Synthesis, optical and electrochemical properties of substituted 2-cinnamoyl-1, 3-indandione O-methyl ethers

Article abstract of DOI:10.1016/j.molstruc.2016.02.090

Seven new 2-cinnamoyl-1,3-indandione (2CID) O-methyl ethers with different substituents (R = -H, -CH₃, -OCH₃, -N(C₆H₅)₂, -N(CH₂CH₂CN)₂, julolidyl, -N(CH₃)₂) in 4-position of the cinnamoyl moiety were synthesized. The methylation with dimethylsulfate occurred at the oxygen atom of the exocyclic enol group with high selectivity. The synthesized compounds were characterized by ¹H, ¹³C NMR, IR, UV-Vis and luminescence spectroscopy, their electrochemical properties were investigated by cyclic voltammetry. The obtained results indicates that introducing an electron donating substituents in the 4-position of cinnamoyl moiety facilitates electrochemical oxidation, remarkably shifts absorption and emission bands to longer wavelengths, simultaneously increases extinction coefficient (ε). O-methyl ethers with strong electron donating groups (R = -N(C₆H₅)₂, -N(CH₂CH₂CN)₂, julolidyl, -N(CH₃)₂) in molecule are characterized by luminescence with maximum in range from 547 to 647 nm and absolute photoluminescence quantum yields from 0.02 to 0.32. Quantum yield (QY) of chromophore containing julolidyl fragment is solvent dependent. It was 0.32 in chloroform and decreased in other polar (ethanol, acetone) solvents.

Full text of DOI:10.1016/j.molstruc.2016.02.090

Accepted Manuscript
Synthesis, optical and electrochemical properties of substituted 2-cinnamoyl-1,3-
indandione O-methyl ethers
Ilze Malina, Valdis Kampars, Baiba Turovska
PII:
S0022-2860(16)30184-3
10.1016/j.molstruc.2016.02.090
MOLSTR 22299
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 23 August 2015
Revised Date: 9 December 2015
Accepted Date: 24 February 2016
Please cite this article as: I. Malina, V. Kampars, B. Turovska, Synthesis, optical and electrochemical
properties of substituted 2-cinnamoyl-1,3-indandione O-methyl ethers, Journal of Molecular Structure
(2016), doi: 10.1016/j.molstruc.2016.02.090.
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ACCEPTED MANUSCRIPT
SYNTHESIS, OPTICAL AND ELECTROCHEMICAL PROPERTIES
OF SUBSTITUTED 2-CINNAMOYL-1,3-INDANDIONE O-METHYL
ETHERS
Ilze Malinaa,*, Valdis Kamparsa, Baiba Turovskab
a
Riga Technical University, Institute of Applied Chemistry, P. Valdena 3/7, Riga, LV-1048, Latvia
bLatvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV-1006, Latvia
Abstract
Seven new 2-cinnamoyl-1,3-indandione (2CID) O-methyl ethers with different
substituents (R= -H, -CH3, -OCH3, -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2)
in 4-position of the cinnamoyl moiety were synthesized. The methylation with
dimethylsulfate occurred at the oxygen atom of the exocyclic enol group with high
selectivity.
The synthesized compounds were characterized by 1H-, 13C-NMR, IR, UV-Vis
and luminescence spectroscopy, their electrochemical properties were investigated by
cyclic voltammetry. The obtained results indicates that introducing an electron
donating substituents in the 4-position of cinnamoyl moiety facilitates electrochemical
oxidation, remarkably shifts absorption and emission bands to longer wavelengths,
simultaneously increases extinction coefficient (ε). O-methyl ethers with strong
electron donating groups (R= -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2) in
molecule are characterized by luminescence with maximum in range from 547 to 647
nm and absolute photoluminescence quantum yields from 0.02 to 0.32. Quantum yield
(QY) of chromophore containing julolidyl fragment is solvent dependent. It was 0.32
in chloroform and decreased in other polar (ethanol, acetone) solvents.
Keywords: O-methyl ethers; 2-cinnamoyl-1,3-indandione; methylation; optical
properties
1. Introduction
1,3-Indandione and its derivatives have been intensively studied over years
due to their wide range of potential applications. First studies were devoted to
investigate biological activity for derivatives of 1,3-indandione. Rat-extermination
[1], anti-inflammatory [2,3] and other properties were discovered for several 1,3-
indandione compounds. But in the last few decades 1,3-indandione moiety has been
used as structural element in synthesis of new chromophores and luminophores with
non-linear optical (NLO) properties [4-10]. 1,3-Indandione is well known as strong
electron acceptor moiety and, when it is bounded with electron donating substituents,
the molecules with potential applications as photoactive organic materials can be
obtained [5].
The
most
studied
derivative
of
1,3-indandione
is
4-N,N-
dimethylaminobenzylidene-1,3-indandione (DMABI) whose crystals and films are
characterized with efficient photoconductivity [11] and non-linear luminescence [7].
In recent years particular interest has been focused to 2-acyl- derivatives of
1,3-indandione. Due to the β,β’-triketone fragment, which has strong intramolecular

