Dissociative ionization of 1,4-bis(2,5-phenyloxazolyl)benzene

Dissociative ionization of 1,4-bis(2,5-phenyloxazolyl)benzene (POPOP) molecule by electron impact in gaseous phase is studied. Potentials of appearance of some fragments of the molecule under study are determined from the experimentally measured dependences of ionization cross-section on the ionizing electron energy. A new ion with m/z = 144 [C₉H₆ON]⁺ is detected in the mass spectrum of the POPOP molecule, being complementary to the fragment with m/z = 220 [C₁₅H₁₀ON]⁺. The threshold of appearance of this ion is determined (E_ap = 9.51 eV) as well as the first ionization potential of the POPOP molecule and fragment ion appearance potentials.     

Preparation and complexation of an A–B–A type triblock copolymer consisting of helical poly(L-proline) and random-coil poly(ethylene oxide)

By using L -proline N-carboxyanhydride (LPNCA) and amino-group terminated poly(ethylene oxide) (ATPEO), an A–B–A–type [A = poly(L -proline) (PLP), B = poly(ethylene oxide) (PEO)] triblock copolymer (POP) was prepared which is water-soluble. In the POP, A = PLP is helical, and B = PEO is random coil. From the observations of the NMR spectra, specific optical rotation, and x-ray diffraction of the POP, it was found that the PLP component of the POP exists nearly as Form II PLP with trans-configuration, and interferes the crystal growth of PEO component, in solid state. With the addition of PMAA into an aqueous POP solution, dramatic decreases of reduced viscosity and pH are observed until the unit-mole-concentration-ratio (UMCR) [PMAA]/[POP] reaches its value of unity, while a distinct increase in turbidity appears. This shows a 1 : 1 interpolymer complex formation between PMAA and POP in aqueous medium through hydrogen bonding. The curves of viscosity, pH, and turbidity versus UMCR [PMAA]/[POP] show breaks at [PMAA]/[POP] = 0.3, suggesting the selective complexation of PLP component (ca. 30 unit-mol %) of POP with PMAA. The x-ray diffraction curve of the complex POP/PMAA shows entirely no diffraction patterns, indicating that the ordered POP structure (mainly due to that of PLP component) is completely destroyed owing to the complexation between POP and PMAA.     

(Systemic) phototoxicity of drugs and other xenobiotics.

Xenobiotics extensively used in drugs, cosmetics, food and agricultural chemicals can produce adverse biological effects. These toxic effects are separated into classes, e.g. hepatotoxicity, genotoxicity and neurotoxicity. Skin allergy, part of immunotoxicity, is also a subdivision of toxicology. When light is an essential condition for toxicity, the xenobiotic is called phototoxic. Thus it fits into the logic of toxicology that photoallergic compounds are a subdivision of phototoxic compounds. Phototoxicons as a group do not differ from the group of phototherapeutics with regard to their eventual biological effects. The primary photoreactions, secondary molecular processes, biomolecules involved and cellular and tissue damage are similar. The difference between the two groups is in the appreciation of the photobiological effects: adverse vs. desired. The aim of research is to determine the part of the molecular structure which makes a given compound phototoxic. With that knowledge the structure of the phototoxicon can be changed. This can result in a derivative which still has the desired properties of the parent compound, but is no longer phototoxic. This aim can be reached by combining data from both in vitro and in vivo research. The variety and number of phototoxic compounds is large. This, together with the limited research effort devoted to this subject so far, means that for most phototoxic xenobiotics a relationship between structure and in vivo photoreactivity is not available. In this review, emphasis is placed on xenobiotics whose in vitro and in vivo photochemistry have been studied. Furthermore, possible phototoxic effects which do not concern the skin but involve inner organs (systemic effects) are considered. References in this review mostly concern investigations over the last 10 years. For older literature or for additional information, references to other reviews are given. Important groups of phototoxic xenobiotics not dealt with in this article were already sufficiently covered in the reviews referred to.     

