Perylene diimide based 'turn-on' fluorescence sensor for detection of Pd2+ in mixed aqueous media

Article abstract of DOI:10.1016/j.tet.2014.01.063

A perylene diimide (PDI) based fluorescence chemosensor (PDI-1) for Pd ²⁺ was prepared. PDI-1 showed a remarkable fluorescence enhancement (over 120-fold) in the presence of Pd²⁺ in mixed aqueous media with high selectivity and sensitivity. Moreover, the dramatically 'off-on' fluorescence response concomitantly induced the obvious color change from dark purple to brilliant pink, which could also be identified by naked eyes easily. The low limit for Pd²⁺ detection was found to be as small as 10 ^-9 mol/L. Hence, PDI-1 is a highly promising fluorescent chemosensor for the direct determination of residual Pd²⁺ in chemical medicines and environment samples.

Full text of DOI:10.1016/j.tet.2014.01.063

Tetrahedron 70 (2014) 1997e2002
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Perylene diimide based ‘turn-on’ fluorescence sensor for detection
of Pd2þ in mixed aqueous media
,
b
,
a
a
a
a,b
Hai-xia Wang a , Yue-he Lang , Hui-xuan Wang , Jing-jing Lou , Hai-ming Guo
,
*
,
Xi-you Li c
*
a School of Chemistry and Chemical Engineering, Key Laboratory of Green Chemical Media and Reactions of Ministry of Education, Henan Normal
University, Xinxiang 453007, China
b School of Environmental Science, Henan Normal University, Xinxiang 453007, China
c School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
a r t i c l e i n f o
a b s t r a c t
A perylene diimide (PDI) based fluorescence chemosensor (PDI-1) for Pd2þ was prepared. PDI-1 showed
a remarkable fluorescence enhancement (over 120-fold) in the presence of Pd2þ in mixed aqueous media
with high selectivity and sensitivity. Moreover, the dramatically ‘offeon’ fluorescence response con-
comitantly induced the obvious color change from dark purple to brilliant pink, which could also be
identified by naked eyes easily. The low limit for Pd2þ detection was found to be as small as 10ꢀ9 mol/L.
Hence, PDI-1 is a highly promising fluorescent chemosensor for the direct determination of residual Pd2þ
in chemical medicines and environment samples.
Article history:
Received 12 November 2013
Received in revised form 21 January 2014
Accepted 27 January 2014
Available online 31 January 2014
Keywords:
Perylene tetracarboxylic diimide
Ó 2014 Elsevier Ltd. All rights reserved.
Fluorescence sensor
PDI-1
Pd2þ
Turn-on
1. Introduction
electron transfer (PET), as a well-known design strategy for various
fluorescence chemosensors for metal ions,7 was scarcely employed
In recent years, fluorescent chemosensors for sensing and
monitoring heavy and transitional metal ions (HTM) are an at-
tractive field due to their high sensitivity and simplicity.1 Among
the metal ions, palladium as a rare transition metal of platinum
group metals, is widely used as catalysts in the synthesis of various
drugs and chemical products.2 However, palladium can accumulate
in vivo, bind to proteins, and other biomacromolecules leading to
degradation of DNA and disturbance of a variety of cellular pro-
in the development of fluorescence sensors for palladium. In this
regard, we are interested in construction of a new PET-based ‘turn-
on’ fluorescence chemosensors for Pd2þ
.
