A Mixed-ligand Zn(II)-based Coordination Polymer for Selectively Detect 2,4,6-Trinitrophenol (TNP) and Treatment Effect on Periodontal Diseases via Inhibition Effect on P. gingivalis Growth.

A new difunctional Zn(II) coordination polymer (CP) with the chemical formula of [Zn(TBTA) (L)1.5]n (1) has been synthesized hydrothermally from tetrabromoterephthalic acid (H2TBTA) and 4,4'-bis(imidazole-1-yl)-biphenyl (L) ligands. Furthermore, due to its strong intense emission and open N donor sites, complex 1 could be used as a light-emitting sensor to determine 2,4,6-trinitrophenol (TNP) which has high selectivity and sensitivity. Furthermore, the anti-bacterial effect of the compound against P. gingivalis in vitro was evaluated by measuring the P. gingivalis growth curves after compound treatment. And the RT-PCR assay was performed to detect the relative expression of ragA and ragB, which are important for the P. gingivalis growth. The potential anti-infectious mechanism was further studied by using molecular docking technique.

A Photophysical Deactivation Channel of Laser-Excited TATB Based on Semiclassical Dynamics Simulation and TD-DFT Calculation.

A deactivation channel for laser-excited 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) was studied by semiclassical dynamics. Results indicate that the excited state resulting from an electronic transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular mrbital (LUMO) is deactivated via pyramidalization of the activated N atom in a nitro group, with a lifetime of 2.4 ps. An approximately 0.5-electron transfer from the aromatic ring to the activated nitro group led to a significant increase of the C⁻NO2 bond length, which suggests that C⁻NO2 bond breaking could be a trigger for an explosive reaction. The time-dependent density functional theory (TD-DFT) method was used to calculate the energies of the ground and S1 excited states for each configuration in the simulated trajectory. The S1←S0 energy gap at the instance of non-adiabatic decay was found to be 0.096 eV, suggesting that the decay geometry is close to the conical intersection.

Experimental determination of solvent-water partition coefficients and Abraham parameters for munition constituents.

There is concern about the environmental fate and effects of munition constituents (MCs). Polyparameter linear free energy relationships (pp-LFERs) that employ Abraham solute parameters can aid in evaluating the risk of MCs to the environment. However, poor predictions using pp-LFERs and ABSOLV estimated Abraham solute parameters are found for some key physico-chemical properties. In this work, the Abraham solute parameters are determined using experimental partition coefficients in various solvent-water systems. The compounds investigated include hexahydro-1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX), hexahydro-1,3-dinitroso-5- nitro-1,3,5-triazine (DNX), 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), and 4-nitroanisole. The solvents in the solvent-water systems are hexane, dichloromethane, trichloromethane, octanol, and toluene. The only available reported solvent-water partition coefficients are for octanol-water for some of the investigated compounds and they are in good agreement with the experimental measurements from this study. Solvent-water partition coefficients fitted using experimentally derived solute parameters from this study have significantly smaller root mean square errors (RMSE = 0.38) than predictions using ABSOLV estimated solute parameters (RMSE = 3.56) for the investigated compounds. Additionally, the predictions for various physico-chemical properties using the experimentally derived solute parameters agree with available literature reported values with prediction errors within 0.79 log units except for water solubility of RDX and HMX with errors of 1.48 and 2.16 log units respectively. However, predictions using ABSOLV estimated solute parameters have larger prediction errors of up to 7.68 log units. This large discrepancy is probably due to the missing R2NNO2 and R2NNO2 functional groups in the ABSOLV fragment database.

Determination of the ATP Affinity of the Sarcoplasmic Reticulum Ca(2+)-ATPase by Competitive Inhibition of [γ-(32)P]TNP-8N3-ATP Photolabeling.

The photoactivation of aryl azides is commonly employed as a means to covalently attach cross-linking and labeling reagents to proteins, facilitated by the high reactivity of the resultant aryl nitrenes with amino groups present in the protein side chains. We have developed a simple and reliable assay for the determination of the ATP binding affinity of native or recombinant sarcoplasmic reticulum Ca(2+)-ATPase, taking advantage of the specific photolabeling of Lys(492) in the Ca(2+)-ATPase by [γ-(32)P]2',3'-O-(2,4,6-trinitrophenyl)-8-azido-adenosine 5'-triphosphate ([γ-(32)P]TNP-8N3-ATP) and the competitive inhibition by ATP of the photolabeling reaction. The method allows determination of the ATP affinity of Ca(2+)-ATPase mutants expressed in mammalian cell culture in amounts too minute for conventional equilibrium binding studies. Here, we describe the synthesis and purification of the [γ-(32)P]TNP-8N3-ATP photolabel, as well as its application in ATP affinity measurements.

