Publication details

Glycoluril-Derived Molecular Clips are Potent and Selective Receptors for Cationic Dyes in Water

Authors

SHE Nengfang MONCELET Damien GILBERG Laura LU Xiaoyong ŠINDELÁŘ Vladimír BRIKEN Volker ISAACS Lyle

Year of publication 2016
Type Article in Periodical
Magazine / Source Chemistry - A European Journal
MU Faculty or unit

Faculty of Science

Citation
Doi http://dx.doi.org/10.1002/chem.201601796
Field Organic chemistry
Keywords cation-pi interactions; dyes; glycoluril; hydrophobic effects; molecular clip
Description Molecular clip 1 remains monomeric in water and engages in host-guest recognition processes with suitable guests. We report the K-a values for 32 1.guest complexes measured by H-1 NMR, UV/Vis, and fluorescence titrations. The cavity of 1 is shaped by aromatic surfaces of negative electrostatic potential and therefore displays high affinity and selectivity for planar and cationic aromatic guests that distinguishes it from CB[n] receptors that prefer aliphatic over aromatic guests. Electrostatic effects play a dominant role in the recognition process whereby ion-dipole interactions may occur between ammonium ions and the C=O groups of 1, between the SO3- groups of 1 and pendant cationic groups on the guest, and within the cavity of 1 by cation-pi interactions. Host 1 displays a high affinity toward dicationic guests with large planar aromatic surfaces (e.g. naphthalene diimide NDI + and perylene diimide PDI +) and cationic dyes derived from acridine (e.g. methylene blue and azure A). The critical importance of cation-pi interactions was ascertained by a comparison of analogous neutral and cationic guests (e.g. methylene violet vs. methylene blue; quinoline vs. N-methylquinolinium; acridine vs. N-methylacridinium; neutral red vs. neutral red H+) the affinities of which differ by up to 380-fold. We demonstrate that the high affinity of 1 toward methylene blue (K-a = 3.92 x 10(7) M-1; K-d = 25 nm) allows for the selective sequestration and destaining of U87 cells stained with methylene blue.
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