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11.
Zinc(II) Hydration in Aqueous Solution: A Raman Spectroscopic Investigation and An ab initio Molecular Orbital Study of Zinc(II) Water Clusters 总被引:1,自引:0,他引:1
Raman spectra of aqueous Zn(II)–perchlorate solutions were measured over broad concentration (0.50–3.54 mol-L–1) and temperature (25–120°C) ranges. The weak polarized band at 390 cm–1 and two depolarized modes at 270 and 214 cm–1 have been assigned to 1(a
1g), 2(e
g), and 5(f
2g) of the zinc–hexaaqua ion. The infrared-active mode at 365 cm–1 has been assigned to 3(f
1u). The vibrational analysis of the species [Zn(OH2)
2
+
] was done on the basis of O
h symmetry (OH2 as point mass). The polarized mode 1(a
1g)-ZnO6 has been followed over the full temperature range and band parameters (band maximum, full width at half height, and intensity) have been examined. The position of the 1(a
1g)-ZnO6 mode shifts only about 4 cm–1 to lower frequencies and broadens by about 32 cm–1 for a 95°C temperature increase. The Raman spectroscopic data suggest that the hexaaqua–Zn(II) ion is thermodynamically stable in perchlorate solution over the temperature and concentration range measured. These findings are in contrast to ZnSO4 solutions, recently measured by one of us, where sulfate replaces a water molecule of the first hydration sphere. Ab initio geometry optimizations and frequency calculations of [Zn(OH2)
2
+
] were carried out at the Hartree–Fock and second-order Møller–Plesset levels of theory, using various basis sets up to 6-31 + G*. The global minimum structure of the hexaaqua–Zn(II) species corresponds with symmetry T
h. The unscaled vibrational frequencies of the [Zn(OH2)
2
+
] are reported. The unscaled vibrational frequencies of the ZnO6, unit are lower than the experimental frequencies (ca. 15%), but scaling the frequencies reproduces the measured frequencies. The theoretical binding enthalpy for [Zn(OH2)
2
+
] was calculated and accounts for ca. 66% of the experimental single-ion hydration enthalpy for Zn(II).Ab initio geometry optimizations and frequency calculations are also reported for a [Zn(OH2)
2
18
] (Zn[6 + 12]) cluster with 6 water molecules in the first sphere and 12 in the second sphere. The global minimum corresponds with T symmetry. Calculated frequencies of the zinc [6 + 12] cluster correspond well with the observed frequencies in solution. The 1-ZnO6 (unscaled) mode occurs at 388 cm–1 almost in perfect correspondence to the experimental value. The theoretical binding enthalpy for [Zn(OH2)
2
18
] was calculated and is very close to the experimental single ion-hydration enthalpy for Zn(II). The water molecules of the first sphere form strong hydrogen bonds with water molecules in the second hydration shell because of the strong polarizing effect of the Zn(II) ion. The importance of the second hydration sphere is discussed. 相似文献
12.
Solvent isotope effects on differential heats of solution of NaCl in HOH and DOD have been measured between 0.01 and 4m and from 5 to 40°C. These data are supplemented by integral heats of solution measured at 0.465m and from 5 to 75°C, and with heats of dilution over the same temperature range. The integral heat measurements include studies on otheralkali halides (KCl, NaI, NaBr), and the dilution measurements include some data for KCl. In the NaCl studies, particular attention was paid to the low-concentration region. Values of the partial molal enthalpiesL 1 adL 2 are derived for solution in both isotopic waters, and new values for the isotope effect on the standard enthalpy of solution ΔL 2 s = (ΔH 2 0 ) d←w as a function of temperature are reported. Comparisons are made with previous work where possible. In contrast to statements made by earlier authors, examination of the low-concentration data reveals a \(\surd \overline m\) dependence within experimental error. 相似文献
13.
[reaction: see text] The tethered aminohydroxylation (TA) of acyclic allylic carbamates has been achieved in a stereospecific and stereoselective manner. Unusually high levels of stereocontrol were observed in the oxidation of 1,1-disubstituted substrates. 相似文献
14.
