Supramolecular Copolymerization by Sequence Reorganization of a Supramolecular Homopolymer

The homopolymeric sequence formed by the head‐to‐head association of tetrakisporphyrin 1 is completely dissociated by the competitive association of the ditopic guest G2 , resulting in the supramolecular copolymer poly‐ 1 ? G2 with an alternatingly repeating host–guest sequence. The 1:1 stoichiometry of 1 and G2 is confirmed by a Job plot using UV/Vis titration and diffusion‐ordered NMR spectroscopy (DOSY). The solution viscometry for poly‐ 1 and poly‐ 1 ? G2 suggests that the supramolecular chain of poly‐ 1 behaves like a rod, whereas the supramolecular copolymer chain of poly‐ 1 ? G2 behaves like a swelled fat chain, which is entangled in the semi‐dilute regime. Atomic force microscopy shows that the supramolecular polymer poly‐ 1 ? G2 is highly oriented through the interdigitation of the long alkyl chains.     

PhSeSiR(3)-Catalyzed Group Transfer Radical Reactions

A novel design for initiating radical-based chemistry in a catalytic fashion is described. The design of the concept is based on the phenylselenyl group transfer reaction from alkyl phenyl selenides by utilizing PhSeSiR(3) (1) as a catalytic reagent. The reaction is initiated by the homolytic cleavage of -C-Se- bond of an alkyl phenyl selenide by the in situ generated alkylsilyl radical (R(3)Si(*)), obtained by the mesolysis of PhSeSiR(3)](*)(-)( )()(1(*)(-)). The oxidative dimerization of counteranion PhSe(-) to PhSeSePh functions as radical terminator. The generation of 1(*)(-) is achieved by the photoinduced electron transfer (PET) promoted reductive activation of 1 through a photosystem comprising of a visible-light (410 nm)-absorbing electron rich DMA as an electron donor and ascorbic acid as a co-oxidant (Figure 1). The optimum mole ratio between the catalyst 1 and alkyl phenyl selenides for successful reaction is established to be 1:10. The generality of the concept is demonstrated by carrying out variety of radical reactions such as cyclization (10, 15-18), intermolecular addition (25), and tandem annulations (32).     

PD-1与单克隆抗体残基特异性结合机制的计算丙氨酸扫描研究

通过分子动力学模拟检测了2种程序性细胞死亡蛋白（PD-1）/单克隆抗体(Pembrolizumab和Nivolumab)复合物, 并使用高效的计算丙氨酸扫描方法预测了单抗与PD-1的结合热点, 将它们与对PD-1/PD-L1结合重要的热点残基进行对比分析. 结果显示, Pembrolizumab以类似于PD-L1的方式与PD-1结合, 而Nivolumab则以不同的方式与PD-1结合. 2个PD-1/mAb复合物中共有的热点只有_PD-1K131. 同时发现, 与_PD-1K131结合的单抗的关键残基通常都受范德华(vdW)能量控制. 2种单克隆抗体上热点的自由能贡献都以vdW能量为主, 这表明在下一代PD-1新抗体的设计中需要提高静电型热点残基的数量.     

Transformation of Phosphaalkynes into 1H- and 2H-Phosphirenes1

Abstract

The 2H-phosphirene 4 is synthesized from the spirocyclic 3H-1,2,4-diazaphosphole 1 by low temperature photolysis. The isomeric 1H-phosphirenes 7 are formed by a [2+1]-cycloaddition process of chlorocarbenes, generated from diazirines. onto the triple bond of phosphaalkynes. When the 1-chlon-1H-phosphirenes 7 are allowed to react with a series of nucleophiles substitution occurs yielding the 1H-phosphirenes 9, 11 and 12. The existance of a phosphirenium cations, for instance 13 is discussed.     

Pathway for the stereocontrolled Z and E production of alpha,alpha-difluorine-substituted phenyl butenoates

An efficient preparation of pure ethyl Z- and E-alpha,alpha-difluoro-4-phenyl-3-butenoate 1a and 1b together with the corresponding acids 2a and 2b is described. The procedures involve stereocontrolled additions of *CF2CO2Et to phenylacetylene or beta-bromostyrene. Compound 1a is easily obtained by addition of *CF2CO2Et to phenylacetylene via a mechanism where the stereochemistry is controlled by an electron-transfer process to produce predominantly the Z vinyl anion. The product 1b is obtained by *CF2CO2Et addition-elimination to Z- or E-beta-bromostyrenes via a mechanism where the stereochemistry is controlled by steric factors in the conformational equilibration of the intermediates.     

