Luminescent Materials Laboratory, DB, Università di Verona, and INSTM, UdR Verona, Strada Le Grazie 15, 37134 Verona, Italy.
Dalton Trans. 2021 Apr 7;50(13):4700-4712. doi: 10.1039/d1dt00511a. Epub 2021 Mar 17.
A neutral Eu(iii) complex containing the S,S enantiomer of isoQC3A ligand (isoQC3A = N-isoquinolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) was synthesized and characterized. The complex was spectroscopically investigated and the results compared with those obtained for the similar bis-anionic ligand bisoQcd (bisoQcd = N,N'-bis(2-isoquinolinmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate). Both Eu(iii)-complexes show similar binding constants upon titration with the main analytes contained in interstitial extracellular fluid (i.e. hydrogen carbonate, serum albumin and citrate). However, the analyte affinity is accompanied by different enhancements of the Eu(iii) intrinsic quantum yield (QY). Structures and hydration numbers of the complexes are determined by luminescence decay measurements and DFT calculations. The QYs as well as the binding constants of the individual adducts of the complexes with hydrogen carbonate, bovine serum albumin (BSA) and citrate are determined. The study of the Eu(iii) emission upon the systematic variation of one analyte in a complex mixture has been carried out to predict the performance of the luminescent sensor in conditions close to the real extracellular environment. Both Eu(iii) complexes can detect citrate at extracellular concentrations up to 500 μM, even at millimolar concentrations of the other interfering species. In the case of the Eu(bisoQcd)OTf complex, an increase of 23% of the Eu(iii) luminescence intensity at 615 nm upon addition of 0.3 mM of citrate was recorded. This feature makes the latter complex a viable probe for luminescence analysis of citrate in a complex matrix.
合成并表征了一种含有 S,S 对映异构体的 isoQC3A 配体（isoQC3A = N-异喹啉基-N,N',N'-反式-1,2-环己二胺三乙酸）的中性 Eu(iii) 配合物。对配合物进行了光谱研究，并将结果与类似的双阴离子配体 bisoQcd（bisoQcd = N,N'-双（2-异喹啉甲基）-反式-1,2-二氨基环己烷 N,N'-二乙酸酯）的结果进行了比较。Eu(iii)-配合物与间质细胞外液（即碳酸氢盐、血清白蛋白和柠檬酸盐）中的主要分析物滴定时显示出相似的结合常数。然而，分析物亲和力伴随着 Eu(iii)本征量子产率（QY）的不同增强。通过荧光衰减测量和 DFT 计算确定了配合物的结构和水合数。还确定了配合物与碳酸氢盐、牛血清白蛋白（BSA）和柠檬酸盐的各个加合物的 QY 和结合常数。研究了在复杂混合物中系统改变一种分析物时 Eu(iii)的发射，以预测在接近实际细胞外环境的条件下发光传感器的性能。两种 Eu(iii)配合物都可以在细胞外浓度高达 500 μM 的条件下检测到柠檬酸盐，即使在其他干扰物质的毫摩尔浓度下也是如此。在 Eu(bisoQcd)OTf 配合物的情况下，在添加 0.3 mM 柠檬酸盐时，记录到 615nm 处 Eu(iii)荧光强度增加了 23%。这一特性使后者的配合物成为复杂基质中柠檬酸盐发光分析的可行探针。
