An efficient multiple-mode molecular logic system for pH, solvent polarity, and Hg2+ ions

Article abstract of DOI:10.1016/j.tet.2008.05.048

A novel fluorophore 1,3-bis(1,1,3-trimethyl-1H-benzo[e]indol-2(3H)-ylidene)propan-2-one (L) was synthesized and fully characterized by ¹H NMR, ¹³C NMR, HRMS, and X-ray single-crystal structural analysis. Compound L is a pH-controlled molecular switch due to its protonation. The fluorescence change in protic polar solvents means that this compound also could be used as a protic solvent polarity sensor. Among the considered metal ions, the fluorescence of compound L could be quenched completely by Hg²⁺ ions with a high selectivity. Based on these fluorescence characters, this fluorescent dye L has promising applications as a multiple-mode molecular logic system.

Full text of DOI:10.1016/j.tet.2008.05.048

Tetrahedron 64 (2008) 8515–8521
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
An efficient multiple-mode molecular logic system for pH, solvent
polarity, and Hg2 ions
þ
Dong Zhang, Jianhua Su, Xiang Ma, He Tian *
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel fluorophore 1,3-bis(1,1,3-trimethyl-1H-benzo[e]indol-2(3H)-ylidene)propan-2-one (L) was syn-
Received 29 February 2008
Received in revised form 25 April 2008
Accepted 9 May 2008
1
13
thesized and fully characterized by H NMR, C NMR, HRMS, and X-ray single-crystal structural analysis.
Compound L is a pH-controlled molecular switch due to its protonation. The fluorescence change in
protic polar solvents means that this compound also could be used as a protic solvent polarity sensor.
Among the considered metal ions, the fluorescence of compound L could be quenched completely by
Available online 14 May 2008
2þ
Hg ions with a high selectivity. Based on these fluorescence characters, this fluorescent dye L has
promising applications as a multiple-mode molecular logic system.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Molecular logic gate
Hg sensor
pH switch
1
. Introduction
nitrogen atoms (trialkylamine moiety), which could be protonated.
In fact, basic donor amino groups can also act as fluorescence
13
Developing a wide variety of supramolecular systems per-
forming as elementary electronic devices, such as switches, sen-
sors, logic gates, and molecular-level machines, is an intense
research area and of tremendous significance to the development
of miniaturized device components. Potential applications of these
components in optical and electronic molecular-scale computa-
tional devices have attracted considerable effort to this research
quenchers. On account of the nitrogen atoms with lone electron
pairs, which can form coordinate bonds, L is propitious to recognize
special metal ion with high selectivity due to its structure. Based on
these results, a pH switch was achieved. Meanwhile, a highly
fluorescent material displaying novel solvent polarity-tunable
blue-green fluorescence emission was presented, which was clearly
different from the behaviors of solvent polarity sensors previously
reported. Otherwise, this molecule has a selective detection of
1
2
area.
2
þ
A significant amount of work has been devoted to obtain specific
molecule that is able to change one or several macroscopic prop-
erties in response external inputs. The design of fluorescent sig-
naling molecules has attracted a great deal of attention. Many
supramolecular systems, the emission properties of which can be
modulated by external inputs, such as temperature, pH, redox po-
tential, solvent polarity, and metal ions, have been reported.
There are few molecular systems behaving as ‘multiply config-
urable’ fluorescent indicators.
Merocyanine dyes are heterocyclic chromophores that are ex-
tensively used in a number of areas (i.e., as photographic sensi-
tizers, for nonlinear optics, and in chemotherapy). Recently, they
have also been employed as sensors of protein conformation and
Hg ions.
As a class of molecular devices, fluorescent logic gates play
3
a pivotal role in molecular computation because they are detectable
as a single molecule and can simultaneously treat multiple in-
4
14,15
puts.
Within the past decade, many fluorescent logic gates
showing NOT, AND, OR, XOR, NOR, NAND, and INHIBIT operations,
and combinational logic circuits incorporating single logic gates
5
–9
16
have been reported. In the same way, the molecule we reported
here could demonstrate three different logic functions (NAND,
10
þ
NOR, and INHIBIT) operated by solvent polarity, proton (H ), and
2
þ
Hg as inputs.
11
2. Results and discussion
12
protein interactions in live cell imaging. Here, we design a mer-
ocyanine dye, L (Scheme 1), which has a carbonyl bearing two
benzo[e]indoline fragments at both ends. At both sides, L has
The synthetic route to the merocyanine receptor (L) is illustrated
in Scheme 1. 1,1,2,3-Tetramethyl-1H-benzo[e]indolinium iodide (1)
and 2-methylene-1,1,3-trimethyl-1H-benzo[e]indoline (2) were
17
prepared according to the literature method. Treatment of 2 with
an appropriate amount of triphosgene and AlCl afforded the
symmetrical structural L. Compounds 1, 2, and L have been
*
Corresponding author. Tel.: þ86 21 64252756; fax: þ86 21 64252288.
E-mail address: tianhe@ecust.edu.cn (H. Tian).
