Synthesis, crystal structure and nonlinear optical properties of ferrocene-containing metalloporphyrins

Article abstract of DOI:10.1016/j.ica.2020.119816

Five ferrocene-containing metalloporphyrins (Pd-P-Fc, Co-P-Fc, Cu-P-Fc, Zn-P-Fc and Ni-P-Fc) were synthesized and characterized. The crystal structure of Zn-P-Fc determined by using the single crystal diffraction technique belongs to the triclinic system. A typical aggregation of Zn-P-Fc occurs when the concentration of Zn-P-Fc is greater than 2.0 × 10^?6 mol/L in solution. The strong interaction between the metalloporphyrin and the ferrocene group was inferred by the absorption spectra, fluorescence spectra and the DFT calculation. Good nonlinear optical properties of these materials were inferred from the low fluorescence quantum yields and the short fluorescence lifetimes. Zn-P-Fc and Pd-P-Fc exhibit great reverse saturable absorption properties for 7 ns laser with 532 nm wavelength, and the β values are 13.36 and 13.41 cm/GW, respectively.

Full text of DOI:10.1016/j.ica.2020.119816

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Research paper
Synthesis, crystal structure and nonlinear optical properties of ferrocene-con‐
taining metalloporphyrins
Xuewei Huang, Fengli Wei, Fengqi Guo, Yanyan Zhu
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Reference:
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https://doi.org/10.1016/j.ica.2020.119816
ICA 119816
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Inorganica Chimica Acta
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18 November 2019
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4 June 2020
Please cite this article as: X. Huang, F. Wei, F. Guo, Y. Zhu, Synthesis, crystal structure and nonlinear optical
properties of ferrocene-containing metalloporphyrins, Inorganica Chimica Acta (2020), doi: https://doi.org/
10.1016/j.ica.2020.119816
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Synthesis, crystal structure and nonlinear optical properties of
ferrocene-containing metalloporphyrins
a Xuewei Huang, b Fengli Wei, a Fengqi Guo*, b Yanyan Zhu*
a Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou, Henan
450001, P. R.China
bCollege of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, P. R.China
______________________________________________________
*Corresponding author, E-mail address: fqguo@zzu.edu.cn, Tel: 8615538009000 (F. Guo);
zhuyan@zzu.edu.cn, Tel: 8615039066923 (Y. Zhu);

Abstract
Five ferrocene-containing metalloporphyrins (Pd-P-Fc, Co-P-Fc, Cu-P-Fc, Zn-P-Fc
and Ni-P-Fc) were synthesized and characterized. The crystal structure of Zn-P-Fc
determined by using the single crystal diffraction technique belongs to the triclinic
system. A typical aggregation of Zn-P-Fc occurs when the concentration of Zn-P-Fc
is greater than 2.0×10-6 mol/L in solution. The strong interaction between the
metalloporphyrin and the ferrocene group was inferred by the absorption spectra,
fluorescence spectra and the DFT calculation. Good nonlinear optical properties of
these materials were inferred from the low fluorescence quantum yields and the short
fluorescence lifetimes. Zn-P-Fc and Pd-P-Fc exhibit great reverse saturable absorption
properties for 7 ns laser with 532 nm wavelength, and the β values are 13.36 and
13.41 cm/GW, respectively.
Keywords: Ferrocene-containing metalloporphyrins; Crystal structure; Photophysical
properties; Nonlinear optical properties

1. Introduction
Nonlinear optical (NLO) materials have been attracting significant interests
because of its potential applications in optical limiting, three-dimensional optical data
storage, microscopy, photodynamic therapy, and optical switch [1-5]. Optical limiter
decreases transmittance when the intensity of laser beam is strong, and the
transmittance keeps high when the laser beam is weak. They can be used to protect
optically sensitive equipment or human eyes from laser-induced damage [6]. The
nonlinear optical phenomenon is the consequence of one or more nonlinear optical
processes, such as the reverse saturable absorption (RSA), multi-photon absorption,
optical self-focusing or self-defocusing, and the absorption of the photo-induced ionic
carrier. Currently, the organic nonlinear optical materials that were intensively studied
are the conjugated organic small molecules largely, among which
metallophthalocyanines and metalloporphyrins are the most promising ones due to
their fast response time and large RSA ability. The heavy atomic effect of the metal
ions and the large rigid -conjugated ligand system can enhance the intersystem
crossing (ISC) coefficient from the first excited singlet state (S1) to the first excited
triplet state (T1) due to the spin-orbital coupling, which facilitates the nonlinear
optical property, especially for the laser with nanosecond pulse width [7-9]. In
addition, the NLO properties of metalloporphyrins can be improved via inserting
different metals in the core or modifying the skeleton of the porphyrin ring with
suitable substituents [10-12].

The significant research conclusions of pioneering work for designing ascendant
NLO materials have been widely accepted. The molecules containing heavy transition
metallic ions and rigid conjugated structures generally have strong RSA ability, while
the organic molecules containing electronic pull-push groups generally have special
two-photon absorption property due to the metastable charge-transfer states. Several
groups, including ours, have designed some new types of materials containing the
above structural characteristics at the same time in order to obtain the nonlinear
optical materials with great RSA and multi-photon absorption synchronously [13-15].
However, most of the research works are still focusing on finding new types of the
materials with new or compositive nonlinear optical mechanisms.
Ferrocene and porphyrin derivatives exhibit good second-harmonic generation
(SHG) efficiency, and outstanding electron donating properties [16,17]. It has been
proved that the ferrocene group can induce the electron transfer from the ferrocene
group to the porphyrin ring after it is introduced into the peripheral position of the
porphyrin ring [18-21]. Although some porphyrins containing ferrocene group have
been synthesized and studied, their nonlinear optical properties are rarely reported
[22,23]. The detailed relationship between the structure of porphyrins and the
two-photon absorption, as well as the excited state absorption, has not been clearly
discussed. In addition, how the two-photon absorption and the excited state absorption
affect each other based on the structure of the complexes have also not been explicitly
discussed. To address these questions, a series of ferrocene-containing
metalloporphyrins were synthesized and characterized with the elemental analyses,

