Photophysical properties of thiophenes and 2,2′-bithiophenes containing alicyclic moieties

Article abstract of DOI:10.1016/j.dyepig.2014.09.013

A series of novel 1-hydroxycycloalkyl- and cycloalkenylthiophenes (4a-4c, 4e, 6b, 6d, 6e) and bithiophenes (5a-5e, 7b-7e) were synthesized via Grignard reaction. The conditions control in the Grignard reaction allowed to obtain tertiary alcohols or cycloa

Full text of DOI:10.1016/j.dyepig.2014.09.013

Dyes and Pigments 113 (2015) 435e446
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Photophysical properties of thiophenes and 2,20-bithiophenes
containing alicyclic moieties
Violetta V. Meshkovaya*, Alexander V. Yudashkin, Yuri N. Klimochkin
Organic Chemistry Division, Samara State Technical University, Kuibyshev St. 153, 443010 Samara, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel 1-hydroxycycloalkyl- and cycloalkenylthiophenes (4ae4с, 4e, 6b, 6d, 6e) and bithio-
phenes (5ae5e, 7be7e) were synthesized via Grignard reaction. The conditions control in the Grignard
reaction allowed to obtain tertiary alcohols or cycloalkenes selectively. The VilsmeiereHaack formylation
of thiophenes and 2,20-bithiophenes with alicyclic fragment C4-C5 results formation of unsaturated
aldehydes whereas cycloalkenes C6 form 50-formylbithiophenes as the main isomers. The photophysical
properties such as absorption and fluorescence spectra were recorded in different solvents, and relative
quantum yields of aldehydes (9a, 9b, 11ce11e) and corresponding carbonitriles (13a, 13b, 15ce15e) were
measured. The synthesized compounds showed an intense fluorescence in the 400e520 nm range,
moderate quantum yields and large Stokes' shifts values.
Received 8 June 2014
Received in revised form
11 August 2014
Accepted 4 September 2014
Available online 16 September 2014
Keywords:
Organic fluorophores
Bithiophene
VilsmeiereHaack reaction
Photophysical properties
Cycloalkylthiophene
Quantum yield
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
optical materials [3e5,24e27] In addition pushepull bithiophenes
bearing N-acetylamino-fragment and variety electron withdrawing
Thiophenes and oligothiophenes are the subject of continuing
research due to their optical and chemical properties with potential
use in scientific and industrial fields. The intense development of
devices based on linear and non-linear optical properties of organic
compounds lead to keen interest to the structures bearing thio-
phene moieties [1e5]. Oligothiophenes are used in energy har-
vesting systems [6,7], as solar cells elements [8,9] and molecular
sensors [10]. The thiophene based materials are used in biomole-
cular diagnostics and bioimaging applications [11e14]. It is found
that thiophene unit is the most efficient for the increase optical
nonlinearity parameters due to the conjugation with different
groups are used as laser dyes with high efficiency coefficient [28].
Thiophenes and oligothiophenes are excellent building blocks to
be used in the donor-acceptor type structures for design of new
fluorophores with efficient photophysical properties for different
applications [29e31]. The electronic nature and the position of
substituent in the oligothiophene structure are the factors to pro-
duce photostable and efficient fluorophores [32]. The 2,20-bithio-
phenes are the most suitable structures for modeling of pushepull
flourophores due to the long-chain conjugation with substituents
in 5 and 50-positions. The presence of alkyl or cycloalkyl group in
the thiophene unit in the most cases leads to slight changes of
photophysical characteristics, but often improves other useful
properties of materials [21,33e35]. Non-symmetric long chained
quaterthiophenes and sexithiophenes bearing alkyl- or cycloalkyl-
chains form liquid crystals and used for fabrication of thin films in
electronic devices [21,36e41]. Moreover, the photochromism was
observed for mixed crystals of thiophene derivatives bearing
cyclohexyl and cyclohexenyl groups [42].
aromatic
p-systems [15e18]. The oligothiophenes have self-
organization properties and form patterned monolayers on
graphite therefore they might provide a basis for interfaces in
electronic devices [19e22]. Oligothiophenes containing donor-
acceptor groups are used as planarizable and polarizable fluores-
cent membrane probes for the detection of fluidity and membrane
potentials in biological research [23]. Pushepull oligothiophenes
have been investigated and exhibit enhanced photophysical prop-
erties, such as intense fluorescence, high quantum yields, large
Stokes' shifts, and polarizability thus they are useful as non-linear
To the best of our knowledge, there is lack of literature data
about synthesis and properties of thiophenes and 2,2'-bithio-
phenes, containing alicyclic moieties. This fact induced us to
combine these fragments in the one structure and study fluores-
cent properties of new molecules. Herein, we report the synthesis
of thiophenes and 2,20-bithiophenes with alicyclic fragments and
describe the results of VilsmeiereHaack reaction for these
* Corresponding author. Tel./fax: þ7 846 332 21 22.
E-mail addresses: orgchem@samgtu.ru, violetta.meshkovaya@yandex.ru
(V.V. Meshkovaya).
http://dx.doi.org/10.1016/j.dyepig.2014.09.013
0143-7208/© 2014 Elsevier Ltd. All rights reserved.

436
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
compounds. The photophysical properties of compounds have been
measured in different solvents to determine the dependence of
fluorescent parameters values and solvent characteristics.
h
i
hꢀ
ꢁ ꢀ
ꢁi
Df ¼ ð
3
ꢁ 1Þ ð2
=
3
þ 1Þ ꢁ n2 ꢁ 1
=
2n2 þ 1
The values of parameters
DG were calculated for n-hexane, THF,
pyridine, diethylene glycol, ethanol, acetonitrile. The p*-values for
2. Experimental section
solvents [51,52]: ꢁ0.081 for n-hexane, 0.540 for ethanol, 0.576 for
tetrahydrofuran, 0.713 for acetonitrile, 0.867 for pyridine, 0.932 for
diethylene glycol.
2.1. General information and materials
Experiments with air and moisture sensitive materials were
carried under argon atmosphere. Marchery-Nagel Silica 60
(0.063e0.2 mm) were used for preparative column chromatog-
raphy. Reagents were commercially available from Sigma Aldrich,
Merck and were used without further purification. FTIR spectra
were taken on a Shimadzu IRAffinity-1 spectrophotometer in KBr
pellets or thin-layer (KBr prisms). NMR spectra were recorded on a
JEOL JNM ECX 400 (400 MHz) spectrometer in DMSO-d6 and CDCl3
using tetramethylsilane (TMS) as an internal reference. Chemical
shifts and coupling constants were recorded in units of parts per
million (ppm) and Hertz (Hz), respectively. Melting points were
determined on an electrothermal melting point apparatus and are
uncorrected. Elemental analysis was performed on a EuroVector
EA-3000 instrument. Electron impact-mass spectrometry (EI-MS)
spectra were obtained on a Finnigan Trace DSQ spectrometer
(70 eV). Analytical thin-layer chromatography (TLC) was performed
on aluminum-backed silica-gel plates (Merck 60 F254 and
Marchery-Nagel XtraSilGel UV-254). Visualization of components
was accomplished with UV-light (365 nm) or exposure to I2.
2.4. General procedure for the preparation of compounds 4ae4c,
4e, 5a-5e, 6b, 6d, 6e, 7be7e
A solution of cycloalkanone 0.01 mol in 20 mL ether was added
very slowly to a stirred and ice-cooled 2-thienylmagnesium bro-
mide/2-thienylmagnesium iodide or 5-(2,20-bithiophene)magne-
sium bromide (was prepared from 0.1 mol of corresponding 2-
halogenthiophene or 5-halogen-2,20-bithiophene and 0.1 mol of
magnesium in 25 mL of ether). The mixture was refluxed for 1 h,
next, it was cooled in an ice-bath and 50 mL of a 10% aqueous so-
lution of ammonia chloride was added. The organic layer was
separated, washed with water, dried with sodium sulfate, and the
solvent was removed. The residue was fractionally distilled in the
thiophene series. The residue in the bithiophene series was worked
up with hexane, the solid was filtered off and dried. The title
product was purified by column chromatography on silica gel in
hexane as eluent.
2.4.1. 1-(2-Thienyl)cyclobutanol (4a)
Colorless crystals, 60%; mp 44-46ꢀС; IR (KBr), cmꢁ1: 3313, 2985,
2940, 1249, 1126, 833, 705; 1H NMR (DMSO-d6, 400 MHz)
d 7.32
2.2. Synthesis of starting compounds
(1H, dd, J ¼ 5.0 Hz, J ¼ 1.4 Hz, 5-H), 7.01 (1H, dd, J ¼ 3.7 Hz,
2,20-bithiophene was prepared by improved method [43], yield
70%; bp 102-108ꢀС/4 mmHg [43]. Synthesis of 5-bromo-2,20-
bithiophene and 5-iodo-2,2’-bithiophene carried out by the
described methods [44,45].
J ¼ 1.4 Hz, 3-H), 6.91 (1H, dd, J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4-H), 2.25e2.34
(4H, m, CH), 1.75e1.88 (1H, m, CH), 1.48e1.72 (1H, m, CH) ppm; 13
C
NMR (DMSO-d6, 100 MHz)
d 154.1, 127.0, 124.6, 122.2, 74.0, 39.8,
13.00 ppm; [Found: C, 62.35; H, 6.58; S, 20.85. C8H10OS requires C,
62.30; H, 6.54; S, 20.79%].
2.3. Electronic absorption and emission spectroscopy
2.4.2. 1-(2-Thienyl)cyclopentanol (4b)
Light yellow oil, 29%; bp 98-103ꢀС/2-4 mmHg; IR (KBr), cmꢁ1
:
UV/Vis absorption spectra were recorded on a Shimadzu UV
mini-1240 spectrophotometer at 24 ꢀC in a 1 cm path-length quartz
cell, in comparison to solvent blank, at the wavelength range
200e550 nm. Emission spectra were obtained on a Cary Eclipse
Varian Fluorescence Spectrophotometer in a 1 cm path-length
quartz cell at the wavelength range 200e650 nm, excitation and
emission slits are 2.5 nm. The excitation wavelength was at the
maxima of absorption spectra. The emission spectra were recorded
at right angle relatively cell. Experiments were conducted in n-
hexane, EtOH, MeCN, THF, pyridine, diethylene glycol (water con-
tent < 1% v/v) prepared according to described methods [46]. The
atmospheric oxygen contained in solutions was not removed. The
absorption and fluorescence spectra of compounds were measured
on a range of known concentrations (C ¼ 10ꢁ6e10ꢁ5 M). The rela-
tive fluorescence quantum yields (Qf (rel)) were determined using
the quinine sulfate (1 ꢂ 10ꢁ5 M) in 0.1 M H2SO4 as the standard
(Qf ¼ 0.546 [47]). The formula for calculation of Qf is.
3400, 2955, 2958, 1438, 1238, 999, 840, 694; 1H NMR (CDCl3,
400 MHz)
7.15 (dd, 1H, J ¼ 5.0 Hz, J ¼ 1.2 Hz, 5-H), 6.92e6.94 (m,
2H), 1.92e2.04 (m, 4H), 1.74e1.82 (m, 2Н), 1.53e1.58 (m, 2Н), ppm;
13C NMR (CDCl3, 100 MHz)
152.8, 126.7, 123.8, 122.3, 82.6, 42.8,
d
d
23.8 ppm; [Found: C, 64.27; H, 7.20; S, 19.07. C9H12OS requires C,
64.29; H, 7.16; S, 19.01%]; MS: m/z (ESI) 168 (38, MHþ), 150 (8), 139
(100), 111 (91).
2.4.3. 2-(Cyclopent-1-en-1-yl)thiophene (6b)
Light yellow oil, 40%; bp 94-96ꢀС/2-4 mmHg; IR (KBr), cmꢁ1
:
2954, 2842, 798, 694; 1H NMR (CDCl3, 400 MHz)
d 7.12 (dd, 1H,
J ¼ 5.0 Hz, J ¼ 0.9 Hz), 6.95 (dd, 1H, J ¼ 5.0 Hz, J ¼ .4 Hz), 6.92 (d, 2H,
J ¼ 3.4 Hz), 6.02 (br s, 1H), 2.65-2.70 (m, 2H), 2.50e2.54 (m, 2Н),
1.98e2.03 (m, 2Н) ppm; 13C NMR (CDCl3, 100 MHz)
d 141.4, 136.0,
127.3, 125.9, 123.8, 123.5, 34.4, 33.5, 23.6 ppm; [Found: C, 71.90; H,
6.72; S, 21.33. C9H10S requires C, 71.95; H, 6.71; S, 21.34%]; MS: m/z
(ESI) 150 (100, MHþ), 149 (92), 135 (52).
hꢀ
ꢁ ꢀ
ꢁi
Qf ¼ Qfr
ꢂ
Dr ꢂ n2 ꢂ A = D ꢂ n2r ꢂ Ar
2.4.4. 1-(Thiophene-2-yl)cyclohexanol (4c)
where all values with subscript r refer to the standard, D is the
optical density at the excitation wavelength, n is the refractive in-
dex of the solvent, A is the integrated intensity of the corrected
fluorescence spectrum on a cmꢁ1 scale. [48].
The formula for calculation of orientation polarizability (
the Lippert plot is [49,50].
Light yellow oil, 32%; bp 98-103ꢀС/2-4 mmHg; IR (KBr), cmꢁ1
:
3309, 2931, 2858, 1446, 1056, 960, 705, 694; 1H NMR (DMSO-d6,
400 MHz)
d
7.26 (dd,1H, J ¼ 4.12 Hz, J ¼ 2.32 Hz), 6.88e6.90 (m, 2H),
5.13 (s, OH), 1.75e1.80 (m, 2H),1.65e1.71 (m, 3H),1.51e1.58 (m, 2H),
DG) in
1.40e1.48 (m, 2Н), 1.15e1.25 (m, 1Н) ppm; 13C NMR (DMSO-d6,
100 MHz)
d 157.6, 127.0, 123.7, 121.8, 71.0, 40.3, 25.7, 22.4 ppm;

