Structure–Property Relationships in Click-Derived Donor–Triazole–Acceptor Materials

Article abstract of DOI:10.1002/chem.201603510

To shed light on intramolecular charge-transfer phenomena in 1,2,3-triazole-linked materials, a series of 1,2,3-triazole-linked push–pull chromophores were prepared and studied experimentally and computationally. Investigated modifications include variati

Full text of DOI:10.1002/chem.201603510

DOI: 10.1002/chem.201603510
Full Paper
&
Charge Transfer
Structure–Property Relationships in Click-Derived Donor–Triazole–
Acceptor Materials
[
a]
[a]
[b]
[c]
[a]
Paul Kautny,* Dorian Bader, Berthold Stçger, Georg A. Reider, Johannes Frçhlich,
[a]
and Daniel Lumpi
Abstract: To shed light on intramolecular charge-transfer
phenomena in 1,2,3-triazole-linked materials, a series of
physical characterization of intramolecular charge-transfer
features revealed ambipolar behavior of the triazole linker,
depending on the substitution position. Furthermore, non-
centrosymmetric materials were subjected to second-har-
monic generation measurements, which revealed the high
nonlinear optical activity of this class of materials.
1,2,3-triazole-linked push–pull chromophores were prepared
and studied experimentally and computationally. Investigat-
ed modifications include variation of donor and/or acceptor
strength and linker moiety as well as regioisomers. Photo-
[
10]
Introduction
drawing and -donating groups, and 4) meta linkage of the
[10a,b,11]
two molecular subunits to lower conjugation.
Moreover,
Great efforts have been made in the design and synthesis of
novel organic push–pull molecules owing to a wide range of
technologically relevant applications. Bipolar organic materials,
consisting of an electron-donating and -withdrawing subunit,
are of crucial importance for organic light-emitting diodes
the choice of a specific linker moiety can be used effectively to
control the donor–acceptor exchange. However, these particu-
lar methods are often difficult to realize and/or require tedious
synthetic work.
In contrast, copper(I)-catalyzed azide–alkyne cycloaddition
(CuAAC) is a well-investigated, robust synthetic methodology
for joining two molecular subunits through 1,2,3-triazole for-
mation. Whereas CuAAC, which is generally regarded as the
[
1]
[2]
[3]
(
OLEDs), imaging, organic photovoltaics (OPVs), dyes, and
[
4]
[5]
nonlinear optical (NLO) materials for two-photon absorption
[
6]
or second-harmonic generation (SHG) to name a few. The
electronic structure and, as a consequence, intrinsic properties
of the individual molecules are dominated by the donor–
acceptor interaction through intramolecular charge transfer
[12]
most successful example of click chemistry, has been exten-
[12,13]
sively exploited in many fields of organic synthesis,
reports
on bipolar organic materials that incorporate 1,2,3-triazoles as
functional p-conjugated moieties are rare. Such synthesized
click-derived push–pull molecules have been employed as NLO
[
1a–c,5a,7]
(ICT).
Generally, the design of push–pull chromophores relies on
[
14]
[15]
a donor–p linker–acceptor architecture. Thus, the properties of
the materials can be modified by careful selection of donor
and/or acceptor units as well as by the modulation of the
degree of electronic exchange between the donor and accept-
materials, fluorophores, materials for two-photon absorp-
[16]
[17]
tion, fluorescent metal sensors, and electro-optical materi-
[18]
als. CuAAC provides an intriguingly simple possibility to join
various donor and acceptor combinations to establish the
1,2,3-triazole linker. However, the intrinsically weak electron-
[
1a,b,5a,6a]
or groups through the conjugated linker moiety.
To
[16,18a,19]
control ICT, molecular design offers a variety of specific linkage
accepting properties of the triazole
and influence on
3
[8]
modes, such as 1) the introduction of sp -hybridized bridges,
) twisted configurations of molecules that result from sterical-
ICT through the triazole linker have to be considered in the
molecular design of the materials. Although a significant influ-
ence of the triazole substitution pattern on the electrochemical
2
[
9]
ly demanding groups, 3) ortho linkage of the electron-with-
[15b–e,17e,20]
and photophysical properties has been reported,
no
extensive combinatorial study of a large set of donors and ac-
ceptors, including donor–acceptor exchange, can be found in
the literature.
[
a] P. Kautny, D. Bader, Prof. Dr. J. Frçhlich, Dr. D. Lumpi
Institute of Applied Synthetic Chemistry, TU Wien
Getreidemarkt 9/163, 1060 Vienna (Austria)
E-mail: paul.kautny@tuwien.ac.at
The aim of this work was to investigate the effects of donor
and/or acceptor variations, as well as of triazole substitution
pattern, on the photophysical properties of simple donor–tria-
zole–acceptor molecules and gain a detailed insight into ICT
phenomena to establish a structure–property relationship for
this particular molecular scaffold.
[b] Dr. B. Stçger
Institute of Chemical Technologies and Analytics, TU Wien
Getreidemarkt 9/164-SC, 1060 Vienna (Austria)
[
c] Prof. Dr. G. A. Reider
Photonics Institute, TU Wien
Gußhausstraße 27–29, 1040 Vienna (Austria)
Supporting information and the ORCID number(s) for the author(s) of this
article are available under http://dx.doi.org/10.1002/chem.201603510.
Chem. Eur. J. 2016, 22, 1 – 13
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copper source and sodium ascorbate for the in situ reduction
Results and Discussion
II
of Cu in a mixture of H O and tBuOH (1:1; Scheme 3). Applica-
2
Our investigations are based on a large matrix of donor–
acceptor molecules. We systematically increased donor (ben-
zene<anisole<dimethylaniline (DMA)) and acceptor (ben-
zene<pyridine<pyrimidine) strength to explore the ICT. More-
over, we examined the effects of donor–acceptor exchange, by
inverting the triazole substitution pattern. In the following dis-
cussion, the two groups of regioisomers are referred to as the
regular (electron donor at 1-N of the triazole linker) and invert-
ed (electron donor at 4-C of the triazole linker) linked series
tion of a reaction microwave (MW) reactor allowed for short re-
action times (30–60 min). Whereas reactions starting from
alkyne 2a proceeded with excellent yields (81–91%), a tenden-
cy towards lower yields (54–68%) was observed in the conver-
sion of electron-poor alkynes 2d and 2e (Scheme 3).
(Scheme 1). An overview of all synthesized materials is given in
Scheme 2.
Scheme 3. Synthesis of the 1,2,3-triazole-linked donor–acceptor materials
(
regular series).
In case of the inverted series, DMA was employed as the
sole donor, owing to its superior electron-donating properties
Scheme 4). The synthesis of pyridine- and pyrimidine-based
(
Scheme 1. Representation of the investigated 1,2,3-triazole-linked donor–
IIdc and IIec required the application of 2-azidopyridine (1d)
and 2-azidopyrimidine (1e). Whereas compound IIac could be
synthesized under standard click conditions (Scheme 4), this
methodology was not applicable for azides 1d and 1e be-
cause they were in a tautomeric equilibrium with the corre-
sponding ring-closed tetrazoles, and thus, exhibited significant-
acceptor materials.
Synthesis
By employing standard CuAAC conditions, the synthesis of the
regular series was accomplished by using CuSO ·5H O as the
4
2
Scheme 2. Overview of all materials under investigation.