Perylene tetracarboxylic diimide derivatives widely used as
fluorophore with good electron accepting ability8 have generated
great interest in the field of photonic materials because of their
excellent light and thermal stabilities, high fluorescence efficiency,
and good semiconducting properties.9 Hence, PDIs are also favor-
able fluorophores for fluorescence sensors towards HTMs.7q,10 For
example, Shangguan and co-workers have reported a PDI-based
turn-on fluorescent sensor for Zn2þ and Cd2þ ions by adjusting
the pH of media (acetonitrileeHEPES buffer, 1/1, v/v).7q He and co-
workers have developed a fluorometric and colorimetric sensor for
Cu2þ by grafting PDI onto the surface of gold nanoparticles.10a Ad-
ditionally, two ‘offeon’ PDI-based fluorescence probes for para-
magnetic species Ni2þ and Fe3þ in DMF were reported in our
previous works.10b
cesses.3 The proposed maximum dietary intake of Pd is <15
mg/
dayꢀ1 per person and its threshold in drugs is 5e10 ppm.3,4 Thus, it
is necessary to develop highly selective and sensitive fluorescent
chemosensors for the quick detection of palladium species in the
living system and natural environment. Among the literature re-
ports, most of fluorescent sensors displayed high selectivity for
palladium by adopting two kinds of signaling mechanisms, in-
cluding rhodamine spirolactam-ring-opening-based process and
palladium catalyzed nonrhodamine-based chemical reaction, such
as the deprotection of propargyl ethers.5,6 However, photo-induced
Herein, three PDIs derivatives PDI-1, PDI-2, and PDI-3 were
rationally designed and synthesized for the purpose of sensing
HTMs (Scheme 1). The PDI with four substituents at the bay posi-
tions was chosen as fluorophore and di(2-pyridylmethyl)amine
(DPA) group was used as receptor owing to their powerful chelating
* Corresponding authors. E-mail addresses: hxwang5270@163.com (H.-xia
Wang), xiyouli@sdu.edu.cn (X.-you Li).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.01.063

1998
H.-xia Wang et al. / Tetrahedron 70 (2014) 1997e2002
significantly different as shown in Fig. 1. The parameters about
absorption and emission spectra of PDI-1, PDI-2, and PDI-3 de-
rivatives in different solvents at room temperature were summa-
rized in Table S1. As expected, the fluorescence from the PDI
fluorophore in PDI-1 (FF¼0.01, using N,N0-bis(normal-butyl-1,7-
bis-(tert-butylphenoxy)perylene-3,4:9,10-tetracarboxylic-diimide)
in DCM solution as reference compound,10b FF¼1) was completely
quenched due to the quick and efficient PET process from nitrogen
lone pair of DPA to PDI fluorophore. Similar fluorescence quenching
was also observed for PDI-2 (FF¼0.09). But the fluorescence
quantum yield of PDI-3 (FF¼0.5) is relative large, which indicates
that the PET process in this compound is less efficient and slow.
Scheme 1. Molecular structures and synthesis of PDI-1, PDI-2, and PDI-3.
ability to many transitional metal ions.7q,10b,11 The different linker,
including aromatic benzyl ring, N-ethyl-aniline, and saturated ethyl
groups, connected the fluorophores with DPA moieties, re-
spectively. Apparently, the expected photoinduced receptor-to-
fluorophore electron transfer (PET) can occur when DPA units are
not involved in metal ion binding, they can act as electron donors,
which quenches the fluorescence of the PDI while the fluorophores
are excited. Once the DPA units coordinated with metal ions, the
PET process between DPA and PDI would be inhibited and thus the
strong fluorescence of PDI fluorophore would be restored.
The results revealed that PDI-1 showed excellent selectivity and
sensitivity for Pd2þ ions over other competing metal ions in mixed
aqueous media (DMF/H2O, v/v, 7:1). The remarkable fluorescence
increase over 120-fold was triggered upon addition of Pd2þ, and the
low detect limit was determined to be 7.32ꢁ10ꢀ9 M, which was
Fig. 1. Fluorescence spectra of PDI-1, PDI-2, and PDI-3 in DCM solutions at room
temperature
(N,N-Bis(normal-butyl-1,7-bis-(tert-butylphenoxy)perylene-3,4:9,10-
tetracarboxylic-diimide) in DCM solution as reference compound,10b FF¼1),
lex¼540 nm, [PDI-1]¼10
mM, [PDI-2]¼10
mM, [PDI-3]¼10
mM, [Refer]¼10
mM,
sufficiently low to detect the nanomolar concentration of Pd2þ
.
lex¼540 nm, Slit: 2.5 nm, 2.5 nm.
PDI-1 was shown to be a promising fluorescent chemosensor for
the direct quantitative determination of residual palladium
(0e15 ppm) in chemicals and natural environment.
2.3. Recognition to different metal ions
The recognition behaviors of PDIs toward different metal ions
(8.0 equiv) were investigated by fluorescence and UVevis spectra.
