Search results for "ionit"
showing 10 items of 142 documents
Computational investigations of 18-electron triatomic sulfur–nitrogen anions
2018
MRCI-SD/def2-QZVP and PBE0/def2-QZVP calculations have been employed for the analysis of geometries, stabilities, and bonding of isomers of the 18-electron anions N2S2−, NS2−, and NSO−. Isomers of the isoelectronic neutral molecules SO2, S2O, S3, and O3 are included for comparison. The sulfur-centered acyclic NSN2−, NSS−, and NSO− anions are the most stable isomers of their respective molecular compositions. However, the nitrogen-centered isomers SNS− and SNO− lie close enough in energy to their more stable counterparts to allow their occurrence. The experimental structural information, where available, is in good agreement with the optimized bond parameters. The bonding in all investigate…
Foldameerien isäntä-vieraskemia
2017
Tutkielman kirjallisessa osassa tarkastellaan foldameerejä isäntä-vieraskemian näkökulmasta. Foldameerit voivat sitoa rakenteeseensa erilaisia vierasmolekyylejä, jolloin muodostuu isäntä-vieraskomplekseja. Kirjallisuudesta valittiin tarkasteluun mielenkiintoisimpia anioneja, kationeja ja neutraaleja vierasmolekyylejä sitovia foldameereja ja perehdyttiin niiden vuorovaikutuksiin. Lisäksi tarkasteltiin vierasmolekyylin sitoutumisen aikaansaamia muutoksia foldameerien konformaatiossa. Kokeellisen osan tarkoituksena oli syntetisoida pitkä, 11 aromaattista rengasta sisältävä aryyliamidifoldameeri käyttäen hyväksi pääasiassa peptidikytkentäreaktioita. Koska synteesi osoittautui erittäin haasteell…
Oligoamide Foldamers as Helical Chloride Receptors-the Influence of Electron-Withdrawing Substituents on Anion-Binding Interactions.
2019
The anion-binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1 H NMR spectra of the foldamers in [D6 ]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the …
Role of Alkyl Substituent and Solvent on the Structural, Thermal, and Magnetic Properties of Binary Radical Salts of 1,2,3,5-Dithia- or Diselenadiazo…
2022
The synthesis, structural, thermal, and magnetic properties of a series of simple binary organic salts based on the radical anion of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 4-(N-alkylpyridinium-3-yl)-1,2,3,5-dithiadiazolyl (DTDA), 1R (R = Et, Pr, Bu), radical cations and their heavier selenium analogues (DSDA), 2R, are described. Single-crystal X-ray structural analyses reveal that short alkyl substituents on the pyridinium moiety of DTDA/DSDA cations lead to crystallization of isostructural acetonitrile (MeCN) solvates 1Et·MeCN, 1Pr·MeCN, 2Et·MeCN, and 2Pr·MeCN with trans-cofacial DTDA radical cation and eclipsed-cofacial TCNQ radical anion dimers. A slight increase in the substituent …
Oligoamide Foldamers as Helical Chloride Receptors : the Influence of Electron-Withdrawing Substituents on Anion-Binding Interactions
2019
The anion‐binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1H NMR spectra of the foldamers in [D6]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the re…
Halofiilisen HMV1-arkkiviruksen virionirakenteen selvittäminen hajotuskokeiden avulla
2008
Redox-Responsive Host-Guest Chemistry of a Flexible Cage with Naphthalene Walls
2020
“Naphthocage”, a naphthalene-based organic cage, reveals very strong binding (up to 1010 M–1) to aromatic (di)cationic guests, i.e., the tetrathiafulvalene mono- and dication and methyl viologen. Intercalation of the guests between two naphthalene walls is mediated by C–H···O, C–H···π, and cation···π interactions. The guests can be switched into and out of the cage by redox processes with high binding selectivity. Oxidation of the flexible cage itself in the absence of a guest leads to a stable radical cation with the oxidized naphthalene intercalated between and stabilized by the other two. Encapsulated guest cations are released from the cavity upon cage oxidation, paving the way to futur…
JYFLTRAP -laitteistolla mitattujen atomimassojen vertailu atomimassamalleihin
2011
Jyväskylän yliopiston IGISOL-laitteiston JYFLTRAP Penningin loukulla on mitattu atomimassoja suurella tarkkuudella. Atomimassoja tarvitaan, jotta voitaisiin esimerkiksi tutkia atomin ytimen rakennetta ja sidosenergioita. Kaikkia ytimiä ei kuitenkaan ole mahdollista saada mitattua nykytekniikoilla, vaan tarvitaan massaennusteita. Tässä pro gradu -työssä vertailtiin teoreettisista atomimassaennusteista ja Atomimassaevaluaatiosta (AME2003) saatuja massojen arvoja JYFLTRAP:lla mitattuihin massoihin. Työtä varten laskettiin kokeellisten ja teoreettisten massavajeiden erotukset, kahden neutronin sidosenergiat, teoreettisten ja kokeellisten S2n-arvojen erotukset ja neutronin kuoriaukkoenergiat neu…
Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks
2009
A series of 1,3-bis(2,6-diisopropylphenyl)-5-methyl-1,3-diaza-4,6-diborabenzenes with methyl, phenyl, and dimethylamino substituents on the ring boron atoms were prepared using the cyclocondensation reaction between N,N′-bis(2,6-diisopropylphenyl)trimethylsilylformamidine and the appropriately substituted 1,1-bis(organochloroboryl)ethane, followed by deprotonation of the cationic ring intermediate. The planar, heterocyclic benzene analogues could be further deprotonated at the other ring carbon using an additional equivalent of potassium hexamethyldisilazide to yield organometallic derivatives akin to the potassium phenylide. The potassium cations could be efficiently sequestered in both so…
Radioactive Beams for Image-Guided Particle Therapy : The BARB Experiment at GSI
2021
Several techniques are under development for image-guidance in particle therapy. Positron (β+) emission tomography (PET) is in use since many years, because accelerated ions generate positron-emitting isotopes by nuclear fragmentation in the human body. In heavy ion therapy, a major part of the PET signals is produced by β+-emitters generated via projectile fragmentation. A much higher intensity for the PET signal can be obtained using β+-radioactive beams directly for treatment. This idea has always been hampered by the low intensity of the secondary beams, produced by fragmentation of the primary, stable beams. With the intensity upgrade of the SIS-18 synchrotron and the isotopic separati…