- Dihydrogen phosphate and hydrogen sulphate of 1,4-dimethyl-1,4- diazabicyclo[2.2.2]octane-1,4-diium: Crystal structures, hydrogen bonding and infrared spectra
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The crystal structures of the title compounds consist of 1,4-dimethyl-1,4-diazabicyclo[2.2.2]octane-1,4-diium cation [C8H 18N2]2+ and [H2PO4] - or [HSO4]- anions. Both crystal structures are monoclinic, the structure of the dihydrogen phosphate (I) is non-centrosymmetric (P21) with a = 6.4090(2) A, b = 13.6920(5) A, c = 7.6140(3) A, β = 94.620(2)°, V = 665.97(4) A3, Z = 2; whereas the unit cell of the hydrogen sulphate (II) is centrosymmetric (P21/c) with a = 13.8460(2) A, b = 12.6610(2) A, c = 8.0360(2) A, β = 99.5800(12)°, V = 1389.10(5) A3, Z = 4. Both the structures are formed by the different bonding patterns of the anions interlinked by strong and moderate O-H???O hydrogen bonds. While the structure of (I) consists of a two-dimensional network of the hydrogen bonded dihydrogen phosphates, the infinite chains of the hydrogen bonded hydrogen sulphates are the basic building unit of the structure (II). In addition to the dominant electrostatic interaction the divalent cations stabilize themselves in the structures by forming several C-H???O hydrogen bonds to the oxygen atoms of the anions. The IR spectra of both the compounds are strongly affected by the hydrogen bonds whose influence on OH stretching vibrations is analysed by means of the DFT calculations in the solid state.
- Kaman, Ondrej,Smrcok, Lubomir,Cisarova, Ivana,Havlicek, David
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- A convenient synthesis of [11C]paraquat and other [N-methyl-11C]bisquaternary ammonium compounds
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[11C]Paraquat was synthesized by the reaction of [11C]methyl triflate with the mono-triflate salt of 1-methyl-[4,4′]bipyridinyl. The product was selectively separated from the precursor by a microcolumn of Chelex 100 ion exchange resin. The method was applied to the synthesis of a variety of [N-methyl-11C]bisquaternary ammonium compounds. This is the first reported use of a chelating cation exchange resin for the selective purification of organic dications. Copyright
- Jewett, Douglas M.,Kilbourn, Michael R.
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- Crystal structures and dielectric properties of two salts of nickel-bis-1,2-dithiolene with noncentrosymmetric organic cations
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Two nickel-bis-1,2-dithiolene salts, [1,4-dimethyl-DABCO][Ni(mnt)2] (1) and (TMSF)2[Ni(mnt)2] (2) (mnt2? = maleonitriledithiolate, 1,4-dimethyl-DABCO2+ = 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane and TMSF+ = trimethylsulfonium), were synthesized and characterized by elemental analysis, IR spectra, thermal analysis and single crystal structures. Both 1 and 2 crystallize in monoclinic space group C2/c, with a formula and cell parameters of C16H18N6NiS4, a = 16.9688(8) ? b = 9.3003(5) ? 13.4090(6) ? and β = 103.244(2)° for 1 at 293 K versus C14H18N4NiS6, a = 17.108(3) ? b = 10.2932(16) ? 14.071(2) ? and β = 118.845(4)° for 2 at 293 K. Moreover, two salts show similar packing structure, with the arrangements of alternating layer of anions and cations, and the layers are parallel to the crystallographic ab-plane. Both 1 and 2 display analogous dielectric behavior, which dielectric permittivity is almost a constant with ε′ ≈ 12 at the temperature below 270 K for 1 versus 215 K for 2, and two steps of dielectric relaxations appear in the higher temperature regime, which originate from the molecular dipole orientation and the ion migration.
- He, Jin-Yu,Chen, Xuan-Rong,Qian, Yin,Liu, Jian-Lan,Ren, Xiao-Ming
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- Controlling the Recognition and Reactivity of Alkyl Ammonium Guests Using an Anion Coordination-Based Tetrahedral Cage
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Caged structures have found wide application in a variety of areas, including guest encapsulation and catalysis. Although metal-based cages have dominated the field, anion-coordination-based cages are emerging as a new type of supramolecular ensemble with
- Zhang, Wenyao,Yang, Dong,Zhao, Jie,Hou, Lekai,Sessler, Jonathan L.,Yang, Xiao-Juan,Wu, Biao
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supporting information
p. 5248 - 5256
(2018/04/23)
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- Synthesis, Characterization, and Reactivity of Thermally Stable Anhydrous Quaternary Ammonium Fluorides
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The synthesis and properties of a new class of anhydrous quaternary ammonium fluorides, based on the rigid skeleton azabicyclo[2.2.2]octane, is described. Compounds 2a-d were easily prepared by passing the corresponding ammonium iodides over fluoride-based resin followed by drying their hydrated form at 100 or 140 °C under reduced pressure. The stability (experimental and theoretical study), solubility, reactivity, and characterization by solution and solid-state MAS NMR are discussed.
- Elias, Shlomi,Karton-Lifshin, Naama,Yehezkel, Lea,Ashkenazi, Nissan,Columbus, Ishay,Zafrani, Yossi
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supporting information
p. 3039 - 3042
(2017/06/23)
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- Quaternary ammonium ions can externally block voltage-gated K+ channels. Establishing a theoretical and experimental model that predicts KDS and the selectivity of K+ over Na+ ions
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The physicochemical basis for the high ion selectivity of potassium channels is poorly understood. In the present studies, external blockade of cloned voltage-gated potassium channels with alkyl quaternary ammonium ions are analyzed from a model derived from theory and experimental data. Atomic mass units, electrostatic potential residing on the nitrogen atom, the COSMO van der Waals solvent accessible surface, the Onsager solvation model, and the isodensity PCM solvation model are computed at the semi-empirical and the ab initio levels of theory. A structure-activity relationship (SAR) exists between the calculated values and the experimentally obtained KD (mM). The SAR model gives us KD predictions and when K+ and Na+ are incorporated into the model, it dramatically predicts the selectivity of K+ over Na+ ions.
- Wempe
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- Diazabicycloalkanes with nitrogen atoms in the nodal positions. 8. Effect of c-substituents on the N-methylation of 1,4-diazabi cyclo[2.2.2]octanes and the demethylation of their bisquaternary salts
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The introduction of substituents with various inductive constants in the 2 position of the diazabicyclo]2.2.2]octane ring gives rise to a change in the pKa values and affects the ease of introduction of a methyl group in the 1 and 4 positions, as well as the rate of demethylation of the bisquaternary salts from the 1 position. When 1,4-diazabicyclo[2.2.2]octane is treated with a sufficiently strong nucleophile, the ring is opened to give a piperazine derivative.
- Vysochin,Shishkin
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p. 196 - 201
(2007/10/02)
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