Chloroform Solution Research Articles

Synthesis and Thermal Analysis of Non-Covalent PS-b-SC-b-P2VP Triblock Terpolymers via Polylactide Stereocomplexation.

Polylactides (PLAs) are thermoplastic materials known for their wide range of applications. Moreover, the equimolar mixtures of poly(L-Lactide) (PLLA) and poly(D-Lactide) (PDLA) can form stereocomplexes (SCs), which leads to the formation of new non-covalent complex macromolecular architectures. In this work, we report the synthesis and characterization of non-covalent triblock terpolymers of polystyrene-b-stereocomplex PLA-b-poly(2-vinylpyridine) (PS-b-SC-b-P2VP). Well-defined ω-hydroxy-PS and P2VP were synthesized by “living” anionic polymerization high-vacuum techniques with sec-BuLi as initiator, followed by termination with ethylene oxide. The resulting PS-OH and P2VP-OH were used as macroinitiators for the ring-opening polymerization (ROP) of DLA and LLA with Sn(Oct)2 as a catalyst to afford PS-b-PDLA and P2VP-b-PLLA, respectively. SC formation was achieved by mixing PS-b-PDLA and P2VP-b-PLLA chloroform solutions containing equimolar PLAs segments, followed by precipitation into n-hexane. The molecular characteristics of the resulting block copolymers (BCPs) were determined by 1H NMR, size exclusion chromatography, and Fourier-transform infrared spectroscopy. The formation of PS-b-SC-b-P2VP and the effect of molecular weight variation of PLA blocks on the resulting polymers, were investigated by differential scanning calorimetry, X-ray powder diffraction, and circular dichroism spectroscopies.

Large area nanodot arrays of PS-b-P2VP with heteropolyacid or metal ions via liquid/liquid interfacial self-assembly

Large area of nanodot arrays of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with inorganic species, including phosphotungstic acid, phosphomolybdic acid or transition metal ions have been fabricated at the planar liquid/liquid interface between pure water and chloroform solution of the block copolymers by adding the aqueous solution of the inorganic species dropwise into the water phase. The nanodots arrange into a quasi-hexagonal pattern, the area reaches to several hundreds of square microns, and the size of the nanodots and the distance between the nanodots can be tuned. The formation of the nanodot arrays is attributed to the interaction between the pyridine groups in the P2VP blocks and the inorganic species through electrostatic interaction or coordination that enhances the hydrophilicity of the block copolymers and leads to aggregation of the P2VP blocks during the adsorption and self-assembly process. This is a novel way to fabricate large area of ordered nanostructures.

Förster Resonance Energy Transfer between Fluorescent Organic Semiconductors: Poly(9,9-dioctylfluorene-alt-benzothiadiazole) and 6,13-Bis(triisopropylsilylethynyl)pentacene

In the present study, an investigation of the electronic excitation energy transfer between two p-type fluorescent semiconductors, F8BT [poly(9,9-dioctylfluorene-alcohol-benzothiadiazole] and TIPS-P [6,13-bis(triisopropylsilylethynyl)pentacene], has been carried out in a chloroform solution using steady-state and time-domain fluorescence techniques. The spectral overlap integral between donor (F8BT) emission and acceptor (TIPS-P) absorption is 2.04 × 1015 nm4/(M cm), and the corresponding critical transfer distance is 53.12 Å. In donor decay dynamics, at the lower acceptor concentrations, the observed results deviate from the Förster theory due to the combined effect of diffusion and energy migration. However, it does not exhibit energy migration and distribution for higher acceptor concentrations, and the system follows the Förster model of resonance excitation energy transfer (FRET). The higher value of the donor-acceptor interaction strength than self-interaction (donor-donor interaction) appears to be responsible for this behavior. Further, in acceptor decay, the appearance of the rise time and its decrease with the acceptor concentration confirms FRET from F8BT to TIPS-P.

