A Simple Assay for Quality Binders to Cucurbiturils

Abstract

A new approach towards the rapid identification of quality binders to cucurbiturils--those that combine high affinity with high selectivity for a particular homologue--was developed. The assay exploits macrocycle-specific optical fingerprints (colorimetric or fluorimetric) of carefully selected indicators dyes. The screening of a guest library revealed known (e.g., adamantane derivatives) and new (e.g., terpenes) quality binders. The predictive power of the assay was underpinned by the modeling of the involved thermodynamic equilibria.

Triple Emission from p‐Dimethylaminobenzonitrile–Cucurbit[8]uril Triggers the Elusive Excimer Emission

“…The observation of a third emission band from DMABN encapsulated inside the CB8 cavity constitutes a completely new photophysical aspect for this famous chromophore. [50] Experimental Section Absorption spectra of the samples were recorded from solutions in 1 cm quartz cuvettes on a Shimadzu UV-160 A or a Varian Cary 4000 UV/Vis spectrophotometer. The excimer emission displays a sizeable quantum yield, between those of the LE and ICT states, which has implications for previous photophysical analyses in which an excimer has been invoked as a nonfluorescent (dark) species.…”

Chemical Sensors Based on Cucurbit[n]uril Macrocycles

“…The host CB8 forms 1 : 1 complexes with a wide range of natural and artificial steroid hormones and drugs, [42] with terpenes, [103,104] with a range of metal complexes such as ferrocene, [105,106] and with adamantane-based guests such as memantine, [13,17,33,102] see Tables 4 and S2. Moreover, the group of Kim discovered that CB8 uniquely forms 2 : 1 and 1 : 1 : 1 ternary complexes with two aromatic guests, which became the cornerstone of most CB8-based applications.…”

“…It is a particular benefit of the IDA format that no covalent functionalisation of CBn is required (which is possible but often cumbersome). [103] A CB8-based, ratiometric Förster resonance energy transfer (FRET) IDA was developed by Brunsveld and co-workers, featuring green fluorescent protein (GFP) and yellow fluorescent proteins (YFP), both possessing a genetically incorporated N-terminal Phe-Gly-Gly moiety as the recognition motif for CB8. [236] Some noteworthy indicator dyes for CB7 are acridine orange (AO), proflavine (PF), berberine (BC), 4',6diamidino-2-phenylindole (DAPI), methylene blue (MB) and N,N-dimethylaminophenyltropylium (DMAT), see Table 6 and references therein.…”

A supramolecular keypad lock

“…22,23 Cucurbiturils have drawn much attention for their very high binding constants of cationic guests (up to 10 17 M À1 ) 24 and their supramolecular application potential with a strong focus on biological and pharmacological contexts, and analytical problems is beginning to reveal. [25][26][27][28][29][30][31][32][33][34][35] In the present work we take advantage of the specific complexation properties of the CB8 macrocycle. Unlike the smaller homologues CB6 and CB7, that commonly offer space for only one guest molecule, the larger CB8 often accommodates two guests and the resulting complexes may feature new emission properties (e.g., excimer fluorescence) or lead to fluorescence self-quenching.…”

“…Unlike the smaller homologues CB6 and CB7, that commonly offer space for only one guest molecule, the larger CB8 often accommodates two guests and the resulting complexes may feature new emission properties (e.g., excimer fluorescence) or lead to fluorescence self-quenching. [35][36][37][38] Additionally, the resulting pre-organization of the two guests may facilitate intracomplex photoreactions that would not happen at the dilute concentrations of the free dye molecules. [38][39][40] In a wider context, host-templated photodimerizations have been used in the design of photoswitchable supramolecular polymers.…”