Complex 8 possesses a 2D layer and further stacks via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 3, 4, 5, and 6. Complexes 3, 5 and 6 display blue photoluminescence. However, complex 4 exhibits green fluorescence. Variable-temperature magnetic susceptibility measurements reveal the existence of antiferromagnetic interactions in both 7 and 8. Additionally, the ferroelectric and second-harmonic generation (SHG) properties of 5 are discussed in detail.

/pdf/metal-directed-assembly-of-coordination-polymers-with-the-4id5g20lzq.pdf

Metal-directed assembly of coordination polymers with the versatile ligand 2-(1H-benzotriazol-1-yl) acetic acid: from discrete structures to two-dimensional networks

Twenty-two chemical reaction pathways of thermal decomposition of 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf, CF 3 CF CH 2 ) are proposed to investigate the formation mechanism of some possible products (CF 3 H, CF 4 , HF, H 2 ) by using density function theory (DFT) simulations with M06-2X/6–311++(d,p) level of theory The results point out that the ground state CF 3 CF CH 2 will excite into the lowest triplet state CF 3 CF-CH 2 favorably in the first step with an energy barrier of 26467 kJ mol −1 and pathway 5 is the most preferred route of homolytic cleavage reactions with the lowest energy barrier of 20570 kJ mol -1  F radical is hard to generate during thermal decomposition processes because of its higher energy barrier H radical and CF 3 radical play a dominant role in thermal decomposition of HFO-1234yf H-abstraction and F-abstraction reactions are proposed in subsequent radical attacking chain reactions CF 3 H and H 2 are easier to be generated due to their lower energy barriers Our work presents the mechanism of thermal decomposition of HFO-1234yf from the molecule level and provides a reference for studying the thermal stability of other working fluids

Mechanism of thermal decomposition of HFO-1234yf by DFT study

The present study deals with the decomposition of CF3OCF2O radical formed from a hydrofluoroether, CF3OCHF2 (HFE-125), in the atmosphere. The study is performed using ab initio quantum mechanical methods. Two plausible pathways of decomposition of the titled species have been considered, one involving C-O bond scission and the other occurring via F atom elimination. The geometries of the reactant, products and transition states involved in the decomposition pathways are optimized and characterized at DFT (B3LYP) level of theory using 6-311G(d,p) basis set. Single point energy calculations have been performed at G2M(CC,MP2) level of theory. Out of the two prominent decomposition channels considered, the C-O bond scission is found to be dominant involving a barrier height of 15.3 kcal mol−1 whereas the F-elimination path proceeds with a barrier of 26.1 kcal mol−1. The thermal rate constants for the above two decomposition pathways are evaluated using canonical transition state theory (CTST) and these are found to be 1.78 × 106 s−1 and 2.83 × 10−7 s−1 for C-O bond scission and F-elimination respectively at 298 K and 1 atm pressure. Transition states are searched on the potential energy surfaces involved during the decomposition channels and each of the transition states is characterized. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation.

Ab initio studies on the decomposition kinetics of CF3OCF2O radical.

A computational perspective on mechanism and kinetics of the reactions of CF3C(O)OCH2CF3 with OH radicals and Cl atoms at 298 K

Hydrofluoroethers are being considered as potential candidates for third generation refrigerants. The present investigation involves the ab initio quantum mechanical study of the decomposition mechanism of CF3OCH2O radical formed from a hydrofluoroether, CF3OCH3 (HFE-143a) in the atmosphere. The geometries of the reactant, products and transition states involved in the decomposition pathways are optimized and characterized at the DFT (B3LYP) level of theory using 6-311G(d,p) basis set. Energy calculations have been performed at the G2(MP2) and G2M(CC,MP2) level of theory. Two prominent decomposition channels, C-O bond scission and reaction with atmospheric O2 have been considered for detailed investigation. Studies performed at the G2(MP2) level reveals that the decomposition channel involving C-O bond scission occurs with a barrier height of 23.8 kcal mol−1 whereas the oxidative pathway occurring with O2 proceeds with an energy barrier of 7.2 kcal mol−1. On the other hand the corresponding values at G2M(CC,MP2) are 24.5 and 5.9 kcal mol−1 respectively. Using canonical transition state theory (CTST) rate constants for the two pathways considered are calculated at 298 K and 1 atm pressure and found to be 5.9 × 10−6 s−1 and 2.3 × 10−5 s−1 respectively. The present study concludes that reaction with O2 is the dominant path for the consumption of CF3OCH2O in the atmosphere. Transition states are searched and characterized on the potential energy surfaces involved in both of the reaction channels. The existence of transition state on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation.

Ab initio studies on the reactivity of the CF3OCH2O radical: Thermal decomposition vs. reaction with O2

The unimolecular decomposition reaction of CF3CCl2O radical has been investigated using theoretical methods. Two most important channels of decomposition occurring via C–C bond scission and Cl elimination have been considered during the present investigation. Ab initio quantum mechanical calculations are performed to get optimized structure and vibrational frequencies at DFT and MP2 levels of theory. Energetics are further refined by the application of a modified Gaussian-2 method, G2M(CC,MP2). The thermal rate constants for the decomposition reactions involved are evaluated using Canonical Transition State Theory (CTST) utilizing the ab initio data. Rate constants for C–C bond scission and Cl elimination are found to be 6.7 × 106 and 1.1 × 108 s−1, respectively, at 298 K and 1 atm pressure with an energy barrier of 8.6 and 6.5 kcal/mol, respectively. These values suggest that Cl elimination is the dominant process during the decomposition of the CF3CCl2O radical. Transition states are searched on the potential energy surface of the decomposition reactions involved and are characterized by the existence of only one imaginary frequency (NIMAG = 1) during frequency calculation. The existence of transition states on the corresponding potential energy surface is further ascertained by performing intrinsic reaction coordinate (IRC) calculation.

Theoretical studies of decomposition kinetics of CF3CCl2O radical

The reaction of 3,5-diphenylpyrazole (PzPh2H) with different inorganic acids affords salts viz., PzPh2H2+·H2PO4− (1), PzPh2H2+·NO3−·H2O (2), PzPh2H2+·Cl− (3), 8PzPh2H2+·4HSO4−·2SO4−2·3H2O (4) and PzPh2H2+·ClO4−·H2O·CH3OH (5) with different structures. The present study demonstrates that the formation of hydrogen bond between protonated pyrazoles and anions provides a sufficient driving force for the directed assembly of an extensive supramolecular frame work. Theoretical studies reveal that with the increase in the strength of the inorganic acid, the hydrogen bond interaction energy increases. Using Gaussview to analyse the optimized geometries obtained at DFT(B3LYP)/6-31G(d,p) level of theory further revealed that the orientation of molecules remained the same both in the solid and gaseous phases.

Hari Ji Singh

Papers

Ab initio studies on the decomposition kinetics of CF3OCF2O radical.

A computational perspective on mechanism and kinetics of the reactions of CF3C(O)OCH2CF3 with OH radicals and Cl atoms at 298 K

Ab initio studies on the reactivity of the CF3OCH2O radical: Thermal decomposition vs. reaction with O2

Theoretical studies of decomposition kinetics of CF3CCl2O radical

Anion directed supramolecular architecture of pyrazole based ionic salts