T-Shaped (Donor-π-)2Acceptor-π-Donor Push-Pull Systems Based on Indan-1,3-dione

Article abstract of DOI:10.1002/ejoc.201500525

Sixteen model (donor-π-)₂acceptor-π-donor [(D-π-)₂A-π-D] molecules with an extraordinary T-shaped arrangement were designed and synthesized. Indan-1,3-dione was employed as a central acceptor with electron donors linked at the C-2, C-4, and C-7 positions. These push-pull molecules represent a first systematic modification of an indan-1,3-dione-fused benzene ring. The structures and properties of all target molecules were investigated by X-ray analysis, electrochemistry, UV/Vis absorption spectroscopy, differential scanning calorimetry, electric-field-induced second-harmonic generation (EFISHG) studies, and DFT calculations. A thorough evaluation of all of the gathered data has been performed, and structure-property relationships were evaluated. Electron donors attached at the C-2 position through π systems of various lengths affect the studied properties most significantly. The side donors at C-4 and C-7 can be described as auxiliary and do not dominate the observed properties. However, thiophene is a more efficient donor than N,N-dimethylaniline in this respect. Hence, indan-1,3-dione bearing a piperidylthiophene donor connected through a propenylidene spacer at C-2 completed with two side thiophen-2-ylethynyl branches at C-4 and C-7 showed the highest figure of merit among the studied properties. T-shaped chromophores based on an indan-1,3-dione central acceptor with systematically varied peripheral donors are investigated by X-ray analysis, electrochemistry, UV/Vis absorption spectroscopy, differential scanning calorimetry (DSC), electric-field-induced second-harmonic generation (EFISHG) studies, and DFT calculations. Structure-property relationships are subsequently elucidated.

Full text of DOI:10.1002/ejoc.201500525

FULL PAPER
DOI: 10.1002/ejoc.201500525
T-Shaped (Donor–π–)2Acceptor–π–Donor Push–Pull Systems Based on
Indan-1,3-dione
[a]
[a]
[a]
[a]
[b]
ˇ
ˇ
ˇ
Parmeshwar Solanke, Filip Bures,* Oldrich Pytela, Milan Klikar, Tomás Mikysek,
[c]
[c]
[d]
ˇ
ˇ
˚ˇ
Loic Mager, Alberto Barsella, and Zdenka Ruzicková
Keywords: Donor–acceptor systems / Chromophores / Electrochemistry / Nonlinear optics / Density functional calculations
Sixteen model (donor–π–)2acceptor–π–donor [(D–π–)2A–π–D]
molecules with an extraordinary T-shaped arrangement were
designed and synthesized. Indan-1,3-dione was employed as
a central acceptor with electron donors linked at the C-2, C-
4, and C-7 positions. These push–pull molecules represent a
first systematic modification of an indan-1,3-dione-fused
benzene ring. The structures and properties of all target mo-
and structure–property relationships were evaluated. Elec-
tron donors attached at the C-2 position through π systems
of various lengths affect the studied properties most signifi-
cantly. The side donors at C-4 and C-7 can be described as
auxiliary and do not dominate the observed properties. How-
ever, thiophene is a more efficient donor than N,N-dimeth-
ylaniline in this respect. Hence, indan-1,3-dione bearing a
lecules were investigated by X-ray analysis, electrochemis- piperidylthiophene donor connected through a propenylid-
try, UV/Vis absorption spectroscopy, differential scanning ene spacer at C-2 completed with two side thiophen-2-yl-
calorimetry, electric-field-induced second-harmonic genera- ethynyl branches at C-4 and C-7 showed the highest figure
tion (EFISHG) studies, and DFT calculations. A thorough
evaluation of all of the gathered data has been performed,
of merit among the studied properties.
Introduction
gated molecule with additional properties such as dipolar
character, intensive color, crystallinity, intermolecular inter-
actions, and chemical and thermal robustness.[8a] The most
common spatial arrangements of push–pull molecules in-
volve linear (D–π–A), quadrupolar (D–π–A–π–D or A–π–
D–π–A), and octupolar/tripodal [(D–π)3–A or (A–π)3–D].[8]
However, push–pull molecules with extraordinary arrange-
ments such as V, Y, H, and X shapes have also been re-
ported recently.[9–12] Since their first syntheses in 1888–
89,[13] indan-1,3-dione and its derivatives have been used as
dyestuffs (indenigo)[14] and as reagents for fingerprint devel-
opment in forensic science (ninhydrin).[15] Later, indan-1,3-
dione evolved into a powerful and readily accessible elec-
tron acceptor. In push–pull molecules, this moiety has been
widely used as a terminal acceptor group and can be intro-
duced by a standard Knoevenagel condensation.[16] The
withdrawing ability of indan-1,3-dione can be further en-
hanced by replacing one or both carbonyl groups by dicya-
novinyl or sulfoxide moieties to afford 3-(dicyanomethyl-
ene)indan-1-one, 1,3-bis(dicyanomethylene)indan, and 3-di-
Push–pull systems comprising an electron donor (D) and
acceptor (A) attached to a π-conjugated backbone un-
doubtedly represent an important class of organic sub-
stances for modern applications, especially in materials
chemistry. These molecules and dyes have found particular
use in organic (opto)electronics and photonics.[1,2] Nowa-
days, D–π–A chromophores are commonly studied as non-
linearly optically active substances (NLOphores)[3–5] as well
as in dye-sensitized solar cells (DSSCs).[6] Beside these two
most widely explored applications, push–pull molecules are
also used in organic field-effect transistors (OFET), organic
light-emitting diodes (OLEDs), and optical memory.[7] Di-
rect D–A interactions in push–pull molecules or so-called
intramolecular charge transfer (ICT) provides the π-conju-
[a] Institute of Organic Chemistry and Technology, Faculty of
Chemical Technology, University of Pardubice,
Studentská 573, 53210 Pardubice, Czech Republic
E-mail: filip.bures@upce.cz
http://bures.upce.cz
[b] Department of Analytical Chemistry, Faculty of Chemical
Technology, University of Pardubice,
Studentská 573, 53210 Pardubice, Czech Republic
[c] Département d’Optique ultrarapide et de Nanophotonique,
IPCMS-CNRS,
23 Rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France
[d] Department of General and Inorganic Chemistry, Faculty of
Chemical Technology, University of Pardubice,
Studentská 573, 53210 Pardubice, Czech Republic
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500525.
cyanomethylene-2,3-dihydrobenzo[b]thiophene
1,1-diox-
ide.[17] In addition to significant NLO activity,[18] push–pull
molecules bearing these acceptor moieties have also found
numerous applications in DSSCs,[19] bulk heterojunction
solar cells (BHJSCs),[20] organic photovoltaic cells
(OPVCs),[21] OLEDs,[22] as vesicle-, gel-, and glass-forming
molecules,[23] or chromoionophores for anion sensing and
recognition.[24]
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F. Buresˇ et al.
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A joint feature of all of the aforementioned, mostly linear acceptor moiety with three donor-substituted branches ap-
D–π–A systems is their terminal indan-1,3-dione acceptor. pended at C-2, C-4, and C-7. Fine property tuning has been
To the best of our knowledge, indan-1,3-dione has not been achieved by variation of the peripheral electron donors
used as a central acceptor moiety to date. Hence, further [N,N-dimethylanilino (DMA), thiophenyl, and 5-(piperidin-
to our preliminary synthetic communication,[25] we report 1-yl)thiophene-2-yl (PIT)] as well as by extension and plan-
herein the design, synthesis, and further studies on T- arization of the whole π-conjugated system through ad-
shaped push–pull molecules 1–16 (Figure 1). These ditional π linkers (acetylenic units). Organic push–pull mo-
(D–π–)2A–π–D molecules possess a central indan-1,3-dione lecules with T-shaped arrangements are a less investigated
class of D–π–A systems. Representative T-shaped molecules
have mostly been built from heterocyclic T-junctions such
as pyrene-spiropyran,[26] benzo[d]imidazole,[27] quinoxal-
ine,[28] phenazine,[29] or carbazole.[30] Despite the immense
and unfading interest in indan-1,3-dione-derived push–pull
molecules,[16–24,31] no attempts have been directed towards
the modification of indan-1,3-dione fused to a benzene ring
to gain access to T-shaped molecules.
