Ferrocenyl substituted triphenylamine based donor-acceptor molecular systems; Synthesis, photophysical, electrochemical, and theoretical studies

Article abstract of DOI:10.1016/j.tet.2014.03.096

A series of push-pull molecular systems 5-14 were designed, and synthesized by the Sonogashira cross-coupling, Knoevenagel condensation, and cycloaddition reactions. The donor 'ferrocenyl substituted triphenylamine' was kept constant, whereas the acceptors were varied (malononitrile, indanone, and tetralone). The electronic absorption spectra of the ferrocenyl substituted triphenylamine based donor-acceptor (D-A) compounds 5-9 exhibit intense intramolecular charge transfer (ICT) band in the visible region (415-502 nm). The incorporation of the tetracyanoethylene (TCNE) group in compounds 5-9 results in new D-A system 10-14, which exhibits the ICT band in the region 630-700 nm. The electrochemical studies suggest considerable donor-acceptor interaction. The computational studies reveal strong D-A interaction, and show good agreement with the experimental results.

Full text of DOI:10.1016/j.tet.2014.03.096

Tetrahedron 70 (2014) 3390e3399
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Ferrocenyl substituted triphenylamine based donoreacceptor
molecular systems; synthesis, photophysical, electrochemical, and
theoretical studies
*
Ramesh Maragani, Rajneesh Misra
Department of Chemistry, Indian Institute of Technology Indore, Indore 452 017, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of pushepull molecular systems 5e14 were designed, and synthesized by the Sonogashira cross-
coupling, Knoevenagel condensation, and cycloaddition reactions. The donor ‘ferrocenyl substituted
triphenylamine’ was kept constant, whereas the acceptors were varied (malononitrile, indanone, and
tetralone). The electronic absorption spectra of the ferrocenyl substituted triphenylamine based do-
noreacceptor (DeA) compounds 5e9 exhibit intense intramolecular charge transfer (ICT) band in the
visible region (415e502 nm). The incorporation of the tetracyanoethylene (TCNE) group in compounds
5e9 results in new DeA system 10e14, which exhibits the ICT band in the region 630e700 nm. The
electrochemical studies suggest considerable donoreacceptor interaction. The computational studies
reveal strong DeA interaction, and show good agreement with the experimental results.
Ó 2014 Elsevier Ltd. All rights reserved.
Received 10 February 2014
Received in revised form 27 March 2014
Accepted 28 March 2014
Available online 3 April 2014
1. Introduction
computational properties of the ferrocenyl substituted triphenyl-
amine based donor connected to the acceptors; malononitrile (a),
There has been increasing interest in the design, and synthesis
of pushepull molecular systems because of their applications in
nonlinear optics (NLO), and organic photovoltaics (OPV).1,2 In
pushepull systems the electron donating group is attached to the
indan-1,3-dione (b), 1-indanone (c), 1-tetralone (d), tetracyano-
ethylene (e).
2. Results and discussion
electron accepting group via
photonic properties of the pushepull systems can be tuned by
varying the strength of donor/acceptor groups, and the
-spacer.3
Our group is interested in the design, and synthesis of
pushepull systems for variety of applications.4 We have explored
ferrocene as a strong electron donor.5 The triphenylamine (TPA)
moiety is also a strong electron donor.6 Therefore attaching the
ferrocene unit on the periphery of the triphenylamine will increase
its donor strength.
Francois Diederich has explored tetracyanoethylene (TCNE), as
a strong electron acceptor.7 TCNE undergo rapid [2þ2] cycloaddi-
tion followed by electrocyclic ring opening with electron donating
acetylenes, and exhibit intramolecular charge transfer.8
Triphenylamine based donoreacceptor systems have been
widely studied for organic photovoltaic devices. To the best of our
knowledge, there are no reports, where ethynyl ferrocene
substituted triphenylamine is attached with the acceptor. In this
article we report synthesis, photophysical, electrochemical, and
p-conjugated spacer (DepeA). The
The ferrocenyl substituted triphenylamine based donoreacceptor
molecular systems 5e14 (Chart 1), were designed, and synthesized
by the Pd-catalyzed Sonogashira cross-coupling, Knoevenagel con-
densation, and cycloaddition reactions.
