Design, synthesis and characterization of ferrocene based V-shaped chromophores with modified nonlinear effect

Article abstract of DOI:10.1016/j.jorganchem.2017.07.023

In order to prepare D-π-A-π-D analogs have the ability to use in optical applications, 4H-pyran fragment conjugated with two styryl groups and their combination play π-spacer role between donor and acceptor groups. Malononitrile and 1, 3-indandione play as acceptor groups and ferrocene nuclei was chosen as donor group. ¹H and ¹³C NMR, FT-IR and mass spectroscopy and CHN analysis were used to confirm the structure of synthesized compounds. Electrochemical, photochemical and photophysical properties of these compounds were studied. The third order nonlinear refractive index, n₂, and nonlinear absorption coefficient, β, of synthesized chromophores were assessed by the open and closed aperture Z-scan measurements, respectively. The quantum chemistry study was performed on synthesized compounds with the DFT approach. The theoretical and experimental results show that these compounds can be considered as candidates to be used in optical applications.

Full text of DOI:10.1016/j.jorganchem.2017.07.023

Accepted Manuscript
Design, synthesis and characterization of ferrocene based V-shaped chromophores
with modified nonlinear effect
Reza Teimuri-Mofrad, Keshvar Rahimpour, Rahim Ghadari
PII:
S0022-328X(17)30452-7
10.1016/j.jorganchem.2017.07.023
JOM 20037
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 17 May 2017
Revised Date: 26 June 2017
Accepted Date: 18 July 2017
Please cite this article as: R. Teimuri-Mofrad, K. Rahimpour, R. Ghadari, Design, synthesis and
characterization of ferrocene based V-shaped chromophores with modified nonlinear effect, Journal of
Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.07.023.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
Design, Synthesis and Characterization of Ferrocene Based V-shaped Chromophores with
Modified Nonlinear Effect

ACCEPTED MANUSCRIPT
Design, Synthesis and Characterization of Ferrocene Based V-shaped
Chromophores with Modified Nonlinear Effect
Reza Teimuri-Mofrad,* Keshvar Rahimpour, Rahim Ghadari
Department of Organic and Biochemistry, Faculty of Chemistry, University of Tabriz, 5166614766
Tabriz, Iran. E-mail address: teymouri@tabrizu.ac.ir (R. Teimuri-Mofrad)
Abstract
In order to prepare D-π-A-π-D analogs have the ability to use in optical applications, 4H-pyran
fragment conjugated with two styryl groups and their combination play π-spacer role between
donor and acceptor groups. Malononitrile and 1, 3-indandione play as acceptor groups and
1
13
ferrocene nuclei was chosen as donor group. H and C NMR, FT-IR and mass spectroscopy
and CHN analysis were used to confirm the structure of synthesized compounds.
Electrochemical, photochemical and photophysical properties of these compounds were studied.
The third order nonlinear refractive index, n , and nonlinear absorption coefficient, β, of
2
synthesized chromophores were assessed by the open and closed aperture Z-scan measurements,
respectively. The quantum chemistry study was performed on synthesized compounds with the
DFT approach. The theoretical and experimental results show that these compounds can be
considered as candidates to be used in optical applications.
Keywords: Ferrocene, Knoevenagel condensation, Cyclic Voltammetry, NLO-phore.
Introduction
Over the years, searching for nonlinear optical (NLO) materials was an interesting field for
scientists because of their potential for use in electro-optic applications such as laser, hybrid
device systems, optical signal processing and optical computing [1]. Conjugated molecules with
1

ACCEPTED MANUSCRIPT
highly delocalized and polarizable π-electron systems are prospects for third-order nonlinear
materials [2].
In general, organic compounds contain donor (D) and acceptor (A) fragments bridged by π-
conjugation system are one of the well-known representative for NLO materials. The structure of
π-conjugated spacer plays an important role in charge transfer process [3].
4
H-pyran-4-one derivatives constitute a useful class of heterocyclic compounds, which are
widely distributed in natural and synthetic products [4]. In addition to bioorganic chemistry
applications, [5] γ-pyrones conjugated in a system with electron donor and electron acceptor
fragments widely adopted for organic photonics such as materials for the organic light emitting
diodes (OLEDs), solar cells, organic magnets and etc [6]. Furthermore V-shaped molecules
incorporating multiple 4H-pyran-4-ylidene moieties, one acting as spacer and the other(s) as
donor group(s), were reported in the literature [7].
Organometallic compounds are promising candidates for nonlinear optical materials, among the
organometallic compounds ferrocene derivatives possess good NLO properties [8]. Furthermore,
ferrocene is a well- known redox active material that can be incorporated into organic fragments
as an electro active center [9]. Ferrocene have attracted lots of attention with respect to their
electrochemical, electronic and magnetic properties [10]. The stability of ferrocene in aerobic
and aqueous media, easy functionalization and its favorable electrochemical and electro optical
properties have made ferrocenyl compounds very popular molecules for electro-optical
applications [11].
In recent years, considerable attention was paid to the simplification or improvement of existing
methods or discovering new methods in manufacture of NLO active organic compounds.
2

