Structural investigation of Fe(III)-salen complexes as “turn-on” fluorogenic probes for selective detection of pyrophosphate ions

• Published in: Dyes and pigments 2022-11, Vol.207, p.110708, Article 110708
• Main Authors: Hui, Eunice Y.-L., Tay, Dillon W.P., Richard, Jean-Alexandre, Pohancenikova, Zuzana, Renault, Kevin, Romieu, Anthony, Lim, Yee Hwee
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Disassembly approach; Fluorogenic probe; Pyrophosphate ion; Salen ligand; Turn-on detection
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2022.110708

In this work, we revisited the disassembly approach (also known as the Zelder's approach) recently proposed for sensing pyrophosphate (PPi) in water and based on the decomposition of metal-salen complexes. A systematic study devoted to the structural optimization of this novel class of PPi-responsive fluorogenic probes was conducted. Screening of eight different vicinal diamines (i.e., bridge of the salen ligand) combined with the use of 8-formyl-7-hydroxycoumarin (i.e., salicylaldehyde derivative) as the fluorescent reporter, has led to a set of novel and fully characterized coumarin-salen Fe(III) complexes. A series of analytical validations helped us to identify that coumarin-salen Fe(III) complexes derived from ethylenediamine and racemic 1,2-propylenediamine backbones exhibit the best and selective PPi-sensing performances (the limits of detection were estimated as 3.15 × 10−6 M and 2.81 × 10−6 M respectively). The implementation of both fluorescence time-course measurements and RP-HPLC-fluorescence analyses has enabled us to gain further insights into the activation mechanism of the disassembly-based probes. This study therefore demonstrates that the disassembly approach is a valuable strategy to achieve fluorogenic activity-based sensing of anions. [Display omitted] •A series of coumarin-salen Fe(III) complexes with various diamine bridges were synthesized.•Coumarin-salen Fe(III) complexes were used to detect pyrophosphate (PPi) through a fluorogenic disassembly approach.•Fe(III) complexes with ethylene- and 1,2-propylenediamine bridges offered the best performances.•Fe(III) complex with 1,2-propylenediamine bridge showed good selectivity and a limit of detection of 2.81 × 10-6 M.•Disassembly mechanism was deciphered by NMR and RP-HPLC-fluorescence analyses.