V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
437
[Found: C, 65.82; H, 7.70; S, 17.49. C10H14OS requires C, 65.89; H,
23.5; [Found: C, 67.25; H, 5.28; S, 27.51. C13H12S2 requires C, 67.20;
7.74; S, 17.59%]; MS: m/z (ESI) 182 (28, MHþ), 164 (12), 139 (100).
H, 5.21; S, 27.60%]; MS: m/z (ESI) 232 (100, Mþ), 231 (62), 217 (16).
2.4.5. 2-(4-Methylcyclohex-1-en-1-yl)thiophene (6d)
Light yellow oil, 75%; bp 102-107ꢀС/5-7 mmHg [53]; MS: m/z
(ESI) 178 (100, MHþ), 177 (85), 146 (53).
2.4.11. 1-(2,2'-bithiophene-5-yl)cyclohexanol (5c)
Yellow crystals, 56%; mp 86-88ꢀС (n-hexane) [54,55]; IR (KBr),
cmꢁ1: 3305 (OH), 2935, 2858, 1446, 1346, 1056, 960, 840, 795, 702,
690; 1H NMR (DMSO-d6, 400 MHz)
d
7.41 (dd, 1Н, J ¼ 5.0 Hz,
2.4.6. (cis-/trans-)4-Phenyl-1-(2-thienyl)cyclohexanol (4e)
White crystals, 47%; mp 78-80ꢀС; IR (KBr), cmꢁ1: 3433, 2935,
2858, 1492, 1448, 1028, 746, 700; 1H NMR (DMSO-d6, 400 MHz)
J ¼ 0.9 Hz, 5'-H), 7.18 (dd, 1Н, J ¼ 3.7 Hz, J ¼ 0.9 Hz, 3'-H), 7.06 (d, 1H,
J ¼ 3.7 Hz, 4-H), 7.02 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4'-Н), 6.82 (d, 1Н,
J ¼ 3.7 Hz, 3-Н), 5.27 (s, 1Н, OН), 1.51e1.80 (m, 6Н, CH), 1.40e1.50
d
7.39 (dd, 1H, J ¼ 5.0 Hz, J ¼ 1.3 Hz, 5-H), 7.18e7.29 (m, 2H),
(m, 4Н, СН) ppm; 13C NMR (DMSO-d6, 100 MHz)
d 157.1, 137.6,
7.08e7.12 (m, 1H), 7.06 (dd, 1H, J ¼ 3.3 Hz, J ¼ 1.3 Hz, 3-H), 6.95 (dd,
1H, J ¼ 5.0 Hz, J ¼ 3.3 Hz, 4-H), 6.91e6.94 (m, 2H), 5.25 (s, OH),
2.52e2.63 (m, 1H), 2.22e2.29 (m, 1H), 1.87e1.96 (m, 1H), 1.75e1.86
(m, 4Н), 1.58e1.63 (m, 1H), 1.45e1.54 (m, 1Н) ppm; 13C NMR
134.3, 128.8, 125.3, 124.0, 123.8, 122.8, 71.1, 71.0, 39.9, 25.6, 22.3;
[Found: C, 63.54; H, 6.18; S, 24.30. C14H16OS2 requires C, 63.60; H,
6.10; S, 24.25%]; MS: m/z (ESI) 264 (65, Mþ), 246 (30), 221 (100).
(DMSO-d6, 100 MHz)
d
152.5, 146.7, 128.8, 127.2, 127.1, 126.4, 124.9,
2.4.12. 5-(Cyclohex-1-ene-1-yl)-2,2'-bithiophene (7c)
124.4, 123.7, 121.6, 70.6, 42.7, 40.4, 29.8 ppm; [Found: C, 74.31; H,
7.10; S, 12.35. C16H18OS requires C, 74.38; H, 7.02; S, 12.41%]; MS: m/
z (ESI) 258 (7, MHþ), 240 (27), 174 (14), 139 (100).
Yellow crystals, 50%; mp 107-110ꢀС (n-hexane) [54,55]; IR (KBr),
cmꢁ1: 2925, 1427, 840, 827, 790, 684; 1H NMR (CDCl3, 400 MHz)
d
7.43 (dd, 1Н, J ¼ 5.1 Hz, J ¼ 0.9 Hz, 5'-H), 7.21 (dd, 1H, J ¼ 3.7 Hz,
J ¼ 0.9 Hz, 3'-H), 7.11 (d, 1Н, J ¼ 3.6 Hz, 4-H), 7.02 (dd, 1Н, J ¼ 5.1 Hz,
J ¼ 3.7 Hz, 4'-H), 6.92 (d, 1H, J ¼ 3.7 Hz, 3-Н), 6.11 (m, 1H, 200-H),
2.28e2.32 (m, 2Н, CH2), 2.23-2.12 (m, 2Н, CH2), 1.60e1.70 (m, 2Н,
CH2),1.50e1.55 (m, 2Н, CH2) ppm; 13C NMR (CDCl3,100 MHz) 145.4,
137.2, 134.2, 131.2, 128.8, 125.7, 124.7, 124.2, 123.2, 27.1, 25.7, 22.7,
22.1; [Found: C, 68.21; H, 5.76; S, 25.96. C14H14S2 requires C, 68.25;
H, 5.73; S, 26.03%]; MS: m/z (ESI) 246 (100, Mþ), 231 (15), 218 (45).
2.4.7. 2-(4-Phenylcyclohex-1-en-1-yl)thiophene (6e)
White crystals, 55%; mp 99-101ꢀС; IR (KBr), cmꢁ1: 2920, 2877,
1488, 1234, 806, 759, 698; 1H NMR (DMSO-d6, 400 MHz)
d 7.32 (dd,
1H, J ¼ 5.1 Hz, J ¼ 1.0 Hz, 5-H), 7.24e7.29 (m, 5H), 7.14e7.19 (m, 1H),
7.02 (dd, 1H, J ¼ 3.6 Hz, J ¼ 1.0 Hz, 3-H), 6.98 (d, 1H, J ¼ 5.1 Hz,
J ¼ 3.6 Hz, 4-H), 6.18 (br s, 1H, CHCH2), 2.74-2.82 (m, 1H), 2.45e2.53
(m, 2H), 2.34e2.43 (m, 1Н), 2.19e2.29 (m, 1H), 1.91e1.98 (m, 1H),
1.75e1.87 (m, 1H, tert-CH) ppm; 13C NMR (DMSO-d6, 100 MHz)
2.4.13. (cis-/trans-)-4-Methyl-1-(2,2'-bithiophene-5-yl)
d
146.9, 146.0, 131.2, 128.9, 128.1, 127.3, 126.6, 124.2, 123.6, 122.5,
39.6, 33.8, 29.9, 28.2 ppm; [Found: C, 79.90; H, 6.76; S, 13.38.
16H16S requires C, 79.95; H, 6.71; S, 13.34%].
cyclohexanol (5d)
Yellow crystals, 56%; mp 71-73ꢀС (n-hexane); IR (KBr), cmꢁ1
:
C
3309 (OH), 2929,1201, 989, 804, 698; 1H NMR (DMSO-d6, 400 MHz)
d
7.41 (dd, 1Н, J ¼ 5.0 Hz, J ¼ 1.4 Hz, 5'-H), 7.17 (dd, 1H, J ¼ 3.7 Hz,
2.4.8. 1-(2,2'-bithiophene-5-yl)cyclobutanol (5a)
J ¼ 1.4 Hz, 3'-H), 7.04 (d, 1Н, J ¼ 3.6 Hz, 4-H), 7.02 (dd, 1Н, J ¼ 5.0 Hz,
J ¼ 3.7 Hz, 4'-H), 6.80 (d, 1H, J ¼ 3.6 Hz, 3-Н), 5.23 (s, 1H, OH), 1.79
(br s, 1H, tert-CH), 1.06-1.72 (m, 3Н, CH), 1.28e1.48 (m, 5H, CH), 0.86
Yellow crystals, 50%; mp 66-69ꢀС (CCl4) [54,55]; IR (KBr), cmꢁ1
:
3271 (OH) (s), 3101, 2991, 2951, 2937, 1425, 1311, 1271, 1134, 1045,
839, 794, 690; 1H NMR (DMSO-d6, 400 MHz)
d
7.42 (dd, 1H, J ¼ 5.0
(d, 3Н, J ¼ 4.6 Hz, CH3) ppm; 13C NMR (DMSO-d6, 100 MHz)
d 157.5,
Hz, J ¼ 1.4 Hz, 4-Н), 7.20 (dd, 1Н, J ¼ 3.7 Hz, J ¼ 1.4 Hz, 3'-Н), 7.07 (d,
1Н, J ¼ 3.7 Hz, 3-H), 7.02 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4'-Н), 6.96 (d,
1H, ¼ 3.7 Hz, 4-H), 5.98 (s, 1H, OH), 2.25e2.37 (m, 2Н), 1.75e1.85
(m, 1H), 1.64e1.72 (m, 1H) ppm; 13C NMR (DMSO-d6, 100 MHz)
137.7, 134.2, 128.7, 125.3, 124.0, 123.8, 70.7, 31.8, 30.7, 30.0; [Found:
C, 64.76; H, 6.59; S, 23.10. C15H18OS2 requires C, 64.71; H, 6.52; S,
23.03%]; MS: m/z (ESI) 278 (35, Mþ), 260 (18), 221 (100).
d
153.6, 128.8, 125.5, 124.0, 123.8, 123.1, 73.9, 39.1, 39.0, 13.0 ppm;
2.4.14. 5-(4-Methylcyclohex-1-ene-1-yl)-2,2'-bithiophene (7d)
[Found: C, 60.90; H, 5.19; S, 27.19. C12H12OS2 requires C, 60.98; H,
5.12; S, 27.13%]; MS: m/z (ESI) 236 (30, MHþ), 218 (16), 208 (100),
193 (30).
Yellow crystals, 50%; mp 94-96ꢀС (n-hexane); IR (KBr), cmꢁ1
:
2916, 1234, 1033, 790, 694; 1H NMR (DMSO-d6, 400 MHz)
d 7.44
(dd, 1Н, J ¼ 5.0 Hz, J ¼ 1.4 Hz, 5'-H), 7.22 (dd, 1H, J ¼ 3.7 Hz,
J ¼ 1.4 Hz, 3'-H), 7.12 (d, 1Н, J ¼ 3.6 Hz, 4-H), 7.03 (dd, 1Н, J ¼ 5.0 Hz,
J ¼ 3.7 Hz, 4'-H), 6.92 (d, 1H, J ¼ 3.6 Hz, 3-Н), 6.75 (br s, 1H, CH),
2.18e2.41 (m, 3H, CH), 1.55e1.80 (m, 3H, CH), 1.16e1.30 (m, 1Н, tert-
CH), 0.92 (d, 3Н, J ¼ 6.4 Hz, CH3) ppm; 13C NMR (DMSO-d6,
100 MHz) 145.1, 137.2, 134.2, 130.8, 128.9, 125.7, 124.7, 124.3, 124.2,
123.4, 34.1, 30.9, 28.1, 27.1, 22.0; [Found: C, 69.24; H, 6.25; S, 23.01.
2.4.9. 1-(2,2'-bithiophene-5-yl)cyclopentanol (5b)
Yellow crystals, 74%; mp 53-54ꢀС (n-hexane) [54,55]; IR (KBr),
cmꢁ1: 3336 (OH), 2958, 1427, 1207, 999, 833, 790, 686; 1H NMR
(CD3CN, 400 MHz)
d
7.26 (dd, 1Н, J ¼ 5.0 Hz, J ¼ 0.9 Hz, 5'-Н), 7.14
(dd, 1H, J ¼ 3.7 Hz, J ¼ 0.9 Hz, 3'-Н), 7.02 (d, 1Н, J ¼ 3.6 Hz, 4-Н), 6.95
(dd, 1Н, J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4'-Н), 6.82 (d, 1H, J ¼ 3.6 Hz, 3-Н),
C
15H16S2 requires C, 69.18; H, 6.19; S, 24.63%]; MS: m/z (ESI) 260
1.93e1.97 (m, 4H), 1.85e1.90 (m, 2H), 1.73e1.82 (m, 2Н) ppm. 13
C
(100, Mþ), 246 (18), 218 (98).
NMR (CD3CN, 100 MHz)
124.3, 123.6, 81.9, 43.4, 24.3 ppm; [Found: C, 62.31; H, 5.60; S, 25.57.
d 153.3, 137.5, 135.0, 129.0, 125.4, 124.3,
2.4.15. 4-Phenyl-1-(2,2'-bithiophene-5-yl)cyclohexanol (5e)
White crystals, 56%; mp 183-185ꢀС (n-hexane); IR (KBr), cmꢁ1
:
C
13H14OS2 requires C, 62.36; H, 5.64; S, 25.61%]; MS: m/z (ESI) 250
(56, MHþ), 232 (100), 221 (74), 217 (76), 208 (71).
3410 (OH), 2920, 1205, 1024, 798, 700; 1H NMR (DMSO-d6,
400 MHz)
d
7.42 (dd, 1Н, J ¼ 5.0 Hz, J ¼ 1.4 Hz, 5'-H), 7.18e7.26 (m,
2.4.10. 5-(Cyclopent-1-en-1-yl)-2,2'-bithiophene (7b)
4H), 7.10e7.14 (m, 2Н), 7.09 (d, 1H, J ¼ 3.7 Hz, 4-H), 7.03 (dd, 1Н,
J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4'-H), 6.92 (d, 1H, J ¼ 3.6 Hz, 3-Н), 7.00e7.05
(m, 2H), 6.87 (d, 1H, J ¼ 3.7 Hz, 3-H), 5.42 (s, 1H, OH), 2.50e2.68 (m,
1H, tert-CH), 1.75e1.95 (m, 7H, CH) ppm; 13C NMR (DMSO-d6,
Yellow crystals, 60%; mp 86-88ꢀС (n-hexane) [54,55]; IR (KBr),
cmꢁ1: 2943, 1654 (w), 968; 1H NMR (CDCl3, 400 MHz)
d 7.18 (d, 1Н,
J ¼ 5.1 Hz, 5'-Н), 7.13 (d, 1H, Н, J ¼ 3.5 Hz, 3'-H), 7.02 (d, 1Н,
J ¼ 3.7 Hz, 4-H), 6.98 (dd, 1Н, J ¼ 5.1 Hz, J ¼ 3.7 Hz, 4'-H), 6.79 (d, 1H,
J ¼ 4.1 Hz, 3-H), 6.11 (m, 1H, 200-H), 2.70 (m, 2Н, CH2), 2.50 (m, 2Н,
CH2), 2.01 (m, 2Н, CH2) ppm; 13C NMR (CDCl3, 100 MHz) 140.3,
137.8, 136.6, 135.5, 127.9, 126.3, 124.3, 124.2, 123.9, 123.5, 34.0, 33.5,
100 MHz) d 157.3, 147.7, 146.6, 137.6, 135.4,134.3, 128.9, 128.8, 128.8,
127.2, 127.2, 123.9, 70.6, 43.2, 31.3, 29.8 ppm; [Found: C, 70.62; H,
5.97; S, 18.78. C20H20OS2 requires C, 70.55; H, 5.92; S, 18.83%]; MS:
m/z (ESI) 260 (100, Mþ), 246 (18), 218 (98).

