Anion receptor chemistry

Abstract

This article looks back at advances made in anion complexation since the turn of the millennium and ahead to the application of receptors in areas such as organocatalysis and nanotechnology.

Anion receptor chemistry: highlights from 2008 and 2009

“…In the compounds containing nitro substituents (20b and 21b) a chargetransfer fluorescent state is formed resulting in quenched fluorescence. This gives rise to an ON-OFF fluorescence response for 20a and 21a, and an OFF-ON response for 20b and 21b upon the addition of acid, and the magnitude of the response depends on the nature of the acid (anion) with a larger response seen for HCl than for CF 3 COOH. Subsequent studies on derivatives of 19 containing various functionalities, revealed that the presence of electron withdrawing groups in 2,6-bis-(anilinoethynyl)pyridine bisureas in general transforms this class of compounds into ''switch on'' fluorescent chloride sensors.…”

“…22). 16 These complexes exhibit intense luminescence in the solid state and in THF solutions, which was assigned to the 3 (pp*) excited state of the acetylide ligands. The authors found that changing the urea substituent could modify the anion binding strength in THF, with electron withdrawing groups (such as -NO 2 in 22) resulting in the strongest anion binding due to the increased acidity of the urea NH groups.…”

“…The results for the 2,6-dipicolinic acid derivatives (218-221) follow the same trend as for the isophthalic acid derivatives, with the only major difference being that the CN substituted compound shows reduced activity without total suppression of transformation. Tests using 20 kb plasmids illustrate how OCH 3 and H substituted tris-arenes can dramatically enhance transformation up to 10-and 8-fold respectively, which is remarkable considering that increased plasmid size usually hinders transformation. The authors theorise that the tris-arenes bind individually to the phosphate residues of the DNA backbone, encapsulating the DNA in a hydrophobic ''coat'', which can be transported across the lipid bilayer by passive diffusion.…”

“…Substitution of the receptor with a carboxylate at the para (55a) or meta (55b) position led to the formation of self-complementary dimers ( Fig. 12), as evidenced by ESI-TOF-MS in MeCN and 1 H NMR titration studies in CDCl 3 . DFT studies highlighted the difference in geometries of the dimers depending on the position of the carboxylate group and this was shown to lead to narcissistic selfsorting behaviour where mixing of the two dimers 55a and 55b in CDCl 3 did not result in the formation of any mixed dimers, due to the higher stability of one self-complementary dimer over the other.…”

A synthetic nanomaterial for virus recognition produced by surface imprinting

“…Since the advent of supramolecular chemistry in the 1980s, considerable effort has been invested in developing molecules that possess defined, predictable recognition properties [5][6][7] . Special focus has been placed on macrocyclic molecules, which have been shown to possess remarkable recognition properties with respect to anions 8 , cations 9 and small neutral molecules 10 . However, owing to a size discrepancy between host and guest molecules that is typically one to two orders of magnitude, applications with larger targets, such as proteins 2,11,12 , are limited.…”