Cooperative anion binding and electrochemical sensing by modular podands

Abstract

A series of podands based on two or three hydrogen bonding ''arms'' situated in mutually ortho, meta, or para relationships about an aryl core have been prepared, and their affinities for simple inorganic anions were measured. Of the two-arm hosts the meta compound and to a lesser extent the ortho host exhibit a cooperative anion binding effect. The two arms function essentially independently in the para derivative. The mutually meta three-arm host shows dramatically enhanced cooperative binding. Conformational changes within the meta two-arm host result in significantly enhanced electrochemical anion sensing compared with the more conformationally rigid three-arm host.

Rim, Side Arms, and Cavity: Three Sites for the Recognition of Anions by Tetraazolium Resorcinarene Cavitands

“…The participation of aryl CÀHb onds in the recognition of anionsi s rather unusual, [15] although the earliest examples were reported in 2002. [16] In line with this finding, the molecular electrostatic potentialo ft he cavitand shows that the positive charge of the molecule is widely distributed throught he arms of the cavitand ( Figure S56 in the Supporting Information). For cavitand 3 4 + (see Figures S53-S55 and the movies provided in the Supplementary Information), chloride interacts with the sidearm region, whereas the interaction at the rim occasionally takes place with the CH 3 substituents of two adjacent arms.…”

“…The other is on the side of the cavitand, where the anions simultaneously interact with the phenylene C−H bonds of adjacent benzoimidazolium fragments and with the resorcinarene aromatic C−H bond, which points toward the cationic side of the molecule. The participation of aryl C−H bonds in the recognition of anions is rather unusual, although the earliest examples were reported in 2002 . In line with this finding, the molecular electrostatic potential of the cavitand shows that the positive charge of the molecule is widely distributed through the arms of the cavitand (Figure S56 in the Supporting Information).…”

A Couple of Tripodal and Dipodal Fluorescent Sensors for Sequential “On‐Off‐On” Response to Cu2+ and ATP/ADP Recognition in Aqueous Solution

“…Substituted benzene is one of the widely utilized cores for tripodal hosts design . Steed and coworkers have widely investigated the anion‐binding behavior of receptors centered around a substituted benzene with three functionalized arms, which exhibit great binding ability for halide ion by the formation of a binding (“3‐up” or “cone”) conformation . Besides that, tris (2‐amino‐ethyl) amine (tren) is another most used scaffold for the design of three‐dimensional receptors.…”

Radical‐Cation Dimerization Overwhelms Inclusion in [n]Pseudorotaxanes

“…[21,22] CB7, in particular, has drawn much attention because of its high solubility in water. [21] CB7 has a hydrophobic internal cavity that measures 7.3 in diameter and 9.1 in height [25] and can accommodate guest substrates [21,[26][27][28] such as imidazoles, [22,29,30] stilbenes, [31][32] viologens, [32][33][34][35][36][37][38] acridiziniums, [39] pyridine/pyridiniums, [40][41] adamantanes, [28] naphthalenes, [42] and ferrocenes, [43][44] to name but a few.…”