As shown in Fig. 2, in the absence of various metal ions, PDI-1
showed no fluorescence in DMF/H2O (7/1, v/v) solution
2. Results and discussion
2.1. Synthesis
(
FF¼0.0041) due to the highly efficient PET process between DPA
The detailed synthetic procedures of these three PDI derivatives
were described in Scheme 1. N-n-Butyl-1,6,7,12-tetra(4-tert-butyl-
phenoxy)perylene-3,4:9,10-tetracarboxylic-3,4-anhydride-9,10-
imide were condensed with compound 1 and compound 2, re-
spectively, in toluene with imidazole as the base to give rise to PDI-
1 in 84% yield and PDI-2 in 80% yield. PDI-3 was synthesized by
refluxing N-n-butyl-1,6,7,12-tetra(4-tert-butyl-phenoxy)perylene-
3,4:9,10-tetracarboxylic-3,4-anhydride-9,10-imide and compound
3 in absolute ethanol to give an 82% yield. The new compounds,
PDI-1, PDI-2, and PDI-3 were fully characterized by 1H and 13C
NMR, and HR-ESI spectra.
moiety and PDI fluorophore. In the presence of Ni2þ, Hg2þ, Co2þ
,
Zn2þ, and Cd2þ, very small increase on the intensity of fluorescence
of PDI-1 was observed. In the presence of other metal ions, in-
cluding Cr3þ, Mn2þ, Fe3þ, Cu2þ, Agþ, and Pb2þ, under identical ex-
perimental conditions, the fluorescence intensity changes were
negligible. However, when Pd2þ was added, a significant emission
peak centered at around 620 nm appeared immediately. The
2.2. Absorption and fluorescence spectra of PDI-1, PDI-2, and
PDI-3
The absorption spectra of these three compounds in dichloro-
methane (DCM) showed a strong band centered around 580 nm,
which was typical for PDIs with four substituents at the bay posi-
tions.12 These results suggest that the connection of DPA groups at
the imide nitrogens through different bridges does not affect the
ground state of PDI. This is reasonable because the frontier mo-
lecular orbital knots at the imide nitrogens block the interactions
between the DPA and PDI units.9b,13 Due to the same reason, the
UVevis absorption spectra of PDI-1 showed almost negligible
changes in the presence of metal ions in their solution. However,
the fluorescence spectra of PDI-1, PDI-2, and PDI-3 in DCM were
Fig. 2. Fluorescence spectra change of PDI-1 (6.0 mM) upon addition of different metal
ions (8.0 equiv) including Cr3þ, Mn2þ, Fe3þ, Co2þ, Ni2þ, Cu2þ, Zn2þ, Agþ, Cd2þ, Hg2þ
,
Pb2þ, and Pd2þ in DMF/H2O (v/v, 7/1), lex¼540 nm, Slit: 2.5 nm; 5.0 nm.

H.-xia Wang et al. / Tetrahedron 70 (2014) 1997e2002
1999
enhancement factors (EFs) of the fluorescence of PDI-1 in the
presence of various metal ions (8.0 equiv) were shown in Fig. 3. In
the presence of Pd2þ ions, the fluorescence intensity of PDI-1 in-
creased by over 120-fold (FF¼0.52). The EFs of Ni2þ, Hg2þ, Co2þ
,
Zn2þ, and Cd2þ were 10, 7, 6, 3, and 2, respectively. PDI-1 thus
exhibits obvious ‘turn-on’ fluorescence response, and displays
a remarkably high selectivity towards Pd2þ in mixed aqueous me-
dia. But for PDI-2 and PDI-3, no distinct fluorescence response
could be observed upon the addition of various metal ions in-
cluding Pd2þ in mixed aqueous solutions (Fig. S7). The experi-
mental results indicated clearly that PDI-2 and PDI-3 had no
response and selectivity for metal ions in DMF/H2O (7/1, v/v)
solutions.
Fig. 4. Fluorescence spectra titration of PDI-1 (5.0
m
M) was measured in the presence
of different concentrations of Pd2þ in DMF/H2O (v/v, 7/1) after 30 min, lex¼540 nm,
Slit: 5.0 nm; 5.0 nm. Inset showing the color change (left) before (right) after the
addition of Pd2þ ions in 365 nm light.
palladium (II). More importantly, PDI-1 also exhibited a similar
fluorescence response with other palladium compounds including
PdCl2, Pd(PPh3)2Cl2 (Fig. 5). In the presence of Pd(PPh3)2Cl2
(8.0 equiv), relatively lower but prominent enhancement of fluo-
rescence was observed. That means the counter ions of Pd2þ does
not disturb the sensing process of PDI-1 towards Pd2þ
.
