A naphthalimide fluorophore with efficient intramolecular PET and ICT Processes: Application in molecular logic

Article abstract of DOI:10.1039/c1ob05481c

A novel 4-amino-1,8-naphthalimide (NDI) with two different metal cation receptors connected at 4-amino or imide nitrogen positions respectively was designed and prepared. Significant internal charge transfer (ICT) as well as photoinduced electron transfer

Full text of DOI:10.1039/c1ob05481c

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PAPER
A naphthalimide fluorophore with efficient intramolecular PET and ICT
Processes: Application in molecular logic
Haixia Wang,a,b Haixia Wu,a Lin Xue,a Yan Shia and Xiyou Li*a
Received 28th March 2011, Accepted 28th April 2011
DOI: 10.1039/c1ob05481c
A novel 4-amino-1,8-naphthalimide (NDI) with two different metal cation receptors connected at
4-amino or imide nitrogen positions respectively was designed and prepared. Significant internal charge
transfer (ICT) as well as photoinduced electron transfer (PET) from the receptors to NDI is revealed by
the shifted UV-vis absorption spectra and significant fluorescence quenching. Both Zn2+ and Cu2+ can
coordinate selectively with the two cation receptors in this molecule with different affinities. The
coordination of Zn2+ with the receptor at imide nitrogen hindered the PET process and accordingly
restored the quenched fluorescence of NDI. But the coordination of Zn2+ at 4-amino position blocked
the ICT process and caused significant blue-shift on the absorption peak with the fluorescence intensity
unaffected. Similarly, coordination of Cu2+ with the receptor at imide nitrogen can block the PET
process, but can not restore the quenched fluorescence of compound 3 due to the paramagnetic
properties of Cu2+, which quench the fluorescence significantly instead. With Cu2+ and Zn2+ as two
chemical inputs and absorption or fluorescence as output, several logic gate operations, such as OR,
NOR and INHIBIT, can be achieved.
and different ligands, and thus the new molecules with prerequisite
Introduction
logic operations can be designed purposively.
Molecular logic gates have attracted a lot of research interests
In the present research, 4-amino-1,8-naphthalimide (NDI)
since the first molecular AND logic gate had been reported by
was chosen as fluoroionophore, due to its remarkable optical
de Silva and co-workers1 due to their potential applications in
properties, such as strong absorption and emission in the visible
the creation of nanometre-scale molecular devices.2 Numerous
region, high fluorescence quantum yields, high photostability and
large Stokes shift.14 The amino group at the 4 position can
play as an electron donor and cause strong ICT upon photo
excitation. Therefore, interfering on the electron donating ability
of amino group at the 4 position will cause significant changes
to the absorption and emission peaks of this compound, which
makes NDI compounds good candidates for the fluorophore
of chemical sensors based on ICT process.15 Moreover, NDIs
are also good electron acceptors due to the strong electron-
withdrawing properties of imide group. Once a receptor with
good electron-donating properties is connected to NDI, PET can
happen between receptor and fluorophore and thus a PET-based
sensor can be designed.16 NDI is therefore expected to be an ideal
model to build a molecule with both ICT and PET processes and
achieve integrated logic operations. However, related research is
scarcely reported in literature.
examples of the molecular logic gates are available in the literature
which demonstrate AND,3 OR,4 NOT,5 XOR,6 INHIBIT,7 NOR,8
XNOR,9 NAND10 logic operations independently. With careful
molecular design, the integration of distinctively different logic
gate operations in one molecule is possible. A rational design is to
decorate the molecule with multiple receptors and fluorophores,
which can multiply the information input and output channels.11
Combination of internal charge transfer (ICT) and photoinduced
electron transfer process (PET) in one fluorophore has been
proved to be an efficient way to increase output channels such
as changes in absorption or emission spectra, which are the most
common ones for the logic gate operations.12 For logic gates
with multiple inputs, high selectivity towards an outer stimulus
is especially important. Metal ions, with their inherent selectivity
for ligands, were a group of ideal candidates for chemical input
and have been used in many molecular logic gates.13 The abundant
knowledge about the ligand–metal interactions allows one to
propose exactly the selective interactions in a mixture of metal ions
Results and discussion
Molecular design and synthesis
aKey laboratory of colloid and interface chemistry, Ministry of Education,
Department of Chemistry, Shandong University, Jinan, China, 250100.
E-mail: xiyouli@sdu.edu.cn; Fax: 86-531-88564464; Tel: 86-531-88369877
We present a new NDI compound 3, which has been selectively
decorated with di(2-pyridylmethyl)amine (DPA) and N,N-di(2-
bDepartment of Chemistry, Henan Normal University, Xinxiang, China,
453007
pyridylmethyl)-N¢-(p-aminophenyl)-ethylenediamine
(EDPA)
metal cation receptors at the 4-amino and imide positions,
5436 | Org. Biomol. Chem., 2011, 9, 5436–5444
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Scheme 1 Synthesis of compound 3.
respectively. The structure and synthetic procedures are shown in
UV-vis absorption and emission spectra of 3 in the presence of
Scheme 1. The coordination of metal ions with the DPA group at
the 4 position is expected to affect the ICT from nitrogen to NDI
efficiently and induce significant changes on the absorption and
emission spectra.15l Meanwhile, the EDPA group at the imide ni-
trogen position is an electron donor, it can quench the fluorescence
of NDI efficiently by a PET process. Coordination of metal ions
at this position will reduce the electron-donating ability of EDPA
and hinder the PET process, and then restore the fluorescence
from NDI again. DPA and EDPA are expected to show different
selectivity towards different metal ions as shown in our previous
results.17 Herein, with different metal ions as chemical inputs, and
absorption and fluorescence spectra as outputs, this compound
can perform multiple logic operations at molecular level.
