Forensic analytical aspects of homemade explosives containing grocery powders and hydrogen peroxide.

Homemade explosives become a significant challenge for forensic scientists and investigators. In addition to well-known materials such as acetone peroxide trimer, black powder, or lead azides, perpetrators often produce more exotic and less recognized Homemade Explosives (HMEs). Mixtures of hydrogen peroxide with liquid fuels are widely acknowledged as powerful explosives. Interestingly, similar explosive properties are found in mixtures of numerous solid materials with H2O2. Notably, powdered groceries, such as coffee, tea, grounded spices, and flour, are particularly interesting to pyrotechnics enthusiasts due to their easy production using accessible precursors, which do not attract the attention of security agencies. H2O2-based HMEs may become a dangerous component of improvised explosive devices for terrorists and ordinary offenders. For the four most powerful mixtures-HMEs based on coffee, tea, paprika, and turmeric-molecular markers useful for identification using the GC-MS technique have been proposed. Furthermore, the observed time-dependent changes in mixtures of H2O2 with these food products were studied and evaluated as a potential method for assessing the age of the evidence and reconstructing timelines of crimes. The paper also discusses the usefulness of FT-IR spectroscopy for identifying H2O2-based HMEs.

The importance of anchoring ligands of binuclear sensitizers on electron transfer processes and photovoltaic action in dye-sensitized solar cells.

The relatively low photon-to-current conversion efficiency of dye-sensitized solar cells is their major drawback limiting widespread application. Light harvesting, followed by a series of electron transfer processes, is the critical step in photocurrent generation. An in-depth understanding and fine optimization of those processes are crucial to enhance cell performance. In this work, we synthesize two new bi-ruthenium sensitizers with extended anchoring ligands to gain insight into underlying processes determining photovoltaic action mechanisms. The structure of the compounds has been confirmed, and their properties have been thoroughly examined by various techniques such as NMR, IR, elemental analysis UV-Vis, cyclic voltammetry, and electroabsorption. The experimental characterization has been supported and developed via extensive quantum-chemical calculations, giving a broad view of the presented molecules' properties. Finally, the DSSC devices have been assembled utilizing obtained dyes. The photovoltaic and EIS measurements, combined with performed calculations and fundamental dyes characterization, unraveled an intramolecular electron transfer as an initial step of the electron injection process at the dye/semiconductor interface. The overall photovoltaic action mechanism has been discussed. Our study demonstrates the significance of the anchoring group architecture in the molecular design of new sensitizers for DSSC applications.

Explosives removal and quantification using porous adsorbents based on poly(2-oxazoline)s with various degree of functionalization.

Polymeric porous adsorbents are reported for removal of explosives, namely picric acid, 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN) and their subsequent quantification using direct analysis with ambient plasma mass spectrometry. The adsorbents are obtained by functionalization of short-chain poly(2-oxazoline)s with methyl ester side chains using 4-(aminomethyl)pyridine with a degree of functionalization equal to 0, 5, 10, and 20%. The subsequent step consist of cross-linking using a high internal phase emulsion procedure by further side-chain amidation with diethylenetriamine as crosslinker. Picric acid, RDX, and PETN were chosen as the model compounds as they belong to three different groups of explosives, in particular nitroaromatics, nitroamines, and nitrate esters, respectively. The adsorption isotherms, kinetics, as well as the influence of pH and temperature on the adsorption process was investigated. The porous adsorbents showed the highest maximum adsorption capacity towards picric acid, reaching 334 mg g-1, while PETN (80 mg g-1) and RDX (17.4 mg g-1) were less efficiently adsorbed. Subsequent quantification of the adsorbed explosives is performed by a specially designed ambient mass spectrometry setup equipped with a thermal heater. The obtained limits of detection were found to be 20-times improved compared to direct analysis of analyte solutions. The effectiveness of the proposed analytical setup is confirmed by successful quantification of the explosives in river water samples. The research clearly shows that functional porous adsorbents coupled directly with ambient mass spectrometry can be used for rapid quantification of explosives, which can be, e.g., used for tracking illegal manufacturing sites of these compounds.

Blockade of persistent colored isomer formation in photochromic 3H-naphthopyrans by excited-state intramolecular proton transfer.