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hydrogen bond in the enol form, some compounds from this class are characterized
with high stability upon UV-irradiation [12], large Stokes shift [13] and complexation
ability with transition [14-16] and rare earth metal ions [17, 18]. As a result
compounds with excellent emission and thermal properties can be obtained, for
example, 2-benzoyl-1,3-indandione complex with europium(III) ion has been
proposed as potential molecular light converter material for new organic light
emitting diodes (OLED) [18]. Whereas 2-acetyl-1,3-indandione complexes with
transition metal ions such as silver(I) ion has shown proper thermal decomposition
temperature and it can be used as precursor for silver films [16]. Only few studies
have been devoted to 2-acyl derivatives of 1,3-indandione with prolonged π-conjugate
system in molecule – 2-cinnamoyl-1,3-indandiones (2CID). 2CID similar as 2-acyl-
1,3-indandiones exist in exocyclic enolic form, which is stabilized by intramolecular
hydrogen bond. If the benzene ring of cinnamoyl part contains strong electron
donating substituent in para- position, push-pull type molecules on the basis of 2CID
can be obtained with excellent electronic and optical properties. Ahmedova et al. [19-
22] have investigated optical and complexation properties of some 2CID and their
analogues. The authors characterized obtained compounds as chromophores with high
molar absorptivity, large Stokes shift, good photostability upon UV-irradiance,
however due to low solubility in organic solvents transition metal ion complexes with
2CID ligands does not have practical application.
Due to relatively low number of the studies devoted to 2CID and their
analogues, our work was directed towards investigation of new chromophores derived
from 2CID – their O-methyl ethers. In some papers also O-methylation of β,β’-
triketone fragment containing compounds were discussed [23-25], although the
properties of O-methyl ethers up till now have not been reported. We are presenting
here the synthesis of new chromophores, which contains 1,3-indandione moiety as
electron acceptor and with different electron donating substituents derived methylated
cinnamoyl fragment. These easily obtainable organic chromophores - 2CID O-methyl
ethers consisting of π-conjugated system between electron donor and acceptor could
possess pronounced emission characteristics and therefore could find an application in
optoelectronic devices, for example in OLED. Newly synthesized 2CID O-methyl
1
ethers are characterized by H-, 13C-NMR, FT-IR, UV-Vis and luminescence
spectroscopy methods and electrochemical measurement. Furthermore, to investigate
the structure modifying effects on the electrochemical and optical properties, 2-
cinnamoyl-1,3-indandione O-methyl ether with –N(CH3)2 substituent is compared
with
the
well
investigated
“push-pull”
chromophore
4-N,N-
dimethylaminobenzylidene-1,3-indandione (DMABI).
2. Experimental Procedures
2.1. General
The FT-IR spectra in the range from 4000 to 650 cm-1 were recorded on a
Perkin-Elmer Spectrum 100 FT-IR spectrometer using KBr pellets.
The 1H- and 13C-NMR spectra were recorded in CDCl3 or DMSO-d6 solutions
on a Brucker Avance 300 MHz spectrometer at 300 MHz for 1H- and 75 MHz for 13C-
nuclei. Chemical shifts were expressed in parts per million (ppm) relative to solvent
signal.
Diffraction data were collected on a Bruker-Nonius Kappa CCD
diffractometer using graphite monochromated Mo-Kα radiation (λ=0.71073 Ǻ). The
crystal structure was solved by direct methods [26, 27] and refined by full-matrix least

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squares [28]. The crystal data, details of data collection and refinement are given in
Table 1.
The purity of prepared organic compounds was established on Waters 2695
HPLC using Waters 2996 Photodiode array UV-Vis detector. The chromatographic
analyses were performed using XTerra MS C18 (5µm 2.1×100 mm) column, 50%
Acetonitrile/0,1% formic acid solution as mobile phase and flow rate 0.2 ml/min. MS
spectra were acquired on a Waters EMD 1000MS mass detector. Mass spectra were
obtained in ESI+ mode, voltage 30 V.
The UV-Vis absorption spectra in CHCl3 solutions were acquired using
Perkin-Elmer 35 UV/Vis spectrometer with a 1 cm path length quartz cell.
Emission spectra in CHCl3 solutions were measured on Quanta Master 40
steady state spectrofluorometer (Photon Technology International, Inc.) using 1 cm
path length quartz cuvettes. Absolute photoluminescence quantum yields in CHCl3
solutions were determined using QuantaMaster 40 steady state spectrofluorometer
(Photon Technology International, Inc.) equipped with 6 inch integrating sphere by
LabSphere.
The cyclic voltammograms were recorded using
a
computer
controlled electrochemical system PARSAT 2273. The measurements were carried
out using a three-electrode cell configuration. Stationary glassy carbon disk (Ø 0.5
cm) was used as a working electrode, Pt wire - as an auxiliary electrode. Potentials
were measured vs saturated calomel electrode (SCE) and recalculated vs normal
hydrogen electrode (NHE). The potential scan rate was 100 mV/sec. Electrochemical
redox reactions were studied in 0,1 M tetrabutyl-ammonium tetrafluorophosphate
(TBAPF6) acetonitrile solution under Ar atmosphere. Acetonitrile (Merck, puriss.
grade) was distilled over phosphorus pentoxide, stored over calcium hydride and
distilled just before use.
Melting points were determined using Stuart SMP101 apparatus and are
uncorrected. TLC analyses were performed on MERCK silica gel plates and were
detected with EURO-BST-203LS UV detector.
All solvents were purchased from Acros Organics with purity of ≥99%.
Dimethylsulphate was purchased from Sigma-Aldrich with purity of ≥99%. Acetone
was dried and distilled over K2CO3. Piperidine was purified by distillation before use.
2-Acetyl-1,3-indandione was synthesized as described in the literature [17] and 4-
N,N-dimethylaminobenzylidene-1,3-indandione as in the study [29]. The synthetic
route of compounds 3a-g and 4a-g are shown in Scheme 1.
Scheme 1
2.2. Synthesis of compounds 3a-g
2-Acetyl-1,3-indandione 1 (0,010 mol), derivative of benzaldehyde 2a-g
(0,010 mol) and piperidine (0,005 mol) was refluxed at 110 °C for 2 hours. Then
reaction mixture was cooled to 80 °C and 8 ml of ethanol was added. Solution was
boiled for 30 minutes, and after cooling, the formed crystals were filtered off and
washed with ethanol. Products were recrystallized from CH2Cl2 and EtOH mixture.
(E)-2-(1-hydroxy-3-phenylallylidene)-2H-indene-1,3-dione
M.P.=186-187 °C. H-NMR (CDCl3), δ, [ppm]: 13.20 (s, 1H), 8.04 (d, J=15.0 Hz,
1H), 7.92 (d, J=15.0 Hz, 1H), 7.89 (m, 2H), 7.74 (m, 4H), 7.46 (m, 3H). C-NMR
(3a),
Yield
32%,
1
13
(CDCl3), δ, [ppm]: 197.59, 188.60, 173.25, 145.04, 138.65, 134.25, 134.25, 134.00,