ACCEPTED MANUSCRIPT
Therefore, in continuance of our previous study on ferrocene containing materials, [12] we
decided to synthesis novel ferrocene based compound with extensive π-conjugated system.
In this work, 4H-pyran fragment conjugated with two styryl groups and their combination play
π-spacer role between ferrocenyl donor and acceptor groups. Final products of this study are
illustrated in Figure 1. Electrochemical, photochemical and photophysical properties of
synthesized compounds were studied and the third order (NLO) properties were measured using
Z-scan technique via the “closed” and “open” methods. The quantum chemistry study was
performed on synthesized compounds with the DFT approach. The B3LYP method and 6-31G
(d) basis set were used for optimizing the structures in the gas-phase.
[
Fig 1]
Results and Discussion
The design and preparation of D-π-A-π-D structure based compounds are the most extensively
investigated studies for optical applications. Ferrocene is one of the attractive organometallic
donors and pyran derivatives are common π spacers in this class of compounds. Target
molecules of this work, PBF, CPBF and IPBF, all were designed and synthesized from ordinary
intermediates
bromophenyl)vinyl]-4H-pyran-4-ylidene} malononitrile and 2-{2,6-bis-[(4-bromophenyl)vinyl]-
H-pyran-4-ylidene}-1,3-indandione).
(2,6-bis-[(4-bromophenyl)vinyl]-4H-pyran-4-one,
2-{2,6-bis-[(4-
4
The synthesis of final compounds involved the cross-coupling of bromine-substituted derivatives
with vinylferrocene under heck reaction conditions. Though the heck coupling is well- known
reaction for double bond formation in organic chemistry, because of some disadvantage such as
low yield, long time of reaction and unrecognizable byproducts in this case, we decided to
3

ACCEPTED MANUSCRIPT
optimize the reaction conditions. In our previous study, we used knoevenagel condensation that
have excellent yield without any unknown byproduct. Only byproduct in these condition was
mono condensation compound that can be transformed to desired product by longer reaction time
or in the presence of excess amount of aldehyde. Therefore, we were prepared 4-(2-
Ferrocenylvinyl)benzaldehyde (3) by heck reaction at the first (scheme 1) and then introduced
them in knoevenagel condensation to 2, 6- dimethyl pyran derivatives.
Scheme 1. Synthesis of 4-(2-Ferrocenylvinyl) benzaldehyde.
It’s better to mention that compound 3 was first synthesized in 1992 by H. E. Bunting and
coworkers in very low yield [13a]. There is also another synthetic method for compound 3 based
on wittig reaction in the literature [13b], but the yield of our product was better than reported
one. On the other hand, the wittig reaction affords a mixture of (E)/(Z) isomers whereas heck
reaction afford (E) isomer in 88%. Final products in Knoevenagel condensation have a
significant high yield. The modest synthetic procedure of these compounds are shown in scheme
2
.
1
13
The elemental analyses, mass spectra, FT-IR, H NMR and C NMR spectra all confirmed the
predicted molecular structure.
4

ACCEPTED MANUSCRIPT
Scheme 2. Synthesis of ferrocene-based dyes. i) A, acetic anhydride, reflux. ii) 4-
Bromobenzaldehyde, piperidine, acetonitrile, reflux. iii) Vinylferrocene, K
tetrabutylammonium tetrafluorobora, Pd(OAC) , DMF, 80 °C. iv) 4-(2-Ferrocenylvinyl)
benzaldehyde, piperidine, acetonitrile, reflux.
2 3
CO ,
2
1
The H NMR spectra of these compounds show three signals for the protons of ferrocene, a
singlet signal for unsubstituted cyclopentadienyl ring and two split downfield signals at 4.33 and
1
4
.49 ppm for substituted ring. In particular, H NMR chemical shifts suggest that 1, 3-indandione
1
is stronger than malononitrile in the place of an acceptor. For example, the H resonance
corresponding to H-3 and H-5 of the pyran ring in IPBF is observed at 8.47 ppm whereas the
same protons in CPBF are appeared at 6.69 ppm. This chemical shift can also be compared to
those in PBF (Figure 2). Similar behavior was seen for exocyclic vinylic protons but complexity
of this area of the spectrum because the presence of aromatic protons prevents detailed
discussion in this case. However, a set of doublet signals in 6.69-7.62 ppm with coupling
5

ACCEPTED MANUSCRIPT
constant of 16 Hz corresponding to E-configuration for exocyclic vinylic protons, well predicts
all-trans geometry for these chromophores.
[
Fig 2]
Not only acceptor groups, but also donor groups play an important role in intramolecular charge
transfer process and in the present case ferrocene can compete with bulky amino aryls used as
common donors in such systems [14].
The optimum geometry and electron-state-density distribution of the highest occupied molecular
orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of all synthesized
compounds were calculated by the B3LYP method and the 6-31G(d) basis set. Figure 3 shows
the optimized structure and the electron-state-density distribution of the HOMO and LUMO of
these compounds. The HOMO state density mainly distributed on the ferrocenyl moieties and the
electron density of LUMO was mainly localized at the 2, 6- dimethyl pyran derivatives with
some extending to the phenyl units of the molecule.
[
Fig 3]
Stability of positive charge on ferrocenyl unit has a direct relationship with π- donor strength of
ferrocene nucleus. DFT calculation of partial charges for atoms and band lengths of the
synthesized NLO-phores are in good agreement with experimental results (Table 1). Increasing
positive charge on H-3 and H-5 of the pyran ring shows that intramolecular charge transfer
1
process is well done. In line with H NMR results this positive charge increases with the increase
of the electron withdrawing ability of the acceptor unit. On the other hand decrease in the bond
lengths of the pyran ring which is normally single in the neutral resonance form indicates that the
formation of zwitterionic resonance form is facilitated by increasing of acceptor ability.
6

