Photonic switches and switch arrays on LiNbO3

In recent years there has been tremendous progress in lithium niobate-based photonic switches. The various switch configurations proposed and implemented, and their characteristics, are reviewed. A summary of the device technology is given. Performance analysis based on different architecture and the size of arrays that can be relalized are discussed.Indian Institute of Science, Bangalore, India     

ORGANOSTANNOXANE MOTIFS IN CAGES AND SUPRAMOLECULAR ARCHITECTURES

The reactions of n-butyl stannonic acid with(PhO) ₂ P(O)H leads to the formation of a hexameric tin cage [{(n-BuSn) ₃ (PhO) ₃ O} ₂ {HPO ₃ } ₄ ].This reaction involves an in situ P─O bond cleavage and the generation of a [HPO ₃ ] ^2? ion. A direct reaction of six equivalents of n-BuSnO(OH) acid with six equivalents of C ₆ H ₅ OH and four equivalents of H ₃ PO ₃ also leads to the formation of same cage structure. A tetranuclear organooxotin cage[(PhCH ₂ ) ₂ Sn ₂ O(O ₂ P(OH)-t-Bu) ₄ ] ₂ has been assembled by debenzylation involving the reaction of (PhCH ₂ ) ₂ SnCl ₂ ,(PhCH ₂ ) ₂ SnO·H ₂ O or (PhCH ₂ ) ₃ SnCl with two equivalents of t-BuP(O)OH ₂ . A half-cage intermediate [(PhCH ₂ ) ₂ Sn ₂ O(O ₂ P(OH)-t-Bu) ₄ ] has been detected. New organotin cations of the type [n-Bu ₂ Sn(H ₂ O) ₄ ] ²⁺[2,5-Me ₂ -C ₆ H ₃ SO ₃ ]^? ₂ and {[n-Bu ₂ Sn(H ₂ O) ₃ LSn(H ₂ O) ₃ (n-Bu) ₂ ] ²⁺[1,5-(SO ₃ ) ₂ -C ₁₀ H ₆ ] ^2?} have been obtained in the reactions of n-Bu ₂ SnO or (n-Bu ₃ Sn) ₃ O with 2,5-dimethyl sulfonic acid and 1,5-naphthalene disulfonic acid respectively. These organotin cations form interesting supramolecular structures in the solid state as a result of O─H─···O hydrogen bonding.     

Can Low‐Valent Germanium Chemistry Be Practiced Under Ambient Conditions? A Tale of a Water‐Stable Yet Reactive Germylene Monochloride Complex

A germylene monochloride complex ((DPM)GeCl, 1 ) that is water stable was isolated for the first time. Interestingly, it reacts with cesium fluoride under ambient conditions (non‐inert atmosphere and water‐containing solvent) to afford water stable germylene monofluoride complex ((DPM)GeF, 2 ). Due to the usage of DPM (dipyrrinate) ligand, germylene monohalides 1 and 2 show fluorescence in the visible region at 555 and 538 nm, respectively. Compounds 1 and 2 are the first fluorescent germylene complexes and were characterized by multinuclear NMR spectroscopy. The structure of compound 1 was also proved by single crystal X‐ray diffraction studies.     

Si-O and P-O motifs in inorganic rings and clusters

This article presents a brief overview of different kinds of silanols and the important reactions of N-bonded silanetriols. The synthesis and characterization of silanediols containing Si-N and Si-C bonds, (2,4,6-Me₃C₆H₂)N(SiMe₃)Si(Me)(OH)₂ (1e) is described. 1e shows a polymeric crinkled tape type of structure due to extensive intermolecular hydrogen bonding. We also describe the formation of a neutral copper(II) complex derived from the reaction of CuCl₂ with (O)P(3,5-Me₂Pz)₃ where the ligand undergoes a facile P-N bond cleavage and functions as an N₂O type of tridentate ligand.     