Solid polymer substrates and coated fibers containing 2,4,6-trinitrobenzene motifs as smart labels for the visual detection of biogenic amine vapors.

Attempts to polymerize trinitrobenzene derivatives (TNB) have been fruitless so far. Accordingly, polymers containing TNB have not been exploited in spite of their envisaged potential applications. Here, we describe two ways for preparing polymers with TNB moieties thus overcoming the previously reported polymerization impairments. We also report on the exploitation of the materials, both obtained as tractable transparent films and coated fibers, as smart labels for the visual detection of amine vapors. More precisely, amines in the atmosphere surrounding the sensory materials diffuse into them reacting with the TNB motifs forming highly colored Meisenheimer complexes, giving rise to development of color and to the naked eye sensing phenomenon. This is the case of highly volatile amines, such as trimethylamine, produced in food spoilage, specifically in the deterioration of fish or meat, for which the color development of the smart labels can be used as a visual test for food freshness.

Quantum chemical studies on three novel 1,2,4-triazole N-oxides as potential insensitive high explosives.

Three novel explosives were designed by introducing N-oxides into 1,2,4-triazole: 1-amino-3,5-dinitro-1,2,4-triazole-2 N-oxide (ADT2NO), 1-amino-2,5-dinitro-1,2,4-triazole-3 N-oxide (ADT3NO), and 1-amino-3,5-dinitro-1,2,4-triazole-4 N-oxide (ADT4NO). Their detonation performance and sensitivity were estimated by using density functional theory and compared with some famous explosives like 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and 1-methyl-2,4,6-trinitrobenzene (TNT). All three designed molecules are more powerful than HMX and less sensitive than TNT, indicating that ADT2NO, ADT3NO, and ADT4NO have high detonation performance as HMX and low sensitivity as TNT, making them being very valuable and may be considered as the potential candidates of insensitive high explosives. Properly introducing N-oxides into the energetic triazole derivatives can generate some superior energetic compounds with both high explosive performance and reduced sensitivity.

4-Fluoro-3-nitrophenyl grafted gold electrode based platform for label free electrochemical detection of interleukin-2 protein.

A new platform based on 4-Fluoro-3-nitrophenyl (FNP) grafted gold disk electrode prepared via electrochemical reduction of 4-fluoro-3-nitrobenzene diazonium ion has been developed and utilized for biosensor fabrication. Anti-interleukin-2 (anti-IL2) antibody has been covalently immobilized onto FNP/Au surface and utilized for label free electrochemical impedance based detection of cytokine IL2. FNP acts as a bridge (cross-linker) between gold surface and anti-IL2, where fluoro group of FNP undergoes nucleophilic substitution by amino group of biomolecule and results in its covalent immobilization. The immobilization process and fabricated electrode have been characterized using contact angle (CA) measurements, cyclic voltammetry (CV) and electrochemical impedance (EIS) technique. CV studies show that FNP grafted surface provides conductive surface for anti-IL2 immobilization. The EIS response of studies as a function of IL2 concentrations exhibits a detection in linear range from 1 pg ml(-1) to 10 ng ml(-1) with minimum detectable concentration of 1 pg ml(-1). The electrode has been found to be selective against other cytokine molecules.

Sensing of hydrophobic cavity of serum albumin by an adenosine analogue: fluorescence correlation and ensemble spectroscopic studies.

Adenosine is a naturally occurring purine nucleoside that plays important role in various biochemical processes. We have studied the binding of TNP-Ado (trinitrophenylated-adenosine), a fluorescent analogue of adenosine (which itself is a weak fluorophore), with a model transport protein, bovine serum albumin (BSA). The binding affinity was determined using Fluorescence correlation spectroscopy (FCS) and compared with its value obtained from macroscopic fluorescence spectroscopic studies. Fluorescence and circular dichroism (CD) spectroscopies were employed together with molecular docking study to locate the probable binding site of TNP-Ado on BSA and its effect on the conformation and stability of BSA. Fluorescence studies showed that TNP-Ado binds to BSA in 1:1 stoichiometry via an entropically favoured process. Induced CD spectra revealed that a chiro-optical switching of TNP-Ado occurs upon binding to BSA. Results on urea-induced denaturation of BSA and docking study suggested that the binding site for the ligand is in the hydrophobic subdomain IIA of BSA, consistent with the results of other measurements. This study establishes TNP-Ado as a sensor of hydrophobic regions in proteins like serum albumin, having the capability of detecting a minimum concentration of 140ng/ml protein. FCS measurement of binding interaction of rhodamine-labeled TNP-Ado (RTNP-Ado) with BSA yielded an association constant of KFCS=(1.03±0.06) × 10(4)M(-1). The association constants (Ka) obtained for binding of BSA with rhodamine-free (i.e. TNP-Ado) and rhodamine-labeled (RTNP-Ado) ligands, obtained using the ensemble spectroscopic technique, were (2.3±0.06) × 10(5)M(-1) and (3.4±0.03) × 10(4)M(-1), respectively. The difference between the values of Ka for the free and labeled ligands suggests that fluorescent labeling of small molecules perceptibly interferes with the binding process. On the other hand, the difference in Ka obtained by FCS and ensemble techniques is due to the fact that while the former measures the change in the diffusion constant (i.e. size) of RTNP-Ado upon binding to BSA, the latter focuses on the change of tryptophan emission properties of BSA due to the presence of bound RTNP-Ado.

Theoretical determination of anisotropic thermal conductivity for crystalline 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).

Bond stretching and three-center angle bending potentials have been developed to extend an existing rigid-bond 1,3,5-triamino-2,4,6-trinitrobenzene molecular dynamics force field [D. Bedrov, O. Borodin, G. D. Smith, T. D. Sewell, D. M. Dattelbaum, and L. L. Stevens, J. Chem. Phys. 131, 224703 (2009)] for simulations requiring fully flexible molecules. The potentials were fit to experimental vibrational spectra and electronic structure predictions of vibrational normal modes using a combination of zero kelvin eigenmode analysis for the isolated molecule and power spectra for the isolated molecule and crystal. A reverse non-equilibrium molecular dynamics method [F. Müller-Plathe, J. Chem. Phys. 106, 6082 (1997)] was used to obtain the room temperature, atmospheric pressure thermal conductivity along three directions in a well-defined, non-orthogonal basis. The thermal conductivity was found to be significantly anisotropic with values 1.13 ± 0.07, 1.07 ± 0.07, and 0.65 ± 0.03 W m(-1) K(-1) for directions nominally parallel to the a, b, and c lattice vectors, respectively.

IR vibrational assignments for 1,3,5-triamine-2,4,6-trinitrobenzene (TATB) based on the temperature-dependent frequency shifts.

IR spectra of TATB at different temperature were investigated for vibrational assignments. The results showed that the hydrogen bonding interaction of TATB was significantly weakened with increasing the temperature. Based on the frequency shifts of the hydrogen bonding interaction to several vibrational modes, 12 absorbance bands in the region 600-1700 cm(-1) were assigned to corresponding vibrational modes. In addition, Fermi resonance effect between NO2 and NH2 scissors was observed, and the enhancement of Fermi resonance effect caused the intensity of v3 (at 1545 cm(-1)) to grow during heating.

Nanoscale effect on thermal decomposition kinetics of organic particles: dynamic vacuum stability test of 1,3,5-triamino-2,4,6-trinitrobenzene.

Despite the extensive research that has been carried out on organic nanoparticles, little explanation has been provided for the reasons behind their exceptional properties. In this work, the effect of the particles being on the nanoscale on the thermal decomposition kinetics of organic particles was examined by means of a dynamic vacuum stability test. Nano- and microscale particles of 1,3,5-triamino-2,4,6-trinitrobenzene were measured for comparison. Analysis of the evolved gas revealed that the nanoparticles (NPs) show much higher reaction activity than the microparticles (MPs). Both the non-isothermal and isothermal reaction mechanisms and kinetics were computed. The NPs and MPs exhibit different reaction mechanisms, while similarly sized particles follow different mechanisms for different stages of the reaction. The mechanisms for the NPs are affected by the temperature in the range considered. NPs have larger values for the apparent activation energy (E(a)) and pre-exponential factor (A) than MPs and the relationship of E(a) to A demonstrates that a kinetic compensation effect is evident. The nanoscale effect shows there to be a significant influence on the apparent performances and kinetics as well as on the intrinsic reaction mechanisms of organic particles. This effect can be attributed to the surface properties of NPs, where the high surface area contributes to efficient mass transfer and heat transfer, thus leading to numerous activated molecules being involved in the reaction.

TAML activator/peroxide-catalyzed facile oxidative degradation of the persistent explosives trinitrotoluene and trinitrobenzene in micellar solutions.

