Ponce Gonzalez J, Edgar M, Elsegood MRJ, Weaver GW (2011) Synthesis of fluorinated fused benzofurans and benzothiophenes: Smiles-type rearrangement and cyclisation of perfluoro(het)aryl ethers and sulfides, Org. Biomol. Chem.9pp. 2294-2305-2294-2305 The Royal Society of Chemistry
Lithium-bromine exchange in 2-bromophenyl perfluoroaryl ethers or sulfides affords fused fluorinated benzofurans or benzothiophenes respectively by SNAr substitution of the adjacent fluorine in the perfluoroaryl substituent. The structures of the new compounds were confirmed by NMR spectroscopy and single crystal X-ray diffraction analysis. In the case of 2-bromophenyl tetrafluoropyrid-4-yl ether, lithiation promoted a Smiles-type rearrangement which led to formation of 4-(2-hydroxyphenyl)tetrafluoropyridine, for which the structure was confirmed by X-ray crystallography.
Ponce-González J, Whelligan DK, Wang L, Bance-Soualhi R, Wang Y, Peng Y, Peng H, Apperley DC, Sarode HN, Pandey TP, Divekar AG, Seifert S, Herring AM, Zhuang L, Varcoe J (2016) High performance aliphatic-heterocyclic benzyl-quaternary ammonium radiation-grafted anion-exchange membranes,Energy and Environmental Science9(12)pp. 3724-3735
Anion-exchange membranes (AEM) containing saturated-heterocyclic benzyl-quaternary ammonium (QA) groups
synthesised by radiation-grafting onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films are reported. The relative
properties of these AEMs are compared with the benchmark radiation-grafted ETFE-g-poly(vinylbenzyltrimethylammonium)
AEM. Two AEMs containing heterocyclic-QA head groups were down-selected with higher relative stabilities in aqueous KOH
(1 mol dm-3) at 80°C (compared to the benchmark): these 100 ¼m thick (fully hydrated) ETFE-g-poly(vinylbenzyl-Nmethylpiperidinium)-
and ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEMs had as-synthesised ion-exchange
capacities (IEC) of 1.64 and 1.66 mmol g-1, respectively, which reduced to 1.36 mmol dm-3 (ca. 17 ? 18% loss of IEC) after
alkali ageing (the benchmark AEM showed 30% loss of IEC under the same conditions). These down-selected AEMs exhibited
as-synthesised Cl- ion conductivities of 49 and 52 mS cm-1, respectively, at 90°C in a 95% relative humidity atmosphere, while
the OH- forms exhibited conductivities of 138 and 159 mS cm-1, respectively, at 80°C in a 95% relative humidity atmosphere.
The ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEM produced the highest performances when tested as
catalyst coated membranes in H2/O2 alkaline polymer electrolyte fuel cells at 60°C with PtRu/C anodes, Pt/C cathodes, and
a polysulfone ionomer: the 100 ¼m thick variant (synthesised from 50 ¼m thick ETFE) yielded peak power densities of 800
and 630 mW cm-2 (with and without 0.1 MPa back pressurisation, respectively), while a 52 ¼m thick variant (synthesised
from 25 ¼m thick ETFE) yielded 980 and 800 mW cm-2 under the same conditions. From these results, we make the
recommendation that developers of AEMs, especially pendent benzyl-QA types, should consider the benzyl-Nmethylpyrrolidinium
head-group as an improvement to the current de facto benchmark benzyltrimethylammonium headgroup.
A pentanuclear M5L6 coordination cage is self-assembled in solution from a rigid linear heteroditopic phen-tpy ligand and an iron (ii) salt.
Fast shuttling motions in solution have been observed by cyclic voltammetry in a CuI/II-based  rotaxane. In the reported system, the different coordination preferences of both copper oxidation states are exploited to promote the electrochemically-triggered gliding of the ring from a tetra to a pentacoordinated site and vice versa. The thread of this rotaxane consists of a tridentate 2,2[prime or minute]:6[prime or minute],2[prime or minute][prime or minute]-terpyridine chelating unit directly bonded through its 5-position to the 3-position of the bidentate 1,10-phenanthroline unit. This distribution reduces to a minimum the distance between the two coordination sites and lessens the congestion around the tetrahedral environment. These two factors have been demonstrated to highly increase the kinetics of the switching process. In addition, the electrochemical experiments carried out in different solvent mixtures evidenced the influence of the solvent on the shuttling mechanism.
The present work aims to give insight into the effect that metal coordination has on the room-temperature conductance of molecular wires. For that purpose, we have designed a family of rigid, highly conductive ligands functionalized with different terminations (acetylthiols, pyridines, and ethynyl groups), in which the conformational changes induced by metal coordination are negligible. The single-molecule conductance features of this series of molecular wires and their corresponding Cu(I) complexes have been measured in break-junction setups at room temperature. Experimental and theoretical data show that no matter the anchoring group, in all cases metal coordination leads to a shift toward lower energies of the ligand energy levels and a reduction of the HOMO?LUMO gap. However, electron-transport measurements carried out at room temperature revealed a variable metal coordination effect depending on the anchoring group: upon metal coordination, the molecular conductance of thiol and ethynyl derivatives decreased, whereas that of pyridine derivatives increased. These differences reside on the molecular levels implied in the conduction. According to quantum-mechanical calculations based on density functional theory methods, the ligand frontier orbital lying closer to the Fermi energy of the leads differs depending on the anchoring group. Thereby, the effect of metal coordination on molecular conductance observed for each anchoring could be explained in terms of the different energy alignments of the molecular orbitals within the gold Fermi level.
Zheng Y, Ash U, Pandey R, Ozioko A, Ponce Julia, Handl M, Weissbach T, Varcoe John, Holdcroft S, Liberatore M, Hiesgen R, Dekel D (2018) Water Uptake Study of Anion Exchange Membranes,Macromolecules51(9)pp. 3264-3278
American Chemical Society
Anion exchange membrane fuel cells (AEMFCs) have attracted extensive attention
in the recent years, primarily due to the distinct advantage potentials they have over the mainstream
proton exchange membrane fuel cells. The anion exchange membrane (AEM) is the key
component of AEMFC systems. Because of the unique characteristics of water management in
AEMFCs, understanding the water mobility through AEMs is key for this technology, as it
significantly affects (and limits) overall cell performances. This work presents a study of the
equilibrium state and kinetics of water uptake (WU) for AEMs exposed to vapor source H2O. We
investigate different AEMs that exhibit diverse water uptake behaviors. AEMs containing different
backbones (fluorinated and hydrocarbon-based backbones) and different functional groups
(various cations as part of the backbone or as pendant groups) were studied. Equilibrium WU
isotherms are measured and fitted by the Park model. The influence of relative humidity and
temperature is also studied for both equilibrium and dynamic WU. A characteristic time constant is
used to describe WU kinetics during the H2O sorption process. To the best of our knowledge, this
is the first time that WU kinetics has been thoroughly investigated on AEMs containing different backbones and cationic
functional groups. The method and analysis described in this work provide critical insights to assist with the design of the nextgeneration
anion conducting polymer electrolytes and membranes for use in advanced high-performance AEMFCs.