Generation and reactivity of the phenyl cation in cryogenic argon matrices: monitoring the reactions with nitrogen and carbon monoxide directly by IR spectroscopy

The phenyl cation 1 has been prepared by co-deposition of iodobenzene 6 or bromobenzene 7 with a microwave-induced argon plasma and characterized by IR spectroscopy in cryogenic argon matrices. The cation can clearly be identified by its strongest absorption at 3110 cm(-1) that is rapidly bleached upon visible light irradiation. This characteristic band is observed neither in the conventional photochemistry of 6 or 7 nor in discharge experiments with alkyl halides or chlorobenzene. The latter finding is in line with energetic considerations. According to density functional theory (DFT) computations, the strongest absorption of 1 is caused by a C-H stretching vibration that involves almost entirely the ortho-hydrogens. This is confirmed by isotopic labeling experiments. Co-deposition of halobenzene/N2 mixtures leads to a decrease of the 3110 cm(-1) absorption, whereas several new signals are detected in the 2200-2400 cm(-1) range of the IR spectrum. Annealing of a matrix that contains 1 and 1% N2 leads to an increase of a broad band at 2260 cm(-1) that is assigned to the benzenediazonium ion 2. A sharp signal at 2327 cm(-1) that had previously been assigned to the N-N stretching vibration of 2 is due to molecular nitrogen. The mechanism that triggers the IR activity of N2 is not yet understood. Annealing of a matrix that contains 1 and 0.5% CO leads to an increase of a broad band at 2217 cm(-1) that is considerably stronger than the 2260 cm(-1) absorption of 2. This signal is assigned to the C-O stretching vibration of the benzoyl cation 12, in excellent agreement with previous investigations of 12 in superacidic media. Some consequences of the measured frequencies with regard to bonding in 2 and 12 are discussed.     

Isomers of cyclo-heptasulfur and their coordination to Li(+): an ab initio molecular orbital study

The potential energy hypersurfaces (PESs) of heptasulfur (S7) and of [LiS7]+ have been investigated by ab initio molecular orbital calculations at the G3X(MP2) level of theory. Besides the chair-like seven-membered ring (1a) as the global minimum structure, eight local minimum structures and one transition state have been located on the PES of S7. The barrier for pseudorotation of 1a is only 5.6 kJ mol(-1). The boat-like S7 ring (1b) is 12.1 kJ mol(-1) less stable than 1a, followed by three isomers of connectivity S6=S and four open-chain isomers. On the basis of multireference calculations at the MRCI(4,4)+Q/6-311G(d) level, the most stable open-chain form of S7 is a triplet of relative energy 133.1 kJ mol(-1). Thus, the reaction energy (deltaE0) for the ring opening of 1a is 133.1 kJ mol(-1), halfway between those of the highly symmetrical rings S6 and S8. Because of their strong multireference characters, the stabilities of the biradicalic singlet chains are significantly overestimated by the single-reference-based G3X(MP2) method. The calculated vibrational spectrum of 1a is in good agreement with experimental data. The various isomers of S7 form stable complexes with Li+ with coordination numbers of 1-4 for the metal atom and binding energies in the range of -93.8 to -165.7 kJ mol(-1). A total of 15 isomeric complexes have been located, with 13 of them containing cyclic ligands. The global minimum structure (2a) is composed of 1a, with the Li+ cation linked to the four negatively charged sulfur atoms (symmetry C(s)). The corresponding complex 2c containing the ligand 1b is by 23.4 kJ mol(-1) less stable than 2a, and a bicyclic crown-shaped LiS7 cation (2e) is by 34.9 kJ mol(-1) less stable than 2a. Even less stable are four complexes with the branched S6=S ligand. SS bond activation by polarization of the valence electrons takes place on coordination of Li+ to cyclo-S7 (1a).     

Dielectric relaxation studies of 1-hexanol and 1,2-hexanediol in heptane

Solutions of 1-hexanol and 1,2-hexanediol in heptane have been investigated tigated by means of dielectric time domain spectroscopy (TDS). The permittivity spectrum of 1-hexanol in heptane is characterized by a model function containing a sum of three elementary Debye dispersions, while 1,2-hexanediol in heptane is best described by a Cole-Davidson model function. It is shown that dilute solutions of 1-hexanol in heptane have a completely different behavior to that of 1,2-hexanediol. For the diol, the relaxation time levels off at a high value indicating an existence of higher hydrogen bonded complexes. It is possible to quantify the relative amount of monomeric 1-alcohol molecules from the dielectric spectrum. The monomerization rate for 1-hexanol upon dilution with heptane is initially low, but increases rapidly for mole fractions of heptane exceeding 0.4.     

