Synthesis and quantum chemical study of PDI derivatives with phenylalkynyl groups at the bay position

Article abstract of DOI:10.1016/j.molstruc.2009.09.035

Six new perylenetetracarboxylic diimide (PDI) compounds were prepared by introducing alkynyl or alkynylphenyl groups with different length to the bay position of PDI ring. The UV-vis absorption and emission spectra of these new compounds were recorded. Th

Full text of DOI:10.1016/j.molstruc.2009.09.035

Journal of Molecular Structure 938 (2009) 245–253
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and quantum chemical study of PDI derivatives
with phenylalkynyl groups at the bay position
*
Delou Wang, Yan shi, Chuntao Zhao, Baolong Liang, Xiyou Li
Key Lab for Colloid and Interface Chemistry of Education Ministry, Department of Chemistry, Shandong University, China 250100, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Six new perylenetetracarboxylic diimide (PDI) compounds were prepared by introducing alkynyl or alky-
nylphenyl groups with different length to the bay position of PDI ring. The UV–vis absorption and emis-
sion spectra of these new compounds were recorded. The red-shift on the maximum absorption and
emission peaks revealed the efficient participation of the side conjugation chain to the whole conjugation
system. The molecular structure, the frontier molecular orbital and the energy gaps between the highest
occupied orbital (HOMO) and the lowest un-occupied orbital (LUMO) were calculated with DFT method.
The results show good consistent with the experimental results. The absorption and emission spectra of
these six compounds were also simulated with TD-B3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d) methods.
The simulated results for the compounds with short side conjugation chain show better response to
the experimental results. However, the quantum calculation on the compounds with long conjugated
side chain do not give satisfied results because of the significant electron transfer characteristics in the
excited states.
Received 15 July 2009
Received in revised form 17 September
2009
Accepted 19 September 2009
Available online 26 September 2009
Keywords:
PDI
Phenylalkynyl
TD-DFT
Absorption spectra
Fluorescence spectra
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
at the bay positions of PDI were demonstrated to significantly af-
fect the electronic properties, including electronic absorption spec-
Perylene-3,4,9,10-tetracarboxylic diimide (PDI) derivatives
have attracted increasing attention in the past decade due to their
outstanding photochemical and thermal stabilities, ease of syn-
thetic modification, and desirable optical and redox characteristics.
Great application potentials have been revealed in the fields of or-
ganic filed effect transistors (OFETs) [1,2], organic light emitting
diodes (OLED) [3,4] electrostatic photographic copying devices
[5], solar cells [6,7], molecular electronics [8,9], as well as artificial
light harvesting system [10,11]. In order to meet the needs of dif-
ferent applications, PDIs with different structures and properties
have been prepared [12].
The structure modification of PDIs has been achieved by intro-
ducing side groups either to the imide nitrogen atoms or at the
bay positions, i.e. 1, 6, 7, 12 positions. Incorporation of substituents
to the imide nitrogen atoms can significantly improve the solubil-
ity of corresponding PDI derivatives in conventional organic sol-
vents and affect the packing model of PDI molecules in solid
films [13–15]. But, it can not significantly affect the electronic
structure and photophysical properties of PDI compounds because
of the orbital nodes on the imide nitrogen atoms in both the HOMO
and LUMO of PDI, which limit the electronic interactions between
PDI and corresponding substituents [16]. In contrast, substituents
tra, fluorescence spectra, and redox potentials [17–19]. The
substituents that have previously been incorporated onto the bay
positions of PDIs are limited to phenoxy groups [20,21], aryls
[22], cyclic secondary amines [23,24], cyano groups [25], halogens
[26], and alkoxy and/or alkythio groups [27]. Very recently, alkynyl
groups have been successfully introduced to the bay positions of
PDI by Sonogashira reactions [28]. The absorption and emission
spectra have been varied by the alkynyl groups significantly.
In the present work, we describe the synthesis and photophys-
ical properties of a series of novel PDIs with phenylalkynyl groups
of different length at the bay position of the PDI ring, 1–6 in
Scheme 1. As opposed to the previous reported PDI compounds,
which contains only one alkynyl group, the PDIs of this research
have several alkynyl groups linked by phenyl rings and formed a
long conjugated chain. This long linear aromatic substituent is ex-
pected in one hand to change the absorption and emission spectra
significantly and on the other hand to provide a reaction point for
connection of other groups.
2. Results and discussion
2.1. Molecular design and synthesis
The introduction of only one alkynyl group at the bay position
of PDI has been achieved by Sonogashira reaction [28] in literature.
* Corresponding author.
E-mail address: xiyouli@sdu.edu.cn (X. Li).
0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.09.035

246
D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
Scheme 1. Synthesis of PDI derivatives containing terminal alkynes and terminal benzene.
With this method, we successfully prepared PDI-Si in reasonable
yields. After been hydrolyzed by tetra-tert-butyl ammonium fluo-
ride, PDI-Si changed into 1. However, when we try to prolong the
aromatic arm by reacting 1 with 1-bromobenzene or p-bromo-
phenyl-alkynyl, the reaction failed to give the title compound
because of the reactivity dropping caused by the electron
withdrawing nature of PDI ring. However, the iodide derivatives
respectively, Scheme 1. In addition, 2 can also be synthesized by
the reaction of PDI-Br with 1,4-dialkynylbezene with a yield of
6.3%.
2.2. Absorption spectra
The absorption spectra of these series of compounds are shown
in Fig. 1 and the data are summarized in Table 1. Two absorption
bands were observed in the visible region, which can be assigned
to the absorption of PDI ring. The absorption bands in the region
of 300–400 nm are due to the absorption of alkynylphenyl chain,
can reacts with
1 readily, therefore 1-iodid-4-(2-trimethyl-
silyl)alkynyl-benzene was prepared as an important intermediate
to 2 and 3, Scheme 2. The terminal alkynyl groups of 1–3 are caped
with phenyl group by Sonogashira reactions to produce 4, 5 and 6,
Scheme 2. Synthesis of intermediate 7.