The triphenylamine based intermediate 2 was synthesized by
the VilsmeiereHaack formylation reaction of triphenylamine 1.9
The monoformylation reaction selectively occurred at the para-
position of the phenyl ring, which resulted 4-(diphenylamino)-
benzaldehyde 2 in 80% yield. The iodination reaction of 2 in the
presence of potassium iodide (KI), potassium iodate (KIO3), and
acetic acid as a solvent resulted 4-(bis(4-iodophenyl)amino)-
benzaldehyde 3 in 85% yield (Scheme 1).10
The Pd-catalyzed Sonogashira cross-coupling reaction of 3 (4-
(bis-(4-iodophenyl)-amino]-benzaldehyde) with ethynyl ferrocene
resulted mono substituted 4, and di-substituted ferrocenyl triphe-
nylamine aldehyde 5 in 20% and 65% yields, respectively (Scheme 2).
The ferrocenyl substituted triphenylamine based donoreacceptor
compounds 6e9 were synthesized by the Knoevenagel condensation
reaction of compound 5, with the corresponding active methylene
compounds; malononitrile (a), indan-1,3-dione (b), 1-indanone (c),
p
* Corresponding author. Tel.: þ91 7312438710; fax: þ91 7312361482; e-mail
address: rajneeshmisra@iiti.ac.in (R. Misra).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.03.096

R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
3391
Fe
Fe
Fe
N
N
O
N
CN
O
CN
6
7
O
5
Fe
Fe
Fe
Fe
NC
Fe
NC
CN
CN
Fe
O
O
H
H
N
N
N
CN
NC
Fe
O
8
9
CN
10
NC
Fe
Fe
Fe
Fe
NC
NC
NC
NC
CN
CN
CN
CN
N
O
CN
N
NC
Fe
CN
CN
CN
NC
Fe
O
CN
Fe
12
CN
NC
NC
11
Fe
CN
CN
CN
O
CN
O
NC
NC
NC
NC
H
H
N
N
CN
CN
CN
CN
NC
NC
NC
NC
Fe
Fe
13
14
Chart 1. Molecular structures of the ferrocenyl substituted triphenylamine based donoreacceptor compounds 5e14.
I
KI, KIO3
DMF
90 oC, 5 hr
N
N
N
Acetic acid
100oC, 16 h
O
O
2
1
I
3
Scheme 1. Synthesis of compounds 2e3.
1-tetralone (d). The Knoevenagel condensation reaction of com-
pound 5, with malononitrile (a), and indan-1,3-dione (b) in
dichloromethane, and NH4OAC as a base in microwave at 65 ꢀC
ferrocenyl substituted triphenylamine based donoreacceptor com-
pounds 8 and 9 in 75% and 70% yields, respectively. The [2þ2] cy-
cloaddition reaction of donoreacceptor compounds 5e9
with tetracyanoethylene (TCNE) at 75 ꢀC, in dichloromethane
solvent in microwave resulted compounds 10e14 in 60e72% yield
(Scheme 3).
resulted
6 and 7 in 85% and 80% yields, respectively. The
condensation reaction of 5 with 1-indanone (c), and 1-tetralone (d)
in ethanol and THF (3:1) as solvent under basic condition resulted,

3392
R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
Fe
Fe
I
Fe
N
O
N
N
Pd(PPh3)4
, Et3N
THF
16 h, 60 oC
O
I
I
5
3
4
(Major)
O
Fe
(Minor)
Scheme 2. Synthesis of aldehydes 4 and 5.
Fe
Fe
NC
NC
CN
CN
NC
CN
(a)
DCM, NH4OAc,
65 oC, 3 h
Microwave
CN
CN
CN
N
NC
CN
CN
CN
Fe
NC
6
11
Fe
Fe
Fe
O
Fe
NC
NC
CN
O
CN
(b)
O
DCM, NH4OAc,
65 oC, 3 h
Microwave
N
N
O
CN
O
NC
Fe
O
7
O
5
CN
12
Fe
Fe
NC
O
Fe
CN
CN
NC
NC
CN
CN
Fe
O
O
DCM, 75oC,
microwave,
3h
CN
CN
NC
NC
NC
NC
(c)
H
(e)
H
Ethanol, THF, NaOH,
85oC - rt, 16 h
DCM, 75oC,
microwave,
3h
(e)
N
Fe
CN
CN
NC
NC
NC
NC
8
CN
CN
13
Fe
Fe
O
Fe
CN
CN
CN
NC
Fe
O
O
O
(d)
NC
NC
H
CN
Fe
H
NC
Ethanol, THF, LiOH,
85oC - rt, 16 h
10
N
9
CN
CN
NC
NC
Fe
Fe
14
Scheme 3. Synthesis of ferrocenyl substituted triphenylamine based donoreacceptor compounds 5e14.