Results and Discussion
Synthesis
The synthetic strategy leading to the target T-shaped
chromophores 1–16 is outlined in Scheme 1. The reaction
sequence starts from commercially available and inexpen-
Figure 1. T-shaped push–pull molecules 1–16 based on indan-1,3-
dione.
Scheme 1. Synthetic pathway to T-shaped chromophores 1–16. (a) I2, oleum (25%), 70 °C, 46%; (b) CH3COCH2COOEt, Et3N, Ac2O,
25 °C, then HCl, H2O, 80 °C, 50%; (c) for 23 and 24: 19 or 20, Al2O3, CH2Cl2, 25 °C, 80% (23), 77% (24); for 25 and 26: 21 or
22, piperidine, EtOH, Δ, 72% (25), 83% (26); (d) [4-(dimethylamino)phenyl]boronic acid pinacol ester or (thiophene-2-yl)boronic acid,
[PdCl2(PPh3)2], Na2CO3, tetrahydrofuran (THF), H2O, 60 °C; (e) 4-ethynyl-N,N-dimethylaniline or 2-ethynylthiophene, [PdCl2(PPh3)2],
CuI, Et3N, THF, 60 °C.
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T-Shaped Push–Pull Systems Based on Indan-1,3-dione
sive phthalic anhydride and its iodination with I2 and
oleum. In contrast to the 4,5-regioselectivity with phthal-
imide,[32] the iodination of phthalic anhydride afforded 3,6-
diiodophthalanhydride (17). The observed regioselectivity is
in accordance with the recently reported phthalic anhydride
bromination;[33] however, it should be noted that the reac-
tion outcome and regioselectivity strongly depends on the
concentration of the oleum used. The molecular structure
of 17 has also been confirmed by X-ray analysis (see Sup-
porting Information). Compound 17 was further treated
with ethyl acetoacetate in a Claisen condensation, and sub-
sequent acid-catalyzed decarboxylation[34] afforded 4,7-di-
iodoindan-1,3-dione (18) in 50% yield. The molecular
structure of 18 was confirmed by X-ray analysis (see Sup-
porting Information). Subsequent Al2O3- or piperidine-cat-
alyzed Knoevenagel condensations of 18 with 4-(N,N-di-
methylamino)benzaldehyde (19), 4-(N,N-dimethylamino)-
cinnamaldehyde (20), and the PIT-derived aldehydes 21 and
22 afforded molecules 23–26 with good yields ranging from
72 to 83%. PIT aldehyde 21 and its extended analogue 22
were synthesized by the method reported by Blanchard–
Desce.[35] The peripheral donors were introduced through
twofold Suzuki–Miyaura or Sonogashira cross-coupling re-
actions of 23–26 with boronic acid (pinacol ester) and eth-
ynyl-substituted DMA and thiophene. The starting boronic
acid (pinacol esters) and terminal acetylenes were either
commercially available or can be synthesized according to
our earlier procedures.[36] The target T-shaped molecules 1–
16 were obtained in reasonably good yields of 30–88%
upon purification by column chromatography.
Figure 2. Front and side views of T-shaped chromophores 1 (a) and
3 (b) measured at 150 K with R = 0.08 (1) and 0.07 (3). CCDC-
943001 (for 1) and -1031512 (for 3) contain the supplementary crys-
tallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
can also be assessed by the Bird index I6, which was calcu-
lated to be 81 and 88 for the lower and peripheral rings in
1. The peripheral DMA rings in 3 possess I6 values of 91,
which reflects their higher twist (unsubstituted benzene pos-
sesses I6 = 100). The Bird index of the lower thiophene ring
in 3 was calculated to be 58 (unsubstituted thiophene pos-
sesses I6 = 66). Both indicators imply higher quinoid char-
acter (less aromaticity) of the lower DMA and thiophene
rings than for the peripheral DMA rings. Thus, the lower
rings are involved in more ICT than the peripheral ones.
X-ray Analysis
Crystals of 1 and 3 suitable for X-ray analysis were ob-
tained by the slow diffusion of hexane into dichlorometh-
ane solutions. The ORTEP plots shown in Figure 2 confirm
the proposed molecular structures of 1 and 3 and can also
be used to determine the extent of the ICT. In this respect,
the involvement of the particular DMA rings in the ICT
can be assessed by their spatial arrangement and bond
length alternation (quinoid character δr and Bird index
I6).[37,38]
Although the lower DMA ring in 1 separated by an ad-
ditional olefinic unit is almost coplanar to the indan-1,3-
dione core (torsion angle φ1 = 1°), both side DMA rings
Electrochemistry
Electrochemical measurements of chromophores 1–16
are forced out of the indan-1,3-dione plane with torsion were performed in N,N-dimethylformamide containing
angles φ2 and φ3 of 45 and 46°, respectively. The corre- 0.1 m Bu4NPF6 in a three-electrode cell by cyclic voltamme-
sponding torsion angles φ1, φ2, and φ3 in PIT-substituted try (CV) and rotating disk voltammetry (RDV). The work-
chromophore 3 are 0.2, 44, and 61°. The large torsion ing electrode was a platinum disk (2 mm diameter) for the
angles φ2 and φ3 in 1 and 3 would present a barrier to the CV and RDV experiments. A saturated calomel electrode
efficient conjugation of both peripheral DMA rings with (SCE) separated by a bridge filled with supporting electro-
the central indan-1,3-dione acceptor. The calculated quin- lyte and a Pt wire were used as the reference and auxiliary
oid characters of the lower and peripheral DMA rings in 1 electrodes, respectively. The acquired data are summarized
are 0.025 and 0.016 Å, whereas the peripheral DMA rings in Table 1, and representative CV plots of 4–8 and 16 are
in 3 possess δr values of 0.01/0.011 Å. In benzene, δr is shown in the Supporting Information.
equal to 0, whereas δr in a fully quinoid ring would be
For compounds bearing a DMA donor at the lower
0.1 Å. The aromaticity of the DMA and thiophene rings branch, one overall oxidation process was observed by CV.
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Table 1. Electrochemical and optical data for chromophores 1–16.
E1/2(ox1) [V][a] E1/2(red1) [V][a]
ΔE [V][b]
EHOMO [eV][c] ELUMO [eV][c]
λmax [nm (eV)][d] ε [103 mol–1 dm3 cm–1]
1
0.81
0.76
0.77
0.55
1.00
0.80
0.77
0.57
0.85
0.82
0.73
0.56
1.07
0.82
0.78
0.57
–1.25
–1.06
–1.28
–1.02
–1.13
–0.92
–1.20
–0.91
–1.12
–0.94
–1.17
–0.94
–1.05
–0.89
–1.12
–0.86
2.06
1.82
2.05
1.57
2.13
1.72
1.97
1.48
1.97
1.76
1.90
1.50
2.12
1.71
1.90
1.43
–5.16
–5.11
–5.12
–4.90
–5.35
–5.15
–5.12
–4.92
–5.20
–5.17
–5.08
–4.91
–5.42
–5.17
–5.13
–4.92
–3.10
–3.29
–3.07
–3.33
–3.22
–3.43
–3.15
–3.44
–3.23
–3.41
–3.18
–3.41
–3.30
–3.46
–3.23
–3.49
486 (2.55)
530 (2.34)
524 (2.37)
609 (2.04)
495 (2.51)
554 (2.23)
531 (2.34)
625 (1.98)
503 (2.46)
546 (2.27)
543 (2.28)
631 (1.97)
510 (2.43)
570 (2.18)
548 (2.27)
641 (1.93)
53.6
50.1
84.0
40.0
70.5
43.1
95.0
73.0
87.9
31.9
87.4
76.4
55.4
41.7
59.5
78.3
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
[a] E1/2(ox1) [E1/2(red1)] are half-wave potentials of the first oxidation (reduction) measured by RDV. [b] ΔE = E1/2(ox1) – E1/2(red1), electro-
chemical gap. [c] –EHOMO/LUMO = E1/2 (ox1/red1) + 4.35.[39] [d] Measured in CH2Cl2 (10–5 m), optical band gap calculated as 1240/λmax
.