438
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
2.4.16. 5-(4-Phenylcyclohex-1-ene-1-yl)-2,2'-bithiophene (7e)
Yellow crystals, 50%; mp 153-155ꢀС (n-hexane); IR (KBr), cmꢁ1
7.21e7.25 (m, 2H, C6Н5), 7.07 (d, 1Н, J ¼ 3.9 Hz, 3-H), 6.52 (br s, 1Н,
CН), 2.82e2.93 (m, 1H, CH), 2.51e2.62 (m, 3H, CH), 2.31-2.42 (m,
:
2924, 1427, 833, 798, 796, 700, 690; 1H NMR (DMSO-d6, 400 MHz)
1H, CH), 2.08e2.17 (m, 1H, CH), 1.83e1.98 (m, 1H, tert-CH) ppm; 13
C
d
7.46 (dd, 1Н, J ¼ 5.0 Hz, J ¼ 1.4 Hz, 5'-H), 7.33 (dd, 1Н, J ¼ 3.6 Hz,
NMR (CDCl3, 100 MHz) 182.9, 156.5, 146.0, 140.7, 137.3, 130.9, 128.6,
128.3, 126.9, 126.5, 122.6, 39.5, 33.9, 29.7, 27.9; [Found: C, 76.1; H,
6.0; S, 12.0. C17H16OS requires C, 76.08; H, 6.01; S, 11.95%].
J ¼ 1.4 Hz, 3'-H), 7.23e7.28 (m, 5Н), 7.15 (d, 1H, J ¼ 3.7 Hz, 4-H), 7.08
(dd, 1Н, J ¼ 5.0 Hz, J ¼ 3.7 Hz, 4'-H), 6.98 (d, 1H, J ¼ 3.7 Hz, 3-Н), 6.20
(br s, 1H, ¼CH), 2.73e2.85 (m, 1H, tert-CH), 2.45e2.55 (m, 2H, CH),
2.35e2.40 (m, 1H, CH), 2.22e2.31 (m, 1H, CH), 1.90e2.00 (m, 1H,
CH), 1.75e1.90 (m, 1H, CH) ppm; 13C NMR (DMSO-d6, 100 MHz)
146.8,144.9,137.1,136.4,136.1,135.2, 134.4,131.0, 128.9,127.3,126.4,
125.7, 124.9, 124.4, 123.6, 33.8, 29.8, 27.8; [Found: C, 74.53; H, 5.67;
S, 19.81. C20H18S2 requires C, 74.49; H, 5.63; S, 19.89%].
2.5.6. 2-(2,2'-bithiophene-5-yl)cyclobut-1-ene-1-ylcarbaldehyde
(9
а
)
Yellow crystals, 71%; mp 125-127ꢀС (CCl4) [54,55]; IR (KBr),
cmꢁ1: 1643 (C]O), 1596, 1446, 1195, 798, 737; 1H NMR (DMSO-d6,
400 MHz)
d
9.72 (s, 1Н, СНО), 7.58 (dd, 1Н, J ¼ 5.1 Hz, J ¼ 0.9 Hz, 5'-
H), 7.47 (d, 1Н, J ¼ 3.9 Hz, 4-H), 7.42 (dd, 1Н, J ¼ 3.7 Hz, J ¼ 0.9 Hz,
3'-H), 7.35 (d, 1H, J ¼ 3.9 Hz, 3-H), 7.10 (dd, 1H, J ¼ 5.1 Hz, J ¼ 3.7 Hz,
4'-H), 2.81e2.86 (m, 2H, CН), 2.61e2.68 (m, 2H, CH) ppm; 13C NMR
(DMSO-d6, 100 MHz) 185.6, 150.0, 141.9, 136.2, 134.5, 133.7, 132.7,
129.2, 127.6, 126.1, 125.3, 28.4, 24.7 ppm; [Found: C, 63.4; H, 4.1; S,
26.0. C13H10OS2 requires C, 63.38; H, 4.09; S, 26.03%]; MS: m/z (ESI)
246 (100, Mþ), 218 (95), 217 (55), 184 (45), 166 (84).
2.5. General procedure for the VilsmeiereHaack reaction
Compounds 4a-4c, 4e, 5a-5e, 6b, 6d, 6e, 7b-7e (10 mmol) and
DMF (25 mmol) were dissolved in dry 1.2-dichloroethane
(10e20 mL). To the reaction mixture was added POCl3 (17 mmol)
at 8-10ꢀС and the mixture was stirred at rt for 2 h. The reaction was
quenched by the addition of crushed ice, was neutralized by
aqueous solution of Na2CO3 (10%) and the layers were separated.
The aqueous layer was extracted by 1.2-dichloroethane (2 ꢂ 15 mL),
collected, washed by the water and was dried over anhydrous
MgSO4. After filtration, the solvent was evaporated on a rotary
evaporator and the obtained residue was purified by column
chromatography on silica gel using carbon tetrachloride as eluent.
2.5.7. 2-(2,2'-bithiophene-5-yl)cyclopent-1-ene-1-ylcarbaldehyde
(9b)
Yellow crystals, 64%; mp 99-100ꢀС (CCl4) [54,55]; IR (KBr),
cmꢁ1: 1635 (C]O), 1577, 1446, 1218, 810, 721, 709; 1H NMR (CDCl3,
400 MHz)
d
10.35 (s, 1Н, СНО), 7.27 (dd, 1Н, J ¼ 5.2 Hz, J ¼ 0.9 Hz, 5'-
H), 7.23 (d, 1Н, J ¼ 3.7 Hz, 4-H), 7.17 (dd, 1Н, J ¼ 3.8 Hz, J ¼ 0.9 Hz,
3'-H), 7.14 (d, 1H, J ¼ 3.9 Hz, 3-H), 7.04 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.7 Hz,
4'-H), 3.00e3.10 (m, 2H, СН), 2.72e2.80 (m, 2H, СН), 1.92e2.07 (m,
2Н, СH) ppm; 13C NMR (CDCl3, 100 MHz) 188.8, 151.7, 141.1, 138.1,
136.5, 135.3, 130.7, 128.2, 125.7, 124.8, 123.9, 39.5, 31.8, 21.6 ppm;
[Found: C, 64.6; H, 4.7; S, 24.6. C14H12OS2 requires C, 64.58; H, 4.65;
S, 24.63%]; MS: m/z (ESI) 260 (100, Mþ), 259 (25), 231 (30), 203 (24),
199 (28), 166 (25), 127 (75).
2.5.1. 2-(Thiophene-2-yl)cyclobut-1-ene-1-carbaldehyde (8
Yellow crystals, 55%; mp 67-68ꢀС (CCl4); IR (KBr), cmꢁ1: 1651
(C]O), 1600, 732; 1H NMR (CDCl3, 400 MHz)
9.91 (s, 1H, CНO),
а)
d
7.48 (dd, 1H, J ¼ 5.0 Hz, J ¼ 0.9 Hz, 5-H), 7.36 (dd, 1H, J ¼ 3.7 Hz,
J ¼ 0.9 Hz, 3-H), 7.08 (dd, 1H, J ¼ 3.7 Hz, J ¼ 5.0 Hz, 4-H); 2.85e2.88
(m, 2H, CH), 2.73e2.76 (m, 2H, CH) ppm; 13C NMR (CDCl3, 100 MHz)
185.2, 151.1, 136.3, 133.9, 130.3, 129.8, 127.9, 28.3, 24.4; [Found: C,
65.83; H, 4.92; S,19.56. C9H8OS requires C, 65.83; H, 4.91; S,19.53%].
2.5.8. 5'-(Cyclohex-1-ene-1-yl)-2,2'-bithiophene-5-carbaldehyde
(11c)
2.5.2. 2-(Thiophene-2-yl)cyclopent-1-ene-1-carbaldehyde (8b)
Yellow crystals, 70%; mp 44-45ꢀС (CCl4); IR (KBr), cmꢁ1: 1651
Yellow crystals, 35%; mp 105-107ꢀС (CCl4); IR (KBr), cmꢁ1: 1654
(C]O), 1458, 1207, 790; 1H NMR (DMSO-d6, 400 MHz)
d 9.83 (s, 1Н,
(C]O), 1589, 721; 1H NMR (CDCl3, 400 MHz)
d
10.29 (s, 1H, CНO),
СНО), 7.94 (d, 1Н, J ¼ 4.1 Hz, 4-H), 7.44 (2d, 2Н, J ¼ 4.1 Hz, J ¼ 4.1 Hz,
3-H, 3'-H), 7.21 (d, 1Н, J ¼ 4.1 Hz, 4'-H), 6.20e6.21 (br s, 1H, CH),
2.30e2.35 (m, 2H, СН), 2.21e2.26 (m, 2H, СН), 1.51e1.62 (m, 2Н,
СН) ppm; 13С NMR (DMSO-d6, 100 MHz) 184.2, 149.5, 148.4, 139.8,
139.3, 137.0, 136.3, 131.9, 129.0, 126.8, 125.3, 27.1, 25.7, 22.6, 22.0;
[Found: C, 65.7; H, 5.1; S, 23.4. C15H14OS2 requires C, 65.66; H, 5.14;
S, 23.37%]; MS: m/z (ESI) 274 (100, Mþ), 246 (37), 245 (24), 217 (17),
184 (26), 171 (22), 127 (56).
7.44 (dd, 1H, J ¼ 5.0 Hz, J ¼ 0.9 Hz, 5-H), 7.25 (dd, 1H, J ¼ 3.6 Hz,
J ¼ 0.9 Hz, 3-H), 7.08 (dd, 1H, J ¼ 3.6 Hz, J ¼ 5.0 Hz, 4-H), 3.00e3.05
(m, 2H, CH), 2.73e2.77 (m, 2H, CH), 1.94e2.01 (m, 2H, CH) ppm; 13
C
NMR (CDCl3, 100 MHz) 189.3, 152.4, 138.3, 136.9, 129.6, 128.9, 127.8,
39.9, 31.65, 31.02, 21.57; [Found: C, 67.39; H, 5.66; S, 17.98. C10H10OS
requires C, 67.38; H, 5.65; S, 17.99%].
2.5.3. 5-(Cyclohex-1-en-1-yl)thiophene-2-carbaldehyde (10c)
Pale yellow crystals, 65%; mp 53-58ꢀС (CCl4); IR (KBr), cmꢁ1
:
2.5.9. 5'-(4-Methylcyclohex-1-en-1-yl)-2,2'-bithiophene-5-
carbaldehyde (11d)
2931, 1657, 1448, 1230, 806; 1H NMR (CDC13, 400 MHz) 9.84 (s, 1H,
CHO), 7.60 (d, 1H, J ¼ 3.6 Hz, 4-H), 7.01 (d, 1H, J ¼ 3.6 Hz), 6.43 (br s,
1H, CH), 2.38e2.41 (m, 2H, CH), 2.18e2.23 (m, 1H, CH), 1.72e1.80
(m, 1H, CH), 1.63e1.68 (m, 1H, CH); 13C NMR (CDCl3, 100 MHz)
182.8, 157.2, 140.5, 137.2, 131.1, 129.0, 122.2, 27.4, 25.9, 22.5, 21.8;
[Found: C, 68.7; H, 6.3; S,16.7. C11H12OS requires C, 68.71; H, 6.29; S,
16.68%]; MS: m/z (ESI) 192 (100, MHþ), 163 (86), 135 (93), 91 (32).
Yellow crystals, 35%; mp 156-158ꢀС (CCl4); IR (KBr), cmꢁ1: 1655
(C]O), 1456, 1228, 1047, 792; 1H NMR (DMSO-d6, 400 MHz)
d 9.83
(s,1Н, СНО), 7.93 (d, 1H, J ¼ 4.0 Hz, 4-H), 7.44 (d,1H, J ¼ 4.0 Hz, 3-H),
7.42 (d, 1H, J ¼ 3.6 Hz, 3'-H), 7.03 (d, 1H, J ¼ 3.6 Hz, 4'-H), 6.18 (br s,
1H, CH), 2.39e2.44 (m, 1H, CH), 2.30e2.38 (m, 1H, CH), 2.18e2.23
(m, 1H, CH), 1.72e1.81 (m, 2H, CH), 1.59e1.68 (m, 1H, СН), 1.21e1.32
(m,1H, tert-СН), 0.93 (d, 3H, J ¼ 6.4 Hz, CH3) ppm; 13C NMR (DMSO-
d6, 100 MHz) 184.2, 148.2, 146.3, 141.4, 139.8, 132.7, 130.7, 127.9,
125.8, 125.3, 123.9, 34.2, 30.8, 28.0, 27.1, 21.9 ppm; [Found: C, 66.6;
H, 5.6; S, 22.2. C16H16OS2 requires C, 66.63; H, 5.59; S, 22.23%].
2.5.4. 5-(4-Methylcyclohex-1-en-1-yl)thiophene-2-carbaldehyde
(10d)
Pale yellow crystals, 65%; mp 75-78ꢀС (CCl4) [53].
2.5.5. 5-(4-Phenylcyclohex-1-en-1-yl)thiophene-2-carbaldehyde
(10e)
2.5.10. 5'-(4-Phenylcyclohex-1-en-1-yl)-2,2'-bithiophene-5-
carbaldehyde (11e)
White crystals, 60%; mp 82-83ꢀС (CCl4); IR (KBr), cmꢁ1: 1654
Yellow crystals, 35%; mp 169-172ꢀС (CCl4); IR (KBr), cmꢁ1: 1654
(C]O), 1458, 1226, 792; 1H NMR (CDCl3, 400 MHz)
d
9.83 (s, 1Н,
(C]O), 1456, 1228, 1047; 1H NMR (DMSO-d6, 400 MHz)
d
9.83 (s,
СНО), 7.64 (d, 1H, J ¼ 3.9 Hz, 4-H), 7.30e7.35 (m, 3Н, C6Н5),
1H, CHO), 7.94 (d, 1H, J ¼ 4.0 Hz, 4-H), 7.48 (d, 1H, J ¼ 4.0 Hz, 3-H),

