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81.
Boomishankar R Ledger J Guilbaud JB Campbell NL Bacsa J Bonar-Law R Khimyak YZ Steiner A 《Chemical communications (Cambridge, England)》2007,(48):5152-5154
The cyclotriphosphazene P(3)N(3)Cl(6) reacts with six equivalents of DMAP (4-(dimethylamino)pyridine) in superheated chloroform to form crystals of composition [P(3)N(3)(DMAP)(6)]Cl(6).19CHCl(3) comprising [P(3)N(3)(DMAP)(6)](6+) ions, which host five chloride ions in basket-type cavities on either side of the ring and at equatorial positions via tetradentate ortho-H-donor arrangements. 相似文献
82.
Hong SU Malaisamy R Bruening ML 《Langmuir : the ACS journal of surfaces and colloids》2007,23(4):1716-1722
Nanofiltration (NF) is an attractive technique for reducing F- concentrations to acceptable levels in drinking water, but commercial NF membranes such as NF 270 and NF 90 show minimal Cl-/F- selectivity. In contrast, simple layer-by-layer deposition of 4.5-bilayer poly(styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films on porous alumina supports yields NF membranes that exhibit Cl-/F- and Br-/F- selectivities>3 along with solution fluxes that are >3-fold higher than those of the commercial membranes. Fluoride rejection by (PSS/PDADMAC)4PSS membranes, which is >70%, is independent of pressure over a range of 3.6 to 6.0 bar, suggesting that the primary transport mechanism in these films is convection. Moreover, the fact that Br-/F- selectivity is 12% higher than Cl-/F- selectivity suggests that discrimination among the monovalent ions is based on size (Stokes radius). Chloride/fluoride selectivities are essentially constant over Cl-/F- feed ratios from 1 to 60, so these separations will be viable over a range of conditions. Interestingly, PSS/protonated poly(allylamine) films show little Cl-/F- selectivity, and the selectivity of PSS/PDADMAC membranes is a strong function of the number of deposited layers, indicating that NF properties are very sensitive to film structure. 相似文献
83.
A low radio frequency power polarization inversion spin exchange at the magic angle (PISEMA) pulse sequence is described for the measurement of heteronuclear dipolar couplings from solids. The method employs a time averaged nutation concept to significantly reduce the rf power required to spin-lock low gamma nuclear spins in PISEMA experiments. The efficacy of the 2D method is demonstrated on a single crystal of n-acetyl-L-(15)N-valyl-L-(15)N-leucine dipeptide to measure (1)H-(15)N dipolar couplings and a liquid crystal sample to measure (1)H-(13)C dipolar couplings. 相似文献
84.
M. Arivanandhan K. Sankaranarayanan K. Ramamoorthy C. Sanjeeviraja P. Ramasamy 《Crystal Research and Technology》2004,39(8):692-698
In order to grow benzophenone single crystal, an organic nonlinear optical material, a cost‐effective Vertical Bridgman‐Stockbarger system has been designed and fabricated by employing a two‐zone, transparent furnace made out of immiscible liquids. Transparent, optical quality benzophenone single crystals were successfully grown as a result of a suitable thermal gradient achieved by means of introducing an intermediate liquid in between the two immiscible liquids. The effect of change in the volume of the intermediate liquid thereby the thermal gradient on the growth parameters was analyzed. The quality of the grown single crystal was justified using X‐ray powder diffraction analysis, FTIR, TG‐DTA and optical transmission studies. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
85.
86.