TAML activators are well-known for their ability to activate hydrogen peroxide to oxidize persistent pollutants in water. The trinitroaromatic explosives, 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB), are often encountered together as persistent, toxic pollutants. Here we show that an aggressive TAML activator with peroxides boosts the effectiveness of the known surfactant/base promoted breakdown of TNT and transforms the surfactant induced nondestructive binding of base to TNB into an extensive multistep degradation process. Treatment of basic cationic surfactant solutions of either TNT or TNB with TAML/peroxide (hydrogen peroxide and tert-butylhydroperoxide, TBHP) gave complete pollutant removal for both in <1 h with >75% of the nitrogen and ≥20% of the carbon converted to nitrite/nitrate and formate, respectively. For TNT, the TAML advantage is to advance the process toward mineralization. Basic surfactant solutions of TNB gave the colored solutions typical of known Meisenheimer complexes which did not progress to degradation products over many hours. However with added TAML activator, the color was bleached quickly and the TNB starting compound was degraded extensively toward minerals within an hour. A slower surfactant-free TAML activator/peroxide process also degrades TNT/TNB effectively. Thus, TAML/peroxide amplification effectively advances TNT and TNB water treatment giving reason to explore the environmental applicability of the approach.

Coordination-driven switching of a preorganized and cooperative calix[4]pyrrole receptor.

The study of preorganization in receptors, particularly in cooperative receptors, and their reversible control by external stimuli is important for elucidating design strategies that can lead to increased sensitivity and external control of molecular recognition. In this work we present the design, synthesis, and operation of an asymmetric tetrathiafulvalene (TTF)-calix[4]pyrrole receptor appended with a pyridine moiety. (1)H NMR spectroscopy was employed to demonstrate that intramolecular complexation between the receptor and the pyridine moiety leads to a preorganized receptor. Absorption and (1)H NMR spectroscopy along with a computational investigation were used to demonstrate the ability of the receptor to complex the substrate 1,3,5-trinitrobenzene (TNB) and that the receptor can be reversibly modulated between negative and positive cooperativity by employing external stimuli in the form of Zn(II). Fitting procedures incorporating multiple datasets and fitting to multiple equilibria simultaneously have been employed to quantitatively determine the preorganization effects.

Effect of heat treatment on sorption of polar and nonpolar compounds to montmorillonites and soils.

Batch sorption isotherms of 1,3,5-trichlorobenzene, 1,3,5-trinitrobenzene, and tetracycline to organic-free montmorillonites and soils receiving heat treatment (375°C for 24 h) were compared with those to unheated sorbents. Sorption of the nonpolar 1,3,5-trichlorobenzene to soil was lowered after the removal of humus by heating, consistent with the mechanism of hydrophobic partition into organic matter. For 1,3,5-trinitrobenzene, the enhanced sorption to heated soils was attributed to specific interactions with exchangeable cations facilitated by heating-induced irreversible partial dehydration of the clay interlayer. For tetracycline, an additional mechanism for sorption enhancement could be due to increased exposure of strong complexation sites on clay minerals after removal of the humic coating. These hypotheses were supported by the sorption data to heated and unheated Na-, K-, and Cs-saturated montmorillonites. The combustion method is commonly adopted to measure the content of black carbon in soils and sediments. However, findings from the present study indicate that combustion may greatly modify the structural properties of clay minerals, leading to misinterpreted sorption contributions of different soil components to sorption of polar or ionic compounds.

Ultrafast shock compression and shock-induced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene subjected to a subnanosecond-duration shock: an analysis of decomposition products.

Shock compression studies of pressed and confined ultrafine 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) powder were conducted using ultrashort ~300 ps, ~50 GPa shock waves. The recovered decomposition products were characterized using X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. A substantial amount of shock-related chemistry was observed. Approximately 75% of the nitrogen atoms were liberated as gas-phase species, along with ~33% of the oxygen atoms, as a result of the applied shock. Furthermore, we observe C 1s binding energies suggesting the formation of sp(3) hybridized amorphous carbon. For comparison, a carbon nitride material was also prepared and characterized by thermally pyrolizing TATB. The shock-compressed TATB and the thermally pyrolized TATB are qualitatively different, suggesting that, carbon nitrides, a possible indicator of nitrogen-rich heterocycles precursors, are not a major product class for strongly overdriven shock conditions. These experimental conditions were, however, not detonation conditions, and the possible formation of nitrogen-rich heterocycles in actual detonations still exists.

Why is the crystal shape of TATB is so similar to its molecular shape? Understanding by only its root molecule.