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133.50, 131.00, 129.03, 122.94, 122.50, 118.14, 108.02. IR, (KBr), ν, [cm-1]: 3400-
3200 (νOH), 3027 (νCH), 1704 (νC=O), 1620 (νC=O, C=C), 1579, 1564 (νC=C(Ph)). MS
(ES+) m/z: 277.00 (M+ requires 277.08), (ES-) m/z: 275.20 (M- requires 275.08).
(E)-2-(1-hydroxy-3-(p-tolyl)allylidene)-2H-indene-1,3-dione (3b), Yield 43%,
1
M.P.=184-185 °C. H-NMR (CDCl3), δ, [ppm]: 13.30 (s, 1H), 7.97 (d, J=13.5 Hz,
1H), 7.89 (m, 3H), 7.73 (m, 2H), 7.62 (d, J=6.0 Hz, 2H), 7.27 (d, J=6.0 Hz, 2H), 2.43
(s, 3H). 13C-NMR (CDCl3), δ, [ppm]: 197.81, 188.60, 173.68, 145.27, 142.25, 141.13,
138.64, 134.90, 134.70, 132.14, 129.90, 128.98, 122.50, 122.23, 116.79, 107.57. IR,
(KBr), ν, [cm-1]: 3200-3000 (νOH), 2962, 2917 (νCH), 1699 (νC=O), 1646, 1625 (νC=O
,
νC=C), 1583 (νC=C(Ph)). MS (ES+) m/z: 291.10 (M+ requires 291.09), (ES-) m/z: 289.30
(M- requires 289.09).
(E)-2-(1-hydroxy-3-(4-methoxyphenyl)allylidene)-2-H-indene-1,3-dione (3c), Yield
1
39%, M.P.=193-194 °C. H-NMR (CDCl3), δ, [ppm]: 13.30 (s, 1H), 7.93 (d, J=15.0
Hz, 1H), 7.88 (m, 3H), 7.82 (m, 2H), 7.69 (d, J=9.0 Hz, 2H), 6.98 (d, J=9.0 Hz, 2H),
13
3.90 (s, 3H). C-NMR (CDCl3), δ, [ppm]: 197.51, 188.80, 173.66, 162.30, 145.04,
140.82, 138.70, 134.74, 133.98, 131.03, 127.67, 122.64, 122.15, 115.33, 114.53,
107.17, 55.42. IR, (KBr), ν, [cm-1]: 3100-2600 (νOH), 3070, 2942, 2845 (νCH), 1698
(νC=O), 1624 (νC=O, C=C), 1565 (νC=C(Ph)), 1258, 1210 (νCOC). MS (ES+) m/z: 307.13
(M+ requires 307.09), (ES-) m/z: 305.28 (M- requires 305.09).
(E)-2-(3-(4-N,N-(diphenylamino)phenyl)-1-hydroxyallylidene)-2H-indene-1,3-dione
1
(3d), Yield 60%, M.P.=220-222 °C. H-NMR (CDCl3), δ, [ppm]: 13.25 (s, 1H), 7.90
(d, J=13.5 Hz, 1H), 7.82 (m, 3H), 7.70 (m, 2H), 7.55 (d, J=7.5 Hz, 2H), 7.33 (m, 4H),
13
7.17 (m, 6H), 7.04 (d, J=7.5 Hz, 2H). C-NMR (CDCl3), δ, [ppm]: 197.59, 188.83,
173.92, 151.01, 145.30, 145.00, 139.10, 138.85, 133.80, 133.50, 130.30, 129.61,
126.00, 124.58, 122.50, 122.06, 120.90, 114.73, 107.33. IR, (KBr), ν, [cm-1]: broad
3200-2800 (νOH), 3049, 3033 (νCH), 1696 (νC=O), 1632, 1617, 1548 (νC=O, νC=C,
νC=C(Ph)), 1504, 1489 (νC=C(Ph)). MS (ES+) m/z: 444.20 (M+ requires 444.15), (ES-)
m/z: 442.30 (M- requires 442.15).
(E)-2-(3-(4-N,N-(bis-(2-cyanoethyl))-amino)-phenyl)-1-hydroxy-allylidene)-2H-inde-
1
ne-1,3-dione (3e), Yield 32%, M.P.=219-220 °C. H-NMR (DMSO), δ, [ppm]: 13.30
(s, 1H), 7.91 (d, J=15.0 Hz, 1H), 7.85 (m, 3H), 7.72 (m, 2H), 7.70 (d, J=7.5 Hz, 2H),
6.73 (d, J=7.5 Hz, 2H), 3.93 (t, J=4.6 Hz, 4H), 2.74 (t, J=4.6 Hz, 4H).13C-NMR
(DMSO), δ, [ppm]: 197.23, 188.30, 173.08, 149.87, 146.17, 141.50, 141.00, 133.77,
133.63, 132.15, 124.30, 124.15, 123.51, 122.46, 119.78, 113.36, 106.64, 45.98, 15.75.
IR, (KBr), ν, [cm-1]: 3200-2600 (νOH), 3072, 3020, 2965 (νCH), 2935 (νCN), 1698
(νC=O), 1625 (νC=O, C=C), 1587, 1560, 1547 (νC=C(Ph)). MS (ES+) m/z: 398.13 (M+
requires 398.14), (ES-) m/z: 396.21 (M- requires 396.14).
(E)-2-(3-(1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)-1-hydroxyallylidene)-
2H-indene-1,3-dione (3f), Yield 50%, M.P.=225-226 °C. 1H-NMR (CDCl3), δ, [ppm]:

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13.25 (s, 1H), 7.84 (d, J=14.3 Hz, 1H), 7.79 (m, 2H), 7.69 (d, J=14.3 Hz, 1H), 7.66
(m, 2H), 7.20 (m, 2H), 3.31 (t, J=2.6 Hz, 4H), 2.78 (4H, t, J=2.6 Hz, 4H), 1.99 (t,
J=2.6 Hz, 4H). 13C-NMR (CDCl3), δ, [ppm]: 197.51, 189.00, 174.58, 147.30, 147.00,
140.80, 139.00, 133.93, 133.54, 129.70, 122.30, 122.20, 122.00, 121.95, 110.00,
106.30, 50.00, 27.10, 21.35. IR, (KBr), ν, [cm-1]: broad 3200-2600 (νOH), 3014, 2939,
2843 (νCH), 1693 (νC=O), 1627, 1567, 1543 (νC=O, νC=C, νC=C(Ph)), 1513, 1463 (νC=C(Ph)).
MS (ES+) m/z: 372.40 (M+ requires 372.43).
(E)-2-(3-(4-N,N-(dimethylamino)phenyl)-1-hydroxyallylidene)-2H-indene-1,3-dione
1
(3g), Yield 67%, M.P.=210-211 °C. H-NMR (CDCl3), δ, [ppm]: 13.30 (s, 1H), 7.93
(d, J=15.0 Hz, 1H), 7.82 (m, 2H), 7.80 (d, J=15.0 Hz, 1H), 7.70 (m, 2H), 7.65 (d,
13
J=7.5 Hz, 2H), 6.81 (d, J=7.5 Hz, 2H), 3.10 (s, 6H). C-NMR (CDCl3), δ, [ppm]:
197.31, 189.01, 174.35, 152.52, 146.30, 140.95, 138.76, 134.31, 133.51, 131.40,
122.67, 122.07, 111.83, 106.49, 40.23. IR, (KBr), ν, [cm-1]: broad 3200-2600 (νOH),
3019, 2904 (νCH), 1698 (νC=O), 1631, 1588, 1567 (νC=O, νC=C, νC=C(Ph)), 1523 (νC=C(Ph)).
MS (ES+) m/z: 320.20 (M+ requires 320.12), (ES-) m/z: 318.20 (M- requires 318.12).
2.3. Synthesis of compounds 4a-g
Under an argon atmosphere to a stirred solution of compounds 3a-g (0,001
mol) and K2CO3 (0,015 mol) in 25 ml anhydrous acetone was added dimethylsulphate
(0,015 mol) and the resulting mixture was heated at reflux for 4 hours. After cooling
at room temperature, K2CO3 was filtered off and washed with acetone. Filtrate was
cooled at 5 °C, and formed precipitate was filtered off. After drying the precipitate
was purified with column chromatography (mobile phase ethyl acetate: CH2Cl2 1:2).
(E)-2-(1-metoxy-3-phenylallylidene)-2H-indene-1,3-dione
M.P.=151-152 °C. H-NMR (CDCl3), δ, [ppm]: 8.18 (d, J=13.8 Hz, 1H), 7.90 (m,
2H), 7.76 (d, J=13.8 Hz, 1H), 7.71 (m, 4H), 7.44 (m, 3H). 4.35 (s, 3H). C-NMR
(4a),
Yield
49%,
1
13
(CDCl3), δ, [ppm]: 191.65, 188.84, 173.91, 145.02, 144.60, 140.45, 134.15, 132.00,
128.52, 122.31, 121.58, 112.39, 65.34. IR, (KBr), ν, [cm-1]: 3028, 2941, 2855 (νCH),
1705 (νC=O), 1664, 1614, 1593 (νC=O, νC=C, νC=C(Ph)), 1525, 1450 (νC=C(Ph)). MS (ES+)
m/z: 291.20 (M+ requires 290.31).
(E)-2-(1-methoxy-3-(p-tolyl)allylidene)-2H-indene-1,3-dione (4b), Yield 56%,
1
M.P.=139-140 °C. H-NMR (CDCl3), δ, [ppm]: 8.10 (d, J=13.8 Hz, 1H), 7.85 (m,
2H), 7.72 (m, 3H), 7.57 (d, J=5.0 Hz, 2H), 7.21 (d, J=5.0 Hz, 2H), 4.35 (s, 3H), 2.38
(s, 3H). 13C-NMR (CDCl3), δ, [ppm]: 192.40, 188.85, 174.19, 144.58, 141.49, 140.68,
134.68, 134.00, 133.14, 126.56, 122.23, 120.73, 112.40, 65.35, 21.63. IR, (KBr), ν,
[cm-1]: 3023, 2926, 2847 (νCH), 1715 (νC=O), 1670, 1612, 1598 (νC=O, νC=C, νC=C(Ph)),
1524 (νC=C(Ph)). MS (ES+) m/z: 305.30 (M+ requires 305.11).
(E)-2-(1-methoxy-3-(4-methoxyphenyl)allylidene)-2-H-indene-1,3-dione (4c), Yield
1
34%, M.P.=148-151 °C. H-NMR (CDCl3), δ, [ppm]: 8.05 (d, J=15.0 Hz, 1H), 7.87
(m, 2H), 7.78 (d, J=15.0 Hz, 1H), 7.73 (m, 2H), 7.67 (d, J=8.3 Hz, 2H), 6.97 (d, J=8.3

ACCEPTED MANUSCRIPT
13
Hz, 2H), 4.36 (s, 3H), 3.89 (s, 3H). C-NMR (CDCl3), δ, [ppm]: 192.31, 188.07,
175.00, 162.50, 141.10, 134.90, 134.50, 132.00, 128.00, 122.50, 119.00, 114.00,
112.00, 65.55, 55.55. IR, (KBr), ν, [cm-1]: 3029, 2965, 2838 (νCH), 1705 (νC=O),
1663, 1593(νC=O, νC=C, νC=C(Ph)), 1524, 1509 (νC=C(Ph)). MS (ES+) m/z: 321.40 (M+
requires 321.34).
(E)-2-(3-(4-N,N-(diphenylamino)phenyl)-1-methoxyallylidene)-2H-indene-1,3-dione
(4d), Yield 53%, M.P.=186-188 °C. 1H-NMR (CDCl3), δ, [ppm]: 8.00 (d, J=13.6 Hz,
1H), 7.86 (m, 2H), 7.73 (d, J=13.6 Hz, 1H), 7.70 (m, 2H), 7.54 (d, J=7.5 Hz, 2H),
7.32 (m, 4H), 7.15 (m, 6H), 7.03 (d, J=7.5 Hz, 2H), 4.34 (s, 3H). 13C-NMR (CDCl3),
δ, [ppm]: 193.00, 189.03, 174.66, 150.54, 147.89, 144.59, 134.29, 131.59, 130.00,
128.20, 125.51, 124.44, 122.27, 121.15, 119.09, 111.70, 65.13. IR, (KBr), ν, [cm-1]:
3027, 2970, 2847 (νCH), 1738 (νC=O), 1662, 1581 (νC=O, νC=C, νC=C(Ph)), 1521 (νC=C(Ph)).
MS (ES+) m/z: 458.30 (M+ requires 458.17).
(E)-2-(3-(4-N,N-(bis-(2-cyanoethyl))-amino)-phenyl)-1-metyoxyallylidene)-2H-indene
1
-1,3-dione (4e), Yield 54%, M.P.=159-160 °C. H-NMR (CDCl3), δ, [ppm]: 8.00 (d,
J=13.1 Hz, 1H), 7.85 (m, 2H), 7.72 (m, 3H), 7.76 (d, J=6.9 Hz, 2H), 6.70 (d, J=6.9
Hz, 2H), 4.34 (s, 3H), 3.90 (t, J=5.0 Hz, 4H), 2.72 (t, J=5.0 Hz, 4H). 13C-NMR
(CDCl3), δ, [ppm]: 192.03, 188.20, 174.67, 147.07, 144.34, 140.91, 134.21, 131.45,
125.98, 122.27, 118.00, 117.90, 112.44, 111.94, 65.36, 47.68, 15.75. IR, (KBr) ν,
[cm-1]: 3007, 2851 (νCH), 2949 (νCN), 1737 (νC=O), 1655, 1586 (νC=O, νC=C, νC=C(Ph)),
1516, 1465 (νC=C(Ph)) 1217 (νCOC). MS (ES+) m/z: 412.30 (M+ requires 412.16.)
(E)-2-(3-(1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)-1-methoxyallylidene)-
2H-indene-1,3-dione (4f), Yield 74%, M.P.=178-180 °C. 1H-NMR (CDCl3), δ, [ppm]:
7.85 (d, J=15.0 Hz, 1H), 7.82 (m, 2H), 7.73 (d, J=15.0 Hz, 1H), 7.66 (m, 2H), 7.18 (s,
2H), 4.28 (s, 3H), 3.30 (t, J=3.0 Hz, 4H), 2.76 (t, J=3.0 Hz, 4H), 1.97 (dt, J=3.0 Hz,
13
4H). C-NMR (CDCl3), δ, [ppm]: 197.22, 188.50, 175.52, 147.34, 146.31, 140.60,
133.72, 129.40, 122.27, 121.65, 121.13, 114.50, 110.27, 54.66, 50.10, 27.60, 21.37.
IR, (KBr), ν, [cm-1]: 2940, 2842, 2812 (νCH), 1702 (νC=O), 1660, 1578, (νC=O, νC=C,
νC=C(Ph)), 1501, 1434 (νC=C(Ph)), 1195 (νCOC). MS (ES+) m/z: 386.30 (M+ requires
386.16).
(E)-2-(3-(4-N,N-(dimethylamino)phenyl)-1-methoxyallylidene)-2H-indene-1,3-dione
(4g), Yield 34%, M.P.=133-134 °C. 1H-NMR (CDCl3), δ, [ppm]: 7.95 (d, J=14.1 Hz,
1H), 7.85 (m, 2H), 7.79 (d, J=14.1 Hz, 1H), 7.68 (m, 2H), 7.61 (d, J=7.1 Hz, 2H),
6.70 (d, J=7.1 Hz, 2H), 4.32 (s, 3H), 3.09 (s, 6H). 13C-NMR (CDCl3), δ, [ppm]:
192.09, 188.28, 175.40, 152.31, 146.29, 140.67, 133.71, 131.39, 123.37, 121.85,
116.15, 111.89, 111.06, 64.90, 40.24. IR, (KBr), ν, [cm-1]: 3072, 3024, 2959, 2869
(νCH), 1697 (νC=O), 1652, 1576 (νC=O, νC=C, νC=C(Ph)), 1531, 1499 (νC=C(Ph)) 1278
(νCOC). MS (ES+) m/z: 334.20 (M+ requires 333.14)