different metal cations
Fig. 1 shows changes of absorption spectra of compound 3 upon
addition of excess metal ions. The addition of metal ions, such
as Mn2+, Fe3+, Hg2+, Co2+, Ni2+, Cd2+, Pb2+, Cr3+ did not induce
any significant changes on the absorption spectra. However,
addition of Zn2+ produced a distinctive blue shift on the maximum
absorption peak (from 406 to 358 nm). Similar changes on the
absorption spectra were observed in the presence of Cu2+ with a
blue shift on the maximum absorption peak as high as 82 nm. The
changes of the absorption of 3 while adding Zn2+ or Cu2+ resulted in
perceived color change from yellow to colorless to the naked eyes,
as can be seen in the photograph. The significant changes on the
absorption spectra indicate directly that compound 3 coordinates
with Cu2+ and Zn2+ selectively. The changes on the absorbance of
compound 3 at 406 nm after the addition of various metal ions are
listed in Fig. 1b. It reveals clearly that compound 3 presents high
selectivity towards Zn2+ and Cu2+ over other conventional metal
ions.
Dipicolylamine is commercially available and reacts with 4-
bromo-1,8-naphthalic anhydride in methyl glycol under reflux for
4 h to give compound 2. Condensation of 2 with EDPA provides
target compound 3 in reasonable yield. All products are purified
repeatedly by column chromatograpahy on silica gel.
Following the literature, receptor DPA normally shows high
selectivity towards Cu2+, Zn2+ and Cd2+ depending on the linkage
and solvent.18 The significant changes on the absorption spectra
of compound 3 upon coordination of Zn2+ and Cu2+ revealed that
the DPA linked at 4 position participated in the coordination
with Zn2+ and Cu2+. The distinctive blue-shift on the maximum
absorption peak was caused by the reduced ICT process.
The fluorescence spectra of compound 3 in the presence of
different metal cations are shown in Fig. 2a. The fluorescence
intensities of compound 3 in the presence of different metal
ions with same concentrations are shown in Fig. 2b. It can be
found that free compound 3 shows a weak broad emission band
with the peak maximum at about 519 nm and a fluorescence
quantum yield of 10%. In the presence of Cu2+, Ni2+, Fe3+, Cr3+ and
Co2+, the fluorescence of compound 3 was quenched completely.
However, the addition of Hg2+, Cd2+, Pb2+ and Mn2+ induced
about two times magnification on the fluorescence intensity
without identical shift on peak wavelength. The most significant
UV-vis absorption and emission spectra of 3 in the absence of
different metal cations
Due to the electron-donating property of DPA at the 4 position
and the electron-withdrawing property of the imide moiety, 4-
amino-1,8-naphthalimide derivative 3 gives a “push–pull” based
excited state. This ICT character gives rise to a broad absorption
band in the visible region centered at about 410 nm (e = 12500 M-1
cm-1), which is responsible for the yellow color of the solution
in acetonitrile, and a broad emission band at about 520 nm
in acetonitrile, respectively. On the other hand, the 4-amino-
1,8-naphthalimide derivatives are usually found to be highly
emissive in organic solvents. However, as expected compound 3
only demonstrates a low quantum yield of 10%. This indicates
that the PET process from nitrogen atoms in the EDPA moiety
to the fluorophore NDI happens with high efficiency and the
excited state of naphthalimide is efficiently quenched by this PET
process.
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Fig. 1 (a) Absorption spectra of compound 3 (20 mM) in the presence
of different metal cations (4 equiv. of 3) in acetonitrile; (b) Absorption
responses of compound 3 to various metal cations, A0 represents the
absorbance of free compound 3 at 406 nm while A represents the
absorbance compound 3 in the presence of various metal ions.
Fig. 2 (a) Fluorescence spectra of compound 3 (20 mM, lex = 380 nm)
in the presence of different metal cations (4 equiv. of 3) in acetonitrile;
(b) Emission responses of compound 3 (20 mM) to various metal cations
(4 equiv. of 3), I represents the integrated fluorescence intensity between
400 nm and 710 nm after it was normalized according to the absorbance
at excitation wavelength. Subscripts m represents in the presence of metal
cations and o represents lack of metal cations.
change on the fluorescence spectra was brought by Zn2+, which
induced a remarkable enhancement on the fluorescence quantum
yield as well as a 50 nm blue-shift on the wavelength of band
maximum.
As mentioned above, the low fluorescence quantum yield of
compound 3 in solution resulted from the PET process. But the
residue of the fluorescence suggests that the PET in compound 3
is not quick enough to quench all the fluorescence of compound
3. The notable fluorescence quenching of compound 3 caused by
the presence of Cu2+, Ni2+, Fe3+, Cr3+ and Co2+ indicated that
all these metal ions indeed coordinated with compound 3. The
paramagnetic properties of these metal ions induced non-radiative
decay for the excited states of NDI and then causing the significant
fluorescence quenching. The significant change on the absorption
spectra of compound 3 revealed that Cu2+ was coordinated with the
DPA group at the 4 position. But the coordination position of Ni2+,
Fe3+, Cr3+ and Co2+ can not be determined at this stage because
these metal ions will induce significant fluorescence quenching
regardless of the coordination position. The moderate fluorescence
enhancement of compound 3 caused by the presence of Hg2+,
Cd2+, Pb2+ and Mn2+ could be attributed to the capture of these
metal ions by the EDPA receptor at the imide nitrogen position,
which hinders the PET process from EDPA to NDI and thus
releases the quenched fluorescence of NDI by the PET process.