稀土胺羧酸配合物的研究 I. {[MnGd(DTPA)(H2O)5]2·H2O}n配合物的合成和晶体结构

本文首次合成了{MnLn(DTPA)(H2O)5]·H2O}n异核链式配合物(Ln=Gd, Er, Y)单晶,测定了{[MnGd(DTPA)(H2O)5]2·H2O]n的单晶结构。     

Type I and type II photosensitization by the antibacterial drug nalidixic acid. A laser flash photolysis study.

The 355 nm laser flash photolysis of nalidixic acid at pH 9.2 leads to the formation of the nalidixate anion triplet state (absorption lambda max = 620 nm; 5700 less than or equal to epsilon T less than or equal to 9000 M-1cm-1; 0.6 less than or equal to phi T less than or equal to 1). The first order triplet state decay (kT = 7.7 x 10(3) s-1) is accompanied by a diffusion controlled triplet-triplet annihilation. Oxygen efficiently quenches the triplet state (k = 3.2 x 10(9) M-1s-1). The nalidixate radical dianion (absorption lambda max = 650 nm; epsilon = 3000 M-1cm-1) is produced by the diffusion controlled reductive quenching of the triplet state by tryptophan and tyrosine. The superoxide anion (O2-.) is produced by diffusion controlled reaction of the radical dianion with oxygen. The O2-. is characterized by its reactions with ferricytochrome c and superoxide dismutase. The physiological form of nalidixic acid is thus a good Type I and Type II photosensitizer.     

Sulfur Versus Oxygen in Interaction with the Double Bond: AB Initio Study of Electronic Structure and Prototropic Rearrangement of 1-Methoxy-2-propene and 1-Methylthio-2-propene

The ab initio calculations of 1-methoxy-2-propene ( 1 ), 1-methylthio-2-propene ( 2 ), and their anions are performed using the RHF/6-31+G* geometry optimization followed by MP2/6-31+G* energy calculations. Both 1 and 2 are found to rearrange toward 1-substituted 1-propenes with a comparable exothermic effect. However, the proton abstraction energies of 1 and 2 differ significantly. So, the acidity of propene is just slightly affected by the OCH 3 group while the SCH 3 group decreases its proton abstraction energy by 17.5 kcal/mol. Changes in charge distribution, bond lengths and bond orders suggest the negative hyperconjugation to stabilize anions of 2 but not that of 1 . This divergence is explained with a difference in sulfur and oxygen electronegativity. The d -functions of both sulfur and oxygen act in polarization. The Z -isomer of anion 1 is found to be by 2.9 kcal/mol more stable than its E -isomer, this could provide a predominant kinetic formation of the less stable Z -isomer of 1-methoxy-1-propene under base catalysis.     

High-performance liquid chromatography of sulphadimethoxine and its N1-glucuronide, N4-acetyl and N4-acetyl-N1-glucuronide metabolites in human plasma and urine

Sulphadimethoxine is metabolized in humans by N1-glucuronidation and by N4-acetylation. Sulphadimethoxine-N1-glucuronide can be measured by the direct high-performance liquid chromatographic analysis and without enzymic deglucuronidation. The N1-glucuronide can be measured by an isocratic as well as by a gradient mobile phase. The group contribution of the N1-glucuronide moiety to the capacity factor is a reduction of 0.24 in the isocratic system and 0.55 in the gradient system. N4-Acetylation increases the capacity factor by a factor 1.4 in the isocratic system and by 1.06 in the gradient system.     

Kinetics of the oxygenation of unsaturated organics with singlet oxygen generated from H2O2 by a heterogeneous molybdenum catalyst

A heterogeneous catalyst containing MoO42- exchanged on layered double hydroxides (Mo-LDHs) is used to produce 1O2 from H2O2, and with this dark 1O2, unsaturated hydrocarbons are oxidized in allylic peroxides. The oxidation kinetics are studied in detail and are compared with the kinetics of oxidation by 1O2, formed from H2O2 by a homogeneous catalyst. A model is proposed for the heterogeneously catalyzed 1O2 generation and peroxide formation. The model divides the reaction suspension in two compartments: (1) the intralamellar and intragranular zones of the LDH catalyst; (2) the bulk solution. The 2-compartment model correctly predicts the oxidant efficiency and peroxide yield for a series of olefin peroxidation reactions. 1O2 is generated at a high rate by the heterogeneous catalyst, but somewhat more 1O2 is lost by quenching with the heterogeneous catalyst than using the homogeneous catalyst. Quenching occurs mainly as a result of collision with the LDH hydroxyl surface, as is evidenced by using LDH supports containing strong 1O2 deactivators such as Ni2+. A total of 15 organic substrates were peroxidized on a preparative scale using the best Mo-LDH catalyst under optimal conditions.     

