Broadband optical limiting of a novel twisted tetrathiafulvalene incorporated donor-acceptor material and its Ormosil gel glasses

Article abstract of DOI:10.1039/c8tc02364f

To accomplish broadband optical limiting with high visible-light region (ca. 400-700 nm) transmittance, as well as to satisfy the requirement of practical applications, a novel molecule, TTF-Pt(bzimb), has been rationally designed and synthesized by connecting an excellent electron donating tetrathiafulvalene and a Pt(ii)-incorporated electron withdrawing Pt(bzimb) with a C-C triple bond. Chlorine substituted Cl-Pt(bzimb) was presented for comparison. As expected, the theoretical calculation results clearly demonstrate that TTF-Pt(bzimb) exhibits a twisted conformation with a dihedral angle of 50° at the C-C triple bond. The intramolecular charge transfer existing between the donor and the acceptor is well evidenced by a series of experimental results such as UV-vis spectra, fluorescence spectra, and CV. Benefiting from a unique conformation, TTF-Pt(bzimb) and its doped Ormosil gel glasses in a methyltriethoxysilane matrix exhibit broadband (532 and 1064 nm) optical limiting behaviour with high visible-light transmittance. Furthermore, TTF-Pt(bzimb) shows more remarkable optical limiting behaviour than the state-of-the-art optical limiting material, C₆₀, under 532 nm. Thus, our results disclose a rational molecular design strategy for the accomplishment of remarkable optical limiting. TTF-Pt(bzimb) and its gel glasses can be considered as promising candidates for the applications of optical limiting and for use in nonlinear optical devices.

Full text of DOI:10.1039/c8tc02364f

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Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
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DOI: 10.1039/C8TC02364F
Journal Name
ARTICLE
Broadband
Optical
Limiting
of
Novel
Twisted
Tetrathiafulvalene Incorporated Donor-Acceptor Material
and Their Ormosil Gel Glasses
Jibin Sun,a Biao Yuan,a Xueqing Hou,b Chaoxian Yan,b Xingming Sun,a Zheng Xie,*a
Xiangfeng Shao,*b Shuyun Zhoua
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
To accomplish broadband optical limiting with high visible-light region (ca. 400 – 700 nm) transmittance as well
as satisfy the requirement of practical application, a novel molecule TTF-Pt(bzimb) by connecting excellent
electron donating tetrathiafulvalene and Pt(II)-incorporated electron withdrawing [Pt(bzimb)] with C-C triple bond
has been rationally designed and synthesized. Chlorine substituted Cl-Pt(bzimb) is presented for comparison.
As expected, the theoretical calculation results clearly demonstrate that TTF-Pt(bzimb) exhibits a twisted
conformation with a dihedral angle of 50o along C-C triple bond, and the intramolecular charge transfer existing
between donor and acceptor is well evidenced by a series of experimental results such as UV-vis spectra,
fluorescence spectra, and CV. Benefiting from the unique conformation, TTF-Pt(bzimb) and their doped Ormosil
gel glasses in methyltriethoxysilane matrix exhibit broadband (532 and 1064 nm) optical limiting behaviour with
high visible-light transmittance. Furthermore, TTF-Pt(bzimb) shows more remarkable optical limiting behaviours
than the state-of-the-art optical limiting materials C60 under 532 nm. Thus, our results disclose one type of
rational molecular design strategy for the accomplishment of remarkable optical limiting. TTF-Pt(bzimb) and
their gel glasses would be considered as promising candidates for the application of optical limiting and nonlinear
optical devices.
to obtain higher nonlinear optical behaviours is using one- and
two-dimensional π-conjugation extension through end-capping
with electron-donating (D) and electron-withdrawing (A)
moieties to effect intramolecular charge transfer (ICT) and/or
Introduction
Organic π-electron conjugated molecules, such as fullerene
derivatives,[1-3] graphenes,[4-6] phthalocyanines,[7-10]
25, 26]
accomplish multidimensional charge transfer.[19,
Such
metalloporphyrins,[11-13] organometallic compounds,[14-19] and
so on,[20-22] have been devoted great efforts in optical limiting
(OL) for the application of laser protection materials and
devices.[23, 24] OL is a nonlinear optical process in which the
transmittance of a material decreases as the input light intensity
increases.[24] The general nonlinear optical response
mechanisms with OL behaviour are reverse saturable
absorption (RSA) at high-energy of visible-light region, and
multiphoton absorption, free charge absorption, nonlinear
refraction and scattering at the low-energy visible-light and/or
near infrared region.[23, 24] Conventionally, an efficient approach
strategies are significant to enhance OL performances.