3
0
040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.05.048

8516
D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
CH
3
I
NaOH
CH2
CH CN,
toluene, rt, 2h
3
N
N
I
N
2
(79%)
1
(91%)
Toluene, Pyridine
.Triphosgene,
°C to r t, 2h
1
0
2. AlCl3,
then to 50 °C, 5h 0° C to 50 °C, 3h
O
N
N
L (10%)
Scheme 1. Synthesis of merocyanine receptor L.
characterized by H NMR spectroscopy, 13C NMR spectroscopy, and
HRMS (ESI) spectrometry. Compound L was also characterized
crystallographically.
1
pH
.0
0
0
0
.9
.6
.3
8
2
.1. pH switch
2
.0
pH
2.0
Molecular systems behaving as a fluorescent indicator of the pH
þ
window have attracted much attention, because the proton (H )
18
concentration is simply and easily controlled. Due to the very low
solubility of L in water, its properties as a base have been examined
8.0
ꢁ
5
in a THF/H
was titrated with H (HClO
2
O mixed solvent. A 50% THF solution of L (1.0ꢀ10 M)
þ
þ
4
). After addition of H , the yellow so-
lution of L turned colorless (see the photograph in Fig.1a). The color
bleaching resulted from the progressive disappearance of the ab-
sorption band at 441 nm. Meanwhile, upon addition of H , a new
þ
0.0
smaller absorption band with a peak at 393 nm forms and de-
velops, as shown in Figure 2. The absorption makes a blue shift of
300
400
Wavelength/nm
500
4
8 nm. There is no absorption from 500 to 700 nm, so this segment
is not shown in Figure 2.
As shown in the photograph (Fig. 1b), the solution of L in 50%
THF emits blue fluorescence, which can be considered as ‘switched
Figure 2. UV–vis spectra in the course of titration of the aqueous THF solution
(
1.0ꢀ10ꢁ M) of L with H , at 298 K.
5
þ
þ
on’. Upon addition of H , the blue fluorescence was quenched
protonation, the whole conjugated system of the molecule has been
separated. Thus, the merocyanine-like chromophore was broken
up, which resulted in the blue shift of the absorption spectrum and
the quenching of the fluorescence.
gradually. It was quenched completely at pH¼2, which is consid-
ered as ‘switched off’ as shown in Figure 3. Since compound L is not
‘
ideal’ polymethine, the mirror-image relationship of absorption
and fluorescence is often abrogated.
In this pH sensing system, with a decrease in pH of the solution,
the color was bleached and the fluorescence quenched. This change
occurs because of the protonation of the nitrogen atoms (two tri-
alkylamine moieties). The nitrogen atoms change from electron-
contributing groups to electron-withdrawing units. After the
1.0
pH
8.0
0.8
0
0
0
0
.6
.4
.2
.0
2.0
4
50
500
550
600
Wavelength/nm
Figure 1. The color change (a) and fluorescence emission (b) responses of
L
ꢁ
5
þ
(
1.0ꢀ10 M in THF/H
2
O¼1:1) on addition of H . Left to right: in the absence (pH¼8)
Figure 3. Change in fluorescence spectra (
aqueous KCl (0.1 M) solution with 50% THF at 298 K.
l
ex¼410 nm) of L (10
mM) with pH in
þ
and presence (pH¼2) of H in KCl (0.1 M) solution at 298 K.

D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
8517
2
.2. Polar fluorescence
a
8
6
4
00
00
00
There have been several experimental and theoretical studies on
11a,19
the solvatochromic behavior of merocyanine dyes.
As a mer-
ocyanine dye, the spectral character of compound L may be largely
influenced in solvents of different polarities. We took the binary
mixed solvents, THF with relative lower polarity and H O with
2
higher polarity, to adjust the polarity of solvent. The emission
spectra of L were recorded with different fractions of THF in dis-
tilled water (Fig. 4).
b
c
2
As the addition of a high-polarity solvent (H O) to a low-polarity
one (THF), enhancement of the solvent polarity causes a significant
quenching of the fluorescence of L coupled with the appearance of
a new band centered at 520 nm. A dramatic fluorescence change
from blue (95% THF) to green (5% THF) could be clearly seen (Fig. 5).
The dual emission character of this compound shows an obvious
red shift. A well-defined isoemissive point at 508 nm can be clearly
observed (Fig. 4). This could be interpreted in terms of two emissive
species with a relationship, as one of the proofs for the formation of
the exciplex with a polar solvent. We have measured the fluo-
rescence spectrum of L in different polar mixed solvents (Fig. 6).
Due to the low solubility of L, its fluorescence spectra were
measured in different polar solvents containing 5% THF. Upon en-
200
0
d
4
50
500
Wavelength/nm
550
600
Figure 6. Emission spectra of L in mixed solvents with different polarities excited at
ꢁ
5
2
0
410 nm (1.0ꢀ10 M, at 298 K). From left to right: (a) pure THF; (b) 95% ethanolþ5%
THF; (c) 95% methanolþ5% THF; (d) 95% H Oþ5% THF.
