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Gas‐phase ion–molecule reactions for the identification of the sulfone functionality in protonated analytes in a linear quadrupole ion trap mass spectrometer 下载免费PDF全文
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Dr. Jan H. Blank Dr. Salvador Moncho Allen M. Lunsford Prof. Edward N. Brothers Prof. Marcetta Y. Darensbourg Prof. Ashfaq A. Bengali 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12752-12760
The mechanism and energetics of CO, 1‐hexene, and 1‐hexyne substitution from the complexes (SBenz)2[Fe2(CO)6] (SBenz=SCH2Ph) ( 1 ‐CO), (SBenz)2[Fe2(CO)5(η2‐1‐hexene)] ( 1 ‐(η2‐1‐hexene)), and (SBenz)2[Fe2(CO)5(η2‐1‐hexyne)] ( 1 ‐(η2‐1‐hexyne)) were studied by using time‐resolved infrared spectroscopy. Exchange of both CO and 1‐hexyne by P(OEt)3 and pyridine, respectively, proceeds by a bimolecular mechanism. As similar activation enthalpies are obtained for both reactions, the rate‐determining step in both cases is assumed to be the rotation of the Fe(CO)2L (L=CO or 1‐hexyne) unit to accommodate the incoming ligand. The kinetic profile for the displacement of 1‐hexene is quite different than that for the alkyne and, in this case, both reaction channels, that is, dissociative (SN1) and associative (SN2), were found to be competitive. Because DFT calculations predict similar binding enthalpies of alkene and alkyne to the iron center, the results indicate that the bimolecular pathway in the case of the alkyne is lower in free energy than that of the alkene. In complexes of this type, subtle changes in the departing ligand characteristics and the nature of the mercapto bridge can influence the exchange mechanism, such that more than one reaction pathway is available for ligand substitution. The difference between this and the analogous study of (μ‐pdt)[Fe(CO)3]2 (pdt=S(CH2)3S) underscores the unique characteristics of a three‐atom S?S linker in the active site of diiron hydrogenases. 相似文献
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Kai Liu Dr. Min Shuai Dr. Dong Chen Michael Tuchband Dr. Jennifer Y. Gerasimov Juanjuan Su Qing Liu Wojciech Zajaczkowski Dr. Wojciech Pisula Prof. Dr. Klaus Müllen Prof. Noel A. Clark Prof. Dr. Andreas Herrmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):4898-4903
As DNA exhibits persistent structures with dimensions that exceed the range of their intermolecular forces, solid‐state DNA undergoes thermal degradation at elevated temperatures. Therefore, the realization of solvent‐free DNA fluids, including liquid crystals and liquids, still remains a significant challenge. To address this intriguing issue, we demonstrate that combining DNA with suitable cationic surfactants, followed by dehydration, can be a simple generic scheme for producing these solvent‐free DNA fluid systems. In the anhydrous smectic liquid crystalline phase, DNA sublayers are intercalated between aliphatic hydrocarbon sublayers. The lengths of the DNA and surfactant are found to be extremely important in tuning the physical properties of the fluids. Stable liquid‐crystalline and liquid phases are obtained in the ?20 °C to 200 °C temperature range without thermal degradation of the DNA. Thus, a new type of DNA‐based soft biomaterial has been achieved, which will promote the study and application of DNA in a much broader context. 相似文献
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