V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
439
7.47 (d, 1H, J ¼ 3.8 Hz, 3'-H), 7.25e7.29 (m, 4H, C6Н5), 7.15e7.19 (m,
1H, C6Н5), 7.09 (d, 1H, J ¼ 3.8 Hz, 4'-H), 6.31 (br s,1H, CH), 2.76e2.85
(m, 1H, CH), 2.44e2.53 (m, 2H, CH), 2.38e2.43 (m, 1H, CH),
2.22e2.33 (m, 1H, CH), 1.92e2.00 (m, 1H, CH), 1.80e1.89 (m, 1H,
tert-CH) ppm; 13C NMR (DMSO-d6, 100 MHz) 184.3, 147.9, 146.7,
141.5, 139.9, 130.9, 128.9, 128.1, 127.3, 126.7, 125.9, 125.4, 124.3, 33.9,
29.8, 27.8 ppm; [Found: C, 71.9; H, 5.2; S, 18.3. C21H18OS2 requires C,
71.96; H, 5.18; S, 18.30%].
J ¼ 3.8 Hz, 4-H), 7.31e7.35 (m, 2H, C6H5), 7.22e7.26 (m, 3H, C6H5),
6.94 (d, 1H, J ¼ 3.8 Hz, 3-H), 2.82e2.91 (m, 1H, CH), 2.49e2.59 (m,
3H, CH), 2.30e2.41 (m, 1H, CH), 2.08e2.16 (m, 1H, CH), 1.85e1.96
(m,1H, tert-CH) ppm; 13C NMR (CDCl3,100 MHz) 153.8,145.9,138.0,
130.3, 128.7, 127.9, 126.9, 126.5, 121.7, 114.8, 106.3, 39.5, 33.9, 29.6,
28.1 ppm; [Found: C, 74.9; H, 5.7; N, 6.0; S,12.1. C17H15NS requires C,
74.94; H, 5.70; N, 5.98; S, 12.08%].
2.6.6. 2-(2,2'-bithiophene-5-yl)cyclobut-1-ene-1-ylcarbonitrile
2.6. General procedure for nitrile synthesis
(13а)
Yellow crystals, 75%; mp 105-107ꢀС (CCl4); IR (KBr), cmꢁ1: 2923,
2195, 1612, 1612, 1446, 806, 718; 1H NMR (DMSO-d6, 400 MHz)
Compounds 8ae8b, 10ce10e or 9ae9b, 11ce11e (10 mmol) and
NH2OH*HCl (25 mmol) were dissolved in dry pyridine (10 mL). The
reaction mixture was refluxed for 1 h, than cooled and propanoic
anhydride (20 mmol) was added. The reaction mixture was
refluxed for 1 more h and then was poured into cold water. The
substance was extracted with 1,2-dichloroethane (in the thiophene
series) or crude precipitate (in the bithiophene series) was filtered,
dried and the obtained residue was purified by column chroma-
tography on silica gel using carbon tetrachloride as eluent.
d
7.59 (dd, 1Н, J ¼ 5.0 Hz, J ¼ 1.2 Hz, 5'-H), 7.44 (dd, 1Н, J ¼ 3.8 Hz,
1.2 Hz, 3'-H), 7.34 (d,1Н, J ¼ 3.9 Hz, 4-H), 7.33 (d,1H, J ¼ 3.9 Hz, 3-H),
7.10 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.8 Hz, 4'-H), 2.84e2.76 (m, 2H, CН),
2.76e2.80 (m, 2H, CH) ppm; 13C NMR (DMSO-d6, 100 MHz) 154.3,
140.9, 135.9, 133.9, 131.0, 129.3, 127.7, 126.2, 125.1, 115.4, 101.8, 29.8,
28.6 ppm; [Found: C, 64.2; H, 3.7; N, 5.8; S, 26.4. C13H9NS2 requires
C, 64.16; H, 3.73; N, 5.76; S, 26.35%].
2.6.7. 2-(2,2'-bithiophene-5-yl)cyclopent-1-ene-1-ylcarbonitrile
(13b)
2.6.1. 2-(Thiophene-2-yl)cyclobut-1-ene-1-carbonitrile (12
Yellow crystals, 75%; mp 63-65ꢀС (CCl4); IR (KBr), cmꢁ1: 2927,
2198, 1612, 1419, 717; 1H NMR (CDCl3, 400 MHz)
7.46 (dd, 1H,
J ¼ 5.0 Hz, J ¼ 0.9 Hz, 5-H), 7.35 (dd, 1H, J ¼ 3.6 Hz, J ¼ 0.9 Hz, 3-H),
7.07 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.6 Hz, 4-H), 2.86e2.89 (m, 2H, CH),
2.82e2.85 (m, 2H, CH) ppm; 13C NMR (CDCl3,100 MHz) 154.0,136.1,
129.2, 128.1, 127.9, 115.0, 102.2, 29.6, 28.6 ppm; [Found: C, 65.1; H,
4.4; N, 8.7; S, 19.9. C9H7NS requires C, 65.07; H, 4.38; N, 8.69; S,
19.89%].
а)
Yellow crystals, 64%; mp 96-97ꢀС (CCl4); IR (KBr), cmꢁ1: 2202,
d
1600, 1450, 795, 725; 1H NMR (CDCl3, 400 MHz)
d
7.42 (d, 1Н, J ¼ 3.9
Hz, 4-H), 7.22e7.28 (m, 2Н, 3'-H, 5'-H), 7.14 (d, 1Н, J ¼ 3.9 Hz, 3-H),
7.03 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.9 Hz, 4'-H), 2.89e2.96 (m, 2H, CН),
2.75e2.83 (m, 2H, CH), 2.03e2.14 (m, 2H, CH) ppm; 13C NMR
(CDCl3, 100 MHz) 150.6,140.4,136.7,135.4,129.7,128.2,125.6,124.8,
124.1, 118.1, 103.6, 36.5, 35.9, 22.8 ppm; [Found: C, 65.3; H, 4.3; N,
5.5; S, 24.9. C14H11NS2 requires C, 65.33; H, 4.31; N, 5.44; S, 24.92%].
2.6.2. 2-(Thiophene-2-yl)cyclopent-1-ene-1-carbonitrile (12b)
Yellow crystals, 74%; mp 85-88ꢀС (CCl4); IR (KBr), cmꢁ1: 2206,
2.6.8. 5'-(Cyclohex-1-ene-1-yl)-2,2'-bithiophene-5-carbonitrile
(15c)
1605,1421, 731; 1H NMR (CDCl3400 MHz)
d
7.56 (d,1H, J ¼ 3.6 Hz, 3-
Yellow crystals, 60%; mp 60-65ꢀС (CCl4); IR (KBr), cmꢁ1: 2924,
H), 7.44 (d, 1H, J ¼ 5.0 Hz, 5-H), 7.09 (dd, 1H, J ¼ 5.0 Hz, J ¼ 3.6 Hz, 4-
H), 2.91e2.96 (m, 2H, CH), 2.77e2.82 (m, 2H, CH), 2.05e2.2.12 (m,
2H, CH) ppm; 13C NMR (CDCl3, 100 MHz) 150.9, 136.9, 128.6, 128.4,
127.8, 118.1, 103.8, 36.8, 35.9, 22.8 ppm; [Found: C, 68.5; H, 5.2; N,
8.0; S, 18.3. C10H9NS requires C, 68.53; H, 5.18; N, 7.99; S, 18.30%].
2214, 1438, 1049, 787; 1H NMR (CDCl3, 400 MHz)
d 7.48 (d, 1H,
J ¼ 3.8 Hz, 4-H), 7.13 (d, 1H, J ¼ 3.9 Hz, 4'-H), 7.06 (d, 1H, J ¼ 3.8 Hz,
3-H), 6.86 (d, 1H, J ¼ 3.9 Hz, 3'-H), 6.21e6.25 (br s, 1H, CH),
2.36e2.42 (m, 2H, CH), 2.18e2.24 (m, 2H, CH), 1.73e1.82 (m, 2H,
CH), 1.61e1.69 (m, 2H, CH) ppm; 13C NMR (CDCl3, 100 MHz) 148.9,
145.3, 138.4, 131.7, 130.9, 126.3, 126.1, 122.9, 122.2, 114.4, 106.7, 27.3,
25.8, 22.6, 22.0 ppm; [Found: C, 66.4; H, 4.8; N, 5.2; S, 23.6.
2.6.3. 5-(Cyclohex-1-en-1-yl)thiophene-2-carbonitrile (14c)
Yellow crystals, 70%; mp 40-41ꢀС (CCl4); IR (KBr), cmꢁ1: 2214,
C15H13NS2 requires C, 66.38; H, 4.83; N, 5.16; S, 23.63%].
1446, 1431, 1243, 810; 1H NMR (СDCl3, 400 MHz)
d 7.44 (d, 1H,
J ¼ 4.1 Hz, 4-H), 6.89 (d, 1H, J ¼ 4.1 Hz, 3-H), 6.31 (br s, 1H, CH),
2.30e2.38 (m, 2H, CH), 2.17e2.27 (m, 2H, CH), 1.73 (m, 2H, CH),
1.60e1.68 (m, 2H, CH) ppm; 13C NMR (CDCl3, 100 MHz) 154.6,138.0,
130.4, 128.6, 121.3, 114.9, 105.9, 27.5, 25.9, 22.5, 21.8; [Found: C,
69.8; H, 5.9; N, 7.4; S, 16.9. C11H11NS requires C, 69.80; H, 5.86; N,
7.40; S, 16.94%].
2.6.9. 5'-(4-Methylcyclohex-1-en-1-yl)-2,2'-bithiophene-5-
carbonitrile (15d)
Yellow crystals, 70%; mp 125-126ꢀС (CCl4); IR (KBr), cmꢁ1: 2214,
1589, 1454, 786; 1H NMR (CDCl3, 400 MHz)
d
7.49 (d, 1H, J ¼ 3.9 Hz,
4-H), 7.12 (d, 1H, J ¼ 3.8 Hz, 4'-H), 7.06 (d, 1H, J ¼ 3.9 Hz, 3-H) 6.86
(d, 1H, J ¼ 3.8 Hz, 3'-H), 6.19-6.21 (br s, 1H, CH), 2.38e2.46 (m, 2H,
CH), 2.24e2.33 (m,1H, CH),1.77e1.89 (m, 2H, CH),1.67e1.76 (m,1H,
2.6.4. 5-(4-Methylcyclohex-1-en-1-yl)thiophene-2-carbonitrile
(14d)
CH),1.31e1.42 (m,1H, tert-CH),1.00 (d, 3H, J ¼ 6.4 Hz, CH3) ppm; 13
C
NMR (CDCl3, 100 MHz) 148.7, 145.2, 138.4, 131.7, 130.5, 126.3, 125.7,
122.9, 122.3, 114.4, 106.8, 34.3, 30.8, 29.8, 28.1, 27.3, 21.6 ppm;
[Found: C, 67.3; H, 5.3; N, 4.9; S, 22.5. C16H15NS2 requires C, 67.33;
H, 5.30; N, 4.91; S, 22.47%].
Yellow crystals, 70%; mp 55-56ꢀС (CCl4); IR (KBr), cmꢁ1: 2924,
2214, 1446, 802; 1H NMR (СDCl3, 400 MHz)
d
7.44 (d, 1H, J ¼ 3.9 Hz,
4-H), 6.89 (d, 1H, J ¼ 3.9 Hz, 3-H), 6.25e6.30 (br s, 1H, CH),
2.36e2.44 (m, 2H, CH), 2.23e2.33 (m, 2H, CH), 1.68e1.88 (m, 3H,
CH), 1.29e1.41 (m, 1H, tert-CH), 0.98 (d, 3H, J ¼ 6.4 Hz, CH3) ppm;
13C NMR (CDCl3, 100 MHz) 154.3, 137.9, 130.0, 128.1, 121.4, 114.9,
105.9, 34.3, 30.6, 27.9, 27.5, 21.6; [Found: C, 70.9; H, 6.5; N, 6.89; S,
15.8. C12H13NS requires C, 70.89; H, 6.45; N, 6.89; S, 15.77%].
2.6.10. 5'-(4-Phenylcyclohex-1-en-1-yl)-2,2'-bithiophene-5-
carbonitrile (15e)
Yellow crystals, 75%; mp 151-153ꢀС (CCl4); IR (KBr), cmꢁ1: 2210,
1438, 795; 1H NMR (CDCl3, 400 MHz)
d
7.51 (d, 1H, J ¼ 3.9 Hz, 4-H),
7.29e7.35 (m, 2H, C6H5), 7.22e7.28 (m, 3H, C6H5), 7.15 (d, 1H,
J ¼ 3.8 Hz, 3'-H), 7.08 (d, 1H, J ¼ 3.9 Hz, 3-H), 6.90 (d, 1H, J ¼ 3.8 Hz,
4'-H), 6.32 (br s, 1H, CH), 2.82e2.91 (m, 1H, CH), 2.47e2.59 (m, 3H,
CH), 2.30e2.41 (m, 1H, CH), 2.08e2.14 (m, 1H, CH), 1.85e1.97 (m,
1H, CH) ppm; 13C NMR (CDCl3, 100 MHz) 148.2, 146.3, 145.1, 138.4,
2.6.5. 5-(4-Phenylcyclohex-1-en-1-yl)thiophene-2-carbonitrile
(14e)
Yellow crystals, 75%; mp 117-120ꢀС (CCl4); IR (KBr), cmꢁ1: 2945,
2216, 1631, 1444, 1230, 804; 1H NMR (CDCl3, 400 MHz)
d 7.48 (d, 1H,

440
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
132.0, 130.7, 128.6,126.9, 126.4, 125.4, 122.9,122.7, 114.5, 106.9, 39.7,
33.9, 29.7, 27.9 ppm; [Found: C, 72.6; H, 4.9; N, 4.0; S, 18.5.
time (up to 12 h) without heating or extended heating time of the
reaction mixture may facilitate preferable formation of cyclic al-
kenes 6b, 6d, 6e and 7be7e. In some cases, the thiophene alcohols
4b, 4c and 4d may undergo dehydration process during vacuum
distillation.
C
21H17NS2 requires C, 72.58; H, 4.93; N, 4.03; S, 18.45%].
3. Results and discussion
The formylation of thiophene and 2,2'-bithiophene is usually
achieved by the VilsmeiereHaack reaction forming, after the hy-
drolysis of iminium salts as intermediates, corresponding 2- and 5-
formyl derivatives [67e69]. Thus the reaction of substituted sty-
renes and 1-phenylcyclohexene with the Vilsmeier reagent leads to
the formation of cinnamaldehyde derivatives only [70,71]. We
decided to study the VilsmeiereHaack reaction of thiophenes 4a-
4c, 4e, 6b, 6d, 6e and 2,2'-bithiophenes 5ae5e, 7be7e with alicyclic
fragments because of two possible reaction pathways may take
place in the formylation process.
The VilsmeiereHaack formylation was carried out using DMF/
POCl3 at room temperature for 3 h in 1,2-dichloroethane that
allowed to increase yields on 10% in comparison with experiments
without solvent (Scheme 2). The formylation reaction of tertiary
alcohols 4ae4c, 4e, 5ae5e or cyclic alkenes 6b, 6d, 6e, 7be7e gave
us the same structures of aldehydes (8ae8b, 9ae9b, 10ce10e,
11ce11e). It may be presumed that in the VilsmeiereHaack reac-
tion tertiary alcohols 4a-4c, 4e, 5a-5e at first undergo elimination
reaction to form corresponding cycloalkenes and only then for-
mylation occurs. In our research the results in the formylation
process may be explained with the change in the alicyclic ring size
at thiophene/2,2'-bithiophene structures.
3.1. Chemistry
Halogen derivatives of thiophene and 2,20-bithiophene easily
form Grignard reagents and used for the synthesis of such tertiary
alcohols [56e62]. The main problem in the synthesis of tertiary
alcohols is their ability to eliminate water very easily to yield al-
kenes [36,63,64].
The reaction of Grignard reagents 1a, 1b, 2a, 2b prepared from
2-halogenthiophenes or 5-halogen-2,2'-bithiophenes with cyclo-
alkanones 3b-3e produced not only tertiary alcohols 4ae4c, 4e and
5ae5e but also corresponding cyclic alkenes 6b, 6d, 6e and 7be7e
(Scheme 1). The Grignard reagents 1a, 1b, 2a, 2b react with
cyclobutanone (3a) and form only tertiary alcohols 4a, 5a due to
greater strain energy in the cyclobutene ring than in the cyclo-
butane [65,66]. The reaction of thiophene compounds 1a, 1b with
cyclohexanone (3c) leads to formation only tertiary alcohol 4c.
However, in the 2,2'-bitiophene series we obtained a mixture of
alcohol 5c and olefin 7c at the ratio 4/1. Due to the reaction of
compounds 1a, 1b, 2a, 2b with cyclopentanone (3b) we obtained a
mixture of tertiary alcohols and cycloalkenes at the ratio 4/1 in the
thiophene series (4b, 6b) and at the 5.5/1 ratio for bithiophene
structures (5b, 7b). In contrast, the reaction of 1a and 1b with 4-
methylcyclohexanone (3d) gives only cyclic olefin 6d. The
mixture of tertiary alcohols 4e, 5e and cyclic alkenes 6e, 7e were
obtained in the reaction of ketone 3e with Grignard reagents 1a and
1b at the ratio 5:1, respectively.
The results of formylation tertiary alcohols 4a, 4b, 5a, 5b as well
as cyclic olefin systems 5a, 5b, 6b, 7b showed the formation only
a,b-unsaturated aldehydes 8a, 8b, 9a, 9b. Therefore, the Vils-
meiereHaack formylation of hydroxycyclohexyl- (4c, 4e, 5c-5e)
and cyclohexenyl- (6d, 6e, 7c-7e) containing compounds produced
only 5'-formylbithiophenes 11ce11e.
In all experiments, the reaction between bithiophene com-
pounds 2a, 2b and ketones 3b-3e lead to the mixture of tertiary
alcohols 5b-5e and cycloalkenes 7b-7e. Perhaps, reaction of
bithiophene's Grignard reagents with ketones 3b-3e depends on
reaction conditions. Therefore, the valuable decomposition condi-
tions of reaction mixture in the cases of compounds (2a, 2b) with
cyclopentanone (3b), cyclohexanone (3c), 4-methylcyclohexanone
(3d) and 4-phenylcyclohexanone (3e) allowed to control the reac-
tion process and to obtain desired products 5b-5e and cycloalkenes
7b-7e with good yields (Scheme 1). Therefore it was found that the
ratio of tertiary alcohol/cycloalkene in the 2,2'-bithiophene series
depends on reaction conditions and substrates structure [54,55]. To
avoid dehydration reaction and to reduce yield of cycloalkenes the
dilute aqueous solution of ammonia chloride for decomposition of
reaction mixture at 5e10 ꢀC was used. These mild reaction condi-
tions allowed to form the tertiary alcohols 5be5e as the main
compounds with traces of corresponding cycloalkenes 7be7e.
However, it was not possible to completely avoid the olefin for-
mation via the elimination process. In addition, the decomposition
of reaction mixture at 15e20 ꢀC produced mainly unsaturated
compounds 6b, 6d, 6e and 7be7e. Moreover, the extended reaction
The results showed that the alicyclic ring size has significant
influence on the electronic p-system of the molecule. Therefore, in
the heterocyclic systems with cyclopentyl 4b, 5b, 6b, 7b and
formed from substrates 4a, 5a which contain strained cyclobutenyl
fragments the main pathway is formation of
a,b-unsaturated al-
dehydes 8a, 8b, 9a, 9b.
It is known the cyano group is strong electron withdrawing
substituent with great potential in the synthetic organic chemistry
and is part of molecules in the new materials for electronic devices
[72-74]. Therefore to continue the research work and to introduce
new perspective fluorophores we obtained from aldehydes 8a, 8b,
9a, 9b, 10ce10e, 11ce11e corresponding nitriles 12a, 12b, 13a, 13b,
14ce14e, 15ce15e by one-pot synthesis (Scheme 3).
3.2. Photophysical parameters of 2,20-bithiophenes with alicyclic
fragments
The substituents in the aromatic systems are the most impor-
tant factors to determine the absorption and fluorescence
properties. Planar and rigid molecules usually show wide-range
Scheme 1. Synthesis of tertiary alcohols 4ae4c, 4e, 5ae5e and cycloalkenes 6b, 6d, 6e, 7be7e.