This process most likely comprises several one-electron sub- the side DMA donors by thiophenes (e.g., 1–4/5–8 and 9–
processes merged into one wave, as indicated by the RDV 12/13–16) has a significant impact on the first reduction
results. More oxidation processes were observed for the re- potentials; however, the effect slightly diminishes as the π-
maining PIT-substituted chromophores, and the first re- conjugated system of the chromophore increases.
duction seems to be a one-electron process. Except for that
The electrochemical gaps ΔE (Table 1), calculated as the
of 1, all oxidations were irreversible. The first oxidation po- difference between the first oxidation and reduction poten-
tentials are listed in Table 1 and range from 1.07 to 0.55 V. tials, significantly change with extension of the lower
Considering the N,N-dimethylamino, thiophene, or PIT branch (n = 0 or 1; compare, e.g., 5/6, 9/10, or 15/16). This
moieties as the main oxidation centers, the observed simple structural change reduces the gap by 0.21–0.49 V.
changes reflect (1) the variation of the peripheral donor The replacement of the lower donor (DMAǞPIT) reduces
groups, (2) the extension of the lower branch by an ad- the electrochemical gap by an additional 0.01–0.28 V, espe-
ditional olefinic unit (n = 0 or 1), and (3) the presence of cially for extended molecules with n = 1 (compare, e.g., 9/
additional acetylenic units separating the side donors. For 11 and 10/12). The replacement of the side donors
instance, the influence of the first structural changes can be (DMAǞthienyl) has a very similar effect. Except for those
demonstrated on pairs of chromophores 2/4 [E(ox1) = 0.76/ of 1/5 and 9/13 (ΔE = +0.07 and +0.15 V), the electrochem-
0.55 V] and 2/6 [E(ox1) = 0.76/0.80 V]. Thus, the replacement ical gaps ΔE for pairs of chromophores 2/6, 3/7, 4/8, 10/14,
of the lower DMA donor by a PIT group (2Ǟ4) resulted 11/15, and 12/16 slightly decreased within the range 0–0.09
in a decrease of the first oxidation potential by 0.21 V, V. Hence, the side electron donors have a very small influ-
whereas the replacement of the peripheral DMA donors by ence on the electrochemical gaps of T-shaped molecules 1–
thiophene donors (2Ǟ6) has only a diminished effect. The 16. The extension and planarization of the π-conjugated
extension of the lower branch especially affects the first system by two additional acetylenic units as in 9–16 (vs. 1–
oxidation potential of the PIT-substituted chromophores 8) have a similar effect. This structural change reduced the
[ΔE(ox1) ≈ 0.2 V, compare, e.g., 3/4, 7/8, 11/12, or 15/16, electrochemical gaps by 0–0.15 V; however, the effect dimin-
Table 1]. The further extension and planarization of the side ishes as the size of the molecule increases. The lowest elec-
branches with triple bond spacers affected the first oxid- trochemical gap of 1.43 V was measured for 16 with a PIT
ation potentials only negligibly (compare, e.g., 1–4/9–12 or lower donor, thiophene side rings, and the most extended π
5–8/13–16, Table 1).
system.
The observed first reductions seem to be one-electron
and mostly reversible processes at the central indan-1,3-di-
one acceptor. The first reduction potentials range from
–1.28 to –0.86 V and are clearly a function of the peripheral
UV/Vis Spectroscopy
All target compounds are highly colored compounds,
substituents appended to the indan-1,3-dione core and their colors range from yellow, orange, and red to blue
(Table 1). The most significant effect can be seen for the (see Supporting Information). The optical properties of 1–
extension of the lower branch [ΔE(red1) ≈ 0.2–0.3 V; com- 16 were investigated by electronic absorption spectroscopy;
pare, e.g., 1/2, 3/4, 5/6, etc.] and the side branches by two the measured longest-wavelength absorption maxima λmax
acetylenic units [ΔE(red1) ≈ 0.1 V; compare, e.g., 1–4/9–12, and molar absorption coefficients ε are summarized in
5–8/13–16, Table 1]. In contrast to its effect on the first Table 1. Representative spectra of chromophores 4–8 and
oxidation, the replacement of the lower donor has only a 16 are shown in Figure 3, and the remaining spectra are
diminished effect on the first reduction. The replacement of provided in the Supporting information.
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T-Shaped Push–Pull Systems Based on Indan-1,3-dione
306 °C, and the decomposition temperatures were estimated
to be in the range 237–312 °C. The measured Td values can
be considered to be high compared with those of other
push–pull chromophores. The thermal stabilities of 1–8
generally decrease as the length of the spacer (n) increases
and, more clearly, as the side DMA moieties are replaced
by thiophene rings (compare, e.g., 1/2 vs. 5/6). Compounds
4 and 7 showed (slow) monotropic solid–solid transitions.
Compound 6 contained a eutectic impurity. The decompo-
sition temperatures of 9–16 range from 180 to 263 °C.
Within this series, the replacement of the side donors affec-
ted the thermal properties most significantly. From the
DSC measurements, we can conclude that chromophores
1–16 resist thermal decomposition up to 180–312 °C; the
lowest and highest Td values were measured for 14 and 4,
respectively, which reflects their different chemical struc-
tures.
Figure 3. Representative UV/Vis absorption spectra of chromo-
phores 4–8 and 16 measured in CH2Cl2 (10–5 m).
All of the absorption spectra are dominated by intense
charge-transfer (CT) bands; the longest-wavelength maxima
at λ = 486–641 nm (2.55–1.93 eV) are clearly dependent on
the structure of the given chromophore. Target chromo-
phores 1–16 showed no emission properties. Considering
the representative subseries of chromophores 4–8 and 16
shown in Figure 3, we can deduce the following relation-
ships: (1) the extension of the lower π system (5Ǟ6 and
7Ǟ8) resulted in bathochromic shifts of 59 and 94 nm (0.28
and 0.36 eV), respectively, (2) the replacement of the lower
donor (5Ǟ7 and 6Ǟ8) redshifted the λmax by 36 and 71 nm
(0.17 and 0.25 eV), (3) the replacement of the peripheral
DMA donors by thienyl groups (4Ǟ8) affected the position
of the λmax moderately (16 nm/0.06 eV redshift), and (4) the
extension and planarization of the peripheral thienyl groups
as in 16 versus 8 shifted the CT band bathochromically by
an additional 16 nm. These effects are in accordance with
the observations made by electrochemistry. Thus, the most
Figure 4. Representative DSC curves of 5 and 16 determined with
a scanning rate of 7 °C/min under N2.
Table 2. Thermal properties of chromophores 1–16.[a]
Tm [°C]
Td [°C]
1
297
266
290
306
247
227
228
201
–
–
–
–
–
308
290
302
312
288
267
267
237
252
261
240
229
190
180
230
263
2
3
4
bathochromically shifted CT band [λmax
= 641 nm
5
(1.93 eV)] has been observed for chromophore 16 bearing a
PIT lower donor connected through a butadiene spacer and
two peripheral thienyl groups linked through acetylenic
units.