2
solvent and the merocyanine molecule. These indicated that L
might be used as a solvent polarity sensor.
hancement of the solvent polarity (THF/CH
O), the fluorescence of L makes a red shift and the intensity is
weakened. This is probably due to the interaction between the
3 2 3
CH OH/CH OH/
H
2
2.3. Metal ions
Sensing harmful species is critical to the environment. Ele-
1
0
0
0
0
0
0
0
.0
.9
.7
.6
.4
.3
.1
.0
2
þ
2
2
1
5
5% THF
0% THF
0% THF
% THF
mentary mercury and Hg salts, which are dangerous for human
21
2þ
health, should be detected effectively. Hg is able to quench the
fluorescence of L when forming the corresponding complex giving
rise to the appearance of CHEQ (chelation enhanced quenching)
effect. The selective properties of L were determined toward rep-
þ
þ
2þ
2þ
2þ
resentative alkali (K ), alkaline earth (Ca and Ba ), and transi-
2
2þ
þ
2þ
2þ
2þ
tion-metal ions (Cd , Co , Ag , Ni , Cu , Zn , and Hg ). Upon
2
þ
interaction with 100 equiv of various metal ions, only Hg ion
exhibited effective fluorescence quenching among the tested metal
ions (Fig. 7a), even in the presence of other cations (e.g., Ca and
2
þ
2
þ
Cd , see Supplementary data).
2þ
This compound therefore possesses an efficient Hg selective
ON–OFF type signaling behavior, which can be explained by the
existence of deactivation channels involving the metal orbital. The
fluorescence quenching effect clearly indicates the coordination of
Hg at the receptor unit of L. Obviously, Hg binds to the two
nitrogen atoms, which have a lone electron pair. From the X-ray
single-crystal structure of L (Fig. 8), the space length between the
two nitrogen atoms (trialkylamine moiety) was found, which in-
dicated that L could form a complex only with particular ions that
have appropriate dimensions. Selected bond distances and angles
4
50
500
Wavelength/nm
550
2þ
2þ
ꢁ
5
Figure 4. Emission spectra of L (1.0ꢀ10 M, at 298 K) in H
2
O with different amount of
THF excited at 410 nm.
2
þ
are tabulated in Table 1. The dimensions of Hg are fit to form
a complex with L, but other metal ions do not have the suitable size.
2
þ
The stoichiometry of the L–Hg complex was estimated to be 1:1
1
by H NMR titration (Fig. 9) and a nonlinear curve fitting of the
fluorescence titration results (Fig. 10).
1
As shown in the H NMR spectra of Figure 9, L alone shows the
symmetrical planar structure, which can also be seen from the
2þ
single crystal (Fig. 8). Treatment with Hg ions resulted in destroy
of structural symmetry, which led to 10 signals (Fig. 9, up) from
original 5 signals (Fig. 9, down) in the range of 7.2–8.2 ppm.
To gain more insight into the chemosensing properties of L to-
2
þ
ward Hg ions, fluorescence titrations were carried out (Fig. 10). In
O, Fig.10), this system exhibited
high-polar solvent (5% THFþ95% H
2
very efficient fluorescence quenching, and over 85% of the total
fluorescence intensity change was observed with addition of
Figure 5. Photograph of L in 95% THF (left) and 5% THF (right), excited at 410 nm
(
1.0ꢀ10ꢁ M, at 298 K).
5
3 equiv of Hg ions. The association constant, Kassoc, was estimated
2þ

8518
D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
Table 1
(
a)
Free, Cd2+, Co2+
,
Selected bond distances (Å) and bond angles ( ) for L with estimated standard de-
viations in parentheses
ꢂ
7
6
5
4
3
2
1
00
00
00
00
00
00
00
0
+
Ag , Ni2+, Ca2+, K+,
N(1)–C(3)
N(1)–C(17)
N(2)–C(19)
N(2)–C(33)
C(3)–N(1)–C(17)
C(19)–N(2)–C(33)
C(18)–C(1)–C(2)
C(3)–C(2)–C(1)
1.377(2)
1.445(2)
1.3769(19)
1.440(2)
124.44(14)
125.13(15)
113.94(16)
128.75(17)
C(1)–C(18)
C(1)–C(2)
C(2)–C(3)
C(18)–C(19)
C(2)–C(3)–N(1)
C(19)–C(18)–C(1)
C(18)–C(19)–N(2)
1.459(2)
1.459(2)
1.355(2)
Ba2+ ,Cu2+, Zn2+
1.360(2)
122.59(16)
129.41(17)
121.41(16)
of L completely. On the other hand, when the solvent polarity is
Hg2+
high (5% THFþ95% H
O, Fig. 10), only 3 equiv of Hg could quench
2þ
2
the fluorescence intensity of L.
Several previous reports have designed switching systems
18
based on external inputs. The emission performances of chemo-
sensors are used as the example for mimicking the logic gates. Due
to the dependence of the fluorescence intensity of L on the external
stimulations, visible light (410 nm for excitation), metal ion (Hg ),
and polarity of solvent (THF/H O), it is possible to mimic the
4
50
500
550
Wavelength/nm
600
2
þ
(b)
2
function of an integrated two-input NAND logic gate (Fig. 11).