ACCEPTED MANUSCRIPT
[
Table 1]
The experimental energy levels of compounds are calculated via cyclic voltammetry according to
the method explained previously [11a] and their values listed in table 2. HOMO and LUMO
energy levels are one of the basic criteria’s in material selection for optical usage. According to
obtained results the band gaps of these kind conjugated chromophores can be tuned by
incorporation of the different electron-acceptor moieties.
[Table 2]
Organic photovoltaic materials have an optical band gap in the range of 1-4 ev; the maximum
gain for the photocurrent may be achieved by applying materials with a lower optical band-gap
[15]. As the electron-donating ability of the aromatic donor group is increased, the band gap of
the bis-condensed product with the push–pull system becomes small. Table 3 shows the band
gap energy of some V-shaped materials in the literature. Compared between them and our
ferrocene based materials confirmed that ferrocene is an ideal donor group.
[Table 3]
In comparison between ferrocene based V-shaped and linear chromophores, the former one has
low band gap; the Eg values of some linear ferrocenyl chromophores reported in literature were
tabulated in table 4.
[Table 4]
The integration of redox-active components into opto-electronic materials can be results in the
creation molecules with modified optical properties; hence the redox properties of synthesized
compounds were determined by cyclic voltammetry in acetonitrile at room temperature (Figure
7

ACCEPTED MANUSCRIPT
4
). The anodic and cathodic peak separation (ꢀEp) in the cyclic voltammograms was found to be
in the range between 0.06 V and 0.10 V (PBF: 0.11, CPBF: 0.08 and IPBF: 0.10 V). However,
the ꢀEp of PBF was found to be higher at 0.11 V, indicating a slow electron transfer. The
corresponding peak potentials E and E are independent of scan rate.
pa
pc
[
Fig 4]
In order to observe phenomena such as aggregation and solvatochromism of the synthesized
compounds, we investigated the UV-Vis absorption spectra of the synthesized NLO-phores
across a range of concentration in some solvents with different polarities (Figure 5). Acetonitrile
and dioxane represented the two extremes in terms of dielectric constants. Acetonitrile has the
highest dielectric constant (37.5) among the examined solvents in the present work, while
dioxane has the lowest amount (2.2). The other solvents in table 5 represent a range intermediate
between these two extremes. The absorption data (λmax and extinction coefficient) from these
experiments are listed in table 5. As elicited from the previous studies, ferrocenyl compounds
possess two characteristic transitions (λmax) assigned to π-π* and MLCT transition. But in this
case the close overlap was seen between two transition bands, to the extent that the MLCT band
was seen just as a shoulder for π-π* peak not even possessing a specified λmax. This overlapping
was increased as the electron withdrawing capability of acceptor moiety increased, insofar that π-
π* transition covered the MLCT transition in the case of IPBF compound. UV-Vis absorption
spectrums show no variation across a range of concentrations conforming that no aggregation
was occurred. As an interesting result the acquired absorption spectrum in chloroform solvent is
totally different from the other spectra. It is obvious that the electronic absorption spectra of
ferrocene in halocarbon solvents such as chloroform and carbontetrachloride is different than
what is expected which is because of ferrocene to solvent charge-transfer (CTTS) phenomena.
8

ACCEPTED MANUSCRIPT
[
Fig 5]
[Table 5]
The NLO properties of synthesized compounds were investigated with Z-scan technique under
continuous-wave diode laser radiation at 655 nm in DMF solution. The third order nonlinear
2
refractive index, n , and nonlinear absorption coefficient, β, of the DMF solution of
chromophores were assessed by the open and close aperture Z-scan measurements, respectively.
Fig. 6(a) and (b) shows the open aperture (OA) and closed aperture (CA) Z-scan data for
ferrocene derivatives solution. In the case of CA datas, all samples have Peak-Valley
configuration, which is corresponding of negative NLR effects and means that self-defocusing
phenomena has been occurred; Obtained data for each compound were listed in table 6.
[Table 6]
[
Fig 6]
We know that thermally induced variation in refractive index of the medium is dominate
phenomena in large nonlinear refractive index, it seems that in our compounds this factor play an
important role. The acceptable values of ꢀꢁ in these compounds suggested that these type of
ferrocene derivatives have potential for using in nonlinear optical applications.
ꢂꢃ
In summary, understanding the electronic and optical properties of new synthesized compounds
is fundamental level of feasibility study of them in optical applications. In present work, three
new ferrocene based chromophores were synthesized. UV-vis spectroscopy and z-scan technic in
both open and closed aperture mode were used to study of linear and nonlinear optical properties,
respectively. We know that in fabrication of optical devices band gap energy of chromophores
play an important role; HOMO and LUMO energy levels must be identified to determine the
9

ACCEPTED MANUSCRIPT
possibility of energy transfer. Therefore we used DFT calculations and cyclic voltammetry
measurement to the theoretical and experimental study of HOMO and LUMO energy levels.
Based on obtained results, our synthetic dyad with narrow band gap and acceptable optical
properties has the potential to be used in the fabrication of electroluminescent devices.
Experimental Section
General Methods. Commercial compounds were used without further purification. Column
chromatography was performed using SiO (60 Å, 230−400 mesh, particle size 0.040−0.063
2
1
13
mm) at 25 °C. H and C NMR spectra were obtained with 400 and 100 MHz spectrometers,
and the chemical shifts are reported in ppm and were referenced to the residual solvent as
1
13
1
follows: CHCl = 7.26 δ ( H), 76.0 δ ( C). For H NMR, coupling constants J are given in Hz
3
and the resonance multiplicity is described as s (singlet), d (doublet), t (triplet), m (multiplet).
−
1
The FT-IR spectra are reported as wavenumbers ν
̃ (cm ) with band intensities indicated as s
(strong), m (medium), w (weak). The mass spectra operated at 70 eV, the most important peaks
+
are reported in m/z units with M as the molecular ion and with the corresponding intensities in
%. Elemental analysis was used to identify of chemical structure of chromophores. The iron
analysis was performed by atomic absorption spectrophotometer and UV/vis spectroscopy was
recorded on a UV/vis spectrophotometer. Cyclic voltammetry measurements were performed on
1
mM solutions of ferrocene derivative in acetonitrile in the presence of 0.100 M LiClO
supporting electrolytes, with a standard three-electrode cell. A 2-mm-diameter glassy carbon
GC) was used as the working electrode. A silver/silver chloride (Ag/AgCl) electrode and a
4
, as
(
platinum electrode were used as the reference and the counter electrodes, respectively. All
potentials in this study are reported with respect to the Ag/AgCl.
1
0

ACCEPTED MANUSCRIPT
Synthesis of 2,6-bis[2-(4-bromophenyl)vinyl]pyran-4-ylidene derivatives: 2-(2, 6-Dimethyl-
4
H-pyran-4-ylidene) malononitrile and 4-(1, 3-indandione)-2,6-dimethyl-4H-pyran [18] were
prepared according to the reference method. Bromine-substituted compounds were synthesized
according to literature [19].
General procedure for the Palladium-Catalyzed coupling of vinylferrocene: A mixture of
vinylferrocene (1 mmol), K CO (2.5 or 5 mmol), tetrabutylammonium tetrafluoroborat (2.5 or 5
2
3
mmol), the given amount of appropriate bromine-substituted compound and catalytic amount of
Pd(OAC) in 10 ml DMF was stirred at 80 °C under argon atmosphere overnight. After the
2
completion of the reaction, the cooled mixture was filtered, diluted with CH
2 2
Cl (50 ml) and
washed with H O (3×50 ml). The organic phase was dried over Na SO , filtered and the solvent
2
2
4
was removed under the reduce pressure. The crude products were purified by column
chromatography on silica gel with hexane/EtOAC as eluent. Specific details for each compound
are given below.
4
-(2-Ferrocenylvinyl)benzaldehyde (3): from 0.1 g (0.47 mmol) vinyl ferrocene and 0.08 g
(0.47 mmol) 4-bromobenzaldehyde, 0.11 g (0.36 mmol) red shining crystals was obtained in
[
13]
1
8
8% yield: R = 0.50 (Hexane: EtOAc 9:1); m.p. 150 °C, lit.
150-151 °C; H NMR (400 MHz,
f
3
CDCl , 25°C): δ= 9.97 (s, 1H, CHO), 7.83 (d, 2H, ArH), 7.56 (d. 2H, ArH), 7.07 (d, J (H,H)=16
3
3
Hz, 1H, =CH), 6.72 (d, J (H,H)=16 Hz, 1H, =CH), 4.50 (t, J=1.78 Hz, 2H, Cp), 4.35 (t, J=1.78
-1
Hz, 2H, Cp), 4.15 (s, 5H, Cp) ppm; FT-IR (KBr, cm ): 3074, 3062 (w), 2936, 2852 (w), 1685
s), 1591, 1561 (w), 814 (w).
,6-Bis [4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-one (6): from 0.1 g (0.47 mmol) vinyl
(
2
ferrocene and 0.1 g (0.23 mmol) 2,6-bis-[(4-bromophenyl)vinyl]-4H-pyran-4-one, 0.10 g (0.13
mmol) orange solid was obtained in 55% yield: R = 0.10 (Hexane: EtOAc 1:1); m.p. 300 °C <
f
1
1