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3. Results and discussion
3.1. Synthesis and characterization of substituted 2-cinnamoyl-1,3-indandiones
Substituted 2-cinnamoyl-1,3-indandiones (2CID) 3a-g were obtained in
Claisen-Schmidt condensation reaction (Scheme 1) between 2-acetyl-1,3-indandione
1 and derivative of benzaldehyde 2a-g in the presence of piperidine. The chemical
1
structures of the compounds 3a-g were identified with H-, 13C-NMR and FT-IR
spectroscopy, compound 3f was also characterized by X-ray diffraction data.
1H-NMR spectra of compounds 3a-g are characterized with broad singlet near
13.20 ppm, which attributes to proton from enol hydroxyl group. Two doublets
appears at 8.00 and 7.90 ppm, which corresponds to protons from double bound of
allylidene fragment and their spin coupling constants are in the range from 13.5 to
15.0 Hz indicating that all substituted 2CID 3a-g exist in trans form. In the 13C-NMR
spectra of compounds 3a-g chemical shifts for 1,3-indandione cycle carbon atoms
C(9) and C(8) (see Scheme 1) are not equal, thus meaning that chemical environment
are not identical for these atoms. This could be explained with hydrogen bond
formation between hydroxyl group and one of the two carbonyl groups of the 1,3-
indandione moiety.
FT-IR spectra for compounds 3a-g shows broad band between 3200 and 3400
cm-1, which is assigned to enol hydroxyl group stretching vibrations. Non-bonded
hydroxyl group vibrations usually appears as a sharp absorption band near 3670-3580
cm-1, therefore such shift to lower region of inverse centimeters and band broadening
indicate that the intramolecular hydrogen bond exist in 2-cinnamoyl-1,3-indandione
molecules.
By slow evaporation of saturated dichloromethane solution good quality single
crystals of 2-cinnamoyl-1,3-indandione 3f were obtained for crystallographic analysis.
The crystal structure of compound 3f is shown in Fig 1. and selected geometrical
parameters are listed in Table 2.
Table 1
X-ray diffraction data confirms, that compound 3f in solid state exist in
exocyclic enol form, which is stabilized by intramolecular hydrogen bond between
carbonyl group oxygen atom (O11) from 1,3-indandione moiety and hydroxyl group
(H13-O13) from allylidene fragment. Hydrogen bond O13-H13 O11 is characterized
by bond length of 1.66(8) Ǻ (O11 H13) and 2.606(7) Ǻ (O11 O13), and angle of
160(6)° (O13-H13 O11). Interestingly, comparing bonds C2-C3 (1.432(7) Ǻ) and
C1-C2 (1.461(7) Ǻ), the latter ones are longer, showing less double bound character.
Moreover, bond C3-O11 (1.252(6) Ǻ) are significantly longer than bond C1-O10
(1.222(6) Ǻ), showing more single bond character. These data indicate that the
conjugated π-electron system stabilized by the intramolecular hydrogen bond is
present in the molecule of 3f. The angles between atoms O10-C1-C2 (128.7(5)°) are
wider than for O11-C3-C2 (125.3(5)°), confirming that hydrogen bond causes
carbonyl group (C3-O11) positioning closer to hydroxyl group and therefore
pseudoaromatic six-membered system is formed in molecule. Similar data were
obtained for other 2-acyl-1,3-indandiones, for examples, 2-acetyl-1,3-indandione [14,
30], 2-(3-thiophen-2-yl-1-hydroxy-allylidene)-2H-inden-1,3-dione [21], 2-(3-furan-2-
yl-1-hydroxy-allylidene)-2H-inden-1,3-dione [21], 2-(1-hydroxy-3-(p-tolyl)allylid-
ene)-2H-indene-1,3-dione [22].