V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
441
Scheme 2. Synthesis of aldehydes by the VilsmeiereHaack reaction.
well-resolved spectra in comparison with non-aromatic molecules.
In addition, there are some more factors that influence on the
fluorescent characteristics of molecules for example, solvent po-
larity, temperature, purity of sample [75].
In order to study the dependence between the molecular
structure and photophysical properties of the new fluorophores we
measured absorbance and fluorescence spectra in solvents such as
THF, acetonitrile, pyridine, ethanol and diethylene glycol at low
concentrations (10ꢁ6 mol/l) (Tables 1 and 2).
The presence of formyl group in the
a
,
b
-unsaturated aldehyde
9a leads to large red shift in emission spectra, for example, 84 nm in
n-hexane, 120 nm in ethanol and 143 nm in diethylene glycol in
contrast with disubstituted 2,20-bithiophenes 11d, 15d, which
showed lower Stokes shifts (60e110 nm) (Figs. 2 and 3).
The formyl derivatives of 2,20-bithiophene with cyclohexenyl
scaffold 11c-11e in comparison with cyclic alkenes 7c-7e have
moderate red shifts in the absorption (avg. 45 nm) and large in the
emission spectra (up to 110 nm) in all solvents (Table 2). The other
For thiophene derivatives we observed very low-intensity
fluorescence hence the photophysical parameters were measured
for 2,2'-bithiophene derivatives only. It is known that the contours
of spectra measured in n-hexane are similar to the spectra
measured in gas phase conditions [49]. Thereby for all synthesized
compounds: tertiary alcohols 5ae5e, cycloalkenes 7be7e, alde-
hydes 9a, 9b, 11ce11e and nitriles 13a, 13b, 15ce15e, we observed
two or three absorption maxima in n-hexane that possibly corre-
spond to the discrete electronic transitions in the molecules.
However, the comparison of 2,20-bithiophene per se with
bithiophenes bearing alicyclic fragments 5a-5e, 7be7e showed that
the alicyclic moiety provide red-shift (up to 33 nm) in absorbance
spectra. The comparison absorbance spectra of phenyl containing
alcohol 5e and cycloalkene 7e showed that the presence of the
olefin fragment in the compound 7e leads to slight bathochromic
shift (up to 30 nm) in all solvents. The presence of alicyclic units
facilitates not only red-shift in absorbance spectra, but also large
values of fluorescence intensity in contrast with 2,20-bithiophene.
Comparison of emission spectra of tertiary alcohols 5ae5d and
cycloalkenes 7be7d showed that the hydroxycycloalkyl- and
cycloalkenyl fragments have the similar influence on the fluores-
cence maxima in all solvents (Table 1). That may suggests the main
electronic transitions in compounds 5ae5d, 7be7d are formed by
the 2,20-bithiophene unit only.
situation was in case of a,b-unsaturated aldehydes 9a, 9b.
The structures 9a and 9b have shown the largest Stokes' shifts
up to 90 nm in n-hexane and up to 150 nm in the diethylene glycol
(Fig. 4) in comparison with initial tertiary alcohols 5a, 5b.
It is well-known the heavy heteroatoms, including sulfur, in
aromatic structure decrease the quantum yields and fluorescence
lifetimes [76], due to the quenching effect. Therefore the 2,20-
bithiophene molecule per se has very low fluorescence signal and
quantum yield (<1%) [77]. We measured quantum yields of alde-
hydes 9a, 9b, 11ce11e and nitriles 13a, 13b and 15ce15e in ethanol
to find the structure influence.
It is found the quantum yields have larger values for 5,5'-
disubstituted bithiophenes containing formyl group 11ce11d
and
a,b-unsaturated aldehyde 9a in contrast with cyclopentene
carbaldehyde 9b (Table 1). The fact that aldehyde 9a has more
efficient electron charge transfer due to rigid and planar struc-
ture is demonstrated by the moderate quantum yield value in
comparison with 9b. Although compounds 9a and 9b have
small structural difference such as an additional methylene
group in the alicyclic unit the possible explanation of low
quantum yield for 9b can be attributed to non-planar geometry
of the molecule [75,78]. The presence of an extra methylene
group in the olefin fragment of 5-monosubstituted bithiophene
9b provides greater conformation flexibility that may cause loss
of energy by external or internal process [75] and decrease
quantum yield.
Nevertheless, the bathochromic shift (up to 50 nm) was found in
the fluorescence spectra of compound 7e in comparison with 5e
(Table 1). Perhaps, thepresenceofphenylmoietyinalicyclicfragment
has greater influence in the more conjugate and rigid cycloalkenyl
structure 7e (Table 1). The influence of structures on the emission
maxima are represented for compounds 5a, 9a and 13a (Fig. 1).
The highest quantum yield value was found for 5-bithiophene
carbaldehyde 11d, therefore the structure has substituents at 5
and 50 positions that may stabilize the exited state of the molecule
and lower energy gap for electron transition. The presence of
Scheme 3. The synthesis of nitriles 12a, 12b, 13a, 13d, 14ce14e, 15ce15e.

442
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
Table 1
Table 2
UVevisible and fluorescence data of tertiary alcohols and cycloalkenes.
UVevisible and fluorescent data of aldehydes and nitriles.
Compound
Solventa
labs (nm)
lg
3
lem (nm)
nss (nm)
Compound Solventa lem (nm) nss, nm Qfb
labs (nm) lg
3
(rel)
5a
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
CH3CN
Pyridine
Ethanol
Diethylene glycol
n-Hexane
THF
308
311
309
316
310
314
341
344
343
348
342
347
308
312
309
315
309
317
341
341
341
345
341
345
307
313
309
314
309
311
341
345
342
348
341
347
341
341
342
345
344
345
341
341
341
343
336
341
341
342
341
347
341
346
3.91
4.02
4.15
4.13
4.05
4.07
4.32
4.31
4.34
4.30
4.25
4.21
4.12
4.12
4.18
4.13
4.17
4.09
4.48
3.95
4.24
4.21
4.32
4.35
4.15
4.14
3.49
4.12
4.19
4.17
4.28
4.32
4.36
4.33
4.31
4.31
4.02
4.07
4.03
4.15
4.11
4.09
4.29
4.24
4.29
4.27
4.24
4.28
4.28
4.32
4.43
4.31
4.15
4.27
465
470
460
468
415
465
410
414
412
419
416
418
465
458
466
475
465
447
408
412
405
416
406
414
464
471
468
385
460
384
410
413
412
418
408
416
411
423
415
423
445
446
408
412
404
417
411
414
409
412
411
417
411
412
157
159
151
152
66
151
69
70
69
71
74
71
157
146
157
160
156
130
67
71
64
71
65
9a
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 384
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 377
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 389
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 394
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 389
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 371
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 367
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 366
EtOH
380
388
387
395
4.34 464
4.34 470
4.32 493
4.34 495
4.33 526
4.34 516
4.29 456
4.27 479
4.25 493
4.25 494
4.24 527
4.30 514
4.39 444
4.27 467
4.31 485
4.31 483
4.30 508
4.34 498
4.47 445
4.43 467
4.41 482
4.39 483
4.36 508
4.20 500
4.32 443
4.37 466
4.40 483
4.38 481
4.16 506
4.37 498
4.41 433
4.44 447
4.37 451
4.39 456
4.38 462
4.40 454
4.45 428
4.38 441
4.40 445
4.35 450
4.27 455
4.39 443
4.38 427
4.23 441
4.06 448
4.27 448
4.31 449
4.30 436
4.27 427
4.27 443
4.28 448
4.26 452
4.27 451
4.35 443
4.46 427
4.42 442
4.44 448
4.38 452
4.36 452
4.43 444
84
82
106
100
142
120
90
102
119
109
150
128
63
82
127
91
119
109
63
80
95
88
114
110
63
81
98
396
366
377
374
385
0.32
5b
5c
5d
5e
7b
7c
7d
7e
9b
386
381
385
358
392
0.02
0.31
0.43
0.29
0.18
0.04
0.06
0.03
0.06
11c
11d
11e
13a
13b
15c
15d
15e
389
382
387
387
395
69
390
380
385
385
393
157
158
159
76
151
73
69
68
70
70
66
69
70
82
73
78
101
101
67
71
63
74
75
73
68
70
70
88
117
109
72
81
87
84
91
87
68
77
83
82
88
77
61
75
82
79
83
70
71
86
93
89
85
85
61
75
82
79
80
78
389
361
366
364
372
367
360
364
362
368
366
366
366
366
369
366
356
357
355
363
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 366
EtOH
n-Hexane
THF
CH3CN
Pyridine
Diethylene glycol 372
EtOH 366
CH3CN
Pyridine
Ethanol
70
70
66
Diethylene glycol
358
366
367
366
373
a
The absorption and fluorescence spectra of compounds were measured on a
range of known concentrations (C ¼ 10ꢁ6e10ꢁ5 M).
additional bulky phenyl ring at the structure 11e reduces quantum
yield on 14% in comparison with 11d.
a
The absorption and fluorescence spectra of compounds were measured on a
range of known concentrations (C ¼ 10ꢁ6e10ꢁ5 M).
However, the cyano group is an effective electron-withdrawing
group the values of Stokes’ shifts, fluorescence and absorption in-
tensity and quantum yields of nitriles 13a, 13b, 15ce15e are
significantly less than the same parameters for corresponding al-
dehydes 9a, 9b, 11ce11e (Table 1). The nitriles 13a, 13b, 15ce15e
showed moderate Stokes shifts in emission spectra in all solvents
and any notable solvent molecular interaction of compounds 13a,
13b, 15ce15e with solvents was not mentioned.
b
The relative fluorescence quantum yields (Qf (rel)) were determined using the
quinine sulfate (1 ꢂ 10ꢁ5 M) in 0.1 M H2SO4 as the standard (Qf ¼ 0.546 [47]).
solvents (THF, CH3CN, pyridine) represent the group of hydrogen-
bond acceptors except n-hexane, ethanol and diethylene glycol
are classified as amphiprotic hydrogen bond acceptor-donor sol-
vents [51,52]. The increase of Kamlet
p*-values for solvent, which
The dependence between non-linear optical properties of
compounds and their structure can be successfully predicted ac-
cording to
depend on their polarity and polarizability, results the consistent
increase in bathochromic shifts of fluorescence maxima for all 2,20-
bithiophene structures.
p
*-values by Kamlet et al. for solvents.25a,b The used

