Second-Order nonlinear optical activity induced by ordered dipolar chromophores confined in the pores of an anionic metal-organic framework

Full text of DOI:10.1002/anie.201204160

Angewandte
Chemie
DOI: 10.1002/anie.201204160
Metal–Organic Frameworks
Second-Order Nonlinear Optical Activity Induced by Ordered Dipolar
Chromophores Confined in the Pores of an Anionic Metal–Organic
Framework**
Jiancan Yu, Yuanjing Cui,* Chuande Wu, Yu Yang, Zhiyu Wang, Michael OꢀKeeffe,
Banglin Chen,* and Guodong Qian*
Organic second-order nonlinear optical (NLO) materials
have potential applications in high-speed electro-optic mod-
ulators and all-optical data processing devices. Thus these
materials have attracted considerate attention over the past
decade.[1,2] Among the prerequisites such as large chromo-
phore hyperpolarizability (b), chromophore number density,
and efficient acentric molecular ordering, efficient ordering is
the most crucial while most challenging task for achieving
large bulk second-order NLO responses. Although a variety
of organic chromophores with high b values have been
developed for a long time, so far no powerful strategy has
been realized to induce efficient acentric molecular ordering,
and thus the use of these organic chromophores as nonlinear
optical materials is limited. The developed strategies for
inducing noncentrosymmetric arrangements of dipolar chro-
mophores which include electric-field poling and self-assem-
bly suffer from intermolecular dipole–dipole interactions
among the packed chromophores.[3–7]
also be possible to encapsulate matching ordered dipolar
chromophores in the pores of a porous MOFs; however, this
has never been realized. Herein we report the first example of
a microporous MOF that includes the ordered organic dipolar
chromophore 4-(4-(diphenylamino)styryl)-1-dodecylpyridi-
nium bromide (DPASD) and forms a highly NLO active
anionic MOF (ZJU-28ꢀDPASD; ZJU = Zhejiang Univer-
sity).
Reaction of 4,4’,4’’-benzene-1,3,5-triyl-tribenzoic acid
(H3BTB) and InCl3 in N,N-dimethylformamide/1,4-dioxane/
H2O at 1308C affords the colorless needle-like crystals of
(Me2NH2)3[In3(BTB)4]·12DMF·22H2O (ZJU-28). Com-
¯
pound ZJU-28 crystallizes in the P62c space group, which
has a symmetric element, c, and thus does not show a second-
order nonlinear optical response. In the crystal structure of
ZJU-28, the eight-coordinated indium centers act as nodes,
which are connected by two H3BTB linkers parallel to the
ab plane and another two linkers roughly perpendicular to
ab plane. Therefore, every indium center is coordinated by
four H3BTB linkers and can be seen as a four-fold connected
node, and every tritropic H3BTB linker is a three-fold
connected node (Figure 1a). The underlying net of ZJU-28
is an unusual MOF and, we believe, not described before. The
net is quite different from the default net expected for
tetrahedral and planar triangular vertices.[27] The net is
remarkably self-entangled and it has for a net composed of
low-coordinated vertices a high density. The net is made up of
three families of parallel corrugated 63 nets that are inter-
woven so that a layer of each family is catenated to all the
members of the other two families as shown in Figure 1b. Two
periodic 63 nets are joined by further links to make the whole
structure just one (3,4)-coordinated net to which the RCSR
(recticular chemistry structure resource) symbol jcy has been
assigned.[28]
To make use of the pore confinement effect of the
emerging porous metal–organic frameworks (MOFs)[8–23] for
specific inclusion of guest substrates, a few microporous
MOFs have been targeted for the efficient polymerization
and separation of xylene isomers.[24–26] In principle, it should
[*] J. C. Yu, Prof. Dr. Y. J. Cui, Dr. Y. Yang, Prof. Dr. Z. Y. Wang,
Prof. Dr. B. Chen, Prof. Dr. G. D. Qian
State Key Laboratory of Silicon Materials
Cyrus Tang Center for Sensor Materials and Applications
Department of Materials Science and Engineering
Zhejiang University, Hangzhou, 310027 (China)
E-mail: cuiyj@zju.edu.cn
gdqian@zju.edu.cn
Prof. Dr. C. D. Wu
Department of Chemistry, Zhejiang University
Hangzhou, 310027 (China)
Two types of 1D channels along a c axis of about 6.1 ꢀ 6.1
and 7.1 ꢀ 8.5 ꢁ2 exist, respectively. The channels and void
spaces were occupied by abundant highly disordered solvent
and cationic Me2NH2 molecules, which were estimated to be
64.7% of the total volume.
Encouraged by the fact that the cationic Me2NH2
molecules can be readily exchanged by metal cations such
as Cu2+, Ni2+, and Eu3+, we examined the potential of ZJU-28
to encapsulate different pyridinium hemicyanine chromo-
phores (Figure 2a) to develop nonlinear optical MOF mate-
rials. To our surprise, four different pyridinium hemicyanine
cationic chromophores with a systematically changed alkyl
chain length, 4-(4-(diphenylamino)styryl)-1-methylpyridi-
Prof. Dr. M. O’Keeffe
Department of Chemistry and Biochemistry
Arizona State University, Tempe, AZ 85287 (USA)
Prof. Dr. B. Chen
Department of Chemistry, University of Texas at San Antonio
San Antonio, TX 78249 (USA)
E-mail: banglin.chen@utsa.edu
[**] This work was supported by the National Natural Science
Foundation of China (grant numbers 50928201, 50972127, and
51010002) and the Fundamental Research Funds for the Central
Universities, and partially supported by the Welch Foundation
(grant number AX-1730, B.C.).