R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
3393
Table 1
The ferrocenyl substituted triphenylamine based donoreacceptor
Photophysical and electrochemical data of donoreacceptor compounds 5e14
compounds 5e14 were found to be stable in solid, and solution
phase. All the compounds were well characterized by UVevis ab-
sorption, 1H NMR, 13C NMR, and HRMS techniques. The typical 1H
NMR spectrum of the donoreacceptor compounds 6e9 show fol-
lowing types of signals; (a) the unsubstituted cyclopentadienyl ring
of the ferrocene exhibits a sharp singlet around 4.19e4.25 ppm, (b)
the mono substituted cyclopentadienyl ring of ferrocene exhibit
triplet at of 4.50 ppm, (c) the olefinic proton appears as singlet in the
region 7.54e8.15 ppm.
Compound lmax
3 ) Eoxid Ered Optical band Theoretical
d (Mꢂ1 cmꢂ1
(nm)
(V)
(V)
gape (eV)
3.01
band gapf (eV)
5
359 27,600
d
0.05a
0.80b
0.08a
0.71b
0.10a
0.81b
0.07a
0.67b
0.06a
0.76b
d
3.42
2.72
2.70
2.80
2.88
2.76
2.74
2.73
2.67
2.61
d
6
349 8100
459
d
d
d
d
2.26
2.12
2.54
2.61
7
502 13,866
8
364 8700
The 1H NMR spectrum of the donoreacceptor compounds
10e14 shows five different types of signals; (a) the unsubstituted
cyclopentadienyl ring of ferrocene exhibits a multiplet around
4.43e4.46 ppm, and triplet in the region of 4.87e4.89 ppm, (b) the
mono substituted cyclopentadienyl ring exhibits triplet at
5.05 ppm, and multiplet at 5.47 ppm, (c) the olefinic proton appears
as singlet in the region 7.67e8.20 ppm.
434
9
367 10,000
415
10
11
12
13
14
485 56,666
d
0.41a 1.43c 2.21
1.11b 0.97c
469 11,066
d
0.42a 1.39c 2.25
0.99b 0.94c
488 15,733
d
0.39a 1.41c 2.11
0.98b 0.97c
499 48,500
d
0.43a 1.37c 2.11
0.93b 0.97c
3. Photophysical properties
502 7666
d
0.44a 1.39c 2.02
0.89b 0.97c
The electronic absorption spectra of the ferrocenyl substituted
triphenylamine based donoreacceptor compounds 5e14 in
dichloromethane solution are shown in Fig. 1, and the data are listed
in Table 1. The UVevis absorption spectrum of the compounds 6e9
show two types of bands. The first band in the region 349e367 nm
Ferrocene
d
d
0.00
d
d
a
The oxidation value of ferrocene unit.
b
c
d
e
f
The oxidation value of triphenylamine unit.
The reduction values of TCNE group.
Measured in dichloromethane solvent.
Optical band gap estimated from the absorption edge.
Theoretical values from DFT calculations.
corresponds to p/p transition, and the second band in the region
*
415e502 nm corresponds to intramolecular charge transfer (ICT).11
Compound 7 shows intense ICT band (lmax w502 nm), which in-
volves the transition from the ferrocenyl substituted triphenylamine
donor to the acceptor 1,3-inadanone, whereas compound 9 shows
moderate charge transfer from ferrocenyl substituted triphenyl-
amine to tetralone around 415 nm (Fig. 1a). The strength of the ICT in
compounds 6e9, follows the order 7>6>8>9.
4. Electrochemical properties
The electrochemical properties of the ferrocenyl substituted
triphenylamine based donoreacceptor compounds 5e14 were
studied by the cyclic voltammetric analysis. The electrochemical
1.0
1.0
10
5
11
6
0.8
12
13
14
0.8
7
8
9
0.6
0.6
0.4
0.2
0.0
0.4
0.2
0.0
300
400
500
600
700
800
300
400
500
600
700
800
Wavelength (nm)
Wavelength (nm)
(a)
(b)
Fig. 1. Normalized electronic absorption spectra of the ferrocenyl substituted triphenylamine based donoreacceptor compounds 5e14 in CH2Cl2 (1.0ꢁ10ꢂ4 M). (a) Compounds 5e9.
(b) Compounds 10e14.
The donoreacceptor compounds 10e14 show two types of bands,
the first high energy absorption band around 469e502 nm corre-
*
sponds to p/p transition, and the second low energy broad band
data of compounds 5e14 are listed in Table 1, and the representa-
tive cyclic voltammograms are shown in Fig. 3. The cyclic voltam-
mogram of compounds 5e9 shows two oxidation waves; (a) the
reversible wave in the region 0.05e0.1 V corresponding to the ox-
idation of ferrocene unit, (b) the quasi reversible oxidation wave in
the region 0.67e0.81 V, which belongs to the triphenylamine
unit.13 Compounds 5e9 exhibit harder oxidation compared to free
ferrocene, confirming strong electronic communication between
ferrocene unit, and different acceptors. The trend in the oxidation
potential of the ferrocenyl moiety in 5e9 follows the order
7>6>8>9>5, which reveals that the increase in the strength of
acceptor unit improves the donoreacceptor interaction.
around 630e700 nm corresponds to ICT (Fig. 1b). Compounds 5e9
show high intensity ICT band around 415e502 nm, whereas their TCNE
derivatives 10e14, show low-intensity ICT band around
630e700 nm.12 Thisrevealsthatafteraddition of the TCNE, the primary
acceptors (malononitrile, 1-indanone, 1,3-indanone, and tetralone)
losses acceptor strength in the presence of TCNE (strong acceptor)
groups, which is also evident from the computational studies and
Figure 2 displays the colors of the donoreacceptor 10e14 in
dichloromethane.

3394
R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
Fig. 2. The ferrocenyl substituted triphenylamine donoreacceptor compounds 5e14 show a prominent effect on their color pattern in dichloromethane solution 1.0ꢁ10ꢂ4 M.
6.0µ
a
30.0µ
4.0µ
d
7
20.0µ
10.0µ
0.0
2.0µ
0.0
12
b
a
c
b
-2.0µ
-4.0µ
-6.0µ
-10.0µ
-20.0µ
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Potential vs Fe/Fe+
Potential vs Fe/Fe+
(b)
(a)
Fig. 3. Cyclic voltammograms of the ferrocenyl substituted triphenylamine based donoreacceptor (a) compound 7, and (b) compound 12, at 1.0ꢁ10ꢂ4 M concentration in 0.1M
TBAPF6 in dichloromethane recorded at a scan rate of 100 mV sꢂ1
.
Compounds 10e14 exhibit harder oxidation potential com-
pared to compounds 5e9 due to increase in the number of ac-
ceptors (TCNE). The cyclic voltammogram of donoreacceptor
compounds 10e14 show two oxidation waves, and two reduction
waves. The first oxidation wave in the region 0.39e0.44 V cor-
responds to the oxidation of ferrocene unit, and the second quasi
reversible wave in the region 0.89e1.11 V, which belongs to tri-
B3LYP/6-31G** for C, H, N, O, and Lanl2DZ for Fe level.15,16 The
ferrocenyl groups were found to be planar with respected to the
phenyl ring in donoreacceptor compounds 5e9. On the other
hand the incorporation of the TCNE group results in loss of pla-
narity of ferrocenyl groups due to steric hindrance in compounds
10e14. The optimized structures of compounds 7 and 12 are
shown in Fig. 4.
Fig. 4. Geometry optimized structures of the ferrocenyl substituted triphenylamine based donoreacceptor compounds (a) 7, and (b) 12, with Gaussian 09 at the B3LYP/6-31G** level
of theory.
phenylamine unit. The two reduction waves, one is quasi re-
versible in the region of 0.94e0.97 V, and another one is
reversible in the region of 1.37e1.43 belongs to the TCNE group.14
The theoretical calculations show good agreement with the
electronic properties. The contours of the HOMO, and LUMO of
compounds 5e9 are shown in Fig. 5.
In compounds 5e9 the HOMO orbitals are localized on the fer-
rocene, and the triphenylamine units, whereas the LUMO orbitals
are mainly concentrated on the acceptor units (malononitrile, 1-
indanone, 1,3-indanone, tetralone). The band gap in compounds
5e9 follows the order 5>9>8>6>7.
The contribution of the HOMO and LUMO orbitals in compounds
10e14 undergoes a drastic change, due to the incorporation of the
1,1,4,4-tetracyanobuta-1,3-diene (TCBD) unit. The LUMO orbitals
5. Theoretical calculations
The structural and electronic properties of the ferrocenyl
substituted triphenylamine based donoreacceptor compounds
5e14 were explored by means of theoretical calculations. The
structures of 5e14 (see Supplementary data) were optimized us-
ing density functional theory (DFT) with Gaussian 09 at the

R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
3395
Fig. 5. Frontier molecular orbitals of the ferrocenyl substituted triphenylamine donoreacceptor compounds 5e9.
are mainly concentrated on one of the TCBD unit, whereas the
HOMO orbitals remain confined on one of the ferrocene unit in
compounds 10 and 11 and on the triphenylamine unit in com-
pounds 12, 13, and 14 (Fig. 6).
substantial donoreacceptor interaction. The band gap in these
donoreacceptor molecular system can be reduced by the in-
corporation of 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) group. The
detailed photonic applications of these materials are underway.
Compounds 10e14 show lower band gap values compared to
the compounds 5e9, which is attributed to the presence of strong
electron withdrawing TCBD units (Fig. 7).
7. Experimental section
7.1. General experimental
6. Conclusion
1H NMR (400 MHz), and 13C NMR (100 MHz) spectra were
recorded on 400 MHz. Chemical shifts in 1H NMR, and 13C NMR
spectra were reported in parts per million (ppm) with TMS (0 ppm),
and CDCl3 (77.23 ppm) as standards. UVevisible absorption spectra
of all compounds were recorded in DCM. Cyclic voltammograms
(CVs) were recorded on electrochemical analyzer using Glassy
carbon as working electrode, Pt wire as the counter electrode, and
In summary a series of ferrocenyl substituted triphenylamine
based donoreacceptor compounds were synthesized by the Pd-
catalyzed Sonogashira cross-coupling, and Knoevenagel conden-
sation reactions. The cycloaddition reaction of 5e9 with TCNE
resulted new series of donoreacceptor compounds 10e14. The
electronic absorption, and cyclic voltammetric studies suggests

3396
R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
Fig. 6. Frontier molecular orbitals of the ferrocenyl substituted triphenylamine donoreacceptor compounds 10e14.

R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
3397
Fig. 7. Calculated HOMO and LUMO levels for: (a) the donoreacceptor compounds 5e9; (b) the donoreacceptor compounds 10e14.
saturated calomel electrode (SCE) as the reference electrode. The
scan rate was 100 mV sꢂ1 for CV. A solution of tetrabutylammo-
niumhexafluorophosphate (TBAPF6) in CH2Cl2 (0.1 M) was
employed as the supporting electrolyte. DCM was freshly distilled
from CaH2 prior to use. All potentials were experimentally refer-
enced against the saturated calomel electrode couple but were then
manipulated to be referenced against Fc/Fcþ as recommended by
IUPAC. Under our conditions, the Fc/Fcþ couple exhibited Eꢀ¼0.38 V
versus SCE. HRMS was recorded on TOF-Q mass spectrometer. All
reagents were obtained from commercial sources, and used as re-
ceived unless otherwise stated.
