Highly soluble perylene tetracarboxylic diimides (PDI)-tetrathiafulvalene (TTF) dyad and TTF-PDI-TTF triad

Article abstract of DOI:10.1002/jhet.160

(Chemical Equation Presented) Two highly soluble donor-σ-acceptor and donor-σ-accepter-σ-donor type fluorescence switches consisting tetrathiafulvalene (TTF) and 3,4,9,10-perylene tetracarboxylic diimides (PDI) were synthesized. The structure of the dyad

Full text of DOI:10.1002/jhet.160

September 2009
Highly Soluble Perylene Tetracarboxylic Diimides (PDI)-
Tetrathiafulvalene (TTF) Dyad and TTF-PDI-TTF Triad
881
Chengyun Wang,* Wei Tang, Hanbin Zhong, Xuechao Zhang,
and Yongjia Shen
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of
Science and Technology, Shanghai 200237, People’s Republic of China
*E-mail: cywang@ecust.edu.cn
Received October 8, 2008
DOI 10.1002/jhet.160
Published online 2 September 2009 in Wiley InterScience (www.interscience.wiley.com).
Two highly soluble donor-r-acceptor and donor-r-accepter-r-donor type fluorescence switches con-
sisting tetrathiafulvalene (TTF) and 3,4,9,10-perylene tetracarboxylic diimides (PDI) were synthesized.
The structure of the dyad and triad as well as their intermediates was characterized by 1H NMR, 13C
NMR MS, elemental analysis. Their fluorescence behavior could be modulated by oxidization and
reduction of the TTF unit using either chemical or electrochemical method.
J. Heterocyclic Chem., 46, 881 (2009).
INTRODUCTION
tra, chemical, and electrochemical methods shows that
two novel fluorescence switches were established.
Perylene diimide (PDI) [1–7] has been used in donor-
acceptor supramolecules due to their optical, redox, and
stability properties. Tetrathiafulvalene (TTF) and its
derivatives [8–11] are well known for their p-electron-
donor properties. They have been extensively investi-
gated as building blocks in electrical conductors and
superconductors [12]. Some electron donor–acceptor
supramolecules with TTF units have been prepared for
studies related to intramolecular photoinduced electron
transfer processes, intramolecular charge-transfer (ICT)
interactions and construction of molecular rectifiers
[13–16].
RESULTS AND DISCUSSION
The target compound 1 and 2 were synthesized start-
ing from N-hexyl-1,6,7,12-tetra(4-tert-butylphenoxy)-
perylene-3,4-anhydride-9,10-tetracarboxylicimide (4) and
1,6,7,12-tetrakis(4-tert-butylphenoxy)-3,4,9,10-perylene-
tetracarboxy-anhydride (5) (Scheme 2).
Compounds 4, 5, and 6 were prepared by method pre-
viously reported [17–20]. The amino TTF 7 was synthe-
sized through ammonization of TTF 6 with the presence
of LiAlH4 in THF. The reaction of compound 4 and
amino TTF 7 led to dyad 1 (yield, 45%). The way to
get compound 2 was just like the reaction to get com-
pound 1. Amino TTF 7, compound 6 together with im-
idazole were heated to 175–180ꢁC for 48 h, and com-
pound 2 was finally achieved with a yield of 40% after
column chromatography on silica gel (CH2Cl2: ethyl
acetate ¼ 1:1).
However, the research of PDI-TTF type donor-
acceptor system was confined because of the poor solu-
bility of perylene diimide (PDI). Thus, we interested in
the introduction of tetra-substituent tetra-butylphenoxy
group to the bay region of PDIs to improve its solubil-
ity. In this article, electron donor-r-acceptor dyad 1 and
donor-r-acceptor-r-donor triad
2
containing PDI
and TTF unit were synthesized and characterized
(Scheme 1). The TTF unit is linked to PDI unit and the
PDI unit is modified by tert-butylphenol to increase its
solubility. TTF-type compounds are able to exist in
three different stable redox states (TTF, TTFꢀþ, TTF2þ).
Therefore, the donating ability of TTF could be tuned
by either chemical or electrochemical reversible redox
reactions. And the optical absorption, fluorescent spec-
With tetrasubstitutions of p-t-butylphenoxy at the bay
region, compound 1 and 2 were highly soluble in com-
mon organic solvents like CH2Cl2, CHCl3, ethyl acetate,
acetone, DMF, toluene, pyridine, and acetonitrile,
slightly soluble in methanol, and insoluble in hexane
and petroleum ether. The UV-vis spectra of dyad 1 and
triad 2 were measured in CH2Cl2 (1.0 ꢂ 10ꢃ5 M) with
CARY 100 Conc UV-vis spectrophotometer (Fig. 1).
C
V
2009 HeteroCorporation

882
C. Wang, W. Tang, H. Zhong, X. Zhang, and Y. Shen
Vol 46
Scheme 1. Structure of dyad 1 and triad 2.
moieties in the ground state. This result was coincident
with that of the UV-vis absorption.
Fluorescence spectra of 1, 2, and 3 were carried out
with a CARY Eclipse Fluorescence Spectrophotometer
in a 1 cm quartz cell (Fig. 2). Compared to compound
3, dyad 1 and triad 2 show a rather weak fluorescence.
The fluorescence quantum yield af (kexc ¼ 540 nm) of
Scheme 2. Synthetic procedure for compound 1 and 2: (a) KOH, iso-
propanol/H2O, N2, reflux; (b) LiAlH4, THF, N2; (c) imidazole, reflux
in m-cresol for 24 h, yield: 6, 45%; 7, 10%; (d) imidazole, reflux in
m-cresol for 48 h, yield 40%.
For comparison, the UV-vis spectra of model compound
3 and 8 (1.0 ꢂ 10ꢃ5 M in CH2Cl2) were also given.
Their spectral data were listed in Table 1.
The absorption spectra of 1, 2, 3 showed a wide absorp-
tion between 300 and 650 nm with identical absorption
maximum at about 451, 537, 577 nm. Compared with PDI
3, compound 1 and 2 have a new band at about 331 nm
which is coincide with the absorption of TTF 8. The UV-
vis absorption spectra of 1 and 2 were almost summation
of the spectra of donor 8 and acceptor 3 and no new band
or unique spectroscopic shoulder was observed, this
implying neglectable ground state electronic interaction
between perylene diimide and TTF unit.
The electrochemical characterization of 1, 2 and refer-
ence compounds 3, 8 were tested by cyclic voltammetry
(CV) and their voltammetric data were listed in Table 2.
All the experiments were performed in dichloromethane,
using n-Bu4NPF6 (10ꢃ1 M) as the supporting electrolyte,
platinum as the working and counter electrodes, and Ag/
AgCl as the reference electrode; the scan rate was
50 mV sꢃ1. Dyad 1 and triad 2 show almost the same
reduction potentials at about ꢃ0.90 and ꢃ0.60 V, which
were ascribed to the successive formation of the anion
radical PDIꢃ and dianion PDI2ꢃ. In positive direction, 1
and 2 exhibited two one-electron reversible oxidation
waves at about þ0.58, þ0.91, and þ1.37 V, correspond-
ing to the successive generation of the cation radical
TTFꢀþ, dication TTF2þ and cation radical PDIþ. Com-
parison of different values for dyad 1 and triad 2 with
reference compounds 3 and 8 suggested that no signifi-
cant interaction takes place between both electroactive
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2009
Highly Soluble Perylene Tetracarboxylic Diimides
(PDI)-Tetrathiafulvalene (TTF) Dyad and TTF-PDI-TTF Triad
883
Table 2
Oxidation potentials of compounds 1, 2, 3, and 8 in dichloromethane
(1.0 3 1023 M).
E1/2 (V)
Compound
PDI2ꢃ
PDIꢃ
TTFꢀþ
TTF2þ
PDIþ
1.37
3
8
1
2
ꢃ0.91
ꢃ0.60
0.54
0.58
0.56
0.91
0.93
0.92
ꢃ0.90
ꢃ0.89
ꢃ0.60
ꢃ0.61
1.38
1.40
chemically oxidized solution, both absorption and fluo-
rescence spectrum of compound 1 and 2 restored (see
Fig. 3). This is because the radical cation of TTF unit
(TTF2þ) of compound 1 and 2 transferred into neutral
unit after adding of Na2S2O3. This indicates that the flu-
orescence of dyad 1 and triad 2 could be modulated by
reversible chemical oxidation and reduction of TTF unit.
The fluorescence of dyad 1 and triad 2 could also be
modulated by reversible electrochemical oxidation and
reduction of TTF unit (see Fig. 4). Oxidation of com-
pound 1 and 2 (1.0 ꢂ 10ꢃ5 M) containing n-Bu4NPF6
(1.0 ꢂ 10ꢃ1 M) was performed by applying an oxida-
tion potential of 0.60 V (vs. Ag wire) to the solution.
Figure 4 show that the oxidation led to the increase at
600 nm. This is similar to the fluorescence spectral vari-
ation observed after chemical oxidation which is dis-
cussed above. The application of a reduction potential
of 0.1 V (vs. Ag wire) to former electrochemically oxi-
dized solution for 5 min also led to the transformation
of TTF2þ into neutral unit. Consequently, the fluores-
cence of dyad 1 and triad 2 restored (Fig. 4). As a
result, electrochemically oxidization and reduction
could also modulate the fluorescence of both dyad 1 and
triad 2.
Figure 1. Absorption spectrum of compounds 1, 2, 3, and 8 (1.0 ꢂ
10ꢃ5 M in CH2Cl2).
1 and 2 was 0.172 and 0.087 compared to PDI 3 (af
¼ 1). This weakly fluorescence emission of 1 and 2
could be attributed to a photoinduced electron transfer
(PET) reaction between PDI and TTF unit in the dyad
and triad for two major reasons: (1) DG values of 1 and
2 calculated using the Rehm-Weller equation [21] for
the photoinduced electron transfer reactions were ꢃ1.03
and ꢃ1.04 eV, thus these reactions are thermodynami-
cally favorable; (2) there was no spectral overlap
between the absorption spectrum of TTF unit and Fluo-
rescence spectrum of PDI unit. Hence, the energy trans-
¨
fer process was prohibited according to Forster mecha-
nism [4].
Figure 3 was fluorescence spectra of 1 and 2 after
addition of different amount of Fe3þ and further reduc-
tion by Na2S2O3 (1.0 ꢂ 10ꢃ5 M in CH2Cl2, kex ¼ 540
nm). It is known that TTF and its analogues can be oxi-
dized stoichiometrically by Fe3þ. As TTF being oxi-
dized to corresponding cation radical and dication spe-
cies, the fluorescence of compound 1 and 2 both
increased gradually after Fe3þ was added. The maxi-
mum fluorescent intensity of dyad 1 increased by 245%
after reaction with 1.0 equiv of Fe3þ and the maximum
fluorescent intensity of triad 2 increased by 663% after
2.0 equiv of Fe3þ was added. As expected, after react
with excess sodium thiosulfate (Na2S2O3) to the former
Table 1
The absorption data of compounds 1, 2, 3, and 8
(1.0 3 1025 M in CH2Cl2).
Compound
Absorption nm, e ꢂ 105 Mꢃ1 cmꢃ1
1
2
3
8
329(0.20), 448(0.21), 537(0.27), 577(0.43)
331(0.31), 449(0.17), 536(0.23), 577(0.37)
451(0.21), 537(0.34), 578(0.56)
312(0.12), 332(0.11)
Figure 2. Fluorescence spectrum of compounds 1, 2, and 3 (1.0 ꢂ
10ꢃ5 M in CH2Cl2, kex ¼ 540 nm).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

884
C. Wang, W. Tang, H. Zhong, X. Zhang, and Y. Shen
Vol 46
mmol) with KOH (6 g,10 mmol) in isopropylalcohol (60 mL)
and H2O (6 mL) were heated to reflux temperature under ar-
gon for 10 h, followed by acidic work up and thorough wash-
ing and drying, yielded a mixture (1.0 g) of perylenemonooc-
tylimide (4) and perylenebisanhydride (5) in a ratio of about
7:3. Compound 4 and 5 were separated by column chromatog-
raphy on a silica gel with CH2Cl2/petroleumether (1:1). Com-
1
pound (4): mp > 300ꢁC; H NMR (CDCl3, 500 MHz): d 8.25
(s, 4H, Hper), 7.25 (d, J ¼ 8.45 Hz, 8H, Har), 6.85 (d, J ¼
8.84 Hz, 8H, Har), 4.15 (t, J ¼ 7.6 Hz, 2H, NACH2), 1.65 (m,
4H), 1.3 (s, 36H, 4AC(CH3)3), 0.85 (t, J ¼ 6.4 Hz, 3H,
ACH3).Compound (5): mp > 300ꢁC; 1H NMR (CDCl3, 500
MHz): d 8.28 (s, 4H, Hper), 7.25 (d, J ¼ 8.46 Hz, 8H, Har),
6.85 (d, J ¼ 8.76 Hz, 8H, Har), 1.3 (s, 36H, 4-C(CH3)3).
4-Methyl-5-aminopropyl-4,5-bishexylenetetrathiafulvalene
(7). LiAlH4 (21 mg, 0.55 mmol) which is dissolved in 5 mL
anhydrous degassed THF was added dropwise to a stirred solu-
tion of compound 6 (114 mg, 0.2 mmol) in anhydrous
degassed THF (20 mL) under N2. The mixture was refluxed
for 2 h. After cooling, THF was evaporated in vacuo and
Figure 3. Fluorescence spectrum of dyad 1 (A) and triad 2 (B) (1.0 ꢂ
10ꢃ5 M in CH2Cl2, kex ¼ 540 nm) in the presence of different
amounts of Fe(ClO4)3 and further reduction by Na2S2O3.
CONCLUSIONS
We have designed and synthesized a new donor-r-ac-
cepter (D-r-A) type molecular fluorescence switches
dyad 1 and a new donor-r-accepter-r-donor (D-r-A-r-
D) type molecular fluorescence switch triad 2 containing
PDI and TTF units. Compound 1 and 2 both have excel-
lent solubility in most organic solvents because of the
tetra-substituted p-t-butylphenoxy at the bay region.
What’s more, their fluorescent behavior could be modu-
lated by reversible oxidation and reduction of TTF unit
either chemically or electrochemically.
EXPERIMENTAL
N-Hexyl-1,6,7,12-tetra(4-tert-butylphenoxy)-perylene-3,4-
anhydride-9,10-tetracarboxylicImide (4) and 1,6,7,12-
tetra(4-tert-butylphenoxy)-perylene-3,4,9,10-tetracarboxy-
licbisanhydride (5). N,N0-Dihexyl-1,6,7,12-tetra(4-tert-butyl-
phenoxy)-perylene-3,4,9,10-tetracarboxylicdiimide (2.2 g, 2.0
Figure 4. Fluorescence spectrum of dyad 1 (A) and triad 2 (B) (10ꢃ5
M in CH2Cl2, kex ¼ 540 nm, containing 10ꢃ1 M n-Bu4NPF6) after ox-
idation of 0.60 V (vs. Ag wire) for different period and further reduc-
tion of 0.1 V (vs. Ag wire) for 5 min (scan rate was 50 mV sꢃ1).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2009
Highly Soluble Perylene Tetracarboxylic Diimides
(PDI)-Tetrathiafulvalene (TTF) Dyad and TTF-PDI-TTF Triad
885
CH2Cl2 (20 mL) and H2O (10 mL) was added. The two phases
were separated and the organic phase was washed with H2O.
Column chromatography (silica gel, CH2Cl2: MeOH ¼ 4:1) af-
19.6, 14.1; MS (MALDI-TOF): m/z 2090.2 [M]þ (calcd for
C108H126N2O8S16
2090.5);
Anal.
Calcd
(%)
for
C108H126N2O8S16: C 61.97, H 6.07, N 1.34; Found C 61.91, H
6.02, N 1.38.
1
ter drying (MgSO4) give compound 7 (67mg). Yield: 60%. H
NMR (CDCl3): d 2.82 (m, 6H, ASCH2A), 2.68 (m, 2H,
ACH2N), 2.40 (s, 3H, ASCH3), 2.08 (s, 2H, NH2) 2.01 (m,
2H, ACH2A), 1.85 (m, 4H, ACH2A), 1.42 (m, 4H, ACH2A),
1.20–1.30 (m, 8H, ACH2A), 0.86 (t, J ¼ 6.8 Hz, 6H, ACH3).
Perylene-TTF dyad 1. N-Hexyl-1,6,7,12-tetra(4-tert-butyl-
phenoxy)-perylene-3,4-anhydride-9,10-tetracarboxylicimide (4)
(208mg, 0.2 mmol), amino-TTF 7 (110mg, 0.2 mmol) and im-
idazole (0.5 g) are added to 30 mL of m-cresol. The reaction
mixture was heated to 175–180ꢁC under dry nitrogen for 48 h
with stirring. After the reaction mixture was cooled to room
temperature, it was evaporated in vacuo to remove m-cresol.
The residue was washed by methanol to remove excess m-cre-
sol and TTF 7. Then the residue was washed with hot 1%
NaOH solution and hot water three times, respectively. After
drying, the residue was purified by chromatography on silica
gel using a mixture of dichloromethane-petroleum ether (1:1)
as eluent, to give a purple solid of dyad 1 (yield: 45%, 144
mg). mp > 300ꢁC; 1H NMR (CDCl3, 500 MHz): d 8.20 (s,
4H, Hper), 7.22 (d, J ¼ 8.45 Hz, 8H, Har), 6.80 (d, J ¼ 8.84
Hz, 8H, Har), 4.20–4.28 (m, 4H, NACH2), 2.75 (m, 6H,
SACH2A), 2.71 (m, 2H) 2.38 (s, 3H, ASCH3), 2.05 (m, 4H,
ACH2), 1.70 (m, 4H), 1.45 (m, 4H, CH2), 1.28–1.35 (m, 44H),
0.88 (t, J ¼ 6.4 Hz, 6H, ACH3). 0.82 (t, J ¼ 6.4 Hz, 3H,
ACH3). 13C NMR (CDCl3, 100 MHz): d 160.9, 155.7, 152.5,
147.2, 131.5, 127.4, 126.5, 122.3, 120.5, 119.7, 119.2, 110.1,
39.3, 36.7, 34.4, 31.6, 29.8, 29.3, 28.2, 27.7, 27.1, 22.5, 21.7,
19.4, 14.2, 13.8; MS(MALDI-TOF): m/z 1592.3 [M]þ (calcd
for C90H100N2O8S8 1592.5); Anal. Calcd (%) for
C90H100N2O8S8: C 67.80, H 6.32, N 1.76; Found C 67.71, H
6.38, N 1.72
Acknowledgments. This work was supported by National Natu-
ral Science Foundation of China (No. 20872035, 20676036), Spe-
cialized Research Fund for the Doctoral Program of Higher
Education (No. 20070251018) and the foundation of East China
University of Science & Technology (YJ0142130).
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mg, 0.1 mmol), amino-TTF 7 (230 mg, 0.4 mmol) and imidaz-
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temperature, it was evaporated in vacuo to remove m-cresol.
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¼ ꢃ0.60 eV, kex ¼ 540, e2/er ¼ ꢃ0.1 eV; For triad 2: Eox ¼ þ0.56
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet