Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, P. R. China.
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
Chemistry. 2016 Oct 17;22(43):15270-15279. doi: 10.1002/chem.201601796. Epub 2016 Aug 5.
Molecular clip 1 remains monomeric in water and engages in host-guest recognition processes with suitable guests. We report the K values for 32 1⋅guest complexes measured by 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 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 =3.92×10 m ; K =25 nm) allows for the selective sequestration and destaining of U87 cells stained with methylene blue.
分子夹 1 在水中保持单体状态，并与合适的客体发生主体-客体识别过程。我们报告了通过 H-NMR、UV/Vis 和荧光滴定测量的 32 个 1⋅客体配合物的 K 值。1 的空腔由带负静电势的芳香表面形成，因此对平面和阳离子芳香客体具有高亲和力和选择性，这使其与偏爱脂肪族客体的 CB[n]受体区分开来。静电作用在识别过程中起主导作用，铵离子和 1 的 C=O 基团之间、1 的 SO 基团和客体上的附加阳离子基团之间以及 1 的空腔内可能发生离子-偶极相互作用。主体 1 对具有大平面芳香表面的二价阳离子客体（例如萘二酰亚胺 NDI+和苝二酰亚胺 PDI+）和衍生自吖啶的阳离子染料（例如亚甲蓝和天青 A）具有高亲和力。通过比较类似的中性和阳离子客体（例如亚甲紫与亚甲蓝；喹啉与 N-甲基喹啉鎓；吖啶与 N-甲基吖啶鎓；中性红与中性红 H ），可以确定阳离子-π 相互作用的至关重要性，它们的亲和力差异可达 380 倍。我们证明，1 对亚甲蓝（K =3.92×10 m ；K =25 nm）的高亲和力允许选择性地螯合和褪色用亚甲蓝染色的 U87 细胞。
