A redox active rod coordination polymer from tetrakis(4-carboxylic acid biphenyl)tetrathiafulvalene.

An enlarged version of the ubiquitous tetrathiafulvalene-tetrabenzoic acid is described, with 4,4'-biphenyl moieties as spacers between the coordination moieties and the electroactive core. The obtained rectangular ligand has a 14 × 22 Å2 size and is combined with Zn(II) under solvothermal conditions to yield a coordination polymer endowed with large cavities of ca. 15 × 11 Å2/10 × 10 Å2. The topology of the material is discussed in detail using the Points of Extension and Metals (PE&M) or the Straight-rod (STR) representation, and the sqc1121 or tfo topological type of the structure is observed, respectively. Its stability towards solvent removal and electrical properties are discussed. The material does not present any permanent porosity upon desolvation according to nitrogen sorption measurements at 77 K. Nevertheless, a significant increase in conductivity is observed on compressed pellets of the material upon post-synthetic oxidation with iodine. Raman spectroscopy combined with density functional theory (DFT) calculations has been used to characterize the oxidation state of tetrakis(4-carboxylic acid biphenyl)tetrathiafulvalene for coordination polymers.

Single-Wall Carbon Nanohorn Langmuir-Schaefer Films.

A suspension of single-walled carbon nanohorn (SWCNH) aggregates with a size of approx. 50 nm was used to create a floating film at the water-air interface. The film was then transferred onto large-area quartz substrates using the Langmuir-Schaefer technique at varied surface pressures. The packaging and arrangement of SWCNHs in the film can be controlled during the process. The resulting films' optical and electrical properties were investigated, and the highest electrical conductivity and figure of merit parameter values were observed for the film transferred at surface pressure near the collapse point. These films had a surface density of less than 5 µg cm-2, making them ideal for use in ultra-light sensors, supercapacitors, and photovoltaic cell electrodes. The preparation and properties of the Langmuir-Schaefer films of carbon nanohorns are reported for the first time.

Bis(Vinylenedithio)-Tetrathiafulvalene-Based Coordination Networks.

Novel coordination polymers embedding electroactive moieties present a high interest in the development of porous conducting materials. While tetrathiafulvalene (TTF) based metal-organic frameworks were reported to yield through-space conducting frameworks, the use of S-enriched scaffolds remains elusive in this field. Herein is reported the employment of bis(vinylenedithio)-tetrathiafulvalene (BVDT-TTF) functionalized with pyridine coordinating moieties in coordination polymers. Its combination with various transition metals yielded four isostructural networks, whose conductivity increased upon chemical oxidation with iodine. The oxidation was confirmed in a single-crystal to single-crystal X-ray diffraction experiment for the Cd(II) coordination polymer. Raman spectroscopy measurements and DFT calculations confirmed the oxidation state of the bulk materials, and band structure calculations assessed the ground state as an electronically localized antiferromagnetic state, while the conduction occurs in a 2D manner. These results are shedding light to comprehend how to improve through-space conductivity thanks to sulfur enriched ligands.

Charge-Ordering and Structural Transition in the New Organic Conductor δ'-(BEDT-TTF)2CF3CF2SO3.

We report structural, transport, and optical properties and electronic structure calculations of the δ'-(BEDT-TTF)2CF3CF2SO3 (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) organic conductor that has been synthesized by electrocrystallization. Electronic structure calculations demonstrate the quasi-one-dimensional Fermi surfaces of the compound, while the optical spectra are characteristic for a dimer-Mott insulator. The single-crystal X-ray diffraction measurements reveal the structural phase transition at 200 K from the ambient-temperature monoclinic P21/m phase to the low-temperature orthorhombic Pca21 phase, while the resistivity measurements clearly show the first order semiconductor-semiconductor transition at the same temperature. This transition is accompanied by charge-ordering as it is confirmed by splitting of charge-sensitive vibrational modes observed in the Raman and infrared spectra. The horizontal stripe charge-order pattern is suggested based on the crystal structure, band structure calculations, and optical spectra.

Structure, optical and electro-physical properties of tetramerized anion-radical salt (N-Xy-Qn)(TCNQ)2.