However, there are many problems to accomplish practical
applications.[27-29] Because the expansion of π-conjugation may
(i) compress the HOMO-LUMO gap, and create one- and/or
multi-photon absorption losing at the third-order optical
susceptibility χ(3) application wavelengths; (ii) reduce the
optical transparency characteristics in visible-light regions (ca.
400 – 700 nm) due to their intense absorption band originating
from abound π-conjugated systems; and (iii) decrease the
chemical, thermal, and/or photochemical stabilities and
solubility. Marks and co-workers[30-33] discovered that a twisted
π-conjugated D-A structure can efficiently avoid these
problems induced by expanding π-system and prominently
enhance the nonlinear optical response than planar π-
conjugation systems. The twisted π-conjugated D-A molecules
a.Key Laboratory of Photochemical Conversion and Optoelectronic Materials,
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences,
Beijing 100190, P. R. China. *E-mail: zhengxie@mail.ipc.ac.cn
b.State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou
730000, P. R. China. *E-mail: shaoxf@lzu.edu.cn.
exhibit unprecedented hyperpolarizabilities on the order of 10-
33]
20 times larger than previously observed.[30,
Thus, the
† Characterization techniques, synthetic procedures, TGA, UV-vis spectra, CV,
theoretical calculations, Z-scan technology, 1H and 13C NMR spectra and FTIR. For
rational design and synthesis of twisted π-conjugated D-A
structure are efficient approaches both for solving these
Electronic
Supplementary
Information
(ESI)
available
see
DOI: 10.1039/x0xx00000x
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under 532 nm. For the convenience of practical application, the
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organically modified silicate (Ormosil) gel glasses
DOI: 10.1039/C8TC0236o4Ff
methyltriethoxysilane (MTES) matrix are employed as host
materials because of their mechanical stability, facile
preparation technique, and molecular level homogeneity of
dopants,[52, 53] and the highly homogeneous Ormosil gel glasses
of TTF-Pt(bzimb) are successfully prepared. The gel glasses
exhibit more outstanding OL abilities than their solutions. To
our best knowledge that this is the first example of TTF-
incorporated materials to accomplish broadband optical limiting
both in solution and gel glasses with high visible-light
transmittance.
Scheme 1
Chemical structures of TTF-Pt(bzimb) and model
compound Cl-Pt(bzimb)
Results and Discussion
difficulties caused by π-conjugation extension and
accomplishing high OL abilities. Unfortunately, the materials
based on such strategies are not applied specifically as OL
materials up to now.
Synthesis and Characterization
TTF-Pt(bzimb) was synthesized through cross-coupling reaction
Tetrathiafulvalene (TTF) and its derivatives,[34-40] because of between mono-ethynyl substituted TTF derivative TTF-1 and Cl-
their remarkable electron donating characters, have been widely Pt(bzimb). TTF-1 and Cl-Pt(bzimb) were synthesized according to
54]
used as an efficient electron-donor unit in D-A structures with the modified procedures of previous reports[53,
and the detail
appealing nonlinear optical properties.[41-47] Most reports of synthetic procedures were showed in Supporting Information (SI,
TTF-based D-A conjugated molecules focus on the second- ESI†). The chemical structural characterizations of TTF-Pt(bzimb)
order nonlinear optical properties, whereas the OL behaviours were processed by using 1H NMR, 13C NMR, element analysis (EA),
are either investigated through the prediction of theoretical and FTIR (see Experimental Section and SI). Thermogravimetric
44]
calculation,[43,
or experimental measurement with weak analysis (TGA) was used to characterize their thermal stability of
performance[41, 44-46, 48] such as single response wavelength (532 TTF-Pt(bzimb) and model compound Cl-Pt(bzimb) (Fig. S1, ESI†).
nm) and low nonlinear extinction coefficients (βeff = 1.19 cm The results demonstrated that model compound Cl-Pt(bzimb)
GW-1). Obviously, TTF-based D-A conjugated materials still exhibits the first mass loss (ca. 4.3%) at 112 oC which belong to the
can’t meet the requirement of practical application in OL loss of Cl atom (5.4%), and the greater mass loss appeared when the
device. Herein, a novel TTF-based D-A type conjugated TTF-
Pt(bzimb) (Scheme 1) has been rationally designed and
synthesized. In order to possess twisted and π-conjugated
conformation simultaneously, the C-C triple bond is employed
in TTF-Pt(bzimb) as D-A bridge to introduce the structural
features of rotational freedom and π-electron conjugation.
Furthermore, according to the RSA mechanism of OL
behaviours, the enhancement of intersystem crossing (ISC)
from the first singlet state (S1) to the first triplet state (T1) under
heavy-metal effect can significantly improve the OL
abilities.[49-51]
Thus,
platinum-contained
1,3-bis(N-
alkylbenzimidazol-2’-yl)benzene (Pt(bzimb)) is used as
electron acceptor. Meanwhile, the chlorine substituted Cl-
Pt(bzimb) is presented as a model compound. The chemical
conformations and frontier molecular orbits are predicted
through theoretical calculation. As expected, the results
obviously demonstrate that TTF-Pt(bzimb) exhibits twisted π-
conjugated conformation with a dihedral angle of 50o between
TTF core and Pt(bzimb) plane. The photo-induced
intramolecular charge transfer (ICT) exists between donor and
acceptor, which is well consistent with the experimental results
of optical spectra and CV. The OL abilities are studied through
Z-scan measurements. In comparison with Cl-Pt(bzimb), the
solution of TTF-Pt(bzimb) exhibits broadband (532 and 1064
nm) optical limiting properties with high visible-light
transmittance. Remarkably, the OL behaviours of TTF-
Pt(bzimb) are higher than the state-of-the-art OL materials C60
Fig. 1 (a) The TD-DFT calculated chemical structures (top and side
view along bzimb ligand plane) and (b) the frontier molecular orbital
distributions of TTF-Pt(bzimb).
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temperature reaches up to 384 oC. In comparison with Cl-Pt(bzimb), transition of independently localized π-conjugation electrons of TTF
View Article Online
DOI: 10.1039/C8TC02364F
compound TTF-Pt(bzimb) showed excellent thermal stability and and Pt(bzimb). In comparison with Cl-Pt(bzimb), the slight blue-
didn’t appear mass loss before the decomposed temperature (ca. 335 shift (4 nm) of highest absorption wavelength and more broaden
oC).
absorption band (ca. 15 nm) of TTF-Pt(bzimb) at ca. 270-340 nm
might attribute to the transition of π-electrons from bzimb ligand to
TTF core. The low energy absorption maximum at 387 and 402 nm
Theoretical calculations
To predict the relationships between the chemical for TTF-Pt(bzimb) and Cl-Pt(bzimb), respectively, could be
conformations and photo-electronic behaviours of TTF- attributed to the intra-ligand (IL) π-π* transition of bzimb ligand,
Pt(bzimb), time-dependent density functional theory (TD-DFT) probably with some mixing of metal-to-ligand charge (MLCT)
and dependent density functional theory (DFT) calculations [dπ(Pt)→π*(N^C^N)] transition.[56, 57] However, it is interest that the
were performed by using the Gaussian 09 program package at absorption maximum of TTF-Pt(bzimb) blue-shifts about 15 nm
the B3LYP/6-31G(d,p) level. The calculated molecular and the relative intensity decreases compared to Cl-Pt(bzimb). This
conformations and the frontier molecular orbital distributions of phenomenon is beneficial to OL materials for the demand of high
TTF-Pt(bzimb) and Cl-Pt(bzimb) were displayed in Fig. 1, transmittance in visible-light regions (400 – 700 nm). Furthermore,
Fig. S2, S3 and Table S1-S4 (ESI†). The TD-DFT calculation as shown in Fig. S5 (ESI†), TTF-Pt(bzimb) appears a slight
results demonstrate that compound Cl-Pt(bzimb) is structural intensity broad absorption band (ca. 430-460 nm), which mainly
coplanarity (Fig. S2, ESI†), the HOMO/HOMO-1 orbits originates from the photo-induced ICT from electron donating TTF
delocalize on the entire molecular framework, but the to electron withdrawing Pt(bzimb). These results agree well with the
LUMO+1/LUMO localized on bzimb ligand plane. Different TD-DFT calculations. Additionally, the fluorescence spectra of
from compound Cl-Pt(bzimb), the chemical structure of TTF- TTF-Pt(bzimb) and model compound Cl-Pt(bzimb) have also been
Pt(bzimb) is not coplanar as the TTF core form dihedral angles collected and demonstrated in Fig. 2b. Compound Cl-Pt(bzimb)
of ca. 50o with Pt(bzimb) plane (Fig. 1a). The HOMO and shows a strong fluorescence signal upon the excitation at 400 nm,
LUMO orbits completely localize on TTF core and Pt(bzimb) which arises from the π-π stacking of Pt(bzimb).[56] While the
ligand, respectively. However, the HOMO-1/LUMO+1 orbits fluorescence signal of TTF-Pt(bzimb) is almost quenched because
partially delocalize on TTF core and Pt(bzimb) section. of the photo-induced ICT from TTF core to Pt(bzimb).
Furthermore, TTF-Pt(bzimb) exhibits more smaller band gap
Electrochemical properties
of 2.19 eV than Cl-Pt(bzimb) of 3.80 eV. These results
obviously demonstrate that the twisted molecule TTF- The electrochemical behaviours of TTF-Pt(bzimb) and model
Pt(bzimb) exists photo-induced ICT from TTF core to compound Cl-Pt(bzimb) were investigated by cyclic
Pt(bzimb) section. Considering the global hybrid functional voltammetry (CV) vs Fc/Fc+. As shown in Fig. S6 (ESI†), TTF-
B3LYP may lead to the wrong structure due to the long-range Pt(bzimb) exhibited three reversible redox potentials, therein,
1
2
charge transfer of TTF-Pt(bzimb), the range-separated hybrid the redox potentials (E1/2 = 0.36 V and E1/2 = 0.59 V)
functional CAM-B3LYP is used to perform the calculation correspond to the typical reversible redox behaviours of
again with SDD basis set for Pt atom and 6-31+G(d,p) basis set intrinsic TTF framework. Moreover, a new reversible redox
3
for other atoms.[55] As shown in Fig. S4 (ESI†), the similar potential (E1/2 = 0.94 V) could be attributed to Pt(bzimb), and
twisted structure is obtained with larger dihedral angles (ca. 67o)
than previous calculation between TTF core and Pt(bzimb)
plane.
Photo-physical properties
The UV-vis absorption spectra of TTF-Pt(bzimb) and Cl-Pt(bzimb)
were measured in dichloromethane (CH2Cl2) solution at room
temperature. As depicted in Fig. 2a, both TTF-Pt(bzimb) and Cl-
Pt(bzimb) exhibited double absorption bands. Wherein, the high
energy absorption maximum at 302 and 306 nm for TTF-Pt(bzimb)
and Cl-Pt(bzimb), respectively, are assigned as n-π* and π-π*
Fig. 3 (a, c) Open aperture Z-scan data and theoretically fitted curves
(solid curves) and (b, d) corresponding plots of normalized
transmittance vs incident intensity of TTF-Pt(bzimb) under (a, b) 532
nm with different energies of 6 μJ, 10 μJ, and 17 μJ, and (c, d) 1064
nm with different energies of 20 μJ, 48 μJ, and 70 μJ. The open
symbols and solid lines represent the experiment results and
theoretical fits, respectively.
Fig. 2 (a) Normalized UV-vis and (b) Fluorescence spectra of TTF-
Pt(bzimb) and Cl-Pt(bzimb) in CH2Cl2 solution (c = 2.0 × 10-5 M, RT).
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Table 1 NLO coefficients of TTF-Pt(bzimb), model compound Cl-
Pt(bzimb) and C60 in 1,1,2,2-tetrachloroethane solution with identical
linear transmittance of 85% at 532 nm.
a
b
c
d
λ
I0
Tmin
Fon
βeff
Samples
[nm]
[μJ]
[%]
[J cm-2]
[cm GW-1]
6
68
57
49
89
83
73
65
60
84
69
59
0.11
0.11
0.13
0.32
0.33
0.07
0.10
0.11
0.26
0.19
0.19
156
136
138
32
TTF-Pt(bzimb)
Cl-Pt(bzimb)
C60
10
17
10
17
6
532
48
153
127
109
60
10
17
20
48
70
TTF-Pt(bzimb)
1064
80
95
Fig. 4 The comparison of OL properties of TTF-Pt(bzimb) and Cl-
Pt(bzimb) at 532 nm with different energies of 10 μJ and 17 μJ; (a)
Open-aperture Z-scan curves with normalized transmittance, (b)
corresponding plots of normalized transmittance vs incident intensity.
a
b
c
incident intensity; the minimum transmittance at the position Z = 0;
d
optical energy-limiting onset fluence (Fon) at normalized T = 95%;
nonlinear extinction coefficient.
with different molar ratios between TTF-Pt(bzimb) and MTES
were applied. The measurement setups and detail experimental
procedures are depicted in Supporting Information, and all data
are collected in Table 1 and 2. The optical nonlinearities of
samples through detecting the transmittance of a Gaussian
beam as a function of the test sample’s position (Z) relative to
laser focus (Fig. S7, ESI†). As depicted in Fig. 3a and 3c, the Z-
scan curves of TTF-Pt(bzimb) at different intensities under
wavelengths 532 and 1064 nm exhibit nonlinear optical
responses. Thus, TTF-Pt(bzimb) is a typical OL material. The
OL abilities increase along with the enhancement of laser
the oxidation potential (0.98 V) slightly decreases ca. 20 mV
compared to the irreversible redox potential of Cl-Pt(bzimb)
(1.00 V). These results disclose that the electrons independently
localize on TTF Framework and Pt(bzimb) at ground state is
beneficial to the production of photo-induced ICT.
Open aperture Z-scan
In order to investigate the OL abilities of this novel twisted π-
electron D-A molecule, the open-aperture Z-scan measurements
were carried out both in solution and gel glasses by Nd: YAG
laser (532 and 1064 nm, 8 ns, 10 Hz) with different levels of
laser intensities (I). The 1,1,2,2-tetrachloroethane solutions with
the identical linear transmittance (T0) of 85% and gel glasses
intensities,
the
corresponding
minimum
normalized
transmittances (Tmin) at the position of Z = 0 are 68% (6 μJ),
57% (10 μJ), and 49% (17 μJ) under 532 nm, and 84% (20 μJ),
Fig. 5 (a) Open aperture Z-scan data and theoretically fitted curves (solid curves) and (b) corresponding plots of normalized transmittance vs
incident intensity of TTF-Pt(bzimb) and C60 at different energies under 532 nm.
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DOI: 10.1039/C8TC02364F
Table 2 NLO coefficients of TTF-Pt(bzimb) in MTES gel glasses
(G1, G2, and G3) with different concentration under the wavelengths
of 532 and 1064 nm.
a
b
c
d
e
T0
λ
I0
[μJ]
Tmin
Fon
βeff
Samples
[%]
86
[nm]
[%]
[J cm-2]
[cm GW-1]
532
1064
532
10
18
29
20
23
14
12
0.05
0.25
0.04
0.21
0.03
0.10
227
45
G1
G2
G3
110
10
279
52
77
41
1064
532
110
10
393
112
1064
110
a
c
the linear transmittance at 532 nm; b incident intensity; the minimum
d
Fig. 7 (a, c) Open aperture Z-scan data and theoretically fitted curves
(solid curves) and (b, d) corresponding plots of normalized
transmittance vs incident intensity of TTF-Pt(bzimb) in gel glasses
with different concentrations at (a, b) 532 nm, 10 μJ (c, d) 1064 nm,
110 μJ. The open symbols and solid lines represent the experiment
results and theoretical fits, respectively.
transmittance at the position Z = 0; optical energy-limiting onset fluence
(Fon) at normalized T = 95%; nonlinear extinction coefficient. The
e
thickness of all glasses is 1 mm.
69% (48 μJ), and 59% (59 μJ) under 1064 nm, respectively.
The OL plots of normalized transmittance vs incident intensity are
extracted by theoretically fitting from Z-scan data. As depicted in
Fig. 3b and Fig. 3d, the transmittance shows no appreciable decrease
before the optical energy-limiting onset fluence (Fon, which defined
as the fluence where transmittance starts to fall to 95% of its original
value[58]) of ca. 0.11 J cm-2 under 532 nm, which obeys the Beer’s
Law. However, when the intensities increase as the sample moves
toward the laser focus, the normalized transmittance decreases and
optical responses.[19, 59-61] These results show that the novel TTF-
Pt(bzimb) is an excellent OL material exhibiting broadband spectra
OL ability and low Fon. In contrast, Cl-Pt(bzimb) only exhibits
weaker OL behaviours under 532 nm (Fig. 4), higher Fon of ca. 0.33
J cm-2, and lower nonlinear coefficient βeff of 32 – 48 cm GW-1 at
laser intensity above 6 μJ.
For evaluating the advantages of TTF-Pt(bzimb) as OL
deviates from linearity, suggesting
a typical OL behaviour.
[24]
materials, the state-of-the-art OL materials C60
is used for
Furthermore, TTF-Pt(bzimb) exhibits OL properties when the Fon
reach up to ca. 0.21 J cm-2 under 1064 nm. The nonlinear extinction
coefficients (βeff) are high up to 136 - 156 cm GW-1 and 60 - 95 cm
GW-1 corresponding to 532 and 1064 nm wavelengths, respectively.
The increase of βeff at 1064 nm implies that the observed OL
behaviour of TTF-Pt(bzimb) is influenced by multiple nonlinear
comparison. Unlike TTF-Pt(bzimb), C60 only shows OL
properties under 532 nm at the same T0 of ca. 85% in CH2Cl2
solution, and TTF-Pt(bzimb) exhibits more outstanding OL
properties at the different energies under 532 nm. As shown in
Table 1 and Fig. 5, the Tmin of C60 are 73%, 65%, and 60% at
energies of 6 μJ, 10 μJ, and 17 μJ, respectively, which are
higher than corresponding TTF-Pt(bzimb). Furthermore, the
βeff of C60 109 – 153 cm GW-1 are lower than corresponding TTF-
Pt(bzimb) solution.
Based on the excellent OL properties of TTF-Pt(bzimb)
,
their highly homogenous gel glasses doped in MTES with
different concentrations were prepared successfully for the
convenient application of optical limiting (Fig. 6). The molar
ratios of TTF-Pt(bzimb) and MTES in glasses G1, G2, and G3
were 1 : 300, 1 : 100, and 1 : 30, respectively. The blank glass
was used for comparison. The linear transmittances (532 nm) of
blank glass, G1, G2, and G3 are of 88%, 86%, 77%, and 41%,
respectively. As demonstrated in Fig. 7 and Table 2, the gel
glasses of TTF-Pt(bzimb) exhibit more outstanding OL
properties than their solution under broadband wavelengths
(532 and 1064 nm), which would be attributed to the molecular
aggregation of TTF-Pt(bzimb) in MTES matrix. The nonlinear
transmittance Tmin of glass G1 can reduce to 18% at input
intensity 10 μJ under 532 nm. Compared with G1, the Tmin of
G2 and G3 does not show more significant decline along with
the increase of TTF-Pt(bzimb) concentration, the Tmin of G2
and G3 is of 20% and 14%, respectively. The corresponding βeff
Fig. 6 (a) The gel glasses photos of TTF-Pt(bzimb) with different
concentrations; (b) transmittance spectra of gel glasses.
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of G1 G2, and G3 increased along with the concentration of
TTF-Pt(bzimb) is high up to 227, 279 and 393 cm GW-1,
respectively. Likewise, these gel glasses exhibit excellent OL
abilities under 1064 nm at 110 μJ intensity. The corresponding
Journal Name
,
Conclusion
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DOI: 10.1039/C8TC02364F
In summary, we rationally design and synthesis a novel twisted
π-conjugated D-A type molecule TTF-Pt(bzimb), based on the
electron donating TTF moiety and electron withdrawing
Pt(bzimb), and C-C triple bond is used for D-A bridge. The
chemical conformation and frontier molecular orbits are
predicted firstly by using theoretical calculations. The results
clearly demonstrate that TTF-Pt(bzimb) exists dihedral angle
of ca. 50o between TTF core and Pt(bzimb) along with C-C
triple bond, but there is no significant influence on conjugated
properties, and photo-induced ICT is existing between donor
and acceptor. Furthermore, these results are well verified by
photo/electronic measurements. The experimental results
disclose that the twisted D-A type TTF-Pt(bzimb) exhibits
high visible-light transmittance and displays broader photo-
induced ICT absorption band at 430 – 500 nm than model
compound Cl-Pt(bzimb). The CV results demonstrate that
TTF-Pt(bzimb) owns three reversible redox potentials
indicating the independent localization of electrons on donor
TTF core and acceptor Pt(bzimb). The highly homogenous
Ormosil gel glasses of MTES matrix doped with TTF-
Pt(bzimb) are prepared to satisfy the practical application in
OL. Open aperture Z-scan obviously discloses that the solutions
and gel glasses of TTF-Pt(bzimb) exhibit excellent OL
properties with high visible-light transmittance under
broadband limiting wavelength (532 nm and 1064 nm). TTF-
Pt(bzimb) shows better OL properties than the state-of-the-art
OL materials C60. In brief, the concerned results should
represent a rational molecular design strategy and a valuable
candidate material for accomplishing broadband OL as well as
constructing nonlinear optical devices.
Tmin of G1
The βeff of G1
,
G2, and G3 is of 29%, 23%, and 12%, respectively.
G2 and G3 is of 45, 52, and 112 cm GW-1,
,
respectively. These results disclose that TTF-Pt(bzimb) and
their gel glasses exhibit broadband OL properties with high
visible-light transmittance and would be considered as
remarkable candidates in the application of OL and nonlinear
optical devices.
Experimental sections
Unless otherwise indicated, all materials and reagents were
commercially available and used without further purification.
Compounds TTF-1 and Cl-Pt(bzimb) were synthesized
according to previous reports.[54, 56, 57] Because of the unstable
properties of compound TTF-1 and its precursor compounds to
an acidic condition, the synthesis and characterization
procedures should proceed under neutral or alkaline conditions.
Synthesis of TTF-Pt(bzimb)
A mixtures of TTF-1 (27 mg, 0.12 mmol) in 15 mL degassed
CH2Cl2 and NaOH (12 mg, 0.30 mmol) in 5 mL degassed
CH3OH were stirred at room temperature for 0.5 h under N2
protection. Then a solution of Cl-Pt(bzimb) (66 mg, 0.10
mmol) in 10 mL degassed CH2Cl2 was added, and the mixture
refluxed overnight under N2 protection. Cooled down to RT and
filtered, the precipitate was washed successively with water,
methanol and diethyl ether. Subsequent recrystallization
through diffusing diethyl ether into a concentrated CH2Cl2
solution, and a yellow powder was obtained (53 mg, yield:
1
63%). H NMR (400 MHz, dichloromethane-d2, 298 K): δ 8.59
Acknowledgements
(d, J = 8.1 Hz, 2H), 7.52 (d, J = 7.8 Hz, 2H), 7.39 (t, J = 7.6 Hz,
2H), 7.27 (m, 5H), 6.40 (s, 2H), 6.28 (s, 1H), 4.83 (t, J = 7.5
Hz, 4H), 1.91 (m, 4H), 1.48 (m, 4H), 0.97 (t, J = 7.4 Hz, 6H).
13C NMR (100 MHz, dichloromethane-d2, 298 K): δ 164.19,
141.77, 135.51, 134.45, 133.86, 124.40, 124.13, 123.95,
123.58, 119.60, 119.36, 119.28, 115.72, 109.90, 45.19, 32.38,
20.64, 13.92. Anal. calcd for C36H32N4PtS4: C, 51.23; H, 3.82;
N, 6.64; S, 15.12. Found: C, 50.93; H, 3.91; N, 6.36; S, 15.03.
IR spectrum (KBr, cm-1): 3064, 2955, 2927, 2868, 2362, 2341,
2063, 1515, 1501, 1482, 1443, 1358, 1311, 1294, 1175, 1101,
1010, 795, 777, 742, 651.
This work was supported by National Natural Science
Foundation of China (NSFC, Grant No. 21702214, 21522203)
and Director Foundation of Technical Institute of Physics and
Chemistry, Chinese Academy of Sciences (Grant No. 2017-
SJB).
Notes and references
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Journal of Materials Chemistry C
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View Article Online
DOI: 10.1039/C8TC02364F
Table of Contents use only
Title: Broadband Optical Limiting of Novel Twisted Tetrathiafulvalene Incorporated
Donor-Acceptor Material and Their Ormosil Gel Glasses
Authors: Jibin Sun, Biao Yuan, Xueqing Hou, Chaoxian Yan, Xingming Sun, Zheng
Xie,* Xiangfeng Shao,* Shuyun Zhou
A novel tetrathiafulvalene incorporated D-A molecule TTF-Pt(bzimb) is rationally
designed and synthesized for broadband optical limiting.