ACCEPTED MANUSCRIPT
1
3
Decompose; H NMR (400 MHz, CDCl
3
, 25°C,): δ= 7.56-7.45 (m, 8H, ArH), 7.47 (d, J
3
3
(
H,H)=16 Hz, 2H, =C-H), 6.98 (d, J (H,H)=16 Hz, 2H, =C-H), 6.74 (d, J (H,H)=16 Hz, 2H,
3
=
C-H), 6.71 (d, J (H,H)=16 Hz, 2H, =C-H), 6.29 (s, 2H, Pyran), 4.49 (t, J=1.72 Hz, 4H, Cp),
1
3
4
.33 (t, J=1.72 Hz, 4H, Cp), 4.16 (s, 10H, Cp) ppm; C NMR (100 MHz, CDCl , 25°C, TMS):
3
δ= 178.70, 160.45, 138.50, 134.65, 132.25, 127.83, 127.05, 125.22, 124.05, 118.00, 112.82,
-1
8
1.82, 68.41, 68.29, 66.07 ppm; FT-IR (KBr, cm ): 3437 (w), 2924, 2859 (w), 1637 (s), 1552
+
(m), 1463 (m), 484 (w); m/z: calcd. for C45
H36Fe
2
O
2
[M] : 720, found 720; Anal. Calc. for
C
45 2 2
H36Fe O : C 75.02, H 5.03, Fe 15.50; Found: C 75.00, H 4.99, Fe 15.46.
2
-{2,6-Bis-[4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-ylidine} malononitrile (9a): from 0.1 g
(0.47 mmol) vinyl ferrocene and 0.11 g (0.23 mmol) 2-{2,6-bis-[(4-bromophenyl)vinyl]-4H-
f
pyran-4-ylidene} malononitrile, 0.10 g (0.12 mmol) black solid was obtained in 52% yield: R =
1
0
7
.27 (Hexane: EtOAc 1:1); m.p. 300 °C < Decompose; H NMR (400 MHz, CDCl , 25°C): δ=
3
3
.54-7.50 (m, 8H, ArH, 2H =C-H), 7.00 (d, J (H,H)= 16 Hz, 2H, =C-H), 6.78-6.69 (m, 4H, =C-
H), 6.69 (s, 2H, Pyran), 4.50 (t, J=1.80 Hz, 4H, Cp), 4.34 (t, J=1.80 Hz, 4H, Cp), 4.16 (s, 10H,
1
3
Cp) ppm; C NMR (100 MHz, CDCl , 25°C, TMS): δ= 178.90, 157.36, 139.20, 136.61, 131.77,
3
1
28.49, 127.36, 125.33, 123.85, 116.50, 114.34, 106.07, 81.64, 70.01, 68.54, 68.32, 66.14 ppm;
-1
FT-IR (KBr, cm ): 3032, 2924 (w), 2200 (m), 1636 (s), 1539 (m), 1499 (m), 485 (w); m/z: calcd.
+
for C48
H36Fe
2
N
2
O [M] : 768, found 768; Anal. Calc. for C48
H36Fe
2
N
2
O: C 75.02, H 4.71, N 3.64,
Fe 14.53; Found: C 75.04, H 4.74, N 3.66, Fe 14.48.
-{2,6-Bis-[4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-ylidine}1,3-indan dione (9b): from 0.1 g
0.47 mmol) vinyl ferrocene and 0.13 g (0.23 mmol) 2-{2,6-bis-[(4-bromophenyl)vinyl]-4H-
2
(
pyran-4-ylidene}-1,3-indan dione, 0.10 g (0.11 mmol) black solid was obtained in 48% yield:
1
R = 0.53 (Hexane: EtOAc 1:1); m.p. 300 °C < Decompose; H NMR (400 MHz, CDCl , 25°C):
f
3
1
2

ACCEPTED MANUSCRIPT
3
δ= 8.47 (s, 2H, Pyran), 7.62-7.41 (m, 12H, ArH, 2H =C-H), 7.00 (d, J (H,H)=16 Hz, 2H, =C-H),
3
3
6
4
.91 (d, J (H,H)=16 Hz, 2H, =C-H), 6.72 (d, J (H,H)=16 Hz, 2H, =C-H), 4.50 (t, J=1.76 Hz,
1
3
H, Cp), 4.34 (t, J=1.76 Hz, 4H, Cp), 4.16 (s, 10H, Cp) ppm; C NMR (100 MHz, CDCl , 25°C,
3
TMS): δ= 190.40, 160.07, 159.17, 138.72, 135.09, 134.40, 132.40, 132.23, 131.30, 128.04,
27.23, 125.30, 124.08, 120.38, 118.24, 108.01, 80.02, 68.46, 68.31, 66.12 ppm; FT-IR (KBr,
1
-1
cm ): 2923, 2857 (w), 1642 (m), 1514 (m), 1463 (m), 464 (w); m/z: calcd. for C H Fe O
3
5
4
40
2
+
[
M] : 848, found 848; Anal. Calc. for C54
H 4.76, Fe 13.19.
Condensation of 4-(2-ferrocenylvinyl)benzaldehyde with pyran derivatives: A solution of
H-pyrane derivative (4, 7a and 7b) (1 mmol), 4-(2-ferrocenylvinyl)benzaldehyde (2 mmol) and
2 3
H40Fe O : C 76.43, H 4.74, Fe 13.16; Found: C 76.46,
4
piperidine (1 mL) in dry acetonitrile (10 mL) was refluxed for 1 hours under argon atmosphere.
The reaction was controlled with TLC method by monitoring the 4-(2-ferrocenylvinyl)
benzaldehyde in the solution of reaction. After the completion of the reaction, the solution was
cooled to room temperature and the product was purified using column chromatography over
silica gel and hexane/EtOAC as eluent. Further purification was performed by recrystallization
from hexane and EtOAc to give corresponding compound as a pure solid. Specific details for
each compound are given below and spectral data in each case is similar to reported one in
above.
2
,6-Bis [4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-one (6): from 0.1 g (0.32 mmol) 4-(2-
Ferrocenylvinyl) benzaldehyde and 0.02 g (0.11 mmol) 2, 6-Methyl-4H-pyran-4-one, 0.08 g
0.13 mmol) orange solid was obtained in 75% yield
(
1
3

ACCEPTED MANUSCRIPT
2
-{2,6-Bis-[4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-ylidine} malononitrile (9a): from 0.1 g
(
0.32 mmol) 4-(2-Ferrocenylvinyl) benzaldehyde and 0.025 g (0.16 mmol) 2-(2, 6-Methyl-4H-
pyran-4-ylidene) malononitrile, 0.09 g (0.12 mmol) black solid was obtained in 73% yield.
-{2,6-Bis-[4-(2-ferrocenylvinyl)styryl]-4H-pyran-4-ylidine}1,3-indan dione (9b): from 0.1 g
0.32 mmol) 4-(2-Ferrocenylvinyl) benzaldehyde and 0.04 g (0.16 mmol) 4-(1, 3-indandione)-
,6-dimethyl-4H-pyran, 0.10 g (0.11 mmol) black solid was obtained in 75% yield.
2
(
2
Theoretical Methods. All calculations were carried out using Gaussian 09 (Rev. D.01) [20]
program package by using density functional theory (DFT) approach. The B3LYP method used
for optimizing the structures [21]. The 6-31G (d) basis set was used [22]. Structure of
compounds was optimized in the gas-phase. No symmetry constraints were imposed.
Nonlinear optical measurements. The third-order NLO properties were measured by the Z-
Scan technique using a Ti: sapphire laser with 4.5 ns pulse widths. The diameter of the laser
beam was 36 ꢁm. The operating wavelength was centred at 655 nm.
The experiments were performed at 22 °C in DMF solutions using a 1 mm-thick quartz cell. The
spatial profiles of the optical pulses were nearly Gaussian. The laser beam was focused with a 10
cm focal-length focusing mirror. The NLO properties of the samples were manifested by moving
the samples along the axis of the incident beam (Z-direction) with respect to the focal point. An
aperture of 1 mm in radius was placed in front of the detector to assist the measurement of the
self-focusing effect. All optical measurements were carried out in ambient atmosphere at room
temperature.
Acknowledgements
1
4

ACCEPTED MANUSCRIPT
We gratefully acknowledge the financial support for this work by the Research Council of
University of Tabriz.
References
[
1] (a) N. Nwaji, J. Mack, J. Britton, T. Nyokong, New J. Chem., 41(5) (2017) 2020-2028;
b) Z. Y. Tian, W. T. Huang, D. B. Xiao, S. Q. Wang, Y. S. Wu, Q. H. Gong, W. S. Yang
and J. N. Yao, Chem. Phys. Lett. 391 (2004), 283-287;
(
(
c) J. Luo, S. Huang, Z. Shi, B. M. Polishak, X. H. Zhou and A. K. Y. Jen, Chem. Mater. 23
2011), 544-553.
(
[
[
[
2] Y. Zhao, N. Zhou, A. D. Slepkov, S. C. Ciulei, R. McDonald, F. A. Hegmann and R. R.
Tykwinski, Helvetica Chimica Acta. 90 (2007), 909-927.
3] N. Tsuboya, R. Hamasaki, M. Ito, M. Mitsuishi, T. Miyashita and Y. Yamamoto, J. Mater.
Chem. 13 (2003), 511-513.
4] (a) R. Teimuri-Mofrad and F. Abrishami, ARKIVOC. 14 (2007), 20-26;
(
b) H. Miyabe, O. Miyata, T. Naito, ChemInform. 43(2) (2012). (10.1002/chin.201202217).
5] F. M. Moghaddam, Gh. R. Bardajee and H. Ismaili, J. Braz. Chem. Soc. 18(5) (2007), 1024-
027.
6] (a) L.S. Hung and C.H. Chen, Mater. Sci. Eng: R. 39 (2002), 143-222;
[
[
1
(b) P. Strohriegel and J.V. Grazulevicius, Adv. Mater. 14 (2002), 1439-1452;
(c) D.M. Bassani, L. Jonusauskaite, A. Lavie-Cambot, N.D. McClenaghan, J. L. Pozzo, D.
Ray and G. Vives, Coord. Chem. Rev. 254 (2010), 2429-2445.
1
5