Stabilisierung eines Phospholanium-methylids durch Silyl- und Phenylsubstituenten

Stabilization of a Phospholanium-methylide by Silyl and Phenyl Substituents The ylide 1-methyl-1-methylene-1λ⁵-phospholane is a thermolabile compound and undergoes spontaneous dimerization. Introduction of one or two trimethylsilyl groups at the ylidic function reduces the nucleophilicity of the carbanion and no dimerization occurs. Through desilylation using alcohol, the silyl-free phospholane ylide is regenerated. Phenyl substitution as in 1-benzylidene-1-methyl-1λ⁵-phospholane has a similar effect. The compound is isolated as a stable ylide. The compounds were characterized by analytical and spectroscopic data.     

Determination of 1-nitropyrene by thin-layer chromatography in a diesel exhaust particulate extract

A method is described for the determination of 1-nitropyrene in a diesel exhaust particulate extract by thin-layer chromatography. 1-Nitropyrene is determined as 1-aminopyrene after prechromatographic reduction and isolation by solvent partition. The fluorescence response of 1-aminopyrene is approximately 1000-fold greater than that of 1-nitropyrene. The poor fluorescence stability of 1-aminopyrene on silica gel plates prevents in situ detection by scanning densitometry unless the plates are impregnated with a mixture of 2,6-di-tert-butyl-4-methylphenol and Fomblin H-Vac. A linear response from 1 to 150 ng of 1-aminopyrene and a detection limit of 1.0 ng were obtained using the impregnated plates. For fourteen samples of a diesel exhaust particulate extract the concentration of 1-nitropyrene was determined to be 165 μg/g with an RSD = 9.0%. No significant interferences were observed from other nitro- or aminopolycyclic aromatic compounds present in the extract.     

pK(a)-directed host-guest assemblies: rational analysis of molecular adducts of 2,4-diamino-6-methyl-1,3,5-triazine with various aliphatic dicarboxylic acids

Molecular adducts of 2,4-diamino-6-methyl-1,3,5-triazine (1) have been prepared with various aliphatic dicarboxylic acids. The molecular complexes (1 a-1 i) thus formed by co-crystallizing 1 with oxalic, malonic, succinic, fumaric, acetylene dicarboxylic, glutaric, thiodiglycolic, diglycolic, and adipic acids have been found to give two types of host-guest assemblies that have voids or channels in a three-dimensional arrangement. The different types of host-guest arrangement appear to result from differences in the acidity of the dicarboxylic acids, that is, acids with pK(a)<3.0 give host networks that consist of 1 and the corresponding acid with water or solvent molecules of crystallization present as guests, whereas acids with pK(a)>3.0 exist as guests in voids in a host network formed by 1. The former arrangement is observed in adducts 1 a, 1 b, 1 e, and 1 h and the latter arrangement is found in adducts 1 c, 1 d, 1 f, 1 g, and 1 i.     

Time-resolved electron spin resonance of gallium and germanium porphyrins in the excited triplet state

Gallium and germanium porphyrin complexes in the lowest excited triplet (T1) state have been studied by time-resolved electron spin resonance (TRESR). It is found that for Ge(TPP)(OH)2 (TPP = dianion of tetraphenylporphyrin) intersystem crossing (ISC) from the lowest excited singlet (S1) state to the T1x and T1y sublevels is faster than that to the T1z sublevel (T1x, T1y, and T1z are sublevels of the T1 state), while the ISC of ZnTPP and Ga(TPP)(OH) is selective to the T1z sublevel. This is interpreted by a weak interaction between the dpi orbital of germanium and LUMO (eg) of the porphyrin ligand, resulting in small spin-orbit coupling (SOC). The interpretation is supported by molecular orbital calculations. The ISC of Ge(OEP)(OH)2 (OEP = dianion of octaethylporphyrin) and Ge(Pc)(OH)2 (Pc = dianion of tetra-tert-butylphthalocyanine) is found to be selective to the T1z sublevel in contrast to Ge(TPP)(OH)2. This dependence on the porphyrin ligand is reasonably explained by a difference between the 3(a(1u)eg) (the OEP and Pc complexes) and 3(a(2u)eg) (the TPP complex) configurations. This is the first observation of a difference in selective ISC between the 3(a(1u)eg) and 3(a(2u)eg) configurations. The TRESR spectrum of Ge(TPP)Br2 is different from those of Ge(TPP)Cl2 and Ge(TPP)(OH)2, and is interpreted by SOC between the T1 and T2 states. From ESR parameters the square of the coefficient of the eg orbital on bromine is evaluated as 0.018 in the T1 state.     