Karunanithi Anandababu Ramamoorthy Ramasubramanian Prof. Dr. Hubert Wadepohl Prof. Dr. Peter Comba Neethinathan Johnee Britto Prof. Dr. Madhavan Jaccob Prof. Dr. Ramasamy Mayilmurugan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9540-9547
The iron(II) complexes [Fe(L)(MeCN)3](SO3CF3)2 (L are two derivatives of tris(2-pyridyl)-based ligands) have been synthesized as models for cysteine dioxygenase (CDO). The molecular structure of one of the complexes exhibits octahedral coordination geometry and the Fe−Npy bond lengths [1.953(4)–1.972(4) Å] are similar to those in the Cys-bound FeII-CDO; Fe−NHis: 1.893–2.199 Å. The iron(II) centers of the model complexes exhibit relatively high FeIII/II redox potentials (E1/2=0.988–1.380 V vs. ferrocene/ferrocenium electrode, Fc/Fc+), within the range for O2 activation and typical for the corresponding nonheme iron enzymes. The reaction of in situ generated [Fe(L)(MeCN)(SPh)]+ with excess O2 in acetonitrile (MeCN) yields selectively the doubly oxygenated phenylsulfinic acid product. Isotopic labeling studies using 18O2 confirm the incorporation of both oxygen atoms of O2 into the product. Kinetic and preliminary DFT studies reveal the involvement of an FeIII peroxido intermediate with a rhombic S= FeIII center (687–696 nm; g≈2.46–2.48, 2.13–2.15, 1.92–1.94), similar to the spectroscopic signature of the low-spin Cys-bound FeIIICDO (650 nm, g≈2.47, 2.29, 1.90). The proposed FeIII peroxido intermediates have been trapped, and the O−O stretching frequencies are in the expected range (approximately 920 and 820 cm−1 for the alkyl- and hydroperoxido species, respectively). The model complexes have a structure similar to that of the enzyme and structural aspects as well as the reactivity are discussed. 相似文献
87.
AK Gupta A Steiner R Boomishankar 《Dalton transactions (Cambridge, England : 2003)》2012,41(32):9753-9759
Mild deprotonation of a 2-pyridyl (py)-functionalized phosphoric triamide [PO(NHpy)(3)] in the absence of an external base was studied in the presence of various silver(I) salts. Interesting examples of octa- and hepta-nuclear Ag(I) complexes coordinated to imido and pyridyl groups were obtained when more reactive Ag(I) salts, such as AgClO(4) and AgBF(4), were used, while the less reactive AgNO(3) reacts only with the peripheral pyridyl groups leading to a tri-nuclear cluster. Structural determination of these Ag(I) complexes show that sequential deprotonation of the ligand amino protons were achieved forming imido P(V) species analogous to the H(2)PO(4)(-) and HPO(4)(2-) ions. 相似文献
88.
Matthew A.J. Duncton Leticia Ayala Carl Kaub Satyanarayana Janagani William T. Edwards Nina Orike Krithika Ramamoorthy John Kincaid Michael G. Kelly 《Tetrahedron letters》2010,51(7):1009-823
Dibutyl-2-(trifluoromethyl)cyclopropylboronate 2, available in one step from commercially available reagents, serves as a useful (trifluoromethyl)cyclopropylating reagent by participating in a palladium-catalyzed Suzuki coupling. The use of boronate ester 2 in medicinal chemistry was exemplified by preparation of TRPV1 receptor antagonists. 相似文献
89.
Polking MJ Zheng H Ramesh R Alivisatos AP 《Journal of the American Chemical Society》2011,133(7):2044-2047
Germanium telluride (GeTe) exhibits interesting materials properties, including a reversible amorphous-to-crystalline phase transition and a room-temperature ferroelectric distortion, and has demonstrated potential for nonvolatile memory applications. Here, a colloidal approach to the synthesis of GeTe nanocrystals over a wide range of sizes is demonstrated. These nanocrystals have size distributions of 10-20% and exist in the rhombohedral structure characteristic of the low-temperature polar phase. The production of nanocrystals of widely varying sizes is facilitated by the use of Ge(II) precursors with different reactivities. A transition from a monodomain state to a state with multiple polarization domains is observed with increasing size, leading to the formation of richly faceted nanostructures. These results provide a starting point for deeper investigation into the size-scaling and fundamental nature of polar-ordering and phase-change processes in nanoscale systems. 相似文献
90.
Dr. Prabhakaran Rajasekar Abinash Swain Prof. Dr. Gopalan Rajaraman Prof. Dr. Ramamoorthy Boomishankar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10012-10015
The synthesis of cages with a polyradical framework remains a challenging task. Herein is reported an enantiomeric pair of quinoid-bridged polyradical tetrahedral palladium(II) cages that are stabilized by an unusual dianionic diradical form (dhbq..2−). These cages have been characterized by electron paramagnetic resonance and UV-visible spectroscopy, squid magnetometry and mass spectrometry. Single-crystal-derived X-ray investigations of the iso-structural cages built on fluoranilate linkers confirm the tetrahedral structure of the obtained radical cages. Theoretical calculations showed that the diradical state of the dhbq anions is more stable than the usual monoradical state. A weak ferromagnetic exchange between adjacent radical centers was observed in DFT studies. 相似文献