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Glycoluril‐Derived Molecular Clips are Potent and Selective Receptors for Cationic Dyes in Water
Author(s) -
She Nengfang,
Moncelet Damien,
Gilberg Laura,
Lu Xiaoyong,
Sindelar Vladimir,
Briken Volker,
Isaacs Lyle
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201601796
Subject(s) - cationic polymerization , clips , molecular tweezers , receptor , chemistry , combinatorial chemistry , pharmacology , biophysics , biochemistry , medicine , organic chemistry , biology , molecule , supramolecular chemistry , surgery
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 1 H 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 SO 3 − groups of 1 and pendant cationic groups on the guest, and within the cavity of 1 by cation–π 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–π 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 =3.92×10 7 m −1 ; K d =25 n m ) allows for the selective sequestration and destaining of U87 cells stained with methylene blue.