ACCEPTED MANUSCRIPT
[
7] R. Andreu, E. Galan, J. Garın, V. Herrero, E. Lacarra, J. Orduna, R. Alicante, B. Villacampa,
J. Org. Chem. 75 (2010), 1684-1692.
[8] (a) S. Scuppa, L. Orian, D. Dini, S. Santi and M. Meneghetti, J. Phys. Chem. A 113 (2009),
9
286-9294;
(
b) A. Wrona, J. Zakrzewski, L. Jerzykiewicz and K. Nakatani, J. Organomet. Chem. 693
2008), 2982-2986;
(
(c) J
. A. Mata, E. Peris, I. Asselberghs, R. V. Boxel, A. Persoons, New J. Chem., 25
(2001), 299-304.
[
9] (a) F. Yang, X. L. Xu, Y. H. Gong, W. W. Qiu, Z. R. Sun, J. W. Zhou, P. Audebert and J.
Tang, Tetrahedron, 63 (2007), 9188-9194;
(
b) S. Miao, Q. F. Zhang and W. H. Leung, J. Chem. Res. 2004 (2004), 714-715.
10] (a) K. K. W. Lo, J. S. Y. Lau, N. Zhu, New J. Chem., 30 (2006), 1567-1575;
b) Z. u. Abdin, L. Wang, H. Yu, M. Saleem, M. Akram, N. M. Abbasi, H. Khalid, R. Sun,
Y. Chen, New J. Chem., 40 (2016), 3155-3163;
[
(
(
c) D. M. Lyons, J. Mohanraj, G. Accorsi, N. Armaroli, P. D. W. Boyd, New J. Chem., 35
2011), 632-639;
(
(d) C. Ornelas, New J. Chem., 35 (2011), 1973-1985.
[11] (a) C. S. Allardyce, A. Dorcier, C. Scolaro and P. J. Dyson, Appl. Organomet. Chem. 19
(2005), 1-10;
(b) E. A. Hillard, A. Vessie`res and G. Jaouen, Top. Organomet. Chem. 32 (2010), 81-117;
1
6

ACCEPTED MANUSCRIPT
(c) L. V. Snegur, V. N. Babin, A. A. Simenel, Y. S. Nekrasov, L. A. Ostrovskaya and N.
S. Sergeeva, Russ. Chem. Bull. Int. Ed. 59 (2010), 2167-2178;
d) M. F. R. Fouda, M. M. Abd-Elzaher, R. A. Abdelsamaia and A. A. Labib, Appl. Organo-
(
met. Chem. 21 (2007), 613-625.
[12] (a) R. Teimuri-Mofrad, K. Rahimpour and R. Ghadari, J. Organomet. Chem. 811 (2016),
1
4-19;
b) R. Teimuri-Mofrad, K. D. Safa and K. Rahimpour, J. Organomet. Chem., 758 (2014),
6-44;
c) R. Teimuri-Mofrad, H. Abbasi, K. D. Safa and B. Tahmasebi, ARKIVOC. 4 (2016),
(
3
(
371-384.
[13] (a) H. E. Bunting, M. L. H. Green, S. R. Marder and M. E. Thompson, Pdyhedron. 11
(1992), 1489-1499.
(
b)A. J. Moore, A. Chesney, M. R. Bryce, A. S. Batsanov, J. F. Kelly, J. A. K. Howard, I. F.
Perepichka, D. F. Perepichka, G. Meshulam, G. Berkovic, Z. Kotler, R. Mazor and V.
Khodorkovsky, Eur. J. Org. Chem. 2001 (2001), 2671-2687.
[14] (a) B. J. Jung, C. B. Yoon, H. K. Shim, L. M. Do, T. Zyung, Adv. Funct. Mater. 11 (2001),
430-434;
(b) S. Ermer, S. M. Lovely, D. S. Leung, ACS Symp. Ser. 601 (1995), 95-110;
(c) A. Vembris, E. Zarins, J. Jubels, V. Kokars, I. Muzikante, A. Miasojedovas, S. Jursenas,
Optical Materials. 34 (2012), 1501-1506;
1
7

ACCEPTED MANUSCRIPT
(d) E. Zarins, K. Siltane, E. Misina, V. Kokars, et al. Proc. SPIE 8435, Organic Photonics V,
8
4351Q, June 1, 2012, (doi:10.1117/12.921996).
[15] H. Hoppe and N. S. Sariciftci, J. Mater. Res. 19 (2004), 1924-1945.
[16] (a) B. J. Jung, J. I. Lee, H. Y. Chu, L. M. Do, J. Lee and H. K. Shim, J. Mater. Chem. 15
(2005), 2470–2475;
(b) Y. S. Yao, J. Xiao, X. S. Wang, Z. B. Deng, B. W. Zhang, Adv. Funct. Mater, 16 (2006),
7
09-718.
17] (a) F. Bures, RSC Adv. 4 (2014), 58826–58851;
b) S. Dhoun, G. Depotter, S. Kaur, P. Kaur, K. Clays and K. Singh, 6 (56) (2016), 50688-
0696.
[
(
5
[
[
[
18] D. U. Kim, S. H. Paik, S. H. Kim, Y. H. Tak, Y. S. Han, S. D. Kim, K. B. Kim, H. J. Ju, T.
J. Kim, Mater. Sci. Eng: C. 24 (2004), 147-149.
19] Q. Peng, Z. Y. Lu, Y. Huang, M. G. Xie, S. H. Han, J. B. Peng, Y. Cao. Macromolecules.
3
7 (2004), 260-266.
20] Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M.
A. Robb and et al. Gaussian 09, Gaussian, Inc., Wallingford, CT, 2009.
[21] A.D. Becke, J. Chem. Phys, 98 (1993), 5648-5652.
[
22] V. A. Rassolov, M. A. Ratner, J. A. Pople, P. C. Redfern and L. A. Curtiss, J. Comp.
Chem. 22 (2001), 976-984.
1
8

