Supplementary information files for Impact of varying the phenylboronic acid position in macrocyclic Eu(iii) complexes on the recognition of adenosine monophosphate

Supplementary files for article Impact of varying the phenylboronic acid position in macrocyclic Eu(iii) complexes on the recognition of adenosine monophosphate

The selective recognition of anions in water by artificial receptors remains a significant research challenge. The creation of a receptor selective for adenosine monophosphate (AMP) is particularly difficult due to its similarity in structure with the more negatively charged anions, ADP and ATP. We recently developed a macrocyclic Eu(III) complex that selectively binds AMP in water, by incorporating a sterically demanding quinoline arm that inhibits coordination of commonly interfering anions such as ATP. A phenylboronic acid motif was installed within the ligand to engage the ribose sugar of AMP through reversible covalent bonds. Herein we report two new Eu(III) complexes, [Eu·oBOH₂]+ and [Eu·pBOH₂]+, to investigate the impact of varying the position of the phenylboronic acid group on the anion binding properties of the Eu(III) receptors. We found that [Eu·pBOH₂]+ showed preferential binding to AMP over ATP, but exhibits a lower level of discrimination between AMP and ADP compared with the isomeric complex [Eu·mBOH₂]+. Surprisingly, [Eu·oBOH₂]+ showed no response to anions but displayed a unique response to pH, ascribed to the direct coordination of the ortho-boronate ester to the Eu(III) centre. Finally, we present first principles computations that offer a promising approach to access the emission spectra of lanthanide complexes, aiding the design of responsive lanthanide probes with specific photophysical properties.