Synthesis,crystal structure,sensitivity, and effect on thermal decomposition of ammonium perchlorate: an energetic compound Cu(HATZ)(PDA)(H2O)

An energetic coordination compound, Cu(HATZ)(PDA)(H₂O) (HATZ?=?5-aminotetrazole, H₂PDA?=?pyridine-2,6-dicarboxylic acid), has been synthesized and structurally characterized by single crystal X-ray diffraction. Copper(II) was coordinated by two oxygen atoms and nitrogen from PDA, one ring nitrogen of ATZ and one water to form a five-coordinate, distorted square-pyramidal structure. 3-D supramolecular architecture was formed by hydrogen bonding. Thermal decomposition of the compound was examined by DSC and TG-DTG analyses. The kinetic parameters of the first exothermic process of the compound were studied by Kissinger's and Ozawa–Doyle's methods. Sensitivity tests revealed that the compound was insensitive to mechanical stimuli. In addition, the compound was explored as additive to promote thermal decomposition of ammonium perchlorate by differential scanning calorimetry.     

A Zn(II)-Coordination Polymer Formed by Benzoate and 3-Pyridinemethanol Ligands: Synthesis,Spectroscopic Properties,Crystal Structure and Kinetics of Thermal Decomposition

The complex catena-poly[bis(benzoato-O)-bis(3-pyridinemethanol-N,O)-zinc(II)], [Zn(benz)₂(3-pymeth)₂] _n was prepared and characterised by elemental analysis, IR spectroscopy, thermal analysis and an X-ray structure determination. Zinc is octahedrally coordinated. Two coordination sites are occupied by oxygen atoms of two monodentate benzoate groups, two by the nitrogen atoms of 3-pyridinemethanol, and two by methanolic oxygen atoms of 3-pyridinemethanol from neighbouring structural units. Due to the bridging 3-pyridinemethanol ligand, molecules of the complex are connected into infinite chains along the c axis. The bridging function is reflected in the IR spectrum by a very sharp absorption band due to the stretching vibration of the methanolic O–H group. Non-isothermal kinetics of the thermal decomposition were studied using the model-free isoconversional method. Based on isoconversional dependencies, a multi-step mechanism with parallel reactions was recognised for the decomposition of the complex.     

Reaction of Amino Acids,Di‐ and Tripeptides with the Environmental Oxidant NO3.: A Laser Flash Photolysis and Computational Study

Absolute rate coefficients for the reaction between the important environmental free radical oxidant NO₃^. and a series of N‐ and C‐protected amino acids, di‐ and tripeptides were determined using 355 nm laser flash photolysis of cerium(IV) ammonium nitrate in the presence of the respective substrates in acetonitrile at 298±1 K. Through combination with computational studies it was revealed that the reaction with acyclic aliphatic amino acids proceeds through hydrogen abstraction from the α‐carbon, which is associated with a rate coefficient of about 1.8×10⁶ m ^?1 s^?1 per abstractable hydrogen atom. The considerably faster reaction with phenylalanine [k=(1.1±0.1)×10⁷ m ^?1 s^?1] is indicative for a mechanism involving electron transfer. An unprecedented amplification of the rate coefficient by a factor of 7–20 was found with di‐ and tripeptides that contain more than one phenylalanine residue. This suggests a synergistic effect between two aromatic rings in close vicinity, which makes such peptide sequences highly vulnerable to oxidative damage by this major environmental pollutant.     

Design of a Highly Active Pd Catalyst with P,N Hemilabile Ligands for Alkoxycarbonylation of Alkynes and Allenes: A Density Functional Theory Study

In the palladium-catalysed methoxycarbonylation of technical propyne, the presence of propadiene poisons the hemilabile Pd(P,N) catalyst. According to density functional theory calculations (B3PW91-D3/PCM level), a highly stable π-allyl intermediate is the reason for this catalyst poisoning. Predicted regioselectivities suggest that at least 11 % of propadiene should yield this allyl intermediate, in which the reaction gets stalled under the turnover conditions due to an insurmountable methanolysis barrier of 25.8 kcal mol⁻¹. The results obtained for different ligands and substrates are consistent with the available experimental data. A new ligand, (6-Cl-3-Me-Py)PPh₂, is proposed, which is predicted to efficiently control the branched/linear selectivity, avoiding rapid poisoning (with only 0.2 % of propadiene being trapped as the Pd allyl complex), and to tremendously increase the catalytic activity by decreasing the overall barrier to 9.1 kcal mol⁻¹.     

A comprehensive theoretical study on the reactions of Sc+ with CnH2n+2 (n=1-3): structure,mechanism, and potential-energy surface

The reactions of Sc(+)((3)D) with methane, ethane, and propane in the gas phase were studied theoretically by density functional theory. The potential energy surfaces corresponding to [Sc, C(n), H(2n+2)](+) (n=1-3) were examined in detail at the B3LYP/6-311++G(3df, 3pd)//B3LYP/6-311+G(d,p) level of theory. The performance of this theoretical method was calibrated with respect to the available thermochemical data. Calculations indicated that the reactions of Sc(+) with alkanes are multichannel processes which involve two general mechanisms: an addition-elimination mechanism, which is in good agreement with the general mechanism proposed from earlier experiments, and a concerted mechanism, which is presented for the first time in this work. The addition-elimination reactions are favorable at low energy, and the concerted reactions could be alternative pathways at high energy. In most cases, the energetic bottleneck in the addition-elimination mechanism is the initial C--C or C--H activation. The loss of CH(4) and/or C(2)H(6) from Sc(+)+C(n)H(2n+2) (n=2, 3) can proceed along both the initial C--C activation branch and the Cbond;H activation branch. The loss of H(2) from Sc(+)+C(n)H(2n+2) (n=2, 3) can proceed not only by 1,2-H(2) and/or 1,3-H(2) elimination, but also by 1,1-H(2) elimination. The reactivity of Sc(+) with alkanes is compared with those reported earlier for the reactions of the late first-row transition-metal ions with alkanes.