D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
247
Fig. 2. Normalized fluorescence spectra of compounds 1–6 in chloroform with
excitation at 410 nm.
Fig. 1. UV–vis absorption spectra of compounds 1–6 in chloroform.
longest conjugated side chain, not by the PDI (6) with the longest
conjugated side chain among these series of compounds.
Table 1
Photophysical properties of compounds 1–6.
(molꢀ1 L cmꢀ1
)
kem (nm)
Uf (%)
s (ns)
2.4. Theoretical simulation on the molecular structure and electronic
spectra
Compounds
kabs (nm)
e
1
2
3
4
5
6
563
578
581
575
580
581
5.62 ꢁ 104
5.00 ꢁ 104
5.05 ꢁ 104
5.02 ꢁ 104
4.96 ꢁ 104
4.90 ꢁ 104
589
604
615
602
610
620
97.2
91.0
67.6
81.0
72.3
76.0
5.80
6.75
7.60
6.82
7.41
7.44
In order to understand the experimental results in deep, the
ground state molecular structure, the frontier molecular orbital
distributions, the HOMO/LUMO energy gaps as well as the absorp-
tion and emission spectra of these six PDI compounds are calcu-
lated. In order to save the calculating time, the molecular
structures were simplified by replacing the dodecyloxy group with
methoxyl group and cyclohexyl groups with methyl groups.
which increased significantly in intensity and redshifted on the
wavelength along with the increase on the length of the substitu-
ent. The maximum absorption band in the visible region of the PDIs
shifted to red relative to their bromide precursor due to the exten-
sion of the conjugation.
The maximum absorption peak of 1 appears at 589 nm, which
red shifted for about 16 nm relative to the PDI with only one dode-
cyloxyl group. Further addition of one phenyl group red shifted the
maximum absorption peak to 581 nm in 3. With the increasing on
the distance of the alkynyl or phenyl group from the PDI core, the
red-shift effects of the alkynyl or phenyl groups on the maximum
absorption peak decreased remarkably. For example, the first phe-
nyl group in 4 redshifted the maximum absorption peak for about
18 nm, the second phenyl group in 5 redshifted the maximum
absorption peak for only 2 nm while the third phenyl group in 6
do not redshift the maximum absorption peak at all. Similar effects
were found for the alkynyl groups too.
2.4.1. Minimized molecular structure
Using b3lyp/6-31g(d) method, the minimized structure of com-
pounds 1–6 were optimized, Fig. 3. The calculated geometric
parameters, including bond length and torsion angle between
two naphthalene rings are listed in Table 2. In order to examine
the accuracy of this method, a PDI compound without substituents
at the bay positions, compound 9, with known crystal structure is
calculated [29]. Table 3 compares the calculated results with the
crystal data. The calculated values are basically in line with the
experimental values, indicating that the calculating method used
is reliable for the calculation of this kind of compounds.
For the unsubstituent compound 9, the torsion angle
a between
two naphthalene nucleuses basically is 0o. But when alkynyl and
alkoxyl groups were introduced at the bay positions, the torsion
angle between two naphthalene nucleuses increased to about
14–17.5o because of the steric hindrance. The conjugated chain
growth does not influence the torsion angle significantly, probably
because the steric hindrance is predominately determined by the
first atom of the side group which directly connected to the PDI
ring as reported previously [30].
2.3. Fluorescence spectra
Fig. 2 shows the fluorescence spectra of these new PDI com-
pounds in chloroform. As expected, the emission peaks signifi-
cantly redshifted because of the introduction of alkynyl and
phenyl groups. Along with the increasing on the length of the con-
jugated side chain, the magnitude of the redshifts on the emission
peak varied follow the same order as that observed for the absorp-
tion maximum. Both the fluorescence quantum yields and life-
times are measured for these series compounds. The results are
also summarized in Table 1. As can be seen from the data, the
introduction of the conjugated chain at the bay position of PDI in-
duced significant decrease on the fluorescence quantum yields and
remarkably prolonged fluorescence lifetimes. The smallest fluores-
cence quantum yield was presented by 3, which has the second
2.4.2. Calculated frontier molecular orbital
The energy levels of the frontier molecular orbital HOMO-5 to
LUMO+5 of 1–6 are listed in Fig. 4. Along with the increase on the
length of the side conjugation substituent, the HOMO/LUMO energy
gap decrease gradually as shown in Fig. 4. The decrease on the en-
ergy gap of HOMO/LUMO is caused mainly by the increase on the en-
ergy level of HOMOs. The energy gap between HOMO and LUMO
decrease following the order of 1 > 4 > 2 > 5 > 3 > 6, which is in
accordance with the redshift on the maximum absorption peaks in
the experimental recorded absorption spectra.

248
D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
Fig. 3. The molecular structure of compound 9 (A) and the minimized molecular structure of 2 (B and C).
Table 2
The geometric construction parameters of PDI derivatives.
