Remarkably selective, non-linear allosteric regulation of anion binding by a tetracationic calix[4]pyrrole homodimer

Abstract

A covalently coupled, dimeric tetra-cationic calix[4]pyrrolehomodimer bearing anthracene linkers displayed distinctive cooperativity and fluoride selectivity with positive allosterism. The exclusive and successive binding of fluoride anions is accompanied by large 'turn-on' fluorescence (K2/K1 = 311).

On the encapsulation and assembly of anticancer drugs in a cooperative fashion

“…3C) was also in line with the formation of ternary 1 6– ⊂ 2 2 2+ with the parabolic function peaking at [ 2 + ]/([ 1 6– ] + [ 2 + ]) ∼ 0.67 38. The positive cooperativity of α = 4 K 2 / K 1 = 112 is large and quite unusual for an artificial host 21,39. We therefore suspected that the formation of ternary 1 6– ⊂ 2 2 2+ could be accompanied by an aggregation of these bolaamphiphilic complexes so that the observed cooperativity is in part arising from the chelate (multivalent) cooperativity 18.…”

Allosteric Regulation of Unidirectional Spring-like Motion of Double-Stranded Helicates

“…The plots of the absorbance at 400 nm versus the TFA concentration displayed a sigmoidal curvature characteristic of the positive homotropic allosterism (Figure ). The Hill coefficient ( n H = 2.1 ± 0.04) and the apparent association constant (log K a = 10.0 ± 0.20 (M –2 )) were obtained from the Hill plot (Figure b; for details, see the Supporting Information). The n H value is almost equal to the maximum value identical to the number of binding sites, being reasonably consistent with the previous 1 H NMR results that showed no signal due to the monoprotonated helicate (Figure S38).…”

Supramolecular Chemistry of Anionic Dimers, Trimers, Tetramers, and Clusters

“…Receptor 88 was synthesized by condensing a bis-dipyrromethane containing a pyridinyldiamido units with acetone in the presence of BF 3 and provided a different approach to creating bis-calixpyrroles than that used previously by the groups of Ballester 130–126 and Lee. 131 Both the Ballester and Lee systems were found capable of forming bis-anion complexes. However, the available evidence leads to the conclusion that the co-bound anions do not make direct contact within the relatively large receptor cavity.…”