Synthesis and evaluation of poly(oxyethylene glycol) polymer (POP) supports

Mono- and alpha,omega-bis-styryl-oligo(oxyethylene glycol) ethers have been constructed in an efficient two-step synthesis. From these precursors, poly(oxyethylene glycol) polymer (POP) supports of varying monomer and cross-linker composition have been produced. The swelling properties and mass-solvent uptake of these novel materials have been evaluated in a variety of solvents, demonstrating that POP supports exhibit enhanced solvent compatibilities over the commercial resins TENTA-GEL, ARGO-GEL, and Merrifield's resin. The utility of POP supports in solid-phase organic chemistry has also been demonstrated successfully. It is anticipated that these high-loading polymeric supports will have generic application in the solid-phase synthesis of combinatorial libraries and the in situ screening of these libraries in the aqueous environment of a bioassay.     

POPOP诱导环糊精形成纳米管的研究

用紫外吸收光谱、稳态荧光、荧光各向异性和动态光散射等方法研究了2,2′-p-亚苯基-双(5-苯基噁唑) (POPOP)分子与环糊精(CD)的相互作用. 结果表明, POPOP分子在浓度较低时与β-CD形成1:2的包合物, 在浓度较高时可以进一步诱导β-CD形成纳米管结构. 同时发现, POPOP分子也可以诱导γ-CD形成纳米管结构. 对比于β-CD, POPOP分子在γ-CD水溶液中的荧光发射峰, 不仅有明显的红移而且也缺失了精细结构, 呈现较宽的大包峰. 这是由于POPOP分子成对进入γ-CD空腔形成了激基缔合物的缘故. pH和温度效应实验进一步表明, POPOP诱导β-CD形成的纳米管在pH大于12和温度高于331 K的环境下不能稳定存在.     

Double silyl migration converting ORe[N(SiMe(2)CH(2)PCy(2))(2)] to NRe[O(SiMe(2)CH(2)PCy(2))(2)] substructures

The reaction of (R(2)PCH(2)SiMe(2))(2)NM (PNP(R)M; R = Cy; M = Li, Na, MgHal, Ag) with L(2)ReOX(3) [L(2) = (Ph(3)P)(2) or (Ph(3)PO)(Me(2)S); X = Cl, Br] gives (PNP(Cy))ReOX(2) as two isomers, mer,trans and mer,cis. These compounds undergo a double Si migration from N to O at 90 degrees C to form (POP(Cy))ReNX(2) as a mixture of mer,trans and fac,cis isomers. Additional thermolysis effects migration of CH(3) from Si to Re, along with compensating migration of halide from Re to Si. DFT calculations on various structural isomers support the greater thermodynamic stability of the POP/ReN isomer vs PNP/ReO and highlight the influence of the template effect on the reactivities of these species.     

Thermal and structural properties of binary mixtures of 1,3-distearoyl-2-oleoyl-glycerol (SOS) and 1,2-dioleoyl-3-stearoyl-sn-glycerol (sn-OOS)

We have conducted thermal and X-ray diffraction experiments on binary mixtures of symmetric stearic-oleic mixed-acid triacylglycerol (TAG) (1,3-distearoyl-2-oleoyl-glycerol: SOS) and asymmetric stearic-oleic mixed-acid TAG (1,2-dioleoyl-3-stearoyl-sn-glycerol: OOS), in which optically active sn-OOS was employed. We found that SOS–OOS mixtures exhibited immiscible monotectic or peritectic mixing behavior. This result was consistent with previous study on binary mixtures of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), in which racemic rac-OOP molecules were employed. The differences between the SOS–OOS and POP–OOP mixtures were in the polymorphic behavior of the fractions of POP and SOS. No effect was found from using an optically active (sn-OOS) or racemic mixture (rac-OOP) as an asymmetric oleic–oleic-saturated acid TAG. From the two results, we may conclude that an immiscible phase was formed in the binary mixtures of symmetric saturated-oleic-saturated TAGs and asymmetric oleic–oleic-saturated TAGs, of both racemic and optically active types. This result stands in contrast to mixtures of SOS–OSO (1,3-dioleoyl-2-stearoyl-glycerol), SOS–SSO (1,2-distearoyl-3-oleoyl-rac-glycerol), POP–OPO (1,3-dioleoyl-2-palmitoyl-glycerol), and POP–PPO (1,2-dipalmitoyl-3-oleoyl-rac-glycerol), all of which exhibited molecular-compound-forming behavior with molecular compound crystals at an equal ratio of the binary mixtures. Molecular-level mechanisms to explain this difference are discussed, based on possible roles of glycerol groups acting during the mixing processes of saturated–unsaturated mixed-acid TAGs.     

