Proaromatic pyranylidene chalcogen analogues and cyclopenta[c]thiophen-4,6-dione as electron donors and acceptor in efficient charge-transfer chromophores

Article abstract of DOI:10.1016/j.dyepig.2016.07.008

Fifteen new push-pull chromophores based on a proaromatic pyranylidene donor and its chalcogen analogues and various electron acceptor moieties were synthesized in a straightforward manner. These model molecules were designed and prepared to investigate the concept of proaromaticity as a tool to tune the fundamental properties of push-pull systems. All target chromophores with systematically varied structure were further investigated by electrochemistry, absorption spectra, and EFISH experiment in conjunction with DFT calculations. Employing structural variations such as chalcogen/acceptor replacement, extension of the π-system, and the position of substitution along the pyran ring, the HOMO-LUMO gap can be tuned within the range of 2.18 to 1.41?eV. A new and powerful electron withdrawing moiety, combining features of polarizable thiophene and successful indane-1,3-dione acceptor, cyclopenta[c]thiophen-4,6-dione (ThDione) has also been developed.

Full text of DOI:10.1016/j.dyepig.2016.07.008

Accepted Manuscript
Proaromatic pyranylidene chalcogen analogues and cyclopenta[c]thiophen-4,6-dione
as electron donors and acceptor in efficient charge-transfer chromophores
Parmeshwar Solanke, Sylvain Achelle, Nolwenn Cabon, Oldřich Pytela, Alberto
Barsella, Bertrand Caro, Françoise Robin-le Guen, Jan Podlesný, Milan Klikar, Filip
Bureš
PII:
S0143-7208(16)30314-X
10.1016/j.dyepig.2016.07.008
DYPI 5342
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 24 May 2016
Revised Date: 4 July 2016
Accepted Date: 5 July 2016
Please cite this article as: Solanke P, Achelle S, Cabon N, Pytela O, Barsella A, Caro B, Robin-
le Guen F, Podlesný J, Klikar M, Bureš F, Proaromatic pyranylidene chalcogen analogues and
cyclopenta[c]thiophen-4,6-dione as electron donors and acceptor in efficient charge-transfer
chromophores, Dyes and Pigments (2016), doi: 10.1016/j.dyepig.2016.07.008.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Proaromatic Pyranylidene Chalcogen Analogues and Cyclopenta[c]thiophen-4,6-dione
as Electron Donors and Acceptor in Efficient Charge-Transfer Chromophores.
Parmeshwar Solanke,[a,b] Sylvain Achelle,*[a] Nolwenn Cabon,[a] Oldřich Pytela,[b] Alberto
Barsella,[c] Bertrand Caro,[a] Françoise Robin-le Guen,[a] Jan Podlesný,[b] Milan Klikar,[b] Filip
Bureš.*[b]
[a]Institut des Sciences Chimiques de Rennes UMR CNRS 6226, IUT de Lannion, rue
Edouard Branly, BP 30219, F22302 Lannion Cedex, France. [b]Institute of Organic Chemistry
and Technology, Faculty of Chemical Technology, University of Pardubice, Studentská 573,
Pardubice,
53210,
Czech
Republic
.
[c]Département d’Optique ultra-rapide et
Nanophotonique, IPCMS-CNRS, 23 Rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France
Corresponding authors: *E-mails: sylvain.achelle@univ-rennes1.fr; filip.bures@upce.cz
Abstract
Fifteen new push-pull chromophores based on a proaromatic pyranylidene donor and its
chalcogen analogues and various electron acceptor moieties were synthesized in a
straightforward manner. These model molecules were designed and prepared to investigate
the concept of proaromaticity as a tool to tune the fundamental properties of push-pull
systems. All target chromophores with systematically varied structure were further
investigated by electrochemistry, absorption spectra, and EFISH experiment in conjunction
with DFT calculations. Employing structural variations such as chalcogen/acceptor
replacement, extension of the π-system, and the position of substitution along the pyran ring,
the HOMO-LUMO gap can be tuned within the range of 2.18 to 1.41 eV. A new and powerful
electron withdrawing moiety, combining features of polarizable thiophene and successful
indane-1,3-dione acceptor, cyclopenta[c]thiophen-4,6-dione (ThDione) has also been
developed.
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Keywords: Chalcogenopyranylidene, Push-Pull, Non Linear Optics, Charge Transfer,
Polymethines
1. Introduction
During the past decades, there has been a great interest for molecular systems displaying
second-order nonlinear optical (NLO) responses due to their application in a wide range of
electronic and optoelectronic devices. The most common design of organic chromophores
exhibiting 2nd order NLO properties consists of push-pull systems with an electron-donor
group (D) attached to an electron-accepting group (A) via a π-conjugated core (D-π-A
design).1 Intramolecular charge transfer (ICT) in such D-π-A systems leads to polarization of
the chromophore and generation of a molecular dipole. The ICT can easily be illustrated by
two limiting resonance forms (aromatic and quinoid/zwitterionic arrangement).2 The D–A
interaction generates new low-energy molecular orbital, which accounts for the unique and
peculiar properties of push–pull chromophores such as intensive color, electrochemical
behavior, crystallinity, intermolecular interactions as well as NLO properties.3
Microscopically, the 2nd order nonlinearity of chromophores can be represented by the scalar
product of the vector part of the hyperporalizability tensor (β) and the dipole moment (µ).4
α- and γ-pyranylidene fragments are six membered chalcogen-containing heterocycles which
possess an exocyclic double bond at either the C2 or the C4 positions, respectively. Due to the
presence of an intracyclic heteroatom in conjugation with the unsaturated carbon backbone,
pyranylidenes are considered as good electron-donors depending on the substituent(s)
attached to the C=C exocyclic double bond. The pyranylidene fragment generally acts as
proaromatic electron donor in push-pull molecules,5 which, upon the ICT, gain a pyrylium
aromatic character. Hence, pyranylidene may impart very strong mesomeric effect depending
on the strength of the acceptor group A attached and the length/nature of the unsaturated π-
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spacer used. The donor capacity of pyranylidene fragments is also exemplified by the
chemical or electrochemical oxidation of the methylenepyran moiety leading to a radical
cation which dimerizes to bispyrylium and extended bispyrans.6 Incorporation of
pyranylidene fragment within the structure of NLOphores7 and organic chromophores for dye
sensitized solar cells (DSSCs)8 has already been described in the literature. However,
replacement of chalcogen atoms within the γ-pyranylidene fragment has been much less
studied.9 In addition, α-pyranylidene fragments have never been used in a push-pull structure
for NLO.
Activated methylene derivatives such as malononitrile,10 indane-1,3-dione (and their
dicyanovinyl analogues),11 (thio)barbituric acid12 and Meldrum’s acid13 have extensively been
used as electron-withdrawing groups in push-pull molecules, while one of the highest µβ
values were obtained for indane-1,3-dione and dicyanovinyl end-capped push-pull
chromophores.14 To the best of our knowledge, indane-1,3-dione-inspired
cyclopenta[c]thiophen-4,6-dione (ThDione) has never been used in push-pull molecules as
electron acceptor.
The aim of this research is to study the influence of various parameters affecting the ICT in
model pyranylidene chromophores 1–15 by UV-Vis spectroscopy, electrochemistry, DFT
calculation, and electric-field induced second harmonic (EFISH) experiments. The studied
parameters are the nature of the intracyclic chalcogen atom (oxygen, sulfur and selenium), the
position of substitution along the pyran ring (α- and γ-pyranylidenes), the length of the
polyene π-conjugated bridge (ethylene, butadiene), and electron withdrawing nature of the
acceptor (indane-1,3-dione, ThDione, N,N-dibutylbarbituric acid, N,N-dibutylthiobarbituric
acid, and Meldrum’s acid).
2. Results and discussion
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2.1. Synthesis
Targeted push-pull derivatives 1–15 were prepared by Al2O3-catalyzed Knoevenagel
condensations between (chalcogeno)pyranylidene aldehydes 16–20 and activated methylene
derivatives in moderate to good yields (Schemes 1-3).11a,15 Pyranylidene aldehydes 16, 19,
and 2016 and chalcogen analogues 17–189a were obtained according to literature procedures.
Nonsymmetrical α-pyranylidene aldehyde 20 was obtained as an inseparable mixture of two
stereoisomers. It should be noted that the E/Z ratio change for each product after purification
by chromatography. Hence, the Knoevenagel condensation of 20 with activated methylene
derivatives leads also to mixtures of two inseparable stereoisomers 13–15. For compounds 8–
12 with extended π-conjugated linker, the central double bond exhibits exclusively (E)-
1
3
configuration as proved by H NMR spectroscopy with J(H,H) equal to 12-13 Hz for the
vinylic protons. The electron withdrawing moieties in 1–15 were represented by indane-1,3-
dione, cyclopenta[c]thiophen-4,6-dione 21, N,N’-dibutyl(thio)barbituric12b and Meldrum’s
acid. The synthesis of ThDione 21 is outlined in Scheme 4. A treatment of commercially
available thiophene-3,4-dicarboxylic acid with acetic anhydride afforded the corresponding
anhydride17 which further underwent Claisen condensation with ethyl acetoacetate (EAA) and
subsequent acid-catalyzed decarboxylation. In this way, ThDione can conveniently be