J. Edward Schneider Jr. Tahereh Tabatabaie Lindsay Maidt Renee Horning Smith Xuan Nguyen Quentin Pye Robert A. Floyd 《Photochemistry and photobiology》1998,67(3):350-357
A spectrum of oxidative lesions was observed in a bacteriophage-based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Qβ were exposed to methylene blue plus light (MB+L), inactivating events, or "hits" occurred that were oxygen-dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8-oxo-7,8-dihydroguanine (8-oxoGua), and (3) single-strand breaks (ssb) in the RNA genome and (4) RNA-protein crosslinks. Formation of carbonyl groups associated with protein in the Qβ phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Qβ genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full-length Qβ RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8-oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB+L, crosslink formation between Qβ RNA and protein was observed by virtue of the location of RNA at the interface of phenol-aqueous extractions of phage suspensions. A significant increase over background of RNA-protein complexes (including full-length Qβ RNA) was observed at the lowest concentration of MB tested (0.5 μ M ), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Qβ inactivation and its expected lethality, RNA-protein crosslink formation may be important as an inactivating lesion in bacteriophage Qβ following MB+L exposure. 相似文献
15.
Zusammenfassung Für die balneologische Beurteilung des Torfes werden die am Balneologischen Institut bei der Universität München und an der Deutschen Forschungsanstalt für Lebensmittelchemie München ausgearbeiteten und gebräuchlichen Methoden der chemischen und physikalischen Untersuchung beschrieben.Der Kleinen Badetorfanalyse, die für die überwiegende Mehrzahl der Badetorfe Deutsehlands in Frage kommt, wird ein Verfahren der abgekürzten organischen Gruppenanalyse zugrunde gelegt, das auf den früher von W. BENADE sowie von S. W. Souci u. Mitarb. ausgearbeiteten Torf-Analysengängen aufgebaut ist und die quantitative Ermittelung der wichtigsten Stoffgruppen (gekennzeichnet durch den vorwiegenden Gehalt an Huminsäuren, Bitumen, wasserlöslichen Kohlenhydraten, Hemicellulosen und Cellulose, Lignin und Huminen) ermöglicht. Die angegebenen Methoden gestatten einen weiteren Ausbau zur Groen Badetorfanalyse.Ein Berechnungsschema und eine tabellarische Übersicht zum Zwecke der einheitlichen Darstellung der Untersuchungsergebnisse werden angegeben.Frl. Anneliese Hartmann, Technische Assistentin, sei für ihre sorgfältige Mitarbeit auch an dieser Stelle bestens gedankt. 相似文献
16.
17.
Dr. Quentin Bonnin Tereza Edlová Dr. E. Daiann Sosa Carrizo Prof. Dr. Paul Fleurat-Lessard Dr. Stéphane Brandès Dr. Hélène Cattey Dr. Philippe Richard Prof. Dr. Pierre Le Gendre Dr. Adrien T. Normand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18175-18187
Cationic amidotitanocene complexes [Cp2Ti(NPhAr)][B(C6F5)4] (Cp=η5-C5H5; Ar=phenyl ( 1 a ), p-tolyl ( 1 b ), p-anisyl ( 1 c )) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti−N bond in 1 a–c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a–c undergo photolytic Ti−N cleavage to release Ti(III) species and aminyl radicals ⋅ NPhAr. Reaction of 1 b with H3BNHMe2 results in fast homolytic Ti−N cleavage to give [Cp2Ti(H3BNHMe2)][B(C6F5)4] ( 3 ). 1 a–c are highly active precatalysts in olefin hydrogenation and silanes/amines cross-dehydrogenative coupling, whilst 3 efficiently catalyzes amine-borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H2 activation key step was disclosed using the Activation Strain Model (ASM). 相似文献
18.
Frédéric Blaffart Quentin Van Overmeere Thomas Pardoen Joris Proost 《Journal of Solid State Electrochemistry》2013,17(7):1945-1954
Stresses due to electric fields in thermal and anodic silica thin layers can impact the devices using these films as dielectrics. Accurately quantifying the internal stress as a function of the electric field is thus of technological importance. In this work, electrostrictive stresses are monitored during cyclic polarization of silica thin films on silicon and during the growth of anodic silica. These are obtained by combining curvature and ellipsometry measurements in situ. In silica films grown by thermal oxidation of silicon, the electric field can generate either tensile or compressive stresses depending on its magnitude and on the silica polarization history. The electromechanical coupling in thermal silica is assumed to be controlled by a reversible change of the dipole organization. For anodic silica films, the stress generated by the electric field is tensile and varies linearly with the square of the electric field above 0.26 V2/nm2 under both cyclic polarization and oxidation conditions. 相似文献
19.
20.
Quentin Vanbellingen Paul Servin Anaïs Coinaud Sonia Mallet-Ladeira Rgis Laurent Anne-Marie Caminade 《Molecules (Basel, Switzerland)》2021,26(8)
Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation. 相似文献