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Scheme 5. Synthesis of the benzene-linked donor–acceptor materials.
cussion, all compounds are named according to the nomencla-
ture defined in Scheme 2. All materials based on the DMA
donor exhibited photoluminescence, with the exception of
PymTazDMA, whereas among the other materials weak emis-
sion was only observed in the case of AnTazPyr. To examine
the differences in the excited states of the compounds, photo-
luminescence spectra in eight solvents with increasing polarity
(cyclohexane, dibutyl ether, diisopropyl ether, diethyl ether, di-
chloromethane, butanol, ethanol, acetonitrile) have been re-
corded. However, in butanol and ethanol, no or only very weak
emission was obtained from triazole-linked materials that in-
corporated pyridine or pyrimidine units, probably owing to
specific protic interactions between the solvent and chromo-
Scheme 4. Synthesis of the 1,2,3-triazole-linked donor–acceptor materials
inverted series).
(
ly decreased reactivity. Single crystals of both tetrazoles were
obtained from solutions of 2d and 2e in CDCl upon slow
3
evaporation of the solvent.
Nevertheless, by utilizing Cu(OTf) (OTf=triflate) as catalyst
2
azides, compounds 1d and 1e could be reacted with 2c by
[21]
heating at reflux in toluene containing traces of benzene for
4–28 h to obtain IIdc and IIec in 68 and 12% yield, respec-
2
[15c,22]
tively (Scheme 4).
phores.
Key photophysical properties are summarized in
Additionally, a benzene-linked donor–acceptor series was
prepared to compare 1,2,3-triazole and benzene as linking
moieties. DMA was likewise employed as the sole electron-
donating group for this series and the strength of the electron
acceptor was varied. Synthesis of the benzene-linked materials
was realized in a Suzuki cross-coupling reaction starting from
boronic ester 3 and the corresponding brominated acceptor
moieties 4a, 4d, and 4e (Scheme 5).
Table 1 and all spectra of the individual compounds are given
in the Supporting Information.
First, compounds of the regular series were investigated.
Within this series, materials with a DMA donor unit exhibit sim-
ilar absorption spectra in dichloromethane with broad maxima
between l=302 and 309 nm. In contrast, the absorption pro-
files of materials with weaker donors seem to be predominate-
ly determined by the acceptor unit connected to the triazole
at the 4-position. Although BTazB and AnTazB feature struc-
tured absorptions with several shoulders between l=260 and
Photophysical characterization
290 nm, compounds BTazPyr and AnTazPyr exhibit a single
absorption maximum at l=287 nm, albeit with low intensity
in the case of BTazPyr. Pyrimidine-based BTazPym and AnTaz-
Pym feature one broad absorption peak at l=255 and
To explore the effects of the systematic structural modifications
on the photophysical properties of the materials, UV/Vis ab-
sorptions and emissions were recorded. In the following dis-
Table 1. Key photophysical properties of the materials.
[
a]
[a]
ꢀ1
ꢀ1
[a]
[a]
[b]
ꢀ1
l
abs [nm]
e
[m cm
]
l
PL,max [nm]
DEopt. [eV]
k
[cm ]
[
c]
[c]
[c]
[c]
[d]
BTazB
BTazPyr
BTazPym
AnTazB
250.5, 266 (sh), 272 (sh), 282 (sh), 289 (sh)
23140
4020
n.o.
n.o.
n.o.
n.o.
4.04
4.02
4.18
3.98
3.92
3.99
3.57
3.53
3.49
3.37
3.22
3.10
3.47
3.31
3.20
–
–
–
–
[
[
d]
d]
286.5
255
25120
25600
27180
24380
20940
23920
20020
34320
27640
30000
28480
27660
16760
[
c]
[c]
[c]
[c]
[d]
256, 267 (sh), 273 (sh), 282 (sh), 289 (sh)
AnTazPyr
AnTazPym
DMATazB
DMATazPyr
DMATazPym
DMABB
DMABPyr
DMABPym
BTazDMA
PyrTazDMA
PymTazDMA
287
263
286 (sh), 302
392.5
6087
–
[
d]
n.o.
396
[
c]
12729
22048
27609
13028
18636
20865
23228
26593
–
306
309
325
337
351
413.5
454
419.5
449
472
438
[
c]
270 (sh), 302
[
c]
[c]
[c]
[c]
271 (sh), 296, 305 (sh), 345 (sh)
268 (sh), 287, 310 (sh), 345 (sh)
470.5
[
c]
[c]
[d]
n.o.
[a] Determined in dichloromethane (5 mm). [b] Slope of the linear correlation of the Stokes shift with the solvent orientation polarizability determined from
the Lippert–Mataga plots. [c] Shoulder. [d] Not observed.
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Figure 2. Top: UV/Vis absorption spectra of DMABB, DMABPyr, and DMAB-
Pym in dichloromethane. Bottom: photoluminescence emission spectra of
DMABB in various solvents.
Figure 1. Top: UV/Vis absorption and photoluminescence emission spectra
of DMATazB in various solvents (DCM=dichloromethane, ACN=acetoni-
trile). Bottom: photoluminescence emission spectra of DMATazPyr and
DMATazPym in cyclohexane (g), dichloromethane (c), and acetonitrile
(
d).
The increasingly redshifted emission can be attributed to the
higher acceptor strength of pyridine and pyrimidine, and thus,
an increased degree of charge transfer upon photoexcitation.
Furthermore, an additional interesting emission feature was
observed for DMATazB. In polar acetonitrile, a second high-
energy emission band emerges at l=354 nm (Figure 1). Such
dual behavior is indicative of a mixed emission from a locally
excited (LE) and ICT state; a feature that has been previously
2
65 nm, respectively. Strikingly, the absorption onset, and thus,
optical band gap of materials of the regular series is solely de-
termined by the donor moiety and varies only insignificantly
within the respective groups. Although materials with a ben-
zene donor (BTazB, BTazPyr, BTazPym) exhibit optical band
gaps between l=297 and 308 nm, onset values of the anisole
derivatives are shifted to slightly higher wavelength (l=311–
[15b]
3
16 nm). In contrast, the absorption onsets of compounds
reported for structurally related chromophores.
with DMA donors are distinctly redshifted and located be-
tween l=347 and 356 nm.
As a second step, the benzene-linked compounds were ana-
lyzed to identify varied photophysical properties relative to the
regular series and correlate these alterations to the modified
linkage mode. In contrast to the regular series, the absorption
maxima and absorption onsets of benzene-linked materials are
not only dependent on the donor unit, but exhibit progressive
bathochromic shifts for stronger acceptor units (Figure 2). Ac-
cordingly, the absorption maxima of DMABB, DMABPyr, and
DMABPym in dichloromethane are located at l=325, 337,
and 351 nm; thus spanning a significantly larger range (26 nm
corresponding to 0.28 eV) than that of the regular series (7 nm,
0.09 eV). This particular behavior can be explained by a donor–
acceptor interaction in the ground state that is absent or dis-
tinctly reduced in the regular series. Moreover, the absorption
maximum of DMABB, which is the compound with the weak-
Whereas the absorption spectra are basically independent of
the solvent polarity, the emission spectra of DMA-substituted
materials of the regular series exhibit distinct solvatochromic
[
22]
effects, as typically observed for ICT emission. However, the
extent of the solvatochromic shift strongly depends on the
strength of the acceptor group (Figure 1). In cyclohexane, the
emission maxima of DMATazB, DMATazPyr, and DMATazPym
are vibronically resolved and located over a narrow range at
l=360, 361.5, and 368.5 nm. In contrast, they are shifted to
l=396, 413.5, and 454 nm in dichloromethane and l=402.5,
460.5, and 524.5 nm in acetonitrile, corresponding to an overall
redshift of 42.5, 99, and 156 nm from cyclohexane to acetoni-
trile for DMATazB, DMATazPyr, and DMATazPym, respectively.