A phosphorescent copper(I) complex: synthesis, characterization, photophysical property, and oxygen-sensing behavior

In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Np)(POP)]BF4, where Phen-Np and POP stand for 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(Phen-Np)(POP)]BF4 renders a yellow phosphorescence peaking at 545 nm, with a long excited state lifetime of 4.69 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Np)(POP)]BF4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ～300 nm exhibit a maximum sensitivity of 7.2 towards molecular oxygen with short response time of 7s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.     

Synthesis and characterization of segmented liquid crystal poly(azoxy polyester-co-polyoxypropylene)

In this study a series of a segmented copolyester, poly(4,4′-dioxy-2,2′-dimethyl-azoxybenzene dodecanedioyl) (PMABD)-co-polyoxypropylene 400 (POP), was prepared. The chain length of PMABD studied (n) was varied from 7.8-18.2, and that of POP was unchanged. The intrinsic viscosity of the segmented copolyesters was 1.04-1.30, and the number average molecular weight obtained was 2.53 × 10⁴?3.49 × 10⁴ g/mol. The mesophase texture and thermal properties of the segmented copolyesters were measured as functions of n. It was found that the insert of flexible POP between those liquid crystalline domains of PMABD did affect thermotropic properties of PMABD. As the n value was 9.0 and 7.8 (or 7.4 and 8.6% by weight POP) the texture appeared as cholesteric-like oily streaks. The effect could not be attained by simply copolymerizing a mesogenic moiety with a pair of spacers of different lengths. The fluidity and domain structure of the flexible dodecanedioyl-POP-dodcanedioyl segments are taken into account for the obtained results. © 1995 John Wiley & Sons, Inc.     

Synthesis and interfacial behaviors of amphiphilic poly(oxypropylene) amidoacids

A series of hydrophobic poly(oxypropylene) (POP)‐backboned and hydrophilic poly(oxyethylene)‐backboned amidoacids and imidoacids were prepared through the reaction of poly(oxyalkylene) diamines and trimellitic anhydride (TMA) under mild conditions. The synthesized copolymers were characterized with nuclear magnetic resonance and Fourier transform infrared. Their ability to lower the water surface tension and toluene/water interfacial tension was measured and correlated with the hydrophobic/hydrophilic balance with multiple sodium carboxylate functionalities. The specific POP2000/TMA copolymers, consisting of a 2000 g/mol POP segment and multiple amidoacid functionalities, enabled the demonstration of a strong surfactant tendency and a critical micelle concentration at 0.1 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 646–652, 2006     

Formation of cyclodextrin nanotube induced by POPOP molecule

The interaction between 2,2′-p-phenylenebis (5-phenyloxazol) (POPOP) and cyclodextrins (CDs) was investigated using UV-Vis absorption, steady-state fluorescence, and dynamic light scattering (DLS). The results indicated that POPOP could form the 1:2 (guest:host) inclusion complex with β-CD at lower concentrations, which could further form the extended nanotube at higher concentrations. POPOP could also induce the formation of the nanotube of γ-CD. The fluorescence emission of POPOP in aqueous solution of γ-CD showed obvious red shift accompanied by the disappearance of fine structure compared with that in aqueous solution of β-CD, which could be attributed to the formation of the excimer of POPOP in the larger cavity of γ-CD. It was found that at pH greater than 12, the hydrogen bond between the neighboring CDs was destroyed, which led to the collapse of the nanotubular structure. The results also showed that the nanotube structure was not stable at temperatures above 331 K.     