6
7
8
9
10
11
12
13
14
15
16
Thermal Properties
–
–
–
The thermal behavior of chromophores 1–16 was studied
by differential scanning calorimetry (DSC). The thermo-
grams of selected chromophores 5 and 16 are shown in Fig-
ure 4, and all measured melting temperatures (Tm) and ther-
[a] Tm = melting point (the point of intersection of a baseline before
the thermal effect with a tangent); Td = thermal decomposition
mal decomposition temperatures (Td) are listed in Table 2. (pyrolysis in N2 atmosphere).
For the DSC curves of 1–16, see the Supporting Infor-
mation. As a general trend, 1–8 showed both melting points
and decomposition temperatures, whereas 9–16 with an ad-
ditional acetylenic spacer decomposed directly. For 1–8, de-
EFISHG Experiment
composition occurred almost immediately upon melting of
The NLO activity of the chromophores was measured
the sample. The melting points of 1–8 range from 201 to by the conventional electric-field-induced second-harmonic
Eur. J. Org. Chem. 2015, 5339–5349
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F. Buresˇ et al.
FULL PAPER
generation (EFISHG) technique, which provides access to cers; e.g., 1/2, 3/4, 5/6, 7/8, etc.). These structural modifica-
the μβ product (μ is the dipole moment, and β is the vector tions resulted in changes in μβ within the range 160–1580
part of the hyperpolarizability). The compounds were dis- esu. The replacements of the lower donor (DMAǞPIT;
solved in dichloromethane at concentrations of ca. 10–3
m
e.g., 1/3, 2/4, 5/7, 6/8, etc.) and the side donors (DMAǞthi-
and illuminated with a laser beam emitted by a pulsed enyl; e.g., 1/5, 2/6, 3/7, 4/8, etc.) have smaller effects on the
Nd:YAG laser, Raman-shifted to λ = 1907 nm through a measured NLO activity (Δμβ of 50–940 and 0–900 esu,
high-pressure hydrogen cell so that the second harmonic at respectively). The extension and planarization of the π sys-
λ = 953 nm stays well clear of the absorption bands of tem with additional acetylenic subunits appended at C-4
the chromophores. A high-voltage signal was applied to the and C-7 (e.g., 1/9, 2/10, 3/11, 4/12, etc.) showed a dimin-
solution, synchronous with the laser pulses, to orient the ished effect with Δμβ = 20–420 esu. The most pronounced
chromophores and break the initial centrosymmetry. The NLO activity with Δμβ = 2100 esu was measured for chro-
intensity of the generated second harmonic was measured mophore 16, which also showed the lowest electrochemical
as a function of the length of the optical path, and the re- and optical gaps.
sulting curves (Maker fringes) were then analyzed and com-
pared with a reference (quartz crystal) to determine the μβ
value for the chromophore. The absolute values were de-
fined against a quartz wedge reference by taking its qua-
DFT Calculations and Further Considerations
dratic susceptibility to be d11 = 1.2ϫ10–9 esu at 1.064 μm
and by extrapolating it to 1.1ϫ10–9 esu at 1.907 μm. The
measurements were repeated at various chromophore con-
centrations to detect any aggregation problems (which can
be recognized by an abnormal drop in the SHG amplitude).
The measured μβ products for all target T-shaped chro-
mophores 1–16 are listed in Table 3. Very similar relation-
ships to those deduced from the electrochemical data and
linear optical properties can also be deduced from the NLO
data. In general, the NLO responses can be tuned by struc-
tural changes in 1–16 within the range 230 to 2100 esu. The
observed NLO activity is most significantly affected by the
extension of the lower π system (ethene vs. butadiene spa-
The spatial and electronic properties of chromophores 1–
16 were also investigated by DFT calculations by using the
B3LYP/6-31G(d) and B3LYP/6-311++G(2d,p)//B3LYP/6-
31G(d) methods (see the Supporting Information for more
details). For 5–8 and 13–16, two stable conformers are an-
ticipated with the thiophene sulfur atoms oriented in and
out of the molecule (further referred to as 5–8in, 13–16in,
5–8out, 13–16out; Figure S33). Therefore, DFT calcula-
tions were performed for both conformers. The total ener-
gies (Etotal), energies of the highest occupied molecular or-
bital (HOMO) and lowest unoccupied molecular orbital
(LUMO; EHOMO and ELUMO) and their differences (ΔE),
ground-state dipole moments (μ), and first hyperpolariz-
abilities [β(–2ω,ω,ω) at 1907 nm] were calculated and are
presented in Tables 3 and S2.
Table 3. Calculated and experimental data for chromophores 1–16.
The calculated total energies (Table S2) and other elec-
tronic properties (Table 2), except for the dipole moments,
of both in and out conformers are close, which implies that
none of them are theoretically preferred, and nonbonding
interactions between the branches and the indan-1,3-dione
central moiety are less important. The energy of the elec-
tron transition calculated from the position of the longest-
wavelength absorption maxima (1240/λmax) correlates very
tightly with the electrochemical gap ΔE according to Equa-
tion (1) and Figure S58.
[a]
EHOMO ELUMO ΔEDFT
μ
βDFT
μβ (2ω)[b]
[eV][a]
[eV][a]
[V][a] [D][a] (–2ω,ω,ω) [10–48 esu]
[10–30 esu]
1
–4.95
–4.93
–4.89
–4.91
–5.69
–5.72
–5.52
–5.54
–5.53
–5.51
–5.37
–5.39
–4.87
–4.85
–4.84
–4.82
–5.56
–5.57
–5.49
–5.52
–5.50
–5.51
–5.35
–5.38
–2.25
–2.46
–2.25
–2.48
–2.58
–2.60
–2.76
–2.77
–2.55
–2.52
–2.73
–2.74
–2.36
–2.53
–2.31
–2.53
–2.70
–2.72
–2.81
–2.83
–2.66
–2.68
–2.78
–2.81
2.70
2.47
2.64
2.43
3.12
3.12
2.77
2.77
2.98
2.99
2.64
2.64
2.51
2.32
2.53
2.29
2.86
2.85
2.68
2.69
2.84
2.83
2.57
2.58
4.45 12.6
6.05 84.1
5.01 5.4
330
960
230
1220
430
2
3
4
5in
5out
6in
6out
7in
7out
8in
6.76 50.7
5.44 69.8
6.42 66.7
7.27 180.3
8.25 176.0
6.97 53.1
7.66 38.6
8.40 122.2
9.28 117.7
5.07 37.7
6.59 41.8
5.90 84.9
7.44 61.1
5.05 63.4
6.44 62.3
6.89 180.7
8.23 179.6
6.54 52.3
8.04 51.2
8.09 141.5
9.30 139.9
1040
480
1240/λmax = (0.84Ϯ0.08) + (0.78Ϯ0.05)ΔE; n = 16, s = 5.15 10–2,
1750
r = 0.965
(1)
8out
9
750
910
520
1200
600
On the contrary, the correlations of the calculated
HOMO and LUMO energies are more complicated. The
correlation of the electrochemically measured and calcu-
lated energies of the HOMO (EHOMO vs. EHOMO,DFT, Fig-
ure S59) clearly splits into two groups. For the first group,
involving chromophores 5–8 and 13–16 with thiophene side
donors, slightly lower calculated HOMO energies were ob-
tained (ΔEHOMO ≈ 0.6 eV). However, these values showed a
statistically significant correlation with the electrochemical
EHOMO values according to Equation (2).
10
11
12
13in
13out
14in
14out
15in
15out
16in
16out
1160
520
2100
[a] All data were calculated by DFT calculations [B3LYP/6-
311++G(2d,p)//B3LYP/6-31G(d)]. [b] Measured at λ = 1907 nm in
CH2Cl2 (EFISHG).