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est electron-accepting moiety within the series, is redshifted
by 23 nm relative to that of the corresponding compound
DMATazB. The observation of an acceptor dependence and
overall redshift of the absorption are indicative of a higher
degree of conjugation in the benzene-linked donor–acceptor
materials. Thus, the incorporation of the triazole moiety in the
regular series effectively decreased the electronic conjugation
of the molecules in the ground state.
In analogy to the regular triazole series, all benzene-linked
materials exhibited distinct solvatochromism, as depicted for
DMABB in Figure 2. To provide a better insight into the solvent
dependency of the emission and for better comparability of
the different series the solvatochromic behavior of the materi-
[
23]
als the Lippert–Mataga equation [Eq. (1)] was applied:
2
2
ðm ꢀ m Þ
e
g
ð1Þ
ðn ꢀ n Þ ¼
Df þ const:
a
f
hca3
in which (n ꢀn ) is the Stokes shift, h is the Planck constant,
a
f
c is the speed of light, a is the solvent cavity (Onsager) radius,
and mg and m correspond to the ground- and excited-state
e
dipole moments, respectively. The orientation polarizability, Df,
as a measure of solvent polarity is related to the refractive
index by Equation (2):
2
e ꢀ 1
Df ¼ 2
n ꢀ 1
ꢀ
ð2Þ
2
e þ 1 2n þ 1
in which e is the dielectric constant and n is the refractive
index of the solvent. Equation (1) predicts a linear dependence
between the Stokes shift and solvent polarity, for which the
slope depends on the square of the dipole moment difference
of the ground and excited states, and thus, indicates the
degree of charge transfer upon photoexcitation. Because the
molecular weight and shape of the investigated molecules are
similar, slopes of the Lippert–Mataga plots are a direct measure
of charge transfer in the individual molecules.
Figure 3. Lippert–Mataga plots of DMATazB, DMATazPyr, and DMATazPym
(
top), as well as of DMABB, DMABPyr, and DMABPym (bottom).
ꢀ
1
and DMABPym (20865 cm ); this indicates a lower degree of
charge transfer.
From these findings, it can be concluded that the triazole
linker decreases conjugation in the ground state, but enhances
charge transfer upon photoexcitation. Notably, increased
charge transfer is only observed in acceptor-substituted DMA-
TazPyr and DMATazPym, whereas the charge-transfer proper-
ties of DMATazB are comparable to those of DMABB. Thus, it
can be concluded that the triazole linker increases the donor
strength of DMA, resulting in enhanced donor–acceptor inter-
action. The donor properties of the triazole linker can be ra-
tionalized by a contribution from mesomeric structure B
(Scheme 6) to the excited state, as previously suggested for
As seen in Figure 3, all materials indeed display a linear cor-
relation of the Stokes shift and solvent polarity and steeper
slopes were observed for materials that incorporated stronger
acceptor units due to increased charge transfer. However,
a comparison of both series unveils more complex behavior.
Compounds DMATazB and DMABB exhibit nearly identical
ꢀ
1
slopes of 12729 and 13028 cm ; these values indicate similar
degrees of charge transfer upon excitation. In contrast, the cor-
responding congeners with stronger acceptor units display dif-
ferent emission properties. Within the regular series, the slope
ꢀ
1
[15e,17d]
values are distinctly increased to 22048 and 27609 cm for
the pyridine and pyrimidine acceptors, respectively, which sug-
gests significantly enhanced charge transfer in these deriva-
tives. In contrast, and in analogy to the absorption maxima,
the benzene series exhibits an overall redshifted emission from
DMABB to DMABPyr to DMABPym, which is already evident
in cyclohexane. Furthermore, the additional redshift of the
emission of the individual acceptor-substituted molecules
caused by Dmeg is smaller than that of the regular series, as de-
metallochromic materials.
Finally, the photophysical properties of the inverted series
were determined. In contrast to the DMA-substituted deriva-
ꢀ
1
duced from the lower slope values of DMABPyr (18636 cm )
Scheme 6. Mesomeric structures of DMATazPyr and DMATazPym.
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Whereas BTazDMA and PyrTazDMA exhibit strong solvato-
chromic behavior, no photoluminescent emission was detected
for PymTazDMA. Emission maxima of BTazDMA and PyrTazD-
MA are redshifted relative to the corresponding derivatives of
the regular series; a feature that has been previously reported
[
15c]
for pairs of triazole regioisomers.
Strikingly, the value of the
ꢀ
1
slope for BTazDMA (23228 cm ) is significantly higher than
ꢀ
1
that of DMATazB (12729 cm ). The additional increase from
ꢀ
1
BTazDMA to PyrTazDMA (26593 cm ) is due to the stronger
electron-accepting moiety of the pyridine. However, it is dis-
tinctly lower than the corresponding two derivatives of the
regular series. From the observation of a strong solvatochromic
effect for BTazDMA without an additional acceptor unit, and
the moderated increase of solvatochromism for the pyridine-
substituted derivative PyrTazDMA, it can be concluded that
the triazole itself operates as an electron-accepting moiety in
the inverted series.
In summary, these investigations revealed that the triazole
linkage significantly decreased conjugation in the ground
state, but increased charge-transfer phenomena upon photo-
excitation due to an enhancement of donor or acceptor prop-
erties. The kind of electronic interaction triggered by the ambi-
polar triazole moiety, in turn, can be controlled by the triazole
substitution pattern.
Theoretical calculations
To gain further insight into the electronic properties of the in-
vestigated materials, theoretical studies applying DFT have
been performed. The spatial distribution of the HOMOs and
LUMOs of the compounds are depicted in Figure 5 and the
Supporting Information.
Figure 4. Top: UV/Vis absorption and photoluminescence emission spectra
of PyrTazDMA in various solvents. Bottom: Lippert–Mataga plots of DMA-
TazB, DMATazPyr, BTazDMA, and PyrTazDMA.
HOMOs and LUMOs are uniformly distributed over the
whole molecules in materials without strong acceptor and/or
donor units. In contrast, increasing spatial separation can be
found for materials with distinctive donor–acceptor combina-
tions. This spatial separation of the HOMO and LUMO is indica-
tive of a charge-transfer process upon photoexcitation, as de-
scribed in the spectroscopic section. However, looking at the
DMA-substituted congeners in detail, a more complex situation
is observed (Figure 5). In DMABPym, the HOMO and LUMO are
mainly located on the DMA and pyrimidine units, respectively,
tives of the regular series, all materials of the inverted series
display structured absorption spectra in solvents with low po-
larity, whereas the individual peaks diminish with increasing
solvent polarity, as depicted for PyrTazDMA in Figure 4 as an
example. In analogy to the benzene series, the absorption
onsets of the inverted materials are gradually redshifted from
BTazDMA to PyrTazDMA and PymTazDMA; this indicates
a donor–acceptor interaction in the ground state that is not
present in the regular series.
Figure 5. Spatial distribution of HOMO and LUMO levels of DMABPym, DMATazB, DMATazPym, BTazDMA, and PymTazDMA.
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Table 2. Key crystallographic properties, supramolecular features, and relative SHG yields of the compounds under investigation.
