Amphiphilic copolymers with poly(meth)acrylic acid chains “grafted from” caprolactone 2‐(methacryloyloxy)ethyl ester‐based backbone

Well‐defined amphiphilic graft copolymers containing hydrophilic poly((meth)acrylic acid) (PMAA) or poly(acrylic acid) (PAA) side chains with gradient and statistical distributions were synthesized. For this purpose, the hydroxy‐functionalized copolymers with various gradient degrees, in which 2‐(6‐hydroxyhexanoyloxy)ethyl (meth)acrylate units (caprolactone 2‐[methacryloyloxy]ethyl ester, CLMA) formed strong gradient with tert‐butyl acrylate (tBA), slight gradient copolymers with tert‐butyl (meth)acrylate (tBMA), and statistical copolymers with methyl (meth)acrylate (MMA) were modified to bromoester multifunctional macroinitiators, P(tBMA‐grad‐BrCLMA), P(BrCLMA‐grad‐tBA), and P(BrCLMA‐co‐MMA). In the next step, they were applied in controlled radical polymerization of tBMA and tBA yielding graft copolymers with various lengths of side chains as well as graft densities. Further, the tert‐butyl groups in copolymers were successfully removed via acidolysis in the presence of trifluoracetic acid, which caused transformation of the hydrophobic graft copolymers into amphiphilic ones with ability of self‐assembly for the future biomedical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Examination of the structure in solid state of amino analogs of 4,4′-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, C CP/MAS NMR, and theoretical calculations

A single crystal of X-ray diffraction structures is presented for 4,4′-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4′-[1,5-(N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/gauche conformation, whereas in 3 – a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of NH···N in 2 and of CH···N in 3. Various conformations of both molecules were reflected in ¹³C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.     

A novel thin layer chromatography–flame ionization detection method for saturated,asphaltenes, resins,and asphaltenes group-type composition analysis with reverse order of chromatogram development

The methodologies of asphaltenes-containing petroleum materials: saturated, aromatics, resins, asphaltenes group-type composition analysis are performed with the use of column adsorption-desorption or thin layer chromatography (TLC)-flame ionization detection under normal phase conditions with silica gel as the adsorbent. In a three-step procedure, the TLC chromatogram is developed within a decreasing distance by the mobile phase with increasing elution strength (polarity). The n-alkane used in the first step does not dissolve asphaltenes, which leads to the occlusion effect and an underestimation of the percentage of saturated hydrocarbons. In this article, the reverse order of the subsequent elution steps was proposed: the solvent polarity is simultaneously reduced and the chromatogram development distance is increased in the order dichloromethane:methanol 95:5 v/v, 3 cm; toluene, 6 cm; and n-hexane, 10 cm. It was also intentional to reduce the weight of the applied sample to 5 μg for bitumen and 2 μg for asphaltene purity testing. It should be the rule that in stepwise TLC chromatogram development, the first mobile phase is a good solvent for all testing components. The IP 469 procedure should be corrected.     

Electron ionisation and electrospray ionisation mass spectrometric study of a series of isomeric methyl-, dimethyl- and trimethylalloxazines

Electron ionisation (EI) mass spectra and electrospray ionisation (ESI) mass spectra at different cone voltages of a series of isomeric methyl- and dimethylalloxazines are discussed, and compared with those of lumichrome, and 1- and 3-methyllumichrome. Examination of ESI mass spectra taken at a higher cone voltage and the use of isotope-labelled methanol allow us to discuss the fragmentation pathways of [M+H]+ and [M-H](-) ions. The fragmentation pathways of all of the compounds and the characteristic fragment ions formed in EI-MS are compared with published data. The influence of methyl and dimethyl substituents in the benzene ring on the fragmentation pathways leading to the loss of 43 and 45 Da upon both electron and electrospray ionisation is described.     

Isomorphism in 1‐(2‐halidobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium halide hemihydrates (halide = Cl,Br)

The crystal structures of two (E)‐stilbazolium salts, namely 1‐(2‐chlorobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium chloride hemihydrate, C₂₀H₁₇ClNO⁺·Cl⁻·0.5H₂O, (I), and 1‐(2‐bromobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium bromide hemihydrate, C₂₀H₁₇BrNO⁺·Br⁻·0.5H₂O, (II), are isomorphous; the isostructurality index is 99.3%. In both salts, the azastyryl fragments are almost planar, while the rings of the benzyl groups are almost perpendicular to the azastyryl planes. The building blocks of the structures are twofold symmetric hydrogen‐bonded systems of two cations, two halide anions and one water molecule, which lies on a twofold axis. In the crystal structure, these blocks are connected by means of weaker interactions, viz. van der Waals, weak hydrogen bonding and stacking. This study illustrates the robustness of certain supramolecular motifs created by a spectrum of intermolecular interactions in generating these isomorphous crystal structures.     

