Structural and orientational studies of chiral N-[4(1-pyrene)butyroyl]-phenylalanine in cast film

Cast films of chiral material N-[4(1-pyrene)butyroyl]-l-phenylalanine (Py-l-Phe) and the racemic modification (the 1:1 mixture of Py-l-Phe and Py-d-Phe) have been investigated in the present study. The microscopic structure, molecular orientation and the aggregation in the film have been studied by using ultraviolet-visible (UV-vis) and infrared (IR) spectroscopy. When a cast film is formed from the chloroform solution at room temperature, the J-aggregates of Py-l-Phe and Py-d-Phe are observed by UV-vis spectra. A comparison of Fourier transform infrared (FT-IR) transmission and reflection-absorption (RA) spectroscopy has been applied to reveal the orientation and structural characterization of the cast films. It has been found that the pyrenyl ring in the cast film of Py-l-Phe assumes a nearly vertical orientation with respect to the surface of the solid substrate. And there are two different hydrogen bonding species, cyclic dimer and linear dimer, exist in carboxyl groups in cast films. The detailed analysis of the OH and NH stretching modes of Py-l-Phe and Py-d-Phe allows us to reveal the hydrogen bonds existing in the films.     

Coacervation of copolymer of diallyldimethylammonium chloride and sodium styrenesulfonate aqueous solution

Coacervate behavior of polyelectrolyte complexes has been studied by many papers. Few studies have focused on the coacervate behavior of amphoteric polymer. In this study, amphoteric copolymer of diallyldimethylammonium chloride (DM) and sodium styrenesulfonate (SS) (the copolymer was noted as DMS) was synthesized with the mole content of SS to DM ranged from 0 to 10%. Firstly, DMS was characterized by static light scattering, FTIR, ¹H-NMR, TGA and DSC. Then, its phase and coacervate behaviors were studied. Turbidity was utilized as an indicator for the coacervate formation. It was found that when the SS content was more than 4 mol%, DMS coacervate would be formed in deionized water at a certain concentration. Temperature and pH have no effect on the formation of DMS coacervate. Meanwhile, salts has a great influence on the DMS coacervation. Unlike the results of the other polyelectrolyte complexes, Na₂SO₄, Na₂HPO₄, NaCOOCH₃, sodium citrate and NaI cannot prevent the DMS coacervate formation. However, the addition of NaCl, NaNO₃, NaBr and NaSCN can prevent the coacervate formation. The influence cannot be described by Hofmeister-like behavior. Results of surface tension and fluorescence spectrum presented that the driving forces to formation of DMS coacervate are the electrostatic interaction and the intermolecular hydrophobic interaction.     

A theoretical prediction about harnessing ESPT process for HBO derivatives

The different excited-state behaviors involved in excited-state proton transfer (ESPT) process of a series of 2-(2-hydroxyphenyl)benzoxazole (HBO) derivatives have been theoretically investigated. The primary bond lengths and bond angles were analyzed. Coupling with the infrared (IR) vibrational spectra, we confirmed that the intramolecular hydrogen bond O–H···N should be strengthened in the S₁ state, which might provide the possibility for ESPT reaction, whereas introducing the fused rings may weaken the hydrogen bond in excited state. By investigating the vertical excitation process, the charge redistribution was explored. It is found that the electron-accepting –NO₂ and –COOH would facilitate the ESPT reaction. With adding fused rings to HBO, less charge transfer exists in the transition process, which can reasonably explain the weakening hydrogen bond phenomenon in excited states. Via constructing the potential energy curves of both S₀ and S₁ states, we further confirm that electron-accepting substitutions could promote the ESPT process for HBO systems. And fused rings do inhibit ESPT reaction to a great extent. We believe this work not only elaborates the different excited-state proton transfer behaviors for a series of HBO derivatives but also presents a new harnessing ESPT process through substitutional effects.     

Synthesis and red electroluminescence of a dimesityl-functionalized bistetracene

The single crystal analysis of the as-prepared 8,16-dimesityltetraceno[2,1,12,11-opqra]tetracene (DMTA) suggests that the parent bistetracene backbone is almost in a plane without any intermolecular p-stacking interaction. The fabricated devices based on DMTA as an emitter exhibit a maximum brightness of 632 cd/m² at 14.7 V with the CIE coordinate of (0.623, 0.349).     

Potassium Amide‐Catalyzed Benzylic C−H Bond Addition of Alkylpyridines to Styrenes

The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide‐catalyzed selective benzylic C?H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Brønsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity.     

不对称氢化杂环亚胺合成四氢吡咯/吲哚[1,2-a]并吡嗪

报道了一种铱催化3,4-二氢吡咯并吡嗪和3,4-二氢吲哚[1,2-a]并吡嗪的不对称氢化合成相应的1,2,3,4,-四氢吡咯/吲哚[1,2-a]并吡嗪化合物的方法.该催化体系适用于芳基取代的底物和烷基取代的底物,反应收率高达99%,对映选择性过量值最高为95%.该反应操作简单,原子经济性好.     

Infrared photodissociation spectroscopy of electrosprayed ions in a Fourier transform mass spectrometer

Previous gas-phase methods for infrared photodissociation spectroscopy (IRPD) require sample volatility. Our method instead uses electrospray ionization to introduce even large nonvolatile molecules into a Fourier transform mass spectrometer, where extended (>15 s) ion storage makes possible high sensitivity spectral measurements with an OPO laser over a range of 3050-3800 cm(-1). The spectra of 22 gaseous proton-bound amino acid complexes are generally correlated with the H-stretching frequencies established for O-H and N-H functional groups in solution. For theoretical structure predictions of the Gly2H+ and N-acylated Asp2H+ dimers, IRPD spectra clearly differentiate between the predicted lowest energy conformers. In contrast to solution, in the gas phase the glycine zwitterion is approximately 20 kcal/mol less stable than the neutral; however, glycine is clearly zwitterionic in the gaseous GlyLysH+ dimer. The level of theory is inadequate for the larger Lys2H+ dimer, as all low energy predicted structures have free carboxyl O-H groups, in contrast to the IR spectrum. IRPD appears to be a promising new technique for providing unique information on a broad range of biomolecular and other gaseous ions, especially on noncovalent bonding involving O-H and N-H groups.     

NO和O2在Pt(110)面上吸附的TDS和PEEM研究

采用热脱附和光电子发射普微镜研究了Ｏ２和ＮＯ在Ｐｔ（１１０）面上的吸附和共吸附。结果表明，室温条件下，ＮＯ在Ｐｔ（１１０）面上有端式和桥式两种不同的吸附方式。Ｐｔ（１１０）表面预吸附的原子态氧占据了ＮＯ进入了桥式吸附的活性粒，从而阻遏了ＮＯ在Ｐｔ表面发生解离反应必须经过的桥式吸附中间态的形式，进而降低了ＮＯ在Ｐｔ表面直接分散的能力。