Space
group
Centro-
symmetry
Weak hydrogen bonds
p–p interactions
Relative SHG
yield
[a]
Taz!Taz
Taz !Pym
Pym!Taz
Pym!Pym
Head–tail
Head–head
[
25]
BTazB
BTazPyr
C2/c
yes
yes
no
no
no
yes
yes
no
yes
yes
yes
yes
chains
chains
chains
chains
chains
–
–
80
3.4
6.0
–
–
0.2
–
–
–
[
26]
P2
Cc
P2
P2
P2
P2
P2
P2
P1¯
1
/n
BTazPym
AnTazB
AnTazPyr
AnTazPym
DMATazB
DMATazPyr
DMATazPym
BTazDMA
PyrTazDMA
PymTazDMA
chains
chains
chains
1
1
1
1
1
1
2
2
/c
1
2
2
1
1
1
chains
chains
[
27]
/n
chains
[
28]
pairs
pairs
[
b]
/c
pairs
pairs
chains
pairs
chains
chains
[
27]
[
[
b]
b]
P2
P2
1
/c
/c
pairs
pairs
1
–
[a] Relative to potassium dihydrogen phosphate (KDP). [b] Formed by pairs of molecules.
[
27]
but spread over the whole molecule and significant electron
density is located on the opposite end of the molecule. A
higher degree of separation is observed in DMATazPym and
PymTazDMA, which indicates increased charge-transfer fea-
tures; this is in agreement with experimental findings. In par-
ticular, the LUMO level of PymTazDMA is localized on the pyri-
midine and triazole rings. This kind of localization was also
found for the LUMO of BTazDMA. Likewise, the HOMO level of
BTazDMA is confined to the DMA and triazole units. Thus, the-
oretical calculations suggest a pronounced charge transfer in
BTazDMA, which is in agreement with spectroscopic character-
ization. In contrast, no such separation is observed in the cor-
responding derivative of the regular series, DMATazB. There-
fore, this particular electronic layout can be directly attributed
to the altered substitution of the triazole linker. A strong locali-
zation of the LUMO in BTazDMA in the absence of a strong
electron-withdrawing unit indicates the establishment of an
electron-accepting moiety at the benzene–triazole fragment.
This particular behavior can be attributed to the substitution
pattern of the triazole due to the absence of any other molec-
ular modifications and is again in agreement with spectroscop-
ic characterization.
being aware of the previously published structural data. Key
crystallographic properties of the materials are summarized in
Table 2.
Compound DMATazPyr is made up of Z’=4 crystallographi-
cally independent molecules. All other structures are made up
of one independent molecule, located on a general position.
Notably, common structural features were observed in some of
the derivatives.
Compounds AnTazB and AnTazPyr are isostructural, which
shows that pyridine can be used as a substitute for benzene.
Likewise, compounds DMATazPym, PymTazDMA, and Pyr-
TazDMA are isostructural, which shows that the substitution
pattern of the triazole linker can be inverted and pyridine can
be substituted by pyrimidine, without affecting the structure
type. Whereas the inversion of the triazole has virtually no
impact on the structure, additional hydrogen in the pyridine
ring imposes a distinct stretching in the [100] direction (DMA-
TazPym: a=8.4266(7) ꢁ, PymTazDMA: a=8.5714(5) ꢁ, Pyr-
TazDMA: a=9.1392(8) ꢁ). A more surprising structural relation-
ship is observed for BTazPyr and DMATazB. Although the di-
methylamine group in DMATazB requires additional space
3
3
(BTazPyr: V=1078.45 ꢁ , DMATazB: V=1315.84 ꢁ ), both
structures can still be considered as isostructural (Figure S4.1 in
the Supporting Information). The remaining structures (BTazB,
BTazPym, AnTazPym, DMATazPyr, and BTazDMA) are unique.
Supramolecular features constitute, on one hand, weak hy-
drogen bonds of the triazole and pyrimidine hydrogen atoms,
and, on the other hand, p–p interactions of the aromatic rings,
as summarized in Table 2. The most commonly observed fea-
ture is hydrogen bonding connecting triazole moieties, form-
ing infinite chains, for example, as in BTazPyr (Figure 6, left).
Triazole to pyrimidine and pyrimidine to pyrimidine hydrogen
bonds are only observed in AnTazPym (chains, Figure 6, right).
Pyrimidine to triazole hydrogen bonds exist only in DMATaz-
Pym and PymTazDMA to form pairs of molecules. The absence
of this particular intermolecular bonding in isostructural Pyr-
TazDMA proves that these weak hydrogen bonds are not
structure determining.
Crystallography and NLO properties
Recently, our group reported a novel class of NLO-active mate-
[
14]
rials with high SHG yields.
These materials are based on
click-functionalized ene–yne compounds with an 1,2,3-triazole
linker as an essential building block. To further explore the
scope of this class of materials, we investigated our present
compounds with regard to their SHG efficiency. Because SHG
[
24]
requires non-centrosymmetric crystallization, single crystals
of all triazole-linked materials were subjected to single-crystal
XRD. Unfortunately, no usable crystals could be grown for the
[25]
benzene-linked series. The crystal structures of BTazB, BTaz-
[
26]
[27]
[28]
[27]
Pyr, DMATazB, DMATazPyr, and BTazDMA are known
from the work of other groups. Additionally, we grew crystals
and determined the structures of AnTazB, AnTazPym, AnTaz-
Pyr, BTazPym, DMATazPym, PymTazDMA, and PyrTazDMA.
Moreover, we redetermined the structure of DMATazB, not
The p–p interactions are observed in DMATazPyr (pairs) and
DMATazPym, PymTazDMA, and PyrTazDMA. In the last of
Chem. Eur. J. 2016, 22, 1 – 13
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7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Figure 6. Supramolecular arrangement of BTazPyr (left) and AnTazPym (right) molecules in chains connected through Taz!Taz hydrogen bonds (BTazPyr) or
Taz !Pym and Pym!Taz hydrogen bonds (AnTazPyr). Carbon, nitrogen, and oxygen atoms are represented by light gray, dark gray, and striped spheres of
arbitrary radius. Hydrogen atoms not involved in hydrogen bonding are omitted for clarity. Hydrogen bonds are indicated by dashed lines.
larizability in the donor–acceptor materials is predominantly
[29]
determined by ICT features.
Conclusion
We have synthesized a complete set of 1,2,3-triazole-linked
donor–acceptor materials and provided a thorough photo-
physical and theoretical characterization. Our findings reveal
an intriguing relationship between intramolecular charge-
transfer properties and triazole substitution patterns in donor–
acceptor materials. Accordingly, triazole can be utilized not
only as a linker unit, but also to increase either the electron-
donating properties of the donor or to establish electron-
accepting properties in a conjugated system without a defined
acceptor moiety. Thus, our investigations provide guidelines
for the incorporation of the 1,2,3-triazole unit as a linker in
conjugated materials and are of great importance for the
design of new functional click-derived materials for manifold
applications.
Figure 7. Supramolecular arrangement of DMATazPym determined by inter-
molecular p–p interactions. Colors are the same as those used in Figure 6.
Intermolecular CꢀC contacts in the 3.3–3.4 ꢁ range are indicated by dashed
lines.
these, the resulting pairs are also connected by head-to-head
p–p interactions (through pyrimidine/pyridine) to chains
(Figure 7). Head-to-head p–p interactions through the benzene
rings are also observed in BTazDMA; these form pairs of mole-
cules. However, no intermolecular interaction between pairs is
observed. Finally, the BTazPym, AnTazB, and AnTazPyr mole-
cules are connected through head-to-tail p–p interactions to
chains (Figure S4.2 in the Supporting Information).
