Anion receptor chemistry: highlights from 2010

Abstract

This critical review covers advances in anion complexation in the year 2010. The review covers both organic and inorganic systems and also highlights the applications to which anion receptors can be applied such as sensing, anion transport, control of molecular motion and gelation (179 references).

Azolium-based systems: application of an anion exchange resin (A- form) method and 1H NMR analysis of the charged-assisted (C–H)+•anion hydrogen bonds

“…It was then confirmed that this simple method is efficient with 1,2,3-triazolium-based ionic liquids 2·X, improving the currently operative procedures of classical counteranion exchange, e.g. 2a·BF 4 , 2a·PF 6 and 2a·CF 3 SO 3 prepared from 2a·I. Recapping the results, the anion loading of the AER (OH¯ form) with acids, ammonium salts and sodium azide was carried out in water or a hydromethanolic or CH 3 CN/H 2 O (9:1) solvent mixture according to the lipophilic nature of the anion source.…”

“…tetraphenylborate. 6 Thus, the structural study of 1a·BPh 4 ( (2)-H of the imidazolium ring. 38 As already mentioned, the use of CD 2 Cl 2 as a solvent implies minimizing solute-solvent interactions.…”

New insights into dihydrogenphosphate recognition with dirhenium(i) tricarbonyl complexes bridged by a thiourea moiety

“…Subsequent combination of 5-isothiocyanatomethyl-2,2'-bipyridine and 5-aminomethyl-2,2'-bipyridine, exploiting pyridine as both solvent and base, resulted in the ditopic ligand L1 (Scheme 1) in 73% yield, the identity of which was confirmed by 1 H NMR spectroscopy and electrospray mass spectrometry. Subsequent complexation of ligand L1 with Re(CO) 5 Br was initially attempted in toluene, but the poor solubility of the ligand resulted in the necessity to use dry DMSO, which was subsequently removed by vacuum distillation and recrystallization from hot toluene giving the product as a bright yellow solid in 62 % yield.…”

“…Studies were undertaken to screen compound L1's behaviour in the presence of a variety of common anions by 1 H NMR spectroscopy in a 50% mixture of CD 3 CN and DMSO-D 6 . This revealed that there is no change in the relative peak position of any of the observed signals, including that of the thiourea NH resonance, with the addition of up to ten equivalents of the tetrabutylammonium (TBA) salts of NO 3 − , Br − and HSO 4 − , while the addition of the corresponding chloride salt leads to a small downfield shift of the thiourea proton signal ( = 0.25 ppm with ten equivalents, Figure 2a and S9).…”

“…The selective recognition of anions has developed over the last two decades into a vibrant area of research 1 with considerable emphasis placed on the selective recognition of phosphate salts due to their prevalence in biology. 2,3 One successful approach is the use of metal-based receptors, where positive electrostatic interactions can be combined with an acidic proton to encourage hydrogen bonding, 4 and then exploit a change in the redox, photophysical or magnetic properties to create a sensor.…”