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Ion Pairing in Protic Ionic Liquids Probed by Far‐Infrared Spectroscopy: Effects of Solvent Polarity and Temperature 下载免费PDF全文
Dr. Koichi Fumino Verlaine Fossog Peter Stange Kai Wittler Wigbert Polet Prof. Dr. Rolf Hempelmann Prof. Dr. Ralf Ludwig 《Chemphyschem》2014,15(12):2604-2609
The cation–anion and cation–solvent interactions in solutions of the protic ionic liquid (PIL) [Et3NH][I] dissolved in solvents of different polarities are studied by means of far infrared vibrational (FIR) spectroscopy and density functional theory (DFT) calculations. The dissociation of contact ion pairs (CIPs) and the resulting formation of solvent‐separated ion pairs (SIPs) can be observed and analyzed as a function of solvent concentration, solvent polarity, and temperature. In apolar environments, the CIPs dominate for all solvent concentrations and temperatures. At high concentrations of polar solvents, SIPs are favored over CIPs. For these PIL/solvent mixtures, CIPs are reformed by increasing the temperature due to the reduced polarity of the solvent. Overall, this approach provides equilibrium constants, free energies, enthalpies, and entropies for ion‐pair formation in trialkylammonium‐containing PILs. These results have important implications for the understanding of solvation chemistry and the reactivity of ionic liquids. 相似文献
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Controlling the Subtle Energy Balance in Protic Ionic Liquids: Dispersion Forces Compete with Hydrogen Bonds 下载免费PDF全文
Dr. Koichi Fumino M. Sc. Verlaine Fossog B. Sc. Peter Stange Dr. Dietmar Paschek Prof. Dr. Rolf Hempelmann Prof. Dr. Ralf Ludwig 《Angewandte Chemie (International ed. in English)》2015,54(9):2792-2795
The properties of ionic liquids are determined by the energy‐balance between Coulomb‐interaction, hydrogen‐bonding, and dispersion forces. Out of a set of protic ionic liquids (PILs), including trialkylammonium cations and methylsulfonate and triflate anions we could detect the transfer from hydrogen‐bonding to dispersion‐dominated interaction between cation and anion in the PIL [(C6H13)3NH][CF3SO3]. The characteristic vibrational features for both ion‐pair species can be detected and assigned in the far‐infrared spectra. Our approach gives direct access to the relative strength of hydrogen‐bonding and dispersion forces in a Coulomb‐dominated system. Dispersion‐corrected density functional theory (DFT) calculations support the experimental findings. The dispersion forces could be quantified to contribute about 2.3 kJ mol?1 per additional methylene group in the alkyl chains of the ammonium cation. 相似文献
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Dr. Lena Decuyper Katarina Magdalenić Marie Verstraete Dr. Marko Jukič Dr. Izidor Sosič Dr. Eric Sauvage Dr. Ana Maria Amoroso Olivier Verlaine Prof. Dr. Bernard Joris Prof. Dr. Stanislav Gobec Prof. Dr. Matthias D'hooghe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16128-16140
Innovative monocyclic β-lactam entities create opportunities in the battle against resistant bacteria because of their PBP acylation potential, intrinsically high β-lactamase stability and compact scaffold. α-Benzylidene-substituted 3-amino-1-carboxymethyl-β-lactams were recently shown to be potent PBP inhibitors and constitute eligible anchor points for synthetic elaboration of the chemical space around the central β-lactam ring. The present study discloses a 12-step synthesis of ten α-arylmethylidenecarboxylates using a microwave-assisted Wittig olefination as the crucial reaction step. The library was designed aiming at enhanced β-lactam electrophilicity and extended electron flow after enzymatic attack. Additionally, increased β-lactamase stability and intermolecular target interaction were envisioned by tackling both the substitution pattern of the aromatic ring and the β-lactam C4-position. The significance of α-unsaturation was validated and the R39/PBP3 inhibitory potency shown to be augmented the most through decoration of the aromatic ring with electron-withdrawing groups. Furthermore, ring cleavage by representative β-lactamases was ruled out, providing new insights in the SAR landscape of monocyclic β-lactams as eligible PBP or β-lactamase inhibitors. 相似文献
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Lena Decuyper Marko Juki
Izidor Sosi
Ana Maria Amoroso Olivier Verlaine Bernard Joris Stanislav Gobec Matthias D'hooghe 《化学:亚洲杂志》2020,15(1):51-55
Monocyclic β‐lactams revive the research field on antibiotics, which are threatened by the emergence of resistant bacteria. A six‐step synthetic route was developed, providing easy access to new 3‐amino‐1‐carboxymethyl‐4‐phenyl‐β‐lactams, of which the penicillin‐binding protein (PBP) inhibitory potency was demonstrated biochemically. 相似文献
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Inside Cover: Controlling the Subtle Energy Balance in Protic Ionic Liquids: Dispersion Forces Compete with Hydrogen Bonds (Angew. Chem. Int. Ed. 9/2015) 下载免费PDF全文
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