Experimental Section
All materials that crystallize as non-centrosymmetric crystals
were investigated regarding their capability of SHG. The strong
dependence of the macroscopic SHG yield on the exact align-
ment of the individual molecules with respect to the symmetry
elements of the crystal has to be taken into account when dif-
X-ray structure determination
Crystals of BTazPym (hexane/EtOH=100:1), AnTazB (EtOH), AnTaz-
Pyr (hexane), AnTazPym (EtOH), DMATazB (EtOH), DMATazPym
(EtOH), PyrTazDMA (EtOH), and PymTazDMA (EtOH) were crystal-
[
29]
ferent materials are compared.
However, in the case of
lized from saturated boiling solvents. XRD intensities were collect-
AnTazB and AnTazPyr, isostructural crystallization allows for
the direct comparison of the two materials. Whereas AnTazB
exhibits a SHG efficiency of 3.4 times the value of KDP, this
value is higher for AnTazPyr (6.0ꢂKDP). In analogy to DMA-
substituted materials, stronger charge-transport features can
be expected for AnTazPyr than those of AnTazB, owing to the
presence of the pyridine acceptor. Thus, the increased SHG effi-
ed at T=100 K in a dry stream of nitrogen on Bruker Smart APEX
(AnTazPym and DMATazPym) or Bruker Kappa APEX II (all other)
diffractometer systems by using graphite-monochromatized MoKa
radiation (l=0.71073 ꢁ) and fine-sliced f and w scans. Data were
[30]
reduced to intensity values with SAINT and an absorption correc-
tion was applied with the multiscan approach implemented in
[30]
SADABS. The structures were solved by charge flipping by using
[31]
[32]
SUPERFLIP and refined against F with JANA2006. Non-hydro-
gen atoms were refined anisotropically. The hydrogen atoms were
placed in calculated positions and thereafter refined as riding on
the parent atoms. Owing to a lack of anomalous scatterers, the
Friedel opposites of non-centrosymmetric crystals were merged
and the absolute structure was not determined. Molecular graphics
ciency directly reflects the increased Dm value, as predicted
eg
[
29]
by the two-state model. Investigation of the NLO properties
of BTazPym revealed a significantly higher SHG yield of
80 times the value of KDP. We could therefore further improve
the NLO performance compared with the most efficient click-
functionalized thiophene- or selenophene-ring fragmenta-
[33]
were generated with the program MERCURY.
CCDC 1471390 (AnTazB), 1471391 (AnTazPym), 1471392 (AnTaz-
Pyr), 1471393 (BTazPym), 1471394 (DMATazB), 1471395 (DMATaz-
Pym), 1471396 (PymTazDMA), and 1471397 (PyrTazDMA) contain
the supplementary crystallographic data for this paper. These data
are provided free of charge by The Cambridge Crystallographic
Data Centre.
[
14b]
tion
products reported previously by our group. Hence, our
investigations further expand the scope of click-derived materi-
als for NLO applications. In particular, the inverted triazole ar-
chitecture, which ensures high Dm , provides an appealing
eg
strategy in the design of new NLO materials because hyperpo-
&
&
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SHG measurements
extracted with DCM. The combined organic layers were dried over
Na SO and concentrated under reduced pressure. Purification of
the crude product was accomplished by filtration over a small
amount of silica gel.
2
4
Second-order NLO properties of the substances were studied with
second-harmonic measurements from powder samples. Powdered
samples of the materials with a grain size of less than 1 mm were
prepared with a mortar. A relative measurement of the NLO coeffi-
cients was possible with this technique because the second-har-
monic efficiency scaled quadratically with the nonlinear coefficient,
providing that the particle size was significantly less than the non-
linear coherence length (which was more than 10 mm in all practi-
BTazB: Starting from ethynylbenzene (2a; 255 mg, 2.50 mmol,
1
.00 equiv), 1a (298 mg, 2.50 mmol, 1.00 equiv), CuSO ·5H O
4 2
(125 mg, 0.50 mmol, 0.2 equiv), and sodium ascorbate (198 mg,
1
.00 mmol, 0.40 equiv), BTazB (506 mg, 91%) was obtained as
1
[34]
a yellow solid. M.p. 181.0–182.38C; H NMR (400 MHz, CD
.27 (s, 1H), 7.92 (d, J=8.1 Hz, 2H), 7.81 (d, J=8.1 Hz, 2H), 7.58
dd, J=8.0 Hz, 7.3 Hz, 2H), 7.51–7.45 (m, 3H) 7.37 ppm (t, J=
Cl ): d=
2 2
cal cases). Subsequently, the powders were positioned between
two microscope slides and irradiated with the output of an ultra-
fast Yb:KGW-Laser (Light Conversion, pulse duration 70 fs, average
power 600 mW, repetition rate 75 MHz, wavelength l=1034 nm),
moderately focused with a 100 mm focusing lens. The diffusely re-
flected second-harmonic radiation was collected with a NA=0.1
lens, separated from fundamental radiation with a color filter, and
spectrally analyzed with a 0.25 m grating monochromator and
a photomultiplier detector. The sample plane was positioned
somewhat out of the focal plane (towards the lens) to prevent any
damage to the sample. After each measurement, the samples were
carefully checked for the absence of damage or thermal modifica-
tion. For quantification of the SHG yields, (Z)-4-(2-(methylthio)-1-
8
(
7
1
13
.3 Hz, 1H); C NMR (100 MHz, CD Cl ): d=148.7, 137.7 131.0,
2 2
30.3, 129.5, 129.3, 128.9, 126.2, 121.0, 118.4 ppm; HRMS (ESI): m/z
+
+
calcd for C H N : 221.09475 [M] , 222.10257 [M+H] , 244.08452
14
11
3
+
+
+
[M+Na] ; found: 221.09438 [M] , 222.10196 [M+H] , 244.08379
+
[M+Na] .
AnTazB: Starting from 2a (153 mg, 1.50 mmol, 1.00 equiv), 1b
(
224 mg, 1.50 mmol, 1.00 equiv), CuSO ·5H O (75 mg, 0.30 mmol,
4 2
0
.2 equiv), and sodium ascorbate (119 mg, 0.60 mmol, 0.40 equiv),
AnTazB (339 mg, 90%) was obtained as a white solid. M.p. 165.5–
1
[14a]
166.88C; H NMR (400 MHz, CD Cl ): d=8.17 (s, 1H), 7.90 (d, J=
propenyl)-1-phenyl-1,2,3-triazole
was employed as a reference
2
2
8
7
.2 Hz, 2H), 7.70 (d, J=9.0 Hz, 2H), 7.46 (dd, J=8.2 Hz, 7.4 Hz, 2H),
.37 (t, J=7.4 Hz, 1H), 7.06 (d, J=9.0 Hz, 2H), 3.87 ppm (s, 3H);
C NMR (100 MHz, CD Cl ): d=160.5, 148.5, 131.2, 131.1, 129.5,
material (SHG yield of reference=SHG yield of KDPꢂ2).
1
3
2
2
Synthesis
1
28.8, 126.2, 122.7, 118.6, 115.3, 56.2 ppm; HRMS (ESI): m/z calcd
+
+
for C H N O: 251.10531 [M] , 252.11314 [M+H] , 274.09508 [M+
Na] ; found: 251.10486 [M] , 252.11195 [M+H] , 274.09465 [M+
Na] .