the nuclear magnetic resonance (NMR) and the matrix-assisted laser
desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), their basic
photophysical and nonlinear optical properties were also studied by using the
thermogravimetric analysis (TGA), UV-vis absorption spectra, fluorescence emission
spectra and the Z-scan techniques.
2. Results and discussion
2.1. Crystal Structures
The crystallographic data of Zn-P-Fc and the measuring conditions are
summarized in Table 1. The single-crystal X-ray diffraction pattern of Zn-P-Fc is
shown in Fig. 1 and the details of the crystal parameters and structural refinement as
well as all the bond lengths and angles are also listed in Table 1 and Tables S1-S2,
respectively. The single-crystal structure of Zn-P-Fc belongs to triclinic and space
group P , with a= 10.85(3) Å, b = 11.09 (4) Å, c = 26.54 (14) Å, α = 90.69 (19), β
1
= 93.17(11), γ = 93.99 (7), V = 3183 (22) Å3, Z = 2. Zn2+ ion was pulled 0.24 Å
above the N4 plane of porphyrin ring due to its large ionic radius, such phenomenon
is known as “doming” of the macrocyclic complexes. The average length of the Zn-N
coordination bond is 2.06 Å, and the axial position of Zn2+ ion is coordinated to the
oxygen atom of THF (O1), that results in a pyramid coordination polyhedron. The
porphyrin ring and ferrocene ring of each independent molecule are not coplanar,
thereby minimizing unfavourable steric interaction between the groups. The dihedral
angle between the porphyrins ring and peripheral phenyl groups at 5, 10 and 15
positions is 78.512(208), the dihedral angle between the two phenyl groups

connected to the two sides of the amido bond [-(CO)-NH-] is about 34.796(287),
and the dihedral angle between the cyclopentadiene of ferrocene and the phenyl group
connected to cyclopentadiene is about 19.167(303). The out of mean plane distortion
of the peripheral phenyl rings in the complex might be attributed to two factors i.e.
distortion of Zn2+ ion above the N4 plane and steric interactions between the
neighbouring phenyl protons and beta pyrrole protons [24]. The anisotropic and
isotropic displacement parameters of the single crystal of Zn-P-Fc are presented in
Tables S3-S4.
（Figure 1）
(Table 1)
2.2 Photophysical properties
The absorption spectra of 4-ferrocenylaniline (Fc-NH2), 5, 10, 15-triphenyl-20-
[4-(carboxy)-phenyl]-porphyrin (TPP-COOH) and the metal-free porphyrin-ferrocene
(P-Fc) in THF are presented in Fig. 2. The absorption spectrum of Fc-NH2 exhibits
two peaks at 255 nm ( = 1.48  104 Lmol-1cm-1) and 294 nm ( = 1.74  104
Lmol-1cm-1), respectively. The absorption spectrum of TPP-COOH shows an intense
peak at 417 nm, which could be attributed to the transition of a1u()  eg(*) (Soret
band), and four relatively weak peaks at 513, 548, 590 and 645 nm, which are
attributed to the transitions of a2u()  eg(*) (Corresponding to Qy(1, 0), Qy(0, 0),
Qx(1, 0) and Qx(0, 0) bands, respectively). The numbers in the parentheses are the
vibrational quantum numbers of the dominant vibrational model in the upper and
lower electronic states, respectively). The absorption spectrum of TPP-COOH is
consistent with that of the porphyrin derivatives of the pioneering works [25,26]. It is

obvious that the absorption spectrum of P-Fc sums up the absorption spectra of
Fc-NH2 and TPP-COOH, although the contribution of Fc-NH2 is very weak because
of the smaller molar extinction coefficient compared to that of TPP-COOH. This
phenomenon also reported in other metalloporphyrins jointing metallic complexes
[27].
(Figure 2)
The absorption spectra of P-Fc and the five metalloporphyrin-ferrocene
complexes (M-P-Fc) in THF are shown in Fig. 3 and the locations of the absorption
maxima are also listed in Table 2. The absorption spectra of the
metalloporphyrin-ferrocene complexes exhibit one Soret band and either one or two Q
bands. The red-shifts of the Soret and Q bands of Zn-P-Fc occurred clearly, and the Q
bands reduce to two peaks, which are attributed to the Qx(1, 0) and Qx(0, 0)
transitions, respectively, compared to those of P-Fc. The coordination of the Co2+,
Ni2+, Cu2+ and Pd2+ ions with P-Fc made the Soret and Q bands blue shifted slightly.
The peaks of the Q band of M-P-Fc reduce due to the increasing of the symmetry in
the molecular structure of M-P-Fc relative to that of P-Fc after the metal ion
coordinated to the four N atoms of the porphyrin. In general, the longer wavelength of
the location of the Q band infers the weaker stability of the metal porphyrin. It can be
seen from Table 2 that the sequence of the stabilities of title compounds is Pd-P-Fc >
Ni-P-Fc > Co-P-Fc > Cu-P-Fc > Zn-P-Fc. This result is consistent with the pioneering
work [28,29].
(Figure 3)
The fluorescence spectra of P-Fc, Co-P-Fc, Zn-P-Fc and Pd-P-Fc are shown in

Fig. 4, and the locations of their peaks, the lifetimes as well as the fluorescence
quantum yields relative to tetraphenylporphyrin zinc (ФF = 0.033 in toluene)[30] are
also listed in Table 2. It is clear that all the fluorescence spectra exhibit two peaks, the
former is attributed to the Q(0–0) transition and the latter to the Q(0–1) transition
[31]. As listed in Table 2, the lifetimes corresponding to the two peaks of every
complex are between 1 to 5 nanoseconds and almost the same. In addition, the similar
emission spectra are collected whatever the different Q and/or B bands are used as the
excited wavelength, which indicates that the emission should be the fluorescence and
attribute to the transition from the first singlet excited state to the ground state.
However, the fluorescence spectra of Cu-P-Fc and Ni-P-Fc aren't detectable under the
same experimental conditions. It should be the outcome of the paramagnetism of the
Cu2+ and Ni2+ complexes [32,33]. The coordination of Zn and Pd ions makes the
fluorescence blue shifted compared to that of P-Fc, and the contour of the
fluorescence spectrum of Co-P-Fc is almost as same as that of P-Fc. The fluorescence
quantum yields of all the metalloporphyrin-ferrocene complexes are much lower than
that of P-Fc, it is because that the coordination of the transition metal ions increases
the intersystem crossing coefficient of the molecules from the first singlet excited
state to the first triplet excited state [34], which is also verified by the shorter
fluorescence lifetimes of the metalloporphyrin-ferrocene complexes than P-Fc. The
fluorescence lifetimes of the metalloporphyrin-ferrocene complexes are all less than 3
ns, which are shorter than that of the nonmetalated porphyrin P-Fc (4.3 ns). The
lifetime of the intermediate, TPP-COOH, is about 15.7 ns, which is 11.4 ns longer