In the present system, excitation at 410 nm is the power supply.
We consider the polarity of the solvent as one inputdthe high
polarity (5% THFþ95% H
2
O) standing for 1 and the low one (50%
THFþ50% H O) standing for 0. The other input is the addition of
2
2
þ
3
equiv of Hg ions (symbol 1) or nonaddition (symbol 0). The
Figure 7. (a) Fluorescence spectra (
l
ex¼410 nm) and (b) photograph (irradiated at
fluorescence emission intensity (
signal as follows: if the emission reaches more than 70% of the
maximum emission intensity of the free ligand in low-polarity
l
¼520 nm) was used as the output
365 nm using UV lamp) of L (10
m
M) with various metal ions in 50% THF solution at
298 K.
solvent (50% THFþ50% H
2
O) at 520 nm, the output is considered as
2
2
by the nonlinear curve-fitting procedure of fluorescence titration
digital 1; if the emission lies below 10% of the maximum emission
intensity, the output is considered as digital 0. The symbol of two-
input NAND logic gate and the truth table is given in Figure 11.
4
ꢁ1
23
data and was 5.3ꢀ10 M . The detection limit was also estimated
from the titration results and was 2.1ꢀ10ꢁ M.
6
2
.4. Logic gates
2.4.2. NOR and INHIBIT dual-output gates based
on polarity–protonation pair
Compound L behaves as a pH-controlled molecular switch,
Compound L presents a red shift of fluorescence in different
polarity solvents. Meanwhile, the protonation of L could quench the
fluorescence emission. Based on these results, compound L could
2
þ
solvent polarity sensor, as well as Hg sensor, which constitutes
the basis for a molecular logic gate with three different logic
functions (NAND, NOR, and INHIBIT) in response to solvent polarity,
be applied as dual-output logic gate with NOR (Out
(Out ) functions.
1
) and INHIBIT
proton, and Hg2 ion.
þ
2
The two input signals are Input1 (high- or low-polarity solvent)
þ
2.4.1. NAND gate based on a polarity–CHEQ pair
and Input2 (H ), and the two output signals are the fluorescence
In Figure 10, we represent the quenching of fluorescence
emissions: Output1 (
l
¼470 nm) and Output2 ( ¼520 nm). We con-
l
emission of L with Hg2þ in two different polarity solutions. When
sider final outputs with digital 1 when the intensity of the fluores-
cence emission goes over 0.8 relative units, and with digital 0 when
the relative intensity of the emission is below 0.3 (see Fig. 12).
the solvent polarity is low (50% THFþ50% H
2
O, Fig. 10), relative
abundant Hg2 (100 equiv) was needed to quench the fluorescence
þ
Figure 8. Perspective drawing of compound L with atomic numbering scheme. Thermal ellipsoids were shown at the 50% probability level.

D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
8519
þ
Addition of H to the solution (pH¼2, Input2 is 1) leads to the
protonation of L, which brings on quenching of fluorescence
emission, resulting in 0 (Out 1) and 0 (Out 2) outputs. On the other
hand, when high-polar (5% THFþ95% H
2
O) solvent is employed
polarity Input is 1), L shows long-wavelength emission at 520 nm
(
(
Output2¼1). Based on this diversification, a binary logic gate
comes into being as shown in Figure 12.
We demonstrate that a simple-structured molecule, L, functions
as a fluorescent molecular logic gate with multiple outputs. The
most interesting feature of the present system is the fact that it can
operate with solvent polarity, and, therefore, this opens new pos-
sibilities in the design of molecular logic devices. Solvent polarity,
as one input, could be reset by adjusting reapportionment of dif-
ferent polar solvents or evaporating and re-dissolving with another
4
polar solvent. Adding acid (e.g., HClO ) and base (e.g., NaOH) could
achieve the reversibility of protonation. Due to the fact that EDTA
2
þ
has stronger complexation ability with Hg , it could be used for
2
þ
de-complexation of L–Hg complex. However, after several oper-
Figure 9. 1H NMR spectra of L blank (down) and in the presence of Hg ions (up) in
2þ
ations, this system will be saturated with acid and base, as well as
DMSO-d . All spectra were obtained at 298 K.
6
2þ
Hg and EDTA. It is the ubiquitous problem for most chemical
computers, which should be resolved with our efforts in the future.
When low-polarity (95% THFþ5% H
2
O) solvent is used (standing
for 0) and at pH¼8 (without H , standing for 0), L shows only short-
þ
3. Conclusion
wavelength emission at
l¼470 nm. Hence, two outputs monitoring
at 470 (Out
1
) and 520 nm (Out
2
) result in 1 and 0, respectively.
A new simple and easily made merocyanine dye L described
here displays multiple-mode fluorescence response driven by pH,
2
þ
solvent polarity, and Hg
ions. Controlling the multiple-mode
Hg2+
0 equiv.
fluorescence by simple chemical inputs resulted in three different
logic functions (NAND, NOR, and INHIBIT). The potential use of this
simple molecule as an efficient luminescent chemosensor as well as
a molecular logic system was demonstrated.