15
13
3
All reagents and solvents were purchased from commercial suppli-
ers and used without further purification. Azidobenzene (1a), 1-
azido-4-methoxybenzene (1b),
+
+
+
[
35]
+
[
36]
4-azido-N,N-dimethylbenzena-
4-ethynyl-N,N-dimethylbenzenamine
[36]
[37]
[37]
mine (1c),
1d,
2c), 2-ethynylpyridine (2d), 2-ethynylpyrimidine (2e), N,N-
dimethyl-4’-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-[1,1’-bi-
1e,
[38]
[38]
[38]
DMATazB: Starting from 2a (112 mg, 1.10 mmol, 1.00 equiv), 1c
(
(178 mg, 1.10 mmol, 1.00 equiv), CuSO ·5H O (55 mg, 0.22 mmol,
4 2
[39]
0.20 equiv), and sodium ascorbate (87 mg, 0.44 mmol, 0.40 equiv),
phenyl]-4-amine (3) were prepared in analogy to published pro-
cedures and the physical data of the prepared materials was com-
pared with literature values. Anhydrous solvents were prepared by
filtration through drying columns. Column chromatography was
performed on silica 60 gel (Merck, 40–63 mm). Experiments under
MW irradiation were performed in a Biotage Initiator Sixty MW re-
actor. Melting points were determined by using a MPA100 Opti-
Melt automated melting point system from Stanford Research Sys-
tems. NMR spectra were recorded on a Bruker Avance DRX-400
spectrometer. A Thermo Scientific LTQ Orbitrap XL hybrid Fourier
transform mass spectrometer equipped with a Thermo Fischer Ex-
active Plus Orbitrap (LC-ESI+) and a Shimadzu IT-TOF mass spec-
trometer were used for HRMS. UV/Vis absorption and fluorescence
emission spectra in solution (5 mm) were recorded with a PerkinElm-
er Lambda 750 spectrometer and an Edinburgh FLS920 instrument,
respectively. DFT calculations were performed by using the Gaussi-
DMATazB (236 mg, 81%) was obtained as a yellow solid. M.p.
1
1
68.1–169.48C; H NMR (400 MHz, CD Cl ): d=8.13 (s, 1H), 7.90 (d,
2
2
J=8.1 Hz, 2H), 7.60 (d, J=9.0 Hz, 2H), 7.46 (dd, J=8.1 Hz, 7.4 Hz,
2
6
1
H), 7.36 (t, J=7.4 Hz, 1H), 6.81 (d, J=9.0 Hz, 2H), 3.02 ppm (s,
13
H); C NMR (100 MHz, CD Cl ): d=151.3, 148.2, 131.4, 129.4,
2
2
28.6, 127.2, 126.2, 122.3, 118.4, 112.8, 40.8 ppm; HRMS (ESI): m/z
+
+
calcd for C H N : 264.13695 [M] , 265.14477 [M+H] , 287.12672
16 16
4
+
+
+
[M+Na] ; found: 264.13679 [M] , 265.14342 [M+H] , 287.12584
+
[M+Na] .
BTazPyr: Starting from 2d (113 mg, 1.10 mmol, 1.00 equiv), 1a
(131 mg, 1.10 mmol, 1.00 equiv), CuSO ·5H O (55 mg, 0.22 mmol,
4
2
0.20 equiv), and sodium ascorbate (87 mg, 0.44 mmol, 0.40 equiv),
BTazPyr (148 mg, 61%) was obtained as a yellow solid. M.p. 90.7–
1
92.08C; H NMR (400 MHz, CD Cl ): d=8.63 (s, 1H), 8.60 (d, J=
2
2
[40]
an 09 package. applying the Becke three-parameter hybrid func-
4.7 Hz, 1H), 8.21 (d, J=8.0 Hz, 1H), 7.85–7.80 (m, 3H), 7.57 (dd, J=
8.3 Hz, 7.6 Hz, 2H), 7.48 (t, J=7.6 Hz, 1H), 7.27 ppm (dd, J=7.6,
[41]
tional with Lee–Yang–Perdew correlation (B3LYP) in combination
[42]
13
with Pople basis sets 6-31G(d,p). Geometry optimizations were
performed in the gas phase and without symmetry constraints. Or-
4.7 Hz, 1H); C NMR (100 MHz, CD Cl ): d=150.7, 150.2, 149.6,
2
2
137.7, 137.4, 130.4, 129.4, 123.6, 121.0, 120.7, 120.6 ppm; HRMS
[43]
+
+
bital plots were generated by using GaussView.
(ESI): m/z calcd for C H N : 222.09000 [M] , 223.09782 [M+H] ,
13 10 4
+
+
+
2
2
45.07977 [M+Na] ; found: 222.08914 [M] , 223.09716 [M+H] ,
+
45.07908 [M+Na] .
General procedure for CuAAC
CuSO ·5H O (0.2 equiv) and sodium ascorbate (0.4 equiv) were
added to a solution of alkyne (1.0 equiv) and azide (1.0 equiv) in
AnTazPyr: Starting from 2d (105 mg, 1.02 mmol, 1.00 equiv), 1b
(152 mg, 1.02 mmol, 1.00 equiv), CuSO ·5H O (51 mg, 0.20 mmol,
4
2
4
2
H O/tBuOH (1:1; ca. 0.4m) in a MW reaction vial immediately
2
0.20 equiv), and sodium ascorbate (81 mg, 0.41 mmol, 0.40 equiv),
before the vial was sealed and the reaction mixture was heated to
AnTazPyr (141 mg, 55%) was obtained as an orange solid. M.p.
1
1
508C until full conversion (TLC; 30–60 min). The resulting precipi-
127.9–128.48C; H NMR (400 MHz, CD Cl ): d=8.59 (d, J=4.7 Hz,
2
2
tate was dissolved in H O and DCM and the aqueous phase was
1H), 8.53 (s, 1H), 8.20 (d, J=8.1 Hz, 1H), 7.81 (dd, J=8.1, 7.4 Hz,
2
Chem. Eur. J. 2016, 22, 1 – 13
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9
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1
3
1
9
1
5
2
2
H), 7.72 (d, J=9.2 Hz, 2H), 7.26 (d, J=7.4, 4.7 Hz, 1H), 7.06 (d, J=
1H), 6.80 (d, J=8.9 Hz, 2H), 3.00 ppm (s, 6H); C NMR (100 MHz,
CD Cl ): d=151.3, 149.3, 137.9, 130.3, 129.0, 127.2, 120.9, 118.8,
13
.2 Hz, 2H), 3.87 ppm (s, 3H); C NMR (100 MHz, CD Cl ): d=160.6,
2
2
2
2
50.8, 150.1, 149.4, 137.4, 131.1, 123.5, 122.6, 120.8, 120.6, 115.4
116.7, 112.9, 40.8 ppm; HRMS (ESI): m/z calcd for C H N :
16 16 4
264.13695 [M] , 265.14477 [M+H] , 287.12672 [M+Na] ; found:
264.13640 [M] , 265.14382 [M+H] , 287.12537 [M+Na] .
+
+
+
+
6.2 ppm; HRMS (ESI): m/z calcd for C H N O: 252.10056 [M] ,
1
+
4
12
4
+
+
+
+
+
53.10839 [M+H] , 275.09033 [M+Na] ; found: 252.10027 [M] ,
+
+
53.10734 [M+H] , 275.08946 [M+Na] .
PyrTazDMA
DMATazPyr: Starting from 2d (88 mg, 0.85 mmol, 1.00 equiv), 1c
The synthesis of PyrTazDMA was accomplished according to a pub-
(
0
138 mg, 0.85 mmol, 1.00 equiv), CuSO ·5H O (42 mg, 0.17 mmol,
4 2
.20 equiv), and sodium ascorbate (67 mg, 0.34 mmol, 0.40 equiv),
[21]
lished procedure.