From the fluorescence titration experimental results (Fig. 6),
good liner relationship between the relative fluorescence
a
Fig. 3. Fluorescence responses of PDI-1 (6.0
(v/v, 7/1), lex¼540 nm, Slit: 2.5 nm; 5.0 nm.
mM) to various metal cations in DMF/H2O
The high selectivity of PDI-1 for Pd2þ is surprising because the
DPA moiety as cation chelating groups usually displayed high se-
lectivity towards Zn2þ, Cu2þ, Cd2þ or Ni2þ as reported in previous
literature.10b,11 For fluorescence probes, as we know, the varied
binding properties of DPA to metal ions are dependent on the flu-
orophore, linker, and experimental conditions, such as solvents.
The dramatic fluorescence increase of PDI-1 in the presence of Pd2þ
could be related to the expected PET process in it. When the ni-
trogen atom connecting directly to the phenyl linker in DPA unit
coordinated to the selected metal ions, the PET process was hin-
dered and the fluorescence of the fluorophore restored. Addition-
ally, the reported crystal structure of the complex obtained from
DPA ligand and Pd2þ revealed clearly the coordination of the aniline
N with the palladium (II).14
Fig. 5. Fluorescence intensity changes of PDI-1 (5.0 mM) in the presence of commonly
found palladium complexes (8.0 equiv) in DMF/H2O (v/v, 7/1), lex¼540 nm, Slit:
2.5 nm; 5.0 nm.
Although PDI-1 exhibited highly remarkable ‘turn-on’ fluores-
cence upon addition of Pd2þ in mixed aqueous solutions, the ab-
sorption spectra of PDI-1 and PDI-1 with different metal ions
including Pd2þ showed no obvious changes as mentioned above
(Fig. S8). These results thus suggested that addition of Pd2þ ions
induced no detectable aggregating behavior. It was worth noting
that due to the remarkable restored fluorescence, the solution of
PDI-1 with Pd2þ ions displayed obvious color change from dark
purple to brilliant pink (inset of Fig. S8), which could be identified
by naked eyes. Consequently, PDI-1 provides a visional method to
discriminate Pd2þ ions from other transitional metal ions.
2.4. Fluorescence titration and competition experiments
A fluorescence titration experiment of PDI-1 (5.0 m
M) with Pd2þ
ions was conducted in DMF/H2O (7/1, v/v) at 25 ꢂC (Fig. 4). Upon
gradual addition of Pd2þ to the solutions of PDI-1 (up to 10 equiv),
the fluorescence at around 620 nm was enhanced progressively. A
brilliant orange color of PDI-1 was clearly observed under UV lamp
(inset of Fig. 4), indicating that PDI-1 could be a promising selective
fluorescent chemosensor for the direct detection of residual
Fig. 6. Relative fluorescence intensity of PDI-1 at different concentrations of Pd2þ
(0e150
mM) added in DMF/H2O (v/v, 7/1). Inset showing a liner relationship between
the relative fluorescence intensity and the Pd2þ concentration.

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H.-xia Wang et al. / Tetrahedron 70 (2014) 1997e2002
intensity (IꢀI0) and the Pd2þ concentration in the 0e15
mM con-
centration range (R¼0.997) was obtained (inset of Fig. 6). This
provides a promising method for the quantification of Pd2þ. By
using above-mentioned fluorescence titration results, the detection
limit for Pd2þ was also calculated with the equation: detection
limit¼3
s
bi/m, where
sbi is the standard deviation of blank mea-
surements (
s
bi¼0.5984, derived from 11 measurements), m is the
slope between relative fluorescence intensity versus sample con-
centration.15 The detection limit was measured to be 7.32ꢁ10ꢀ9 M
(7.32 ppb) in DMF/H2O (v/v, 7/1). The detection limit was suffi-
ciently low to detect the nanomolar concentration of Pd2þ, which
means that PDI-1 can be used for Pd-polluted analysis in drug and
environmental settings according to the WHO specified threshold
limit for palladium content in drug chemicals [4.7ꢁ10ꢀ5 M (5 ppm)
to 9.4ꢁ10ꢀ5 M (10 ppm)].16
Fig. 8. Partial 1H NMR spectra (400 MHz) of PDI-1 in the presence of different con-
To determine the stoichiometry of the complex between PDI-1
and Pd2þ, Job’s plot was employed by using the emission intensity
centrations of Pd2þ in CDCl3. *Note: the fluorescence spectra changes of PDI-1 (5.0
mM)
in the presence of different concentrations of Pd2þ and job’s plot in chloroform were
shown in Fig. S12.