ACCEPTED MANUSCRIPT
Fig. 1
Dihedral angle between 1,3-indandione moiety and julolidyl substituent plane
is 9.60°, meaning that molecule are almost planar. Interestingly, 2-acyl-1,3-
indandiones with 2-thiophene or 2-furan rings in the molecule are planar [21], but on
the contrary 2-(1-hydroxy-3-(p-tolyl)allylidene)-2H-indene-1,3-dione (compound 3b)
is not planar and has larger dihedral angle (11.34°) than 3f [22]. Planarity of the 1,3-
indandione moiety approves dihedral angle (0.96°) between cyclopentane and
benzene rings planes.
Compound 3f also exhibits weak intermolecular hydrogen bonds between
carbonyl group oxygen atom (O10) as proton acceptor and CH2 group (C25-H25)
from julolidyl substituent as proton donor. Contrary to the compound 3b [22]
cinnamoyl-1,3-indandione 3f does not show π-π stacking between aromatic rings.
Table 2
3.2. Synthesis and characterization of substituted 2-cinnamoyl-1,3-indandione O-
methyl ethers
Methylation of compounds 3a-g was carried out in acetone under argon
atmosphere with dimethlysulphate as alkylating agent in the presence of potassium
carbonate (Scheme 1).
Methylation of β,β’-triketones can lead to two different O-methyl ethers [25].
It is possible to add methyl group to carbonyl group of 1,3-indandione moiety or to
enol hydroxyl group of cinnamoyl fragment, and the result mainly depends from the
used alkylation agent. In the case of substituted 2-cinnamoyl-1,3-indandiones the
theoretically possible methylation products - O-methyl ethers A and B are shown in
Fig. 2. It was confirmed by 13C-NMR, that all O-methyl ethers 4a-g have a structure
A. In the case of structure B the symmetry of 1,3-indandione moiety would be
lowered, which would lead to different chemical shifts for carbon atoms C(9) and
C(8) near to methoxy group. However obtained compounds 4a-g showed identical
chemical shifts for these atoms in 13C-NMR spectra.
Fig. 2
1
The chemical structures of the compounds 4a-g were confirmed with H- and
13C-NMR spectroscopy, and FT-IR spectroscopy. 1H-NMR spectra of compounds 4a-
g shows minor changes from 3a-g spectra – a singlet for methoxy group protons
13
appears at 4.35 ppm and broad singlet for hydroxyl group proton disappears. C-
NMR spectra shows more differences. The comparison of 13C-NMR spectra chemical
shifts for 3a and O-methyl ether 4a are given in Table 3. Firstly chemical shifts of
carbon atoms C(8) and C(9) from 1,3-indandione moiety became identical, thus
indicating that chemical environment around these two atoms are identical. Secondly
chemical shifts for atom pairs C(4) and C(7), as well as C(5) and C(6) are identical,
which could be explained with more symmetrical structure for O-methyl ethers 4a-g
than for 2CID 3a-g. Compounds 3a-g have a strong hydrogen bond between hydroxyl
group and carbonyl group from 1,3-indandione moiety in the molecule, which could

ACCEPTED MANUSCRIPT
make molecule less symmetrical. Furthermore, in the IR spectra of compounds 4a-g a
broad band around 3200 cm-1, corresponding to hydroxyl group vibrations, was not
observed.
Table 3
3.3. Electrochemical properties
Redox properties of the synthesized chromophores 4a-g were investigated by
cyclic voltammetry. Both electrode processes - cathodic reduction as well as anodic
oxidation - are electrochemically irreversible (Fig. 3).
Fig. 3
In acetonitrile electrochemical reduction of the investigated compounds
proceeds in one step at potentials close to -1 V and are practically unaffected by the
substituent R (Table 4). On the contrary, electrochemical oxidation potential Eox
values are greatly affected by the substituents and are lowered with an increase of
their electron donating properties in the line -H, -CH3, -OCH3, -N(CH2CH2CN)2, -
N(C6H5)2, -N(CH3)2, julolidyl (Table 4). It can be concluded that the peak potentials
Eox and Ered represents the energies of the frontal molecular orbitals, which are
localized on the different parts of chromophore molecules - the oxidation process is
localized on the cinnamoyl part of the molecules, while 1,3-indandione moiety
undergoes electrochemical reduction.
Table 4
3.4. Optical properties
In order to explore the effect of different substituents in cinnamoyl moiety on
the optical properties of compounds 4a-g, absorption spectra were investigated in
1.5·10-5M chloroform solution. The absorption bands of the chromophores 4a-g are
presented in the Fig. 4 and the values of its maxima (λabs) and molar extinction
coefficients (ε) are summarized in Table 4.
As shown in Fig. 4, unsubstituted O-methyl ether 4a exhibit a broad
absorption band with ε value 22392 cm-1 M-1 and maximum at 389 nm, which could
be assigned to an intramolecular charge transfer (ICT) transitions from cinnamoyl
fragment to 1,3-indandione moiety. Introduction of the donor groups in the benzene
ring of cinnamoyl moiety shifts absorption bands to longer wavelength and increases
its molar absorptivity. Red shift of absorption band increases in the following
sequence - 4b, 4c, 4e, 4d, 4g, and 4f. Introducing weak electron donor groups
(methyl and methoxy) in the benzene ring (chromophores 4b and 4c) exhibits the
smallest red shift for 11 and 35 nm of absorption band maxima, but their molar
absorptivity increases two times compared to unsubstituted O-methyl ether 4a. Other
O-methyl ethers 4d-g contains electron rich dialkylamino, diphenylamino or
polycyclic amino - julolidine substituents, which possess larger electron donating
strength. Therefore large bathochromic shifts of 72-125 nm and higher ε values more

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than two times are observed for compounds 4d,e,g. Similar observations were
reported to analogues of substituted 2-cinnamoyl-1,3-indandiones [22]. Julolidyl
donor causes the largest bathochromic shift (173 nm), probably due to nitrogen atom
location in the donor group. In julolidyl fragment nitrogen is in fixed position, due to
polycyclic structure, which promotes the overlap between p-orbital of the amino
group and benzene ring. This structure facilitates nitrogen lone pair electron
conjugation with the π-electron system of molecule and increase the electron-donating
strength of substituent. Similar observation was reported in the study [31].
Fig. 4
The absorption wavelengths of chromophores 4a-g (the charge – transfer
transition energy) linearly depends on the difference between the electrochemical
oxidation and reduction peak potentials (Eox-Ered), which indicates that the absorption
is connected with charge transfer from cinnamoyl fragment to 1,3-indandione moiety
(Fig. 5).
Fig. 5
The emission properties of newly synthesized chromophores 4a-g were also
studied in 1.5 10-5 M chloroform solutions; emission bands maxima (λem), Stokes
shifts ( ∆λsts) and absolute photoluminescence quantum yields (QY) are depicted in
Table 4.
Unsubstituted and methyl and methoxy group substituted O-methyl ethers 4a-
c does not show emission properties, probably due to weak donating group presence
in molecule. The luminescence are observed only for compounds 4d-g, which have
both strong electron acceptor (1,3-indandione) and electron donor (-N(C6H5)2, -
N(CH2CH2CN)2, julolidyl, -N(CH3)2) groups in molecule. Red shift for emission
bands increases in the following sequence - 4e, 4g, 4d, and 4f, respectively. Emission
bands are wide with maximum in range from 547 to 647 nm (Fig. 6), but
photoluminescence quantum yields (QY) varies from 0.02 and 0.06 for 4g and 4d, to
0.32 for compound 4f. Interestingly, the replacement of the electron donor N(CH3)2 by
-N(CH2CH2CN)2 leads to decrease in QY value below 0.01. This fact could be
explained with cyano group location in the donor substituent in chromophore 4e
molecule. Cyano group act as an electron acceptor and therefore decrease the
donating strength of diethylamino group to 1,3-indandione. High quantum yield of 4f
in chloroform solution cause a great interest. We assumed, that high quantum yield of
O-methyl ether 4f could be explained with its rigid donor substituent, which prevents
amino group from rotation in excited state. Other luminescent O-methyl ethers 4d,e,g
have dialkyl or diphenyl amino groups as donors, which could easily twist in the
excited state and therefore lead to the fast non-radiative excited-state deactivation of
the whole molecule, likewise it was observed for structurally similar compound -
DMABI [32].
Fig. 6
However, it was observed, that emission properties for compound 4f were
solvent dependent. QY of 4f was relatively low in polar solvents, for example, in
1.5 10-5 M ethanol solution QY was only 0.01 and in 1.5 10-5 M acetone solution -