We present an understanding of the quasi-regular or regular hexagonal enlargement of 1,3,5-triamino-2,4,6 (TATB) from its root molecule to its bulk crystal, by only its root molecule. That is, the mechanism of regular hexagonal TATB molecules stacking to a quasi-regular or regular hexagonal TATB crystal was discussed using a combined method of a density functional theory BLYP and Dreiding forcefield, and a series of static scanning calculations. As a result, we found that there are two styles of forming the most energetically favored TATB dimers: a hydrogen bonding along the molecular plane and an offset π-stacking vertical to the plane, just leading to the outspread and the thickening of the regular hexagon during the crystal growth, respectively. At the same time, it was found that the rotation of one TATB layer in any parallel stacked double-layer should overcome a very high energy barrier. It suggests that the TATB molecules or layers are arranged on the crystal face always along the special orientation of a regular hexagon and other orientations are strongly thermodynamically forbidden, resulting in a hexagonal crystal bulk.

Theoretical studies on vibrational spectra, thermodynamic properties, detonation properties and pyrolysis mechanism for 1,2-bis(2,4,6-trinitrophenyl) hydrazine.

The thermal stability and pyrolysis mechanism of 1,2-bis(2,4,6-trinitrophenyl) hydrazine were investigated based on fully optimized molecular geometric structures. The results demonstrate the existence of intramolecular hydrogen bond interactions 1,2-bis(2,4,6-trinitrophenyl) hydrazine. The assigned infrared spectrum was also obtained; the results reveal four main characteristic regions in the calculated IR spectra of the title compound. Detonation velocities (D) and pressures (P) were also evaluated by using Kamlet-Jacobs equations based on the calculated density and heat of formation. Thermal stability and the pyrolysis mechanism of 1,2-bis(2,4,6-trinitrophenyl) hydrazine were investigated by calculating the bond dissociation energies at the B3LYP/6-31 G* level.

Self-assembly of dimeric tetrathiafulvalene-calix[4]pyrrole: receptor for 1,3,5-trinitrobenzene.

The synthesis and binding properties of a tetrathiafulvalene (TTF)-calix[4]pyrrole receptor 2 appended with one 3,5-dinitrobenzoate guest moiety are reported. The preliminary studies revealed that the receptor is self-complexing into a dimer receptor 2•2. The self-complexation of the receptor leads to preorganization--in its 1,3-alternate conformation--and as a result hereof, the dimer receptor 2•2 is displaying a 2 order higher binding affinity toward analytes (e.g., 1,3,5-trinitrobenzene) than the model tetrathiafulvalene (TTF)-calix[4]pyrrole receptor 3.

Microscopic calculations of Hugoniot curves of neat triaminotrinitrobenzene (TATB) and of its detonation products.

We compute the Hugoniot curves of both neat triaminotrinitrobenzene (TATB) and its detonation products mixture using atomistic simulation tools. To compute the Hugoniot states, we adapted our sampling constraints in average (SCA) method (Maillet et al. Appl. Math. Res. eXpress 2009, 2008, abn004) to Monte Carlo simulations. For neat TATB, we show that the potential proposed by Rai (Rai et al. J. Chem. Phys. 2008, 129, 194510) is not accurate enough to predict the Hugoniot curve and requires some optimization of its parameters. Concerning the detonation products, thermodynamic properties at chemical equilibrium are computed using a specific reaction ensemble Monte Carlo (RxMC) method (Bourasseau et al. Phys. Chem. Chem. Phys. 2011, 13, 7060), taking into account the presence of carbon clusters in the fluid mixture. We show that this explicit description of the solid phase immersed in the fluid phase modifies the chemical equilibrium.

Acid/base controllable molecular recognition.

The study of controllable molecular recognition in supramolecular receptors is important for elucidating design strategies that can lead to external control of molecular recognition applications. In this work, we present the design and synthesis of an asymmetric (TTF) tetrathiafulvalene-calix[4]pyrrole receptor and show that its recognition of 1,3,5-trinitrobenzene (TNB) can be controlled by an acid/base input. The new receptor is composed of three identical TTF units and a fourth TTF unit appended with a phenol moiety. Investigation of the host-guest complexation taking place between the TTF-calix[4]pyrrole receptor and the TNB guests was studied by means of absorption and (1)H NMR spectroscopy; this revealed that the conformation of the molecular receptor can be switched between locked and unlocked states by using base and acid as the input. In the unlocked state, the receptor is able to accommodate two TNB guest molecules, whereas the guests are not able to bind to the receptor in the locked state. This work serves to illustrate how external control (acid/base) of a receptor may be used to direct the molecular recognition of guests (TNBs). It has led to a new controllable molecular recognition system that functions as an acid/base switch.