Compounds 1d (180 mg, 1.50 mmol,
1
.00 equiv), 2c (240 mg, 1.65 mmol, 1.10 equiv), and Cu(OTf)2
DMATazPyr (121 mg, 54%) was obtained as a yellow solid. M.p.
1
(108 mg, 0.30 mmol, 0.20 equiv) in toluene (6 mL, abs. degassed)
and benzene (11 mg) were heated to reflux for 28 h. The reaction
1
1
1
9
1
4
2
2
50.7–151.58C; H NMR (400 MHz, CD Cl ): d=8.59 (d, J=4.7 Hz,
2 2
H), 8.48 (s, 1H), 8.19 (d, J=8.1 Hz, 1H), 7.80 (dd, J=8.1, 7.4 Hz,
H), 7.62 (d, J=9.4 Hz, 2H), 7.25 (d, J=7.4, 4.7 Hz, 1H), 6.81 (d, J=
mixture was poured on H O and extracted with DCM. Subsequent-
2
13
ly, the combined organic layers were dried over Na SO and con-
.2 Hz, 2H), 3.02 ppm (s, 6H); C NMR (100 MHz, CD Cl ): d=151.3,
2
4
2
2
centrated under reduced pressure. The crude product was purified
51.0, 150.1, 149.1, 137.3, 127.1, 123.3, 122.2, 120.6, 120.5, 112.8,
+
by column chromatography (DCM/Et O, 2%) to yield PyrTazDMA
0.8 ppm; HRMS (ESI): m/z calcd for C H N : 265.13220 [M] ,
2
1
+
5
15
5
1
+
+
(269 mg, 68%) as a yellow solid. M.p. 154.8–156.78C; H NMR
66.14002 [M+H] , 288.12197 [M+Na] ; found: 265.13254 [M] ,
+
+
(400 MHz, CD Cl ): d=8.68 (s, 1H), 8.52 (d, J=4.7 Hz, 1H), 8.20 (d,
66.13866 [M+H] , 288.12122 [M+Na] .
2
2
J=8.2 Hz, 1H), 7.94 (dd, J=8.2, 7.4 Hz, 1H), 7.79 (d, J=9.0 Hz, 2H),
7
6
1
.36 (d, J=7.4, 4.7 Hz, 1H), 6.80 (d, J=9.2 Hz, 2H), 3.00 ppm (s,
BTazPym: Starting from 2e (156 mg, 1.50 mmol, 1.00 equiv), 1a
13
H); C NMR (100 MHz, CD Cl ): d=151.3, 150.0, 149.1, 148.9,
2
2
(
179 mg, 1.50 mmol, 1.00 equiv), CuSO ·5H O (75 mg, 0.30 mmol,
4 2
39.6, 127.2, 123.9, 118.8, 115.6, 114.1, 112.9, 40.8 ppm; HRMS (ESI):
0
.20 equiv), and sodium ascorbate (119 mg, 0.60 mmol, 0.40 equiv),
+
+
m/z calcd for C H N : 265.13220 [M] , 266.14002 [M+H] ,
288.12197 [M+Na] ; found: 265.13243 [M] , 266.13860 [M+H] ,
15
15
5
BTazPym (209 mg, 62%) was obtained as a yellow solid. M.p.
+
+
+
1
1
2
2
50.8–154.28C; H NMR (400 MHz, CD Cl ): d=8.83 (d, J=4.9 Hz,
2 2
+
2
88.12115 [M+Na] .
H), 8.74 (s, 1H), 7.84 (d, J=8.9 Hz, 2H), 7.58 (dd, J=8.9 Hz, 7.4 Hz,
H), 7.50 (t, J=7.4 Hz, 1H), 7.27 ppm (t, J=4.9 Hz, 1H); C NMR
13
(
100 MHz, CD Cl ): d=159.6, 158.1, 148.6, 137.5, 130.4, 129.6, 123.7,
PymTazDMA
2
2
1
21.1, 120.4 ppm; HRMS (ESI): m/z calcd for C H N : 223.08525
12 9 5
The synthesis of PymTazDMA was accomplished according to
+
+
+
[M] , 224.09307 [M+H] , 246.07502 [M+Na] ; found: 223.08420
[21]
a published procedure.
.00 equiv), 2c (208 mg, 1.43 mmol, 1.10 equiv), and Cu(OTf)2
94 mg, 0.26 mmol, 0.20 equiv) in toluene (6 mL, abs. degassed)
Compounds 1e (157 mg, 1.30 mmol,
+
+
+
[M] , 224.09245 [M+H] , 246.07437 [M+Na] .
1
(
AnTazPym: Starting from 2e (141 mg, 1.35 mmol, 1.00 equiv), 1b
and benzene (3 drops) were heated to reflux for 24 h. The reaction
(
201 mg, 1.35 mmol, 1.00 equiv), CuSO ·5H O (67 mg, 0.27 mmol,
4 2
mixture was poured on H O and extracted with DCM. Subsequent-
2
0
.20 equiv), and sodium ascorbate (107 mg, 0.54 mmol, 0.40 equiv),
ly, the combined organic layers were dried over Na SO and con-
2
4
AnTazPym (216 mg, 63%) was obtained as a beige solid. M.p.
centrated under reduced pressure. The crude product was purified
1
1
2
7
62.1–163.48C; H NMR (400 MHz, CD Cl ): d=8.82 (d, J=4.8 Hz,
2 2
by column chromatography (DCM/Et O, 25%) to yield PymTazDMA
2
H), 8.65 (s, 1H), 7.73 (d, J=9.1 Hz, 2H), 7.25 (t, J=4.8 Hz, 1H),
1
(
(
40 mg, 12%) as a yellow solid. M.p. 2128C (dec); H NMR
400 MHz, CD Cl ): d=8.87 (d, J=4.8 Hz, 2H), 8.69 (s, 1H), 7.80 (d,
13
.07 (d, J=9.1 Hz, 2H), 3.87 ppm (s, 3H); C NMR (100 MHz,
2
2
CD Cl ): d=160.7, 159.7, 158.1, 148.3, 130.8, 123.8, 122.7, 120.3,
2
2
J=9.0 Hz, 2H), 7.40 (t, J=4.8 Hz, 1H), 6.81 (d, J=9.0 Hz, 2H),
115.4, 56.2 ppm; HRMS (ESI): m/z calcd for C H N O: 253.09581
13
1
+
3
11
5
3.01 ppm (s, 6H); C NMR (100 MHz, CD Cl ): d=159.8, 155.2,
2
2
+
+
[M] , 254.10364 [M+H] , 276.08558 [M+Na] ; found: 253.09527
1
51.4, 148.9, 127.3, 121.1, 118.3, 117.1, 112.9, 40.7 ppm; HRMS (ESI):
+
+
+
[M] , 254.10248 [M+H] , 276.08474 [M+Na] .
+
+
m/z calcd for C H N : 266.12745 [M] , 267.13527 [M+H] ,
2
289.11658 [M+Na] .
1
4
+
14
6
+
+
89.11722 [M+Na] ; found: 266.12788 [M] , 267.13403 [M+H] ,
+
DMATazPym: Starting from 2e (135 mg, 1.30 mmol, 1.00 equiv), 1c
(
211 mg, 1.30 mmol, 1.00 equiv), CuSO ·5H O (65 mg, 0.26 mmol,
4 2
0
.20 equiv), and sodium ascorbate (103 mg, 0.52 mmol, 0.40 equiv),
General procedure for the Suzuki cross-coupling reactions
DMATazPym (234 mg, 68%) was obtained as a brown solid. M.p.