synthesized in 54% overall yield.
<Scheme 1>
<Scheme 2>
<Scheme 3>
<Scheme 4>
All new compounds are well soluble in THF, chloroform, and dichloromethane and were
characterized by a variety of analytical techniques such as 1H and 13C NMR, IR, and HR-MS.
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2.2. Electrochemistry
Electrochemical behavior of target compounds 1–15 was studied by cyclic voltammetry in
CH2Cl2 containing Bu4NPF6 electrolyte at a scan rate of 0.1 V/s. The working electrode was a
glassy carbon disk, tungsten wire was used as the counter electrode, and a non-aqueous
Ag/AgCl electrode was used as reference. The first oxidation/reduction peak potentials and
their differences are listed in Table 1, representative CV diagrams of 4, 9, and 14 are shown in
the SI.
<Table 1>
The first oxidation/reduction potentials of 1–15 range from 0.28 to 0.77 and –1.43 to –1.18 V,
respectively, and are obviously a function of the chromophore structure. From the
electrochemical data shown in Table 1 we can deduce the following general structure-
property relationships:
•
O
→
S or O
oxidation.
in the order O→S→Se. As a consequence a gradual narrowing of the electrochemical
gap E is observed ∆E (1.91 1.74 1.70).
→
Se replacement in pyranylidene donors 1–3 slightly facilitated the first
For these compounds, reduction process is easier
∆
→
→
•
•
A systematic variation of the peripheral acceptor within the order of ThDione (4),
indan-1,3-dione (1), thiobarbituric acid (6), barbituric acid (5), and Meldrum’s acid (7)
also affected both oxidation and reduction potentials and allowed tuning of the gap ∆E
from 1.85 to 2.18 V. A similar trend can be seen within the series 8–12.
Considering the electrochemical data of structural analogues 1 and 4–7 and 8–12, the
newly developed ThDione and the thiobarbituric acid proved to be the strongest electron
acceptors.
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•
In comparison to 1, 4–7 (∆E = 1.85-2.18 V), extension of the π-system by an additional
olefinic unit as in 8–12 (∆E = 1.41-1.64 V) reduced the electrochemical gap
significantly.
•
•
Shifting the position of the acceptor-terminated π-linker from γ to α position along the
electron donating pyranylidene fragment narrowed the electrochemical gap within the
limit of 0.18–0.23 V.
Employing the aforementioned structural variations, the electrochemical gap in 1–15
can be tuned within the range of 2.18 to 1.41 V, with the lowest gap measured for
chromophore 9 featuring ThDione acceptor and extended π-linker.
2.3. UV-Vis spectroscopy
All target compounds are highly colored with the color ranging from orange, red to blue
(Figure 1). The UV-Vis electronic spectra of compounds 1–15 were recorded in
dichloromethane and the results are given in Table 1. In general, three absorption bands were
observed for chromophores 1–12. The two more intense bands localized in the visible part of
the spectra (λmax= 498–673 nm) are attributed to the ICT (listed in Table 1). Representative
spectra are shown in Figure 2. Due to the presence of two stereoisomers, spectra of 13–15
feature six absorption bands. It should be noted that none of the studied compounds exhibited
significant emission properties.
<Figure 1>
<Figure 2>
The positions of the CT absorption bands are clearly dependent on the structure of the
chromophores. Concerning the CT bands, the following structure-property relationships can
be highlighted:
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•
•
•
A replacement of pyranylidene donor by its chalcogen (sulfur and selenium) analogues
leads to a bathochromic shift (e.g. 1–3, Figure 2a).
A chalcogen exchange within the (thio)barbituric acceptor has a similar influence (e.g.
5/6 or 10/11).
The used acceptor moieties can be ordered according the position of the longest-
wavelength absorption maxima in the following way (Figure 2b): Meldrum’s acid (7 and
12) < barbituric acid (5 and 10) < indane-1,3dione (1 and 8) < thiobarbituric acid (6 and
11) < ThDione (4 and 9).
•
•
Among the studied acceptors, novel ThDione and thiobarbituric acid impart the strongest
ICT in the push-pull molecules.
Compared to 1, 4-7, chromophores 8–12 with the extended
λmax by about 100 nm (Figure 2c).
π-linker showed red-shifted
•
•
In accordance with the electrochemical observations, the absorption maxima of α-
pyranylidenes 13–15 are red-shifted compared to γ-pyranylidene derivatives 1, 4–5
(Figure 2d).
By varying the structure, the optical properties of 1–15 can be tuned within the range of
498(2.49)/673(1.84) nm(eV).
In term of relationships between optical and electrochemical properties, the general trend
(except for compounds 3, 11, 14 and 15) is the lower the HOMO-LUMO gap, the more red-
shifted the absorption CT band.
2.4. EFISH Experiments
Second-order non-linear properties were studied in CHCl3 solution using the electric-field-
induced second-harmonic generation technique (EFISH), which provides information about
the scalar product µ
β
(2ω) of the vector component of the first hyperpolarisability tensor β
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and the dipole moment vector.18 This product is derived according to equation 1 and
considering γ0(-2ω,ω,ω,0), the third-order term, as negligible for the push-pull compounds
under consideration. This approximation is usually used for push-pull organic and
organometallic molecules.
γEFISH = µ
β
/5kT + γ0(-2ω,ω,ω,0)
Eq. 1
Measurements were performed at 1907 nm, obtained from a Raman-shifted Nd:YAG laser
source, which allowed us to work in conditions far from the resonance peaks of 1–15. It
should be noted that the sign and values of µβ depend on the “direction” of the transition
implied in the NLO phenomena and on the direction of the ground-state dipole moment.
When β and ꢀ are parallel (antiparallel), positive (negative) maxima ꢀβ values are reached.
Except for compound 6, all the µβ values (Table 2) are positive. In addition, this also implies
that the ground and excited states are polarized in the same direction. The negative value
observed for 6 indicates that zwitterionic arrangement of 6 is slightly predominant and a
location in the C region of the Marder's plot.19 This is in accordance with the value measured
by Andreu and coworkers for a di-tert-butyl-substituted pyranylidene chromophore with
N,N’-diethylthiobarbituric acid acceptor.7h Due to small positive µβ values measured for
chromophores 5 and 15, these compounds are also located close to the C region of the
Marder's plot. As can be seen from the data gathered in Table 2, replacement of the oxygen
atom by S or Se atom within the pyranylidene donor (compounds 1–3) increases the µ
β
values despite the decrease of the ground state dipole moment value as observed previously.9c
A chalcogen replacement (O→S) within the (thio)barbituric acceptors has also a significant
impact on the NLO responses (e.g. 5/6 or 10/11). In general, the effect of attaching various
electron-withdrawing moieties mimics the trends seen for the linear optical properties (Table
1), especially within the series 8–12 with the extended π-linker. Hence, the largest
nonlinearities were measured for ThDione- and thiobarbituric acid-terminated chromophores
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4/9 and 11, respectively. From the data in Table 2 it is also clear that the length of the polyene
π-conjugated bridge is the crucial parameter affecting the µβ values. Compared to ethylene
analogues, a strong enhancement of the NLO response is observed for butadiene derivatives
(e.g. 8 vs 1, 9 vs 4, 10 vs 5, 11 vs 6, and 12 vs 7). α-Pyranylidene derivatives 13–15 exhibited
µβ values within the same range as analogous γ-pyranylidene derivatives (e.g. 1 vs. 13, 4 vs.
14, and 5 vs. 15).
<Table 2>
2.5. DFT Calculations
Spatial and electronic properties of all target chromophores 1–15 were investigated by DFT
calculations using Gaussian W09 package.20 Initial geometries were estimated by PM3
method implemented in ArgusLab21 and these were subsequently optimized by the DFT
B3LYP/6-311++G(2d,p) method. Energies of the HOMO and the LUMO, their differences,
ground state dipole moments, and the second-order polarizabilities were calculated with the
DFT B3LYP/6-311++G(2d,p) level. All calculated data are summarized in Table 2. The
calculated energies of the HOMO/LUMO range from –5.89/–5.45 to –3.13/–2.87 eV. Both
energies correlate very tightly with the experimental HOMO/LUMO levels obtained from the
electrochemical measurements (see the SI). The calculated HOMO-LUMO gaps (∆EDFT) were
found within the range from 2.97 to 2.38 eV (max. difference 0.6 eV) and showed even
tighter correlation with the experimentally obtained electrochemical and optical gaps (see the
SI). Hence, the used DFT method can be considered as a reasonable tool for the description of
electronic properties of 1–15. As a consequence, very similar trends as deduced from the
electrochemical data and positions of the longest-wavelength absorption maxima can also be
seen from the calculated data. Namely, ∆EDFT depends primarily on the π-linker extension,
character of the acceptor attached, chalcogen atom involved in the pyranylidene donor as well
as in the (thio)barbituric acceptor, substitution of the pyranylidene fragment (γ and α), and
9