The (N-Xy-Qn)(TCNQ)2 anion-radical salt characterized by tetramerized stacks of the TCNQ acceptor molecules has been synthesized and characterized using vibrational spectroscopy and electrical resistivity measurements. The bond lengths analysis based on the crystal structure data, indicates that the TCNQ molecules are non-uniformly charged with -0.83 e localized on the inner B molecules and -0.33 e on the outer A molecules within ABBA tetramers. Both infrared and Raman spectra of (N-Xy-Qn)(TCNQ)2 are dominated by vibrational modes of TCNQ and display splitting related to the tetramerized structure. Many of these features are affected by the strong electron-molecular vibration (EMV) coupling. Other charge-sensitive modes allowed estimation of charge localized on TCNQ, with the results that confirm the charges estimated on basis of the crystal data. Electrical measurements revealed the low-conducting behavior with room temperature conductivity value of 2.6 mS cm-1 and temperature dependence of resistivity that can be explained within the band conduction model. The calculated activation energies range from 0.169 eV to 0.187 eV, depending on the crystallographic direction and thermal history of the sample.

Correction: The influence of diameter of multiwalled carbon nanotubes on mechanical, optical and electrical properties of Langmuir-Schaefer films.

Correction for 'The influence of diameter of multiwalled carbon nanotubes on mechanical, optical and electrical properties of Langmuir-Schaefer films' by Karol Rytel et al., Phys. Chem. Chem. Phys., 2020, DOI: .

The influence of diameter of multiwalled carbon nanotubes on mechanical, optical and electrical properties of Langmuir-Schaefer films.

In this paper results of a study of mechanical, optical and electrical properties of thin films made of multiwall carbon nanotubes (MWCNT) of various types were reported. The MWCNT films were obtained on quartz substrates using the Langmuir-Schaefer (LS) method. A gradual increase in transmittance was recorded with decreasing diameters of MWCNT used. Moreover, a blue shift of the π-plasmon band position was observed with increasing MWCNT diameter. In all tested films, anisotropy of electrical surface resistivity was revealed, which was more pronounced for MWCNT of low diameters, except for the MWCNT sample of the smallest diameters. Results of oscillatory barrier measurements of various MWCNT films at the air water interface were used to calculate the complex compression and shear moduli. It is worth emphasizing that the values of these moduli were obtained for the first time for carbon nanotubes films. Moreover, the obtained results allowed identification of the main factor blocking the alignment process, which turned out to be the shear loss tangent.

Lifetime nanomanometry - high-pressure luminescence of up-converting lanthanide nanocrystals - SrF2:Yb3+,Er3.

Anti-Stokes luminescence of up-converting nanocrystals SrF2:Yb3+,Er3+ can be used as a high pressure optical sensor alternative to the ruby fluorescence-scale. In nanocrystalline SrF2:Yb3+,Er3+, high pressure reversibly shortens the emission lifetimes nearly linearly up to 5.29 GPa at least. Its advantage is the use of NIR (≈980 nm) radiation, highly penetrable for many materials. The shortening of up-conversion lifetimes has been attributed mainly to the changes in energy transfer rates, caused by decreased interatomic distances and increased overlap integrals between 4f electrons and the valence shells of ligand ions. The origin of high-pressure effects on the luminescence intensity, band ratio and their spectral position has been explained by the increased interactions and distortions of the crystal-field symmetry around the emitting ions in the compressed structure.

Crystal structure of bis-(ethyl-enedi-thio)-tetra-thia-fulvalenium µ2-acetato-bis-[tri-bromido-rhenate(III)] 1,1,2-tri-chloro-ethane hemisolvate.

