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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Polysaccharide backbones of fungi and mushrooms are composed mainly of 1,3-linked polysaccharides. Cationic ring-opening polymerization of 1,3-anhydro-2,4,6-tri-O-(pbromobenzyl)-β-d-glucopyranose (15) takes place by triflic anhydride or silver triflate catalyst to provide stereoregular (1→3)-α-d-glucopyranans (16) with M¯n of 11 × 103 − 19 × 103 and with [α]D of +259° (Scheme III).30 After deprotection, the DP¯ n of stereoregular glucopyranans may be 40–50.
Polysaccharides
Published in Stanislaw Penczek, H. R. Kricheldorf, A. Le Borgne, N. Spassky, T. Uryu, P. Klosinski, Models of Biopolymers by Ring-Opening Polymerization, 2018
On the other hand, polymerization of the p-brornobenzyl monomer 46B demonstrates that it has considerably higher polymerizability than that of the benzyl monomer 46. In the polymerization of 46B with triflic anhydride and silver triflate as catalysts, polymers with high molecular weights, up to 31 · 103 are obtained. In addition, the stereoregularity is higher in nonpolar solvents, such as toluene and benzene, than in methylene chloride. For instance, the polymerization, which is performed with silver triflate catalyst in benzene at room temperature, affords a completely stereoregular 2,4,6-tri-O-p-bromobenzyl-(1→3)-α-d-glucopyranan with a molecular weight of 31 · 103 in 100% yield (Scheme 16).
Telechelic Polyethers by Living Polymerizations and Precise Macromolecular Engineering
Published in Sophie M. Guillaume, Handbook of Telechelic Polyesters, Polycarbonates, and Polyethers, 2017
Pierre J. Lutz, Bruno Ameduri, Frédéric Peruch
The CROP of THF has also been performed with bromopropionyl bromide in the presence of silver triflate [289, 290] or 4-hydroxy-butyl-2-bromoisobutyrate with trifluoromethanesulfonic anhydride [291]. Upon termination of the polymerization with water (or methanol), α-bromo,ω-hydroxy (or methoxy) PTHF was obtained and subsequently used as the macroinitiator for the ATRP of styrene or (meth)acrylates to yield PTHF-b-PS or PTHF-b-PMMA block copolymers. Similar block copolymers have also been obtained by reacting living PTHF with lithium bromoacetate, which was further used as a macroinitiator for free-radical polymerization (FRP) of styrene or MMA [292]. In the same way, living PTHF has been terminated with N-alkoxy pyridinium ion that photo-initiated the FRP of styrene or MMA [293]. Another approach for the synthesis of block copolymers involving PTHF segments was based on the transformation of cationic active species of THF polymerization into species able to initiate radical polymerization [294]. Miktoarm star polymers containing PTHF and polystyrene arms have also been obtained by combining CROP and ATRP methods [295,296–297]. Star-block copolymers have also been easily prepared [298,299,300–301]. Similarly, cationic active centers were transformed into active anionic centers to yield nylon 6-PTHF block copolymers [302, 303].
Fascinating interaction of the ammonium cation with [2.2.2]paracyclophane: experimental and theoretical study
Published in Molecular Physics, 2018
Emanuel Makrlík, David Sýkora, Stanislav Böhm, Magdalena Kvíčalová, Petr Vaňura
It is well known that π-prismands and certain hydrocarbon cyclophanes are capable of forming π-complexes with some small metal cations, where benzene rings act as π-donors for the respective complexes [1]. This fascinating complexation behaviour is especially effective for [2.2.2]paracyclophane and related structures [2,3]. Pierre et al. [3] have reported the preparation of the silver triflate complex of [2.2.2]paracyclophane and claimed that it was the first member of a new class of compounds; owing to the complexation properties, they proposed the name π-prismand for such hydrocarbon cyclophanes. Furthermore, Vögtle et al. [4] have shown that concave hydrocarbon cyclophanes can extract certain metal ions from an aqueous phase into a nonpolar phase. They have tested these hydrocarbons as ionophores and have shown that PVC–[2.2.2]paracyclophane membranes demonstrated remarkable sensitivity toward the univalent silver cation [4]. Recently, the first-principles model of Fermi resonance in the alkyl CH stretch region has been applied to 1,2-diphenylethane and [2.2.2]paracyclophane [5]. Finally, the role of the metal formal charge in the cation–π interactions has been evaluated with relativistic density functional theory (DFT) methods involving a versatile π-cryptating structure, namely [2.2.2]paracyclophane [6].
Coordination complexes featuring bidentate κN, κI-8-iodoquinoline
Published in Journal of Coordination Chemistry, 2021
Pramod Dhungana, Pranab K. Nandy, Anwar Hussain, James D. Hoefelmeyer
In a 20 mL vial Ag(OTf) (257 mg, 1.0 mmol) was dissolved in 5 mL of CH3CN. A solution of 8-iodoquinoline (255 mg, 1.0 mmol) in 5 mL of toluene was added to the silver triflate solution. The vial was completely wrapped with aluminum foil to block light that may lead to photoreduction of Ag(I), and the mixture was stirred overnight at room temperature. The solvent was removed in vacuo and the product was extracted with CH2Cl2. Crystals were obtained by slow evaporation of the solvent. Yield: 457 mg (89%). Melting point: 180–183 °C. Elemental analysis calculated: C 29.73%, H 1.56%, N 3.65%; found: C 29.81%, H 1.22%, N 3.71%.
Synthesis of novel Ag(I)-N-heterocyclic carbene complexes soluble in both water and dichloromethane and their antimicrobial studies
Published in Journal of Coordination Chemistry, 2019
Lamia Boubakri, Khaireddine Dridi, Abdullah Sulaiman Al-Ayed, I. Ozdemir, S. Yasar, Naceur Hamdi
Silver-N-heterocyclic carbene (Ag-NHC) complexes were first reported by Arduengo in 1993 using silver triflate (AgOTf) [29]. In 1998, Lin simplified the method of complexation of silver to NHC by in situ complexation of the carbene precursors using silver(I) oxide [30]. There have been many Ag-NHC complexes reported [6, 10, 51, 52] which use silver(I) oxide as a base to deprotonate the imidazolium proton and also as a source of silver. The formation of Ag-NHCs and their structural diversity depends largely on the source of silver and the ratio of silver reagent to the imidazolium salt or N-heterocyclic carbene ligand.