EHOMO = (2.86Ϯ1.18) + (1.45Ϯ0.21)EHOMO,DFT; n = 16, s = 8.56
10–2, r = 0.876
(2)
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 5339–5349

T-Shaped Push–Pull Systems Based on Indan-1,3-dione
The DFT-derived energies of the HOMOs of chromo- LUMO energies and the corresponding electrochemical
phores 1–4 and 9–12 with DMA peripheral donors showed gaps are affected by the variation of the peripheral donor
no significant correlation with the electrochemical EHOMO
.
groups (mainly by the DMAǞPIT replacement), the exten-
According to the calculated HOMO/LUMO localizations sion of the lower π system, and the presence of additional
given in the Supporting Information, this group of mo- acetylenic units separating the side donors. The UV/Vis ab-
lecules possess the HOMO localized mainly on the periph- sorption spectra of chromophores 1–16 are dominated by
eral DMA rings. This is in contrast to the thiophene-substi- intense CT bands, and the position of the longest-wave-
tuted chromophores 5–8 and 13–16, in which the HOMO length absorption maximum is affected similarly to the elec-
is predominantly localized on the lower C-2 donor.
trochemically measured properties. The electrochemical and
A similar observation can be made for the energies of the optical gaps correlate very closely. From the DSC measure-
LUMO. Again, the dependence (Figure S60) splits into two ments, we can conclude that 1–16 resist thermal decomposi-
groups involving the same chromophores, but both corre- tion up to 180–312 °C. Although 1–8 showed melting points
lations (line 1 and line 2) are statistically significant and and subsequent decomposition temperature, compounds 9–
tight as shown in Equations (3) and (4).
16 with the peripheral donors separated by an additional
acetylenic spacer decomposed directly. The second-order
nonlinearities of NLOphores 1–16 as measured by EF-
ISHG experiments were affected very significantly by the
Line 1: ELUMO = –(0.04Ϯ0.33) + (1.22Ϯ0.01)ELUMO,DFT; n = 16,
s = 4.54 10–2, r = 0.937
(3)
Line 2: ELUMO = –(0.63Ϯ0.18) + (1.10Ϯ0.01)ELUMO,DFT; n = 8, aforementioned structural changes, and the μβ values were
s = 2.34 10–2, r = 0.986
(4)
within the range 230 to 2100 esu. The DFT calculations
revealed significant differences between the T-shaped mo-
lecules bearing thiophene side donors (5–8 and 13–16) and
their DMA-substituted analogues (1–4 and 9–12). Both
types of chromophore showed distinctly different HOMO
and LUMO localizations. Hence, chromophore 16 bearing
a PIT lower donor connected through a propenylidene
spacer and completed with two side thiophen-2-ylethynyl
branches showed the lowest HOMO–LUMO gap (1.43 eV),
the most bathochromically shifted CT band by 641 nm
(1.93 eV), and the highest optical nonlinearity with a μβ
value of 2100 esu.
Although line 1 statistically passes zero, line 2 is shifted
to lower values by ca. 0.6 eV. This is most likely because
of a different localization of the LUMO in both types of
chromophores. Although the LUMOs in 5–8 and 13–16 are
spread over the lower C-2 π system and the peripheral thio-
phene branches, the DMA branches in 1–4 and 9–12 are
solely occupied by the HOMO. The LUMOs in 1–4 and 9–
12 are spread over the lower C-2 π system (see Supporting
Information). As thiophene is more polarizable than benz-
ene, a LUMO spread over a thiophene ring generally has
lower energy.[8b,40]
The calculated hyperpolarizabilities βDFT are summa-
rized in Table 3. These data generally follow the trends seen
by the μβ values measured by the EFISH experiments; how-
ever, the correlation is not very tight. The extension of the
π system and the replacement of the particular donors had
a similar impact on the calculated and experimental nonlin-
earities. The highest βDFT coefficients were calculated for
NLOphores 6, 14, and 16 with the most extended π systems
and peripheral thiophene donors.
Experimental Section
Materials and General Methods: Reagent-grade reagents and sol-
vents were purchased from Penta, Aldrich, and Across and used as
received. The synthetic details and full spectral characterization of
1, 2, 5, 6, 9, 10, 13, 14, 17, 18, 23, and 24[25] as well as the synthesis
of PIT aldehydes 21 and 22[35] have been reported previously. Col-
umn chromatography was performed with silica gel 60 (particle size
0.040–0.063 nm, 230–400 mesh) and commercially available sol-
vents. TLC was conducted with aluminum sheets coated with silica
gel 60 F254 (Merck) with visualization by a UV lamp (254 and
1
360 nm). The H and 13C NMR spectra were recorded at 400/500
Conclusions
and 100/125 MHz with Bruker AVANCE 400 and AVANCE 500
instruments at 25 °C. The latter was equipped with a Prodigy Cryo-
Probe. The chemical shifts are reported in ppm relative to the signal
of Me4Si. The residual solvent signal in the 1H and 13C NMR spec-
tra was used as an internal standard (CDCl3: δ = 7.25 and
We have designed a new class of T-shaped molecules and
have demonstrated the first systematic modification of in-
dan-1,3-dione derivatives with a substituted fused benzene
ring. The central indan-1,3-dione acceptor has been suc-
cessfully equipped with electron donors at positions C-2, C- 77.23 ppm). The apparent resonance multiplicities are described as
s (singlet), br s (broad singlet), d (doublet), and m (multiplet). The
particular (hetero)aromatic protons of the PIT, DMA, thiophen-2-
yl, and piperidin-1-yl moieties are denoted as PIT, DMA, th and
pip, respectively. The IR spectra were recorded with a Perkin–El-
mer FTIR Spectrum BX spectrometer. High-resolution MALDI
MS spectra were recorded with an LTQ Orbitrap XL MALDI mass
spectrometer (Thermo Fisher Scientific) equipped with a nitrogen
UV laser (337 nm, 60 Hz). The LTQ Orbitrap instrument was oper-
ated in positive-ion mode over a normal mass range (m/z 50–1500)
with the following parameters: resolution 100000 at m/z = 400, la-
4, and C-7 to gain access to tripodal nonsymmetrical (D–
π)3–A molecules. The structures and properties of target
molecules 1–16 were studies by X-ray analysis, electrochem-
istry, UV/Vis absorption spectroscopy, DSC, and EFISHG
experiments. The experimental data were further completed
with DFT calculations. The single-crystal X-ray analysis of
two representative derivatives 1 and 3 showed that the lower
donor/π system is involved in more-efficient ICT than the
peripheral donors attached at C-4 and C-7. The electro-
chemical measurements have shown that the HOMO/ ser energy 17 mJ, five laser shots. The survey crystal positioning
Eur. J. Org. Chem. 2015, 5339–5349
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5345

F. Buresˇ et al.
FULL PAPER
system (survey CPS) was set for the random choice of shot position
by automatic crystal recognition. For collision-induced dissociation
(CID) experiments with the LTQ linear ion trap, an isolation width
Δm/z of 4, normalized collision energy of 25%, activation Q value
of 0.250, activation time of 30 ms were used with helium as the
collision gas. The matrix was 2,5-dihydroxybenzoic acid (DHB).