than the fluorescence lifetimes of P-Fc. It infers that the introduction of the ferrocene
group into porphyrin decreases the fluorescence lifetime of the porphyrin. The results
reveal the strong interaction between the ferrocene group and the porphyrin ring. The
strong interaction of the porphyrin with the ferrocene group and different transition
metallic ions affects the properties of complexes strongly, which is beneficial for the
molecules to form sub-stable states and enhance the nonlinear optical properties [35].
Similar properties have been found in other metalloporphyrins jointing metallic
complexes [27].
(Figure 4)
(Table 2)
To study the aggregation property of the title complexes in solution, the
excitation spectra of Zn-P-Fc with different concentrations in THF are collected. As
shown in Fig. 5, the excitation spectrum of Zn-P-Fc exhibits two Q bands and a Soret
band when the concentration is low, this is in accord with its UV-Vis absorption
spectrum. The Soret band gradually splits into two peaks when the concentration of
Zn- P-Fc is greater than 2.0×10-6 mol/L, which indicates that the typical aggregation
of Zn-P-Fc occurs. To explain the experimental phenomenon, the absorption spectra
of the metalloporphyrin-ferrocene complexes were calculated using density functional
theory (DFT) with Gaussian 09 software package program [36], and the contributions
of different transitions to the absorption spectrum were also calculated with SWizard
software [37,38]. The Soret band in the absorption spectrum of Zn-P-Fc is the
compositive result of several transitions, in which the main contributions of the

transitions HOMO-2LUMO+1, HOMOLUMO, HOMO-4LUMO, HOMO
LUMO+2 and HOMO-4LUMO+1 are 36%, 22%, 16%, 12% and 10%,
respectively. The interaction between Zn-P-Fc molecules is small and the molecules
move freely in solution when the concentration of Zn-P-Fc is below 2.0×10-6 mol/L,
so all the absorptions of different transitions are mixed together. However, when the
concentration of Zn-P-Fc in solution is higher than 2.0×10-6 mol/L, the strong
-packing interaction between the porphyrin molecules makes the molecules
aggregated and the originally merged absorptions are separated. The similar critical
aggregation also has reported in other literature corresponding to metalloporphyrins
[39,40].
(Figure 5)
2.3 Quantum Mechanics Calculations
To explore the properties of P-Fc and M-P-Fc, the geometries were optimized
and the molecular orbitals of them were also calculated using the density functional
theory (DFT). The mixed basis sets of 6-31g (d, p) for C, H, O, N atoms and Lanl2DZ
for Fe, Co, Ni, Cu, Zn and Pd atoms were selected. All the calculations were
performed with the Gaussian 09 software package [36]. The electronic density
distributions of HOMO and LUMO orbitals of P-Fc and M-P-Fc are shown in Fig. 6,
and the calculated energy levels, as well as the energy gaps (Eg) between HOMO and
LUMO, are also listed in Table 3. It can be seen that the HOMO and LUMO of P-Fc
are dominated by the ferrocene and porphyrin groups, respectively, a clear charge

transfer from the ferrocene to the porphyrin group happens when the molecule is
excited. The HOMOs of all the M-P-Fc complexes are dominated by the porphyrin
ring. The LUMOs of all the M-P-Fc are also dominated by the porphyrin ring with
little contribution of the central metal ions, and a charge transfer from the porphyrin
ring to the central metal ion occurs when the molecules are excited excepted Zn-P-Fc,
it may be the outcome of the low electrode potential of Zn2+/Zn.
(Figure 6)
(Table 3)
The Eg values of the complexes are following the sequence of Co-P-Fc >
Ni-P-Fc > Pd-P-Fc > Zn-P-Fc > Cu-P-Fc > P-Fc.
2.4 Thermo-gravimetric analysis
The thermostabilities of P-Fc and M-P-Fc were investigated using thermo-
gravimetric analysis (TGA). As shown in Fig. 7, the P-Fc and all the
metalloporphyrins are stable without much weight loss up to 200 ºC under argon
atmosphere, a slow solvents removal occurs between 200 and 250 ºC, which is
coincident with the reported similar metalloporphyrins [41]. A large weight loss of
13% ~25% happens between 250 and 500 ºC, which should be due to the pyrolysis of
the carbon skeleton of the ferrocene (theoretical weight loss 12.6% ~ 14.1%). This
result shows that the stability of the title complexes is pretty good for the application
as nonlinear optical materials.
(Figure 7)

2.5 Nonlinear optical properties
2.5.1 Solvatochromism method for determining first-order polarizabilities
The first-order polarizability (βxxx) of organic molecules can be determined by
the solvatochromism method [42,43]. The simple expression of the first-order
polarizability is shown in Equation (1)：
2
2
2
2
βxxx(2ω) = 3휇푒푔 휇푒 ― 휇푔 휔푒푔 /2h2(휔푒푔 ― ω2)(휔푒푔 ―4ω2)
(
)
(1)
where h is Planck’s constant (in ergs), μeg is the transition dipole moment between the
ground state and the excited state, μg and μe are the permanent dipole moments of the
ground state and the excited state, respectively, and ω is the laser frequency, ωeg is the
frequency of the transition from the ground state to the first excited state. According
to the general quantum mechanics, ωeg can be obtained from the area of the absorption
band using Equation (2).
area = ∫휀′푀푑휔 = 2πωeg푁퐴푛휇푒푔2M/3(2.303)ε0푐ℎ
(2)
where M is the molar concentration of the sample, NA is Avogadro’s constant, n is the
refractive index of the solvent, ' is the molar extinction coefficient of the sample, ε0
is the permittivity of vacuum, c is the speed of light in vacuum, and the integral is
over the entire absorption band. The value of μe-μg could be derived from Equations
(3)-(5) [43].
(3)
(4)
νa ― νf = 퐴 + 퐵(퐵퐾)
2
3
(
)
B = 2 휇푒 ― 휇푔 /ℎ푐푎