In photochemistry the excited-state intramolecular proton transfer process (ESIPT) is often observed as a highly efficient singlet excited state depletion pathway, which in the presence of a strong intramolecular hydrogen bond may proceed on a subpicosecond time scale. The present work describes the suppression of unwanted transoid-trans isomer formation in photochromic 3H-naphthopyran derivatives by the introduction of a 5-hydroxy substituent. According to time-resolved spectroscopy experiments and excited-state ab initio calculations, transoid-cis → transoid-trans photoisomerization is reduced by a competitive ESIPT channel in nonpolar solvent (cyclohexane). Upon specific solute-solvent interactions (methanol, acetonitrile) the intramolecular hydrogen bond in the transoid-cis form is perturbed, favoring the internal conversion S1 → S0 process as photostabilizing channel.

Mechanistic insights into photochromic 3H-naphthopyran showing strong photocoloration.

3,3-Diphenylbenzo[f]chromene (1) represents an important architectural platform for photochromic systems. Since the practical utility of such chromophores is largely dependent upon the kinetics of coloration and decoloration, elucidating the mechanistic details of these processes is of great value. Toward this end, we studied the photochromic reaction of (3-(2-methoxyphenyl)-3-phenyl-3H-benzo[f]chromene (2) by both time-resolved UV-vis and mid-IR spectroscopies. We found that irradiation of 2 at 365 nm generates long-lived colored transoid-cis isomers with lifetimes of 17.1 s and 17.5 min (at 21 °C) and even longer-lived transoid-trans isomers with a lifetime of 16 h. These experimental results were supplemented with ab initio ground-state and excited-state calculations, and the resulting theoretical interpretation may be useful for the design of new photochromic systems with optimized photofunctionality.

Electronic States of Tris(bipyridine) Ruthenium(II) Complexes in Neat Solid Films Investigated by Electroabsorption Spectroscopy.

We present the electric field-induced absorption (electroabsorption, EA) spectra of the solid neat films of tris(bipyridine) Ru(II) complexes, which were recently functionalized in our group as photosensitizers in dye-sensitized solar cells, and we compare them with the results obtained for an archetypal [Ru(bpy)3]2+ ion (RBY). We argue that it is difficult to establish a unique set of molecular parameter values by discrete parametrization of the EA spectra under the Liptay formalism for non-degenerate excited states. Therefore, the experimental EA spectra are compared with the spectra computed by the TDDFT (time-dependent density-functional theory) method, which for the first time explains the mechanism of electroabsorption in tris(bipyridine) Ru complexes without any additional assumptions about the spectral lineshape of the EA signal. We have shown that the main EA feature, in a form close to the absorption second derivative observed in the spectral range of the first MLCT (metal-to-ligand charge transfer) absorption band in Ru(bpy)3(PF6)2, can be attributed to a delocalized and orbitally degenerate excited state. This result may have key implications for the EA mechanism in RBY-based systems that exhibit similar EA spectra due to the robust nature of MLCT electronic states in such systems.

Specific Noncovalent Association of Truncated exo-Functionalized Triangular Homochiral Isotrianglimines through Head-to-Head, Tail-to-Tail, and Honeycomb Supramolecular Motifs.

Chiral isotrianglimines were synthesized by the [3 + 3] cyclocondensation of (R,R)-1,2-diaminocyclohexane with C5-substituted isophthalaldehyde derivatives. The substituent's steric and electronic demands and the guest molecules' nature have affected the conformation of individual macrocycles and their propensity to form supramolecular architectures. In the crystal, the formation of a honeycomb-like packing arrangement of the simplest isotrianglimine was promoted by the presence of toluene or para-xylene molecules. A less symmetrical solvent molecule might force this arrangement to change. Polar substituents present in the macrocycle skeleton have enforced the self-association of isotrianglimines in the form of tail-to-tail dimers. These dimers could be further arranged in higher-order structures of the head-to-head type, which were held together by the solvent molecules. Non-associating isotrianglimine formed a container that accommodated acetonitrile molecules in its cavity. The calculated dimerization energies have indicated a strong preference for the formation of tail-to-tail dimers over those of the capsule type.