Air Stable Chalcogen-Doped Rubicenes with Diradical Character

Air Stable Chalcogen-Doped Rubicenes with Diradical Character

Nanoporous-crystalline and amorphous films of PPO including off-on vapochromic fluorescent 7-hydroxy coumarin guests

This study examines the preparation of nanoporous-crystalline and amorphous films of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) containing 7-hydroxy coumarin (i.e., umbelliferone) for the detection of chloroform vapours. Chloroform is selected as the volatile contaminant model being considered harmful and possibly carcinogenic after prolonged exposure. Umbelliferone is chosen as a fluorescent molecule being mostly unemissive in the solid-state and apolar media. α and β nanoporous-crystalline and amorphous PPO films presenting ≈40 μm thickness have been prepared by casting from carbon tetrachloride, benzene and chloroform solutions, respectively, whereas umbelliferone inclusions (1–2 wt%) have been realized in saturated methanol mixtures. Films show fluorescence maximum at about 430 nm with very low quantum yield (Φ F ) of around 1–2%, and particularly reduced in the α and β PPO films, thus suggesting stronger molecular interactions which might facilitate fluorescence self-quenching. It has demonstrated that the exposure to chloroform vapours under saturated conditions (10 5 ppm) turns rapidly on the fluorescence of the polymer films thanks to the solvation effect of the solvent and in agreement with the Φ F of 7% of umbelliferone in chloroform. Notably, a slower response was detected by using dichlorometane as VOC, possibly due to the weaker H-donor strength with respect to chloroform. It was worth noting, that the phenomenon results fastest for the α PPO films, i.e., in case of the lowest Φ F and quenched emission. Vapochromism appears therefore sensitive to the different fluorophore confinement, and the reported results may open new avenues for the rapid detection of VOC vapours. • Nanoporous-crystalline PPO films were prepared and characterized by WAXD and FTIR. • Umbelliferone inclusions in PPO films showed very low Φ F of around 1–2%. • Exposure to CHCl 3 vapours turned the fluorescence on. • Faster vapochromism for the α and β co-crystalline PPO films.

Synthesis of [99Tc(CO)6]+ Cation under Ambient Conditions

AbstractTechnetium(I) and rhenium(I) hexacarbonyl cations were prepared for the first time at atmospheric pressure and room temperature by treatment of dichloromethane or chloroform solutions of [99TcBr(CO)5] and [ReCl(CO)5] with carbon monoxide in the presence of dry aluminum trichloride. The yield was 17.0 % and 3.1 %, respectively.

Layered optimization strategy enables over 17.8% efficiency of layer-by-layer organic photovoltaics

In this work, layer-by-layer (LbL) type OPVs are constructed with wide bandgap polymer PNTB6-Cl as donor and nonfullerene material BTP-4F-12 as acceptor. The layered optimization strategy is employed via separately incorporating the diphenyl ether (DPE) and 1,8-diiodooctane (DIO) into PNTB6-Cl chlorobenzene solution and BTP-4F-12 chloroform solution. A power conversion efficiency (PCE) of 17.81% was achieved from the optimal LbL type OPVs with two solvent additives, which should be among the top level for LBL type binary OPVs. The incorporation of DPE and DIO can separately induce more ordered PNTB6-Cl and BTP-4F-12 orientation, which should contribute to charge transport with suppressed charge recombination in active layers. Meanwhile, BTP-4F-12 crystallization is strongly increased with the incorporation of DIO, which should facilitate more swell matrix for exciton diffusion in active layers. Over 13% PCE improvement can be realized in LbL type OPVs by incorporating two additives, benefiting from simultaneously improved short circuit current density (JSC) of 26.89 mA cm−2 and fill factor (FF) of 75.79%. Meanwhile, the PCE of optimized LbL type OPVs is higher than that of 17.33% for the optimized OPVs with bulk-heterojunction (BHJ) configuration, which reveals that layered optimization strategy should be a promising approach to achieve highly efficient LbL type OPVs.

Study some specifications of copolymer (PLA-PEG)

This study about the blends of Poly Lactic Acid/ Poly Ethylene Glycol (PLA/PEG) 4000 copolymer at concentrations (9%,6%,3%,0%)) wt%) from (PEG) and (PLA) (5%) (w/w) by using casting solvent method to production films. The nonwoven nano fibrous mats were obtained by electro spinning of (PLA/PEG) solutions in chloroform, at weight ratios (70/30) (v/v), respectively. DSC is employed to measure the crystallinity difference between (PLA/PEG) blends and their nonwovens mats. the thermal properties (DSC) of (PLA/PEG) copolymer blends films and electrospun nano fiber mats such as (Tm) melting temperature, (Tg) glass transition temperature, (Tc) crystallization, Xc crystallinity rate and enthalpy . the FTIR test was done for all samples to figure the nature linking between (PLA) and (PEG),the results were that (6%) (w/w) of (PEG) was the optimized rate to apply Electrospinning method , data of DSC test defined that (Tg) and (Tm) were decreased, and that refer to occurrence physicist cross linking between the used substances (Completely miscible blend) when the electrospinning method was applied, also Xc for these nonwoven mats was decreased which has in turn an important effect on the speed of biodegradble for poly lactic acid (PLA).

