Non-covalent self assembly controls the relaxivity of magnetically active guests

Abstract

The relaxivity of a magnetically responsive Gd complex can be controlled by non-covalent molecular recognition with a water-soluble deep cavitand. Lowered relaxivity is conferred by a self-assembled micellar “off state”, and the contrast can be regenerated by addition of a superior guest.

Role of non-covalent interactions in three copper(II) 5-chloro-2-nitrobenzoate complexes with N-donor ligands: Syntheses, characterization and packing analyses of trans-[Cu(β-pic)2(H2O)2(5-chloro-2-nitrobenzoate)2], trans-[Cu(γ-pic)2(5-chloro-2-nitrobenzoate)2] and [trans-Cu(en)2(H2O)2](5-chloro-2-nitrobenzoate)2·2H2O

“…The area of crystal engineering that deals with this concept as one of the important central themes have advanced exponentially in recent years [1][2][3]. The understanding that the molecular aggregation can be controlled to a large extent by certain groups of atoms (i.e., functional groups) which interact strongly by non-covalent interactions has led to the identification of number of reliable and robust supramolecular synthons.…”

A (Fluoroalkyl)Guanidine Modulates the Relaxivity of a Phosphonate-Containing T 1 -Shortening Contrast Agent

“…[3] This new class of agents can adjust their contrast enhancement in response to specific stimuli, including enzymes,4] metal ions,5] light,6] anions,7] pH,8] temperature,9] dioxygen,10] various biomolecules,11] or even events that trigger self-assembly. [12] Some stimuli (e.g. enzymes) covalently modify the chemical structure of the contrast agents such that the changes in contrast behavior are irreversible.…”

Selective Heavy Element Sensing with a Simple Host–Guest Fluorescent Array

“…Fluorescence Sensor Array with Metals. In general, the fluorescence assay was carried out by mixing 10 μL of guest 4 (30 μM) or guest 5 (15 μM), 10 μL of the cavitand (40 ) were first prepared in DI water with a concentration of 1 mM and then spiked into tap water sample with a final concentration of 20 μM. Other salts were also prepared and added the same way with a final concentration of 20 μM, respectively.…”

“…Here we offer an alternative strategy: instead of applying optical sensors that only use “single-mode” detection, i.e., coordination of the metal to a specific ligand, and monitoring the change in emission of an appended fluorophore, one can exploit a series of host–fluorophore complexes that are affected by the presence of small amounts of metal ions in aqueous solution in different ways. The sensing candidates are shown in Figure : the hosts are water-soluble deep cavitands, molecules that display a defined cavity capable of binding suitably sized and charged species in aqueous solution. − By varying the charge and H-bonding abilities at the upper rim while maintaining the internal cavity, selective host–guest interactions can be enhanced, and pH-responsive recognition is possible. , The molecular recognition properties of cavitands 1 – 3 are affected by numerous factors, including salt concentration and type, pH, and the presence of surfactants. These subtle changes in environment can alter the binding affinity of fluorescent guests in the hosts, giving a simple optical readout of affinity changes.…”