Parameter
1
2
3
4
5
6
C1–C2
C2–C3
C3–C13
C18–C7
C7–C8
1.406
1.379
1.411
1.419
1.416
1.376
1.415
1.430
1.414
1.383
1.397
1.402
1.469
1.439
1.433
1.359
1.430
14.08
16.64
1.406
1.379
1.411
1.421
1.418
1.374
1.417
1.430
1.413
1.384
1.397
1.402
1.469
1.438
1.4326
1.359
1.422
14.31
17.38
1.406
1.379
1.411
1.422
1.418
1.374
1.417
1.430
1.413
1.384
1.397
1.402
1.469
1.439
1.433
1.359
1.421
14.11
17.17
1.405
1.379
1.411
1.421
1.418
1.374
1.417
1.430
1.413
1.384
1.397
1.402
1.469
1.438
1.433
1.360
1.422
13.98
16.95
1.405
1.379
1.411
1.422
1.418
1.374
1.417
1.430
1.413
1.384
1.397
1.402
1.469
1.438
1.432
1.360
1.421
14.11
17.08
1.406
1.379
1.411
1.422
1.418
1.374
1.417
1.430
1.413
1.384
1.397
1.402
1.469
1.439
1.433
1.359
1.421
14.10
17.15
C8–C9
C9–C20
C20–C19
C20–C10
C
10–C11
C11–C12
C12–C17
C17–C15
C19–C17
C19–C18
C1–R1
C7–R2
a1
Fig. 4. The molecular orbital energy and HOMO/LUMO energy gaps of 1–6.
a2
can be found that even in compound 6, which has the longest side
conjugation chain, the HOMO orbital can extend to the end of the
side chain.
Table 3
The theoretical calculated bond length and the crystal data of compound 9.
The conjugated substituents have a significantly larger propor-
tion in HOMO than that in LUMO, Table 4. The difference between
the contribution of conjugation substituent in HOMO and LUMO
increases along with the increasing in length of the substituent. Be-
cause of the larger difference on the contribution of substituent to
the HOMO and LUMO, the transition from HOMO to LUMO under
photoexcitation will induce electron cloudy flow from substituent
to PDI ring and thus endow the excited states of these series of
compounds with partial electron transfer characteristics. The elec-
tron transfer characteristic of the excited states will be more signif-
icant along with the increase on the length of the conjugated
substituent because of the increasing distance between the posi-
tive and negative charge center. This large electron transfer charac-
teristic will induce significant drop on the fluorescence quantum
yields, which consists with the experimental recorded fluorescence
quantum yields of these compounds.
Bondsa
Calculated
Experimentalb
C1–C2
C2–C3
C3–C13
1.399
1.384
1.416
1.429
1.416
1.384
1.399
1.396
1.471
1.431
1.431
ꢀ0.008
1.396
1.365
1.422
1.409
1.422
1.365
1.396
1.383
1.457
1.423
1.423
ꢀ1.188
C
13–C14
C13–C4
C4–C5
C5–C6
C6–C16
C16–C18
C14–C15
C
14–C16
a
a
See Fig. 3 for atomic labels.
Experimental data are taken from Ref. [29].
b
The calculated HOMO and LUMO orbital maps of these series of
2.5. Simulated UV–vis absorption spectra
compounds revealed that the conjugation has fully extended to the
alkynylphenyl chain. Fig. 5 shows the LUMO and HOMO orbital
maps of 3 and 6 as representatives, while the contribution of the
conjugated substituent for 1 to 6 are summarized in Table 4. It
TD-DFT can be effective for the excited states of the medium-
sized molecules, so it become a very popular excited states
simulation method. However, due to the general electron

D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
249
Fig. 5. Calculated molecular orbitals of 3 and 6: (A) HOMO of 3; (B) LUMO of 3.
Table 4
Table 5
The contribution of the substitutent to the HOMO and LUMO.
Use TD-b3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d) calculated maximum absorption
wavelength and experimental value of PDI compounds.
1 (%)
2 (%)
3 (%)
4 (%)
5 (%)
6 (%)
Compound
B3lyp
PBE1PBE
k(exp)/nm
HOMO
LUMO
4.73
2.93
20.43
6.50
39.61
7.18
16.14
5.63
37.29
6.75
59.40
7.16
k/nm
E/eV
f
k/nm
E/eV
f
1
2
3
4
5
6
546
593
627
583
625
655
2.27
2.09
1.98
2.13
1.98
1.89
0.5571
0.4646
0.4692
0.4698
0.4457
0.4494
531
572
596
564
596
613
2.34
2.17
2.08
2.20
2.08
2.02
0.5828
0.4996
0.5233
0.5001
0.4964
0.5283
563
578
581
575
580
581
exchange–correlation functional can not well descript the role of
long-range electron correlation in larger conjugate system and the
excited states with charge transfer characteristic, TD-DFT calcula-
tion always leads to results with larger difference from the experi-
mental results [31,32]. But the exact expression of the HF
(Hartree–Fock) exchange energy can better descript the long-range
electronicinteractions, so when a larger chargetransfer occurs in the
excited states, we can use hybrid functionals that contain a higher
proportion of HF to predict the experimental data [33,34]. We
choose b3lyp and PBE1PBE to simulate the absorption spectra of 1
to 6, because both of them are the hybrid functionals contain higher
proportion of HF (b31yp 20% and PBE1PBE 25%).
With TD-B3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d) methods,
the absorption spectra of 1–6 were simulated. The maximum
absorption peaks calculated are summarized in Table 5. The calcu-
lated results of TD-B3lyp/6-31g(d) for the compounds with short
side conjugation chain are relatively more close to the experimen-
tal results. But for the compounds with long side conjugation
chain, the calculated results of TD-PBE1PBE/6-31g(d) method seem
more accurate relative to the experimental results. The simulated
absorption spectra of 1 and 6 are shown in Fig. 6 as representatives.
It can be found that the simulated absorption spectra of compound
1 based on TD-B3lyp/6-31g(d) show good similarity with the
experimental recorded spectra. The maximum absorption at
546 nm due to the transition from HOMO to LUMO corresponding
well with the experimental recorded absorption peaks at 527 and
560 nm. The small peak at about 300 nm can be assigned to the
transition from HOMO-11 to LUMO, which can be ascribed to the
absorption of side conjugation chain. The simulated results based
on both TD-B3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d) methods
for other compounds were found diverse from the experimental re-
sults seriously especially for that with longer conjugation side
chain. The simulated results for compound 6 based on PBE1PBE/
6-31g(d) method as shown in Fig. 6 presents three main peaks,
two of them at 614 and 518 nm are assigned to the transition of

250
D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
Table 6
Structure parameter of the first singlet excited state structure of PDI derivatives 1–6.
Parameter
1
2
3
4
5
6
C1–C2
C2–C3
C3–C13
C18–C7
C7–C8
C8–C9
C9–C20
C20–C19
1.375
1.375
1.393
1.437
1.388
1.371
1.402
1.424
1.391
1.384
1.369
1.418
1.44
1.425
1.419
1.355
1.424
11.29
15.41
1.376
1.375
1.392
1.442
1.398
1.362
1.411
1.424
1.384
1.386
1.368
1.415
1.445
1.424
1.418
1.357
1.407
11.29
16.62
1.376
1.374
1.392
1.442
1.399
1.361
1.412
1.423
1.384
1.386
1.368
1.415
1.445
1.424
1.418
1.357
1.405
11.26
16.64
1.376
1.375
1.392
1.442
1.397
1.363
1.411
1.424
1.385
1.386
1.368
1.416
1.444
1.424
1.418
1.357
1.408
11.31
16.63
1.376
1.374
1.392
1.442
1.399
1.361
1.412
1.423
1.384
1.386
1.368
1.415
1.445
1.424
1.418
1.357
1.405
11.26
16.64
1.376
1.374
1.392
1.442
1.399
1.361
1.412
1.423
1.383
1.386
1.368
1.415
1.445
1.424
1.418
1.357
1.405
11.26
16.64
C20–C10
C10–C11
C11–C12
C12–C17
C17–C15
C19–C17
C19–C18
C1–R1
C7–R2
a1
a2
Based on the optimized structure of the excited state, we calcu-
lated the maximum fluorescence emission wavelength by using
TD-b3lyp-6-31g(d) and TD-PBE1PBE-6-31g(d) methods. The calcu-
lated results are shown in Table 7. Similar to the calculated absorp-
tion spectra, the calculated largest emission wavelengths shifted to
longer wavelength with the conjugation chain growth of the sub-
stituent, this is in accordance with the experimental results. The
calculated results based on TD-b3lyp/6-31g(d) method for 1, which
has short conjugation chain length, show good coincident with the
experimental results while the results for the PDIs with longer con-
jugation chain diverted significantly from the experimental results.
Contrarily, the calculated results based on PBE1PBE method for 4
responds to the experimental results well while the calculated re-
sults for other compounds in this series present large difference
from the experimental results. This results suggest that the calcu-
lation on the maximum fluorescence emission by both TD-b3lyp-
6-31g(d) and TD-PBE1PBE-6-31g(d) methods do not give satisfied
results especially for those with long conjugation side chain. Both
methods have over estimated the contribution of the alkynyl or
phenyl groups which far away from the PDI core to the whole
conjugation system, this has also observed during the absorption
spectra simulation.
Fig. 6. The experimental and simulated absorption spectra of 1 and 6 (1, b3lyp. 6,
PBE1PBE).
HOMO to LUMO and HOMO-1 to LUMO respectively, which depar-
ture from the experimentally recorded two peaks at 581 and
541 nm significantly. The largest absorption peak in the simulated
absorption spectra at 400 nm is assigned to the transition from
HOMO to LUMO+1. The LUMO+1 of compound 6 distributed
mainly on the conjugation side chain as shown in Fig. 5E, therefore
the transition from HOMO to LUMO+1 can be ascribed to the
absorption of the alkynylphenyl chain. However, the absorption
of the conjugation side chain in the experimental recorded spectra
is at 350 nm, which is obviously shorter in wavelength than the
theoretical predication. This might be caused by the disturbance
on the conjugation of the side chain because of the solvation dur-
ing the experiment. The longer the side chain is, the stronger the
disturbance will be, and the diversion of the theoretical predication
from the experimental results will be more significant just as seen
in the calculated results of other compounds in these series.
Fluorescence quantum yield, Uf, can be simply expressed as:
Kf
Uf
¼
Kf þ KNR
where KNR is the non-radiative transition rate constant and Kf is the
fluorescence radiation rate constant. Kf is closely related with the
oscillator strength, f. Large f means quick transition and therefore
Table 7
The calculated largest fluorescence emission wavelength compared with experimen-
tal data.
2.6. Simulated fluorescence spectra
Compound
1
2
3
4
5
6
The stable first singlet excited state was obtained by single-
excitation configuration interaction CIS/3-21g(d) approach for 1–
6. Table 6 lists the structural parameters of the first singlet excited
states. From the frequency results, no imaginary frequency appear,
so the optimized excited state structures are stable structure on
the potential energy surface. Compared the excited state structural
parameters with those of the ground states, we can find that the
length of the most bonds are reduced little bit in the excited state.
Only few examples, such as C18–C7, C12–C17 and C10–C11 are in-
creased. The twist angles between two naphthalene rings are de-
creased in the excited states according to the calculated result.
Expt.
Uf (%)
E/eV
Cala
Ea/eV
fa
589 nm
97.2
2.11
588 nm
2.109
0.549
575 nm
2.16
604 nm
91
2.06
618 nm
2.007
0.469
612 nm
2.03
615 nm
67.6
2.09
663 nm
1.870
0.441
636 nm
1.95
602 nm
81
2.06
612 nm
2.027
0.472
606 nm
2.04
612 nm
72
2.03
652 nm
1.902
0.436
637 nm
1.95
620 nm
76
2.05
680 nm
1.823
0.432
646 nm
1.92
Calb
Eb/eV
fb
0.555
0.475
0.477
0.500
0.461
0.481
a
Calculated by TD-b3lyp/6-31g(d).