1
2
2
6
01.8–202.98C; H NMR (400 MHz, CD Cl ): d=8.81 (d, J=4.9 Hz,
Arylbromide (1.00 equiv), 3 (1.00 equiv), K CO (2.50 equiv, 2m de-
2
2
2
3
H), 8.60 (s, 1H), 7.63 (d, J=9.2 Hz, 2H), 7.24 (t, J=4.9 Hz, 1H),
gassed aqueous solution), and [Pd(PPh ) ] (2.5 mol%) were added
3 4
13
.81 (d, J=9.2 Hz, 2H), 3.02 ppm (s, 6H); C NMR (100 MHz,
to degassed THF (50 mm). The mixture was heated to reflux under
an argon atmosphere until full conversion (TLC, ca. 20 h). Subse-
quently, the solvent was evaporated and the residue was dissolved
CD Cl ): d=159.9, 158.0, 151.4, 148.0, 126.9, 123.5, 122.3, 120.2,
2
2
112.7, 40.8 ppm; HRMS (ESI): m/z calcd for C H N : 266.12745
14 14 6
+
+
+
[M] , 267.13527 [M+H] , 289.11722 [M+Na] ; found: 266.12824
in DCM and H O. The aqueous phase was repeatedly extracted
2
+
+
+
[M] , 267.13384 [M+H] , 289.11640 [M+Na] .
with DCM, the combined organic layers were dried over anhydrous
Na SO , and the solvent was removed in vacuo after filtration.
2
4
BTazDMA: Starting from 2c (232 mg, 1.60 mmol, 1.00 equiv), 1a
(
192 mg, 1.60 mmol, 1.00 equiv), CuSO ·5H O (80 mg, 0.32 mmol,
DMABB: Starting from bromobenzene (4a; 196 mg, 1.25 mmol,
4
2
0
.20 equiv), and sodium ascorbate (127 mg, 0.64 mmol, 0.40 equiv),
1.00 equiv), 3 (404 mg, 1.25 mmol, 1.00 equiv), K CO3 (432 mg,
2
BTazDMA (173 mg, 41%) was obtained as a yellow solid after
3.13 mmol, 2.50 equiv, 2m aqueous solution), and [Pd(PPh ) ]
3
4
column chromatography (petroleum ether (PE)/DCM, 1%). M.p.
(36 mg, 31 mmol, 2.5 mol%), DMABB (293 mg, 86%) was obtained
1
1
75.0–176.68C; H NMR (400 MHz, CD Cl ): d=8.11 (s, 1H), 7.81–
as a yellow solid after column chromatography (PE/DCM, 40%).
2
2
1
7
.74 (m, 4H), 7.56 (dd, J=8.6 Hz, 7.4 Hz, 2H), 7.46 (t, J=7.4 Hz,
M.p. 239.8–241.78C; H NMR (400 MHz, CD Cl ): d=7.67–7.65 (m,
2
2
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6
H), 7.56 (d, J=9.0 Hz, 2H), 7.46 (dd, J=8.1 Hz, 7.3 Hz, 2H), 7.35 (t,
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330; b) M. Pawlicki, H. A. Collins, R. G. Denning, H. L. Anderson, Angew.
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(
100 MHz, CD Cl ): d=151.8, 141.4, 140.6, 139.1, 129.3, 128.6, 127.9,
2 2
3
1
27.8, 127.7, 127.3, 126.9, 113.2, 40.9 ppm; HRMS (ESI): m/z calcd
+
+
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for C H N: 273.15120 [M] , 274.15903 [M+H] ; found: 273.15102
2
0
19
+
+
[M] , 274.15784 [M+H] .
DMABPyr: Starting from 2-bromopyridine (4d; 198 mg, 1.25 mmol,
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.00 equiv), 3 (404 mg, 1.25 mmol, 1.00 equiv), K CO3 (432 mg,
2
3
.13 mmol, 2.50 equiv, 2m aqueous solution), and [Pd(PPh ) ]
3
4
(
36 mg, 31 mmol, 2.5 mol%), DMABPyr (204 mg, 59%) was ob-
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9] a) Y. Zheng, A. S. Batsanov, V. Jankus, F. B. Dias, M. R. Bryce, A. P. Monk-
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1
6
5%). M.p. 210.3–212.68C; H NMR (400 MHz, CD Cl ): d=8.67 (d,
2 2
J=4.8 Hz, 1H), 8.06 (d, J=8.6 Hz, 2H), 7.81–7.74 (m, 2H), 7.68 (d,
J=8.6 Hz, 2H), 7.59 (d, J=9.0 Hz, 2H), 7.22 (dd, J=7.1, 4.8 Hz, 1H),
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13
6
.82 (d, J=9.0 Hz, 2H), 3.00 ppm (s, 6H); C NMR (100 MHz,
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2
2
1
27.6, 126.7, 122.4, 120.5, 113.2, 40.8 ppm; HRMS (ESI): m/z calcd
+
+
for C H N : 275.15428 [M+H] ; found: 275.15378 [M+H] .
1
9
18
2
2
014, 2, 2069–2081.
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2
[
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12] A. Qin, J. W. Y. Lam, B. Z. Tang, Chem. Soc. Rev. 2010, 39, 2522–2544.
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[
432 mg, 3.13 mmol, 2.50 equiv, 2m aqueous solution), and
Pd(PPh ) ] (36 mg, 31 mmol, 2.5 mol%), DMABPym (168 mg, 49%)
3
4
was obtained as a yellow solid after column chromatography
1
(
DCM/Et O, 1%). M.p. 198.8–201.18C; H NMR (400 MHz, CD Cl ):
2
2
2
d=8.79 (d, J=4.8 Hz, 2H), 8.47 (d, J=8.6 Hz, 2H), 7.70 (d, J=
.6 Hz, 2H), 7.61 (d, J=9.0 Hz, 2H), 7.18 (t, J=4.8 Hz, 1H), 6.82 (d,
8
13
J=9.0 Hz, 2H), 3.01 ppm (s, 6H); C NMR (100 MHz, CD Cl ): d=
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14] a) D. Lumpi, B. Stçger, C. Hametner, F. Kubel, G. Reider, H. Hagemann, A.
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1
65.0, 157.8, 151.0, 143.8, 135.8, 129.0, 128.3, 128.1, 126.4, 119.4,
1
13.1, 40.8 ppm; HRMS (ESI): m/z calcd for C H N : 275.14170
1
+
8
17
3
+
+
[M] , 276.14952 [M+H] ; found: 275.14163 [M] , 276.14840 [M+
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Keywords: charge transfer · chromophores · donor–acceptor
systems · nonlinear optics · triazoles
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[
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Received: July 25, 2016
2
Published online on && &&, 0000
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FULL PAPER
&
Charge Transfer
P. Kautny,* D. Bader, B. Stçger,
G. A. Reider, J. Frçhlich, D. Lumpi
&& – &&
Making connections: An in-depth anal-
ysis of the photophysical properties of
a large set of 1,2,3-triazole-linked
intriguing relationship between the tria-
zole substitution pattern and intramo-
lecular charge-transfer (ICT) phenomena
(see figure).
Structure–Property Relationships in
Click-Derived Donor–Triazole–
Acceptor Materials
donor–acceptor materials unveiled an
Chem. Eur. J. 2016, 22, 1 – 13
www.chemeurj.org
13
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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&
These are not the final page numbers! ÞÞ