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71.
Cho YS Yi GR Lim JM Kim SH Manoharan VN Pine DJ Yang SM 《Journal of the American Chemical Society》2005,127(45):15968-15975
Most of the colloidal clusters have been produced from oil-in-water emulsions with identical microspheres dispersed in oil droplets. Here, we present new types of binary colloidal clusters from phase-inverted water-in-oil emulsions using various combinations of two different colloids with several size ratios: monodisperse silica or polystyrene microspheres for larger particles and silica or titania nanoparticles for smaller particles. Obviously, a better understanding of how finite groups of different colloids self-organize in a confined geometry may help us control the structure of matter at multiple length scales. In addition, since aqueous dispersions have much better phase stability, we could produce much more diverse colloidal materials from water-in-oil emulsions rather than from oil-in-water emulsions. Interestingly, the configurations of the large microspheres were not changed by the presence of the small particles. However, the arrangement of the smaller particles was strongly dependent on the nature of the interparticle interactions. The experimentally observed structural evolutions were consistent with the numerical simulations calculated using Surface Evolver. These clusters with nonisotropic structures can be used as building blocks for novel colloidal structures with unusual properties or by themselves as light scatterers, diffusers, and complex adaptive matter exhibiting emergent behavior. 相似文献
72.
[reaction: see text] The allyl group, which serves as a protecting group for an internucleotide bond for both phosphates and phosphorothioates, can be easily removed by good nucleophiles under weakly basic or neutral conditions. For a practical synthesis on solid support, camphorsulfonyloxaziridine was used as the oxidizing agent for synthesizing DNA, while the Beaucage reagent was used for preparing phosphorothioate oligomers. Both types of oligonucleotides were easily deprotected by concentrated ammonium hydroxide containing 2% mercaptoethanol. 相似文献
73.
P.?Thangadurai S.?RamasamyEmail author T. K.?Kundu P. T.?Manoharan 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(4):447-454
Nanocrystalline samples of PbF2 doped with 0.05, 0.1, 0.4 and 1 mol%
Mn2+, used as paramagnetic probe, were prepared by inert gas
condensation technique. All the samples were vacuum annealed at different
temperatures to get different grain sizes. The X-ray diffraction studies
showed the dominant content of -PbF2 phase with a fractional
quantity of -PbF2. Thermal stability and sublattice melting
were studied by TGA and DSC respectively. EPR measurements were made on all
these samples at 77 and 300 K. The EPR spectra of all samples were found to
contain well resolved sextet arising from the Mn2+ ions that occupied
the cubic sites of Pb2+ ion of PbF2 lattice. The lower
concentration of the Mn2+ ions (0.05 and 0.1 mol%) clearly monitored
the Pb2+ environment in the PbF2 lattice. The 0.4 mol% showed
the presence of only the cubic sites with a minor concentration of the
orthorhombic sites. The spectra corresponding to 1 mol% Mn2+ clearly
showed two different components. The isotropic nature of the 1 mol%
as-prepared sample implied that there was no cluster formation and hence
this EPR spectrum was taken as the single ion spectrum. The annealed samples
contain two spectral components; one is from the isolated single ions and
the other one from the Mn2+ clusters. The spectral component of Mn2+ clusters was obtained by subtracting the spectrum for the
as-prepared sample for the spectra of annealed samples. The extracted
cluster phase spectra and the pure spectrum from the as-prepared sample were
then combined to simulate the entire set of experimental spectra. The
simulated spectra were found to be in good agreement with the experimental
data. The g values obtained were in the range very close to the free
electron g factor as the electrons are in the S state (L=0). 相似文献
74.
Jonathan OShea Christopher S. Theile Rajat Das I. Ramesh Babu Klaus Charisse Muthiah Manoharan Martin A. Maier Ivan Zlatev 《Tetrahedron》2018,74(42):6182-6186
5′-(E)-Vinylphosphonate (VP) is an effective bioisostere of the natural 5′-monophosphate in small interfering RNAs (siRNAs). Solid-phase synthesis of VP-siRNAs requires the use of appropriately protected VP-phosphoramidites in combination with optimal oligonucleotide deprotection conditions. Addition of 3% (v) neat diethylamine to the standard aqueous ammonia deprotection conditions allows clean and rapid one-step deprotection of 5′-[O,O-bis(pivaloyloxymethyl)] (POM)-protected VP oligonucleotides, minimizing side reactions and impurities, which broadly enhances the scope of VP oligonucleotide synthesis. 相似文献
75.