We note that the enhanced fluorescence of compound 3 in the
presence of these metal ions does not show significant shift on
the peak maximum relative to that of free compound 3, which
indicates that the nitrogen atom at the 4 position of compound 3
did not participate in the coordination with these metal ions. The
significant fluorescence enhancement of compound 3 caused by
Zn2+ can also be attributed to the coordination of Zn2+ with EDPA
at the imide nitrogen as that observed for Hg2+, Cd2+, Pb2+ and
Mn2+. The more significant fluorescence enhancement measured
for Zn2+ than those of Hg2+, Cd2+, Pb2+ and Mn2+ may be attributed
to the high affinity of EDPA towards Zn2+ over other metal ions
as reported in the literature.18p The distinctive blue-shift on the
maximum fluorescence peak of compound 3 in the presence of
Zn2+ may result from the coordination of Zn2+ with PDA at the 4
position, too. The capture of Zn2+ by DPA that is conjugated to
the NDI core resulted in a reduced ICT process, and this process
magnified the energy gap between the HOMO and LUMO and
thus caused the blue-shift on the fluorescence peak.
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UV-vis absorption and emission spectra of 3 in the presence of
different concentration of Zn2+
detectable shift on the peak wavelength. However, in the range
of higher concentration (>1 equiv.), further enhancement of the
fluorescence intensity at 518 nm was not detected, but a slight
blue-shift was observed. The plot of the fluorescence quantum
yields of compound 3 against the concentration of Zn2+ reveals
that the changes on the fluorescence spectra are synchronous
with that of absorption spectra. We attributed the changes of the
absorption and fluorescence spectra to the two step coordination
of compound 3 with Zn2+. For the first step, Zn2+ was coordinated
to the EDPA group of compound 3 at the imide nitrogen position,
the PET process was then hindered and the fluorescence of NDI
was released. At the second step, Zn2+ began to bind with DPA at
the 4 position, the ICT process was interrupted and the blue shift in
the absorption and emission spectra was consequently observed.
According to the Benesi–Hildebrand-type analysis, the stability
constants of the complexes formed for the first and second step
reaction were estimated to be 4.21 ¥ 105 M-1 and 1.33 ¥ 105 M-1
respectively.17,19 The results indicate that the favorite position for
Zn2+ to coordinate is the EDPA at imide nitrogen position.
In order to understand the coordination of compound 3 with Zn2+
in detail, the absorption spectra of compound 3 with different
concentrations of Zn2+ were recorded as shown in Fig. 3. The
changes on the absorption spectra of compound 3 along with the
concentration increase of Zn2+ can be divided into two distinct
stages. This is revealed clearly in Fig. 3b, which shows the
plot of the absorbance of compound 3 at 409 nm against the
concentration of Zn2+. In the concentration range of 0–1.0 equiv.
of Zn2+, the absorption spectra of compound 3 had no significant
change on both intensity and peak wavelength. However, when the
concentration of Zn2+ in solution exceeded 1.0 equiv. of compound
3, the absorbance at 409 nm decreased along with the increase
of the Zn2+concentration. Meanwhile, a new absorption peak
at 358 nm formed, clearly suggesting the formation of a new
compound in the solution.
The two step coordination of compound 3 with Zn2+ was
further supported by the 1H NMR titration experiments. Fig.
1
5 shows the H NMR spectra of compound 3 in the presence
of different concentration of Zn2+ and the assignment of the
signals. It can be found that the signals of Ha, Hb, Hc, He and
Hf shifted significantly when the concentration of Zn2+ increased
from 0 to 1.0 equiv., which proved that Zn2+ was coordinated to
EDPA at imide nitrogen position. While the content of Zn2+ in
the solution exceeded 1 equiv. of compound 3, the signals of the
proton mentioned above did not shift anymore, but the signal of
Hg shifted obviously instead, which indicated that Zn2+ began to
coordinate with DPA. Further increase on the content of Zn2+
in the mixture did not induce further shifts on the signals of the
protons but sharpened the signal peaks. This suggests that the
formed coordination compounds between compound 3 and Zn2+
was stabilized by the presence of excess of Zn2+.
The absorption and emission spectra of compound 3 in the presence
of different concentration of Cu2+
As mentioned above, the absorption and emission spectra of
compound 3 showed remarkable changes upon the coordination
of Cu2+. In order to get more information on the coordination
process between Cu2+ and compound 3, the absorption spectra
of compound 3 in the presence of different concentrations of
Cu2+ were also recorded. The results are shown in Fig. 6a.
Similar to the results observed for the coordination of Zn2+, the
absorption spectra of compound 3 had no significant changes
when the content of Cu2+ in the solution was less than 1.0 equiv.
Further increase on the concentration of Cu2+ in the solution,
the absorbance of 3 at 406 nm gradually decreased following the
formation of a new band centered at 328 nm, and an isobestic point
at 356 nm was clearly observed. Upon addition of 3.5 equiv. of
Cu2+, the peak at 406 nm disappeared completely. The experiment
results mean that the coordination of compound 3 with Cu2+
in acetonitrile could also be divided into two stages like Zn2+,
as can be seen in Fig. 6b. In the concentration range of 0–1.0
equiv. of Cu2+, the absorption spectra of compound 3 had no
significant changes on both intensity and peak wavelength, which
indicates that Cu2+ is coordinated to DPA at the 4 position. Further
Fig. 3 (a) Absorption spectra of compound 3 in the presence of different
concentration of Zn2+; (b) Changes of the absorbance of compound 3 at
408 nm along with the concentration increase of Zn2+
.
The change of fluorescence spectra of compound 3 along with
concentration increase of Zn2+ can also be divided distinctively
into two stages as shown in Fig. 4. In the low concentration
range of Zn2+ (0–1 equiv.), the emission peak of compound
3 at 518 nm increased dramatically in intensity without any
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Fig. 4 Emission spectra of compound 3 (20 mM, lex = 380 nm) in the presence of Zn2+ in acetonitrile solution. (a) The concentration range of Zn2+ is
0, to 1.0; (b) The concentration range of Zn2+ is 1.0 to 8.0; (c) Photograph of compound 3 (4.5 ¥ 10-3 M) in the presence of different concentration of
Zn2+ in acetonitrile under UV light; (d) The change of fluorescence quantum yield of compound 3 along with the increasing on Zn2+ concentrations in
acetonitrile; The inset profile represents the change of fluorescence quantum yield with the concentration of zinc ions in the range of 0-20 mM.
Fig. 5 1H NMR spectra of compound 3 in CD3CN in the presence of various concentration of Zn2+
.
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Fig. 7 Emission spectra of compound 3 (20 mM) in the presence of various
concentrations of Cu2+, and photograph of 3 in the presence of different
concentration of Cu2+ in acetonitrile under UV light.
of Cu2+ as shown in Fig. 7, which indicates that the fluorescence
quenching caused by the paramagnetic property of Cu2+ dominates
the process. In the higher concentration range of Cu2+, DPA at
the 4 position conjugating to the NDI core begins to participate
in the coordination with Cu2+, and accordingly the fluorescence is
efficiently quenched with the maximum emission peak blue-shifted
simultaneously as that reported in literature.18o
Competition coordination between Cu2+ and Zn2+
Fig. 8a shows the absorption spectra of compound 3 with 3
equiv. of Zn2+ and various concentrations of Cu2+. The absorption
spectrum of compound 3 in the presence of 3 equiv. of Zn2+
produced a maximum absorption at 359 nm, which blue-shifted
for about 50 nm relative to that of pure compound 3 and can be
assigned to the coordination of Zn2+ with DPA at the 4 position.
The addition of a small amount of Cu2+, such as 0.6 equiv., induced
a mild blue shift on the absorption spectra, but with further
increase on the amount of Cu2+ in the solution, the absorption
peak at 359 nm decreased gradually, which coincided with the
growing of a new peak at 328 nm. This change can be ascribed to
the complex of DPA at the 4 position of compound 3 with Cu2+.
When the amount of Cu2+ increased to 4 equiv. of compound
3, the absorption spectra grew into typical absorption spectra of
compound 3 in the presence of pure Cu2+. This result indicates that
the Zn–DPA complex has completely transferred into Cu–DPA
complex, suggesting that DPA at the 4 position prefers to chelate
Cu2+ instead of Zn2+. The fluorescence spectra of compound 3 in
the presence of both Zn2+ and Cu2+ are shown in Fig. 8b. Addition
of 3 equiv. of Zn2+ showed a maximum emission band at about
492 nm, which blue-shifted for about 30 nm relative to that of free
compound 3, and significant fluorescence quenching. When the
amount of Cu2+ in the mixture increased to 4 equiv. of compound
3, the fluorescence was completely quenched. This result suggests
that the coordination of DPA at the 4 position with Zn2+ has
been completely edged out by the coordination with Cu2+, which
corresponds well with the results of absorption spectra.
Fig. 6 (a) Absorption spectra of compound 3 (20 mM) in acetonitrile
in the presence of various concentrations of Cu2+; (b) Changes of the
absorbance of compound 3 at 406 nm as a function of Cu2+ concentration.
addition of Cu2+ in the solution gave rise to a large blue-shift on
the absorption maximum and a clear isobestic point at 356 nm,
which reveals that Cu2+ is coordinated to DPA at the 4 position at
this concentration range.
The fluorescence spectra of compound 3 with different con-
centrations of Cu2+ are shown in Fig. 7. Unlike Zn2+, the addi-
tion of Cu2+ induced significant fluorescence quenching, which
accompanied an obvious blue-shift on the maximum emission
peak. In combination with the results of absorption experiments,
we speculate that Cu2+ could bind with both EDPA and DPA
of compound 3, but the complex formed with EDPA has higher
stability. Therefore, in the low concentration rang of Cu2+, EDPA
binds with most of the Cu2+ in solution. That is why the UV-vis
absorption spectra did not show significant change at this stage.
Because of the paramagnetic nature of Cu2+, the coordination of
Cu2+ at EDPA position will also introduce massive no-radiative
decay for the excited states of NDI. Two controversial processes
are now operating on the fluorescence intensity of compound 3.
On the one hand, the fluorescence of compound 3 is quenched
by the presence of paramagnetic Cu2+, on the other hand, the
fluorescence of NDI is enhanced by the hindered PET process
between EDPA and NDI due to the coordination of Cu2+. The
fluorescence intensity decreased in the low concentration range
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Fig. 9 Top: Absorption spectra of compound 3, 3 + 3 equiv. Zn2+, 3 + 3
equiv. Cu2+ and 3 + 3 equiv. Zn2+ + 3 equiv. Cu2+. Bottom: The truth table
for the OR/NOR logic gates (Positive logic; 0: low signal, 1: high signal).
The fluorescence spectra of compound 3 in the presence of
Zn2+or Cu2+ and both of them are shown in Fig. 10. Without
any chemical input, free compound 3 did not show any strong
emission at 492 nm. But in the presence of Zn2+, the intensity of
the fluorescence at 492 nm increased significantly. On the contrary,
the presence of Cu2+ quenched the fluorescence of compound 3
at 492 nm. In the presence of both Zn2+ and Cu2+, compound
3 presents fluorescence again but with small intensity. With the
fluorescence quantum yields as output signals and 0.25 is defined
at the gate limit. The fluorescence quantum yield of compound 3
in the presence of Zn2+ is larger than 0.25 and therefore the output
is 1, but in the presence of Cu2+, both of Cu2+ and Zn2+, as well as
free compound 3, the fluorescence quantum yields are all smaller
than 0.25 and the output is 0. The fluorescence intensity changes
described above mimic the function of an INHIBIT logic gate.
The truth table and logic diagram are shown in Fig. 11.
Fig. 8 Absorption(a) and fluorescence (b) spectra of compound 3 (20 mM)
in the presence of 3 equiv. of Zn2+ and various concentration of Cu2+ in
acetonitrile. (lex = 380 nm).
Logic operations based on the absorption and fluorescence spectra
of compound 3
It is well known that one can design a single molecule which
can simultaneously behave as two (or more) distinct logic gates,
depending on the exact choice or definition of outputs.12a Take
the advantage of high selectivity of compound 3 towards Zn2+ and
Cu2+, different logic operations with Zn2+ and Cu2+ as two chemical
inputs and absorption or emission spectra as multiple channel
outputs may be achieved. Fig. 9 (Top) compares the absorption
spectra of free compound 3, 3 + 3 equiv. Zn2+, 3 + 3 equiv. Cu2+
and 3 + 3 equiv. Cu2+ + 3 equiv. Zn2+. With the absorbance at
350 nm as the output signal, the absorbance of free compound
3 (no chemical input) is small (0.07 a.u.). But in the presence of
Zn2+ or Cu2+ or both Zn2+ and Cu2+, the absorbance at this point
increased to 0.26 a.u.. This observations are correlated with a two
input OR logic gate. The truth table is shown in Fig. 9 (Bottom).
If we choose the absorbance at 405 nm as the output signal, the
NOR logic operation can be achieved. Without any chemical
input, the absorbance at 405 nm is high, but in the presence of
either Zn2+, or Cu2+, the output signal is small. Similar small
output signal is also observed in the presence of both Zn2+ and
Cu2+.
Conclusion
From a view of a potential application, the reset capability is
very important for the chemical-driven logic operations. Although
various reset strategies have been addressed in some molecular
systems, the low reset capabilities are all the same main drawbacks
of molecular logic gates with chemical inputs. But the potential
application of molecular based logic gates in a small space such
as the inside of a cell makes the research on this topic still
prospective.12a In the present research, we have designed and
prepared successfully a new compound based on naphthalic
imide, which bears both intramolecular ICT and PET processes.
Selective coordination of Zn2+ and/or Cu2+ with this compound
at different positions can block selectively the above mentioned
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More importantly, the newly designed molecule could perform
NOR, OR and INH logic operations simultaneously with Zn2+
and Cu2+ as chemical inputs and absorption or emission spectra as
outputs. These results will be useful for further molecular design
to mimic the function of complex logic gates. Due to versatile
structural modification on naphthalene imides, more complicated
logic operations will be constructed. Related research is being
carried out on in our lab.
Experimental section
General methods
1H and 13C NMR spectra were recorded on a Bruker 300 MHz
NMR spectrometer with chemical shifts reported in ppm (in
CDCl3, TMS as internal standard). Mass spectra were recorded
on a LCQ advantage spectrometer with ESI resource. HRMS
were recorded on APEXII and ZAB-HS spectrometers. UV-
vis absorption spectra were measured on HITACHI U-4100
spectrophotometer. Fluorescence emission spectra were recorded
on an ISS K2 system.
Materials
The salts used in stock solutions of metal ions were CrCl3·6H2O,
MnCl2·4H2O, FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CuCl2·
6H2O, Zn(NO3)2·6H2O, CdCl2·2.5H2O, Hg(NO3)2, Pb(NO3)2. N-
(4-Amino-phenyl)-N¢,N¢-di(2-picolyl) ethylene diamine was syn-
thesized according to literature methods.15f,17 Other chemicals were
purchased from commercial sources. Solvents were of analytical
grade and purified by standard methods.
4-N-di(2¢-pyridylmethyl)amino-1,8-naphthalic anhydride (2).
In a 100 ml round bottom flask, di(2-pyridylmethyl)amine
(430 mg, 2.15 mmol) and monomethylglycol ether (50 ml) was
added. The mixture was stirred at room temperature for 5 min.
Then 4-bromo-1,8-naphthalic anhydride (500 mg, 1.8 mmol) was
added to the flask. After the reaction mixture was refluxed at
125 ◦C for 4 h it was cooled to room temperature and diluted
with 10 ml CH2Cl2. The organic layer was washed with water
(3 ¥ 80 ml) to remove the water soluble solvents and dried over
MgSO4 overnight. CH2Cl2 was removed under reduced pressure.
