Strong optical nonlinearities of self-assembled polymorphic microstructures of phenylethynyl functionalized fluorenones

The polymorphs of a phenylethynyl functionalized fluorenone derivative, and their controlled self-assembly for microstructures with different morphologies have been studied. These polymorphic microcrystals exhibit very distinctive NLO properties, which are highly correlated to their electronic and supramolecular structures.     

Fast Exfoliation and Functionalisation of Two‐Dimensional Crystalline Carbon Nitride by Framework Charging

Two‐dimensional (2D) layered graphitic carbon nitride (gCN) nanosheets offer intriguing electronic and chemical properties. However, the exfoliation and functionalisation of gCN for specific applications remain challenging. We report a scalable one‐pot reductive method to produce solutions of single‐ and few‐layer 2D gCN nanosheets with excellent stability in a high mass yield (35 %) from polytriazine imide. High‐resolution imaging confirmed the intact crystalline structure and identified an AB stacking for gCN layers. The charge allows deliberate organic functionalisation of dissolved gCN, providing a general route to adjust their properties.     

X-ray structure of 14-phenyldiquino[3,4 b;4′,3′-e][1,4]thiazine<Superscript>(1)</Superscript>

The title compound 1 (C₂₄H₁₅N₃S) crystallizes in an orthorhombic unit cell, with a = 8.2355(3), b = 19.1499(8), and c = 11.3520(5) Å, Z = 2, and space group Pnma. The pentacyclic ring system is folded mainly along the S–N(2) axis and slightly along the C(3)–C(4) and C(3′)–C(4′) axes. The butterfly folding angle between the two quinoline planes is 48.96(3)^∘ and the angle between the planes of the two halves of the thiazine ring is 43.46(7)^∘. The central thiazine ring is in a boat conformation. The phenyl substituent is unexpectedly in an axial location with respect to the thiazine ring with the C–N⋅ < eqid1 > ⋅S angle of 114.0(1)^∘ and it is perpendicular to the bisecting plane of the pentacyclic ring system.     

Crystal and molecular structure of sodium picrate monohydrate

Na⁺ [C₆H₂(NO₂)₃O]^– H₂O,M _r=269.11, monoclinic,C2/m (No. 12),a=13.065(1),b=20.065(2),c=3.6957(4) Å,=90.75(1)°,V=968.7(1) ų,Z=4,D _m=1.848 g cm^–3 (by flotation),D _x=1.845 g cm^–3, (CuK)=1.54184 Å,(CuK)=17.5 cm^–1,F(000)=540,T=295 K,R=0.055,wR=0.060 for 879 observed reflections withI2.5(I). p]In the structure the picrate anion has exact twofold symmetry, the water molecule has exact mirror symmetry and the two sodium cations occupy special positions on inversion centers at (0, 1/2, 0) and (1/2, 1/2, 1/2). The phenyl ring together with the four substituent N and O atoms is strictly planar, but the phenyl ring is severely distorted from hexagonal symmetry, as is commonly observed in structures containing the picrate fragment. Both sodium ions are eight-coordinated with Na(1) and Na(2) in a cubic and distorted cubic arrangement, respectively. Na(1) coordinates to four charged phenoxide O atoms and four O atoms of nitro groups, and Na(2) to four O atoms of nitro groups and four water molecules. The water molecule donates two hydrogen bonds to symmetry-related O(2) atoms ofortho nitro groups. Two symmetry-related O(3) atoms ofortho nitro groups serve as acceptors in a very unusual asymmetric bifurcated C-HO hydrogen bond.     

Wild nearfields of dimension 2 over rational function fields

Let F be a field. We construct many subgroups of \({{\rm GL}_2(F(t))}\) that act regularly on \({F(t)^2{\setminus}\{0\}}\), and we show that the corresponding nearfields are not Dickson nearfields if chara \({F \ne 2}\).     

Collective diffusion coefficient of proteins with hydrodynamic, electrostatic, and adhesive interactions

A theory is presented for lambdaC, the coefficient of the first-order correction in the density of the collective diffusion coefficient, for protein spheres interacting by electrostatic and adhesive forces. An extensive numerical analysis of the Stokesian hydrodynamics of two moving spheres is given so as to gauge the precise impact of lubrication forces. An effective stickiness is introduced and a simple formula for lambdaC in terms of this variable is put forward. A precise though more elaborate approximation for lambdaC is also developed. These and numerically exact expressions for lambdaC are compared with experimental data on lysozyme at pH 4.5 and a range of ionic strengths between 0.05M and 2M.     

Nonlinear magneto-optical probing of magnetic interfaces

Received: 16 October 1998