2
푛 ― 1
)
(
(휀 ― 1)
―
[
(2휀 + 1)
2
2푛 + 1
)
]
(
(5)
BK = [
2
2
(푛
― 1
)
(휀 ― 1)
1 ― (2푛 + 1 1 ―
[
]
2
]
(2휀 + 1)
)
where νa-νf is the Stokes shift in wave number. a is the radius of a spherical cavity
occupied by the molecule in the solvent. ε is the dielectric constant of the solvent. n is
the refractive index of the solvent. BK is the Bilote-Kawski value of the solvent. The
parameters of P-Fc, Co-P-Fc, Zn-P-Fc and Pd-P-Fc in five different solvents are listed
in Tables 4 and 5. The first-order polarizabilities |βxxx| of them are finally calculated
by substituting the values of μeg, ωeg, μe and μg into Equation (1).
(Table 4)
(Table 5)
It can be seen from Table 4, slight blue shifts of absorption spectra and
remarkable increases of Stokes shifts are observed when the polarity of the solvent
changes from non-polar to polar solvent, which indicates that the polarity of all the
molecules in the ground states is larger than that in the excited states and the efficient
intra-molecular charge transfer occurred from the donor to the acceptor groups. The
good linear relationship between the Stokes-Shifts of the title complexes and the BK
values of the solvents (Figs. S1-S4) indicate the strong dipole-dipole interactions
between solvent and solute molecules [44].
As listed in Table 5, the first-order hyperpolarizabilities of the P-Fc, Co-P-Fc,
Zn-P-Fc and Pd-P-Fc are between 0.25×10-29 and 3.01×10-29 esu, which is similar to
that of 4-nitro-N,N-dimethylaniline (|βxxx|=37×10-30 esu) [45]. The insertion of metal
ions increases the first order hyperpolarizability of porphyrins. Although the effect of

different metal ions on the first-order hyperpolarizabilities of the synthesized
metalloporphyrin-ferrocene complexes is still not clear because of the experimental
error of solvatochromism method for determining the first-order polarizabilities, the
large first-order hyperpolarizabilities still make them prospective to develop organic
second harmonic (SHG) materials.
2.5.2 Nonlinear absorption properties
The low fluorescence quantum yields and the strong interaction between the
ferrocene group and porphyrin ring infer that these materials maybe of good nonlinear
optical properties, so the nonlinear absorption properties of these materials were
measured with a 532 nm-wavelength and 7 ns laser in DMF using the open aperture
Z-scan technology.
(Figure 8)
Fig. 8 shows the open aperture Z-scan traces and the theoretical fitting curves
according to Equation (6) (Experimental section) of the six synthesized complexes.
The best fit of the experimental data of every complex yields the effective excited
state absorption cross-section. The effective excited state absorption cross-sections,
the ground state absorption cross-sections, the ratios of δe/δg and the effective excited
state absorption coefficients () of the complexes are listed in Table 6. It can be seen
from Fig. 8 that the normalized transmittance increases with the increasing of the
on-axis laser intensity for Ni-P-Fc, and the ratio of δe/δg in DMF is less than 1, which
indicate a clear saturable absorption mechanism, the population of the molecules in

the ground-state is depleted when the incident pulse intensity is high and the
molecules at excited state cannot return to the ground state in time [46]. For the other
complexes, the transmittances decrease with the increasing of the on-axis laser
intensity and reach minimum values when the samples are at the focus position of the
lens. The normalized transmittances decrease to 82%, 64%, 38%, 31% and 24% for
Cu-P-Fc, Co-P-Fc, Pd-P-Fc, Zn-P-Fc and P-Fc, respectively, at the focus point of the
lens. These may be attributed to the two-photon absorption (TPA), excited state
absorption (ESA), free carrier absorption, and/or the reverse saturable absorption
(RSA). In general, the mechanism of the optical nonlinear absorption of
metalloporphyrins under the effect of nanosecond pulse laser should be the reverse
saturable absorption, and can be explained using the five level energy diagram
[47,48]. The molecules are excited from the ground state (S0) to the first singlet
excited state (S1) after absorbing a photon. The molecules at the first singlet excited
state can be excited to the second singlet excited state (S2) by absorbing another
photon. However, this process does not deplete the population of S1 because of the
picoseconds-short lifetime of S2 in the nanosecond time scale. The molecules at S1
also can transfer to the first triplet excited state (T1) via intersystem crossing (ISC),
and the transition from T1 to T2 maybe occur when the lifetime of T1 is longer than
the pulse width of the laser, which maybe results in the RSA if the absorption cross
section of T1 is greater than that of the S0 [48]. The pulse width of the laser in our
experiments is 7 ns, which is much shorter than the lifetime of T1 of metalloporpyrins
[49,50]. It can be seen from Table 6 that the effective excited state absorption

cross-sections of this kind of complexes are larger than the ground state absorption
cross-sections except for Ni-P-Fc, the effective excited state absorption cross-sections
of P-Fc, Zn-P-Fc and Pd-P-Fc are 17.40, 15.06 and 8.92 times bigger than their
ground state absorption cross-sections, respectively. For metalloporphyrins, the short
fluorescence lifetime generally indicates high quantum yield of the intersystem
crossing, which is coincident with the experimental data of δe/δg. The large values of
δe/δg and short fluorescence lifetimes are expected to make significant contribution to
triplet-triplet excited states absorption.
(Table 6)
The calculated nonlinear absorption coefficients (β) of P-Fc, Zn-P-Fc, Pd-P-Fc
Co-P-Fc and Cu-P-Fc are 11.18, 13.36, 13.41, 1.29 and 0.21 cm/GW, respectively.
The large nonlinear absorption coefficients of Zn-P-Fc and Pd-P-Fc can be attributed
to the low electrochemical redox potential for Zn2+/Zn and the high electrochemical
redox potential for Pd2+/Pd, which boosts the LMCT(Ligand to Metal Charge
Transfer) and MLCT(Metal to Ligand Charge Transfer) respectively. Co-P-Fc and
Cu-P-Fc show weak nonlinear absorption properties compared to P-Fc, Zn-P-Fc and
Pd-P-Fc. Especially for Ni-P-Fc, the saturated absorption happened under our
experimental conditions, the similar experimental results have been reported in other
literatures [51,52]. The experimental results infer that the introduction of the
ferrocene and different metal ions has significant effect on the NLO behavior of the
metalloporphyrin-ferrocene complexes.

3. Conclusions
In summary, a new ferrocene-containing porphyrin (P-Fc) and its five metallic
complexes were synthesized and characterized detailedly. The thermo-stabilities of
them are pretty good below 200 C. The crystal structure of Zn-P-Fc determined
using the single crystal diffraction technique belongs to the triclinic system. A typical
aggregation of Zn-P-Fc occurs when the concentration of Zn- P-Fc is greater than
2.0×10-6 mol/L in solution, which induces the mixing of different transitions and is
testified by the calculation results. The strong interaction between the
metalloporphyrin and ferrocene group is inferred by the absorption spectra,
fluorescence spectra, as well as the DFT calculation. The low fluorescence quantum
yields, short fluorescence lifetimes and strong interaction between ferrocene group
and porphyrin ring indicate good nonlinear optical properties of these materials.
Zn-P-Fc and Pd-P-Fc exhibit great reverse saturable absorption, and the β values are
13.36 and 13.41 cm/GW, respectively.
4. Experimental Section
Materials:
Methyl-4-formyl
benzoate,
benzaldehyde,
pyrrole,
4-dimethylaminopyridine (DMAP), boron trifluoride etherate, 2,3-dichloro-5,6-
dicyano-1,4-benzoquinone (DDQ), N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide
hydrochloride (EDCI), 4-nitroaniline and ferrocene were commercially available
products and used without further purification. All the solvents were dried and
distilled via the standard methods prior to use. 4-ferrocenylaniline (Fc-NH2) was

synthesized following the literature procedure [53]. 5,10,15-Triphenyl-20-
[4-(methoxycarbonyl) phenyl]-porphyrins (TPP-COOMe) was synthesized using the
Lindsey method [54-56]. Then TPP-ester was hydrolyzed in the presence of
potassium hydroxide to afford the desired 5,10,15-Triphenyl-20-[4-(carboxy)phenyl]-
porphyrin (TPP-COOH) [57]. The synthetic processes of the title compounds are
outlined in Scheme 1.
Synthesis of 5, 10, 15-Triphenyl-20-[4′-(amidophenylferrocene)phenyl]-
porphyrin [25,26]: 5,10,15-triphenyl-20-[4-(carboxyl)-phenyl]porphyrin (1.00 g,
1.52 mmol) was dissolved in tetrahydrofuran (160 mL), then the solution was cooled
to around 0°C. Then EDCI （0.58 g, 3.04 mmol）and DMAP （0.19 g, 1.52 mmol）
were added to the solution, and the resulting mixture was stirred for 1h. After
4-ferrocenylaniline (0.51 g, 1.82 mmol) was added, the solution was heated to 40°C
and stirred overnight. After the reaction was finished, the organic solvent was
evaporated in vacuo. The residue was treated with dichloromethane (120 mL) and the
solution was extracted with distilled water three times. The organic phase was dried
over with anhydrous Na2SO4. After the organic solvent was removed, the crude
compound was purified by column chromatography on silica gel with petroleum
ether: CH2Cl2 (1:10 v/v) as eluent. The title product was collected as purple solid.
(Yield: 67%)
1H NMR (600 MHz, CDCl3) (Fig. S5)： δ 8.92 – 8.84 (m, 6H), 8.81 (d, J = 4 Hz, 2H),
8.34 (d, J = 8 Hz, 2H), 8.26 (d, J = 8 Hz, 2H), 8.21 (d, J = 7 Hz, 6H), 8.11 (s, 1H),
7.76 (m, J = 14, 7 Hz, 9H), 7.71 (d, J = 8 Hz, 2H), 7.55 (d, J = 8 Hz, 2H), 4.67 (s, 2H),

4.33 (s, 2H), 4.07 (s, 5H), 2.76 (s, 2H). MALDI-TOF-MS (Fig. S6): m/z 918.2892 for
[M + H]+, calcd. 917.2817. Anal. calcd. for C61H43FeN5O.H2O : C 78.28, H 4.81, N
7.48; found: C 78.47, H 4.23, N 7.08.
(Scheme 1)
General process for synthesizing metalloporphyrins [58-61]: 2-10 equiv. of
the corresponding metal acetate was added to the solution of P-Fc in
dimethylformamide (DMF) or the mixture of tetrahydrofuran (THF) and methanol
(MeOH) and refluxed for about 2 h. The absorption spectrum of the free-base
porphyrin during the reaction progress was monitored using UV-vis spectrometer.
After the reaction was finished, the mixture was cooled to room temperature, and the
solvent was removed under vacuum. To the residue, a certain amount of
dichloromethane was added and extracted with water for several times, and then the
organic phase was dried over anhydrous sodium sulphate. After the solvent was
removed, the crude product was purified by column chromatography on a silica
1
column using CH2Cl2 as eluant. However, the HNMR spectra of (Co-P-Fc) and
(Cu-P-Fc) weren’t collected due to the paramagnetism of copper and cobalt
complexes, and the similar phenomenon has been reported in other literatures [32].
5,10,15-Triphenyl-20-[4-(amidophenyl-4'-ferrocene)phenyl]porphyr-inatocobalt
(II) (Co-P-Fc): MALDI-TOF-MS (Fig. S7): m/z 974.2017 for [M]+, calcd. 974.1993.
Anal. calcd for C61H41FeN5OCo.2H2O: C 72.48, H 4.49, N 6.93; found: C 72.35, H
4.79, N 6.44.
5,10,15-Triphenyl-20-[4-(amidophenyl-4'-ferrocene)phenyl]porphyrinatonickel