The residue was purified by column chromatography on silica
with CH3OH/CHCl3 (v/v) as eluent. The product was collected
Fig. 10 (a) Fluorescence spectra of compound 3, 3 with 3 equiv. Zn2+
,
3 with 3 equiv. Cu2+, and 3 with 3 equiv. Zn2+ + 3 equiv. Cu2+. The
concentration of 3 was 20 mM; (b) The corresponding fluorescence
quantum yield of compound 3 under different conditions.
as a pale yellow solid (120 mg, 0.30 mmol) with a yield of 17%.
◦
mp >250 C; H NMR (300 MHz, CDCl3, 25 ◦C, TMS): d =
1
9.00 (d, J = 8.3 Hz, 1H, naphthyl), 8.60 (m, 3H, naphthyl +
pyridyl), 8.38 (d, J = 8.4 Hz, 1H, naphthyl), 7.73 (t, J = 8.1 Hz,
1H, naphthyl), 7.64 (d, J = 7.8 Hz, 2H, pyridyl), 7.37 (d, J = 7.8
Hz, 2H, pyridyl), 7.26 (m, 3H, pyridyl + naphthyl), 4.80 (s, 4H,
NCH2); MS (ESI): m/z: 396.13 [M+H+]; Calcd for C24H18N3O3:
396.42. High resolution MS (ESI): m/z: 396.1250 (M+H+); Calcd
for C24H18N3O3: 396.1248.
N-p-(N¢-2-(N¢,N¢-di(2-pyridylmethyl)amino-ethylene)aniline)-
4-N¢¢-di(2-pyridylmethyl) amino-1,8-naphthalimide (3). N-(4-
amino-phenyl)-N¢,N¢-di-(2-picolyl) ethylene diamine (185 mg,
0.56 mmol) was added to a mixture of 20 ml dried toluene
and 2 g imidazole. Under the protection of nitrogen, 4-N-di(2¢-
pyridylmethyl)amino-1,8-naphthyl anhydride (2) (110 mg, 0.27
mmol) was added to the mixture. After refluxing at 110 ◦C for 3 h,
Fig. 11 The truth table for the INHIBIT logic gate and the corresponding
logic diagram (Positive logic; 0: low signal, 1: high signal).
intramolecular process. The responses of the molecule towards
outer stimulus are therefore enriched and thus the sensing of
multiplespecies by one sensor with high selectivitycan be achieved.
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the reaction mixture was diluted with 100 ml CH2Cl2 and washed
with water to remove imidazole. The organic layer was dried over
MgSO4 for overnight and the solvents were removed under reduced
pressure. The residue was purified by column chromatography
on silica gel with CH3OH/CH2Cl2 as eluent. The product was
collected as yellow oil (82 mg, 0.11 mmol) with a yield of 42%.
Chem.–Eur. J., 1997, 3, 1992; (b) S. H. Lee, J. Y. Kim, S. K. Kim, J. H.
Lee and J. S. Kim, Tetrahedron, 2004, 60, 5171.
10 (a) S. Iwata and K. Tanaka, J. Chem. Soc., Chem. Comm., 1995, 1491;
(b) O. S. Wolfbeis and H. Offenbacher, Monatsh. Chem., 1984, 115, 647;
(c) M. W. Hosseini, A. J. Blacker and J.-M. Lehn, J. Am. Chem. Soc.,
1990, 112, 3896; (d) D. Parker and J. A. G. Williams, Chem. Commun.,
1998, 245.
11 A. P. de Silva, N. D. McClenaghan and C. P. McCoy, Molecular
◦
mp >250 C; UV-vis, lmax 406 nm (e = 1.25 ¥ 104 mol L-1 cm-1);
Switches, Wiley-VCH, Weinheim, Germany, 2001.
◦
1H NMR (300 MHz, CDCl3, 25 C, TMS): d = 8.94 (d, J = 8.3
12 (a) O. A. Bozdemir, R. Guliyev, O. Buyukcakir, S. Selcuk, S. Kolemen,
G. Gulseren, T. Nalbantoglu, H. Boyaci and E. U. Akkaya, J. Am.
Chem. Soc., 2010, 132, 8029; (b) A. Coskun, E. Deniz and E. U. Akkaya,
Org. Lett., 2005, 7, 5187; (c) A. P. de Silva and N. D. McClenaghan,
Chem.–Eur. J., 2002, 8, 4935.
Hz, 1H, naphthyl), 8.62 (m, 5H, naphthyl + pyridyl), 8.41 (d, J =
8.1 Hz, 1H, naphthyl), 7.76–7.57 (m, 5H, naphthyl + pyridyl), 7.47
(d, J = 7.8 Hz, 2H, pyridyl), 7.39 (d, J = 7.8 Hz, 2H, pyridyl), 7.18
(m, 5H, naphthyl + pyridyl), 7.03 (d, J = 8.4 Hz, 2H, phenyl),
6.68 (d, J = 8.4 Hz, 2H, phenyl), 4.76 (s, 4H; NCH2), 3.94(s, 4H,
NCH2), 3.24 (t, J = 5.4 Hz, 2H, NCH2), 2.95(t, J = 5.4 Hz, 2H,
CH2); 13C NMR (300 MHz, CDCl3, 25 ◦C, TMS): d = 165.0, 164.5,
157.3, 153.7, 149.6, 148.4, 136.7, 136.6, 132.3, 131.4, 130.5, 129.0,
126.8, 125.9, 124.4, 123.7, 123.3, 122.5, 122.3, 117.7, 116.9, 113.0,
60.2, 59.9, 52.6, 41.2; MS(ESI) m/z: 711.42 [M+H+], Calcd for
C44H38N8O2: 711.31.
13 (a) X. Zhao and C. Z. Huang, Analyst, 2010, 135, 2853; (b) B. Valeur
and I. Leray, Coord. Chem. Rev., 2000, 205, 3; (c) J. P. Desvergne and
A. W. Czarnik, Chemosensors of Ion and Molecule Recognition, Kluwer
Academic, Dordrecht, Netherlands, 1997.
14 (a) E. Martin, J. L. G. Coronado and J. J. Cammacho, J. Photochem.
Photobiol., A, 2005, 175, 1; (b) Y. Gao and R. A. Marcus, J. Phys.
Chem. A, 2002, 106, 1956; (c) J. Gan, Q. Song, X. Hou, K. Chen and
H. Tian, J. Photochem. Photobiol., A, 2004, 162, 399; (d) D. Kolosov,
V. Adamovich, P. Djurovich, M. E. Thompson and C. Adachi, J. Am.
Chem. Soc., 2002, 124, 9945; (e) R. M. Duke, E. B. Veale, F. M. Pfeffer,
P. E. Kruger and T. Gunnlaugsson, Chem. Soc. Rev., 2010, 39, 3936;
(f) X. Qian, Y. Xiao,Y. Xu, X. Guo, J. Qiana and W. Zhua, Chem.
Commun., 2010, 46, 6418.
Acknowledgements
15 (a) D. Staneva, I. Grabchev, J. Soumillion and V. Bojinov, J. Photochem.
Photobiol., A, 2007, 189, 192; (b) V. B. Bojinov and T. N. Konstantinova,
Sens. Actuators, B, 2007, 123, 869; (c) H. He, M. A. Mortellaro, M. J.
P. Leiner, S. T. Young, R. J. Fraatz and J. K. Tusa, Anal. Chem., 2003,
75, 549; (d) X. Guo, X. Qian and L. Jia, J. Am. Chem. Soc., 2004, 126,
2272; (e) Z. Xu, Y. Xiao, X. Qian, J. Cui and D. Cui, Org. Lett., 2005,
7, 889; (f) J. Wang, Y. Xiao, Z. Zhang, X. Qian, Y. Yang and Q. Xu, J.
Mater. Chem., 2005, 15, 2836; (g) Z. Xu, X. Qian, J. Cuia and R. Zhang,
Tetrahedron, 2006, 62, 10117; (h) T. Gunnlaugsson, P. E. Kruger, T. C.
Lee, R. Parkesh, F. M. Pfeffera and G. M. Husseya, Tetrahedron Lett.,
2003, 44, 6575; (i) T. Gunnlaugsson, P. E. Kruger, T. C. Lee, R. Parkesh,
F. M. Pfeffera and G. M. Husseya, Tetrahedron Lett., 2003, 44, 8909;
(j) H. Ali and G. M. Hussey, J. Org. Chem., 2005, 70, 10875; (k) D. Cui,
X. Qian, F. Liu and R. Zhang, Org. Lett., 2004, 6, 2757; (l) Z. Xu, X.
Qian and J. Cui, Org. Lett., 2005, 7, 3029.
Financial support from the Natural Science Foundation of
China (Grant No. 21073112, 20771066) and instrument sup-
port from Key lab of Photochemical Conversion and Optoelec-
tronic Materials of Chinese Academy of Science are gratefully
acknowledged.
References
1 A. P. de Silva, H. Q. N. Gunaratne and C. P. McCoy, Nature, 1993, 364,
42.
2 (a) F. M. Raymo, Adv. Mater., 2002, 14, 401; (b) A. P. de Silva and
N. D. McClenaghan, Chem.–Eur. J., 2004, 10, 574; (c) P. Ball, Nature,
2000, 406, 118–120; (d) V. Balzani, M. Venturi and A. Credi, Molecular
Devices and Machines: A Journey into the Nanoworld, Wiley-VCH,
Weinheim, Germany, 2003; (e) A. P. de Silva and S. Uchiyama, Nat.
Nanotechnol., 2007, 2, 399; (f) D. C. Magri, T. P. Vance and A. P. de
Silva, Inorg. Chim. Acta, 2007, 360, 751; (g) A. Credi, Angew. Chem.,
Int. Ed., 2007, 46, 5472.
3 (a) A. P. de Silva, H. Q. N. Gunaratne and C. P. McCoy, J. Am. Chem.
Soc., 1997, 119, 7891; (b) H. Wang, D. Zhang, X. Guo, L. Zhu, Z. Shuai
and D. Zhu, Chem. Commun., 2004, 670; (c) Z. Zhao, Y. Xing, Z. Wang
and P. Lu, Org. Lett., 2007, 9, 547.
4 (a) P. Ghosh, P. K. Bharadwaj, S. Mandal and S. Ghosh, J. Am. Chem.
Soc., 1996, 118, 1553; (b) N. J. Youn and S.-K. Chang, Tetrahedron
Lett., 2005, 46, 125.
5 (a) A. P. de Sliva, S. A. de Sliva, A. S. Dissanayake and K. R. A.
S. Sandanayake, J. Chem. Soc., Chem. Commun., 1989, 1054; (b) A.
P. de Silva, H. Q. N. Gunaratne and P. L. M. Lynch, J. Chem. Soc.,
Perkin Trans. 2, 1995, 685; (c) M. N. Stojanovic, T. E. Mitchell and D.
Stefanovic, J. Am. Chem. Soc., 2002, 124, 3555; (d) T. Gunnlaugsson,
A. P. Davis and M. Glynn, Chem. Commun., 2001, 2556.
16 J. Wang and X. Qian, Chem. Commun., 2006, 109.
17 H. Wang, D. Wang, Q. Wang, X. Li and C. A. Schalley, Org. Biomol.
Chem., 2010, 8, 1017.
18 (a) H.-W. Rhee, C.-R. Lee, S.-H. Cho, M.-R. Song, M. Cashel, H. E.
Choy, Y.-J. Seok and J.-I. Hong, J. Am. Chem. Soc., 2008, 130, 784;
(b) H. M. Kim, M. S. Seo, M. J. An and B. R. Cho, Angew. Chem.,
2008, 120, 5245; (c) X. Peng, J. Du, J. Fan, J. Wang, Y. Wu and J. Zhao,
J. Am. Chem. Soc., 2007, 129, 1500; (d) K. Komatsu, K. Kikuchi,
H. Kojima, Y. Urano and T. Nagano, J. Am. Chem. Soc., 2005, 127,
10197; (e) A. Ojida, Y. Mito-oka, K. Sada and I. Hamachi, J. Am.
Chem. Soc., 2004, 126, 2454; (f) T. Hirano, K. Kikuchi, Y. Urano and
T. Nagano, J. Am. Chem. Soc., 2002, 124, 6555; (g) S. C. Burdette, G.
K. Walkup, B. Spingler, R. Y. Tsien and S. J. Lippard, J. Am. Chem.
Soc., 2001, 123, 7831; (h) T. Hirano, K. Kikuchi, Y. Urano and T.
Higuchi, J. Am. Chem. Soc., 2000, 122, 12399; (i) Z. Liu, C. Zhang, Y.
Li, Z. Wu, F. Qian, X. Yang, W. He, X. Gao and Z. Guo, Org. Lett.,
2009, 11, 795; (j) E. Ballesteros, D. Moreno, T. Go´mez, T. Rodr´ıguez, J.
Rojo, M. Garc´ıa-Valverde and T. Torroba, Org. Lett., 2009, 11, 1269;
(k) S. Atilgan, T. Ozdemir and E. U. Akkaya, Org. Lett., 2008, 10,
4065; (l) J. D. Amilan, M. Sandhya and G. Amrita, Org. Lett., 2007,
9, 1979; (m) X. Zhang, K. S. Lovejoy, A. Jasanoff and S. J. Lippard,
Proc. Natl. Acad. Sci. U. S. A., 2007, 104, 10780; (n) S. A. de Silva,
A. Zavaleta, D. E. Baron, O. A. Edward, V. Isidor, N. Kashimura and
J. M. Percarpio, Tetrahedron Lett., 1997, 38, 2237; (o) S. Banthia and
A. Samanta, New J. Chem., 2005, 29, 1001; (p) R. Trokowski, J. Ren,
F. K. Kalman and A. D. Sherry, Angew. Chem., Int. Ed., 2005, 44,
6920.
6 (a) A. P. de Silva and N. D. McClenaghan, J. Am. Chem. Soc., 2000,
122, 3965; (b) A. Credi, V. Balzani, S. J. Langford and J. F. Stoddart, J.
Am. Chem. Soc., 1997, 119, 2679.
7 (a) T. Gunnlaugsson, D. A. MacDonaill and D. Parker, Chem.
Commun., 2000, 93; (b) D. H. Qu, F. Y. Ji, Q. C. Wang and H. Tian,
Adv. Mater., 2006, 18, 2035; (c) T. Gunnlaugsson, D. A. MacDonaill
and D. Parker, J. Am. Chem. Soc., 2001, 123, 12866; (d) M. Kluciar, R.
Ferreira, B. de Castro and U. Pischel, J. Org. Chem., 2008, 73, 6079.
8 (a) A. P. de Silva, I. M. Dixon, H. Q. N. Gunaratne, T. Gunnlaugsson,
P. R. S. Maxwell and T. E. Rice, J. Am. Chem. Soc., 1999, 121,
1393; (b) Z. Wang, G. Zheng and P. Lu, Org. Lett., 2005, 7, 3669;
(c) P. N. Cheng, P. T. Chiang and S. H. Chiu, Chem. Commun., 2005,
1285.
19 (a) Y. Shiraishi, S. Sumiya, Y. Kohno and T. Hirai, J. Org. Chem., 2008,
73, 8571; (b) M. Zhu, M. Yuan, X. Liu, J. Xu, J. Lv, C. Huang, H.
Liu, Y. Li, S. Wang and D. Zhu, Org. Lett., 2008, 10, 1481; (c) M.
Yuan, W. Zhou, X. Liu, M. Zhu, J. Li, X. Yin, H. Zheng, Z. Zuo,
C. Ouyang, H. Liu, Y. Li and D. Zhu, J. Org. Chem., 2008, 73,
5008.
9 (a) M. Asakawa, P. R. Ashton, V. Balzani, A. Credi, G. Mattersteig, O.
A. Matthews, M. Montalti, N. Spencer, J. F. Stoddart and M. Venturi,
5444 | Org. Biomol. Chem., 2011, 9, 5436–5444
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