7
6
5
4
3
2
1
00
00
00
00
00
00
00
0
1
00 equiv.
4. Experimental section
4.1. General
1
The pH values were measured by using PHS-3C pH meter. H
13
NMR and C NMR spectra were obtained by using a Bruker AV 400
spectrometer. Mass spectra were performed with an HP5989 mass
spectrometer and UV–vis spectra on a Varian Cary 500 spectro-
photometer (1-cm quartz cell used). Fluorescent spectra were
recorded on a Varian Cary Eclipse fluorescence spectrophotometer.
Toluene was distilled from calcium hydride.
4
50
500
Wavelength/nm
550
600
4
.1.1. 1,1,2,3-Tetramethyl-1H-benzo[e]indolinium iodide (1)17
A mixture of 60 g (0.287 mol) 1,1,2-trimethyl-1H-indole and
4 g (0.6 mol) methyl iodide was refluxed in 200 ml acetonitrile for
h. Upon cooling to room temperature, compound 1 was pre-
Hg2+
0 equiv.
8
2
200
150
100
cipitated and filtered off and washed with cold diethyl ether, giving
white powder. Yield: 91 g; 91%; mp 219–220 C.
ꢂ
3
equiv.
4
.1.2. 2-Methylene-1,1,3-trimethyl-1H-benzo[e]indoline (2)17
A mixture of 20 g (0.057 mol) 1 and 7 g (0.125 mol) potassium
hydroxidewas stirred vigorouslyat room temperature in 40 ml water
and 100 ml toluene for 2 h. Upon standing, the organic phase was
4
isolated, dried (MgSO ), and then concentrated under reduced
pressure. The product was then recrystallized from ethanol to give 2
5
0
0
ꢂ
1
asolivine flakes. Yield: 10 g; 79%; mp 107–108 C; H NMR (400 MHz,
ꢂ
CDCl
3
, 25 C, TMS):
d
3 3
(ppm) 1.69 (s, 6H, CH ), 3.15 (s, 3H, N–CH ), 3.95
(
7
d, 2H, CH
2
, J¼26.4 Hz), 7.01 (d,1H, J¼4.8 Hz), 7.21 (s,1H), 7.41 (s,1H),
.72 (d, 1H, J¼5.2 Hz), 7.78 (d, 1H, J¼4.8 Hz), 7.98 (d, 1H, J¼5.6 Hz).
450
500
550
Wavelength/nm
600
4.1.3. 1,3-Bis(1,1,3-trimethyl-1H-benzo[e]indol-2(3H)-ylidene)
M) with Hg2 in
þ
m
propan-2-one (L)
Compound 2 (5 g, 0.0224 mol) was stirred in 60 ml dry toluene
and the temperature was kept below 5 C. Dry pyridine (15 ml) was
Figure 10. Change in fluorescence spectra (
low-polarity solvent (50% THFþ50% H O, up) and high-polarity solvent (5% THFþ95%
O, down) at 298 K.
l
ex¼410 nm) of L (10
2
ꢂ
H
2

8520
D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
Figure 11. Bar graph representation of the output (relative fluorescence at 520 nm) of the NAND gate (excited at 410 nm at 298 K), truth table, and logic scheme.
Figure 12. Fluorescence spectra (
l
ex¼410 nm) of L (0.1 M) in the absence and presence of Hþ in KCl (0.1 M) solution at 298 K, truth table, and logic scheme.
added to the mixture under stirring and isolated from water vapor.
A solution of 1.11 g triphosgene (0.0112 mol) dissolved in 15 ml dry
toluene was subsequently added dropwise at 0–5 C. After the
dropwise addition, the mixture was stirred at room temperature for
2 h and then heated at 50 C for 5 h. Then at 0–5 C, 2.5 g anhydrous
ꢂ
ꢂ
ꢂ
ꢂ
aluminum chloride (0.0187 mol) was added and heated at 50 C for
ꢁ
1
3
h. After cooling to room temperature, 150 ml NaOH (0.1 mol l
was added and stirred for 10 min. Upon standing, the organic phase
), and
then concentrated under reduced pressure to 10 ml solution. After
cooling, yellow solid (0.6 g) was precipitated and filtered off. The
product was washed with ethyl acetate (20 ml) and then recrys-
tallized from dichlorobenzene to give pure L as brilliant flakes.