C. Mahadevan M. Seshasayee P. Kuppusamy P. T. Manoharan 《Journal of chemical crystallography》1985,15(4):305-316
The crystal and molecular structure of the title compound, (C13H11N2)[Ni(S2C6H4)2], is reported. Crystals are triclinic, space groupP¯1(No.2) withZ=2 in a unit cell of dimensionsa=9.363(1),b=10.148(1),c=13.623(1) Å,=85.64(1),=107.33(1), and =113.10(1)°. The structure was solved by the heavy-atom method and refined by the method of full-matrix least squares toR=0.036 for 2874 unique reflections. The metal atom of the anion has an approximate square-planar configuration. The metal atoms occupy the origins and A-face centers of the lattice. The anions with the metal atoms in the origins stack along thec-axis, the interplanar separation being thec-axis lattice repeat of 13.623(1) Å. The anions with the metal atoms in theA-face centers and the cations form a mixed stack along the short diagonal of theab-plane. The short interplanar distances (C–A=A–C=3.43 Å and C-C=3.91 Å) in the mixed stack (CAC-CAC) show the possibility of unusual electrical behavior. There is no evidence of direct or indirect metal-metal interaction.This work was supported by the Department of Science and Technology, Government of India, New Delhi, for which we are grateful. One of the authors (PK) also expresses his thanks to the U.G.C., New Delhi and Pachaiyappas College, Madras, for the award of FIP Fellowship. 相似文献
76.
Ragaverthini Chinnasamy Jada Ravi Vuppu Vinay Pradeep Deepak Manoharan Dr. Franziska Emmerling Dr. Biswajit Bhattacharya Prof. Dr. Soumyajit Ghosh Prof. Dr. Rajadurai Chandrasekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(40):e202200905
Flexible organic crystals (elastic and plastic) are important materials for optical waveguides, tunable optoelectronic devices, and photonic integrated circuits. Here, we present highly elastic organic crystals of a Schiff base, 1-((E)-(2,5-dichlorophenylimino)methyl)naphthalen-2-ol ( 1 ), and an azine molecule, 2,4-dibromo-6-((E)-((E)-(2,6-dichlorobenzylidene)hydrazono)methyl)phenol ( 2 ). These microcrystals are highly flexible under external mechanical force, both in the macroscopic and the microscopic regimes. The mechanical flexibility of these crystals arises as a result of weak and dispersive C−H⋅⋅⋅Cl, Cl⋅⋅⋅Cl, Br⋅⋅⋅Br, and π⋅⋅⋅π stacking interactions. Singly and doubly-bent geometries were achieved from their straight shape by a micromechanical approach using the AFM cantilever tip. Crystals of molecules 1 and 2 display a bright-green and red fluorescence (FL), respectively, and selective reabsorption of a part of their FL band. Crystals 1 and 2 exhibit optical-path-dependent low loss emissions at the termini of crystal in their straight and even in extremely bent geometries. Interestingly, the excitation position-dependent optical modes appear in both linear and bent waveguides of crystals 1 and 2 , confirming their light-trapping ability. 相似文献
77.
78.
Intramolecular hydrogen atom (H-atom) abstraction from the o-OCH3 group effectively intercepts the p-benzyne intermediate in the Bergman cycloaromatization of 2,3-diethynyl-1-methoxybenzene (1) before this intermediate undergoes either retro-Bergman ring opening or external H-atom abstraction. This process leads to the formation of a new diradical and renders the cyclization step essentially irreversible. Chemical and kinetic consequences of this phenomenon were investigated through the combination of computational and experimental studies. 相似文献
79.
Enachescu C Varret F Codjovi E Linarès J Floquet S Manikandan P Manoharan PT 《The journal of physical chemistry. B》2006,110(12):5883-5888
The molecular solid [Fe(II)L(2)](ClO(4))(2).CH(3)CN where L is 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine provides a stable high-spin (HS) state at low temperature. Photoexcitation and subsequent relaxation have been studied using light-induced excited state spin trapping [LIESST(H --> L)] in the 700-850 nm range, determination of T(LIESST), relaxation curves at different temperatures, and temperature dependence of the light-induced spin equilibrium under constant irradiation. The measured photoinduced population of the metastable low-spin (LS) state (<30%) was drastically limited by the concomitant L --> H photoprocess. The absence of static light-induced thermal hysteresis and the stretched exponential shape of the relaxation curves respectively revealed the absence of sizable interactions and a large spreading of the activation energies attributed to the ligand flexibility. The whole data set has been simulated using a linear rate equation, with a simplified correction for the bulk extinction of light in the powder sample. 相似文献
80.
Palanichamy Manikandan K. R. Justin Thomas Periakaruppan T. Manoharan 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):308-309
The title compound, [Cu(NCS)2(C17H21N5)], displays a distorted square‐pyramidal coordination geometry, where the basal plane is defined by the tridentate ligand and by one of the thiocyanate ions. The apical position is occupied by the other thiocyanate ion. 相似文献