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Vibrational energy redistribution (VER) of energetic materials plays an important role in transferring the injected energy to the hot spots, but it is extremely challenging to understand the mechanism of VER from experimental or theoretical studies. Here, we combined nonequilibrium molecular dynamics with density functional theory to study the processes of VER for solid nitromethane after the selective excitation of the C–H stretching vibration. The VER processes are traced by monitoring the normal-mode kinetic energies of both excited and unexcited vibrations. To explore the underlying VER mechanism, we also analyzed the spectral energy density for the normal mode, obtained from the squared modulus of the short-time Fourier transition of their normal mode momentum. The results showed that the simulated VER progress was reproduced well compared with the previous 3D IR-Raman experiments of liquid nitromethane. Interestingly, the symmetric dependence of the coupling mechanism between the normal modes has been found. [ABSTRACT FROM AUTHOR]

As security needs have increased, mechanism investigation has become of high importance in the development of new sensitive and selective chemosensors for chemical explosives. This study details a theoretical investigation of the sensing mechanism of a new phosphonate pyrene chemosensor for trinitrotoluene (TNT), suggesting a different interaction mode between the probe and TNT from the one previously reported. The invalidity of the mechanism of binding TNT through intermolecular hydrogen bonds was proved using the Gibbs free energy profile and 1H NMR analysis. Frontier molecular orbitals (FMOs) analysis was used to show that photo-induced electron transfer (PET) is the underlying mechanism behind the luminescence quenching of the probe upon exposure to TNT, the rationality of which was further confirmed by the recording of a high charge transfer rate. We also found the existence of an energy level crossing between the local excited (LE) state and charge transfer (CT) state of a complex of the probe and TNT, which was confirmed using energy profile calculations along the linearly interpolated internal coordinate (LIIC) pathway. [ABSTRACT FROM AUTHOR]

A series of novel light-harvesting compounds (namely PO–PN, PO–PO–PN and PO–PO–PO–PN) were synthesized with a linear-shaped phenoxy group-substituted perylenetetracarboxylic diimide (PO) oligomer as donor and a pyrrolidinyl group-substituted perylenetetracarboxylic diimide (PN) as acceptor. The photophysical properties of these linear-shaped compounds are investigated by steady state electronic absorption, fluorescence spectra and lifetime measurements. The ground state interactions between the neighbor PO subunits within these three compounds are weak. No matter which PO subunit is excited in these linear molecules, the excitation energy is finally collected by the PN subunit. The excitation energy can transfer as long as 47 Å without any decrease in efficiency. The energy transfer rate constants determined by femtosecond transient absorption experiments are fast and close to that of the energy transfer from B800 to B850 in LH II of natural photosynthesis. [ABSTRACT FROM AUTHOR]

Nowadays, thousands of energetic materials have been synthesized, but only a few compounds meet all the high standards of detonation performance comparable to that of the widely used military explosive RDX, thermal stability comparable to that of the most widely used heat-resistant explosive HNS, and impact sensitivity comparable to that of the traditional explosive TNT. Also, as a goal, a novel and unexpected one-step method for constructing the furoxan-bridged energetic compound 3,4-bis(3,8-dinitropyrazolo[5,1- c ][1,2,4]triazin-4-amino-7-yl)-1,2,5-oxadiazole 2-oxide (OTF) has been achieved under the conventional TFA/100% HNO 3 nitration reaction system from the acetic acid intermediate. In this work, OTF with a high density of 1.90 g cm -3 , the highest decomposition temperature of 310 °C (onset) among furoxan-based high explosives to date, superior detonation velocity ( D V : 9109 m s -1 ), and low sensitivity (IS: 25 J) is reported. This work is a giant step forward in the development of advanced high-energy heat-resistant explosives and could improve future possibilities for the design of furoxan-based energetic materials.

We report the enzyme-like reversible amination of four intermediates pertinent to the reductive tricarboxylic acid cycle on a photo-irradiated surface of mineral sphalerite (ZnS). Given its prevalence in the waters of early Earth, we suggest that the mineral-based photochemistry might have catalyzed the homeostasis of prebiotic metabolic systems., (This journal is © The Royal Society of Chemistry 2012)

Ultrathin films with noncentrosymmetrically orientated azobenzene chromophores were constructed using a combination of layer-by-layer adsorption of polyelectrolytes and the surface sol-gel process.