)
Table 2
Crystal data and structural refinement data for L
was isolated, washed with water (3ꢀ100 ml), dried (MgSO
4
Empirical formula
Formula weight
Temperature
C
33
H
32
N
2
O
472.61
293(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Unit cell dimensions
Monoclinic
P2(1)/n
ꢂ
ꢁ1
Yield: 0.52 g; 10%; mp 253–254 C; IR (KBr, cm ): 3044, 2968,
2929, 1625, 1593, 1546, 1514, 1047, 943; H NMR (400 MHz, DMSO-
¼90ꢂ
1
a¼10.4999(10) Å,
a
ꢂ
b¼7.4272(7) Å,
c¼32.916(3) Å,
b
¼91.258(2)
ꢂ
d
6
, 25 C, TMS):
d
(ppm) 2.05 (s, 12H, CH
3
), 3.28 (s, 6H, N–CH
3
), 5.61
g
¼90ꢂ
3
(t, 2H, CHCO), 7.27 (t, 2H, Ar–H), 7.36 (d, 2H, J¼8.8 Hz, Ar–H), 7.48 (t,
Volume
2566.3(4) Å
1
3
2
H, Ar–H), 7.85 (m, 4H, Ar–H), 8.04 (d, 2H, J¼8.8 Hz, Ar–H);
C
),
Z
4
ꢁ
3
ꢂ
Calculated density
Absorption coefficient
F(000)
1.223 g cm
0.073 mm
1008
NMR (400 MHz, DMSO-d
6
, 25 C, TMS):
d
(ppm) 22.95 (4C, CH
3
ꢁ
1
3 2
30.02 (2C, N–CH ), 49.13 (2C, C(Me) ), 99.86 (2C), 110.41 (2C),
122.31 (2C), 122.79 (2C), 127.16 (2C), 127.33 (2C), 128.71 (2C), 129.46
Crystal size
0.481 mmꢀ0.412 mmꢀ0.387 mm
ꢂ
(2C), 129.66 (2C), 130.05 (2C), 130.18 (2C), 141.76 (1C, CO), 169.18
q
Range for data collection
2.02–27.00
þ
Limiting indices
Reflections collected/unique
Completeness to
Absorption correction
Max and min transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F
ꢁ13ꢃhꢃ13, ꢁ5ꢃkꢃ9, ꢁ40ꢃlꢃ41
14,507/5593 [R(int)¼0.0809]
99.4%
(2C); HRMS (ESI), m/z: 473.2577 [LþH] .
q
¼27.00ꢂ
Empirical
4.2. Crystal structural determination
1.0000 and 0.7535
Full-matrix least-squares on F2
5593/0/331
Single crystals of L were obtained by slow evaporation of
dichloromethane/ethanol solution. A yellow glassy crystal of di-
2
0.922
Final R indices [I>2
R indices (all data)
Largest diff. peak and hole
s
(I)]
R1¼0.0535, wR2¼0.1232
R1¼0.0818, wR2¼0.1350
0.222 and ꢁ0.222 e Åꢁ
mensions 0.481 mmꢀ0.412 mmꢀ0.387 mm was used for data col-
ꢂ
lection at 20 C (
l
¼0.71073 Å). Crystal data (CCDC 662222) and
3
structural refinement data are given in Table 2. These data can be

D. Zhang et al. / Tetrahedron 64 (2008) 8515–8521
8521
obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
8. (a) Fichou, D.; Hubert, C.; Garnier, F. Adv. Mater. 1995, 7, 914–917; (b) Zhang, G.;
Yang, G.; Wang, S.; Chen, Q.; Ma, J. S. Chem.dEur. J. 2007, 13, 3630–3635; (c)
Zhao, Z.; Xing, Y. J.; Wang, Z. X.; Lu, P. Org. Lett. 2007, 9, 547–550; (d) Silva, P. L.;
Bastos, E. L.; El Seoud, O. A. J. Phys. Chem. B 2007, 111, 6173–6180.
9
. (a) de Silva, A. P.; Gunaratne, H. Q. N.; McCoy, C. P. J. Am. Chem. Soc. 1997, 119,
891–7892; (b) Bodenant, B.; Fages, F.; Delville, M. M. J. Am. Chem. Soc. 1998,
20, 7511–7519; (c) de Silva, S. A.; Amorelli, B.; Isidor, D. C.; Loo, K. C.; Crooker,
Acknowledgements
7
1
This work was supported by NSFC/China (50673025, 90401026),
National Basic Research 973 Program (2006CB806200), and
Scientific Committee of Shanghai.
K. E.; Pena, Y. E. Chem. Commun. 2002, 1360–1361; (d) Rurack, K.; Resch-Genger,
U. Chem. Soc. Rev. 2002, 31, 116–127; (e) Yang, R. H.; Chan, W. H.; Lee, A. W. M.;
Xia, P. F.; Zhang, H. K.; Li, K. J. Am. Chem. Soc. 2003, 125, 2884–2885.
1
1
0. Shiraishi, Y.; Tokitoh, Y.; Hirai, T. Chem. Commun. 2005, 5316–5318.
1. (a) Brooker, L. G. S.; Keyes, G. H.; Sprague, R. H.; VanDyke, R. H.; VanLare, E.; Van
Zandt, G.; White, F. L.; Cressman, H. W. J.; Dent, S. G. J. Am. Chem. Soc. 1951, 73,
332–5350; (b) Tian, H.; Meng, F. S. Functional Dyes; Kim, S. H., Ed.; Elsevier:
Amsterdam, 2006; Chapter 2, pp 47–84; (c) Marder, S. R. Chem. Commun. 2006,
31–134.
2. (a) Toutchkine, A.; Kraynov, V.; Hahn, K. J. Am. Chem. Soc. 2003, 125, 4132–4145;
b) Nalbant, P.; Hodgson, L.; Kraynov, V.; Toutchkine, A.; Hahn, K. M. Science
004, 305, 1615–1619.
