Phosphates Sensing: Two Polyamino-Phenolic Zinc Receptors Able to Discriminate and Signal Phosphates in Water

Abstract

Two Zn(II)-dinuclear systems were studied as receptors for phosphates; they were obtained by using the two polyamino-phenolic ligands 3,3'-bis[N,N-bis(2-aminoethyl)aminomethyl]-2,2'-dihydroxybiphenyl (L1) and 2,6-bis[N,N-bis(2-aminoethyl)aminomethyl]phenol (L2) in which the difference lies in the spacers between the two dien units, biphenol or phenol in L1 and L2, respectively. The metallo-receptors obtained are able to selectively discriminate phosphate (Pi) from pyrophosphate (PPi) and vice versa in aqueous solution in a wide range of pH (6 < pH < 10). The L1 receptor system shows selectivity toward PPi over Pi, and on the contrary the L2 system exhibits opposite selectivity. This different selectivity is ascribed to the different Zn(II)-Zn(II) distances between the two metal centers which, showing a similar coordination requirement and binding phosphate in a bridge disposition, fit in a different way with the different guests. Furthermore, NMR studies supported the model of interaction proposed between guests and receptors, highlighting that they are also able to bind biological phosphates such as G6P and ATP at physiological pH. Fluorescence studies showed that the receptor system based on L1 is able to signal the presence in solution of Pi and PPi at physiological pH; the presence of Pi is detected by a quenching of the emission, that of PPi by an enhancement of it. With the aid of an external colored sensor (PCV), the receptors were then used to produce simple signaling systems for phosphates based on the displacement method; the two chemosensors obtained are able to signal and quantify these anions at physiological pH, preserving the selectivity between phosphate and pyrophosphate and extending it to G6P and ATP.

Artificial Receptors for the Recognition of Phosphorylated Molecules

“…627 Potentiometric studies in aqueous solution (0.15 M NaCl) revealed the formation of 1:1 complexes with the receptors and both inorganic phosphate and pyrophosphate. At near-neutral pH, a strong preference was observed for pyrophosphate by 577 and for inorganic phosphate by 578 .…”

Synthesis, Antioxidant Activity and Fluorescence Properties of Novel Europium Complexes with (E)-2- or 4-hydroxy-N'-[(2-hydroxynaphthalen-1-yl)methylene]benzohydrazide Schiff Base

“…[7][8][9][10][11] Organic rare earth complexes have garnered growing interest due to their potential application as fluorescent probes, labels in biological immunoassay applications, as optical amplifiers 12,13 and as active central species in photoluminescent materials. 14,15 Due to the unique photophysical and photochemical properties of rare earths complexes which exhibit potential to be harnessed in the development of new photodynamic therapies, they offer exciting opportunities to elucidate the structural features of nucleotides such as DNA.…”

Oil|Water Interfacial Phosphate Transfer Facilitated by Boronic Acid: Observation of Unusually Fast Oil|Water Lateral Charge Transport

“…Phosphates are ubiquitous in natural waters and important analytical targets for water quality monitoring 1. Methods for phosphate detection are currently mainly based on colorimetric or conductance probes,2 luminescence probes,3, 4, 5 fluorescence lifetime,6 poly‐amino‐phenolic zinc receptors,7 or gravimetric probes 8. Electrochemical phosphate detection is difficult due to the electrochemically inert and highly hydrophilic nature of phosphate.…”