Switching high two-photon efficiency: from 3,8,13-substituted triindole derivatives to their 2,7,12-isomers

Bridging the triindole core and triarylboryl acceptor by an ethenylene linker at the 3,8,13- or 2,7,12-position, the resultant 3-BET and 2-BET show two-photon absorption (TPA) cross sections of δ = 2100 and 2500 GM (at 810 nm by femtosecond pulses in THF), respectively. The TPA enhancement of the 2,7,12-isomers is also found when comparing 3-BYT and 2-BYT (δ = 870 and 1900 GM) and 3-NET and 2-NET (36 and 400 GM).     

芸香草精油化学成分的研究

芸香草(Cymbopogon distans(Nees)W.wats)系多年生禾本科香茅属植物,分布于我国甘肃、陕西和西南及印度等地~[1].芸香草含芳香油,可提制香精油,是香料及化妆品工业的重要原料,芸香草还可入药,有较大的开发价值.Melkani等~[2]曾指出,不同地区生长的芸香草精     

Strain Tunable Berry Curvature Dipole,Orbital Magnetization and Nonlinear Hall Effect in WSe_2 Monolayer

The electronic topology is generally related to the Berry curvature,which can induce the anomalous Hall effect in time-reversal symmetry breaking systems.Intrinsic monolayer transition metal dichalcogenides possesses two nonequivalent K and K’ valleys,having Berry curvatures with opposite signs,and thus vanishing anomalous Hall effect in this system.Here we report the experimental realization of asymmetrical distribution of Berry curvature in a single valley in monolayer WSe₂ via applying uniaxial strain to break C_3v symmetry.As a result,although the Berry curvature itself is still opposite in K and K’ valleys,the two valleys would contribute equally to nonzero Berry curvature dipole.Upon applying electric field E,the emergent Berry curvature dipole D would lead to an out-of-plane orbital magnetization M ∝ D·E,which further induces an anomalous Hall effect with a linear response to E²,known as nonlinear Hall effect.We show the strain modulated transport properties of nonlinear Hall effect in monolayer WSe₂ with moderate hole-doping by gating.The second-harmonic Hall signals show quadratic dependence on electric field,and the corresponding orbital magnetization per current density M/J can reach as large as 60.In contrast to the conventional Rashba-Edelstein effect with in-plane spin polarization,such current-induced orbital magnetization is along the out-of-plane direction,thus promising for high-efficient electrical switching of perpendicular magnetization.     

约化密度矩阵中的N表示问题

利用准自旋-辛群对称性基函数及Kummer提出的构造暴露算子法研究了量子化学中密度矩阵N表示理论的端点问题,找出了更多的二阶约化密度矩阵凸集的端点.     

Acceptor or donor (diaryl B or N) substituted octupolar truxene: synthesis, structure, and charge-transfer-enhanced fluorescence

Two diaryl B- and N-substituted truxene charge-transfer compounds B3 and N3 have been synthesized. The fluorescence intensities of several nonfunctionalized truxene compounds are 1 order of magnitude weaker than that of B3 and N3. To reveal the structure-property correlations, the X-ray structures of B3 and N3 and their precursors 3 and 4 have been determined. The extended molecular dimension, the especially shortened B-C bond, and the improved planarity of B3 can serve as direct structural evidence for the charge transfer.     

四种荧光素酯的化学物理性质

在紫外线的照射下,荧光素酯能与生物体细胞作用发出鲜艳的黄绿色荧光,由于生物体细胞的生活力不同,细胞内水解酶的含量也不同,因而显出的荧光强度不同。借此性质可以测定细胞内荧光素水解酶的活性以及细胞的生活状态。由于它们是一类选择性好,灵敏度较高的生物荧光染色剂,所以深入研究四种荧光素酯的化学物理性质是有意义的。四种荧光素酯的分子结构可用下面通式表示。     

Chemometrics to chemical modeling: novel molecular distance-edge vector (λ) in alkanes and retention index of gas chromatography

Systematic studies are made on application of chemometrics to chemical modeling and/or molecular modeling as well as the regularity of retention index for gas chromatography (GC). A set of novel molecular graph theoretical parameters, called the molecular distance-edge (MDE) vector (λ), is proposed and found to be excellently correlated to retention index of GC for alkanes. The MDE parameters were tested by the multiple linear regression (MLR) estimation and prediction of the retention index of GC, and the results obtained are satisfactory.     

Donor-and-acceptor substituted truxenes as multifunctional fluorescent probes

A series of dimesitylboryl acceptor (mesityl=2,4,6-trimethylphenyl) and/or diphenylamino donor (-N(Ph)2)-substituted truxene derivatives, classified as D-or-A substituted compounds and D-and-A substituted charge-transfer compounds, have been synthesized. Two D-and-A substituted truxene compounds, namely, 2-dimesitylboryl-7,12-di(N,N-diphenylamino)-5,5',10,10',15,15'-hexaethyltruxene (BN2) and 2,7-di(dimesitylboryl)-12-(N,N-diphenylamino)-5,5',10,10',15,15'-hexaethyltruxene (B2N), exhibit extraordinarily large solvatochromism ranging from 420 nm (in hexane) to 580 nm (in acetonitrile) in aprotic solvents, which can be used to probe the polarity of the solution environment. Due to proton-donor interactions, the solvatochromic red shift of BN2 and B2N in protic solvents has been significantly decreased, and this effect can be used to identify local protic and aprotic environment. Furthermore, because of the interaction between F- and acceptor, BN2 and B2N show sharp spectral response to fluoride ion concentration. The simultaneous "turn-off" at 500 nm and "turn-on" at 380 nm of the fluorescence signal have provided a good example of a fluorescent ratiometric method, which can greatly enhance the sensitivity of the fluoride ion probe. Underlying these interesting spectral phenomena and multifunctional probe properties is the charge-transfer strategy of grafting donor and acceptor moieties, as A-pi-D2 or A2-pi-D style, to the triangular truxene.