as the function of the fraction of Pd2þ 17
. The result of Job’s plot was
shown in Fig. S9. The emission intensity reached maximum when
the fraction of Pd2þ was 0.5, indicating a 1:1 stoichiometric com-
plex between PDI-1 and Pd2þ, that is, one Pd2þ ion binds to one
molecule of PDI-1. In addition, the ESI-MS analysis was conducted
to confirm the stoichiometry of the complex between PDI-1 and
Pd2þ (Fig. S10). A clear peak at m/z 1443.51, corresponding to [PDI-
1þPd2þþNaþþ2Hþ] gave solid evidence for the formation of a 1:1
complex. Based on the 1:1 binding stoichiometry and Bene-
sieHildebrand method18 (Fig. 7, the analysis results could be found
in ESI), the plot of 1/(IꢀI0) against 1/[Pd2þ] was linear, and the as-
Fig. 9. Proposed binding model of PDI-1 with Pd2þ
.
sociation constant Ka was calculated to be 2.24ꢁ104 Mꢀ1
.
The recognition process of PDI-1 was confirmed to be reversible
by adding EDTA to the solution of the metaleligand complex. The
strong fluorescence band at 620 nm was quenched completely after
adding excess amount of EDTA (Fig. 10), accompanying with dis-
tinctive color change from light pink to dark purple. The dramatic
‘oneoff’ response indicated that EDTA sequestered Pd2þ from the
metaleligand complex, and regenerated free PDI-1. Such re-
versibility is important for the fabrication of devices to sense the
Pd2þ. Thus PDI-1 could be classified as a reversible chemosensor
for Pd2þ
.
Fig. 7. BenesieHildebrand plot of PDI-1, assuming 1:1 stoichiometry for association
between PDI-1 and Pd2þ in DMF/H2O (v/v, 7/1).
To get further insight into the binding mode of chemosensor
PDI-1 with Pd2þ 1H NMR spectroscopic titration experiment was
,
performed by addition of Pd2þ to a CDCl3 solution of PDI-1. The
spectral changes are depicted in Fig. 8. Upon addition of 2.0 equiv of
Pd2þ, the Ha, Hb, Hc, and Hd protons of pyridyl rings underwent
overall large downfield shifts of 0.39, 0.20, 0.25, and 0.77 ppm,
indicating coordination of nitrogen atoms in pyridyl rings to Pd2þ
Similarly, the Hf and Hg aromatic protons of aniline unit experi-
enced downfield shifts of 0.50 and 0.58 ppm, confirming the
binding of another nitrogen atom of DPA group to Pd2þ. In addition,
.
Fig. 10. Fluorescence spectra of PDI-1 (5.0 m
M) upon gradual addition of Pd2þ in DMF/
H2O (v/v, 7/1), lex¼540 nm, Slit: 2.5 nm; 5.0 nm. EDTA was added to PDI-1þPd2þ
mixture to show the reversible binding nature of Pd2þ with PDI-1.
the distinct downfield changes (d 4.85 shifting to both 5.39 and
6.17) of chemical shifts (He) were also observed. The 1H NMR results
firmly supported that the nitrogen atoms of the aniline and pyri-
dine rings in DPA moiety were involved in the coordination with
Pd2þ, thus inducing the reduction of PET and the recovery of the
fluorescence of PDI. Taking these results into account, a binding
mode of Pd2þ with PDI-1 was proposed and shown in Fig. 9.
To further explore the selectivity of PDI-1 for Pd2þ, competition
experiments were also conducted by recording the fluorescence
spectra of PDI-1 (5.0
competing metal ions under the same concentration (Fig. 11). The
fluorescence enhancement observed for the mixtures of Pd2þ with
other metal ions was similar to that caused by Pd2þ alone. These
m
M) with Pd2þ in the presence of other

H.-xia Wang et al. / Tetrahedron 70 (2014) 1997e2002
2001
(200e300 mesh) was used as the stationary phase. All reactions
were monitored by thin layer chromatography (TLC).