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Formation of a solvate of manganese(III) acetylacetonate with chloroform

Metal acetylacetonates are coordination compounds consisting of the acetylacetonate anion (CH3COCHCOCH3, indicated as acac) and metal ions. Typically, both oxygen atoms of the anion bind with the metal and form a six-membered chelate ring. The simplest complexes have the formulas M(acac)3 and M(acac)2. Many complexes are soluble in organic solvents, and such solutions are used for the synthesis of catalysts. The processes of formation of solvates of acetylacetonates of various metals have not been studied properly. It should be noted that the determination of the composition and properties of solvates is important for understanding the peculiarities of the extraction processes of metal acetylacetonates.Manganese(III) acetylacetonate Mn(acac)3, for example, is also widely used. The recrystallisation of the complex is most commonly conducted from solutions in chloroform, and in this case, the corresponding solvates may be formed, which can affect the structure and properties of Mn(acac)3. There are no data on the synthesis conditions and the composition of the solvates of manganese(III) acetylacetonate with chloroform. Therefore, the purpose of this work is to study the possibilities of its formation and to establish the composition of such solvates. The formation of the solvate in solution was established using Fourier IR spectroscopy by the shift of the absorption band of the C-H chloroform bond. The composition of the Mn(acac)3· 2CHCl3 solvate was determined using gravimetric analysis.

A comprehensive linear and nonlinear study on a fluorescent stain

The optical properties, linear and nonlinear, for Leishman stain are studied in ethanol and chloroform over a wide spectral region. The stain consists of two components: Methylene blue (MB) and Eosin (E). The low intensity optical measurements, linear regime, show the absorption and emission characteristics of the E and the MB components in ethanol and only the MB component in chloroform. Under the influence of optical intensity less than 15[Formula: see text]MW/m2, the stain shows nonlinear absorption characteristics at excitation wavelengths 532[Formula: see text]nm and 650[Formula: see text]nm only. The nonlinear absorption coefficients of the solutions are in 1–12.4 [Formula: see text][Formula: see text] cm/W range in both solvents. Leishman stain solutions in ethanol and chloroform have a strong thermal nonlinearity with a negative index of refraction over the entire visible region. The value of the nonlinear refractive index ([Formula: see text]) of Leishman stain in both solvents increases as the wavelength of the excitation radiation increases. The value of [Formula: see text] of the solutions is in the range of about 2–46 [Formula: see text][Formula: see text][Formula: see text]cm2/W. As an example of the optoelectronic applications, the stain shows excellent properties of an energy spreading optical limiter.

Highly Fluorescent Dyes Containing Conformationally Restrained Pyrazolylpyrene (Pyrazoolympicene) Chromophore.

The triflic-acid-promoted cyclization of 1-phenyl-3-(pyren-1-yl)-1H-pyrazole-4-carbaldehyde afforded a mixture of 9-phenyl-7,9-dihydropyreno (10,1-fg)indazole and 9-phenylpyreno(10,1-fg)indazole-7(9H)-one, readily separable by column chromatography. Both products contained a rigid six-ringed pyrazoolympicene backbone and exhibited bright fluorescence in chloroform solution and a weak fluorescence in the solid state. DFT and TD DFT calculations revealed that the lowest excited state (S1) of these compounds is populated via HOMO →LUMO π-π * transition. Furthermore, the synthesized compounds behaved as weak bases and their emission spectra showed substantial changes upon protonation. Therefore, they may be of interest for sensing of strongly acidic fluorophore environments.

Synthesis and Characterization of Partially Biobased Aromatic (Co)polycarbonates Containing Biphenylene Units and Pendant Pentadecyl Chains