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also by the double bond conformation. Length of the π-linker affected the calculated HOMO
and LUMO energies and their differences most significantly (e.g. 1 vs 8; 4 vs 9; 5 vs 10; 6 vs
11 or 7 vs 12, Table 2). Replacing the peripheral acceptor affected the ∆EDFT within a limit of
about 0.2–0.3 eV (e.g. 1, 4–7 or 8–12). Within the particular three subseries, ThDione-
terminated chromophores 4, 9, and 14 showed the lowest HOMO-LUMO gaps. The increased
polarizability and molecular weight of the chalcogen atom involved in pyranylidene fragment
(O→S→Se) lowered ∆EDFT in 1–3. In general, Z-isomers of α-pyranylidenes 13–15 possess
lower calculated total energies and thus can be considered as energetically preferred. In
Z-configured 13–15 is the pyranylidene oxygen atom in a close proximity of the adjacent
olefinic hydrogen, which may imply higher stabilization of this isomer via H-bonding. Hence,
narrowed HOMO-LUMO gaps were calculated for Z isomers. In accordance with the
electrochemical measurements, the α-substituted pyranylidene chromophores 13–15 showed
lower gaps when compared to γ-pyranylidenes 1, 4, and 5.
<Figure 3>
Representative visualizations of the HOMO and LUMO localizations for chromophores 4, 8,
and (Z)-15 are depicted in Figure 3. For complete listing see the SI. As a general trend, the
HOMO as well the HOMO–1 is localized on the π-linker connecting both pyranylidene
fragment and the given acceptor. Both orbitals are also partially spread over β- and γ-carbon
atoms of the pyrane ring. The LUMO in 4 and 8 is localized not on the acceptor but rather on
the π-linker and α-carbon atoms of the pyrane, whereas the LUMO+1 is completely localized
on the diphenylpyran moiety. This is conversely to α-pyranylidene derivatives e.g. (Z)-15.
Despite these counterintuitive results, these observations are in accordance with those
observed for other proaromatic pyranylidene chromophores7g and imply that 1–15 are strongly
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polarized with the pyranylidene donor adopting positively charged pyrylium character. The
calculated ground state dipole moments of 1–15 (Table 2) range from about 7 to 18 D with the
highest ones computed for chromophores 6 and 11 bearing an N,N´-dibutyl-2-thiobarbituric
acceptor. On the contrary, chromophores 1–3, 8, and 13 with attached indane-1,3-dione
showed the lowest values. Molecular second order optical nonlinearities
1907 nm either in vacuum or CHCl3. The computed (-2ω;ω,ω) values are given in Table 2.
Generally higher coefficients were calculated in CHCl3 than in vacuum. Within the
β were calculated at
β
β
particular subseries 1–3, 1–7, 8–12, and 13–15 the calculated second-order polarizabilities
mimic the trends seen for the experimentally obtained µβ values. When going from 1 to 3, the
chalcogen replacement within the pyranylidene fragment slightly improved the optical
nonlinearities. Similarly to EFISHG measured µβ values, the largest optical nonlinearities
were calculated for chromophores 8–12 with the extended butadiene π-conjugated bridge.
Hence, the length of the π-linker seems to be the most crucial factor affecting optical
nonlinearities of target compounds. On the contrary, when going from 6 to 11 a slight
decrease of the calculated
β coefficients has been observed. The highest β values were
calculated for extended chromophores 8–12 and ThDione seems to be the most suited
acceptor moiety delivering the highest calculated nonlinearity in 9 (β
= 233/103 × 10-30 esu).
3. Conclusion
Starting from three types of pyranylidene aldehydes and their chalcogen analogues, we have
prepared fifteen new push-pull D-π-A compounds 1–15. Property tuning has been achieved
by variation of the acceptor moiety, extension of the π-linker, chalcogen replacement within
the pyranylidene as well as in (thio)barbituric fragments, and substitution of the pyranylidene
donor. These structural changes allowed tuning of the electrochemically measured HOMO-
LUMO gap within the range of 2.18 to 1.41 eV, the optical gap can be tuned from 498(2.49)
11