ACCEPTED MANUSCRIPT
Fig 1. Structure of ferrocene-based NLO-phores synthesized in this study.
1
Fig 2. Chemical shifts of the pyran ring proton in H NMR spectra of PBF, CPBF and IPBF.
1
9

ACCEPTED MANUSCRIPT
Fig 3. Optimized geometries and Molecular orbital surfaces of the HOMO and LUMO of
synthesized compounds obtained at B3LYP/6-31G(d) level.
-1
Fig 4. CV curves of the PBF, CPBF and IPBF in different scan rates (scan rates given in mV s ).
2
0

ACCEPTED MANUSCRIPT
2
1

ACCEPTED MANUSCRIPT
Fig 5. UV−Vis absorption spectra: (a) Normalized UV-Vis absorption of PBF in series of
solvents. (b) Normalized UV-Vis absorption of CPBF in series of solvents. (c) Normalized UV-
Vis absorption of IPBF in series of solvents. (d) Normalized UV-Vis absorption of NLO-phores
in Dioxane. (e) Concentration dependence of UV−Vis absorption spectra of PBF in DCM. (f)
Concentration dependence of UV−Vis absorption spectra of CPBF in DCM. (g) Concentration
dependence of UV−Vis absorption spectra of IPBF in DCM. (h) Solvatochromism effect on
π→π* transition.
Fig 6. Z-scan data in DMF solution, (a) obtained in an OA configuration, (b) obtained in a CA
configuration.
2
2

ACCEPTED MANUSCRIPT
Table1. Selected ESP charge and bond length (in A°) in the spacer pyran
Compound
ESP charge H-3 & H-5
a
b
PBF
CPBF
IPBF
0.20
0.22
0.26
1.46213
1.43439
1.43244
1.35850
1.36429
1.36500
Table 2. Experimental data for synthesized compounds.
Eg (experiment
UV–Vis)
HOMO (eV)
(experimental CV)
LUMO (eV)
(experimental CV)
Compound
a
PBF
CPBF
IPBF
2.19
1.91
1.89
-4.40
-4.20
-5.01
-2.21
-2.29
-3.12
a
11a
The ICT energies (hνICT) derived from the wavelength at the absorption edge from UV-Vis spectra
2
3

ACCEPTED MANUSCRIPT
Table 3. Band gap energy of V-shaped chromophores [7, 16]
R
A
B
R
A
B
-
1
2
.91 ev
1.89 ev
2.44 ev
.69 ev
2.69 ev
1.97 ev
-
Table 4. Band gap energy of linear ferrocene-based chromophores [17]
Band gap
energy
Band gap
energy
Compound (Fc = ferrocene)
Compound (Fc = ferrocene)
2
2
.20 ev
.93 ev
2.90 ev
2.95 ev
2
4

ACCEPTED MANUSCRIPT
Table 5. Absorption spectral data of novel ferrocene-based NLO-phores in various solvents.
Solvent
a
Dioxane (36)
Chloroform (39.1)
DCM (40.7)
Acetone (42.2)
Acetonitrile (45.6)
Compound
PBF (π-π*)
350
(53000)
425
328
(18108)
410
363
(55000)
435
353
(42000)
359
359
(32388)
428
-
1
-1
λ
λ
λ
max /nm (ε /M cm )
CPBF (π-π*)
-
1
-1
max /nm (ε /M cm )
(65666)
480
(18324)
368
(74416)
485
(63416)
480
(32833)
487
IPBF (π-π*)
-
1
-1
max /nm (ε /M cm )
(74666)
(35833)
(52500)
(59416)
(13160)
a
-1
The solvent parameters E in kcal.mol
T
Table 6. Nonlinear parameters of synthesized compounds
ꢄꢁꢅꢆꢇꢈ
ꢃ
ꢑꢒ
ꢑ ꢁꢅꢆ ⁄ꢊꢃ
ꢓ
ꢌꢁꢍꢃꢁꢎꢏꢐꢃ
compound
ꢉꢁꢅꢆ⁄ꢊꢃ
ꢋꢆ
ꢌ
ꢁꢍꢃꢁꢎꢏꢐꢃ
ꢔꢎ
ꢌ
ꢁꢍꢃꢁꢎꢏꢐꢃ
ꢓ
-4
-4
-3
-3
-7
-4
-3
PBF
CPBF
IPBF
1.5
1.8
6.9
7.1×10
6.5×10
2.6×10
1.9×10
1.7×10
7.0×10
1.4270
1.4266
1.4267
-1.5×10
-7.7×10
-8.7×10
-1.2×10
2.0×10
-3
-3
-7
-4
-3
-3
-1.7×10
1.9×10
-7
-3
-2.4×10
7.1×10
2
5

ACCEPTED MANUSCRIPT
Highlights
•
•
•
•
Ferrocene based D-π-A-π-D analogs were synthesized aiming to use them in optical
applications.
Electrochemical, photochemical and photophysical properties of these compounds were
studied.
Quantum chemistry study was performed on synthesized compounds with the DFT
approach.
The theoretical and experimental results show that these compounds can be considered as
candidates to be used in optical applications.