V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
443
Fig. 1. Absorption (dot) and emission (plain) spectra 5a (dark blue), 9a (red), 13a
(green) in ethanol. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)
Fig. 3. Emission spectra 9a (blue, left cell) and 9b (purple, right cell) in diethylene
glycol. (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
The consistent increase in the Kamlet
gradual increase in the Stokes shifts. The dependence of Kamlet
p
*-values would lead to a
The Lippert equation describes non-specific interaction of
fluorescent molecule in aprotic solvents. The orientation polariz-
p*-
values for solvents with Stokes shifts for aldehydes 9a, 9b, 11ce11e
shows the main path according to the statement (Fig. 5, 6), however
we mentioned the greater values of Stokes shifts for compounds 9a
and 9b in all solvents (Fig. 5) in contrast with compounds 11ce11e
(Fig. 6). Moreover, the Stokes shifts observed for aldehydes 9a, 9b
and 11ce11e in ethanol and diethylene glycol did not fit the linear
relation and plots were based only on points measured in n-hexane,
THF, CH3CN and pyridine (Figs. 5 and 6). The possible explanation
for the results observed in ethanol and diethylene glycol is strong
hydrogen-bond interaction in the excited state of the molecules
ability (DG), which consists two parameters the dielectric constant
of solvent and refraction index, may be used for estimation of in-
fluence of solvent polarity on Stokes shift [78,79].
Therefore, to evaluate the influence of solvent polarity on the
fluorophore sensitivity we plotted the graph with Stokes shift and
orientation polarizability (Figs. 7 and 8). The increase in orientation
polarizability facilitates the bathochromic shift in the emission
spectra of all compounds. The consistent increase in solvent po-
larity leads to the significant bathochromic shift for all aldehydes
9a, 9b, 11c-11d and probably is due to the greater change in the
dipole moment of excited molecules. Moreover, ethanol and
diethylene glycol may cause a specific solvent interaction, and may
form hydrogen bonds with formyl group in the excited state of
aldehydes, thus facilitate the increase in bathochromic shift
(Table 2, Figs. 7 and 8). However, the points for the aldehydes 9a, 9b
in diethylene glycol did not fit the Lippert plot, and may be referred
to the very strong influence of hydrogen-bond formation with
molecule in the excited state (Fig. 7).
(9a, 9b, 11ce11e). The Kamlet
p*-values consider the polarity and
polarizability parameters for solvents; however the relation of
these parameters on the fluorescence maxima were presented in
the Lippert equation [78,79].
Fig. 2. Emission spectra 5d (blue), 11d (green) and 15d (crimson) in ethanol. (For
interpretation of the references to colour in this figure legend, the reader is referred to
the web version of this article.)
Fig. 4. Emission spectra 9a (blue), 9b (orange), 11c (magenta), 11d (green), 11e (dark
blue) in ethanol. (For interpretation of the references to colour in this figure legend, the
reader is referred to the web version of this article.)

444
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
Fig. 5. The relationship between
p*-values of Kamlet and Stokes shift of 9a, 9b.
Fig. 8. Lippert plot for aldehydes 11ce11e.
The dependence of solvent orientation polarizability and Stokes
shift shows the consistent pattern in the Lipperts’ plot (Figs. 7 and
8), so the increase in orientation polarizaility results on stabiliza-
tion the main and exited states of the molecule. However, for
compounds 9a and 9b in THF we observed the smallest value of
Stokes shift, so this fact may suggest about very slight solvent effect
on the fluorophore molecules in the exited state (Figs. 5 and 7).
Although acetonitrile is non-hydrogen-bonding solvent, we
observed the large values of Stokes shifts for aldehydes 9a, 9b, 11c-
11e (comparable with Stokes shifts in ethanol) probably, due to the
nonspecific solvation (Figs. 7 and 8). Perhaps, the decrease in red-
shift for 9a and 9b in THF may be explained by some interaction
of compounds with solvent.
4. Conclusions
It was found the tertiary alcohols (4a-4c, 4e, 5a-5e) prepared via
Grignard reaction undergo dehydration process easily, although
mild reaction conditions were used. The VilsmeiereHaack reaction
pathway depends on the alicyclic ring size. Therefore, we obtained
Fig. 6. The relationship between
p*-values of Kamlet and Stokes shift of 11ce11e.
only a,b-unsaturated aldehydes with C4eC5 (9a, 9b) and in cyclo-
hexane derivatives we observed two isomers: the formylation in
thiophene ring and formylation in the olefin double bond.
The absorbance, fluorescence spectra and quantum yields were
measured in several solvents. In common, the increase of Kamlet
et al.
p*-values for solvents is consistent with bathochromic shift
(15e30 nm) as in absorbance and so emission spectra. The Lipperts’
plot of orientation polarizability and Stokes shift was found for
aldehydes 9a, 9b, 11c-11e. Significant bathochromic shifts for al-
dehydes due to the possible hydrogen-bond formation in the
ethanol and diethylene glycol. The future work will be focused on
the synthesis and solvatochromic study of thiophenes and 2,20-
bithiophenes with bulky alicyclic moieties.
Acknowledgments
This work was financially supported by the Russian Ministry of
Education and Science within basic part of government assignment
for scientific research (2014/199-1078) with use of equipment of
Multiple-Access Center ‘Investigation of the physicochemical
properties of substances and materials’ Samara State Technical
University.
Fig. 7. Lippert plot for aldehydes 9a, 9b.