CRYSTAL AND MOLECULAR STRUCTURE OF 3a-(4-CHLORO-PHENYL)-1, 5-DIPHENYL-3a, 4,5,11-TETRAHYDRO-1, 2, 4-OXA-DIAZOLINO [5,4-d][1, 5]BENZOTHIAZEPINE, (C_(28)H_(21)N_2OClS)

<正> The structure of 3a-(4-chlorophenyl)-1, 5-diphenyl-3a, 4,5,11-te-trahydrq-1, 2, 4-oxadiazolino [5, 4-d][1, 5] benzothiazepine (C28H21N2OClS) has been determined. The compound crystallizes in triclinic space group P1 with two formula units in a cell of dimensions: a =11. 114(2), b = 11. 673(1), c=10. 435(1) (?), α=98. 42(1), β=118. 69(1),γ = 98. 64(1)° and V = 1136. 2(3)(?)3. The structure was solved by using direct methods and refined by full matrix least-squares. The final crystallographic discrepancy factor is 0. 058 for 2384 observed reflections. The molecular backbone is a tricyclic system : The seven-membered hetero ring in the center is in twisted-boat conformation, and is cis-fused to 1, 2, 4-oxadiazolino ring which is in an envelope form, together with the equilaterally adjoined benzene ring . The compound has a non-planar conjugation system.     

Chemo- and periselectivity in the addition of [OsO2(CH2)2] to ethylene: a theoretical study

Quantum chemical calculations by using density functional theory at the B3LYP level have been carried out to elucidate the reaction course for the addition of ethylene to [OsO2(CH2)2] (1). The calculations predict that the kinetically most favorable reaction proceeds with an activation barrier of 8.1 kcal mol(-1) via [3+2] addition across the O=Os=CH2 moiety. This reaction is -42.4 kcal mol(-1) exothermic. Alternatively, the [3+2] addition to the H2C=Os=CH2 fragment of 1 leads to the most stable addition product 4 (-72.7 kcal mol(-1)), yet this process has a higher activation barrier (13.0 kcal mol(-1)). The [3+2] addition to the O=Os=O fragment yielding 2 is kinetically (27.5 kcal mol(-1)) and thermodynamically (-7.0 kcal mol(-1)) the least favorable [3+2] reaction. The formal [2+2] addition to the Os=O and Os=CH2 double bonds proceeds by initial rearrangement of 1 to the metallaoxirane 1 a. The rearrangement 1-->1 a and the following [2+2] additions have significantly higher activation barriers (>30 kcal mol(-1)) than the [3+2] reactions. Another isomer of 1 is the dioxoosmacyclopropane 1 b, which is 56.2 kcal mol(-1) lower in energy than 1. The activation barrier for the 1-->1 b isomerization is 15.7 kcal mol(-1). The calculations predict that there are no energetically favorable addition reactions of ethylene with 1 b. The isomeric form 1 c containing a peroxo group is too high in energy to be relevant for the reaction course. The accuracy of the B3LYP results is corroborated by high level post-HF CCSD(T) calculations for a subset of species.     

Inbred testing of tomato (Lycopersicon esculentum L.) F1 varieties by ultrathin-layer isoelectric focusing of seed protein

To test seed lots of tomato F1 hybrid varieties for the presence of undesirable inbred seeds by electrophoresis, a method has been developed on the basis of ultrathin-layer isoelectric focusing. The method is based on the genetic variation of the seed protein PRS-1 which could be visualized by isoelectric focusing of a 5 mM NaCl-soluble seed protein extract in a pH 6-9 gel followed by protein staining. Two genetic variants of the PRS-1 protein, PRS-1+ and PRS-1(1), were found among open-pollinated varieties, as well as among F1 hybrid varieties. The isoelectric points (pI) of the PRS-1 proteins are 7.1 and 6.1 for PRS-1+ and PRS-1(1), respectively. The PRS-1 protein is unique to seed tissue and is located primarily in the embryo. A genetic 1:2:1 segregation of the gene Prs-1 among several F2 populations shows monogenic inheritance. Analysis of commercial F1 hybrid varieties from several seed companies indicated that the Prs-1(1) allele, in contrast to the Prs-1+ allele, is primarily present in gene pools of "Money-maker type" tomatoes. The described method is generally applicable to all tomato F1 varieties that are heterozygous for the gene Prs-1. With the described method one person can routinely analyze more than 768 seeds per day.