7.3.1. 2-{4-[Bis-(4-ethynyl-phenyl)-amino]-benzylidene}-malononi-
trile (6). Orange solid (0.091 g, 85%); mp >345.0 ꢀC; Rf (50% hexane/
CH2Cl2) 0.23; dH (400 MHz CDCl3) 7.78e7.76 (d, 2H, J¼8 Hz), 7.55 (s,
1H), 7.48e7.46 (d, 4H, J¼8 Hz), 7.13e7.11 (d, 4H, J¼8 Hz), 7.06e7.04
(d, 2H, J¼8 Hz), 4.51 (t, 4H, J¼4 Hz), 4.27e4.25 (d, 13H, J¼4 Hz); dC
(100.0 MHz, CDCl3) 157.8, 152.5, 144.2, 132.9, 132.9, 126.0, 123.9,
121.5,120.0,113.8, 89.5, 85.0, 71.5, 70.0, 69.0, 64.9; HRMS: Mþ found
737.1216. C46H31Fe2N3 requires 737.1213.
7.3.2. 2-{4-[Bis-(4-ethynyl-phenyl)-amino]-benzylidene}-indan-1,3-
dione (7). Red solid (0.095 g, 80%); mp >360.0 ꢀC; Rf (85% hexane/
CH2Cl2) 0.20; dH (400 MHz CDCl3) 7.78e7.76 (d, 2H, J¼8 Hz), 7.55 (s,
1H), 7.48e7.46 (d, 6H, J¼8 Hz), 7.12e7.10 (d, 6H, J¼8 Hz), 7.06e7.04
(d, 2H, J¼8 Hz), 4.51e4.50 (t, 4H, J¼4 Hz), 4.26e4.25 (d, 13H,
J¼4 Hz); dC (100.0 MHz, CDCl3) 157.8, 152.5, 144.2, 132.9, 126.0,
123.9, 121.5, 120.0, 114.9, 113.5, 89.5, 85.0, 71.5, 70.0, 69.0, 64.9;
HRMS: Mþ found 817.1361. C52H35Fe2NO2 requires 817.1364.
7.2. General procedure for the preparation of compounds 2, 3,
and 5e14
Compound 2 was synthesized by the VilsmeiereHaack for-
mylation reaction of triphenylamine 1.9 Compound 3 synthesized
from compound 2 according to the literature procedure.10
7.4. General procedure for the preparation of compounds
8 and 9
7.2.1. Synthesis of compound 5. 4-[Bis-(4-ethynyl ferrocenyl-
phenyl)-amino]-benzaldehyde (5).
A
mixture of 4-(bis(4-
iodophenyl)amino)-benzaldehyde (2 g, 3.80 mmol), and ethynyl
ferrocene (4 g, 9.52 mmol) was dissolved in dry THF (30 ml), added
triethylamine (15 ml), Pd(PPh3)4 (0.100 g, 0.08 mmol), stirred for
16 h at 60 ꢀC under argon atmosphere, after completion of the re-
action, the reaction mixture was concentrated under reduced
pressure, the crude compound was purified by flash column
chromatography (40% hexane/CH2Cl2) to give title compound 5
(1.712 g, 65%) as a orange solid; mp >300.0 ꢀC; Rf (40% hexane/
CH2Cl2) 0.45; dH (400 MHz, CDCl3) 9.86 (s, 1H), 7.74e7.72 (d, 2H,
J¼8 Hz), 7.45e743 (d, 4, J¼8 Hz), 7.12e7.09 (t, 6H), 4.51e4.50 (t, 4H,
J¼4 Hz), 4.25 (t, 12H); dC (100.0 MHz, CDCl3) 191.0, 152.4, 145.3,
132.8, 131.3, 130.2, 125.5, 121.1, 120.4, 88.9, 85.2, 71.5, 70.1, 69.0,
65.4; HRMS: Mþ found 689.1104, C43H31Fe2NO requires 689.1101.
The mixture of compound 5 (0.1 g, 0.14 mmol), and active
methylene derivatives (1-indanone, 1-tetralone) (0.072, 0.54 mmol)
was dissolved in dry in ethanol and THF (30:10) as solvent, added
10% NaOH or LiOH solution (1 ml), stirred for 16 h at 85 ꢀC, after
completion of the reaction, reaction mixture was allowed to cool to
room temperature, then quenched with cold water (0.5 ml), orange
solid gets precipitated, filtered dried under vacuum, crystallized
with CH2Cl2/ethanol (1:3) to give title compounds 8 and 9.
