Selective recognition of ATP over phosphorylated molecules in aqueous media by urea-based arene ruthenium metalla-rectangle

• Selective recognition of ATP over phosphorylated molecules in water • Synthesis and characterization of urea-based arene ruthenium metalla-rectangles • Encapsulation of fluorescein to generate fluorescent indicator displacement assays • Different interactions between fluorescein and the metalla-rectangles Selective recognition of biomolecules is of paramount importance in medicine, biotechnology, and cellular biology. Adenosine triphosphate (ATP), the universal energy currency of living systems, represents a valuable analytical target in sensing technology. However, discriminating ATP from its closely related analogues (ADP, AMP) remains a challenge. Herein, we report the synthesis of two arene ruthenium metalla-rectangles incorporating urea-based units. These water-stable assemblies are obtained from the dinuclear complex [Ru 2 ( p -cymene) 2 {bis(2-hydroxyethyl)oxamidate}Cl 2 ] and the bipyridyl connectors 1,1′-(1,4-phenylene)bis{3-(pyridin-4-yl)urea} (PPU) and 1,1′-(naphthalene-1,5-diyl)bis{3-(pyridin-4-yl)urea} (NPU) in the presence of silver triflate. Both metalla-rectangles are isolated as triflate salts, with the formula [Ru 4 ( p -cymene) 4 {bis(2-hydroxyethyl)oxamidate} 2 (PPU) 2 ](CF 3 SO 3 ) 4 (MRPPU) and [Ru 4 ( p -cymene) 4 {bis(2-hydroxyethyl)ethanediamide} 2 (NPU) 2 ](CF 3 SO 3 ) 4 (MRNPU), respectively. Both metalla-rectangles can interact with fluorescein (FLU) to form weakly-fluorescent host-guest systems, resulting in discrete fluorescent indicator displacement assays (FIDA). The MRPPU rectangle shows in buffered aqueous solution a selective ATP recognition over purine nucleotides, as opposed to MRNPU, with an affinity of 2.4 × 10 4 M -1 and a detection limit of 22.0 μM. The dissimilar response of these two metalla-rectangles is rationalized from their molecular design, suggesting distinct binding interactions with ATP.