The mass spectra were averaged over the whole MS record (30 s)
for all measured samples. Elemental analyses were performed with
an EA 1108 Fisons instrument. The UV/Vis spectra were recorded
with a Hewlett–Packard 8453 spectrophotometer with samples in
CH2Cl2. The electrochemical measurements were performed in
N,N-dimethylformamide containing 0.1 m Bu4NPF6 in a three-elec-
trode cell by cyclic voltammetry (CV) and rotating disk voltamme-
try (RDV). The working electrode was a platinum disk (2 mm in
diameter) for the CV and RDV experiments. As the reference and
auxiliary electrodes, a saturated calomel electrode (SCE) separated
by a bridge filled with the supporting electrolyte and a Pt wire were
used, respectively. All potentials are given vs. SCE. Voltammetric
measurements were performed with a PGSTAT 128N potentiostat
(AUTOLAB, Metrohm Autolab B.V) operated with the NOVA
1.10 software. For details of the X-ray analysis, see the Supporting
Information. The thermal properties of the target molecules were
measured by DSC with a Mettler–Toledo STARe System DSC 2/
700 instrument equipped with an FRS 6 ceramic sensor and a HU-
BERT TC100-MT RC 23 cooling system.
601.9147. C21H17I2NO2S (601.2391): calcd. C 41.95, H 2.85, N
2.33, S 5.33; found C 41.95, H 2.90, N 2.30, S 5.21.
General Method for Suzuki–Miyaura Cross-Coupling. Synthesis of
Chromophores 3, 4, 7, and 8: Diiodo derivative 25 (287 mg,
0.5 mmol) or 26 (300 mg, 0.5 mmol) and [4-(dimethylamino)-
phenyl]boronic acid pinacol ester (272 mg, 1.1 mmol) or (thiophen-
2-yl)boronic acid (139 mg, 1.1 mmol) were dissolved in a THF/H2O
mixture (20 mL, 4:1). Argon was bubbled through the solution for
15 min, whereupon [PdCl2(PPh3)2] (18 mg, 0.025 mmol) and
Na2CO3 (159 mg, 1.5 mmol) were added, and the reaction mixture
was stirred at 60 °C for 3 h. The reaction mixture was diluted with
H2O (50 mL) and extracted with CH2Cl2 (2ϫ50 mL). The com-
bined organic extracts were dried (Na2SO4), the solvents were evap-
orated in vacuo, and the crude product was purified by column
chromatography (SiO2; indicated solvent system).
General Method for Sonogashira Cross-Coupling. Synthesis of Chro-
mophores 11, 12, 15, and 16: Diiodo derivative 25 (287 mg,
0.5 mmol) or 26 (300 mg, 0.5 mmol) and 4-ethynyl-N,N-dimeth-
ylaniline (159 mg, 1.1 mmol) or 2-ethynylthiophene (110 mg,
1.1 mmol) were dissolved in a mixture of THF/Et3N (20 mL, 4:1).
Argon was bubbled through the solution for 15 min, whereupon
[PdCl2(PPh3)2] (18 mg, 0.025 mmol) and CuI (10 mg, 0.05 mmol)
were added, and the reaction mixture was stirred at 60 °C for 3 h.
The reaction mixture was diluted with H2O (50 mL) and extracted
with CH2Cl2 (2 ϫ 50 mL). The combined organic extracts were
dried (Na2SO4), the solvents were evaporated in vacuo, and the
crude product was purified by column chromatography (SiO2; indi-
cated solvent system).
General Method for Knoevenagel Condensation. Synthesis of 25–26:
4,7-Diiodoindan-1,3-dione (18) (3.98 g, 10.0 mmol) and 5-(piperi-
din-1-yl)thiophene-2-carbaldehyde (21; 2.05 g, 10.5 mmol) or 3-[5-
(piperidin-1-yl)thiophen-2-yl]propenal (22; 2.32 g, 10.5 mmol) were
dissolved in absolute ethanol (40.0 mL), and a catalytic amount of
piperidine was added. The mixture was heated at reflux for 3 h and
then cooled to room temperature. The solvent was evaporated in
vacuo, and the crude product was purified by column chromatog-
raphy (SiO2; CH2Cl2/hexane 2:1).
2-[5-(Piperidin-1-yl)thiophen-2-ylmethylidene]-4,7-bis[4-(dimethyl-
amino)phenyl]indan-1,3-dione (3): The title compound was prepared
from 25 and [4-(dimethylamino)phenyl]boronic acid pinacol ester
by following the general procedure for Suzuki–Miyaura cross-cou-
pling. The product was obtained as an orange solid (168 mg, 60%);
Rf = 0.2 (CH2Cl2). 1H NMR (400 MHz, CDCl3): δ = 1.61–1.67 (m,
6 H, pip), 3.01 [s, 6 H, N(CH3)2], 3.02 [s, 6 H, N(CH3)2], 3.45 (m,
4 H, pip), 6.15 [d, 3J(H,H) = 4.8 Hz, 1 H, PIT], 6.80–6.83 (m, 4 H,
2ϫ DMA), 7.47–7.53 (m, 6 H, 2ϫDMA, 2ϫ CH, PIT), 7.63 (s, 1
H, CH=) ppm. 13C NMR (100 MHz, CDCl3): δ = 23.8, 25.3, 40.7,
51.2, 100.1, 111.8, 112, 122.9, 126.2, 126.5, 130.7, 130.8, 135.3, 136,
136.7, 137.7, 138.3, 138.4, 150.2, 150.4, 172.0, 190.0, 190.9 ppm.
2-[5-(Piperidin-1-yl)thiophen-2-ylmethylidene]-4,7-diiodoindan-1,3-
dione (25): The title compound was prepared from 5-(piperidin-1-yl)-
thiophene-2-carbaldehyde (21) by following the general method for
Knoevenagel condensation. The product was obtained as an
orange solid (4.14 g, 72%); Rf = 0.25 (CH2Cl2/hexane 3:1). 1H
NMR (400 MHz, CDCl3): δ = 1.66–1.85 (m, 6 H, pip), 3.59–3.62
3
3
(m, 4 H, pip), 6.31 [d, J(H,H) = 4.8 Hz, 1 H, PIT], 7.59 (d, J =
4.8 Hz, 1 H, PIT) 7.63 + 7.64 (2ϫ s, 2 H, 2ϫCH), 7.74 (s, 1 H,
CH=) ppm. 13C NMR (125 MHz, CDCl3): δ = 23.8, 25.7, 51.9,
87.0, 87.3, 108.8, 123.5, 137.6, 141.5, 145.2, 145.4, 151.0, 174.3,
187.8 ppm. HRMS (MALDI, DHB): calcd for C19H16I2NO2S [M
+ H]+ 575.8985; found 575.9000. C19H15I2NO2S (575.2018): calcd.
C 39.67, H 2.63, N 2.44, S 5.57; found C 39.61, H 2.57, N 2.10, S
5.61.
IR (HATR): ν = 3569, 3067, 2354, 1694, 1650, 1607, 1510, 1333,
˜
1178, 1065, 811, 792, 624 cm–1. HRMS (MALDI, DHB): calcd. for
C35H36N3O2S [M + H]+ 562.2522; found 562.2523. C35H35N3O2S
(561.7363): calcd. C 74.83, H 6.28, N 7.48, S 5.71; found C 74.10,
H 6.18, N 7.14, S 5.68.