Photophysics of Soret-excited tetrapyrroles in solution. I. Metalloporphyrins: MgTPP, ZnTPP, and CdTPP

The photophysical behavior of three Soret-excited diamagnetic meso-substituted tetraphenylmetalloporphyrins, MgTPP, ZnTPP, and CdTPP, have been examined in a wide variety of solvents using both steady-state and femtosecond fluorescence upconversion methods. The S 2 population of MgTPP decays to S 1 on the time scale of a few picoseconds with unit S 2-S 1 internal conversion efficiency, and the decay rates conform to the weak coupling case of radiationless transition theory. The energy gap law parameters characterizing the coupling of the S 2 and S 1 states of MgTPP have been obtained. The most important accepting vibrational modes in the S 1 state are multiple in-plane C-C and C-N stretches in the 1200-1500 cm (-1) range. Net S 2-S 1 decay is the dominant decay path for ZnTPP and CdTPP as well, but the process occurs at rates that exceed (in the case of CdTPP, they vastly exceed) those predicted by weak interstate coupling. Alternate mechanisms for the radiationless decay of the S 2 states of ZnTPP and CdTPP have been explored. Large spin-orbit coupling constants and the presence of multiple, near-equiergic triplet states suggest that S 2-T n intersystem crossing might occur at rates competitive with internal conversion. However, the measured efficiencies of S 2-S 1 internal conversion show that, at most, only a few percent of the S 2 population of ZnTPP and no more than about 30% of the S 2 population of CdTPP can decay by a "dark" path such as intersystem crossing.     

An HPLC-DAD and LC-MS study of condensation oscillations with S(+)-ketoprofen dissolved in acetonitrile

In our earlier studies, a spontaneous chiral conversion of the selected low-molecular-weight carboxylic acids (i.e., amino acids, hydroxy acids, and profen drugs) dissolved in aqueous ethanol medium, running in vitro was described. Then it became clear that this spontaneous chiral conversion is accompanied by the spontaneous condensation of the discussed compounds. With several acids, it was established that this condensation is also oscillatory in nature. The theoretical models were developed aiming to give a rough explanation of the observed non-linear processes. In this paper, the results of these studies on the dynamics of condensation with S(+)-ketoprofen, a very popular profen drug, when stored for certain amount of time dissolved in a non-aqueous medium (i.e., acetonitrile) is presented. These investigations were carried out with the aid of two independent high-performance liquid chromatographic systems with the diode array detection and of a third high-performance liquid chromatographic system equipped with mass spectrometric detection. In one cycle of chromatographic measurements, it was possible to monitor condensation of S(+)-ketoprofen in 25-min intervals for 30 h, thus obtaining kinetic information on the progress of this process. Mass spectrometric detection confirmed the presence of new species in the stored solution with molecular weights much higher than that of S(+)-ketoprofen, which can be attributed to the condensation products. The obtained data show that condensation of S(+)-ketoprofen dissolved in acetonitrile progresses in a rapid manner, and that the observed oscillatory concentration changes with S(+)-ketoprofen and with the main condensation product characterize with an irregularity and shallow amplitudes. A theoretical model was referenced that jointly describes the oscillatory chiral conversion and the oscillatory condensation with the low-molecular-weight chiral carboxylic acids.     

Generating singlet oxygen bubbles: a new mechanism for gas-liquid oxidations in water

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [(1)O(2) ((1)Δ(g))] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiberoptic receptacles loaded with 150 μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O(2) gas to the reactor chambers. In the presence of O(2), singlet oxygen was generated by illuminating the sensitizer particles with 669 nm light from an optical fiber coupled to the top of the reactor. The generated (1)O(2) was transported through the membrane by the O(2) stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, or N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that (1)O(2) transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow; it arose only from (1)O(2)-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves (1)O(2) mass transfer and solvation, where smaller bubbles provide better penetration of (1)O(2) into the flowing stream due to higher surface-to-volume contact between the probe molecules and (1)O(2).