Abstract2‐Pentadecyl‐[1,1”‐biphenyl]‐4,4”‐diol (PBD) is synthesized starting from cashew nut shell liquid—a by‐product of cashew processing industry. A new series of partially biobased aromatic (co)polycarbonates possessing biphenylene units and pendant pentadecyl chains is synthesized by solution polycondensation of PBD or varying compositions of PBD and bisphenol‐A with triphosgene in dry dichloromethane. Inherent viscosities and number average molecular weights of (co)polycarbonates are in the range 0.51–1.24 dL g−1and 18 × 103– 43.4 × 103 g mol−1, respectively indicating the formation of reasonably high molecular weight polymers. Flexible, transparent, and free‐standing films of (co)polycarbonates can be cast from chloroform solution. (Co)polycarbonates are characterized using Fourier transform infrared spectroscopy (FTIR),1H NMR,13C NMR spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry, and thermogravimetric analysis.T10andTgvalues of (co)polycarbonates are in the range 417–433 and 8–147 °C, respectively. It is demonstrated that theTgvalues can be tuned by incorporation of appropriate mol% of PBD as a comonomer in Bisphenol‐A‐based copolycarbonates. The lowering of theTgvalues of (co)polycarbonates can be attributed primarily to the packing disruptive effect of flexible pentadecyl chains. Furthermore, the effect of incorporation of PBD as a comonomer on water contact angle values of (co)polycarbonates is evaluated.

Synthesis and spectroscopic characterization of 3-(3,4-dimethoxyphenylethylamino)-methylidene-1,2,3,9-tetrahydropyrrolo[2,1-b]-quinazolin-9-one and crystal structure of its hydrochloride

The structure of 3-(3,4-dimethoxyphenylethylamino)-methylidene-1,2,3,9-tetrahydropyrrolo[2,1-b]-quinazolin-9-one hydrochloride was determined by single-crystal X-ray diffraction at 100 K. The compound crystallizes in the monoclinic space group Cc, with a = 4.7149(18), b = 30.075(12), c = 14.199(6) Å, β = 91.852(8)°, Z = 4, V = 2012.4(14) Å3. The crystallographic study revealed E configuration of the C11 = N9′ bond. Electrostatic interactions between the organic cation and the chloride anion and classical N-H…Cl hydrogen bonds stabilize this salt. A Hirshfeld surface analysis revealed that H···H, H···C/C···H, and H···O/O···H represent the most prominent Van-der-Waals contacts. For the neutral parent molecule, nuclear magnetic resonance spectroscopy in deuterated chloroform solution showed that two tautomeric forms coexist in 3:1 ratio.

Remotely controllable supramolecular rotor mounted inside a porphyrinic cage

Remotely controllable supramolecular rotor mounted inside a porphyrinic cage

An investigation of the predominant structure of antibiotic azithromycin in chloroform solution through NMR and thermodynamic analysis.

Azithromycin (AZM) is a well-known macrolide-type antibiotic that has been used in the treatment of infections and inflammations. Knowledge of the predominant molecular structure in solution is a prerequisite for an understanding of the interactions of the drug in biological media. Experimental structural determination can be carried out for samples in solid-state (X-ray diffraction technique) and gas phase (electron diffraction experiment). In solution, spectroscopic methods can be used to extract valuable information which combined with quantum chemical calculations can lead to the determination of the preferred molecular structures to be observed when a given solute is dissolved in each solvent. That is precisely the aim of this work. We used experimental NMR chemical shift data (in CDCl3) as a reference for comparison with Density Functional Theory (DFT) NMR calculations, with geometry optimized having as guess input two crystallographic structures available in the literature with the configuration of all chiral carbon atoms inverted, named here A and B. The Polarizable Continuum Model (PCM) was used to describe the solvent effects (chloroform) including five explicit CHCl3 solvent molecules, which we believe can account for short and long-range solute-solvent interactions. Analysis of calculated thermodynamic, NMR chemical shift, MAE (Mean Absolute Error), and spin-spin coupling constant values revealed that both supposable C3R-C5S (named M2-A) and C3S-C5R (named M2-B) structures are equally probable to exist in chloroform solution. In addition, we found that the heavy atoms' conformation is reasonably similar in the solid-state and chloroform solution; however, regarding the OH groups, the spatial orientations are rather different with intramolecular OH⋯N and OH⋯O hydrogen bonds present in solution and with some of them being absent in the X-ray structure probably due to crystal packing effects.

Влияние озона на структуру биоразлагаемых матриц на основе смесей поли(3-гидроксибутирата), полилактида и хитозана

Changes in fibrous and film materials based on mixtures of biodegradable polyesters polyhydroxybutyrate, polylactide, and chitosan polysaccharide during ozonolysis were studied by the structural-dynamic EPR method using a stable nitroxyl radical—the TEMPO probe. Fibers and films were obtained from solutions in chloroform, respectively, by electrospinning and casting onto glass. It is shown that the lower packing density in the amorphous regions of mixed samples determines the increased rate of their oxidation by ozone compared to homopolymers. A two-stage kinetic mechanism of ozonolysis has been demonstrated, including the formation of side groups and subsequent degradation of the polymer chain. It has been found that the activation energy of probe rotation depends on the amount of polymer in the mixture, while the activation barrier is minimal for polyester mixtures in the same concentration range where the ozonolysis constants are maximum. It has been shown that the presence of chitosan in ternary compositions leads to an increase in the degree and rate of ozonolysis.

