A Combination of Factors: Tuning the Affinity of Europium Receptors for Phosphate in Water
A Combination of Factors: Tuning the Affinity of Europium Receptors for Phosphate in Water
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DOI：
10.1021/acs.inorgchem.9b02650
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发表时间：
2019-12-02
影响因子：
4.6
通讯作者：
Pierre, Valerie C.
中科院分区：
文献类型：
--
作者：
Huang, Sheng-Yin;Qian, Michelle;Pierre, Valerie C.
虽然硬金属离子对硬阴离子的识别主要是通过直接配位实现的，但静电和氢键相互作用也在调节这种超分子受体对其靶标的亲和力方面发挥了重要作用。对于基于Eu-III-羟基吡啶酮的配合物，在开放配位周围添加一个带电基团(-NH3+、-CO2-或-SO3-)或中性氢键部分(-OH)大大影响了中性pH条件下金属受体对水中磷酸盐的亲和力。在中性水中，单一的伯铵盐使磷酸盐的第一缔合常数比其中性类似物增加2个数量级。外周酒精基团的加入也增加了受体的亲和力，但程度较小(21倍)。另一方面，含有羧酸盐或硫酸盐部分的带负电的络合物对磷酸盐的亲和力可以忽略不计。有趣的是，外围基团也影响了稀土磷酸盐受体的化学计量比。含有a-NH3+基团的络合物与磷酸盐的结合比例为1：2，而含有-OH和H(对照)的络合物均形成1：3的络合物。虽然带正电的Eu-III-Lys-HOPO对磷酸盐具有最高的K-A1，但中性Eu-III-Ser-HOPO络合物的发光强度增加更大(36倍)。值得注意的是，虽然Eu-III络合物对磷酸盐的亲和力受到单个带电基团或氢键供体的存在的显著影响，但它们对磷酸盐的选择性相对于竞争阴离子的选择性仍然不受外围基团的添加的影响。
Although recognition of hard anions by hard metal ions is primarily achieved via direct coordination, electrostatic and hydrogen-bonding interactions also play essential roles in tuning the affinity of such supramolecular receptors for their target. In the case of Eu-III hydroxypyridinone-based complexes, the addition of a single charged group (-NH3+, -CO2-, or -SO3-) or neutral hydrogen-bonding moiety (-OH) peripheral to the open coordination site substantially affects the affinity of the metal receptor for phosphate in water at neutral pH. A single primary ammonium increases the first association constant for phosphate in neutral water by 2 orders of magnitude over its neutral analogue. The addition of a peripheral alcohol group also increases the affinity of the receptor but to a lesser degree (21-fold). On the other hand, negatively charged complexes bearing either a carboxylate or sulfate moiety have negligible affinity for phosphate. Interestingly, the peripheral group also influences the stoichiometry of the lanthanide receptor for phosphate. While the complex bearing a -NH3+ group binds phosphate in a 1:2 ratio, those with -OH and H (control) both form 1:3 complexes. Although the positively charged Eu-III-Lys-HOPO has the highest K-a1 for phosphate, a greater increase in luminescence intensity (36-fold) is observed with the neutral Eu-III-Ser-HOPO complex. Notably, whereas the affinity of the Eu-III complexes for phosphate is substantially influenced by the presence of a single charged group or hydrogen-bond donor, their selectivity for phosphate over competing anions remains unaffected by the addition of the peripheral groups.