20
Compound 1,10b,11e,19 compound 2,19 compound 3,
and N-n-
butyl-1,6,7,12-tetra(4-tert-butylphenoxy)perylene-3,4:9,10-tetracar
boxylic-3,4-anhydride-9,10-imide21a were prepared according to
literature procedures. The salts used in stock solutions of metal ions
were Cr(NO3)3$9H2O, MnCl2$4H2O, FeCl3$6H2O, CoCl2$6H2O,
NiCl2$6H2O, CuCl2$2H2O, Zn(NO3)2$6H2O, CdCl2$2.5H2O, AgNO3,
Pd(OAc)2, Hg(ClO4)2$3H2O, Pb(NO3)2. Other chemicals were pur-
chased from commercial sources. Solvents were of chromatographic
pure reagent.
4.2. Synthesis and characterization
Fig. 11. Fluorescence responses of PDI-1 (5.0
m
M) to Pd2þ (8.0 equiv) in the presence or
4.2.1. Synthesis of N-n-butyl,N0-[N00,N00-di(2-pyridylmethy)-aniline]-
absence of other competition metal ions (8.0 equiv). 1¼Pd2þ only, 2¼Zn2þþPd2þ
,
,
,
1,6,7,12-tetra(4-tert-butylphenoxy)perylene-3,4:9,10-tetra
ylic-3,4:9,10-tetracarboxylic-diimide21b (PDI-1). A solution of com-
pound (90 mg, 0.31 mmol), N-n-butyl-1,6,7,12-tetra(4-tert-
carbox-
3¼Hg2þþPd2þ
,
4¼Fe3þþPd2þ
,
5¼Cr3þþPd2þ
,
6¼Ni2þþPd2þ
,
7¼AgþþPd2þ
8¼Pb2þþPd2þ
,
9¼Co2þþPd2þ
,
10¼Cu2þþPd2þ
,
11¼Mn2þþPd2þ
,
12¼Cd2þþPd2þ
1
lex¼540 nm, Slit: 2.5 nm; 5.0 nm.
butylphenoxy)perylene-3,4:9,10-tetracarboxylic-3,4-anhydride-
9,10-imide (58 mg, 0.056 mmol), and imidazole (500 mg) in toluene
(25 ml) was heated to reflux for 12 h under the protection of ni-
trogen. After cooling, the solvent was removed. The residue was
purified by column chromatography on silica gel (CH3OH/CH2Cl2, 2/
100, v/v) to yield PDI-1 as violet solid (62 mg, 84%),
mp¼149e151 ꢂC. 1H NMR (400 MHz, CDCl3, 25 ꢂC, TMS):
results indicated that other competing metal ions, including Ni2þ
,
Cu2þ, Zn2þ, and Cd2þ, did not interfere with the binding between
PDI-1 and Pd2þ, and could not disturb the highly fluorogenic de-
tection of PDI-1 for Pd2þ in mixed aqueous solution.
Moreover, the response of PDI-1 for selective detection of Pd2þ
under different pH conditions was also examined. It was found that
the fluorescence intensity of PDI-1 and PDI-1 in the presence of
Pd2þ remained stable over a wide pH range of 2.5e10 (Fig. S13).
Although the fluorescence intensity of PDI-1 in a pH range of
0.5e2.5 increased slightly as shown in inset of Fig. S1, but it was
negligible in comparison with that induced by Pd2þ. The results
revealed that the fluorescence of the complex formed by PDI-1 and
Pd2þ was actually pH-independent in the pH range of 2.5e10. PDI-1
could work as a highly selective and sensitive sensor for Pd2þ in
practical use.