The asymmetric unit of the title salt, (C10H8S8)[Re2Br6(CH3COO)]·0.5C2H3Cl3, contains one bis-(ethyl-enedi-thio)-tetra-thia-fulvalene (ET) radical cation, one µ2-acetato-bis-[tri-bromido-rhenate(III)] anion and a 1,1,2-tri-chloro-ethane mol-ecule with half-occupancy disordered about a twofold rotation axis. The tetra-thia-fulvalene fragment adopts an almost planar configuration typical of the ET radical cation. The C atoms of both ethyl-enedi-thio fragments in the cation are disordered over two orientations with occupancy factors 0.65:0.35 and 0.77:0.23. In the anion, six Br atoms and a µ2-acetate ligand form a strongly distorted cubic O2Br6 coordination polyhedron around the Re2 dinuclear centre. In the crystal, centrosymmetrically related ET cations and Re2O2Br6 anions are linked into dimers by π-π stacking inter-actions [centroid-to-centroid distance = 3.826 (8) Å] and by pairs of additional Re⋯Br contacts [3.131 (3) Å], respectively. The dimers are further packed into a three-dimensional network by non-directional inter-ionic electrostatic forces and by C-H⋯Br and C-H⋯S hydrogen bonds. The disordered 1,1,2-tri-chloro-ethane mol-ecules occupy solvent-accessible channels along the b axis.

Morphology and molecular arrangement of perylene-3,4,9,10-(n-pentylester) in thin layers obtained by zone-casting.

Liquid-crystalline perylene-3,4,9,10-tetra-(n-pentylester) zone-casted on hydrophilic glass substrates forms characteristic belt-like structures which are observed under optical microscope and atomic force microscope. Polarised Raman scattering spectra reveal the presence of anisotropic alignment of the molecules inside the obtained structures. Moreover, the absorption and fluorescence spectra confirm molecular aggregation in the belt-like structures. The research shows, that the belt-like structures are created by columns of molecules with the edge-on alignment on the glass substrate. Such organisation of the molecules is confirmed by spectroscopic methods. These structures can be interesting from the point of view of organic electronics.

The impact of solvents on the singlet and triplet states of selected fluorine corroles - absorption, fluorescence, and optoacoustic studies.

This paper examines the influence of aprotic solvents on the spectroscopic properties as well as the energy deactivation of two free-base corrole dyes substituted with C6F5 and/or 4-NO2C6H4 groups. Absorption, fluorescence and laser-induced optoacoustic spectroscopy have been used to follow the singlet and triplet states of fluorine corroles belonging to the A2B and A3 type in toluene (TL), chloroform (CL), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and also in solvent mixtures. Changes in the absorption and fluorescence spectra are influenced by the type of solvent mixture. The fluorescence behaviors of the two investigated corroles were extremely different - fluorescence of the nitro-corrole in TL is dramatically quenched in the presence of DMF. In contrast, fluorescence quenching of fluorine corroles in DMF-TL mixtures is substantially weakened. Absorption, fluorescence, triplet population as well as singlet oxygen generation parameters are evaluated. The spectral experimental data are supported by quantum chemical calculations - time-dependent density functional theory (TD-DFT) and cyclic voltammetry experiments. The presented results are discussed from a viewpoint of aggregation, tautomerization, and deprotonation effects occurring in the corroles.

New meso-substituted corroles possessing pentafluorophenyl groups--synthesis and spectroscopic characterization.

The investigation presented in this paper deals with new free-base corroles substituted with different peripheral groups. These aromatic macrocycles were efficiently synthesized by a [2+1] approach from dipyrromethanes. Moreover, the basic spectroscopic studies of the dyes in chloroform were conducted, and the UV-Vis absorption, fluorescence and ESR parameters were estimated. The experimental data were supported by quantum chemical calculations. The presence of monomeric dye structures is concentration independent (10(-6)-10(-4) M), as expected for dyes in a solvent of low polarity, and rules out aggregate formation of corroles dissolved in chloroform. The excitation emission and fluorescence life-time values confirm the monomeric structure of the corroles. The spectra were compared with the time-dependent density functional theory (TD-DFT) results for the HOMO-LUMO states. The ESR examinations strongly show that for any type of studied fluorine corrole an unpaired electron is localized on the corrole macroring but not on the substituents both before and after light illumination. Laser illumination creates additional radicals, however with different effectiveness depending on the sample.

Solid-state stability and compatibility studies of clavulanate potassium.

