A spirooxazine derivative,
PheSPO
(3,3-dimethyl-1-phenethylspiro[indoline-2,3′-naphtho[2,1-
b
][1,4]oxazine]), as a dual-sensing probe for Cu
2+
and Fe
3+
was synthesized, and its structure was confirmed
by
1
H NMR,
13
C NMR, HRMS, and single-crystal
X-ray diffraction. The results reveal that the
PheSPO
probe is selective to both Cu
2+
and Fe
3+
through
distinct colorimetric responses in acetonitrile. The sensing performance
of
PheSPO
toward Cu
2+
was investigated, and
upon addition of Cu
2+
, an instant change in color from
colorless to bright yellow with a strong absorption band at 467 nm
was observed. Due to a dual-sensing behavior,
PheSPO
also
exhibits a unique response toward Fe
3+
that can be discovered
from a color change from colorless to red at an absorption wavelength
of 514 nm. Based on spectroscopic analyses and density functional
theory calculations, the 1:1 stoichiometric complexation of
PheSPO
with the targeted metal ions was proposed and the binding
constants of 1.95 × 10
3
M
–1
for
Cu
2+
and 1.29 × 10
3
M
–1
for Fe
3+
were obtained. In addition, the detection limits
of
PheSPO
for Cu
2+
and Fe
3+
were
0.94 and 2.01 μM, respectively. To verify its applicability
in real samples,
PheSPO
was further explored for quantitative
determination of both Cu
2+
and Fe
3+
in spiked
drinking water. The results showed that the recoveries of Cu
2+
and Fe
3+
examined using the
PheSPO
probe
were found comparable to those obtained from atomic absorption spectroscopy.
Moreover, the
PheSPO
strip test was developed, and its
utilization for qualitative detection of Fe
3+
in real rice
samples was demonstrated.