2-{(2E)-3-[5-(Piperidine-1-yl)thiophen-2-yl]prop-2-en-1-ylidene}-4,7-
bis[4-(dimethylamino)phenyl]indan-1,3-dione (4): The title com-
pound was prepared from 26 and [4-(dimethylamino)phenyl]-
boronic acid pinacol ester by following the general procedure for
Suzuki–Miyaura cross-coupling. The product was obtained as a
dark metallic solid (220 mg, 75%); Rf = 0.3 (CH2Cl2). 1H NMR
(400 MHz, CDCl3): δ = 1.63–1.69 (m, 6 H, pip), 3.01 [s, 6 H,
2-{(2E)-3-[5-(Piperidine-1-yl)thiophen-2-yl]prop-2-en-1-ylidene}-
4,7-diiodoindan-1,3-dione (26): The title compound was prepared
from 3-[5-(piperidin-1-yl)thiophen-2-yl]propenal (22) by following
the general method for Knoevenagel condensation. The product
was obtained as a dark metallic solid (4.98 g, 83 %); Rf = 0.22
3
N(CH3)2], 3.03 [s, 6 H, N(CH3)2], 3.31 [t, J (H,H) = 4.8 Hz, 4 H,
1
3
(CH2Cl2/hexane 3:1). H NMR (400 MHz, CDCl3): δ = 1.72–1.74
pip], 5.99 [d, J(H,H) = 4.4 Hz, 1 H, PIT], 6.79–6.84 (m, 4 H, 2ϫ
(m, 6 H, pip), 3.43 [t, 3J(H,H) = 4.3 Hz, 4 H, pip], 6.11 [d, 3J(H,H)
DMA), 7.08 [d, J(H,H) = 4.4 Hz, 1 H, PIT], 7.22 [d, J(H,H) =
14.0 Hz, 1 H, CH=], 7.39 [d, 3J(H,H) = 12.0 Hz, 1 H, CH=], 7.46–
7.53 (m, 6 H, 2 ϫ DMA, 2 ϫ CH), 7.74 [dd, 3J(H,H) = 12.0,
3J(H,H) = 14.0 Hz, 1 H, CH=] ppm. 13C NMR (100 MHz, CDCl3):
δ = 23.8, 25.2, 40.7, 40.8, 51.4, 100.2, 105.3, 111.8, 118.1, 123.3,
125.9, 126.2, 126.3, 130.7, 130.8, 135.8, 136.3, 137.0, 137.3, 138.4,
138.8, 139.0, 145.0, 145.2, 150.4, 150.5, 165.9, 190.5, 191.0 ppm.
3
3
3
= 4.6 Hz, 1 H, PIT], 7.26 [d, J(H,H) = 4.6 Hz, 1 H, PIT], 7.41 [d,
3
3J(H,H) = 14.0 Hz, 1 H, CH=], 7.52 [d, J(H,H) = 13.0 Hz, 1 H,
CH=], 7.65 + 7.66 (2ϫ s, 2 H, 2 ϫCH), 7.78 [t, 3J(H,H) = 13.0 Hz,
1 H, CH=] ppm. 13C NMR (125 MHz, CDCl3): δ = 23.7, 25.3,
51.7, 87.2, 87.7, 107.2, 117.6, 118.3, 126.4, 140.7, 141.3, 141.6,
145.3, 145.5, 147.6, 148.1, 168.7, 187.2, 187.8 ppm. HRMS
(MALDI, DHB): C21H18I2NO2S [M + H]+ 601.9142; found IR (HATR): ν = 2921, 2852, 1688, 1647, 1558, 1420, 1346, 1158,
˜
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Eur. J. Org. Chem. 2015, 5339–5349

T-Shaped Push–Pull Systems Based on Indan-1,3-dione
1012, 889, 798, 687 cm–1. HRMS (MALDI, DHB): calcd. for
1.73 (m, 6 H, pip), 3.0 [s, 6 H, N(CH3)2], 3.01 [s, 6 H, N(CH3)2],
3
3
C37H38N3O2S [M + H]+ 588.2679; found 588.2683. C37H37N3O2S 3.39 [t, J(H,H) = 4.8 Hz, 4 H, pip], 6.05 [d, J(H,H) = 4.4 Hz, 1
(587.7735): calcd. C 75.61, H 6.34, N 7.15, S 5.46; found C 75.75,
H 6.24, N 7.58, S 5.75.
H, PIT], 6.64–6.71 (m, 4 H, 2ϫ DMA), 7.17 [d, 3J (H,H) = 4.4 Hz,
1 H, PIT], 7.31 [d, 3J(H,H) = 14.0 Hz, 1 H, CH=], 7.51 [d, 3J(H,H)
= 12.0 Hz, 1 H, CH=], 7.54–7.62 (m, 6 H, 2ϫ DMA, 2ϫ CH),
2-[5-(Piperidin-1-yl)thiophen-2-ylmethylidene]-4,7-bis(thiophen-2-
yl)indan-1,3-dione (7): The title compound was prepared from 25
and (thiophen-2-yl)boronic acid by following the general procedure
for Suzuki–Miyaura cross-coupling. The product was obtained as
3
7.84 [dd, 3J(H,H) = 14.0, J(H,H) = 12.0 Hz, 1 H, CH=] ppm. 13C
NMR (125 MHz, CDCl3): δ = 23.8, 25.2, 40.4, 40.5, 51.5, 86.1,
86.2, 98.6, 99.1, 104.4, 105.8, 109.9, 110.0, 111.9, 117.9, 118.3,
118.7, 122.3, 126.4, 133.7, 133.8, 136.4, 136.5, 137.2, 139.8, 140.9,
1
a dark red solid (109 mg, 45%); Rf = 0.2 (CH2Cl2/hexane 3:1). H
145.7, 146.1, 150.6, 150.7, 166.7, 189.6, 189.9 ppm. IR (HATR): ν
˜
NMR (400 MHz, CDCl3): δ = 1.62–1.71 (m, 6 H, pip), 3.49 (m, 4
= 2923, 2852, 1651, 1603, 1568, 1521, 1430, 1350, 1296, 1278, 1160,
1069, 985, 813, 786 cm–1. HRMS (MALDI, DHB): calcd. for
C41H38N3O2S [M + H]+ 636.2679; 636.2691. C41H37N3O2S
(635.8163): calcd. C 77.45, H 5.87, N 6.61, S 5.04; found C 77.63,
H 5.51, N 6.64, S 5.29.
3
H, pip), 6.21 [d, J(H,H) = 4.8 Hz, 1 H, PIT], 7.10–7.21 (m, 2 H,
th), 7.41 [dd, 3J(H,H) = 4.8, 3J(H,H) = 0.8 Hz, 2 H, th], 7.61 +
7.62 (2ϫ s, 2 H, 2ϫ CH), 7.62–7.68 (m, 4 H, PIT, 2ϫ th, CH=)
ppm. 13C NMR (100 MHz, CDCl3): δ = 23.7, 25.5, 51.4, 107.6,
123.0, 126.7, 126.8, 127.3, 127.6, 129.0, 129.5, 131.2, 132.3, 136.7,
137.0, 138.0, 139.2, 139.4, 149.4, 173.0, 189.2, 190.1 ppm. IR
2-[5-(Piperidin-1-yl)thiophen-2-ylmethylidene]-4,7-bis[(thiophen-2-
yl)ethynyl]indan-1,3-dione (15): The title compound was prepared
from 25 and 2-ethynylthiophene by following the general procedure
for Sonogashira cross-coupling. The product was obtained as a
dark metallic solid (155 mg, 58%); Rf = 0.1 (CH2Cl2/hexane 3:1).
1H NMR (500 MHz, CDCl3): δ = 1.72–1.74 (m, 6 H, pip), 3.54–
3.60 (m, 4 H, pip), 6.26 [d, 3J(H,H) = 4.1 Hz, 1 H, PIT], 7.03–7.05
(m, 2 H, th), 7.35 + 7.36 (2ϫ s, 2 H, 2 ϫ CH), 7.43–7.46 (m, 2 H,
th), 7.54 (br s, 1 H, PIT), 7.59–7.63 (m, 2 H, th), 7.74 (s, 1 H, CH=)
ppm. 13C NMR (125 MHz, CDCl3): δ = 23.8, 25.5, 51.6, 89.8, 90.1,
91.1, 91.27, 108.0, 114.6, 117.2, 117.6, 123.2, 123.3, 123.5, 127.4,
127.5, 128.4, 128.7, 129.0, 133.2, 135.9, 136.7, 137.0, 139.8, 140.8,
(HATR): ν = 2928, 2851, 2367, 1691, 1640, 1573, 1457, 1382, 1243,
˜
1174, 1073, 978, 820, 691 cm–1. HRMS (MALDI, DHB): calcd. for
C27H22NO2S3 [M + H]+ 488.0807; found 488.0799. C27H21NO2S3
(487.6564): calcd. C 66.50, H 4.34, N 2.87, S 19.73; found C 66.71,
H 4.25, N 2.78, S 19.64.