The kinetic and thermodynamic parameters of degradation of clavulanate potassium in the solid state were studied by using a reversed phase high performance liquid chromatography (RP-HPLC) method. The degradation of clavulanate potassium was a first-order reaction depending on the substrate concentration at an increased relative air humidity (RH) and in dry air. The dependence ln k = f(1/T) became the ln k = (0.026 ± 166.35)-(2702.82 ± 1779.43)(1/T) in dry air and ln k = (1.65 ± 100.40) × 10(3)-(5748.81 ± 3659.67)(1/T) at 76.4% RH. The thermodynamic parameters Ea, ΔH(≠a), ΔS(≠a) of the degradation of clavulanate potassium in the solid state were calculated. The dependence ln k = f (RH%) assumed the form ln k = (8.78 ± 5.75) 10 (-2) (RH%) + (2.64 × 10(-8 )± 40.41). The compatibility of clavulanate potassium with commonly used excipients was studied at an increased temperature and in dry air. The geometric structure of molecule, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbitals were also determined in order to predict the structural changes and reactive sites in clavulanate potassium during degradation and compatibility studies in the solid state. The ultraviolet (UV), Fourier transform infrared spectroscopy (FT-IR) and Raman spectra of degraded samples of the compound were analyzed.

Solid-state stability studies of faropenem based on chromatography, spectroscopy and theoretical analysis.

AIM: The purpose of this study was to investigate the stability of faropenem in solid state. RESULTS: The kinetic and thermodynamic parameters of degradation of faropenem were studied using an RP-HPLC method while the changes of spectral properties were investigated using derivative UV and FT-IR. Quantum-chemical calculations, based on the density functional theory, were carried out to support the estimation of the intra-ring stresses of faropenem and for theoretical interpretation of the spectra. The degradation of faropenem was a first-order reaction depending on the substrate concentration at an increased relative humidity and in dry air. The dependence ln k = f(1/T) became the ln k = (2.03 ± 3.22) × 10(4)-(9761 ± 3052)(1/T) in dry air and ln k = (1.25 ± 0.22) × 10(5)-(9004 ± 3479)(1/T ) at 90.0% RH. The thermodynamic parameters Ea, ΔH(≠a), and ΔS(≠a) of the degradation of faropenem were calculated. The dependence ln k = f(RH%) assumed the form ln k = (7.58 ± 1.88) × 10(-2) (RH%) - (5.90 ± 3.90) × 10(-8). CONCLUSIONS: Stability studies of faropenem showed that the fusion of ß-lactam and thiazolidine rings reduces the intra-ring stress, leading to a lower susceptibility to degradation in dry air and at increased RH.

Spectroscopic properties and orientation of molecules in Langmuir-Blodgett layers of selected functionalized fullerenes.

Vibrational properties of two fullerene derivatives: C60TZ-OT-5 (1) and C60TH-3HX (2) have been studied using infrared absorption and Raman scattering spectroscopies. Additionally, quantum chemical calculations of the equilibrium geometry and normal mode vibrations of these functionalized fullerenes were performed. It was stated that despite of distinct structural differences between the investigated molecules, their experimental spectra are quite similar and correspond well with the calculated ones. The orientation of the molecules in the Langmuir-Blodgett films was evaluated.

Solid-state stability study of meropenem - solutions based on spectrophotometric analysis.

BACKGROUND: B-Lactam antibiotics are still the most common group of chemotherapeutic drugs that are used in the treatment of bacterial infections. However, due to their chemical instability the potential to apply them as oral pharmacotherapeutics is often limited and so it is vital to employ suitable non-destructive analytical methods. Hence, in order to analyze such labile drugs as ß-lactam analogs, the application of rapid and reliable analytical techniques which do not require transferring to solutions or using organic solvents, following the current green approach to pharmaceutical analysis, is necessary. The main objective of the present research was to develop analytical methods for the evaluation of changes in meropenem in the solid state during a stability study. RESULTS: The UV, FT-IR and Raman spectra of meropenem were recorded during a solid-state stability study. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated according to the density-functional theory (DFT/B3LYP method) with a 6-31G(d,p) basis set. As the differences between the observed and scaled wavenumber values were small, a detailed interpretation of the FT-IR and Raman spectra was possible for non-degraded and degraded samples of meropenem. The problem of the overlapping spectra of meropenem and ring-containing degradation products was solved by measuring changes in the values of the first-derivative amplitudes of the zero-order spectra of aqueous solutions of meropenem. Also, molecular electrostatic potential (MEP), front molecular orbitals (FMOs) and the gap potential between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were determined. CONCLUSIONS: Based on the findings of this work, it appears possible to use time-saving and reliable spectrophotometric analytical methods, supported by quantum-chemical calculations, for solid-state stability investigations of meropenem. The methods developed for this study may be considered a novel, green solution to pharmaceutical analysis of labile drugs - an alternative for the recommended chromatographic procedures.