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to 673(1.84) nm (eV). The employed electron withdrawing moieties include novel ThDione,
N,N’-dibutyl(thio)barbituric acids, indane-1,3-dione, and Meldrum’s acid. ThDione and
thiobarbituric acid impart the strongest ICT into proaromatic systems and can be considered
as strongest acceptors within the studied series. Thorough structure-property relationships
were elucidated from both experimental as well as calculated data. Both approaches suggest
charge-separated (zwitterionic) ground-state character of 1–15 as evidenced by the
electrochemistry, absorption spectra, and DFT. The optical nonlinearities of 1–15 measured
by EFISH experiments showed trends in accordance to the ICT efficiency. Namely, the
highest NLO responses were observed for the chromophores bearing ThDione and
thiobarbituric acceptors and extended π-system. In view of the current interest push-pull
molecules with enhanced ICT, this fundamental research provides the impetus for further
application of proaromatic pyranylidene-derived chromophores and novel ThDione acceptor
in molecular electronics.
4. Experimental Section
General. Reagent-grade reagents and solvents were purchased from Sigma-Aldrich, Acros,
TCI Europe and Alfa Aesar and used as received. Pyranylidene aldehyde and their chalcogen
analogues were obtained according to reported procedures.9a,16 Column chromatography was
performed with silica gel 60 (Macherey-Nagel, particule size 0.040-0.063 nm, 230-400 mesh)
and indicated solvent. TLC was conducted with aluminum sheets coated with silica gel 60
F254 (Merck or Macherey Nagel) with visualization by a UV lamp (254 and 360 nm). NMR
spectra were acquired at room temperature on a Bruker AC-300, AVANCE 400 or AVANCE
500 spectrometer. Chemical shifts are given in parts per million relative to TMS (1H, 0.0
ppm) and CDCl3 (13C, 77.0 ppm). Acidic impurities in CDCl3 were removed by treatment
with anhydrous K2CO3. For compounds 13-15, identification of the two isomers is based on
NOESY analysis performed on similar push-pull α-pyranylidene push-pull derivatives
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(unpublished results). High resolution mass analyses were performed at the “Centre Régional
de Mesures Physiques de l’Ouest” (CRMPO, University of Rennes1) using a Bruker
MicroTOF-Q II apparatus. 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, 60Hz). The matrix was 2,5-dihydroxybenzoic acid (DHB). More details
concerning MALDI HRMS analysis are given elsewhere.11a Elemental analyses were
performed with an EA 1108 Fisons instrument. IR spectra were recorded on either a Perkin–
Elmer spectrum1000 FTIR using KBr plates or Nicolet 6700 with single-bounce diamond
ATR. UV/vis spectra were recorded with a UVIKON xm SECOMAM spectrometer using
standard 1 cm quartz cells. Cyclic voltammetric experiments were performed in a three
electrodes cell using a potentiostat (Autolab PGSTAT 12) driven by the GPES software. The
working electrode consisted of a vitreous carbon disk. The Ag/Ag+ reference electrode was
separated from the analyte by a CH2Cl2–[NBu4][PF6] bridge. All the potentials are quoted
against the ferrocene–ferrocenium couple; ferrocene was added as an internal standard at the
end of each experiment.
General procedure for the synthesis of push-pull derivatives: The corresponding activated
methylene derivative (1.00 mmol) and the corresponding pyranylidene aldehyde (1.00 mmol)
were dissolved in CH2Cl2 (5 mL), Al2O3 activity II-III (510 mg, 5.00 mmol) was added and
the reaction was stirred at room temperature for 3 h (24 h for 13–15). Al2O3 was then filtered
off, the solvent was evaporated in vacuo and the crude product was purified by column
chromatography over SiO2.
2-[2-(2,6-Diphenyl-pyran-4-ylidene)-ethylidene]-indan-1,3-dione (1): Purified by column
chromatography (CH2Cl2/petroleum ether, 2:1). Dark solid (160 mg, 40 %). Mp > 260 °C. 1H
NMR (300 MHz, CDCl3):
δ = 6.97 (d, 1H, J = 1.5 Hz), 7.48 (s, 2H), 7.52-7.57 (m, 6H), 7.65-
7.68 (m, 2H), 7.83-7.88 (m, 4 H), 8.08 (d, 1H, J = 13.8 Hz) ppm. 13C NMR (75 MHz, CDCl3):
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δ
= 103.5 (CH), 110.4 (CH), 111.8 (CH), 120.3 (C), 121.8 (CH), 122.1 (CH), 125.0 (CH),
125.8 (CH), 129.1 (CH), 131.2 (CH), 131.3 (CH), 131.4 (C), 131.6 (C), 133.7 (CH), 133.8
(CH), 138.8 (CH), 140.5 (C), 142.0 (C), 149.8 (C), 157.8 (C), 157.6 (C), 191.6 (C), 191.9 (C)
ppm. IR (KBr):
ν = 2922 (C-H), 1699 (C=O), 1654 (C=C), 1492 (C-O), 1451, 1208, 1152,
941, 728 (=C-H), 678 (=C-H) cm-1. HRMS (ESI/ASAP) m/z calculated for C28H19O3 [M+H]+
403.1329, found 403.1321
2-[2-(2,6-Diphenyl-thiopyran-4-ylidene)-ethylidene]-indan-1,3-dione (2): Purified by
column chromatography (ethyl acetate/petroleum ether, 1:1). Dark solid (177 mg, 42 %). Mp
1
> 260 °C. H NMR (300 MHz, CDCl3):
δ
=7.31 (s, 1H), 7.48-7.53 (m, 6H), 7.63-7.72 (m,
13
7H), 7.84-7.86 (m, 3 H), 8.11 (d, 1H, J = 13.8 Hz) ppm. C NMR (75 MHz, CDCl3):
δ =
118.4 (CH), 119.7 (CH), 121.3 (C), 121.9 (CH), 122.2 (CH), 126.5 (CH), 126.8 (CH), 127.1
(CH), 129.3 (CH), 130.5 (CH), 130.6 (CH), 133.8 (CH), 134.0 (CH), 136.4 (C), 136.7 (C),
137.8 (CH), 140.6 (C), 142.2 (C), 145.5 (C), 147.0 (C), 150.5 (C), 191.3 (C), 191.7 (C) ppm.
IR (KBr):
ν
= 1661 (C=O), 1509 (C-S), 1352, 1324, 1228, 986, 751 (=C-H) cm-1. HRMS
(ESI/ASAP) m/z calculated for C28H18O2NaS [M+Na]+ 441.0925, found 441.0927
2-[2-(2,6-Diphenyl-selenopyran-4-ylidene)-ethylidene]-indan-1,3-dione (3): Purified by
column chromatography (ethyl acetate/petroleum ether, 1:1). Dark solid (264 mg, 57 %). Mp
1
> 260 °C. H NMR (300 MHz, CDCl3):
δ = 7.37 (s, 1H), 7.48-7.52 (m, 6H), 7.58-7.63 (m,
4H), 7.68-7.71 (m, 2H), 7.82-7.90 (m, 4H), 8.17 (d, 1H, J = 13.8 Hz) ppm. 13C NMR (75
MHz, CDCl3): = 120.5 (CH), 121.7 (CH), 122.1 (C), 122.2 (CH), 122.4 (CH), 126.5 (CH),
δ
126.9 (CH), 128.4 (CH), 129.4 (CH), 130.3 (CH), 130.4 (CH), 134.0 (CH), 134.1 (CH), 137.7
(CH), 138.3 (C), 138.6 (C), 140.7 (C), 142.3 (C), 148.0 (C), 148.6 (C), 150.9 (C), 191.3 (C),
191.7 (C) ppm. IR (KBr):
ν
= 1663 (C=O), 1529 (C=C), 1351, 1209, 729 (=C-H) cm-1.
HRMS (ESI/ASAP) m/z calculated for C28H18O2Na80Se [M+Na]+ 489.0370, found 489.0370.
14

