Syntheses, Structures, and Anion‐Binding Properties of Two Novel Calix[2]benzo[4]pyrroles

Abstract

Calix[2]benzo[4]pyrrole m-6 and p-6, each containing two dipyrromethane moieties and two m-phenylene or p-phenylene units, respectively, were readily synthesised from pyrrole, 1,3- and 1,4-bis(1,1'-dimethylhydroxymethyl)benzene, (m-4 and p-4, respectively) and acetone. Macrocycles m-6 and p-6 were tested as receptors for a selection of anions, such as acetate, dihydrogenphosphate and fluoride. The X-ray structures of m-6 and p-6 and those of the complexes m-6F(-), m-6Cl(-) and m-6CH(3)COO(-) (with an nBu(4)N(+) counterion) were also determined.

A calixpyrrole derivative acts as a GPER antagonist: mechanisms and models

“…Calixpyrroles are macrocyclic compounds made up of pyrrole units linked by quaternary carbon atoms at their 2,5-positions ( Gale et al, 2001 ). Larger calix[ n ]pyrroles ( n >4) and hybrid calixpyrroles in which one or more pyrrole units are replaced by a benzo or other heterocyclic unit(s) are also known ( Cafeo et al, 2002 , 2007 ). Calixpyrroles have gained considerable interest owing to their ability to bind anions ( Gale et al, 1998 , 2001 ), to act as ditopic (ion-pair) receptors ( Custelcean et al, 2005 ) and to host neutral molecules ( Allen et al, 1996 ) that accept NH hydrogen bonds ( Gale, 2011 ).…”

Anion Sensing by Fluorescent Expanded Calixpyrroles

“…Figure also illustrates this point: the affinity constant of calix[2]benzo[4]pyrrole sensor S4 towards oxalate anion is an order of magnitude lower than that obtained from titration of calix[4]pyrrole congener S2 with the same analyte. This was somewhat unexpected, considering the behavior of the parent calix[2]benzo[4]pyrrole macrocycle, which displays higher affinity for larger or multiatomic anions (e.g., bromide, acetate, dihydrogen phosphate) compared to the calix[4]pyrrole . Further inspection of the affinity constants in Table shows that all of the sensors S1 – S5 , irrespective of the size of the macrocycle, display significant cross‐reactivity.…”

Synthesis and recognition properties of colorimetric anion chemosensor bearing 2,4-dinitrophenylhydrazone and indene-1,3-dione moieties

“…There is an increasing attention toward the development of colorimetric probes which have the advantage of showing easily observable color changes in the presence of target guests. Synthetic receptors for anions are usually based on macrocyclic ammonium/ guanidinium [8,9] and imidazolium [10,11], amides [12], sulfonamides [13], carbamates [14], urea/thioureas [15][16][17][18], functionalized calixarenes [19], aromatics such as pyrrole, carbazole and indole [20][21] and particularly phenylhydrazone [22], which is a kind of neutral receptor and has a simple synthetic method. Phenylhydrazone derivatives exhibit such an obvious color change when anion is added that one can use naked-eye detection without resorting to spectroscopic instrumentation [23].…”