(II) (Ni-P-Fc): 1H NMR (400 MHz, CDCl3) (Fig. S8): δ 8.78 (m, 6H), 8.76 – 8.72 (m,
2H), 8.26 – 8.16 (m, 4H), 8.10 (s, 1H), 8.07 – 8.01 (m, 6H), 7.72 (m, 11H), 7.58 –
7.56 (d, 2H), 4.72 – 4.69 (s, 2H), 4.38 – 4.35 (s, 2H), 4.10 (s, 5H). MALDI-TOF-MS
(Fig. S9): m/z 973.2010 for [M]+, calcd. 973.2014. Anal. calcd. for
C61H41FeN5ONi.H2O: C 73.81, H 4.37, N 7.06; Found: C 74.00, H 4.50, N 6.52.
5,10,15-Triphenyl-20-[4-(amidophenyl-4'-ferrocene)phenyl]porphyrinatocopper
(II) (Cu-P-Fc) ： MALDI-TOF-MS (Fig. S10): m/z 979.2006 for [M+H]+; calcd
978.1957. Anal. calcd for C61H41FeN5OCu: C 74.81, H 4.22, N 7.15; found: C 74.82,
H 4.53, N 6.89.
5,10,15-Triphenyl-20-[4-(amidophenyl-4'-ferrocene)phenyl]porphyrinatozinc(II)
(Zn-P-Fc): 1H NMR (600 MHz, DMSO-d6) (Fig. S11): δ 10.59 – 10.55 (s, 1H), 8.74
(d, J = 18 Hz, 8H), 8.34 – 8.26 (m, 4H), 8.13 (d, J = 5 Hz, 6H), 7.86 – 7.80 (m, 2H),
7.75 (m, 9H), 7.58 – 7.52 (d, 2H), 4.75 (s, 2H), 4.29 (s, 2H), 4.00 (s, 5H).
MALDI-TOF-MS (Fig. S12): m/z 979.1960 for [M]+, calcd 979.1952. Anal. calcd for
C61H41FeN5OZn.2H2O: C 72.02, H 4.46, N 6.88; found: C 72.33, H 4.02, N 6.38.
5,10,15-Triphenyl-20-[4-(amidophenyl-4'-ferrocene)phenyl]porphyrinatopalladi
1
um(II) (Pd-P-Fc): H NMR (400 MHz, CDCl3) (Fig. S13): δ 8.85 (m, 6H), 8.83 –
8.78 (m, 2H), 8.38 – 8.32 (m, 2H), 8.32 – 8.26 (m,2H), 8.23 – 8.17 (m, 6H), 8.15 –
8.12 (m, 1H), 7.85 – 7.72 (m,11H), 7.62 – 7.59 (m, 1H), 7.59 – 7.56 (m, 1H), 4.77 –
4.69 (s, 2H), 4.41 – 4.35 (s, 2H), 4.12 (s, 5H). MALDI-TOF-MS (Fig. S14): m/z
1021.1721 for [M]+, calcd 1021. 1695. Anal. calcd for C61H41FeN5OPd.H2O: C
70.43, H 4.17, N 6.73; found: C 70.00, H 3.60, N 6.22.

General information: Nuclear magnetic resonance (NMR) spectra were
recorded with 400 MHz or 600 MHz Bruker AVIII HD (Bruker, Switzerland). The
high-resolution mass spectra were measured on a Waters SYNAPT G2-Si mass
spectrometer with MALDI-TOF-Q II system and α-cyano-4-hydroxycinnamic acid as
the main matrix. The elemental analyses were detected on a Vario EL III instrument
(Elementar, Germany). Thermogravimetric analysis (TGA) was performed using a
STA 409 PC (NETZSCH, German) by heating the samples from 30 °C to 600 °C with
a heating rate of 10 °C·min-1 under argon atmosphere. UV-vis absorption spectra
were studied on a UV-vis spectrophotometer (UV-5200PC, UNICO, China).
Fluorescence spectra were collected on a F97 Pro fluorescence spectrometer
(Lengguang Tech, China). The emission lifetime was determined on a FLS980
spectrometer, in which the TCSPC laser (EPLED-330, =332.6 nm, = 937.6 ps, EI,
England) was used as the excitation source, and the data was analyzed by exponential
curve fitting.
X-Ray Crystallography: The single crystal for the X-ray diffraction
measurement was obtained by slow solvent evaporation of the solution of Zn-P-Fc in
tetrahydrofuran/hexane = 4:1. The X-Ray diffraction data of Zn P-Fc was collected on
a Bruker smart Apex CCD II diffractometer using graphite monochromated Mo-Kα (λ
= 0.71073 Å) radiation at room temperature. All data were collected at room
temperature using the ω-2θ scan technique and corrected based on
Lorenz-polarization effects. The structure of Zn-P-Fc was solved by the direct
methods and expanded using the Fourier technique. The hydrogen atoms on C were

positioned geometrically and refined using a riding model. The hydrogen atoms on O
were found at reasonable positions in the differential Fourier map and located there.
All the hydrogen atoms were included in the final refinement. All calculations were
performed using the OLEX-2 crystallographic software package.
Z-Scan measurement: The Z-scan technique was used to evaluate the
third-order nonlinear optical susceptibility of the title complexes in solution. The
Z-scan experimental set-up is shown schematically in Fig. 9. This technique enables
measurement of the nonlinear refraction (NLR) and the nonlinear absorption (NLA)
simultaneously [35,62,63]. The initial laser beam is divided into two beams by a beam
splitter BS1 after passing through an energy attenuator, and the reflection part is
received by the detector D1 to monitor the fluctuation of the incident pulse energy.
The laser beam passing through BS1 is tightly focused and then is divided into two
parts by the beam splitter BS2 behind the focus, and the reflected part is all received
by the detector D2, while the transmitted part is received by the detector D3 after
passing through an aperture. The output laser energies were noted using a Laser Probe
Rj-7620 energy ratio-meter with two pyroelectric detectors. The solution of the
sample was placed in a 2-mm thick quartz cell near the focus. The energy of the laser
beams after passing through the sample with and without the aperture was monitored
when the sample moved through the focal plane along the Z-axis. A Q-switched,
frequency doubled Nd:YAG laser (Beamtech Optronics Co., Ltd., Dawa-200)
producing a 532 nm laser beam with 7 ns pulse width and repetition rate of 10Hz was
used as the laser resource, and the output of the laser beam had a nearly Gaussian