d
8.58e8.57 (d, J¼4 Hz, 2H, pyridine), 8.24 (s, 2H, perylene), 8.19 (s,
2H, perylene), 7.63 (t, J¼8 Hz, 2H; pyridine), 7.30e7.29 (d, J¼4 Hz,
2H, pydidine), 7.25e7.20 (m, 8H, phenyl), 7.17 (t, J¼10 Hz, 2H, pyr-
idine), 7.02e7.00 (d, J¼8 Hz, 2H, phenyl), 6.86e6.80 (m, 8H, phenyl),
6.78e6.76 (d, J¼8 Hz, 2H, phenyl), 4.85 (s, 4H, NCH2), 4.12 (t, J¼8 Hz,
2H, NCH2), 1.70e1.63 (m, 2H (CH2)3), 1.45e1.37 (m, 2H (CH2)3),
1.29e1.26 (d, J¼12 Hz, 36H, C(CH3)3), 0.94 (t, J¼8 Hz, 3H, CH3); 13
C
NMR (100 MHz, CDCl3, 25 ꢂC, TMS):
d 163.4, 163.2, 159.6, 156.0,
153.0,148.8,147.3,136.1,132.9,126.7,122.8,122.5,121.8,120.6,120.0,
119.5,119.3, 60.4, 40.4, 38.3, 34.4, 31.5, 30.2, 20.4,13.8; HR-ESI (m/z):
calcd for C86H81N5O8: [MþHþ]¼1312.6085, found: 1312.6130.
3. Conclusion
4.2.2. Synthesis of N-n-butyl,N0-(N00-2-(N000,N000-di-(2-pyridylmethyl)-
amino-ethylene)-aniline)-1,6,7,12-tetra-(4-t-butylphenoxy)-per-
ylene-3,4:9,10-tetracarboxylic-diimide (PDI-2). A solution of com-
pound 2 (142 mg, 0.37 mmol), N-n-butyl-1,6,7,12-tetra (4-tert-
butylphenoxy) perylene-3,4:9,10-tetracarboxylic-3,4-anhydride-
9,10-imide (60 mg, 0.058 mmol), and imidazole (500 mg) in toluene
(25 ml) was heated to reflux for 12 h in nitrogen atmosphere. After
cooling, the solvent was removed. The residue was purified by
column chromatography on silica gel (CH3OH/CH2 Cl2, 3/100, v/v)
to yield PDI-2 as violet solid (63 mg, 80%), mp¼113e115 ꢂC. 1H NMR
In summary, three PDI derivatives connecting with DPA moie-
ties using different linkages, PDI-1, PDI-2, and PDI-3 were pre-
pared. PDI-1 showed a remarkable fluorescence enhancement
(over 120-fold) in the presence of Pd2þ in mixed aqueous media
with high selectivity over other competing ions, which represented
the first example of PET-based ‘turn-on’ probe for Pd2þ. Moreover,
the dramatically ‘offeon’ fluorescence response concomitantly in-
duced the obvious color change from dark purple to brilliant pink,
which could also be identified by naked eyes easily. Adding EDTA in
the sensing mixture caused significant fluorescence quenching,
which indicated that PDI-1 was a reversible chemosensor. More
importantly, the low detection limit was calculated to 7.32ꢁ10ꢀ9 M,
which was sufficiently low to detect the nanomolar concentration
of Pd2þ. Hence, PDI-1 is a highly promising fluorescent chemo-
sensor for the direct quantitative determination of residual Pd2þ
(0e15 ppm) in chemical medicines and environment samples.
(400 MHz, CDCl3, 25 ꢂC, TMS):
d
8.55e8.54 (d, J¼4 Hz, 2H, pyridyl),
8.24e8.23 (d, J¼4 Hz, 4H, perylene), 7.62 (t, J¼8 Hz, 2H, pyridyl),
7.42e7.40 (d, 2H, J¼8 Hz, pyridyl), 7.26e7.21 (m, 8H, phenyl), 7.14 (t,
J¼4 Hz, 2H, pyridyl), 6.99e6.97 (d, J¼8 Hz, 2H, phenyl), 6.83 (t,
J¼10 Hz, 8H, phenyl), 6.65e6.63 (d, J¼8 Hz, 2H, phenyl), 5.02 (br s,
1H, NHCH2), 4.13 (t, J¼6 Hz, 2H, NCH2), 3.89 (s, 4H, NCH2), 3.17 (t,
J¼4 Hz, 2H, NCH2), 2.88 (t, J¼4 Hz, 2H, NCH2), 1.67e1.65 (m,
2H (CH2)3), 1.45e1.38 (m, 2H (CH2)3), 1.29e1.26 (s, 36H, C(CH3)3),
13
0.95 (t, J¼6 Hz, 3H, CH3); C NMR (100 MHz, CDCl3, 25 ꢂC, TMS):
4. Experimental section
d 164.0, 163.5, 159.2, 156.0, 155.9, 152.9, 149.1, 148.7, 147.3, 136.5,
133.0, 128.9, 126.7; 126.6, 123.9, 123.2, 122.8, 122.5, 122.2, 120.6,
120.2, 119.9, 119.8, 119.5, 119.4, 112.9, 67.1, 60.4, 52.8, 41.4, 40.4, 34.4,
31.5, 30.2, 20.4, 13.8. HR-ESI (m/z): calcd for C88H86N6O8: [MþHþ]¼
1355.6585, found: 1355.6472.