ACCEPTED MANUSCRIPT
5-(2-(2,6-Diphenyl-4H-pyran-4-ylidene)ethylidene)-4H-cyclopenta[c]thiophene-4,6(5H)-
dione (4): Purified by column chromatography (ethyl acetate/hexane, 1:1). Dark solid (300
mg, 73 %). Mp 300–305 °C. 1H NMR (500 MHz, CDCl3):
δ = 7.00 (d, 1H, J = 1.5 Hz), 7.49
(d, 2H, J = 13.5 Hz), 7.52-7.55 (m, 6H), 7.74-7.76 (m, 2H), 7.85-7.87 (m, 2H), 7.92-7.94 (m,
13
2H), 8.05 (d, 1H, J = 13.5 Hz) ppm. C NMR (125 MHz, CDCl3):
δ = 104.0 (CH), 110.9
(CH), 112.1 (CH), 123.0 (CH), 123.3 (CH), 125.8 (CH), 126.1 (CH), 128.5 (C), 129.4 (CH),
129.5 (CH), 131.4 (C), 131.5 (CH), 131.6 (CH), 131.7 (C), 140.6 (CH), 146.5 (C), 147.7 (C),
150.8 (C), 158.4 (C), 158.6 (C), 184.9 (C), 185.5 (C) ppm. IR (KBr):
ν = 2953 (C-H), 1651
(C=O), 1455 (C-O), 1159 cm-1. HRMS (MALDI) m/z calculated for C26H17O3S [M+H]+
409.0898, found 409.0901. Anal. Calcd for C26H16O3S: C, 76.45; H, 3.95; S, 7.85. Found: C,
75.98; H, 3.94; S, 8.20.
1,3-Dibutyl-5-(2-(2,6-diphenyl-4H-pyran-4-ylidene)ethylidene)pyrimidine-
2,4,6(1H,3H,5H)-trione. (5): Purified by column chromatography (CH2Cl2/hexane, 3:1).
Dark solid (451 mg, 91 %). Mp 281–284 °C. 1H NMR (400 MHz, CDCl3):
δ = 0.93-0.97 (m,
6H), 1.35-1.42 (m, 4H), 1.59-1.66 (m,4H), 3.91-3.97 (m, 4H), 6.99 (s, 1H), 7.51-7.54 (m,
7H), 7.68 (d, 1H, J = 14.0 Hz), 7.81-7.84 (m, 2H), 7.89-7.92 (m, 2H), 8.65 (d, 1H, J = 14.0
Hz) ppm. 13C NMR (125 MHz, CDCl3):
δ = 14.0(CH3), 20.5(CH2), 20.6(CH2), 30.5(CH2),
30.6(CH2), 41.2(CH2), 41.8(CH2), 104.2 (CH), 105.5 (C), 111.9 (CH), 113.2 (CH), 125.8
(CH), 126.1 (CH), 129.4 (CH), 129.5 (CH), 131.2 (C), 131.4 (C), 131.8 (CH), 131.9 (CH),
149.2 (CH), 151.7 (C), 152.9 (C), 159.0 (C), 159.2 (C), 163.0 (C), 163.8 (C) ppm. IR (KBr):
1653 (C=O), 1538 (C=C), 1477 (C-O), 1223 cm-1. HRMS (MALDI) m/z calculated for
C31H33N2O4 [M+H]+ 497.2434, found 497.2455. Anal. Calcd for C31H32N2O4: C, 74.98; H,
6.50; N, 5.64. Found: C, 74.81; H, 6.47; N, 5.60.
1,3-Dibutyl-5-(2-(2,6-diphenyl-4H-pyran-4-ylidene)ethylidene)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione. (6): Purified by column chromatography
15

ACCEPTED MANUSCRIPT
1
(CH2Cl2/hexane, 3:1). Dark solid (261 mg, 51 %). Mp 294–297 °C. H NMR (500 MHz,
CDCl3): = 0.95-0.97 (m, 6H), 1.39-1.43 (m, 4H), 1.71-1.73 (m, 4H), 4.47-4.8 (m, 4H), 7.08
δ
(s, 1H), 7.24 (s, 1H), 7.54-7.60 (m, 6H), 7.77 (d, 1H, J = 14.0 Hz), 7.85 (d, 2H, J = 6.2 Hz),
13
7.93 (d, 2H, J = 6.2 Hz), 8.67 (d, 1H, J = 14.0 Hz) ppm. C NMR (125 MHz, CDCl3):
δ =
14.1 (CH3), 20.5 (CH2), 20.6 (CH2), 29.4 (CH2), 29.9 (CH2), 47.8 (CH2), 48.3 (CH2), 104.9
(CH), 106.0 (C), 111.7 (CH), 114.4 (CH), 126.0 (CH), 126.3 (CH), 129.5 (CH), 129.6 (CH),
130.9 (C), 131.0 (C), 131.1(CH), 132.2 (CH), 150.0 (CH), 154.6 (C), 160.0 (C), 160.4 (C),
161.2 (C), 162.5 (C), 179.1 (C) ppm. IR (ATR):
ν = 1638 (C=O), 1482 (C-O), 1372, 1342,
1225 (C=S), 1180, 1120, 927, 766 (=C-H), 682 (=C-H) cm-1. HRMS (MALDI) m/z calculated
for C31H33N2O3S [M+H]+ 513.2206, found 513.2211. Anal. Calcd for C31H32N2O3S: C, 72.63;
H, 6.29; N, 5.46; S, 6.25. Found: C, 72.93; H, 6.67; N, 6.60; S, 6.48.
5-(2-(2,6-Diphenyl-4H-pyran-4-ylidene)ethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione
(7): Purified by column chromatography (ethyl acetate/hexane, 1:1). Dark solid (272 mg, 68
%). Mp: 255–257 °C. 1H NMR (500 MHz, CDCl3):
δ = 1.72 (s ,6H), 6.99 (d, 1H, J = 1.7 Hz),
7.38 (d, 1H, J = 14.0 Hz), 7.45 (d, 1H, J = 1.7 Hz), 7.50-7.55 (m, 6H), 7.82-7.84 (m, 2H),
13
7.88-7.91 (m, 2H), 8.56 (d, 1H, J = 14.0 Hz) ppm. C NMR (125 MHz, CDCl3):
δ = 27.4
(CH3), 99.7 (C), 103.8 (C), 104.1 (CH), 110.9 (CH), 112.8(CH), 125.9 (CH), 126.1(CH),
129.4(CH), 129.5 (CH), 131.0 (C), 131.2(C), 131.9 (CH), 149.9 (CH), 153.1 (C), 159.3 (C),
159.6 (C), 162.9 (C), 165.4 (C) ppm. IR (ATR):
ν = 1690 (C=O), 1648 (C=C), 1524, 1484 (C-
O), 1365, 1235, 1157, 945, 884, 765 (=C-H), 682 (=C-H) cm-1. HRMS (MALDI) m/z
calculated for C25H20O5 M+˙ 400.1305, found 400.1317. Anal. Calcd for C25H20O5: C, 74.99;
H, 5.03; Found: C, 74.91; H, 5.19.
2-[4-(2,6-Diphenyl-pyran-4-ylidene)-but-2-enylidene]-indan-1,3-dione (8): Purified by
column chromatography (CH2Cl2/petroleum ether, 2:1). Dark solid (107 mg, 25 %). Mp > 260
1
°C. H NMR (300 MHz, CDCl3):
δ
= 6.08 (d, 1H, 12 Hz), 6.62 (d, 1H, J = 1.5 Hz), 7.03 (d,
16