Hydrothermal synthesis and structural and spectroscopic properties of the new triclinic form of GdBO3:Eu3+ nanocrystals.

Triclinic Gd1-xEuxBO3 nanophosphors have been prepared by a hydrothermal method without using additional coreagents and prior precipitation of precursor (in situ). The formation of the borate nanorods and their crystal structure was refined on the basis of X-ray diffraction patterns (XRD) and well confirmed using various techniques such as infrared spectroscopy (IR), Raman spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The new triclinic crystal structure (space group P1) for the GdBO3 nanocrystals and detailed structure parameters were determined with the help of the Rietveld analysis. The spectroscopic characteristics of the synthesized nanomaterials with different concentrations of Eu(3+) ions were defined with the use of luminescence excitation spectra as well as emission spectra and decay kinetics. The Judd-Ofelt parameters (Ω2, Ω4) and quantum efficiency, η, were also calculated for the more detailed analysis of Eu(3+) spectra in the GdBO3 host.

Stress Degradation Studies of Tebipenem and a Validated Stability-Indicating LC Method.

A inexpensive and rapid isocratic LC method has been developed for the quantitative determination of tebipenem-a new ß-lactam antibiotic. Stress degradation studies were performed on tebipenem in acidic (0.2 N hydrochloric acid) and basic (0.02 N sodium hydroxide) solutions, in a solution with oxidizing agent (3 % hydrogen peroxide), and in the solid state, during thermolysis and photolysis. For a chromatographic separation of tebipenem and its degradation products, a C-18 stationary phase and 12 mM ammonium acetate-acetonitrile (96:4 v/v) were used. A quantitative determination of tebipenem was carried out by using a PDA detector at 298 nm, with a flow rate of 1.2 mL min-1. The linear regression analysis for the calibration plots showed a good linear relationship (r = 0.999) in the concentration range 0.041-0.240 mg mL-1. The method demonstrated good precision (1.14-1.96 % RSD) and recovery (99.60-101.90 %). The limits of detection and quantitation were 9.69 and 29.36 µg mL-1, respectively. The analysis of tebipenem reactivity was supported by quantum chemical calculations based on the density functional theory (DFT). The analysis of the electron density of the HOMO and LUMO of tebipenem suggested the possibility of electron transport in the molecule during the degradation of bi-cyclic 4:5 fused penem rings.

IR and Raman spectra of beta''-(BEDT-TTF)(2)RCH(2)SO(3) (R = SF(5), CF(3)): dimerization related to hydrogen bonding.

The beta''-(BEDT-TTF)(2)CF(3)CH(2)SO(3) organic conductor has been synthesized by electrocrystallization. The crystal structure was determined by single-crystal X-ray diffraction and electronic properties examined. The polarized IR reflectance of beta''-(BEDT-TTF)(2)SF(5)CH(2)SO(3) and beta''-(BEDT-TTF)(2)CF(3)CH(2)SO(3), as well as Raman spectra of beta''-(BEDT-TTF)(2)CF(3)CH(2)SO(3) have been measured as a function of temperature. Both materials display charge-nonequivalence within the whole temperature range and unusual activation of vibronic modes with lowering the temperature. In particular, electron-molecular vibration coupling is involved in the activation of the nu(27) mode. The effect is discussed in terms of lattice dimerization involving hydrogen bonding between the anion layer and the conducting BEDT-TTF layer.