Synthesis and properties of novel ferroelectric liquid crystalline polyacetylenes containing terphenyl mesogens with chiral groups

Abstract  

Novel ferroelectric liquid crystalline (FLC) polyacetylenes, namely, “side-end-fixed” type of PAM ₆ OTPhOR* and “side-on-fixed” type of PAM ₃ OCO(TPh)OR* were designed and synthesized in high yields (89.3 and 62.0%), respectively, where the terphenyl was linked at the different positions. The thermal stability of PAM ₃ OCO(TPh)OR* is better than PAM ₆ OTPhOR* owing to the “jacket effect” from terphenyl pendant linked at the waist position well protecting the main chain from the perturbations. The PAM ₃ OCO(TPh)OR* shows enantiotropic chiral smectic A phase (SmA*), but it is noteworthy that the PAM ₆ OTPhOR* exhibits enantiotropic chiral smectic C phase (SmC*) responsible for ferroelectric liquid crystallinity. Compared to “side-end-fixed” type of polymer, the “side-on-fixed” type shows better light emitting property, ascribed to the mesogen linked at the waist position has stronger tendency to enhance the main-chain coplanarity. Furthermore, the circular dichroism (CD) spectra demonstrate that the asymmetric force field generated by the chiral center affects the secondary structure of PAM ₃ OCO(TPh)OR*.     

高光谱图像信息的柑橘叶片光合色素含量分析技术研究

暗箱环境下采集柑橘叶片高光谱图像,采用阈值法提取整叶有效光谱信息区域的平均光谱,比对分析了柑橘叶片光谱信息不同预处理方法和光谱PLS、BPNN和LS-SVM预测模型对叶绿素a、叶绿素b和类胡萝卜素等光合色素含量的预测精度。结果显示,采用MSC对原始光谱进行预处理和LS-SVM建模对叶绿素a含量的预测效果较好,Rp达0.898 3,RMSEP为0.140 4;采用SNV光谱预处理和LS-SVM模型对叶绿素b含量的预测其Rp为0.912 3,RMSEP为0.042 6;采用MAS预处理和PLS模型对于类胡萝卜素含量预测的Rp和RMSEP分别为0.712 8和0.062 4。结果表明:采用高光谱图像信息可较好地进行柑橘叶片叶绿素a,叶绿素b和类胡萝卜素等光合色素含量的预测,为进一步研究柑橘叶片光合色素含量与组分构成的非损伤实时检测提供了依据。     

Supercomputing and supercomputers for science and engineering in general and for chemistry and biosciences in particular

We start by pointing out relationships between production of information, global simulation, and supercomputing, thus placing our research activities in today's society context. Then we detail the evolution in hardware and software for 1CAP, our experimental supercomputer, which we claim to be especially well suited for supercomputing in science and engineering. A preliminary discussion of 1CAP/3090 (our latest experimental effort) is included. Many examples from different disciplines are provided to verify our assertions. We “prove” our point by presenting an example of global supercomputing. Starting with 3 nuclei and 10 electrons, building up to a single water molecule, then to a few hundred, we learn, for example, about Raman, infrared, and neutron scattering; we then move up to a few hundred thousand molecules to analyze particle flow and obstructions; finally we experiment, but only preliminarily, with a few million particles to learn more on nonequilibrium dynamics as in the Rayleigh-Benard systems. In this way, quantum mechanics is overlapped with statistical mechanics and expanded into microdynamics. The entire paper is finally reanalyzed from a different perspective, presenting rather systematically, even if most briefly, our ideas on “modern” computational chemistry, where quantum mechanics is as much needed as fluid dynamics and graphics. In this section the main computational techniques are analyzed in terms of computer programs and their associated flow diagrams to solve the basic equations using parallel supercomputers.     