ACCEPTED MANUSCRIPT
1H, J = 1.2 Hz), 7.47-7.53 (m, 6H), 7.58 (d, 2H, J = 12.0 Hz), 7.64-7.67(m, 2H), 7.72 (s, 1H),
7.77-7.83 (m, 6H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 103.1 (CH), 109.3 (CH), 115.9
(CH), 122.0 (CH), 122.2 (CH), 122.9 (CH), 123.8 (C), 125.1 (CH), 125.3 (CH), 128.9 (CH),
129.0 (CH), 130.5 (CH), 130.6 (CH), 131.8 (C), 132.0 (C), 133.9 (CH), 134.1 (CH), 140.8
(C), 141.3 (C), 142.1 (C), 145.4 (CH), 148.5 (CH), 155.6 (C), 155.8 (C), 191.0 (C), 191.2 (C)
ppm. IR (KBr):
ν = 2342 (C-H), 1669 (C=O), 1597, 1540, 1371, 1330, 1176, 1023, 937, 728
(=C-H), 670 (=C-H) cm-1. HRMS (ESI/ASAP) m/z calculated for C30H21O3 [M+H]+
429.1485, found 429.1480.
(E)-5-(4-(2,6-Diphenyl-4H-pyran-4-ylidene)but-2-en-1-ylidene)-4H-
cyclopenta[c]thiophene-4,6(5H)-dione (9): Purified by column chromatography (ethyl
1
acetate/hexane, 1:1). Dark solid (217 mg, 50 %). Mp: 275–278 °C. H NMR (500 MHz,
CDCl3):
δ = 6.09 (d, 1H, J = 12.5 Hz), 6.65 (d, 1H, J = 1.5 Hz), 7.05 (s, 1H), 7.48-7.59 (m,
8H), 7.72-7.81 (m, 7H) ppm. 13C NMR (125 MHz, CDCl3):
δ
= 103.5 (CH), 109.7 (CH),
116.3 (CH), 123.5 (CH), 123.6(CH), 123.9 (CH), 125.3 (CH), 125.4 (CH), 125.6 (CH), 129.2
(CH), 129.3 (CH), 130.8 (CH), 130.9 (CH), 131.0 (CH), 131.9 (C), 132.1 (C), 142.4 (C),
146.6 (C), 147.2 (C), 147.3 (CH), 147.6 (C), 149.3 (CH), 156.2 (C), 156.3 (C), 184.4 (C),
184.8 (C) ppm. IR (KBr): 2953 (C-H), 1644 (C=O), 1507 (C=C), 1488 (C-O), 1228 cm-1.
HRMS (MALDI) m/z calculated for C28H19O3S [M+H]+ 435.1055, found 435.1069. Anal.
Calcd for C28H18O3S: C, 77.40; H, 4.18; S, 7.38. Found: C, 77.76; H, 4.47; S, 7.40.
(E)-1,3-Dibutyl-5-(4-(2,6-diphenyl-4H-pyran-4-ylidene)but-2-en-1-ylidene)pyrimidine-
2,4,6(1H,3H,5H)-trione. (10): Purified by column chromatography (CH2Cl2/hexane, 3:1).
Dark solid (224 mg, 43 %). Mp: 216–219 °C. 1H NMR (400 MHz, CDCl3):
δ = 0.91-0.96 (m,
6H), 1.34-1.43 (m, 4H), 1.58-1.62 (m, 4H), 3.90-3.95 (m, 4H), 6.07 (d, 1H, J = 12.0 Hz), 6.68
(d, 1H, J = 1.6 Hz), 7.11 (d, 1H, J = 1.6 Hz), 7.48-7.53 (m, 6H), 7.68 (dd, 1H, J1 =13.2 Hz, J2
=12.0 Hz), 7.81-7.87 (m, 4H), 7.92 (dd, 1H, J1 =13.2 Hz, J2 =12.0 Hz), 8.11 (d, 1H, J = 12.0
17

ACCEPTED MANUSCRIPT
Hz) ppm. 13C NMR (125 MHz, CDCl3):
δ
= 14.0 (CH3), 20.4 (CH2), 20.5 (CH2), 30.5 (CH2),
30.6 (CH2), 41.2 (CH2), 41.8 (CH2), 104.0 (CH), 108.3 (C), 109.8 (CH), 116.1 (CH), 125.0
(CH), 125.5 (CH), 125.6 (CH), 129.2 (CH), 129.3 (CH), 131.0 (CH), 131.1(CH), 131.8(C),
132.0 (C), 143.8 (C), 151.7 (C), 151.9 (CH), 156.7(C), 156.9 (CH), 162.5 (C), 163.2 (C) ppm.
IR (KBr): 1647 (C=O), 1484 (C-O), 1396, 1174 cm-1. HRMS (MALDI) m/z calculated for
C33H35N2O4 [M+H]+ 523.2591, found 523.2593. Anal. Calcd for C33H34N2O4: C, 75.84; H,
6.56; N, 5.36. Found: C, 76.12; H, 6.86; N, 5.10
(E)-1,3-Dibutyl-5-(4-(2,6-diphenyl-4H-pyran-4-ylidene)but-2-en-1-ylidene)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (11): Purified by column chromatography
1
(CH2Cl2/hexane, 3:1). Dark solid (274 mg, 51 %). Mp: 258–260 °C. H NMR (400 MHz,
CDCl3): δ = 0.93-0.97 (m, 6H), 1.35-1.42 (m, 4H), 1.65-1.74 (m, 4H), 4.42-4.46 (m, 4H), 6.11
(d, 1H, J = 12.0 Hz), 6.73 (d, 1H, J = 1.6 Hz), 7.15 (d, 1H, J = 1.6 Hz), 7.49-7.55 (m, 6H),
7.72 (dd, 1H, J1 =13.0 Hz, J2 =12.0 Hz), 7.81-7.87 (m, 4H), 7.94 (dd, 1H, J1 =13.0 Hz, J2 =
12.0 Hz), 8.01 (d, 1H, J = 13.0 Hz) ppm. 13C NMR (125 MHz, CDCl3):
δ = 14.1 (CH3), 20.4
(CH2), 20.5 (CH2), 29.3 (CH2), 29.4 (CH2), 47.8 (CH2), 48.2 (CH2), 103.9 (CH), 108.3 (C),
110.1 (CH), 116.7 (CH), 125.5 (CH), 125.6 (CH), 129.8 (CH), 126.2 (CH), 129.3 (CH), 129.4
(CH), 131.4 (CH), 131.5 (CH), 131.6 (C), 145.7 (C), 153.2(CH), 157.5 (C), 157.6 (CH), 157.7
(C), 160.7 (C), 161.8 (C) ppm. IR (ATR):
ν = 1692 (C=O), 1532 (C=C), 1468 (C-O), 1363,
1281 (C=S), 1144, 934, 763 (=C-H), 681 (=C-H) cm-1. HRMS (DHB) m/z calculated for
C33H35N2O3S [M+H]+ 539.2362, found 539.2366. Anal. Calcd for C33H34N2O3S: C, 73.58; H,
6.36; N 5.20; S, 5.95. Found: C, 73.75; H, 6.46; N, 5.57; S, 6.13.
(E)-5-(4-(2,6-Diphenyl-4H-pyran-4-ylidene)but-2-en-1-ylidene)-2,2-dimethyl-1,3-
dioxane-4,6-dione (12): Purified by column chromatography (ethyl acetate/hexane, 1:1).
Dark solid (230 mg, 54 %). Mp: 238–241 °C. 1H NMR (400 MHz, CDCl3):
δ = 1.71 (s, 6H),
6.07 (d, 1H, J = 13.0 Hz), 6.68 (d, 1H, J = 1.8 Hz), 7.09 (d, 1H, J = 1.8 Hz), 7.49-7.53 (m,
18

