Tobey Suzanne L, Anslyn Eric V
Department of Chemistry and Biochemistry, The University of Texas, Austin, TX 78712, USA.
J Am Chem Soc. 2003 Dec 3;125(48):14807-15. doi: 10.1021/ja030507k.
The design and synthesis of receptors containing a Cu(II) binding site with appended ammonium groups (1) and guanidinium groups (2), along with thermodynamics analyses of anion binding, are reported. Both receptors 1 and 2 show high affinities (10(4) M(-1)) and selectivities for phosphate over other anions in 98:2 water:methanol at biological pH. The binding of the host-guest pairs is proposed to proceed through ion-pairing interactions between the charged functional groups on both the host and the guest. The affinities and selectivities for oxyanions were determined using UV/vis titration techniques. Additionally, thermodynamic investigations indicate that the 1:phosphate complex is primarily entropy driven, while the 2:phosphate complex displays both favorable enthalpy and entropy changes. The thermodynamic data for binding provide a picture of the roles of the host, guest, counterions, and solvent. The difference in the entropy and enthalpy driving forces for the ammonium and guanidinium containing hosts are postulated to derive primarily from differences in the solvation shell of these two groups.
本文报道了含有连接铵基（1）和胍基（2）的铜（II）结合位点的受体的设计与合成，以及阴离子结合的热力学分析。在生物pH值下，受体1和2在98:2的水:甲醇体系中对磷酸根均表现出高亲和力（10⁴ M⁻¹），且对磷酸根的选择性高于其他阴离子。主客体对的结合被认为是通过主体和客体上带电官能团之间的离子对相互作用进行的。使用紫外/可见滴定技术测定了对含氧阴离子的亲和力和选择性。此外，热力学研究表明，1:磷酸根络合物主要由熵驱动，而2:磷酸根络合物则同时显示出有利的焓变和熵变。结合的热力学数据描绘了主体、客体、抗衡离子和溶剂的作用。推测含铵基和胍基主体的熵和焓驱动力差异主要源于这两组溶剂化层的差异。