intensity profile. The Gaussian laser beam was focused by a lens with 25 cm focal
length. The resulting beam waist of the focused spot was found to be 33 m (0), the
2
corresponding Rayleigh length, calculated using the formula Z0 = 0 /, was found
to be 6.43 mm. The sample thickness is less than the Rayleigh length, hence the thin
sample approximation is valid [64].
(Figure 9)
All the metalloporphyrins in DMF with the concentration of 5×10-5~1×10-3
mol/L were used for the Z-scan measurement. The effective nonlinear absorption
coefficients β were calculated using the theory reported previously [62,63,65]. The
normalized transmission of the open aperture Z-scan, which is mainly contributed by
the excited state absorption δe, can be expressed by the following Equation (6):
1 + x2
T(Z) =
ln [1 + q /(1 + x2)]
0
(6)
[
]
q0
Where x=Z/Z0, Z is the distance from the sample to the focus, and Z0 is the Rayleigh
2
πω0
length,
.
= 6.43 mm
Z0 =
λ
(7)
q0 = ασeF0Leff/2ℏω
In which  is the angular frequency of the laser. F0 is the on-axis fluence at the focus,
2, ω0 is the
which is related to the incident laser energy
by
F0 = 2Etotal/πω0
Etotal
beam waist, Leff = (1-e-L)/, α is the linear absorption coefficient of the sample, L is
the length of the sample.
The linear absorption coefficient α of the sample can be obtained from the
following equation:  = 10-3gNAC, where C is the molar concentration of the sample,
NA is the Avogadro constant and σg is the absorption cross-sectional area of the

ground state of the sample.
The value of q0 can be obtained by fitting the experimental data of the open
aperture Z-scan with Equation (8), and then the value of the excited state absorption
sectional area of the target molecule, σe, can be calculated out according to the
Equation (9). Finally, the nonlinear absorption coefficient of β can be calculated out
based on the value of σe.
[CCDC 1856611 contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.]
Supporting Information
Supporting Information is available.
Acknowledgement
The authors are grateful to Prof. Zhaoxun Lian of School of Chemistry and
Chemical Engineering, Henan Institute of Science and Technology for letting us using
his experimental facilities.
Reference
[1]. L.W. Tutt, A. Kost, Nature 356 (1992) 225-226. (DOI: 10.1038/356225a0)
[2]. D.A. Parthenopoulos, P.M. Rentzepis, Science 245 (1989) 843-845. (DOI ：
10.1126/science.245.4920.843)
[3]. F. Helmchen, W. Denk, Nat. Methods 2 (2005) 932-940. (DOI:
10.1038/nmeth818)
[4]. J.D. Bhawalkar, N.D. Kumar, C.F. Zhao, P.N. Prasad, J. Clin. Laser Med. Surg.

15 (1997) 201-204. ( DOI: 10.1089/clm.1997.15.201)
[5]. M. Kauranen, A.V. Zayats, Nature Photon 6 (2012) 737-748. (DOI:
10.1038/nphoton.2012.244)
[6]. Y. Chen, L. Gao, M. Feng, L. Gu, N. He, J. Wang, Y. Arakic, W.J. Blaub, O. Ito,
Mini-Rev. Org. Chem. 6 (2009) 55-65. ( DOI: 10.2174/157019309787316166)
[7]. J. Zhao, W. Wu, J. Sun, S. Guo, Chem. Soc. Rev. 42 (2013) 5323-5351. (DOI:
10.1039/C3CS35531D)
[8]. K. McEwan, K. Lewis, G.-Y. Yang, L.-L. Chng, Y.-W. Lee, W.-P. Lau, K.-S.
Lai, Adv. Funct. Mater. 13 (2003) 863-867. (DOI:10.1002/adfm.200304288)
[9]. W. Blau, H. Byrne, W.M. Dennis, J.M. Kelly, Opt. Commun. 56 (1985) 25-29.
(DOI: 10.1016/0030-4018(85)90059-8)
[10].
USA, 6 (2003) 44-131.
[11].
K.M Kadish, K.M. Smith, R. Guilard, The Porphyrin Handbook, New York,
M.O. Senge, M.E. Fazekas, E.G.A. Notaras, W.J. Blau, M. Zawadzka, O.B.
Locos, E.M.N. Mhuircheartaigh, Adv. Mater. 19 (2007) 2737-2774. (DOI:
10.1002/adma.200601850)
[12].
K.S. Suslick, C.T. Chen, G.R. Meredith, L.T. Cheng, J. Am. Chem. Soc. 114
(1992) 6928-6930. (DOI: 10.1021/ja00043a055)
[13].
G. Zhou, X. Wang, D. Wang, C. Wang, Z. Shao, Q. Fang, M. Jiang, Opt.
Commun. 190 (2001) 345-349. (DOI: 10.1016/S0030-4018(01)01058-6)
[14].
D. Yao, H. Wang, J. Guo, T. Wang, L. Zhang, J. Shao, F. Guo, J. Organomet.
Chem. 752 (2014) 6-11. (DOI: 10.1016/j.jorganchem.2013.11.032)

[15].
P. Xie, L. Wang, Z. Huang, F. Guo, Q. Jin, Eur. J. Inorg. Chem. 15 (2014)
2544-2551. (DOI:10.1002/ejic.201402043)
[16].
M.L.H. Green, S.R. Marder, M.E. Thompson, J.A. Bandy, D. Bloor, P.V.
Kolinsky, R.J. Jones, Nature 330 (1987) 360-362. (DOI: 10.1038/330360a0)
[17].
M.J. Frampton, H. Akdas, A.R. Cowley, J.E. Rogers, J.E. Slagle, P.A. Fleitz,
M. Drobizhev, A. Rebane, H.L. Anderson, Org. Lett. 7 (2005) 5365-5368. (DOI:
10.1021/ol0520525)
[18].
C. Bucher, C.H. Devillers, J.C. Moutet, G. Royal, E. Saint-Aman, Coord.
Chem. Rev. 253 (2009) 21-36. (DOI: 10.1016/j.ccr.2007.11.025)
[19].
H. Nakagawa, K. Ogawa, A. Satake, Y. Kobuke, Chem. Commun. 14 (2006)
1560-1562. (DOI: 10.1039/B518332D)
[20].
J. Rochford, A.D. Rooney, M.T. Pryce, Inorg. Chem. 46 (2007) 7247-7249.
(DOI: 10.1021/ic0703326)
[21].
H. Imahori, K. Tamaki, D.M. Guldi, C. Luo, M. Fujitsuka, O. Ito, Y. Sakata,
S. Fukuzumi, J. Am. Chem. Soc. 123 (2001) 2607-2617. (DOI:
10.1021/ja003346i)
[22].
F.D. Souza, P.M. Smith, S. Gadde, A.L. McCarty, M.J. Kullman, M.E.
Zandler, M. Itou, Y. Araki, O. Ito, J. Phys. Chem. B 108 (2004) 11333-11343.
(DOI: 10.1021/jp0485688)
[23].
G.N. Lim, E. Maligaspe, M.E. Zandler, Chem. Eur. J. 20 (2014)
17089-17099. (DOI: 10.1002/chem.201404671)
[24].
P. Dechan, G.D. Bajju, P. Sood, U.A. Dar, J. Mol. Struct. 1183 (2019) 87-99.