V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
445
[28] Юда
5-R-2,2'-б
erocyc Compd 1979;8:1057e61 [Russian].
[29] Yoshimura K, Matsumoto K, Uetani Y, Sakumichi S, Hayase S, Kawatsura M,
et al. Tetrahedron 2012;68:3605e10.
[30] Raposo MMM, Ferreira AMFP, Amaro M, Belsley M, Moura JCVP. The synthesis
and characterization of heterocyclic azo dyes derived from 5-N,N-dia-
lkylamino-2,2'-bithiophene couplers. Dyes Pigments 2009;83:59e65.
[31] Herbivo C, Comel A, Kirsch A, Fonseca AMC, Belsley M, Raposo MMM. Syn-
thesis and characterization of novel, thermally stable 2-aryl-5-
dicyanovinylthiophenes and 5-aryl-5'-dicyanovinyl-2,2'-bithiophenes as
potentially promising non-linear optical materials. Dyes Pigments 2010;86:
217e26.
ш
к
и
н АВ, Лип
к
и
н АЕ, Зво
л
и
нский ВИ, Захаров
В
Ф
, Игнатов . Н
В
Ф
итрование
References
и
т
иофенов, с
одерЖащих электр
он
од
он
орные заМест
и
тели. Chem Het-
[1] Tao T, Qian H-F, Zhang K, Geng J, Huang W. Functionalized oligothiophene-
based heterocyclic aromatic fluorescent compounds with various
donoreacceptor spacers and adjustable electronic properties: a theoretical
and experimental perspective. Tetrahedron 2013;69:7290e9.
[2] Kanaparthi RK, Kandhadi J, Giribabu L. Metal-free organic dyes for dye-
sensitized solar cells: recent advances. Tetrahedron 2012;68:8383e93.
[3] Dong Y, Bolduc A, McGregor N, Skene WG. Push-Pull aminobithiophenes e
highly fluorescent stable fluorophores. Org Lett 2011;13:1844e7.
[4] Herbivo C, Comel A, Kirsch G, Raposo MMM. Synthesis of 5-aryl-50-formyl-
2,20-bithiophenes as new precursors for nonlinear optical (NLO) materials.
Tetrahedron 2009;65:2079e86.
[32] Gupta A, Ali A, Singh TB, Bilic A, Bach U, Evans RA. Molecular engineering for
[5] Batista RMF, Costa SPG, Belsley M, Lodeiro C, Raposo MMM. Synthesis and
characterization of novel (oligo)thienyl-imidazo-phenanthrolines as versatile
panchromatic absorbing oligothiophene donor-p-acceptor organic semi-
conductors. Tetrahedron 2012;68:9440e7.
[33] Shellaiaha M, Fang H-P, Lin Y-L, Hsu Y-C, Lin J-T, Lin H-C. Synthesis of metal-
free organic dyes containing tris(dodecyloxy)phenyl and dithienothiophenyl
units and a study of their mesomorphic and photovoltaic properties. Tetra-
hedron 2013;69:2124e30.
p-conjugated systems for several optical applications. Tetrahedron 2008;64:
9230e8.
[6] Xu M-H, Pu L. Novel unsymmetrically hyperbranched polythiophenes with
conjugation gradient. Tetrahedron Lett 2002;43:6347e50.
[7] Sakamoto K, Takashima Y, Hamada N, Ichida H, Yamaguchi H, Yamamoto H,
et al. Selective photoinduced energy transfer from a thiophene rotaxane to
acceptor. Org Lett 2011;13:672e5.
[34] Effenberger H, Wurthner F, Steybe F. Synthesis and solvatochromic properties
of donor-acceptor-substituted oligothiophenes.
2082e91.
J Org Chem 1995;60:
[8] Zhao J, Jin T, Islam A, Kwon E, Akhtaruzzaman Md, Asao N, et al. Thieno[2,3-a]
[35] Higuchi H, Koyama H, Yokota H, Ojima J. Solvent effect on the bathochromic
shifts of push-pull dihexylbithiophenes with head-to-head and head-to-tail
orientations. Tetrahedron Lett 1996;37:1617e20.
[36] Dedier D, Sergeyev S, Geerts YH. Non-symmetrical oligothiophenes with
‘incompatible’substituents. Tetrahedron 2007;63:941e6.
[37] Darmanin T, Taffin de Givenchy E, Amigony S, Guittard F. Synthesis, charac-
terization and surface wettability of polythiophene derivatives containing
semi-fluorinated liquid-crystalline segment. J Fluor Chem 2012;134:85e9.
[38] Szczucinski T, Dabrowski R. A convenient synthesis of 4-(trans-4'- n-alkylcy-
clohexyl) benzoic acids. Mol Cryst Liq Cryst 1982;88:55e64.
[39] Inukai T, inventor; Inoue H, inventor; Sato H, inventor. Chisso Corporation,
assignee. Liquid crystal compounds. United States patent US 4,211,666. 1980
July 8.
[40] Karamysheva LA, Kovshev EI, Pavluchenko AI, Roitman KV, Titov VV,
Torgova SI, et al. New heterocyclic liquid crystalline compounds. Mol Cryst Liq
Cryst 1981;67:241e52.
[41] Kiryanov AA, Seed AJ, Sampsom P. Ring fluorinated thiophenes: applications
to liquid crystal synthesis. Tetrahedron Lett 2001;42:8797e800.
[42] Morimoto M, Irie M. Photochromism of diarylethene derivatives having
cyclohexyl and cyclohexenyl groups in single-component crystals and a two-
component mixed crystal. Tetrahedron Lett 2009;50:3404e7.
[43] Wynberg H, Logothetis A. Studies in the synthesis of long-chain compounds.
J Am Chem Soc 1956;78:1958e61.
[44] Wu R, Schumm JS, Pearson DL, Tour JM. Convergent synthetic routes to
orthogonally fused conjugated oligomers directed toward molecular scale
electronic device applications. J Org Chem 1996;61:6906e21.
[45] Curtis RF, Phillips GT. The synthesis of monohalogeno-2,20-bithienyls. J Chem
Soc 1965;950:5134e7.
[46] Gordon AJ, Ford RA. Chemist's companion e a handbook of practical data,
techniques, and references. New York: John Wiley & Sons; 1972.
[47] Melhuish WH. Quantum efficiencies of fluorescence of organic substances:
effect of solvent and concentration of the fluorescent solute. J Phys Chem
1961;65:229e35.
carbazole-based donor-p-acceptor organic dyes for efficient dye-sensitized
solar cells. Tetrahedron 2014;70:6211e6.
[9] Ying JY, Chen CY, Lee CP, Chen SC, Lin TH, Tsai HH, et al. Unsymmetrical
squaraines incorporating the thiophene unit for panchromatic dye-sensitized
solar cells. Org Lett 2010;12:5454e7.
[10] Ikemoto N, Estevez I, Nakanishi K, Berova N. Fluorescent bithiophene chro-
mophores: synthesis and application in CD exciton chirality studies. Hetero-
cycles 1997;46:489e501.
[11] Amro K, Daniel J, Clermont G, Bsaibess T, Pucheault M, Genin E, et al. A new
route towards fluorescent organic nanoparticles with red-shifted emission
and increased colloidal stability. Tetrahedron 2014;70:1903e9.
[12] Wang H, Wang J-L, Yuan S-C, Pei J, Pei W-W. Novel highly fluorescent den-
dritic chiral amines: synthesis and optical properties. Tetrahedron 2005;61:
8465e74.
[13] Cui M, Li Z, Tang R, Jia H, Liu B. Novel (E)-5-styryl-2,2'-bithiophene derivatives
as ligands for b-amyloid plaques. Eur J Med Chem 2011;46:2908e16.
[14] Vollmer MS, Effenberger F, Stumpfig T, Hartschuh A, Port H, Wolf HC. Steroid-
bridged anthryloligothienylporphyrins: synthesis and study on the intra-
molecular energy transfer. J Org Chem 1998;63:5080e7.
[15] Lee W, Yang Y, Cho N, Ko J, Hong J-I. Functionalized organic dyes containing a
phenanthroimidazole donor for dye-sensitized solar cell applications. Tetra-
hedron 2012;68:5590e8.
[16] Wang C, Liang M, Huang J, Cheng F, Wang H, Guo Y, et al. Redox couple related
influences of bulky electron donor as well as spacer in organic dye-sensitized
mesoscopic solar cells. Tetrahedron 2014;70:6203e10.
[17] Pati PB, Zade SS. New panchromatic dyes comprising benzothiadiazole units
within a donor-acceptor
properties. Tetrahedron 2013;69:2167e74.
p-conjugated spacer. Synthesis and photophysical
[18] Robitaille L, Leclerc M, Callender CL. Poly[3-(alkoxyphenyl)thiophenes]: syn-
thesis and linear and nonlinear optical properties. Chem Mater 1993;5:
1755e61.
[19] Khunchalee J, Tarsang R, Prachumrak N, Jungsuttiwong S, Keawin T,
Sudyoadsuk T, et al. Synthesis and properties of oligofluorene-thiophenes as
emissive materials for organic electroluminescent devices: color-tuning from
deep blue to orange. Tetrahedron 2012;68:8416e23.
[20] Cho N, Kim J, Song K, Lee JK, Ko J. Synthesis and characterization of push-pull
organic semiconductors with various acceptors for solution-processed small
molecule organic solar cells. Tetrahedron 2012;68:4029e36.
[21] Lia WJ, Wu H-M, Li Y-B, Hu C-P, Yi M-D, Xie L-H, et al. Facile synthesis and
self-assembly of diazafluorenone-based p-n(donor-acceptor) organic semi-
conductors. Tetrahedron 2012;68:8216e21.
[22] Vollmer MS, Effenberger F, Stecher R, Gomph B, Eisenmenger W. Steroid-
bridged thiophenes: synthesis and self-organization at the solid/liquid
interface. Chem Eur J 1999;5:96e101.
[23] Fin A, Jentzsch AV, Sakai N, Matile S. Oligothiophene amphiphiles as planar-
izable and polarizable fluorescent membrane probes. Angew Chem Int Ed
2012;51:12736e9.
[24] Gupta A, Armel V, Xiang W, Fanchini G, Watkins SE, MacFarlane DR, et al. The
effect of direct amine substituted push-pull oligothiophene chromophores on
dye-sensitized and bulk heterojunction solar cells performance. Tetrahedron
2013;69:3584e92.
[25] Raposo MMM, Kirsch G. Formylation, dicyanovinylation and tricyanovinyla-
tion of 5-alkoxy- and 5-amino-substituted 2,2'-bithiophenes. Tetrahedron
2003;59:4891e9.
[26] Raposo MMM, Fonseca AM, Kirsch G. Synthesis of donor-acceptor substituted
oligothiophenes by Stille coupling. Tetrahedron 2004;60:4071e8.
[27] Raposo MMM, Sousa AMRC, Kirsch G, Cardoso P, Belsley M, de Matos
Gomes E. Synthesis and characterization of dicyanovinyl-substituted thie-
nylpyrroles as new nonlinear optical chromophores. Org Lett 2006;8:
3681e4.
[48] Fery-Forgues S, Lavabre D. Are fluorescence quantum yields so tricky to
measure? A demonstration using familiar stationery products. J Chem Educ
1999;76:1260e4.
[49] Lacowicz JR. Principles of fluorescent spectroscopy. New York: Kluwer Aca-
demic/Plenum Publishers; 1999. p. 185e207.
[50] Mataga N, Kaifu Y, Koizumi M. Solvent effects upon fluorescence spectra and
the dipole moments of excited molecules. Bull Chem Soc Jpn 1956;29:
465e70.
[51] Kamlet MJ, Abboud JL, Taft RW. The solvatochromic comparison method. 6.
The
p* scale of solvent polarities. J Am Chem Soc 1977;99:6027e38.
[52] Taft RW, Kamlet MJ. The solvatochromic comparison method. 2. The
a
-scale of
solvent hydrogen-bond donor (HBD) acidities.
2886e94.
[53] Meshkovaya VV, Yudashkin AV, Bushueva PY, Eremeeva NB, Klimochkin YN.
Synthesis and fluorescent properties of novel chiral 1,2-diaminocyclohexane
substituted ligands and their complexes. Tetrahedron 2014;70:3211e7.
J Am Chem Soc 1976;98:
[54] Meshkovaya VV, Yudashkin AV, Klimochkin YN. ФорМ
илирование 5-(1-
ги
др ксицикл алк л)- 5-(цикл алк-1-ен-1- л)-2,2'-б иофенов. [Formylation
о
о
и
и
о
и
ит
of 5-(1-hydroxycycloalkyl)- and 5-(cycloalk-1-ene-1-yl)-2,2'-bithiophenes].
Russ J Org Chem 2012;48:1517e8 [Russian].
[55]
М
е
ш
к
овая ВВ, inventor; Юда
Samara State Technical University, assignee.
цикл ческ х спиртов ряда 2,2'-б иофена. [A method for synthesis of tertiary
ш
к
и
н АВ, inventor; Кл
и
о
М
б
о
чк
и
н ЮН; inventor.
С
по
с
получен
ия
трет чных
и
и
и
ит
alcohols in 2,2'-bithiophene series]. Russian Federation patent. RU 2495018.
2013 October 10.
[56] Johnson AL. Synthesis of the three isomeric ortho-substituted phenylthienyl
benzoic acids. J Org Chem 1976;41:1320e4.

446
V.V. Meshkovaya et al. / Dyes and Pigments 113 (2015) 435e446
[57] Nakayama J, Fujimiri T. 1,6-Bis(5,20:50,200-terthiophene-2-yl)spiro[4.4]nona-
1,6-diene: a molecule having two orthogonally bisected -terthiophene sys-
[68] Wei Y, Yang Y, Yeh JM. Synthesis and electronic properties of aldehyde end-
a
capped thiophene oligomers and other a,u-substituted sexithiophenes.
tems through a spiro carbon. J Chem Soc Chem Comm 1991;22:1614e5.
[58] He XS, Raymon LP, Mattson MV, Eldefrawi ME, de Costa BR. Synthesis and
biological evaluation of 1-[1-(2-benzo[b]thienyl)cyclohexyl]piperidine ho-
Chem Mater 1996;8:2659e66.
[69] Lescot E jun, Buu-Hoi NP, Xuong ND. Thiophene derivatives. Part XIV. Some
problems of substitution in the 2,20-bithienyl series. J Chem Soc 1959:3234e7.
[70] Katritzki AR, Shcherbakova IV, Tack RD, Steel PJ. Reactions of unactivated
olefins with Vilsmeier reagents. Can J Chem 1992;70:2040e5.
mologs at dopamine-uptake and phencyclidine-, and
s-binding sites. J Med
Chem 1993;36:1188e93.
[59] Lara M, Mutti FG, Glueck SM, Kroutil W. Biocatalytic cleavage of alkenes with
O2 and Trametes hirsuta G FCC 047. Eur J Org Chem 2008;21:3668e72.
[60] Brown HC, Gupta AK, Prasad JVNV. Chiral synthesis via organoboranes. 11.
Hydroboration. 82. Asymmetric hydroboration of 1-heteroarylcycloalkenes
with monoisopinocampheylborane. Synthesis of trans-2-heteroarylcycloalkyl
boronates and derived alcohols of very high enantiomeric purity. Bull Chem
Soc Jpn 1988;61:93e100.
[71] Schmidle CJ, Barnett PG. The preparation of cinnamaldehydes by the for-
mylation of styrenes. J Am Chem Soc 1956;78:3209e10.
[72] Barclay TM, Cordes AW, MacKinnon CD, Oakley RT, Reed RW. Oligothiophenes
end-capped by nitriles. Preparation and crystal structures of a,u-dicyanooli-
gothiophenes NC(C4H2S)nCN (n ¼ 3-6). Chem Mater 1997;9:981e90.
[73] Melucci M, Barbarella G, Zambianchi M, Di Pietro P, Bongini A. Solution-phase
microwave-assisted synthesis of unsubstituted and modified
sexithiophenes. J Org Chem 2004;69:4821e8.
a-quinque- and
[61] Kuroda M, Nakayama J, Hoshino M, Furusho N, Kawata T, Ohba S. Synthesis
and properties of 1,8-Di(2-thienyl)-, 1,8-bis(5,2'-bithiophene-2-yl)-, 1,8-
[74] Zotti G, Zecchin S, Vercelli B, Berlin A, Casado J, Hernandez V, et al. Magnetic
and conductive properties of quinoidal oligothiophenes. Chem Mater
2006;18:1539e45.
[75] Berlman IB. Handbook of fluorescence spectra of aromatic molecules. New
York: Academic Press; 1971. p. 47e66.
[76] Nijegorodov N, Mabbs R. The influence of molecular symmetry and topolog-
ical factors on the internal heavy atom effect in aromatic and heteroaromatic
compounds. Spectrochim Acta Part A: Mol Biomol Spectrosc 2001;57:
1449e62.
[77] Curtis RF, Phillips GT. The absorption spectra and synthesis of some 2,2'-
bithienyl derivatives. Tetrahedron 1967;23:4419e24.
bis(5,2':5',2'-terthiophene-2-yl)-,
and
1,8-bis(5,2':5',2':5',200-quaterthio-
phene-2-yl)naphthalenes and related compounds. Tetrahedron 1993;49:
3735e48.
[62] Brown D, Craig JC, Dyson NH, Westley JW. Synthesis of 5-(but-3-en-1-ynyl)-
2,20-bithienyl and related compounds by Grignard coupling. J Chem Soc C
1966:89e91.
[63] Fieser LF, Szmuszkovicz J. Synthesis of keto acids by chromic anhydride
oxidation of tertiary alcohols. J Am Chem Soc 1948;70:3352e5.
[64] Kosak AI, Palchak RJF, Steele WA, Selwitz CM. The synthesis and properties of
the 5-phenyl-2- and 3-thiophene-ols. J Am Chem Soc 1954;76:4450e4.
[65] Wiberg KB. The concept of strain in organic chemistry. Angew Chem Int Ed
Engl 1986;25:312e22.
[78] Taber RL, Daub GH, Hayes FN, Ott DG. Liquid scintillators. XIII. steric inhibition
of resonance in liquid scintillators. J Het Chem 1965;2:181e7.
[79] Lippert E. Spektroskopische Bestimmung des Dipolmomentes aromatischer
[66] Bach RD, Dmitrenko O. Strain energy of small ring hydrocarbons. Influence of
C-H bond dissociation energies. J Am Chem Soc 2004;126:4444e52.
[67] Weston AW, Michaels RJ. 2-Thenaldehyde. Org Synth 1951;31:108.
Verbindungen im ersten angeregten Singulettzustand.
Z für Elektrochem
1957;61:962e9 [German].