7.4.1. 2-{4-[Bis-(4-ethynyl-phenyl)-amino]-benzylidene}-indan-1-
one (8). Orange solid (0.088 g, 75%); mp >360.0 ꢀC; Rf (50% hexane/
CH2Cl2) 0.23; dH (400 MHz CDCl3) 7.93e7.91 (d, 1H)7.64 (s, 1H),
7.61e7.55 (q, 4H), 7.43e7.41 (d, 5H, J¼8 Hz), 7.15e7.13 (d, 3H,
J¼8 Hz), 7.10e7.08 (d, 4H, J¼8 Hz), 4.51e4.50 (t, 4H, J¼4 Hz),
4.25e4.24 (d, 12H, J¼4 Hz), 4.03 (s, 2H); dC (100.0 MHz, CDCl3)
194.3, 149.4, 145.8, 138.3, 132.9, 132.6, 132.1, 127.7, 126.1, 124.7,
123.0, 119.4, 88.4, 85.4, 71.3, 70.0, 68.8, 65.3, 32.5; HRMS: Mþ found
803.1567. C52H37Fe2NO requires 803.1571.
7.3. General procedure for the preparation of compounds
6 and 7
The mixture of compound 5 (0.1 g, 0.14 mmol) and corre-
sponding active methylene derivative (malononitrile, indan-1,3-
dione) (0.023 g, 0.95 mmol) was dissolved in dry DCM (5 ml),
added ammonium acetate (0.073g, 0.94 mmol) stirred for 3 h at
65 ꢀC in microwave, after completion of the reaction, reaction
mixture was concentrated under reduced pressure, the crude
compound was purified by column chromatography (80% hexane/
CH2Cl2) to give title compounds 6 and 7.
7.4.2. 2-{4-[Bis-(4-ethynyl-phenyl)-amino]-benzylidene}-1-tetralone
(9). Orange solid (0.083 g, yield 70%); mp >360.0 ꢀC; Rf (50% hex-
ane/CH2Cl2) 0.22; dH (400 MHz CDCl3) 8.13e8.11 (dd, 1H, J¼8 Hz),
7.84 (s, 1H), 7.51e7.47 (ddd, 2H, J¼8 Hz), 7.41e7.38 (m, 7H),
7.13e7.07 (dd, 6H, J¼8 Hz), 4.50e4.49 (t, 4H, J¼4 Hz), 4.30e4.24 (t,
12H, J¼4 Hz), 3.18e3.16 (t, 2H, J¼4 Hz), 2.99e2.96 (t, 2H, J¼4 Hz); dC

3398
R. Maragani, R. Misra / Tetrahedron 70 (2014) 3390e3399
(100.0 MHz, CDCl3) 187.7, 148.0, 146.1, 143.1, 136.4, 134.0, 132.6,
131.5, 128.1, 124.3, 123.2, 118.9, 88.2, 85.5, 71.4, 70.0, 68.8, 65.4, 28.8,
27.3; HRMS: Mþ found 817.1727. C53H39Fe2NO requires 817.1727
[Mþ].
J¼4 Hz), 4.89e4.87 (t, 2H, J¼4 Hz), 4.55e4.53 (t, 2H, J¼4 Hz),
4.46e4.44 (d, 10H), 3.15e3.12 (t, 2H), 3.00e2.97 (t, 2H); dC
(100.0 MHz, CDCl3) 187.5, 172.9, 164.1, 150.6, 143.3, 143.1, 136.4,
134.8, 133.5, 132.1, 130.9, 128.3, 127.0, 123.1, 113.5, 112.9, 112.4, 112.1,
82.8, 78.9, 75.1, 75.0, 72.8, 72.6, 71.2, 69.7, 28.8, 27.3; HRMS: MþnNa,
found 1096.1872. C65H39Fe2N9O requires 1096.1872.
7.5. General procedure for the preparation of compounds
10e14
Acknowledgements
To a solution of ferrocenyl substituted triphenylamine based
donoreacceptor compounds (10e14) (0.05 g, 0.72 mmol) in
CH2Cl2 (5 ml), TCNE (0.022 g, 1.77 mmol) was added, and the
mixture was stirred at 75 ꢀC for 3 h in microwave, after com-
pletion of the reaction, the reaction mixture was concentrated
under reduced pressure, the crude compound was purified by
column chromatography (5% CH2Cl2/EtOAC) to give title
compounds (10e14).
The work was supported by DST (_501100001409) and CSIR
(_501100001412) Govt. of India, New Delhi.
Supplementary data
The optimized structures of compounds 5e14 with dihedral
angles, cyclic voltammograms of compounds 5e14, 1H NMR, 13C
NMR spectra, mass spectroscopy data, UVevis graphs, DFT calcu-
lations of compounds 5e14 are provided. Supplementary data as-
sociated with this article can be found in the online version, at
http://dx.doi.org/10.1016/j.tet.2014.03.096.
7.5.1. 3-(4-{Bis-[4-(3,3-dicyano-1-dicyanomethylene-2-ferrocenyl-
allyl)-phenyl]-amino}-benzaldehyde (10). Light wine solid (0.049 g,
72%); mp >380.0 ꢀC; Rf (5% CH2Cl2/EtOAC) 0.50; dH (400 MHz
CDCl3) 9.98 (s, 1H), 7.89e7.88 (d, 2H, J¼4 Hz), 7.58e7.56 (d, 5H,
J¼8 Hz), 7.14e7.13 (d, 5H, J¼4 Hz), 5.54 (s, 2H), 5.04 (s, 2H), 4.89 (s,
2H), 4.46 (s, 12H); dC (100.0 MHz, CDCl3) 208.9, 190.5, 177.5, 164.2,
142.4, 136.3, 131.8, 130.9, 126.2, 124.0, 118.1, 113.5, 90.9, 72.8, 72.6,
72.5, 72.3, 71.0; HRMS: MþnNa found 968.1248. C55H31Fe2N9O re-
quires 968.1245.
References and notes
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7.5.2. 3-(4-{Bis-[4-(3,3-dicyano-1-dicyanomethylene-2-ferrocenyl-
allyl)-phenyl]-amino}-phenyl)-2-malononitrile (11). Light wine
solid red solid (0.042 g, 60%); mp >380.0 ꢀC; Rf (5% CH2Cl2/EtOAC)
0.32; dH (400 MHz CDCl3) 7.90e7.89 (d, 2H, J¼4, Hz), 7.68 (s, 1H),
7.59e7.57 (d, 4H, J¼8 Hz), 7.21e7.15 (m, 6H, J¼4 Hz), 5.48 (s, 2H),
5.05 (s, 2H), 4.90 (s, 2H), 4.47 (s, 11H); dC (100.0 MHz, CDCl3) 164.2,
132.9, 131.0, 127.2, 125.3, 124.5, 112.0, 111.8, 84.4, 82.0, 76.1, 72.9,
72.7, 71.2. HRMS: MþnNa found 1016.1356. C58H31Fe2N11 requires
1016.1358.
7.5.3. .3-(4-{Bis-[4-(3,3-dicyano-1-dicyanomethylene-2-ferrocenyl-
allyl)-phenyl]-amino}-2-(indane-1,3-dione) (12). Light wine solid
(0.040 g, 61%); mp >380.0 ꢀC; Rf (5% CH2Cl2/EtOAC) 0.25; dH
(400 MHz CDCl3) 8.50e8.48 (d, 2H, J¼8 Hz), 8.01 (s, 2H), 7.83 (s,
3H), 7.59e7.57 (d, 4H, J¼8 Hz), 7.19e7.17 (d, 5H, J¼8 Hz), 5.45 (s,
2H), 5.05 (s, 2H), 4.90 (s, 2H), 4.54e4.47 (d, 9H); dC (100.0 MHz,
CDCl3) 190.0, 164.2, 150.2, 148.1, 140.1, 136.3, 136.0, 130.9, 127.0,
125.8, 124.2, 123.4, 113.5, 112.9, 112.2, 112.0, 83.1, 76.0, 75.0, 72.8,
72.6, 71.2; HRMS: MþnNa found 1096.1504. C64H35Fe2N9O2 requires
1096.1508.
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(400 MHz CDCl3) 7.93e7.92 (d, 1H, J¼8 Hz), 7.71e7.69 (d, 2H,
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130.9, 127.0, 126.2, 123.4, 113.5, 112.9, 112.1, 76.0, 75.0, 72.8, 72.6,
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1082.1716.
M
þnNa found 1082.1716. C64H37Fe2N9O requires
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3399
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