3. (a) Lakowicz, J. R. Principles of Fluorescence Spectroscopy; Plenum: New York, NY,
999; (b) Valeur, B. Molecular Fluorescence: Principles and Applications;
Wiley-VCH: Weinheim, 2002.
Supplementary data
5
1
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2008.05.048.
1
(
2
1
References and notes
1
1
. (a) Collier, C. P.; Wong, E. W.; Belohradsky, M.; Raymo, F. M.; Stoddart, J. F.;
Kuekes, P. J.; Williams, R. S.; Heath, J. R. Science 1999, 285, 391–394; (b) Balzani,
V.; Credi, A.; Raymo, F. M.; Stoddart, J. F. Angew. Chem., Int. Ed. 2000, 39, 3348–
14. (a) Balzani, V.; Credi, A.; Venturi, M. ChemPhysChem. 2003, 4, 49–59; (b) de
Silva, A. P.; Uchiyama, S. Nat. Nanotechnol. 2007, 2, 399–410.
15. (a) Weiss, S. Science 1999, 283, 1676–1683; (b) Zang, L.; Liu, R.; Holman, M. W.;
Nguyen, K. T.; Adams, D. M. J. Am. Chem. Soc. 2002, 124, 10640–10641; (c)
Qu, D. H.; Wang, Q. C.; Tian, H. Angew. Chem., Int. Ed. 2005, 44, 5296–5299.
16. Some examples: (a) de Silva, A. P.; Gunaratne, H. Q. N.; McCoy, C. P. Nature 1993,
364, 42–44; (b) Credi, A.; Balzani, V.; Langford, S. J.; Stoddart, J. F. J. Am. Chem.
Soc. 1997, 119, 2679–2681; (c) Baytekin, H. T.; Akkaya, E. U. Org. Lett. 2000, 2,
1725–1727; (d) Stojanovic, M. N.; Mitchell, T. E.; Stefanovic, D. J. Am. Chem. Soc.
2002, 124, 3555–3561; (e) Guo, X. F.; Zhang, D. Q.; Wang, T. X.; Zhu, D. B. Chem.
Commun. 2003, 914–915; (f) Guo, X. F.; Zhang, D. Q.; Zhang, G. X.; Zhu, D. B. J.
Phys. Chem. B 2004, 108, 11942–11945; (g) Tang, Y. L.; He, F.; Wang, S.; Li, Y. L.;
Zhu, D. B.; Bazan, G. C. Adv. Mater. 2006, 18, 2105–2110; (h) Qu, D. H.; Ji, F. Y.;
Wang, Q. C.; Tian, H. Adv. Mater. 2006, 18, 2035–2038.
3
2
391; (c) Feringa, B. L. Molecular Switches; Wiley-VCH: Weinheim, Germany,
001; (d) Balzani, V. Molecular Devices and Machines: A Journey into the Nano
World; Wiley-VCH: Weinheim, Germany, 2003; (e) Margulies, D.; Melman, G.;
Shanzer, A. Nat. Mater. 2005, 4, 768–771; (f) Tian, H.; Wang, Q. C. Chem. Soc. Rev.
2
006, 35, 361–374.
. (a) Feringa, B. L.; Van Delden, R. A.; Koumura, N.; Geertsema, E. M. Chem. Rev.
000, 100, 1789–1816; (b) Rudzinski, C. M.; Nocera, D. G. Optical Sensors and
2
2
Switches (Molecular and Supramolecular Photochemistry); Schanze, K. S., Ed.;
Marcel Dekker: New York, NY, 2001; Chapter 1, pp 1–91; (c) Trieflinger, C.; R o¨ hr,
H.; Rurack, K.; Daub, J. Angew. Chem., Int. Ed. 2005, 44, 6943–6947; (d) Jiang, G.;
Wang, S.; Yuan, W.; Jiang, L.; Song, Y. L.; Tian, H.; Zhu, D. B. Chem. Mater. 2006,
1
8, 235–237; (e) Amendola, V.; Fabbrizzi, L.; Foti, F.; Licchelli, M.; Mangano, C.;
Pallavicini, P.; Poggi, A.; Sacchi, D.; Taglietti, A. Coord. Chem. Rev. 2006, 250,
73–299; (f) Raymo, F. M.; Tomasulo, M. Chem.dEur. J. 2006, 12, 3186–3193; (g)
17. Wang, J.; Cao, W. F.; Su, J. H.; Tian, H.; Sun, Z. R. Dyes and Pigments 2003, 57,
171–179.
2
18. (a) Akkaya, E. U.; Huston, M. E.; Czarnik, A. W. J. Am. Chem. Soc. 1990, 112,
3590–3593; (b) de Silva, A. P.; Fox, D. B.; Huxley, A. J. M.; Moody, T. S. Coord.
Chem. Rev. 2000, 205, 41–57; (c) Amendola, V.; Fabrrizzi, L.; Mangano, C.;
Miller, H.; Pallavicini, P.; Parotti, A.; Taglietti, A. Angew. Chem., Int. Ed. 2002, 41,
2553–2556; (d) Shiraishi, Y.; Tokitoh, Y.; Hirai, T. Org. Lett. 2006, 8 3841–3444;
(e) Shiraishi, Y.; Tokitoh, Y.; Nishimura, G.; Hirai, T. J. Phys. Chem. B 2007, 111,
5090–5100.
19. (a) Brooker, L. G. S.; Keys, C. H.; Heseltine, D. W. J. Am. Chem. Soc. 1951, 73, 5350–
5356; (b) Reichardt, C. Solvents and Solvent Effects in Organic Chemistry; Chemie:
New York, NY, 1988; (c) Reichardt, C. Chem. Rev. 1994, 94, 2319–2358.
20. Weisenborn, P. C. M.; Huizer, A. H.; Varma, C. A. G. O. Chem. Phys. 1988, 126,
425–433.
R o¨ hr, H.; Trieflinger, C.; Rurack, K.; Daub, J. Chem.dEur. J. 2006, 12, 689–700.
. (a) Beer, P. D. Chem. Commun. 1996, 689–696; (b) Atwood, J. L.; Holman, K. T.;
Steed, J. W. Chem. Commun. 1996, 1401–1407; (c) de Silva, A. P.; Gunaratne, H.
Q. N.; Gunnlaugsson, T.; Huxley, A. J. M.; McCoy, C. P.; Rademacher, J. T.; Rice, T.
E. Chem. Rev. 1997, 97, 1515–1566; (d) Gale, P. A. Coord. Chem. Rev. 2000, 199,
3
1
81–233; (e) Suksai, C.; Tuntulani, T. Chem. Soc. Rev. 2003, 32, 192–202.
. (a) Fabbrizzi, L.; Licchelli, M.; Pallavicini, P. Acc. Chem. Res. 1999, 32, 846–853;
b) Raymo, F. M. Adv. Mater. 2002, 14, 401–414; (c) Brown, G. J.; de Silva, A. P.;
4
(
Pagliari, S. Chem. Commun. 2002, 2461–2464; (d) de Silva, A. P.; McClenaghan,
N. D. Chem.dEur. J. 2004, 10, 574–586.
. Uchiyama, S.; Kawai, N.; de Silva, A. P.; Iwai, K. J. Am. Chem. Soc. 2004, 126,
5
6
3
032–3033.
. (a) Liebsch, G.; Klimant, I.; Krause, C.; Wolfbeis, O. S. Anal. Chem. 2001, 73,
354–4363; (b) Charier, S.; Ruel, O.; Baudin, J. B.; Alcor, D.; Allemand, J. F.;
21. (a) Yoon, J.; Ohler, N. E.; Vance, D. H.; Aumiller, W. D.; Czarnik, A. W.
Tetrahedron Lett. 1997, 38, 3845–3848; (b) Prodi, L.; Bargossi, C.; Montalti, M.;
Zaccheroni, N.; Su, N.; Bradshaw, J. S.; Izatt, R. M.; Savage, P. B. J. Am. Chem.
Soc. 2000, 122, 6769–6770; (c) Moon, S. Y.; Cha, N. R.; Kim, Y. H.; Chang,
S. K. J. Org. Chem. 2004, 69, 181–183; (d) Liu, B.; Tian, H. Chem. Commun.
2005, 3156–3158; (e) Guo, Z. Q.; Zhu, W. H.; Shen, L. J.; Tian, H. Angew.
Chem., Int. Ed. 2007, 46, 5549–5553.
4
Meglio, A.; Jullien, L. Angew. Chem., Int. Ed. 2004, 43, 4785–4788; (c) Wong, K.
M. C.; Tang, W. S.; Lu, X. X.; Zhu, N.; Yam, V. W. W. Inorg. Chem. 2005, 44, 1492–
1498; (d) Koopmans, C.; Ritter, H. J. Am. Chem. Soc. 2007, 129, 3502–3503.
7. (a) de Santis, G.; Fabbrizzi, L.; Licchelli, M.; Sardone, N.; Velders, A. H. Chem.d
Eur. J. 1996, 2, 1243–1250; (b) Fabbrizzi, L.; Licchelli, M.; Mascheroni, S.; Poggi,
A.; Sacchi, D.; Zema, M. Inorg. Chem. 2002, 41, 6129–6136; (c) Zhang, G.; Zhang,
D.; Guo, X.; Zhu, D. Org. Lett. 2004, 6, 1209–1212; (d) Zapata, F.; Caballero, A.;
Espinosa, A.; T a´ rraga, A.; Molina, P. Org. Lett. 2007, 9, 2385–2388.
22. Nishizawa, S.; Cui, Y. Y.; Minagawa, M.; Morita, K.; Kato, Y.; Taniguchi, S.; Kato,
R.; Teramae, N. J. Chem. Soc., Perkin Trans. 2 2002, 866–870.
23. Shortreed, M.; Kopelman, R.; Kuhn, M.; Hoyland, B. Anal. Chem. 1996, 68,
1414–1418.