ACCEPTED MANUSCRIPT
0.03. To explore ethanol influence on the emission properties of 4f, several
chloroform-ethanol mixtures with different ethanol volume were prepared, and
solutions of 4f with concentration 1.5 10-5M were prepared and their QY were
determined. Obtained data are shown in Fig. 7. As it was expected ethanol has a
quenching effect on fluorescence of 4f. QY lowers for 0.1, when ethanol volume is
6% in mixed ethanol-chloroform solution and decreases for half (0.16), when ethanol
volume is 15%. Polar solvents probably increase non-radiative processes in the
excited state of compound 4f molecules. This could mean that several factors,
including structure geometry, interactions of ground and excited states with
environment could influence the O-methyl ether 4f emission properties. To explain
clearly O-methyl ether 4f emission properties further experimental and theoretical
investigations are needed.
Fig. 7
In conclusion for practical application only O-methyl ether 4f with julolidyl
substituent presents valuable red light emission with high QY and therefore should be
further investigated for use in the optolectronic materials.
Similarly to 2-cinnamoyl-1,3-indandione analogues with heterocyclic ring in
molecule [21] large Stokes shift (∆λsts) were observed for O-methyl ethers 4d-g, what
can be explained with intramolecular rearrangements in excited state for these
molecules.
Absorption and emission spectra of compounds 4a-g in non-polar
(cyclohexane, MTBE), polar aprotic (acetone, DMF) and protic (ethanol) solvents
were registered in room temperature, data of λabs and λem are depicted in Table 5. Since
the dipole moments of the ground and the excited states are different, the change of
solvent polarity leads to the different stabilization of these states and cause the
solvatochromic effect. For chromophores 4a-c solvents polarity has an insignificant
effect on absorption properties and red shift in DMF compared to cyclohexane by 5-
10 nm are observed. Other chromophores 4d-g shows larger bathochromic shift by
18-47 nm, thus meaning that these chromophores have more polar character than 4a-
c. Impact of solvents polarity on emission properties is similar to those for absorption
properties. By changing solvents from cyclohexane to DMF the compounds 4d-g
shows large red shift by 77-99 nm of λem in DMF compared to one in cyclohexane (or
MTBE for 4e).
Table 5
3.5. Comparison of the characteristics for substituted cinnamoyl-1,3-indandione O-
methyl ethers and benzylidene-1,3-indandiones
To gain clearer information about the difference in properties for benzylidene
and cinnamoyl derivatives of 1,3-indandione, the compound 4g with –N(CH3)2
substituent in cinnamoyl fragment was compared to well-known chromophore 4-N,N-
dimethylaminobenzylidene-1,3-indandione (DMABI). The properties of DMABI are
given in Table 6. Comparison of absorption properties between DMABI and 4g,
showed that latter one has a red shift of absorption band maximum for 32 nm, due to
more extended π-conjugate system in the molecule. Though the DMABI exhibit more
intensive absorption band, it is not so wide as absorption band of compound 4g (89

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nm). Furthermore, chromophore 4g relative strongly emits yellow light at 597 nm,
whereas DMABI has a weak luminescence with quantum yield <0.01.
Table 6
5. Conclusions
A series of new substituted 2-cinnamoyl-1,3-indandione O-methyl ethers were
synthesized in methylation reaction between substituted 2-cinnamoyl-1,3-indandiones
1
and dimethylsulphate. Obtained O-methyl ether structures were confirmed by H-,
13C-NMR, FT-IR spectroscopy.
Investigation of electrochemical properties by cyclic voltammetry shows that
all obtained compounds are “push-pull” chromophores with a location of highest
occupied molecular orbital on cinnamoyl and lowest vacant molecular orbital on 1,3-
indandione moieties. All 2-cinnamoyl-1,3-indandione O-methyl ethers exhibit strong
absorption in 350-600 nm range with high molar absorptivity (22000-57000 cm-1 M-
1). Linear dependence of absorption wavelength on difference between oxidation and
reduction peak potentials establishes that absorption is connected with charge transfer
from cinnamoyl fragment to 1,3-indandione moiety.
Luminescence for three newly synthesized compounds with no or weak
electron donor substituents (R= -H, -CH3, -OCH3) were not observed, but other O-
methyl ethers with strong electron donor substituents (R= -N(C6H5)2, -
N(CH2CH2CN)2, julolidyl, -N(CH3)2) in chloroform solutions shows emission with
maximum at 647, 547, 634, 597 nm and with absolute photoluminescence quantum
yields - 0.06, <0.01, 0.32, 0.02, respectively. High photoluminescence quantum yield
in the case of julolidyl derivative is influenced by several factors, including structure
geometry and interactions with environment in the ground and excited states. To
elucidate emission properties for the compound with julolidyl substituent, further
investigations are necessary.
Acknowledgments
This work was supported by the National research program of Latvia “Imis2”.
The authors thanks Dr.phys. S. Belyakov for his help with X-ray diffraction analysis.
Supplementary material
The deposition number CCDC 1439051 for compound 3f contains the
supplementary crystallographic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/data_request/cif or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK;
fax: +44 (0) 1223 336033; email:deposit@ccdc.cam.ac.uk.
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Schemes, Tables and Figures
Scheme 1. Reagents and conditions: (i) Piperidine, 110 oC, 2 hours; (ii) dimethylsulphate, K2CO3,
acetone, 56 oC, 4 hours.