消除原子吸收光谱分析中干扰效应的正交多项式回归设计

应用正交多项式回归设计的方法,对原子吸收光谱分析中的干扰效应进行计算消除的研究。通过实验建立了针对高纯 Eu2O3中钙含量测定时消除干扰的最优回归方程,回归方程精度为 1.32× 10－ 2,对高纯 Eu2O3中钙含量测定,计算结果与实际含量基本一致,相对误差为 1％～ 4％。     

Metal-assisted assembly of pyridine-containing arylene ethynylene strands to enantiopure double helicates

Pyridine-containing arylene ethynylene strands were connected to the 2- and 2'-positions of (R)- and (S)-1,1'-binaphthyl templates. The arylene ethynylene moieties underwent intramolecular coordination with Ag(I) or Cu(I) ion to afford enantiopure double helicates. The double-helical structure was elucidated on the basis of circular dichroic (CD) spectra. The importance of intramolecular complexation of the double strands for the helicate formation was confirmed by comparison with a ligand bearing a single strand. Connection of the strands through an ether linkage enabled a sorting out of the Cotton effect induced by double-helical arylene ethynylene moieties. The CD exciton chirality method unambiguously proved that the termini of the strands approach each other upon complexation and that the sense of the induced helicity is the same as predicted by molecular modeling.     

Lateral flow nucleic acid biosensor for Cu2+ detection in aqueous solution with high sensitivity and selectivity

A lateral flow nucleic acid biosensor based on copper-dependent DNA-cleaving DNAzyme and gold nanoparticles has been developed for the visual detection of copper ions (Cu(2+)) in an aqueous solution with a detection limit of 10 nM.     

Synthesis and Phase Behavior of Poly(1-alkyne) with Liquid Crystalline-induced Luminescence Enhancement

Poly(1-alkyne) with octoxy spacer -{[HC=C(CH2)8O-terphenyl-CN]}n-(PA8CN) and terphenyl liquid crystalline pendant was synthesized,and the effects of structure on the optical properties,especially the liquid crystallinity behavior of the polymer and monomer were investigated.The monomer was prepared in high yields(92.30%) by coupling and etherification reactions and successfully polymerized in the presence of Rh catalyst and Et3N cocatalyst in high yields with trans-rich(86.27%) stereoregular structure.Compared to the monomer showing mixed monolayer structure,its corresponding polymer PA8CN formed homogeneous monolayer arrangement.Upon photoexcitation,strong blue emission peak of PA8CN appeared at 413 nm[fluorescence quantum yield,ΦF = 68% when excited at 330 nm in tetrahydrofuran(THF) solution].Compared with its solid film photoexcitated at 330 nm at room temperature,the UV light-emitting band of PA8CN solid film from its liquid crystalline with liquid nitrogen quenched rapidly at 236 ℃ was red-shift 10 nm with higher intensity,which may be ascribed to the fact that the effectual conjugation and the order degree of the molecule in the liquid crystalline state of the polymer were enhanced,the energy loss caused by the thermal vibration was decreased,thus resulting in the observed hyperchromic effect.     

Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis

The synthesis, reactivity, and potential of well‐defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PN^HP^iPr ( L^H ) ligand, dinuclear Au^I–Au^I complex 1 and mixed‐valent Au^I–Au^III complex 2 provide access to structurally characterized chlorido‐bridged cationic species 3 and 4 upon halide abstraction. For 2 , this transformation involves unprecedented two‐electron oxidation of the redox‐active ligand, generating a highly rigidified environment for the Au₂ core. Facile reaction with phenylacetylene affords the σ,π‐activated phenylacetylide complex 5 . When applied in the dual gold heterocycloaddition of a urea‐functionalized alkyne, well‐defined precatalyst 3 provides high regioselectivities for the anti‐Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear Au^I systems. This proof‐of‐concept demonstrates the benefit of preorganization of two gold centers to enforce selective non‐classical σ,π‐activation with bifunctional substrates.     

Improved Pöschl–Teller potential energy model for diatomic molecules

By employing the dissociation energy and the equilibrium internuclear distance for a diatomic molecule as explicit parameters, we construct an improved Pöschl–Teller potential energy model. We analyze the average absolute deviations of the improved Pöschl–Teller and Morse potentials from the experimental Rydberg–Klein–Rees (RKR) potentials for six diatomic molecules. It is found that the improved Pöschl–Teller potential is more accurate than the Morse potential in fitting experimental RKR potential curves over a large range of internuclear distances for six molecules examined.     

Substrate‐Induced Dimerization Assembly of Chiral Macrocycle Catalysts toward Cooperative Asymmetric Catalysis

An artificial system of substrate‐induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen‐bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich‐like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen‐bonding interaction sites. Inspired by the guest‐induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β‐ketoacid by a cooperative hydrogen‐bonding network enabled by sulfamate‐induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved.