A new tetrathiafulvalene-perylene diimide dyad with a pentaoxa-heptadecane chain as the spacer: metal-ions-induced aggregation

Article abstract of DOI:10.1016/j.tetlet.2006.10.083

A new TTF-perylene diimide dyad 1 with a pentaoxa-heptadecane chain as the spacer was synthesized and characterized. Absorption and fluorescent spectral studies of dyad 1 and reference compounds 2 and 3 indicate that aggregation of dyad 1 and compound 2 occurs in the presence of metal ions. Such metal-ions-induced aggregation is likely due to the synergic action of the coordination of metal ions with the oligoethylene glycol unit and the π-π stacking of the perylene diimide unit.

Full text of DOI:10.1016/j.tetlet.2006.10.083

Tetrahedron Letters 47 (2006) 9083–9087
A new tetrathiafulvalene–perylene diimide dyad with a
pentaoxa-heptadecane chain as the spacer: metal-ions-induced
aggregation
Xiaoping Zheng,a,b Deqing Zhanga,* and Daoben Zhua,*
aBeijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100080, China
bGraduate School of the Chinese Academy of Sciences, Beijing 100080, China
Received 15 July 2006; revised 16 October 2006; accepted 17 October 2006
Available online 7 November 2006
Abstract—A new TTF–perylene diimide dyad 1 with a pentaoxa-heptadecane chain as the spacer was synthesized and characterized.
Absorption and fluorescent spectral studies of dyad 1 and reference compounds 2 and 3 indicate that aggregation of dyad 1 and
compound 2 occurs in the presence of metal ions. Such metal-ions-induced aggregation is likely due to the synergic action of the
coordination of metal ions with the oligoethylene glycol unit and the p–p stacking of the perylene diimide unit.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Perylene diimides, initially studied as dyestuffs,1 have
been intensively investigated as electronic materials in
recent years due to their optical, redox and stability
properties.2 They are among the best n-type organic
semiconductors reported in the literature. High electron
mobilities have been described for organic-field-effect
transistors with perylene diimides as the semiconductor
layers.3 Perylene diimides are good electron acceptors,
and indeed D–A dyads with perylene diimides as the
electron acceptor units have been described. We have
previously reported tetrathiafulvalene (TTF)–perylene
diimide triads and found that the fluorescence is largely
quenched due to the photoinduced electron transfer
between TTF and perylene diimide units.4 Recently,
Hudlhomme and co-workers have shown that the
fluorescence of the tetrathiafulvalene–perylene diimide
dyad can be reversibly modulated by the transformation
of the TTF unit into its radical cation and dication.5
the p–p interaction.8 Interesting foldmers and nano-
structures generated through the assembly of perylene
diimides have been reported recently.9
Herein we report a new TTF–perylene diimide dyad 1
(Scheme 1) with a pentaoxa-heptadecane chain as the
spacer. According to previous studies,10 oligoethylene
glycol chain is able to coordinate with metal ions, and
as a result the separation between the TTF and perylene
diimide units would be shortened (Scheme 2). Accord-
ingly, the interaction between TTF and perylene diimide
units would be modulated to induce significant fluores-
cence quenching. However, detailed spectroscopic stud-
ies of dyad 1 and the reference compounds 2 and 3
(Scheme 1) indicate that dyad 1 and compound 2 both
containing oligoethylene glycol unit, aggregate in the
presence of various metal ions.
The synthesis of dyad 1 started from compound 4,11
from which compound 5 was prepared after removing
2-cyanoethyl group in the presence of CsOH and
sequentially reacting with 1,17-bis-(toluene-4-sulfonyl-
oxy)-3,6,9,12,15-pentaoxa-heptadecane.12 Compound 5
was transformed to compound 6 after substitution,
and the reaction of compound 6 with PPh3 led to com-
pound 7. The direct condensation of perylene tetracarb-
oxylic dianhydride with a mixture of 2-ethylhexylamine
and compound 7 (1:1 in molar ratio) in DMAc
Perylene diimides also show a tendency to aggregate in a
solution due to the stacking of the planar p systems.6
Both absorption and fluorescence spectral changes are
observed for perylene diimides upon aggregation.7 The
aggregation of perylene diimides has been achieved
through metal ion coordination and H-bonding besides
*
Corresponding authors. E-mail: dqzhang@iccas.ac.cn
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.10.083

9084
X. Zheng et al. / Tetrahedron Letters 47 (2006) 9083–9087
S
S
OTs
S
shifted and became weak upon addition of Ca2+
S
S
S
S
S
S
S
S
S
S
S
S
O
i
CN
O
(Fig. 1B).15 Such spectral changes for dyad 1 are likely
due to the coordination of the oligoethyleneglycol chain
with Ca2+. There are two possible ways for the interac-
tion of dyad 1 with Ca2+ as shown in Scheme 2: (1) the
‘intramolecular coordination of the oligoethyleneglycol
chain with Ca2+’; (2) the ‘intermolecular coordination
of the oligoethyleneglycol chain with Ca2+’. The intra-
molecular coordination would shorten the separation
between the TTF and perylene diimide units, and as a
result the interaction between the TTF and perylene
diimide units would be increased. On the other hand,
the intermolecular coordination would lead to the inter-
molecular aggregation of dyad 1 in solution. The results
from the control experiments with reference compound
2, as to be discussed below, indicate that the ‘intermole-
cular coordination of the oligoethyleneglycol chain with
Ca2+’ may be also responsible for the resulting absorp-
tion and fluorescent spectral changes of dyad 1 after
5
4
5
S
S
S
N3
NH2
S
S
S
S
S
S
S
ii
iii
O
5
5
S
S
S
7
6
O
O
S
S
N
O
S
S
S
S
N
O
iv
O
5
1
S
O
N
O
O
N
O
OH
O
3
2
O
N
O
O
N
O
the addition of Ca2+
.
Figure 2 shows the absorption and fluorescent spectra of
the reference compound 2 with a tetraethyleneglycol
chain unit. The absorption bands at 525 nm, 489 nm
3
Scheme 1. Reagents: (i) 1,17-bis-(toluene-4-sulfonyloxy)-3,6,9,12,15-
pentaoxa-heptadecane, CsOHÆH2O; (ii) NaN3, DMF; (iii) PPh3, THF;
(iv) perylene-3,4,9,10-tetracarboxylic acid dianhydride, 2-ethylhexyl-
amine, DMAc.
and 459 nm were gradually red shifted and their absorp-
tion intensities decreased upon the addition of Ca2+
.
16
Also, the fluorescence of 2 was gradually reduced in
the presence of Ca2+. In comparison, compound 3 with-
out the oligoethyleneglycol chain unit showed no varia-
tion in both absorption and fluorescence spectra in the
presence of Ca2+ under the same condition. Thus, the
spectral variation of 2 should be a reflection of the inter-
action of the oligoethyleneglycol unit with Ca2+. As
there is no TTF unit in compound 2, such spectral
changes cannot be ascribed to the ‘intramolecular coor-
dination of the oligoethyleneglycol chain with Ca2+’.
Moreover, the spectral changes of 2 in the presence of
Ca2+ are rather similar to those of perylene diimides
upon aggregation reported previously.7 Therefore, it
may be concluded that the aggregation of 2 occurred
in the presence of Ca2+ through the synergic effect of
the coordination of Ca2+ with oligoethylene glycol chain
and p–p stacking of the perylene diimide unit (Scheme
2). The intermolecular coordination mode of Ca2+ with
the oligoethyleneglycol chain is not clear at this stage
(dimethyl acetamide) led to dyad 1 after careful separa-
tion. Similarly, condensation of perylene tetracarboxylic
dianhydride with a mixture of 2-ethylhexylamine and 2-
{2-[2-(2-amino-ethoxy)-ethoxy]-ethoxy}-ethanol13 (1:1
in molar ratio) afforded reference compound 2 after sep-
aration. Compound 3 was synthesized in an excess of 2-
ethylhexylamine.14
Compared with compounds 2 and 3, dyad 1 shows a
rather weak fluorescence, a result ascribed to the photo-
induced electron transfer (PET) between TTF and peryl-
ene diimide units as reported previously.4,5 When Ca2+
was added to the solution of dyad 1, the fluorescence
intensity of dyad 1 decreased gradually and the emission
bands at 533 nm and 572 nm were slightly red shifted
(Fig. 1A). Simultaneously, the absorption bands of dyad
1 at 524 nm, 488 nm and 458 nm were gradually red
Dyad 1
Compound 2
O
N
S
O
O
O
O
OH
O
O
O
O S
N
O
Mn+
N
O
O
O
Mn+
Mn+
Mn+
Mn+
Perylene
Diimide
Oligoethyleneglycol
Chain
TTF
Scheme 2. The possible coordination modes of metal ions with the oligoethylene glycol chain and resulting aggregation of dyad 1 and compound 2.

X. Zheng et al. / Tetrahedron Letters 47 (2006) 9083–9087
9085
A
B
240
200
160
120
80
dyad 1
dyad 1
0.0 eq
0.2 eq
0.4 eq
0.6 eq
0.8 eq
1.0 eq
1.2 eq
1.4 eq
1.6 eq
1.8 eq
2.0 eq
3.0 eq
0.0 eq
0.2 eq
0.4 eq
0.6 eq
0.8 eq
1.0 eq
1.2 eq
1.4 eq
1.6 eq
0.6
0.4
0.2
0.0
40
0
500
550
600
650
700
750
400
450
500
550
600
650
Wavelength (nm)
Wavelength (nm)
Figure 1. Fluorescence (A) and absorption spectra (B) of dyad 1 (1.0 · 10À5 M in CH2Cl2) after the addition different amounts of Ca(ClO4)2
(dissolved in CH3CN); arrows indicate the direction of spectral change by increasing the amounts of Ca(ClO4)2.
0.8
0.6
0.4
0.2
0.0
A
B
0.0 eq
0.2 eq
0.4 eq
0.6 eq
0.8 eq
1.0 eq
1.2 eq
1.4 eq
1.6 eq
1.8 eq
2.0 eq
2.2 eq
3.0 eq
4.0 eq
compound 2
compound 2
1200
1000
800
600
400
200
0
0.0 eq
0.2 eq
0.4 eq
0.6 eq
0.8 eq
1.0 eq
1.2 eq
1.4 eq
1.6 eq
1.8 eq
2.0 eq
2.2 eq
3.0 eq
500
550
600
650
700
750
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
Figure 2. Fluorescence (A) and absorption spectra (B) of compound 2 (1.0 · 10À5 M in CH2Cl2) after the addition different amounts of Ca(ClO4)2
(dissolved in CH3CN); arrows indicate the direction of spectral change by increasing the amounts of Ca(ClO4)2.
although two possible coordination modes are proposed
in Scheme 2.
down-field shifts for the protons of the –CH2 unit of the
spacer. According to previous results,9b,18 aggregation
of the perylene diimide unit results in up-field shifts
for the perylene aromatic protons.
It is obvious that similar absorption and fluorescent
spectral changes occurred to dyad 1 and reference com-
pound 2 upon the addition of Ca2+. Therefore, it is rea-
sonably assumed that the ‘intermolecular coordination
of the oligoethyleneglycol chain with Ca2+’ the resulting
aggregation (Scheme 2) also contribute to the spectral
changes of dyad 1 in the presence of Ca2+. According
to previous studies,6–9 stacking of perylene diimide units
results in absorption spectral changes and the pending
TTF units, would further quench the fluorescence of
the perylene diimide unit through PET process.17
In addition, the perylene–spacer–perylene diimide in
which the spacer contained the oligoethyleneglycol units
was synthesized (see page S4–S5 Supplementary data).
The absorption bands became gradually weak and red
shifted upon the addition of Ca2+. Also, the intensities
of the fluorescent bands were reduced gradually in the
presence of Ca2+ (see Fig. S11 of Supplementary data).
These results indicated that aggregation occurred for the
perylene–spacer–perylene diimide in the presence of
Ca2+
Besides Ca2+, other metal ions (Li+, Na+, K+, Ba2+
.
1
The H NMR spectral measurements made for dyad 1
and compound 2 also provided evidence for their aggre-
gation in the presence of Ca2+. After addition of
1.0 equiv of Ca2+ to the CDCl3 solution (ca. 1 mM) of
dyad 1, the chemical shifts for the protons of –CH2 unit
of the spacer were down-field shifted by ca. 0.10 ppm
while those of the perylene diimide unit were up-field
shifted by ca. 0.11 ppm. Similar result was observed
for compound 2. It is understandable that coordination
of the oligoethylene glycol unit with Ca2+ would induce
,
Mn2+, Pb2+, Cd2+, Gd3+) were also tested. For instance,
Figure 3 shows the absorption spectral changes of dyad
1 and compound 2 upon the addition of Gd3+; the inten-
sities of absorption bands at 525 nm, 489 nm and
459 nm decreased gradually with obvious red-shifts.
These results imply that Gd3+ can also induce the aggre-
gation of dyad 1 and compound 2. Minor absorption
spectral variation was also detected for dyad 1 and

9086
X. Zheng et al. / Tetrahedron Letters 47 (2006) 9083–9087
0.7
0.6
0.5
0.4
A
B
0.0 eq
0.2 eq
0.4 eq
0.6 eq
0.8 eq
1.0 eq
2.0 eq
3.0 eq
4.0 eq
5.0 eq
compound 2
0.6
dyad1
0.0 eq
1.0 eq
2.0 eq
3.0 eq
4.0 eq
0.5
0.4
5.0 eq
0.3
0.2
0.1
0.0
0.3
0.2
0.1
6.0 eq
0.0
440 460 480 500 520 540 560 580 600
Wavelength (nm)
400
450
500
550
600
Wavelength (nm)
Figure 3. Absorption spectra of dyad 1 (A) (1.0 · 10À5 M in CH2Cl2) and compound 2 (B) (1.0 · 10À5 M in CH2Cl2) after the addition of different
amounts of Gd(ClO4)3 dissolved in acetonitrile; arrows indicate the direction of spectral change by increasing the amounts of Gd(ClO4)3.
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
A
B
dyad1
compound 2
0.05
0.04
0.03
0.02
0.01
0.00
0.0 eq
2.0 eq
0.0 eq
2.0 eq
400
450
500
550
600
350
400
450
500
550
600
650
Wavelength(nm)
Wavelength (nm)
Figure 4. Absorption spectra of dyad 1 (1.0 · 10À6 M in CH2Cl2) (A) and compound 2 (B) (1.0 · 10À6 M in CH2Cl2) after the addition of different
amounts of Ca2+ dissolved in acetonitrile; arrows indicate the direction of spectral change by increasing the amounts of Ca2+
.
compound 2 upon addition of Li+ (see Figs. S1 and S6
of Supplementary data), but there was no absorption
spectral change in the presence of Na+ and K+ (even
5.0 equiv of amounts of Na+/K+ were present). The dif-
ferent effects of metal ions on the absorption spectra of
dyad 1 and compound 2 may be related to their different
binding abilities with the oligoethyleneglycol chain.
pound 2 occurs in the presence of metal ions. Such me-
tal-ions-induced aggregation is likely due to the synergic
action of the coordination of metal ions with the oligo-
ethyleneglycol unit and the p–p stacking of the perylene
diimide units (Scheme 2). It should be noted that the
aggregation of perylene diimides under the influences
of metal ions were scarcely described. Further studies
of the perylene diimides with different oligoethylene
glycol units are under way.
The absorption spectra of dyad 1 and compound 2 could
not be measured at a high concentration due to their low
solubilities in organic solvents. On the other hand, the
absorption spectra of dyad 1 and compound 2 were re-
corded at a low concentration in the absence and pres-
ence of metal ions. As shown in Figure 4, even when
the concentration of dyad 1 and compound 2 was re-
duced to 1.0 · 10À6 M, their absorption spectra became
weak and red shifted upon the addition of Ca2+, imply-
ing the aggregation of dyad 1 and compound 2 occurred
even at such a low concentration.
Acknowledgments
The present research was financially supported by
NSFC and Chinese Academy of Sciences. D.-Q.Z.
thanks the National Science Fund for Distinguished
Young Scholars.
Supplementary data
In summary, a new TTF–perylene diimide dyad 1 with a
pentaoxa-heptadecane chain as the spacer was synthe-
sized and characterized. Absorption and fluorescent
spectral studies of dyad 1 and reference compounds 2
and 3 indicate that the aggregation of dyad 1 and com-
Experimental details for the synthesis of dyad 1, com-
pound 2 and the perylene diimide–spacer–perylene
diimide; absorption and fluorescence spectra of dyad 1
and compound 2 in the presence of metal ions; absorp-

X. Zheng et al. / Tetrahedron Letters 47 (2006) 9083–9087
9087
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15. Based on the plot of 1/(A À Ao) versus the reciprocal of
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3513–3520; (d) Quante, H.; Mullen, K. Angew. Chem., Int.
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À22.69 kJ molÀ1
.
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calculated to be À22.87 kJ molÀ1
.
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presence of Ca2+
.
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