ACCEPTED MANUSCRIPT
13
6H), 7.63-7.66 (m, 2H), 7.79-7.86 (m, 4H), 8.06 (d, 1H, J = 12.0 Hz) ppm. C NMR (100
MHz, CDCl3): = 27.9 (CH3), 103.0 (C), 103.5 (CH), 104.0 (C), 109.8 (CH), 115.7 (CH),
δ
124.2 (CH), 125.5 (CH), 125.6 (CH), 129.2 (CH), 129.3 (CH), 131.1 (CH), 131.2 (CH), 131.7
(C), 131.9 (C), 144.5 (C), 151.9 (CH), 157.0 (C), 157.1 (C), 157.7 (CH), 162.3 (C), 162.4 (C)
ppm. IR (ATR):
ν = 1648 (C=O), 1471 (C=C), 1381 (C-O), 1171, 1120, 937, 916, 781, 763
(=C-H), 677 (=C-H) cm-1. HRMS (DHB) m/z calculated for C27H22O5 M+ 426.1462, found
426.1467. Anal. Calcd for C27H22O5: C, 76.04; H, 5.20. Found: C, 75.82; H, 5.21.
2-[2-(4,6-Diphenyl-pyran-2-ylidene)-ethylidene]-indan-1,3-dione
(13):
The
title
compound, as a mixture of two (E/Z) isomers with 1:2 ratio (based on integration of ethylenic
protons) was obtained following the general procedure and was purified by column
1
chromatography (CH2Cl2/petroleum ether, 2:1). Dark solid (99 mg, 25 %). Mp > 260°C. H
NMR (major isomer, 300 MHz, CDCl3):
δ = 6.97 (d, 1H, J = 0.6 Hz), 6.99 (d, 1H, J = 0.6
Hz), 7.35 (d, 1H, J = 13.5 Hz), 7.55-7.60 (m, 6H), 7.67-7.71 (m, 4H), 7.85-7.87 (m, 2H),
7.95-7.98 (m, 2H), 8.26 (d, 1H, J = 13.5 Hz) ppm. 13C NMR (major isomer, 75 MHz, CDCl3):
δ
= 102.8 (CH), 104.0 (CH), 117.2 (CH), 119.5 (C), 121.6 (CH), 122.0 (CH), 125.7 (CH),
126.3 (CH), 129.2 (CH), 129.4 (CH), 130.9 (CH), 131.1 (C), 131.4 (CH), 135.5 (C), 137.6
(CH), 140.6 (CH), 142.0 (C), 147.7 (C), 159.7 (C), 166.4 (C), 191.4 (CH), 192.1 (C) ppm. IR
(KBr):
ν
= 1653 (C=O), 1558 (C=C), 1505 (C-O), 1470, 1439, 1330, 1201, 1152 cm-1. HRMS
(ESI/ASAP) m/z calculated for C28H18O3Na [M+Na]+ 425.1154, found 425.1154.
5-[2-(4,6-Diphenyl-pyran-2-ylidene)-ethylidene]-cyclopenta[c]thiophene-4,6-dione (14):
The title compound, as a mixture of two (E/Z) isomers with 1:2 ratio (based on integration of
ethylenic protons), was obtained following the general procedure and was purified by column
chromatography (CH2Cl2/petroleum ether, 2:1). Dark solid (121 mg, 30 %). Mp > 260 °C. 1H
NMR (major isomer, 300 MHz, CDCl3):
δ = 6.94 (d, 1H, J = 0.6 Hz), 6.99 (d, 1H, J = 0.6
Hz), 7.32 (d, 1H, J = 13.5 Hz), 7.50-7.54 (m, 6H), 7.64-7.68 (m, 2H), 7.70-7.73 (m, 2H),
19

ACCEPTED MANUSCRIPT
7.90-7.93 (m, 2H), 8.18 (d, 1H, J = 13.5 Hz) ppm. 13C NMR (major isomer, 75 MHz, CDCl3):
δ
= 103.0 (CH), 104.3 (CH), 117.2 (CH), 125.8 (C), 126.4 (CH), 126.6 (CH), 127.5 (C), 129.3
(CH), 129.4 (CH), 131.0 (CH), 131.5 (CH), 135.3 (C), 139.0 (CH), 146.5 (C), 147.5 (C),
148.4 (C), 160.0 (C), 166.7 (C), 170.0 (C), 184.5 (C), 185.4 (C) ppm. IR (KBr): = 1633
ν
(C=O), 1567 (C=C), 1427 (C-O), 1358, 1200, 757 (=C-H), 683 (=C-H) cm-1. HRMS
(ESI/ASAP) m/z calculated for C26H16O4NaS [M+Na]+ 431.0712, found 431.0714.
1,3-Dibutyl-5-[2-(4,6-diphenyl-pyran-2-ylidene)-ethylidene]-pyrimidine-2,4,6-trione (15):
The title compound, as a mixture of two (E/Z) isomers with 1:3 ratio (based on integration of
ethylenic protons), was obtained following the general procedure and was purified by column
chromatography (CH2Cl2/petroleum ether, 2:1). Dark solid (121 mg, 30 %). Mp > 260 °C. 1H
NMR (major isomer, 300 MHz, CDCl3):
δ = 0.88-0.92 (m, 6H), 1.29-1.36 (m, 4H), 1.55-1.59
(m, 4H), 3.84-3.91 (m, 4H), 6.86 (d, 1H, J = 0.6 Hz), 6.97 (d, 1H, J = 0.6 Hz), 7.42-7.50 (m,
13
7H), 7.55-7.58 (m, 2H), 7.81-7.86 (m, 2H), 8.72 (d, 1H, J = 13.5 Hz) ppm. C NMR (major
isomer, 75 MHz, CDCl3):
δ = 13.8 (CH3), 203 (CH2), 30.4 (CH2), 40.9 (CH2) 41.6 (CH2)
104.3 (CH), 104.5 (C), 104.6 (CH), 117.0 (CH), 125.8 (CH), 126.4 (CH), 129.4 (C), 129.5
(CH), 130.8 (C), 131.2 (CH), 131.7 (CH), 135.1 (C), 147.5 (CH), 149.5 (C), 151.6 (C), 160.5
(C), 163.0 (C), 167.8 (C) ppm. IR (KBr):
ν = 2955 (C-H), 1706 (C=O), 1644 (C=C), 1469 (C-
O), 1388, 1227, 1197, 758 (=C-H), 683 (=C-H) cm-1. HRMS (ESI/ASAP) m/z calculated for
C31H32N2O4Na [M+Na]+ 519.2254, found 519.2256.
4H-Cyclopenta[c]thiophene-4,6(5H)-dione (ThDione, 21): Thiophene-3,4-dicarboxylic acid
anhydride (0.2 g, 1.3 mmol) was dissolved in acetic anhydride (1 mL). Triethylamine (1 mL)
and ethylacetoacetate (0.17 mL, 1.31 mmol) were added and the reaction was stirred at 65 °C
overnight. The reaction mixture was poured over ice with HCl, the oily product was extracted,
dried (Na2SO4), and the solvent was evaporated in vacuo. The resulting carboxylic acid was
treated with conc. HCl at reflux for 10 minutes, cooled to room temperature, and extracted
20

ACCEPTED MANUSCRIPT
with CH2Cl2 (3 x 50 mL). The combined organic extracts were dried (Na2SO4) and the solvent
was evaporated in vacuo. The crude product was suspended in a minimum amount of diethyl
ether, stirred at room temperature for 1 hour and 21 was filtered off. Yellowish solid (0.14 g,
1
71 %). Mp: 122 °C (dec.). H NMR (400 MHz, CDCl3): δ (ppm): 3.54 (s, 2H), 7.99 (s, 2H).
13C NMR (100 MHz, CDCl3): 53.6 (CH2), 125.8 (CH), 148.7 (C), 189.7 (CO). EI-MS (70 eV)
m/z (rel. int.): 152 (M+˙, 100), 110 (75), 96 (50), 82 (50).
Acknowledgement
This work has received funding from the European Research Council (ERC) under the
European Union’s Horizon 2020 research and innovation program (grant agreement No
[638857]).
21

ACCEPTED MANUSCRIPT
Scheme 1 : Synthesis of γ-pyranylidene push-pull derivatives 1–7.
Scheme 2 : Synthesis of γ-pyranylidene push-pull derivatives 8–12 with extended
π-conjugated core.
Scheme 3 : Synthesis of α-pyranylidene push-pull derivatives 13–15.
Scheme 4 : Synthesis of ThDione 21.
Figure 1: picture of solutions of 1, 4-12 ( from left to right) in DCM (c ~ 10-3M).
Figure 2: UV/Vis spectra of compounds a) 1 - 3 b) 1 and 4–7 c) 1, 4, 8, and 9 d) 1, 5, 13, and
15 in dichloromethane (c ~ 10-5 M).
Figure 3. Localization of frontier molecular orbitals in representative chromophores 4, 8, and
(Z)-15.
Table 1: Electrochemical and optical data of chromophores 1–15.
Table 2: DFT calculated properties and optical nonlinearities of chromophores 1–15.
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Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N.
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Gaussian, Inc., Wallingford CT, 2013.
21
ArgusLab 4.0, Mark A. Thompson, Planaria Software LLC, Seattle, WA.
http://www.arguslab.com
26

ACCEPTED MANUSCRIPT
ox1
E1/2red1 (∆E) ∆E
Ep
EHOMO ELUMO
λmax
ε
Comp.
[V]a
0.50
[eV]c
–5.30
[eV]c
–3.39
[nm]d
[L.mmol.cm-1]d
[V]a [V]b
–1.41 (80) 1.91
–1.29 (80) 1.74
–1.24 (80) 1.70
–1.34 (90) 1.85
–1.43 (87) 2.09
–1.31 (80) 2.02
–1.41 (90) 2.18
–1.30 (83) 1.49
–1.22 (88) 1.41
–1.30 (80) 1.58
–1.18 (92) 1.47
–1.30 (96) 1.64
–1.29 (80) 1.68
–1.27 (81) 1.66
–1.33 (80) 1.91
528/565
49.3/51.3
52.2/46.5
65.0/54.8
78.1/89.4
70.7/71.2
59.1/86.5
56.6/57.1
64.5/44.2
44.6/33.5
68.0/48.9
84.9/92.5
85.7/65.1
35.7/34.2
34.2/19.9
33.3/32.2
1
2
0.45
0.46
0.51
0.66
0.71
0.77
0.19
0.19
0.28
0.29
0.34
0.39
0.39
0.58
–5.25
–5.26
–5.31
–5.46
–5.51
–5.57
–4.99
–4.99
–5.08
–5.09
–5.14
–5.19
–5.19
–5.38
–3.51
–3.56
–3.46
–3.37
–3.49
–3.39
–3.50
–3.58
–3.50
–3.62
–3.50
–3.51
–3.53
–3.47
556/596
563/586(sh)
538/575
3
4
514/550
5
537/575
6
498/531
7
599/654(sh)
613/666
8
9
589/639
10
11
12
13
14
15
620/673
576/623
574/612(sh)
619/656(sh)
561/596
a All potentials are given versus ferrocene. b ∆E = Epox1 – E1/2red1. For the oxidation, Ep stand
c
d
for E1/2 EHOMO = – (Eox1 + 4.8), ELUMO = – (Ered1 + 4.8) All spectra were recorded in
CH2Cl2 solutions at room temperature at c = 1.0 to 2.0 x 10-5 M.

ACCEPTED MANUSCRIPT
∆EDFT
β
(-2ω;ω,ω)
β
(-2ω;ω,ω)
µβ
EHOMO
ELUMO
µ
Comp.
1
[eV]a
[eV]a
[eV]b
[D]c
[10-30 esu]d
34.50
[10-30 esu]e
14.00
[10-48 esu]f
170
–5.72
–5.66
–5.65
–5.73
–5.79
–5.83
–5.89
–5.45
–5.46
–5.51
–5.55
–5.57
–5.63
–5.61
–5.64
–5.63
–5.70
–5.68
–2.93
–3.03
–3.09
–3.00
–2.90
–3.05
–2.92
–3.02
–3.08
–2.99
–3.13
–3.00
–2.89
–2.99
–2.94
–3.04
–2.87
–2.97
2.79
2.63
2.56
2.73
2.89
2.78
2.97
2.43
2.38
2.52
2.42
2.57
2.74
2.62
2.70
2.59
2.83
2.71
8.58
7.60
57.40
78.10
56.10
19.50
60.40
10.80
181.00
233.00
55.80
39.10
51.00
43.20
39.30
65.90
61.90
9.84
32.60
42.70
27.50
17.80
59.90
6.81
250
230
430
50
2
7.11
3
9.31
4
11.64
14.43
10.69
11.31
12.16
14.52
17.73
13.69
9.62
5
-70
6
130
1050
1200
1300
1500
900
7
76.10
103.00
16.90
46.40
20.50
13.00
8.94
8
9
10
11
12
13E
13Z
14E
14Z
15E
15Z
180
230
70
9.58
10.37
10.32
12.61
12.58
25.90
22.30
16.70
21.30
15.40
b
a DFT calculated energies of the HOMO/LUMO in CH2Cl2 (PCM). EHOMO – ELUMO. c DFT
calculated ground state dipole moment in CH2Cl2. d Calculated second-order polarizability in
CHCl3 at 1907 nm. e Calculated second-order polarizability in vacuum at 1907 nm. f µ
β
(2ω)
at 1907 nm in CHCl3. Molecular concentrations used for the measurements were in the range
10-3 to 10-2 M. µ
± 10 %.
β