Investigation of ring resonators in photonic crystal circuits

In this paper, we propose the implementation of waveguide-coupled ring resonators in photonic crystal integrated circuits. Using two-dimensional finite difference time domain (2D FDTD) method, we study the spectral characteristics of a waveguide-coupled ring carved in two-dimensional photonic crystal of square lattice (2D SLPC) and based on the results, we suitably modify the structure geometry to establish its performance as a ring resonator. We further investigate the effects of ring dimension and crystal parameters on the resonance properties of the ring resonator.     

A reactivity change of a strontium monohydroxide by umpolung to an acid

Controlled hydrolysis of strontium amide LSrN(SiMe 3) 2(thf) (L = CH(CMe2,6- i-Pr 2C 6H 3N) 2) ( 1) gave an unprecedented example of a hydrocarbon-soluble strontium hydroxide, [LSr(thf)(mu-OH) 2Sr(thf) 2L] ( 2). In compound 2, the tetrahydrofuran (THF) molecules can easily replaced by benzophenone and triphenylphosphine oxide to yield [LSr(mu-OH)(OCPh 2)] 2 ( 3) and [LSr(mu-OH)(OPPh 3)] 2 ( 4) compounds. Among the two strontium atoms of 2, one is coordinated to a single THF molecule, while the other is coordinated to two THF molecules. Interestingly, strontium hydroxide complex 2 behaves as an acid in its reaction with Zr(NMe 2) 4 and results in a heterobimetallic oxide, [LSr(mu-O)Zr(NMe 2) 3] 2 ( 5). Compound 5 is dimeric in the solid state and contains a Sr 2Zr 2O 2 core.     

A numerical study of flow through wavy-walled channels

A numerical procedure is developed for the analysis of flow in a channel whose walls describe a travelling wave motion. Following a perturbation method, the primitive variables are expanded in a series with the wall amplitude as the perturbation parameter. The boundary conditions are applied at the mean surface of the channel and the first-order perturbation quantities are calculated using the pseudospectral collocation method. Although limited by the linear analysis, the present approach is not restricted by the Reynolds number of the flow and the wave number and frequency of the wavy-walled channel. Using the computed wall shear stresses, the positions of flow separation and reattachment are determined. The variations in velocity and pressure with frequency of excitation are also presented. © 1998 John Wiley & Sons, Ltd.     

Characterization of pure and urea-doped γ-glycine single crystals grown by solution method

Pure and urea-doped gamma-glycine (γ-glycine) single crystals were grown by solution method with slow evaporation technique. When urea was added as dopant, morphological alterations were noticed in γ-glycine crystals. Structural characterization of the grown crystals was carried out by single and powder X-ray diffraction (XRD) methods and it is observed that the samples crystallize in non-centrosymmetric space groups. UV-visible transmittance studies were performed to analyse optical transparency of pure and urea-doped γ-glycine crystals and found that the crystals were transparent in the entire visible-NIR region. Density and melting point of the grown crystals were measured. Second harmonic generation (SHG) for the grown crystals of this work was confirmed using Nd:YAG laser. Thermogravimetric and differential thermal analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. From Microhardness studies, it is observed that urea-doped γ-glycine crystal is harder than pure (undoped) sample.     

First example of a Sn-C bond cleaved product in the reaction of Ph3SnOSnPh3 with carboxylic acids. 3D-supramolecular network formation in the X-ray crystal structure of [Ph2Sn(OH)OC(O)(Rf)]2, Rf = 2,4,6-(CF3)3C6H2

A 1:2 reaction of Ph3SnOSnPh3 1 with RfCOOH 2 leads to the formation of [Ph2Sn(OH)OC(O)(Rf)]2 3, by means of a facile Sn-C bond cleavage process.     

A lipophilic hexaporphyrin assembly supported on a stannoxane core

Lipophilic hexaporphyrin free-base and copper-metalated assemblies supported on a Sn6O6 core have been synthesized and characterized. The nuclease activity of the copper derivative has been studied.