Calculated by TD-PBE1PBE/6-31g(d) method.
b

D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
251
results in shorter fluorescence lifetime and larger fluorescence
quantum yield. The calculated f for 1 is 0.55, which is the largest
among these PDIs, corresponding well with the experimental re-
corded largest fluorescence quantum yield and the shortest fluores-
cence lifetime for 1. Meaning while, 3 and 5 present the smallest f in
these series compounds and corresponding well with the smallest
experimentally recorded fluorescence quantum yields and longest
fluorescence lifetimes of them. It is interesting that both the fluo-
rescence quantum yields and the fluorescence lifetime do not
change linearly with the increase of the conjugation length of the
substituent.
ppm): 7.64 (m, 2H), 7.19 (m, 2H), 0.24 (s, 9H); MALDI-TOF MS
(m/z): Calculated: 300.12; Found: 300. Compound 8 (1,4-bis(2-
(trimethysilyl)ethynyl)-benzene was collected from the third frac-
tion. Yield: 0.106 g, (20%). 1H NMR (CDCl3), (d: ppm): 7.38 (d, 4H),
0.24 (s, 9H).
4.1.2. N,N-dicyclohexyl-1-dodecyl-7-ethynyl-perylene-3,4,9,10-
tetracarboxydiimide (1)
To
a mixture of PDI-Br (81.7 mg, 0.1 mmol), CuI (4 mg,
0.01 mmol), Pd(PPh3)4 (15 mg, 0.012 mmol), toluene (5 mL), and
triethylamine (1 mL) in a 100 ml round bottom flask, trimethylsi-
lylacetylene (30 lL) were added under the protection of nitrogen.
The mixture was heated to 50 °C and kept at this temperature
for 2 h. The solvents were then evaporated under reduced pressure.
The residue was column chromatographied on silica gel with chlo-
roform and n-hexane (6:1, v/v) as eluent. The first fraction contains
PDI-Si. Yield: 78.7 mg, (94.6%). The PDI-Si was not further purified
and characterized but put into next step directly to synthesis com-
pound 1.
A mixture of PDI-Si (83 mg, 0.1 mol), dried THF (15 mL), and
half drop of TBAF was stirred at room temperature for 30 min.
The solvents were evaporated under reduced pressure. The residue
was column chromatographied on silica gel with chloroform as
eluent. 1 was collected as red solid. Yield: 71 mg, (92%). 1H NMR
(CDCl3), (d: ppm): 9.97(d, 1H), 9.45(d, 1H), 8.71 (s, 1H), 8.55 (m,
2H), 8.38 (s, 1H), 5.03 (m, 2H), 4.46 (m, 2H), 3.78 (s, 1H), 2.59
(m, 4H), 2.09–1.26 (m, 36H), 0.87 (t, 3H); 13C NMR (300 MHz
CDCl3), (d: ppm): 163.7, 163.6, 163.3, 163.1, 157.5, 148.0, 137.9,
137.8, 134.8, 134.0, 133.1, 133.1, 131.1, 130.8, 130.1, 128.5,
128.2, 127.8, 127.8, 127.6, 127.5, 124.4, 123.6, 123.3, 122.5,
122.0, 118.3, 117.6, 106.2, 105.0, 70.6, 54.1, 54.0, 31.9, 29.7, 29.6,
29.6, 29.3, 29.2, 29.1, 26.6, 26.3, 25.5, 22.7, 14.1; MALDI-TOF MS
(m/z): Calculated: 763.0; Found: 763.
3. Conclusion
Introduction of alkynylphenyl groups at the bay positions of PDI
could vary the photophysical properties of PDI compounds effi-
ciently. The redshifted absorption and emission maximum peaks
revealed the participation of the conjugated side chain to the
whole conjugation system of the molecule. The quantum calcula-
tion on the molecular structure, the orbital energy levels and the
frontier orbital maps reveal the electron transfer characteristics
for the excited states of these compounds. The simulated absorp-
tion and emission spectra for the PDIs with short side conjugation
chain shown good coincident with the experimental results. How-
ever, along with the increase on the length of the side conjugation
chain, the quantum calculation results diverted from the experi-
mental results more and more significantly probably because of
the enhanced electron transfer characteristics of the excited states.
4. Experimental
4.1. Materials and methods
N,N-dicyclohexyl-1-bromo-7-dodecyl-perylene-3,4,9,10-tetra-
carboxy diimide (PDI-Br) and N,N-dicyclohexyl-1,7-bi(4-tert-
butyl)phenoxy)perylene-3.4,9,10-tetracarboxylic diimide was
prepared following the literature methods [27,35], all other
chemicals are purchased from commercial source. Solvents were
of analytical grades and were purified by the standard method be-
fore use.
4.1.3. N,N-dicyclohexyl-1-dodecyloxy-7-(1,4-diethynylbenzene)pery-
lene-3,4,9,10-tetracarboxydiimide (2)
A mixture of 1 (38 mg, 0.05 mmol), CuI (2 mg, 5
lL), Pd(PPh3)
(7.5 mg, L), toluene (5 mL), triethylamine (1 mL) and 7
6
l
(24 mg, 0.08 mmol) was heated to 50 °C under the protection of
nitrogen. The reaction mixture was kept at this temperature for
about 1 h, and then the solvents were evaporated under reduced
pressure. The residue was column chromatographied on silica gel
with chloroform and n-hexane (6:1, v/v) as eluent. The first frac-
tion was collected. The dried compound was dissolved in dried
THF (5 mL), and half drop of TBAF. The mixture was stirred at room
temperature for 30 min. Then THF was evaporated under reduced
pressure. The residue was column chromatographied on silica gel
with chloroform as eluent. The first fraction contains 2. Yield:
25.8 mg, (62%). 1H NMR (CDCl3), (d: ppm): 9.82 (d, J = 8.1 Hz,
1H), 9.32 (d, 1H), 8.56 (s, 1H), 8.41 (m, 2H), 8.28 (s, 1H), 7.56 (m,
4H), 5.01 (m, 2H), 4.37 (m, 2H), 3.28 (s, 1H), 2.59(m, 4H), 2.05–
1.27 (m, 36H), 0.88 (t, 3H); 13C NMR (300 MHz CDCl3), (d: ppm):
163.6, 163.4, 163.3, 162.9, 157.3, 136.8, 133.5, 132.7, 132.5,
132.3, 131.5, 131.4, 130.7, 130.5, 128.0, 127.9, 127.4, 127.4,
127.0, 126.9, 124.4, 124.2, 123.3, 123.0, 122.6, 122.2, 121.8,
121.5, 119.5, 117.7, 117.2, 97.5, 97.2, 93.0, 83.1, 70.5, 54.2, 54.1,
31.9, 29.7, 29.6, 29.4, 29.4, 29.3, 29.2, 29.1, 26.7, 26.3, 25.6,22.7,
14.1; MALDI-TOF MS (m/z): Calculated: 863.12; Found: 862.
Compound 2 can also be obtained by following procedures: A
mixture of PDI-Br (150 mg, 0.183 mmol), CuI (10 mg, 0.025 mmol),
Pd(PPh3) (25 mg, 0.02 mmol), DMF (50 mL), NaOH (15 mg,
0.375 mmol) and 1,4-dialkynylbenzene (24 mg, 0.183 mmol) was
heated to 80 °C under the protection of nitrogen. The reaction mix-
ture was kept at this temperature for about 24 h, and then the sol-
vents were evaporated under reduced pressure. The residue was
washed with water thoroughly. The mixture was purified by col-
1H NMR and 13C NMR spectra were recorded on a Bruker DPX
300 spectrometer (300 MHz) in CDCl3. Electronic absorption spec-
tra were recorded on a Hitachi U-4100 spectrophotometer. Fluo-
rescence spectra and the fluorescence life time were measured
on a K2 system (ISS product) with the excitation at 410 nm. The
fluorescence lifetimes were measured with a phase modulation
model with a scattering sample as standard. The fluorescence
quantum yields are calculated with N,N-dicyclohexyl-1,7-bi(4-
tert-butyl)phenoxy)perylene-3,4,9,10-tetracarboxy diimide as
standard. MALDI-TOF mass spectra were taken on a Bruker BIFLEX
III ultra-high resolution Fourier transform ion cyclotron resonance
(FT-ICR) mass spectrometer. Elemental analyses were performed
on a VarioEL III analyzer.
4.1.1. (2-(4-Iodophenyl)ethynyl)trimethysilane (7)
A mixture of paradiiodobenzene (0.66 g, 2 mmol), Pd(PPh3)4
(250 mg, 0.2 mmol), CuI (18 mg, 0.02 mmol), toluene (30 mL) and
triethylamine (6 mL) was stirred at room temperature for 5 min
under the protection of nitrogen, and then trimethylsilylacetylene
(150 ll, 1 mmol) was added to the reaction mixture. The mixture
was heated to 50 °C and kept at this temperature for 5 h. Then
the solvents were evaporated under reduced pressure. The residue
was column chromatographied on silica gel with petroleum ether
as eluent. The second fraction was collected. Compound 7 was col-
lected as white solid. Yield: 0.46 g, (38.3%). 1H NMR (CDCl3), (d:

252
D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
umn chromatographied on silica gel with chloroform as eluent.
Compound 2 (10 mg, 0.012 mmol) was collected from the second
fraction with a yield of 6.3%.
4.2. Calculation model and method
By Gaussian03 quantum chemical software package [36], we
employ b3lyp/6-31g(d) theoretical methods and basis set for these
six PDI derivatives structural optimization and vibration analysis.
Vibration analysis results show that there is no imaginary fre-
quency appears, so the structures of these PDI derivatives are sta-
ble ground state structure. Take advantage of these ground state
structure, we use TD-B3lyp/6-31g(d) and TD-PBE1PBE/6-31g(d)
to calculate the absorption spectra. Use cis/3-21g(d) optimize the
first excited singlet state of these six PDI derivatives. Vibration
analysis results show that there is no imaginary frequency appears,
so the excited state structure is stable structure. Then we use TD-
B3lyp/6-31g(d) and TD-PBE1PBE1/6-31g(d) to calculate the fluo-
rescence emission wavelength. All the calculations were performed
using the Gaussian 03 program in the IBM P690 system at the
Shandong Province High Performance Computing Centre. With
the help of the SWIZARD software [37], the calculated electronic
absorption data of 1 and 6, were simulated to sequential absorp-
tion spectrum.
4.1.4. N,N-dicyclohexyl-1-dodecyloxy-7-(1,2-bis(4-
ethynylphenyl)ethyne)perylene-3,4,9,10-tetracarboxydiimide (3)
With 2 (21 mg) as starting material, following the similar proce-
dures of 2, compound 3 was prepared. Yield: 14.3 mg, (60%). 1H
NMR (CDCl3), (d: ppm): 10.01 (d, J = 8.24 Hz, 1H), 9.505 (d,
J = 8.4 Hz, 1H), 8.74 (s, 1H), 8.56 (m, 2H), 8.42 (s, 1H), 7.60 (s,
4H), 7.51 (m, 4H), 5.05 (m, 2H), 4.47 (m, 2H), 3.20 (s, 1H), 2.57
(m, 4H), 2.16–1.26 (36 H), 0.87 (t, 3H); 13C NMR (300 MHz CDCl3),
(d: ppm): 163.5, 163.4, 163.4, 163.1, 132.3, 132.1, 131.9, 131.9,
131.6, 131.5, 128.1, 127.7, 54.2, 54.1, 31.9, 29.7, 29.6, 29.4, 29.3,
29.2, 29.1, 26.6, 26.3, 25.6, 22.7, 14.1; MALDI-TOF MS (m/z): Calcu-
lated: 962.8; Found: 962.