Four-coordinate N-heterocyclic carbene (NHC) copper(I) complexes with brightly luminescence properties

Three four-coordinate N-heterocyclic carbene (NHC) copper(I) complexes, [Cu(Py-Im)(POP)](PF₆) (P1), [Cu(Py-BenIm)(POP)](PF₆) (P2), and [Cu(Py-c-BenIm)(POP)](PF₆) (P3) (Py-Im = 3-methyl-1-(pyridin-2-yl)-1H-imidazolylidene, Py-BenIm = 3-methyl-1-(pyridin-2-yl)-1H-benzo[d]imidazolylidene, Py-c-BenIm = 3-methyl-1-(pyridin-2-ylmethyl)-1H-benzo[d]imidazolylidene, POP = bis([2-diphenylphosphino]-phenyl)ether), have been synthesized without transmetalation of the NHC–Ag(I) complex for the first time. The photophysical properties of the resultant NHC–Cu(I) complexes have been systematically investigated via spectroscopic methods. All complexes exhibit good photoluminescence properties with long excited-state lifetimes and moderate quantum yields. Density functional theory and time dependent density functional theory calculations were employed to rationalize the photophysical properties of the NHC–Cu(I) complexes.     

On the molecular mechanism of clouding in aqueous solution of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers

The physical aspects of the clouding phenomenon in the aqueous solution of a poly(oxyethylene)(POE) – poly(oxypropylene)(POP) – poly(oxyethylene)(POE) triblock copolymer were investigated by applying various experimental methods: viscometry, ultrasonic technique, light scattering, infrared and Raman spectroscopy. The ultrasonic absorption studies hint at a critical behaviour. In order to understand the spectroscopic findings, conformational energies of model POE molecules as well as interaction energies between oxyethylene (OE) units and water molecules were calculated by the use of the quantum chemical PCILO method. It is suggested that the clouding is connected with conformational changes of POE segments.     

几种聚醚胺改性蒙脱土对环氧树脂固化过程的影响

首先制备了五种聚醚胺改性蒙脱土(MMT), 并将这五种聚醚胺改性蒙脱土加入到双酚A 型环氧树脂E51 和聚醚胺D400体系中, 采用差示扫描量热法(DSC)考察了五种聚醚胺改性MMT对环氧树脂升温固化进程的影响. 随后, 优选一种EP/MMT 混合体系即EP/D400-T500-MMT 混合体系, 系统地研究了该体系与纯环氧树脂体系在130, 140, 150 及160 ℃等几个温度下的等温固化过程, 考察了等温固化时间对固化度和固化度变化速率的影响以及固化度与固化度变化速率之间的关系, 并利用Kamal 模型进行拟合计算了固化动力学参数. 研究结果表明, 与纯环氧树脂相比, 几种聚醚胺改性MMT 的固化放热峰均向高温迁移, 同时聚醚胺D400 协同插层MMT 降低了高分子量聚醚胺插层MMT 所导致的环氧树脂DSC 曲线的畸变情况; EP/D400-T500-MMT 混合体系和纯环氧体系的等温固化反应过程符合Kamal 模型;在相同的固化温度下, EP/D400-T5000-MMT 混合体系的反应速率常数k₁ 和k₂ 值以及反应级数m 均比纯EP 体系小, 而反应级数n 以及总反应级数m+n 值比纯EP 体系大, 表明两种聚醚胺协同插层的改性蒙脱土D400-T5000-MMT 的加入降低了环氧体系固化反应速率. 另外, EP/D400-T5000-MMT 混合体系的活化能E_a1 和E_a2 与纯EP 体系的相比也略有升高.     

Synthesis,characterization, photophysical and oxygen-sensing properties of a copper(I) complex

In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(TBT)(POP)]BF₄, where TBT and POP stand for 4,5,9,14-tetraaza-benzo[b]triphenylene and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(TBT)(POP)]BF₄ renders a red phosphorescence peaking at 622 nm, with a long excited-state lifetime of 13.2 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(TBT)(POP)]BF₄ and polystyrene, hoping to explore the possibility of replacing precious-metal-based oxygen sensors with cheap Cu-based ones. The finally obtained samples with average diameter of ~700 nm exhibit a maximum sensitivity of 5.8 toward molecular oxygen with short response/recovery time (5/13 s) due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples. All these results suggest that phosphorescent Cu(I) complexes doped nanofibrous membranes are promising candidates for low-cost and quick-response oxygen-sensing materials.     

Combining Topological and Steric Constraints for the Preparation of Heteroleptic Copper(I) Complexes

Heteroleptic copper(I) complexes have been prepared from a macrocyclic ligand incorporating a 2,9‐diphenyl‐1,10‐phenanthroline subunit ( M30 ) and two bis‐phosphines, namely bis[(2‐diphenylphosphino)phenyl] ether (POP) and 1,3‐bis(diphenylphosphino)propane (dppp). In both cases, the diphenylphosphino moieties of the PP ligand are too bulky to pass through the 30‐membered ring of M30 during the coordination process, hence the formation of C_2v‐symmetrical pseudo‐rotaxanes is prevented. When POP is used, X‐ray crystal structure analysis shows the formation of a highly distorted [Cu( M30 )(POP)]⁺ complex in which the POP ligand is only partially threaded through the M30 unit. This compound is poorly stable as the Cu^I cation is not in a favorable coordination environment due to steric constraints. By contrast, in the case of dppp, the bis‐phosphine ligand undergoes both steric and topological constraints and adopts a nonchelating coordination mode to generate [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂. This compound exhibits metal‐to‐ligand charge transfer (MLCT) emission characterized by a very large Stokes’ shift (≈200 nm) that is not attributed to a dramatic structural distortion between the ground and the emitting states but to very weak MLCT absorption transitions at longer wavelengths. Accordingly, [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂ shows unusually high luminescence quantum yields for Cu^I complexes, both in solution and in the solid state (0.5 and 7 %, respectively).     

The synthesis of polymers of intrinsic microporosity (PIMs)

Polymers of intrinsic microporosity(PIMs) are a class of porous organic polymer(POP) that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films,coatings or fibres. Here, over twelve years' accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tr鰃er抯 base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue.     

Influence of 1,4‐dioxane solvent inclusion on the crystal structure of 5,5′‐diphenyl‐2,2′‐(p‐phenylene)di‐1,3‐oxazole (POPOP)

Crystallization of 5,5′‐diphenyl‐2,2′‐(p‐phenylene)di‐1,3‐oxazole (POPOP), C₂₄H₁₆N₂O₂, from chloroform or 1,4‐dioxane yielded crystals in pure and solvated forms, respectively. The solvated crystals of POPOP were found to contain 1,4‐dioxane in a strict 1:2 compound–solvent stoichiometry, C₂₄H₁₆N₂O₂·C₄H₈O₂, thus being a defined solvent‐inclusion compound. The crystal system is monoclinic in both cases and the asymmetric unit of the cell contains only half of the molecule (plus one dioxane molecule in the case of the solvated structure), owing to the centrosymmetry of the di‐1,3‐oxazole molecule.     

New and efficient high Stokes shift fluorescent compounds: unsymmetrically substituted 1,2-bis-(5-phenyloxazol-2-yl)benzenes via microwave-assisted nucleophilic substitution of fluorine

Two new unsymmetric derivatives of 1,2-bis-(5-phenyloxazol-2-yl)benzene (ortho-POPOP) were synthesized via microwave-assisted nucleophilic substitution of fluorine which appears to be significantly more efficient compared with conventional thermal activation. The compounds synthesized are characterized by high fluorescence Stokes shifts (6000-11,000 cm⁻¹) in solvents of various polarity, intermediate-to-high fluorescence quantum yields and lifetimes in the range of several nanoseconds.     

Molecular structural features of unsymmetrical ortho analogs of POPOP

The electronic spectra and structures of sterically hindered molecules of unsymmetrical ortho-analogs of POPOP containing electron donor subsitituents in the oxadiazole part of the molecule have been studied (1-(5′-phenyloxazol-2-yl)-2-(5-phenyl-1,3,4-oxadiazol-2-yl)benzene derivatives (I)). X-Ray structural analysis was carried out on the dimethylamino derivative of I. It was found that the conformation of the molecules of the investigated compounds is determined by the conformation of the starting 2-(5-phenyloxazol-2-yl)benzoic acid and its acid chloride used in the synthesis of the ortho POPOP analogs. In the series of unsymmetrical ortho POPOP analogs there arises a unique possibility for changes in the structure of the oxadiazole part of the molecule to affect the position of the spectral emission almost without affecting the long wavelength absorption band in the process. There were thus prepared efficient organic luminophores having an anomalously large Stokes fluorescence shift. Kharkov State University, Kharkov 310077. Institutefor Monocrystals. National Academy of Sciences of Ukraine, Kharkov 310001. Translated from Khimiya Geterotsiklicheskikh Soedinenii. No. 11, pp. 1549–1558, November, 1997.