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2,6-Diformylphenylboronic acid has been synthesized and characterized both in the solid state as well as in solution. In crystal, an unusual structural pattern has been found with the formation of intermolecular hydrogen bonds by B(OH) 2 and CHO groups as well as water molecules. In solution tautomeric equilibrium with the formation of oxaborole ring by one of the formyl groups was proved on the basis of multinuclear NMR spectroscopy. The title compound reacts with secondary mono- and diamines to form various types of substituted benzoxaboroles, which have been characterized by XRD and spectroscopic methods. [ABSTRACT FROM AUTHOR]

ESI-CID-MS/MS spectra of [Mn+(NO3-)n+1]- anions (M stands for a transition metal, for a metal from group 2 or 13 of the periodic table), thus composed only of a metal and nitrate groups, are discussed in details. Decomposition of [Mn+(NO3-)n+1]- ions consists in (i) formation of fragment ion NO3-, (ii) loss of NO3· radical, (iii) loss of NO2, sometimes also NO, molecule(s). Process (iii) is the most interesting, as for example it may lead to the formation of fragment ions containing metal at the highest, possible oxidation state (e.g. [Mn(NO3)3]- → MnO4- + 2NO2 + NO, anion MnO4- contains MnVII) or to the formation of oxygen molecule (e.g. [Ni(NO3)3]- → [NiNO3]- + 2NO2 + O2). Process (i) is trivial and it is the dominant, sometimes the only, decomposition pathway of anions [Mn+(NO3-)n+1]- which contain metal of low charge density. Process (ii) is the decomposition pathway characteristic of anions [Mn+(NO3-)n+1]- which contain metal prone to be reduced (e.g. [Tl(NO3)4]- → [Tl(NO3)2]- + 2NO3-). [ABSTRACT FROM AUTHOR]

Abstract: Novel ionic liquids with iodide anions and functionalized with silicon tripodand centers have been synthesized and tested as iodide sources for dye sensitized solar cells, 1-methyl-3-(3-(trimethoxysilyl)propyl)imidazolium iodide 3a, 1-methyl-3-(3-(tris(2-methoxyethoxy)silyl)propyl)imidazolium iodide 3b, and 1-methyl-3-(3-(tris(2-(2-methoxyethoxy)ethoxy)silyl)propyl)imidazolium iodide 3c. The compounds have been proved to be thermally and electrochemically stable, as evidenced by thermogravimetry and linear sweep voltammetry on platinum. Specific conductivities at 25°C of pure ionic liquids are of the order of 10−4 Scm−1 and show little dependence on the length of oxaethylene chains. Conductivities rise to nearly 10−2 Scm−1 for the electrolytes prepared on their bases as a result of viscosity decrease. Model dye-sensitized solar cells show appreciable conversion efficiencies, reaching a maximum value of 5.08% for the electrolyte with 3b as iodide source. Electrochemical impedance spectroscopy measurements revealed high resistance associated with electron recombination on the interface of TiO2/dye/electrolyte and important contribution of electrolyte diffusion. [Copyright &y& Elsevier]

By the self-assembly monolayer (SAM) organization, three new podands belonging to silylpropanethiols have been tested as to their ability to form nanolayers protecting the noble metal surface (gold or silver) and to form complexes with monovalent metal cations on the metal surfaces. The stable self-assembled chemisorbed layers, providing protection to metal surface against electrooxidation and capable of blocking propylene carbonate (PC) electroreduction and Li electrodeposition were produced. Reflection-absorption infrared spectroscopy (RAIRS) indicated cleavage of the S–H bond upon adsorption of species 1–3 with the formation of S–Ag bonds on the metal surface. By cyclic voltammetry, it was found that the primary adsorbate formed on a Au electrode at E ad (between −0.2 and −1.2 V vs. SCE) underwent reductive desorption at E < −1.3 V vs. SCE. The structures of 1–3 and their complexes with Na+ cations on the Ag surfaces were calculated and visualized by the AM1d semi-empirical method. [ABSTRACT FROM AUTHOR]

Abstract: Triton X surfactants are used in numerous commercial and industrial products. Large amounts of such surfactants and their various residual biodegradation by-products are ultimately released into the environment. The first synthesis of the group of Tr-polypodands (Triton polypodands), with different central atoms, such as Si, B or P, is reported. Results of this study demonstrate the potential of these compounds in some organic reactions in phase-transfer catalysis (PTC) conditions. The catalytic activity of Triton X (1) and Tr-podands (2–8) has been evaluated in an ion promoted reaction under solid–liquid phase-transfer catalysis conditions and compared with that of the earlier studied Si-podands (9–11), used as PTC agents. [Copyright &y& Elsevier]

Abstract: The electron ionization (EI) induced mass spectrometric fragmentation pathways of the titled compounds were studied by electron ionization mass spectrometry. It was found that in the case two isomers are formed in one reaction, the substantially different fragmentation patterns enable to discriminate between them. All of the compounds studied have shown simple bond ruptures in the alkyl chain, some of them were accompanied by H-shift. Moreover, complex rearrangements, depending on compound structure, were also observed. In order to better understand the latter processes, mass spectra of isotope-labeled compounds, B/E mass spectra of metastable ions and high resolution mass spectra were recorded. [Copyright &y& Elsevier]

For thousands years Ephedrae herba has been used in traditional Chinese herbal medicine. Its main bioactive constituents are ephedrine and pseudoephedrine. Nowadays, these alkaloids have found application in various clinical treatments, as sports-enhancing drugs and for the illicit production of amphetamine-like drugs. Ephedrine and pseudoephedrine are diastereomers, and because of their high polarity and similar pK a values, their chromatographic separation may be a challenge. In this study a possible application of direct infusion mass spectrometry and direct infusion tandem mass spectrometry has been proposed for differentiation of ephedrine and pseudoephedrine as well as the relative determination of the contents of these compounds in a mixture. At low collision energy condition, the ratio of relative abundances of ions [M+H–H 2 O]+ and [M+H]+ permit distinction of the analyzed diastereomers, and enable evaluation of their relative content in a mixture with no need of chromatographic separation. The performed quantum chemical calculation have shown that protonated pseudoephedrine contains stronger hydrogen bond than protonated ephedrine, which can justify the observed higher relative abundance of ion [M+H–H 2 O]+ in the mass spectrum of pseudoephedrine, in comparison to that of ephedrine. [Display omitted] • MS methods has been proposed for differentiation of ephedrine and pseudoephedrine. • Abundances of ions [M+H–H 2 O]+ and [M+H]+ permit distinction of the compounds. • Evaluation of their relative content in a mixture is possible. • There is no need of chromatographic separation. • Formation of ions [M+H–H 2 O]+ has been studied by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Abstract Three isomers of trifluoromethylphenylboronic acids were synthesized and characterized by 1H, 13C, 11B and 19F NMR. The investigated compounds exhibit high resistance to protodeboronation reaction. Molecular and crystal structure of these compounds was determined by single crystal XRD method. The compounds form typical hydrogen-bonded dimers with the syn - anti conformation. CF 3 substituent does not interact with boronic moiety neither as hydrogen bond acceptor nor a lone-electron pair donor. p K a values of the isomers have been determined by spectrophotometric and potentiometric method. Introduction of the CF 3 group increases the acidity for meta and para isomers in comparison to the phenylboronic acid, while for the ortho isomer the acidity is reduced due to the steric hindrance. Graphical abstract Image 1 Highlights • Synthesis of isomeric trifluoromethylphenylboronic acids. • Multinuclear NMR characterization in solution. • Single crystal XRD measurements. • p K a determination. • Hydrolytic stability. [ABSTRACT FROM AUTHOR]

Four isomeric fluoro-2-formylphenylboronic acids were synthesized and characterized by 1 H, 13 C, 19 F and 17 O NMR. Molecular and crystal structure of two compounds was determined by single crystal XRD method. p K a values of all the isomers have been determined by spectrophotometric method and compared with the results for the corresponding benzoxaboroles as well as fluoro- and formylphenylboronic acids. Tautomeric equilibrium with cyclic benzoxaborole form was investigated. The influence of position of fluorine substituents on the properties of investigated compounds is discussed. [ABSTRACT FROM AUTHOR]

5-Fluoro-2,1-benzoxaborol-1(3H)-ol, a potent antifungal drug also known as Tavaborole or AN2690, has been compared with its three isomers in terms of its activity against several fungi as well as p K a and multinuclear NMR characterization. The molecular and crystal structure of 6-fluoro-2,1-benzoxaborol-1(3H)-ol was determined and compared with that of AN2690. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of ortho-methoxyalkylphenylboronic acids catechol esters. [•] 17O NMR characterization of the esters and parent acids. [•] Influence of hydrogen bond on the properties of the acids. [•] No O→B interactions in the investigated compounds. [•] Diminished acidity compared with the unsubstituted phenylboronic acid. [ABSTRACT FROM AUTHOR]

This article reports the synthesis details and film-forming properties of 1,1,3,3-tetramethyl-1,3-bis(3-(ω-hexadecyloxy-deca(ethylenoxy)propyl)disiloxane, a new potential electrolyte additive/functional co-solvent for propylene carbonate (PC)-based Li-ion cells with graphitic anodes. Galvanostatic charge/discharge characteristics and scanning electron microscopy images provide direct evidence for the suppression of solvent intercalation and graphite exfoliation in the presence of the additive. In terms of irreversible capacity, the additive's efficiency is the highest for 15% weight ratio in the solvent mixture. Potentiodynamic measurements have revealed that disiloxane component undergoes irreversible reduction at potential significantly higher then PC decomposition. Energy dispersive spectroscopy analysis of graphite flake surfaces confirm that silicon species from the disiloxane decomposition are built in the passive layer. The reported compound may be considered as a basis for alternative cost-effective electrolyte compositions for low-temperature applications. [ABSTRACT FROM AUTHOR]

The following ions [UO2(NO3)3]−, [UO2(ClO4)3]−, [UO2(CH3COO)3]− were generated from respective salts (UO2(NO3)2, UO2(ClO4)3, UO2(CH3COO)2) by laser desorption/ionization (LDI). Collision induced dissociation of the ions has led, among others, to the formation of UO4 − ion (m/z 302). The undertaken quantum mechanical calculations showed this ion is most likely to possess square planar geometry as suggested by MP2 results or strongly deformed geometry in between tetrahedral and square planar as indicated by DFT results. Interestingly, geometrical parameters and analysis of electron density suggest it is an UVI compound, in which oxygen atoms bear unpaired electron and negative charge. [Copyright &y& Elsevier]

Abstract: Phenylboronic acids with polyoxaalkyl substituents at ortho position were synthesized from the corresponding bromides. Structures in solid state, determined by single crystal X-ray diffraction, reveal the presence of inter- and intramolecular hydrogen bonds. Presence of several oxygen atoms in oxaalkyl chains enables the formation of intramolecular hydrogen bonds by B(OH)2 group with different oxygen centers which lead to the formation of bifurcated hydrogen bonds. Investigated compounds were characterized by 1H, 13C, 11B and 17O NMR spectroscopy in solution. Assignment of 1H and 13C signals was made on the basis of HSQC and HMBC spectra. 17O NMR spectra show that in acetonitrile solution hydrogen bonds with solvent molecules are predominant. [Copyright &y& Elsevier]

Metal-containing compounds form a large and rapidly expanding group of high-energy materials. Many compounds in this class attract the attention of non-professionals, who may attempt the illegal production of explosives. Several of these substances have been commercially available and pose significant danger if used by terrorists or for criminal purposes. Others are experimental compounds, kinds of curiosities, often created by pyrotechnics enthusiasts, which can present serious risks to both the creators and their immediate surroundings. The internet hosts a vast amount of information, including recipes and discussions on forums, private websites, social media, and more. This paper aims to review the variety of metal-containing explosives and discuss their appeal and potential accessibility to unauthorized individuals.

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 H 2 O 2 . 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. H 2 O 2 -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 H 2 O 2 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 H 2 O 2 -based HMEs., (© 2024. The Author(s).)

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., (© 2023. Springer Nature Limited.)

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 S 1  → S 0 process as photostabilizing channel., (© 2022. The Author(s).)

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., (© 2022. The Author(s).)

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 (PF 6 ) 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.

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.

Alkali metal chloroaurates(III) were analysed by laser desorption ionization mass spectrometry. Among a number of generated gas-phase ionic clusters, the unusual ions [MAu 2 Cl 5 ] - (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.

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 5 Z ,10 Z ,15 Z isomer, the sample contains also the geometric isomer IXα 5 Z ,10 Z ,15 E. 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.

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 Al 2 O 3 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 Al 2 O 3 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., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three series of substituted 1,3,4-oxadiazoles were studied by (17)O NMR spectroscopy. Chemical shifts values were correlated with empirical Hammett parameters as well as calculated bond lengths and chemical shielding values., (Copyright © 2011 John Wiley & Sons, Ltd.)

Protonated organic ligands containing pyridine moieties form complexes with undissociated salt molecules present in solution, especially with ZnCl(2), as proved by electrospray ionization mass spectrometry. In the gas phase, the ions observed, for example [L1H + ZnCl(2)](+), lose an HCl molecule producing ions [L1 + ZnCl](+) (L1 = 1,1,3,3-Tetramethyl-1,3-bis(3-(3-(2-pyridyl)propoxy)propyl)disiloxane). The use of other zinc salts (for example ZnI(2)), also yielded the complexes of between protonated ligands and neutral salt molecules (for example, [L1H + ZnI(2)](+)), but losses of respective acid molecules (for example, HI), proceeded with higher efficiencies than the loss of HCl molecule. An increase in solvent polarity, namely the use of water instead of methanol, led to the substantial lowering of [L1H + ZnCl(2)](+) ion abundances, since fewer undissociated species (for example, ZnCl(2)) were present in the solution. Ligand L2 (1,3,5,7-tetramethyl-1,3,5,7-tetrakis(3-(3-(2- pyridyl)propoxy)propyl)cyclotetrasiloxane, larger than L1), forms doubly charged ions containing one and two ZnCl(2) molecules, for example [L1H(2) + ZnCl(2)](+2).