4.1.5. N,N-dicyclohexyl-1-dodecyl-7-(4-ethynylbenzene)perylene-
3,4,9,10-tetracarboxydiimide (4)
A mixture of 1 (38 mg, 0.05 mmol), CuI (2 mg, 5
lL), Pd(PPh3)4
(7.5 mg, 6 L), iodo-benzene (12.3 mg, 0.06 mmol), toluene (5 mL),
l
and triethylamine (1 mL) was heated to 50 °C at kept at this tem-
perature for about 1 h. Then the solvents were evaporated under
reduced pressure. The residue was column chromatographied on
silica gel with chloroform as eluent. Compound 4 was collected
as red powder. Yield: 12.1 mg, (58%). 1H NMR (CDCl3), (d: ppm):
d 10.03 (d, J = 8.2 Hz, 1H), 9.46 (d, J = 8.4 Hz, 1H), 8.73 (s, 1H),
8.52 (m, 2H), 8.38 (s, 1H), 7.64 (m, 2H), 7.46 (m, 3H), 5.04 (m,
2H), 4.44 (m, 2H), 2.59 (m, 4H), 2.16–1.26 (m, 36H), 0.85 (t, 3H);
13C NMR (300 MHz CDCl3), (d: ppm): 163.6, 163.6, 163.5, 163.2,
157.4, 137.0, 133.9, 133.7, 133.1, 131.8, 130.8, 129.4, 128.8,
128.3, 128.2, 127.7, 127.5, 127.3, 127.1, 124.3, 123.3, 123.2,
122.4, 121.9, 121.7, 119.9, 118.4, 117.4, 97.8, 91.3, 54.2, 54.0,
31.9, 29.7, 29.6, 29.4, 29.4, 29.3, 29.2, 29.1, 26.6, 26.3, 25.5, 22.7,
14.1; MALDI-TOF MS (m/z): Calculated: 839.1; Found: 838.
Acknowledgements
Financial support from the Natural Science Foundation of China
(Grant Nos. 20640420467, 20771066, 20571049), Ministry of Edu-
cation of China, Shandong University, is gratefully acknowledged.
References
[1] H.E. Katz, Z. Bao, S.L. Gilat, Acc. Chem. Res. 34 (2001) 359–369.
[2] F. Würthner, Angew. Chem. Int. ED. 40 (2001) 1037–1039.
[3] M.A. Angadi, D. Gosztola, M.R. Wasielewski, Mater. Sci. Eng. B 63 (1999) 191–
194.
[4] P. Ranke, I. Bleyl, J. Simmerer, D. Haarer, A. Bacher, H.W. Schmidt, Appl. Phys.
Lett. 71 (1997) 1332–1334.
[5] K.Y. Law, Chem. Rev. 93 (1993) 449–486.
[6] B.A. Gregg, R.A. Cormier, J. Am. Chem. Soc. 123 (2001) 7959–7960.
[7] A.J. Breeze, A. Salomon, D.S. Ginley, B.A. Gregg, H. Tillmann, H.H. Horhold, Appl.
Phys. Lett. 81 (2002) 3085–3087.
[8] R.T. Hayes, M.R. Wasielewski, D. Gosztola, J. Am. Chem. Soc. 122 (2000) 5563–
5567.
[9] W.B. Davis, W.A. Svec, M.A. Ratner, M.R. Wasielewski, Nature 396 (1998) 60–
63.
[10] F. Hippiu, F. Schlosser, J. Am. Chem. Soc. 128 (2006) 3870–3871.
[11] K. Tornizaki, R.S.R.S. Loewe, C. Kirmaier, J.K. Schwartz, J.L. Retsek, D.F. Bocian, J.
Org. Chem. 67 (2002) 6519–6531.
[12] A. Hagfeldt, M. Gratzel, Acc. Chem. Res. 33 (2000) 269–277.
[13] K. Balakrishman, A. Datar, T. Naddo, J. Huang, R. Oitker, M. Yen, J. Zhao, L.
Zhang, J. Am. Chem. Soc. 128 (2006) 7390–7398.
[14] K. Balakrishnan, A. Datar, R. Oitker, H. Chen, J. Zuo, L. Zang, J. Am. Chem. Soc.
127 (2005) 10496–10497.
[15] J. Locklin, D. Li, S.C.B. Mannsfeld, E. Borken, H. Meng, R. Advincula, Z. Bao,
Chem. Mater. 17 (2005) 3366–3374.
[16] Z. Chen, M.G. Debije, T. Debaerdemaeker, P. Osswald, F. Würthner,
Chemphychem 5 (2004) 137–140.
4.1.6. N,N-dicyclohexyl-1-dodecyloxy-7-(1-ethynyl-4-(2-
phenylethynyl)benzene)perylene-3,4,9,10-tetracarboxydiimide (5)
Following the similar procedure of 4, with 2 as starting material,
compound 5 was prepared. Yield: 12.4 mg, (53%). 1H NMR (CDCl3),
(d: ppm): 9.77 (d, J = 8.2 Hz, 1H), 9.24 (d, 1H), 8.47 (s, 1H), 8.35 (m,
2H), 8.22 (s, 1H), 7.59 (m, 4H), 7.38 (m, 5H), 5.02 (m, 2H), 4.32 (m,
2H), 2.56 (m, 4H), 2.17–1.27 (m, 36H), 0.85 (t, 3H); 13C NMR
(300 MHz CDCl3), (d: ppm): 163.6, 163.5, 163.5, 163.2, 157.4,
136.9, 134.0, 133.7, 133.1, 131.9, 131.8, 131.6, 130.8, 128.6,
128.4, 128.3, 128.2, 127.7, 127.5, 127.4, 127.1, 124.5, 124.3,
123.4, 123.3, 122.9, 122.0, 121.9, 121.7, 119.9, 118.1, 117.4, 97.4,
93.0, 88.9, 86.3, 70.6, 54.2, 54.1, 31.9, 29.7, 29.6, 29.4, 29.4, 29.2,
29.1, 26.6, 26.3, 25.5, 22.7, 14.1; MALDI-TOF MS (m/z): Calculated:
939.2; Found: 938.
[17] C.C. Chao, M.K. Leung, Y.O. Su, K.Y. Chiu, T.H. Liu, S.J. Shieh, S.C. Lin, J. Org.
Chem. 70 (2005) 4323–4331.
[18] S. Becker, A. Böhm, K. Müllen, J. Chem. Eur. 6 (2000) 3984–3990.
[19] H. Langhals, P. Blanke, Dyes Pigment 59 (2003) 109–116.
[20] M. Sandrai, L. Hadel, R.R. Sauers, S. Husain, K. Krogh-Jespersen, J. Phys. Chem.
96 (1992) 7988–7996.
[21] C. Ego, D. Marsitzkey, S. Becker, J. Zhang, A.C. Grimsdale, J.D. MacKenzie, C.
Silva, R.H. Friend, J. Am. Chem. Soc. 125 (2003) 437–443.
[22] W. Qiu, S. Chen, X. Sun, Y. Liu, D. Zhu, Org. Lett. 8 (2006) 867–870.
[23] J.M. Serin, D.W. Brousmiche, J.M.J. Frechet, J. Am. Chem. Soc. 124 (2002)
11848–11849.
[24] J.M. Giaimo, A.V. Gusev, M.R. Wasielewski, J. Am. Chem. Soc. 124 (2002) 8530–
8531.
[25] B.A. Jones, M.J. Ahrens, M.H. Yoon, A. Facchetti, T.J. Marks, M.R. Wasielewski,
Angew. Chem. Int. Ed. 43 (2004) 6363–6366.
[26] M.J. Ahrens, M.J. Fuller, M.R. Wasilewski, Chem. Mater. 15 (2003) 2684–2686.
[27] C. Zhao, Y. Zhang, R. Li, R. Li, J. Jiang, J. Org. Chem. 72 (2007) 2402–2410.
[28] R. Raramasivan, C. Revital, S. Elijah, J.W. Linda, R. Boris, J. Org. Chem. 72 (2007)
5973–5979.
[29] F. Hadicke, F. Graser, Acta Crystallogr. Sect. C 42 (1986) 189–195.
[30] W. Su, Y. Zhang, C. Zhao, X. Li, J. Jiang, ChemPhysChem 8 (2007) 1857–1862.
[31] A. Dreuw, M. Head-Gordon, Chem. Rev. 105 (2005) 4009–4037.
4.1.7. N,N-dicyclohexyl-1-dodecyloxy-7-(1-(2-(4-ethynylphenyl)ethy-
nyl)-4-(2-phenylethynyl)benzene)perylene-3,4,9,10-tetracarboxy-
diimide (6)
Following the similar procedure of 4, with 3 as starting material,
compound 6 was prepared. Yield: 8.8 mg, (50%). 1H NMR (CDCl3),
(d: ppm): 9.87 (d, J = 8.2 Hz, 1H), 9.34 (d, 1H), 9.57 (s, 1H), 8.43
(m, 2H), 8.29 (s, 1H), 7.53 (m, 9H), 7.35 (m, 4H), 5.02 (m, 2H),
4.38 (m,2H), 2.60 (m, 4H), 2.16–1.27 (m, 36H), 0.86 (t, 3H); 13C
NMR (300 MHz CDCl3), (d: ppm): 163.4, 163.4, 163.3, 163.0,
157.3, 136.8, 133.7, 133.5, 132.8, 131.9, 131.7, 130.7, 128.5,
128.4, 128.0, 127.9, 127.5, 127.4, 127.1, 126.9, 124.3, 123.6,
123.3, 123.1, 122.7, 122.1, 121.8, 121.5, 119.6, 117.8, 117.2, 97.6,
93.2, 92.0, 91.5, 90.8, 89.1, 77.4, 76.9, 76.6, 70.5, 54.2, 54.1, 31.9,
29.7, 29.7, 29.5, 29.4, 29.3, 29.2, 29.1, 26.7, 26.3, 25.6, 22.7, 14.1;
MALDI-TOF MS (m/z): Calculated: 1039.3; Found: 1038.

D. Wang et al. / Journal of Molecular Structure 938 (2009) 245–253
253
[32] A. Dreuw, M. Head-Gordon, J. Am. Chem. Soc. 126 (2004) 4007–4016.
[33] Y. Wang, G. Wu, Acta Phys. Chim. Sin. 23 (2007) 1813–1818.
[34] Y. Wang, G. Wu, Acta Phys. Chim. Sin. 24 (2008) 552–560.
[35] M.J. Ahrens, L.E. Sinks, B. Rybtchinski, W. Liu, B.A. Jones, J.M. Giaimo, A.V.
Gusev, A.J. Goshe, D.M. Tiede, M.R. Wasielewski, J. Am. Chem. Soc. 126 (2004)
8284–8294.
[36] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J. A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M. W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision B.05, Gaussian, Inc., Pittsburgh, PA, 2003.
[37] S.I. Gorelsky, SWizard program. http://www.sg-chem.net/.