1 research outputs found
Dinuclear Zinc(II) Macrocyclic Complex as Receptor for Selective Fluorescence Sensing of Pyrophosphate
A new
diethylenetriamine-derived macrocycle known as L, bearing
2-methylquinoline arms and containing <i>m</i>-xylyl spacers,
was prepared in good yield by a one-pot [2 + 2] Schiff base condensation
procedure, followed by reduction with sodium borohydride. Up to now
this is the first hexaazamacrocycle with appended fluorophore units.
Single-crystal X-ray diffraction determination of the dinuclear zinc(II)
complex of L showed that metal centers are located at about 7.20(2)
Å from one another. This complex exhibits only weak fluorescence
in aqueous solution, but the addition of 1 equiv of pyrophosphate
(PPi) caused a 21-fold enhancement of the fluorescence
intensity. The sensor response is linear up to a value of 10 μM
HPPi<sup>3–</sup> and has a detection limit of 300
nM. The receptor behaves as a highly selective sensor for pyrophosphate
as other anions, including phosphate, phenylphosphate (PhP), adenosine
monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate
(ATP), failed to induce any fluorescence change and practically do
not affect the fluorescence intensity of the sensor in the presence
of HPPi<sup>3–</sup>. Competition titrations carried
out in aqueous solution at pH 7.4 [in 20 mM 3-(<i>N</i>-morpholino)propanesulfonic
acid (MOPS) buffer] by spectrofluorometry revealed a high association
constant value of 6.22 log units for binding of PPi by
the dinuclear zinc(II) receptor, one of the highest reported values
for colorimetric/fluorometric sensors able to work under real aqueous
physiological conditions, while association constant values for binding
of the other phosphorylated substrates are in the 5.51–4.03
log unit range