2-{3-[5-(Piperidine-1-yl)thiophen-2-yl]prop-2-en-1-ylidene}-4,7-bis-
(thiophen-2-yl)indan-1,3-dione (8): The title compound was pre-
pared from 26 and (thiophen-2-yl)boronic acid by following the
general procedure for Suzuki–Miyaura cross-coupling. The product
was obtained as a dark brown solid (226 mg, 88 %); Rf = 0.25
1
(CH2Cl2/hexane 3:1). H NMR (400 MHz, CDCl3): δ = 1.62–1.68
149.9, 173.3, 188.5, 189.5 ppm. IR (HATR): ν = 2920, 2852, 2358,
˜
(m, 6 H, pip), 3.33 [t, 3J(H,H) = 4.8 Hz, 4 H, pip], 6.01 [d, 3J(H,H)
= 4.4 Hz, 1 H, PIT], 7.13–7.17 (m, 3 H, th), 7.28 [d, 3J(H,H) =
14.0 Hz, 1 H, CH=], 7.41–7.45 (m, 3 H, th), 7.56–7.68 (m, 4 H,
1645, 1568, 1510, 1472, 1415, 1326, 1247, 1176, 1093, 764,
695 cm–1. HRMS (MALDI, DHB): calcd. for C31H22NO2S3 [M +
H]+ 536.0807; found 536.0813. C31H21NO2S3 (535.6989): calcd. C
69.50, H 3.95, N 2.61, S 17.96; found C 69.46, H 3.94, N 2.63, S
17.24.
3
3
PIT, 2ϫ CH, CH=), 7.70 [dd, J(H,H) = 12.0, J(H,H) = 14.0 Hz,
1 H,CH=] ppm. 13C NMR (100 MHz, CDCl3): δ = 23.7, 25.1, 51.5,
106.1, 117.6, 121.3, 126.1, 126.8, 127.0, 127.4, 127.5, 129.1, 129.6,
131.5, 131.9, 135.7, 136.4, 137.1, 138.8, 139.0, 139.1, 139.2, 146.2,
2-{(2E)-3-[5-(Piperidine-1-yl)thiophen-2-yl]prop-2-en-1-ylidene}-
4,7-bis[(thiophen-2-yl)ethynyl]indan-1,3-dione (16): The title com-
pound was prepared from 26 and 2-ethynylthiophene by following
the general procedure for Sonogashira cross-coupling. The product
was obtained as a dark metallic solid (190 mg, 68%); Rf = 0.1
146.7, 167.1, 189.7, 190.0 ppm. IR (HATR): ν = 2919, 2852, 1694,
˜
1648, 1560, 1421, 1347, 1153, 971, 687 cm–1. HRMS (MALDI,
DHB): calcd. for C29H24NO2S3 [M + H]+ 514.0963; found
514.0969. C29H23NO2S3 (513.6934): calcd. C 67.81, H 4.51, N 2.73,
S 18.73; found C 67.97, H 4.59, N 2.41, S 18.72.
1
(CH2Cl2/hexane 3:1). H NMR (400 MHz, CDCl3): δ = 1.68–1.73
3
(m, 6 H, pip), 3.39–3.45 (m, 4 H, pip), 6.08 [d, J(H,H) = 4.0 Hz,
2-[5-(Piperidin-1-yl)thiophen-2ylmethylidene]-4,7-bis[4-(dimethyl-
amino)phenylethynyl]indan-1,3-dione (11): The title compound was
prepared from 25 and 4-ethynyl-N,N-dimethylaniline by following
the general procedure for Sonogashira cross-coupling. The product
1 H, PIT], 7.01–7.13 (m, 2 H, th), 7.23 [d, 3J(H,H) = 16.8 Hz, 1 H,
CH=], 7.33–7.38 (m, 3 H, th, PIT), 7.46–7.48 (m, 2 H, th), 7.54 [d,
3J(H,H) = 15.6 Hz, 1 H, CH=], 7.63 + 7.64 (2ϫ s, 2 H, 2ϫ CH),
7.81 [t, 3J(H,H) = 15.6 Hz, 1 H, CH=] ppm. 13C NMR (125 MHz,
CDCl3): δ = 23.7, 25.2, 51.6, 90.0, 90.4, 91.0, 91.1, 106.4, 117.6,
118.0, 121.0, 123.1, 123.2, 126.3, 127.4, 127.5, 128.6, 128.8, 133.4,
136.3, 137.0, 139.7, 140.1, 141.3, 146.4, 147.0, 167.6, 189.0,
1
was obtained as a red solid (121 mg, 40%); Rf = 0.5 (CH2Cl2). H
NMR (400 MHz, CDCl3): δ = 1.72–1.75 (m, 6 H, pip), 3.0 [s, 6 H,
N(CH3)2], 3.01 [s, 6 H, N(CH3)2], 3.53–3.57 (m, 4 H, pip), 6.23 [d,
3J(H,H) = 4.4 Hz, 1 H, PIT], 6.61–6.69 (m, 4 H, 2ϫ DMA), 7.51–
7.61 (m, 7 H, PIT, 2ϫ DMA, 2ϫ CH), 7.73 (s, 1 H, CH=) ppm.
13C NMR (125 MHz, CDCl3): δ = 23.9, 25.5, 40.3, 40.4, 51.5, 86.2,
86.6, 98.2, 98.6, 110.9, 111.0, 111.2, 111.8, 111.9, 115.7, 117.9,
118.2, 123.2, 128.7, 128.8, 132.2, 133.7, 134.0, 134.1, 136.0, 136.2,
189.3 ppm. IR (HATR): ν = 2921, 2852, 1706, 1654, 1556, 1518,
˜
1351, 1324, 1271, 1208, 1153, 1105, 1049, 875, 848, 689 cm–1.
HRMS (MALDI, DHB): calcd. for C33H24NO2S3 [M + H]+
562.0963; found 562.0972. C33H23NO2S3 (561.7362): calcd. C
70.56, H 4.13, N 2.49, S 17.12; found C 70.52, H 4.21, N 2.43, S
17.09.
137.2, 150.5, 150.6, 153.9, 190.04 ppm. IR (HATR): ν = 2921,
˜
2852, 1644, 1566, 1366, 1362, 1112, 1156, 1055, 755 cm–1. HRMS
(MALDI, DHB): calcd. for C39H36N3O2S [M + H]+ 610.2522;
found 610.2534. C39H35N3O2S (609.7791): calcd. C 76.82, H 5.79,
N 6.89, S 5.26; found C 76.53, H 5.50, N 6.09, S 5.29.
Acknowledgments
This research was supported by the Czech Science Foundation
(grant number 13-01061S).
2-{(2E)-3-[5-(Piperidine-1-yl)thiophen-2-yl]prop-2-en-1-ylidene}-4,7-
bis[4-(dimethylamino)phenylethynyl]indan-1,3-dione (12): The title
compound was prepared from 26 and 4-ethynyl-N,N-dimethylanil-
ine by following the general procedure for Sonogashira cross-cou-
pling. The product was obtained as a dark metallic solid (222 mg,
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70%); Rf = 0.6 (CH2Cl2). H NMR (400 MHz, CDCl3): δ = 1.66–
Eur. J. Org. Chem. 2015, 5339–5349
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5347

F. Buresˇ et al.
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Received: April 24, 2015
Published Online: July 20, 2015
Eur. J. Org. Chem. 2015, 5339–5349
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