4.1. General methods and materials
NMR spectra were recorded with a 400 MHz spectrometer for
1H NMR, 100 MHz for 13C NMR. Chemical shifts
d are given in parts
per million (in CDCl3, TMS as internal standard). Absorption spectra
were measured on UV-1700 spectrophotometer. Fluorescence
emission spectra were measured on a Varian Eclipse FL0905M004
spectrofluorimeter. For column chromatography, silica gel
4.2.3. Synthesis of N-n-butyl,N0-[N00,N00-bis(2-pyridylmethyl)ethyl-
enediamine]-1,6,7,12-tetra (4-tert-butylphenoxy)perylene-3,4:9,10-
tetracarboxylic-3,4:9,10-tetracarboxylic-diimide22 (PDI-3). A solu-
tion of compound 3 (35 mg, 0.14 mmol) and N-n-butyl-1,6,7,12-

2002
H.-xia Wang et al. / Tetrahedron 70 (2014) 1997e2002
Chen, H.; Lin, W.; Yuan, L. Org. Biomol. Chem. 2013, 11, 1938e1941; (d) Jiang, J.;
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4922e4925.
tetra(4-tert-butylphenoxy) perylene-3,4:9,10-tetracarboxylic-3,4-
anhydride-9,10-imide (50 mg, 0.048 mmol) in ethanol was heated
to reflux 2 h in nitrogen atmosphere. After cooling, the solvent was
removed and the residue was purified by column chromatography
on silica gel (CH3OH/CH2Cl2, 3/100, v/v) to yield PDI-3 as violet
solid (50 mg, 82%), mp¼128e130 ꢂC. 1H NMR (400 MHz, CDCl3,
7. (a) Dissanayake, A. S.; Sandanayake, K. R. A. S. J. Chem. Soc., Chem. Commun.
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25 ꢂC, TMS):
d 8.39e8.38 (m, 2H, pyridyl), 8.23 (s, 2H, pyridyl), 8.17
(s, 2H, pyridyl), 7.30e7.31(m, 4H, perylene), 7.25e7.23 (m, 8H,
phenyl), 7.00e6.96 (m, 2H, pyridyl), 6.85e6.82 (m, 8H, phenyl), 4.31
(t, J¼8 Hz, 2H, NCH2), 4.12 (t, J¼6 Hz, 2H, NCH2), 3.85(s, 4H, NCH2),
2.88 (t, J¼8 Hz, 2H, NCH2), 1.69e1.62 (m, 2H (CH2)3), 1.42e1.37 (m,
2H (CH2)3), 1.29 (s, 36H, C(CH3)3), 0.93 (t, J¼8 Hz, 3H, CH3); 13C NMR
€
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(100 MHz, CDCl3, 25 ꢂC, TMS):
d 163.4, 163.2, 159.6, 156.0, 155.9,
153.0, 152.9, 148.8, 147.3, 147.3, 136.1, 122.8, 126.7, 122.6, 122.5,
121.8, 120.6, 120.5, 120.0, 119.9, 119.5, 119.3, 119.2, 60.4, 51.8, 40.4,
38.3, 34.4, 31.5, 30.2, 20.4, 13.8; HR-ESI (m/z): calcd for C82H81N5O8:
[MþHþ]¼1264.6163, found: 1264.6108.
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Org. Lett. 2008, 10, 4437e4440.
Acknowledgements
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Financial support from the Natural Science Foundation of China
(Grant No. 21073112 and 21272059), Science Foundation
(2011QK12), and Postdoctoral Science Foundation of Henan Normal
University are gratefully acknowledged.
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Supplementary data
Supplementary data (1H NMR and 13C NMR spectra of PDI-1,
PDI-2, and PDI-3, Table S1 and supporting figures (Fig. S7eS13))
associated with this article can be found. Supplementary data re-
lated to this article can be found at http://dx.doi.org/10.1016/
j.tet.2014.01.063.
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