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Table 1
Crystal data and refinement parameters for compound 3f.
Compound
3f
Molecular formula
C24H21NO3
Molecular weight
Crystal system
Space group
371.42
Monoclinic
P 21/n
a (Ǻ)
b (Ǻ)
8.5990 (4)
21.7570 (5)
10.5800 (14)
108.692 (3)
1875.0 (3)
4
c (Ǻ)
β (°)
V (Ǻ3)
Z
Dc (Mg m-3)
1.316
T (K)
293
µ (mm-1)
0.09
F(000)
2θmax (°)
784
54.2
h, k, l range
-10 to 10, -27 to 26, -12 to 13
11204
No. measured reflections
No. independent reflections (Rint)
4089 (0.139)
1399
257/0
No. observed reflections (I> 2σ(I))
No. refined parameters/restraints
0.0936, 0.2348
0.2702, 0.3341
0.902
R, wR [I > 2σ(I)]
R, wR [all data]
Goodness of Fit on F2, S
Max., Min electron density (e Ǻ-3)
0.23, -0.21
0.021
Maximum ꢀ/σ
Table 2
Selected geometry of compound 3f.
Bond distances
Bond angles
1.222 (6)
1.461 (7)
1.488 (7)
1.432 (7)
1.385 (7)
1.347 (7)
1.447 (7)
1.392 (7)
1.391 (7)
1.367 (7)
107.7 (4)
129.7 (5)
118.4 (5)
122.5 (5)
128.7 (5)
C1-O10
C1-C2
C1-C8
C2-C3
C14-C15
C15-C16
C16-C17
C16-C21
C1-C2-C3
C1-C2-C12
C2-C12-O13
C3-C2-C12
C2-C12
C3-O11
C3-C9
C17-C18
C18-C19
C19-C20
C20-C21
O10-C1-C2
O10-C1-C8
O11-C3-C2
O11-C3-C9
1.252 (6)
1.477 (7)
1.340 (6)
1.414 (7)
1.425 (7)
1.407 (7)
1.380 (7)
125.1 (5)
125.3 (5)
126.3 (5)
C12-O13
C12-C14
Hydrogen bond geometry
Symmetry code
D-H
D-H A
H A
D A
D-H A
0.98 (7)
0.96
O13-H13 O11
C25-H25 O10
1.66 (8)
2.49
2.606 (7) 160 (6)
3.422 (8) 162
intramolecular
−1/2+x, 1/2−y, 1/2+z

ACCEPTED MANUSCRIPT
Table 3
Comparison of 13C-NMR chemical shifts for 2-cinnamoyl-1,3-indandione 3a and O-methyl ether 4a.
δ, ppm
13C atom
3a
4a
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
=C-OH
188.61
108.02
197.59
122.50
133.50
134.25
122.94
138.65
134.25
173.25
188.84
112.39
191.65
132.00
134.15
134.15
132.00
145.02
145.02
-
-CH=CH-Ph 145.04
144.60
140.45
122.31
128.52
121.58
173.91
65.34
1-C-Ph
2,6-C-Ph
3,4,5-C-Ph
134.00
131.00
129.03
-CH=CH-Ph 118.14
=C-OCH3
-OCH3
-
-
Table 4
Absorption, emission and electrochemical properties of compounds 4a-g.
Compound
QY
Eox, V
Ered, V
∆λsts,
nm
-
λ
abs, nm
ε, cm-1 M-1
λem, nm
389
401
424
509
461
22392
41841
46904
50456
57520
-
-
-
-
1.80
1.69
1.46
0.97
1.02
-0.98
-1.00
-1.05
-0.97
-0.97
4a
4b
4c
4d
4e
-
-
-
-
647
547
0.06
<0.01
131
101
562
514
54367
44642
634
597
0.32
0.02
80
83
0.57
0.77
-1.14
-1.11
4f
4g

ACCEPTED MANUSCRIPT
Table 5
Absorption (λabs) and emission (λem) band maxima of compounds 4a-g in various solvents.
Cyclohexane MTBE Acetone Ethanol
λem, λabs λem, λabs λem, λabs λem,
nm
DMF
λabs,n
m
,
,
,
λabs
,
λem,
nm
Compound
nm
nm
nm
nm
nm
382
396
423
nm
nm
382
396
420
374
391
410
-
-
-
375
389
410
-
-
-
378
391
413
-
-
-
-
-
-
-
-
-
4a
4b
4c
478,
524,
555
484
455
529
597
526
610
488
474
551
649
593
651
506
483
573
645
608
655
496
488
564
654
611
662
4d
4e
4f
498sh
a
a
-
-
500sh, 558,
522
471,
600
487
576
505
619
524
628
518
634
4g
491sh
545
a-insoluble in cyclohexane
Sh – shoulder
Table 6
Absorption, emission and electrochemical properties of DMABI.
Characteristics
Eox, V
Ered, V
Eox– Ered, V
DMABI
1.00
-1.26
2.26
482
λabs, nm in chloroform
531
λem, nm in chloroform
49
∆λsts, nm
Photoluminescence quantum yield in chloroform
Solvatochromic shift of absorption band by
changing solvent from cyclohexane to DMF, nm
ε, cm-1 M-1
<0.01
27
68900
47
Half width of absorption band in chloroform, nm

ACCEPTED MANUSCRIPT
Fig. 1. ORTEP drawing of compound 3f with the atom numbering scheme. All non-hydrogen atoms are
drawn as 50% probability ellipsoids.
Fig. 2. Structures of possible methylation products of substituted 2-cinnamoyl-1,3-indandiones.
Fig. 3. Cyclic voltammogramms of chromophores 4a-c.

ACCEPTED MANUSCRIPT
Fig. 4. Absorption spectra of compounds 4a-g in 1,5 10-5M chloroform solutions.
Fig. 5. Correlation of the absorption band maxima with the difference of the electrochemical
oxidation and reduction peak potentials.

ACCEPTED MANUSCRIPT
Fig. 6. Emission spectrum of O-methyl ether 4f in 1.5 10-5M chloroform solution.
Fig. 7. Stern-Volmer-like plot of quenching of compound 4f by ethanol.

ACCEPTED MANUSCRIPT
Highlights:
1. Differently substituted 2-cinnamoyl-1,3-indandione O-methyl ethers were
synthesized.
2. Methylation occurred at the exocyclic enol group of cinnamoyl fragment.
3. Some obtained compounds have high molar absorptivity and intensive
luminescence.
4. Compound with julolidyl substituent showed relatively high quantum yield.