The thermal decomposition of a series of lepidocrocite samples has been monitored by means of the Constant Rate Thermal Analysis (CRTA). This method allows controlling the reaction temperature in such a way that both the reaction rate and the partial pressure of the water vapor generated in the reaction are maintained constant at values that can be arbitrarily selected by the user. The final products obtained from the thermal dehydroxylation of the lepidocrocite precursors under residual pressures of water vapor ranging from 5 × 10 -5 mbar to 10 mbar have been characterized by TEM, XRD, and Mo ¨sbauer spectroscopy. It has been concluded that they preserve the shape and size of the corresponding precursors. The precise control of the partial pressure of the water vapor self-generated in the above reaction allows tailoring the internal porosity of the maghemite-hematite mixture obtained as final product. It has been shown that the larger the particle size of the starting lepidocrocite is, the larger the porosity of the iron oxide obtained. The ratio γ-Fe 2 O 3 /R-Fe 2 O 3 is strongly dependent on both the texture of the starting lepidocrocite and the partial pressure of water vapor selected for performing its dehydration. Thus, the percentage of maghemite increases by decreasing the particle size of the starting lepidocrocite and by increasing the residual pressure of water vapor. An interpretation of this behavior is given.

In the present study, the hydrogen-bonded complexes of azole with water and hydrogen peroxide are systematically investigated by second-order Møller–Plesset perturbation theory and density functional theory with dispersion function calculations. This study suggests that the ability of pyrrolic nitrogen (NH) atom to function as hydrogen-bond donor increases with the introduction of nitrogen atoms in the ring, whereas the ability of pyridinic nitrogen (N) atom to act as hydrogen-bond acceptor reduces with successive aza substitution in the ring. With introduction of nitrogen atoms in the ring, the vibrational frequency, stabilization energy, and electron density in the σ antibonding orbitals of the X–H (X = N, C of azole) bond of the complexes all increase or decrease systematically. Decomposition analysis of total stabilization energy showed that the electrostatic energy term is a dominant attractive contribution in comparison to induction and dispersion terms in all of the complexes under study.

The second-order Møller–Plesset perturbation theory (MP2) and density functional theory with dispersion function calculations have been applied to investigate the hydrogen-bonding interaction between azines and water. The study suggests that the ability of nitrogen present in azine to act as a hydrogen-bond acceptor decreases in the order of pyridine ( PY ) > diazine ( DZ ) > triazine ( TZ ) > tetrazine ( TTZ ) > pentazine ( PZ ) > hexazine ( HZ ). Natural bond orbital (NBO) analysis, atoms in molecules, symmetry-adapted perturbation theory (SAPT), and molecular electrostatic potential studies reflect the factors important for hydrogen-bond strength as well as for the structural, electronic, and vibrational changes occurring during complexation. NBO analysis reflects that upon gradual addition of nitrogen atoms, hyperconjugation leads to an increase in the population of antibonding O–H bond, thus causing elongation and weakening of O–H bond in complexes incorporating N···H–O W interaction, whereas rehybridization leads to an increase in the s character of the carbon hybrid orbital in C–H bond, thus causing contraction and shortening of C–H bond in complexes having C–H···O W interactions. From the topological analysis, an excellent linear correlation is found to exist between stabilization energy (Δ E BSSE ), electron density (ρ c ), and its Laplacian (∇ 2 ρ c ) at the bond critical points.