Gas-phase generation of dinuclear Au(I)-Au(II) complexes by laser desorption ionization mass spectrometry.

Alkali metal chloroaurates(III) were analysed by laser desorption ionization mass spectrometry. Among a number of generated gas-phase ionic clusters, the unusual ions [MAu2Cl5]- (were M stands for Na, K, Rb, Cs) were detected. The spectra of metastable ions and quantum mechanics calculations show the presence of unprecedented Au(I)-Au(II) interactions in the clusters.

Effect of ß-Ketoiminato Ancillary Ligand Modification on Emissive Properties of New Iridium Complexes.

A series of new bis(benzo[h]quinolinato) Ir(III) complexes with modified ß-ketoiminato ancillary ligands were synthesized, and their electrochemical, photophysical properties were determined with the support of theoretical calculations. Moreover, all the synthesized heteroleptic Ir(III) complexes were examined as dopants of the host-guest type emissive layers in solution-processed phosphorescent organic light emitting diodes (PhOLEDs) of a simple structure. As expected on the basis of voltammetry measurements as well as DFT calculations, all the compounds appeared to be green emitters. Their examination showed that alteration of ß-ketoiminato ligand structure causes frontier orbitals' energy levels to be slightly changed, while significantly affecting photoluminescence and electroluminescence efficiencies of iridium phosphors containing these ligands. It was also found that modification of ancillary ligands might enhance charge trapping on the dopant, thus increasing its efficiency, especially in electroluminescence. From among the iridium complexes studied, the compound bearing 1-naphthyl group bonded to the nitrogen atom of the ancillary ligand proved to be the most efficient emitter. The PhOLED fabricated on the basis of this dopant has reached a luminance level of 16000 cd/m2, current efficiency close to 12 cd/A, and an external quantum efficiency around 3.2%.

Signals of diagnostic ions in the product ion spectra of [M - H]- ions of methoxylated flavonoids.

RATIONALE: The main feature of the fragmentation of [M - H]- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH3 ]-• product ion). Subsequent decomposition of [M - H - CH3 ]-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids. METHODS: Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument. RESULTS: A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking. CONCLUSIONS: The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH3 ]-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.

Identification of a biliverdin geometric isomer by means of HPLC/ESI-MS and NMR spectroscopy. Differentiation of the isomers by using fragmentation "in-source".

ABSTRACT: A commercially available biliverdin sample was analyzed by means of HPLC/ESI-MS and NMR spectroscopy. It was been found that beside the main IXα 5Z,10Z,15Z isomer, the sample contains also the geometric isomer IXα 5Z,10Z,15E. It was also found the isomers behave differentially upon "in-source" fragmentation in negative ion mode (in contrast to the their behavior upon "in-source" fragmentation in positive ion mode and to their behavior upon MS/MS fragmentation in both modes): the relative abundances of deprotonated molecules and fragment ions are significantly different for both isomers, which can be used as an analytical tool to differentiate between the isomers.

Methyl group transfer upon gas phase decomposition of protonated methyl benzoate and similar compounds.

Gas phase decompositions of protonated methyl benzoate and its conjugates have been studied by using electrospray ionization-collision induced dissociation-tandem mass spectrometry. Loss of CO2 molecule, thus transfer of methyl group, has been observed. In order to better understand this process, the theoretical calculations have been performed. For methyl benzoate conjugates, it has been found that position of substituent affects the loss of CO2 molecule, not the electron donor/withdrawing properties of the substituent. Therefore, electrospray ionization-mass spectrometry in positive ion mode may be useful for differentiation of isomers of methyl benzoate conjugates.

Scorpionate complexes of aza-18-crown-6 containing fluoronitrophenyl substituents as studied by electrospray ionization mass spectrometry.