(DOI: 10.1016/j.molstruc.2019.01.064)
[25].
J. Matsumoto, T. Matsumoto, Y. Senda, T. Shiragami, M. Yasuda, J.
Photochem. Photobiol. A: Chem. 197 (2008) 101-109. (DOI:
10.1016/j.jphotochem.2007.12.010)
[26].
A.M. Gazzali, L. Colombeau, P. Arnoux, H.A. Wahab, C. Frochot, R.
Vanderesse, S. Acherar, Tetrahedron 73 (2017) 532-541. (DOI:
10.1016/j.tet.2016.12.037)
[27].
T.H.O. Leite, G. Grawe, J. Honorato, B.N. Cunha, O.R. Nascimento, P.S. de
Vargas, C. Donatoni, K.T. Oliveira, J.M.S. Lopes, N.M.B. Neto, W.C. Moreira,
L.R. Dinelli, A.A. Batista, Inorg. Chem. 58 (2019) 1030-1039. (DOI:
10.1021/acs.inorgchem.8b01032)
[28].
[29].
J.E. Falk, Porphyrins and Metalloporphyrins, Elsevier Pub. Co., 1964, p34.
H.P. Tao, H.S. Yu, West China J. Pharm. Sci. 10 (1995) 15-18. (DOI:
10.13375/j.cnki.wcjps.1995.01.005)
[30].
M.C. Yoon, S. Lee, S. Tokuji, H. Yorimitsu, A. Osuka, D. Kim, Chem. Sci. 4
(2013) 1756-1764. (DOI: 10.1039/C3SC22151B)
[31].
B. Minaev, M. Lindgren, Sensors 9 (2009) 1937-1966. (DOI:
10.3390/s90301937)
[32].
Y. Fang, Y.G. Gorbunova, P. Chen, X. Jiang, M. Manowong, A.A.
Sinelshchikova, Y.Y. Enakieva, A.G. Martynov, A.Y. Tsivadze, A.
Bessmertnykh-Lemeune, C. Stern, R. Guilard, K.M. Kadish, Inorg. Chem. 54
(2015) 3501-3512. (DOI: 10.1021/acs.inorgchem.5b00067)

[33].
M.K. Chahal, M. Sankar, R.J. Butcherb, Phys. Chem. Chem. Phys. 19 (2017)
4530-4540. (DOI: 10.1039/C6CP08396J)
[34].
A. Harriman, J. Chem. Soc. Faraday Trans. I 77 (1981) 369-377.
(DOI: 10.1039/F19817700369)
[35].
S.U. Hassan, F. Nawaz, Z.U.H. Khan, A. Firdous, M.A. Farid, M.S. Nazir,
Opt. Mater. 86 (2018) 106-112. (DOI:10.1016/j.optmat.2018.09.036)
[36].
M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji,
M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L.
Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida,
T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery, Jr.J.E.
Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N.
Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene,
J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L.
Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J.
Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J.
Cioslowski, and D.J. Fox, Gaussian 09, Revision D.01, Gaussian, Inc.,
Wallingford CT, USA, 2013.
[37].
S.I. Gorelsky, SWizard program, http://www.sg-chem.net/, University of
Ottawa, Ottawa, Canada, 2013.

[38].
S.I. Gorelsky, A.B.P. Lever, J. Organomet. Chem. 635 (2001) 187-196.
(DOI: 10.1016/S0022-328X(01)01079-8)
[39].
R.J. Abraham, F. Eivazi, H. Pearson, K.M. Smith, J. Chem. Soc. Chem.
Commun. 17 (1976) 699-701. (DOI: 10.1039/C39760000699)
[40].
J. Karolczak, D. Kowalska, A. Lukaszewicz, A. Maciejewski, R.P. Steer, J.
Phys. Chem. A 108 (2004) 4570-4575. (DOI: 10.1021/jp049898v)
[41].
A. Fateeva, S. Devautour-Vinot, N. Heymans, T. Devic, J.M. Grenèche, S.
Wuttke, S. Miller, A. Lago, C. Serre, G.De Weireld, G. Maurin, A. Vimont, G. F
érey, Chem. Mater. 23 (2011) 4641-4651. (DOI: 10.1021/cm2025747)
[42].
(DOI:10.1002/anie.196901771 )
[43]. M.S. Paley, J.M. Harris, H. Looser, J.C. Baumert, G.C. Bjorklund, D. Jundt,
R.J. Twieg, J. Org. Chem. 54 (1989) 3774-3778. (DOI: 10.1021/jo00277a007)
W. Liptay, Angew. Chem. Int. Ed.
8
(1969) 177-188.
[44].
T.M. Clarke, K.C. Gordon, W.M. Kwok, D.L. Phillips, D.L. Officer, J. Phys.
Chem. A 110 (2006) 7696-7702. (DOI: 10.1021/jp0600312)
[45].
D.S. Chemla, J.E. Zyss, Nonlinear Optical Properties of Organicmolecules
and Crystals, Academic Press, New York, USA 1987.
[46].
J. Huang, N. Dong, S. Zhang, Z. Sun, W. Zhang, J. Wang, ACS Photonics 4
(2017) 3063-3070. (DOI: 10.1021/acsphotonics.7b00598)
[47].
N. Ono, S. Ito, C.H. Wu, C.H. Chen, T.C. Wen, Chem. Phys. 262 (2000)
467-473. (DOI: 10.1016/S0301-0104(00)00306-2)
[48].
P. Poornesh, P.K. Hegde, G. Umesh, M.G. Manjunatha, K.B. Manjunatha,