Kinetic trapping of a cobalt(ii) metallocage using a carbazole-containing expanded carbaporphyrinoid ligand.

The meso-unsubstituted expanded porphyrinoid 3, incorporating two carbazole moieties, acts as an effective ligand for Co(ii) and permits the isolation and X-ray diffraction-based characterization of a 6 : 3 metal-to-ligand metallocage complex that converts spontaneously to the constituent 2 : 1 metal-to-ligand metalloring species in chloroform solution. The discrete metalloring is formed directly when the Co(ii) complex is crystallized from supersaturated solutions, whereas crystallization from more dilute solutions favors the metallocage. Studies with two other test cations, Pd(ii) and Zn(ii), revealed exclusive formation of the monomeric metalloring complexes with no evidence of higher order species being formed. Structural, electrochemical and UV-vis-NIR absorption spectral studies provide support for the conclusion that the Pd(ii) complex is less distorted and more effectively conjugated than its Co(ii) and Zn(ii) congeners, an inference further supported by TD-DFT calculations. The findings reported here underscore how expanded porphyrins can support coordination modes, including bimetallic complexes and self-assembled cage structures, that are not necessarily easy to access using more traditional ligand systems.

Excited state absorption of DNA bases in the gas phase and in chloroform solution: a comparative quantum mechanical study.

We study the excited state absorption (ESA) properties of the four DNA bases (thymine, cytosine, adenine, and guanine) by different single reference quantum mechanical methods, namely, equation of motion coupled cluster singles and doubles (EOM-CCSD), singles, doubles and perturbative triples (EOM-CC3), and time-dependent density functional theory (TD-DFT), with the long-range corrected CAM-B3LYP functional. Preliminary results at the Tamm-Dancoff (TDA) CAM-B3LYP level using the maximum overlap method (MOM) are reported for thymine. In the gas phase, the three methods predict similar One Photon Absorption (OPA) spectra, which are consistent with the experimental results and with the most accurate computational studies available in the literature. The ESA spectra are then computed for the ππ* states (one for pyrimidine, two for purines) associated with the lowest-energy absorption band, and for the close-lying nπ* state. The EOM-CC3, EOM-CCSD and CAM-B3LYP methods provide similar ESA spectral patterns, which are also in qualitative agreement with literature RASPT2 results. Once validated in the gas phase, TD-CAM-B3LYP has been used to compute the ESA in chloroform, including solvent effects by the polarizable continuum model (PCM). The predicted OPA and ESA spectra in chloroform are very similar to those in the gas phase, most of the bands shifting by less than 0.1 eV, with a small increase of the intensities and a moderate destabilization of the nπ* state. Finally, ESA spectra have been computed from the minima of the lowest energy ππ* state, and found in line with the available experimental transient absorption spectra of the nucleosides in solution, providing further validation of our computational approach.

Development of the Spectrophotometric Method for the Determination of Atorvastatin Calcium in Tablets by using Bromophenol Blue

A simple, rapid, and inexpensive spectrophotometric method for the determination of atorvastatin calcium in tablets has been developed. It requires only one reagent (BPB) and suitable for routine pharmaceutical analysis with less sophisticated equipment. The procedure for atorvastatin determination is based on its interaction with bromophenol blue (BPB) in medium of organic solvent. As a result of the reaction, the intensity of the band of the doubly ionized form of the BPB with a maximum at 595 nm increases. The maximum analytical signal is observed in a solution of methanol, chloroform, or acetonitrile, while ethanol and ethyl acetate turned out to be unsuitable. The optimal concentration of BPB is 4.12·10-4 M. To study the stability, the absorbance of the obtained solution was measured under optimal conditions for 45 min. The stoichiometric ratio of components in the resulting associate, determined by the method of continuous variations, is 1:1. The calibration graph is linear in the range from 4.1 to 33 μmol/L. The calculated LOD and LOQ values were 1.36 μmol/L and 4.13 μmol/L, respectively. The systematic error of the method is statistically insignificant in the whole range of calibration graph. The developed method was successfully applied for the determination of atorvastatin in tablets.