RATIONALE: Coordination of a metal cation by a nitro group is rare and the interaction between them is usually weak. Examples of complexes in which such an interaction takes place are metal complexes of cyclams containing nitrophenyl or nitrobenzyl substituents. It seemed to be interesting to check if in the complexes of the respective crown ether conjugates the interaction can also take place. METHODS: We synthesized the respective conjugates of aza-18-crown-6, namely fluoro-substituted N-nitrophenylaza-18C6 conjugates. Their complexes with alkali and alkali earth metal cations were generated in the gas phase by electrospray ionization mass spectrometry (ESI-MS). Both collision-induced dissociation 'in-source' and collision-induced dissociation tandem mass spectrometry (ESI-CID-'in-source' and ESI-CID-MS/MS) were used to study the gas-phase stabilities of the generated complexes. RESULTS: The gas-phase decomposition of the studied complexes indicated that the complexes formed by the conjugates containing a nitro group at the ortho position are more stable than those formed by the conjugates with a nitro group at the para position. CONCLUSIONS: This indicates that a metal cation complexed by crown ether ring is additionally coordinated by a nitro group in the scorpionate mode. To the best of our knowledge, our finding provide the first example of a complex in which a metal cation complexed by a crown ether ring is additionally coordinated by a nitro group.

Factors Affecting the Performance of Champion Silyl-Anchor Carbazole Dye Revealed in the Femtosecond to Second Studies of Complete ADEKA-1 Sensitized Solar Cells.

Record laboratory efficiencies of dye-sensitized solar cells have been recently reported using an alkoxysilyl-anchor dye, ADEKA-1 (over 14 %). In this work we use time-resolved techniques to study the impact of key preparation factors (dye synthesis route, addition of co-adsorbent, use of cobalt-based electrolytes of different redox potential, creation of insulating Al2 O3 layers and molecule capping passivation of the electrode) on the partial charge separation efficiencies in ADEKA-1 solar cells. We have observed that unwanted fast recombination of electrons from titania to the dye, probably associated with the orientation of the dyes on the titania surface, plays a crucial role in the performance of the cells. This recombination, taking place on the sub-ns and ns time scales, is suppressed in the optimized dye synthesis methods and upon addition of the co-adsorbent. Capping treatment significantly reduces the charge recombination between titania and electrolyte, improving the electron lifetime from tens of ms to hundreds of ms, or even to single seconds. Similar increase in electron lifetime is observed for homogenous Al2 O3 over-layers on titania nanoparticles, however, in this case the total solar cells photocurrent is decreased due to smaller electron injection yield from the dye. Our studies should be important for a broader use of very promising silyl-anchor dyes and the further optimization and development of dye-sensitized solar cells.

FAPA mass spectrometry of designer drugs.

Application of a flowing atmospheric-pressure afterglow ion source for mass spectrometry (FAPA-MS) for the analysis of designer drugs is described. In this paper, we present application of FAPA MS for identification of exemplary psychotropic drugs: JWH-122, 4BMC, Pentedrone, 3,4-DNNC and ETH-CAT. We have utilized two approaches for introducing samples into the plasma stream; first in the form of a methanolic aerosol from the nebulizer, and the second based on a release of vapors from the electrically heated crucible by thermal desorption. The analytes were ionized by FAPA and identified in the mass analyzer. The order of release of the compounds depends on their volatility. These methods offer fast and reliable structural information, without pre-separation, and can be an alternative to the Electron Impact, GC/MS, and ESI for fast analysis of designer-, and other psychoactive drugs.

Complexation of phosphates by 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane.

RATIONALE: Compounds containing a urea or thiourea moiety form complexes with anions thanks to the ability to form quite strong hydrogen bonds. We have synthesized 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane (1). Compound 1 contains two urea moieties connected by a long flexible linker; thus, it should be able to adopt a structure suitable for formation of quite stable complexes with anions. METHODS: The ability to form complexes of compound 1 with phosphates was tested by electrospray ionization mass spectrometry (ESI-MS). Full scan ESI mass spectra and collision-induced dissociation tandem mass (CID-MS/MS) spectra of the ions of interest were obtained on a quadrupole time-of-flight (QTOF) mass spectrometer. RESULTS: It has been found that compound 1 is not only much more prone to form complexes with the phosphate anion than with other inorganic anions, but it is also able to form complexes with organic phosphates, namely nucleotides and phospholipids. However, compound 1 is not able to form complexes with organic compounds not containing a phosphate group (e.g. nucleosides, sugars, glycerolipids). CONCLUSIONS: Compound 1 can be regarded as selective towards phosphate-containing organic compounds. Formation of such complexes may have some interesting applications for identification of organic phosphates in crude extracts from biological materials.