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201204160.
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Figure 1. a) Crystal structure of ZJU-28 viewed along the crystallo-
graphic c direction, (In, blue polyhedra; C, orange; O, red; H atoms,
Me2NH2+ ions, and solvent molecules are omitted for clarity. b) The
underlying net of ZJU-28. Three interwoven families of 63 nets, shown
in green, blue, and red, are linked by further three-coordinated vertices
(magenta) to form a continuous three-periodic jcy net.
Figure 2. a) Schematic illustration of pyridinium hemicyanine chromo-
phores incorporated into ZJU-28; b) Fluorescent microscope images of
ZJU-28 and ZJU-28ꢀDPASD illuminated with light of 365 nm UV;
c) PXRD patterns of ZJU-28 and ZJU-28ꢀDPASD.
nium (DPASM), 1-butyl-4-(4-(diphenylamino)styryl)pyridi-
nium (DPASB), 4-(4-(diphenylamino)styryl)-1-nonylpyridi-
nium (DPASN), and 4-(4-(diphenylamino)styryl)-1-dodecyl-
pyridinium (DPASD) can be easily incorporated into the
corresponding framework materials by immersing the as-
synthesized ZJU-28 in DMF, which contains different hemi-
cyanine chromophores, for eight days at 608C to give ZJU-
28ꢀDPASM, ZJU-28ꢀDPASB, ZJU-28ꢀDPASN, and ZJU-
28ꢀDPASD with a chromophore content of 27.6, 28.2, 29.8,
and 22.9 wt%, respectively. These new hemicyanine chromo-
phore-including MOF materials have been characterized by
FTIR and luminescent spectroscopies and fluorescent mi-
croscopy. Compared with the as-synthesized ZJU-28 which
displays after excitation at 365 nm an emission of blue light at
414 nm, the new MOF material ZJU-28ꢀDPASD shows a red
emission peak at 634 nm (Figure 2b and Figure S6 in the
Supporting Information). This unique feature makes it
possible to visualize the distribution of the cationic chromo-
phores simply by fluorescent microscopy.
were for several hours immersed in the DMF solution
containing the dye molecules, a bright-red emission was
observed from the end regions of the crystals. The lumines-
cent emissive regions gradually spread over the whole MOF
crystal once the immersion time has been increased to several
days. As shown in Figure S7 in the Supporting Information, all
slices of various depths show the same fluorescent image
profile and three selected regions in the crystal show the same
luminescent spectra, indicating that the hemicyanine chro-
mophore DPASD ions have been uniformly distributed
within ZJU-28ꢀDPASD. ZJU-28ꢀDPASD is a highly crys-
talline material which retains the original crystal structure of
ZJU-28, as shown by the powder X-ray diffraction (PXRD)
patterns (Figure 2c).
A laser confocal scanning microscope was used to follow
the distribution of cationic chromophores within the host
MOF materials. After the as-synthesized ZJU-28 crystals
To study nonlinear optical properties, second harmonic
generation (SHG) measurements were performed on these
hemicyanine chromophore-including ZJU-28 materials by the
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Kurtz powder technique using a Q-switched Nd:YAG pulse
laser with a 1064 nm as fundamental frequency laser.[29] The
output signals were collected by a fiber spectrometer at 520 to
560 nm, to distinguish the SHG signals from fluorescence
emission. As shown in Figure 3a,c, the inclusion of these
hemicyanine chromophores tunes the ZJU-28 MOF material
surface.[30] Studies indicated that the measured SHG intensity
of ZJU-28ꢀDPASD matches with the theoretically calculated
intensity, which indicates that the second-order nonlinear
optical effect indeed occurs in ZJU-28ꢀDPASD and is
attributed to the acentric orientation of the chromophore
DPASD ions in ZJU-28ꢀDPASD.
Using the confocal laser scanning microscope equipped
with a femtosecond laser pulsed at 1040 nm, the SHG
response of ZJU-28ꢀDPASD was imaged by collecting the
SHG signal at 520 nm (Figure 3b). The slices of the SHG
images in different depths display a uniform SHG distribution
in the single crystal, further indicating that the NLO activity
originates from the ordered chromophores in the host MOF
ZJU-28.
Exact pore/channel matching with the included hemi-
cyanine chromophores and strong interactions between the
host framework and the included hemicyanine chromophore
guest ions are important for stabilizing the highly ordered
NLO active hemicyanine chromophore guest ions to generate
nonlinear optical properties. As shown before, the SHG
intensities of the examined materials are heavily dependent
on the included hemicyanine chromophore guest ions: the
longer the terminal alkyl chain of the included hemicyanine
chromophore guest ions, the stronger the SHG intensity of the
resulting MOF material. In fact, the SHG intensity of ZJU-
28ꢀDPASD is about 73 times higher than that of ZJU-
28ꢀDPASM. It is speculated that the longer alkyl chain
minimizes the rotational freedom of the included hemi-
cyanine chromophore guest ions and enhances the interac-
tions with the host framework, leading to the most ordered
DPASD ions in the 1D channels of the ZJU-28 framework.
Given the fact that DPASD is a basically linear molecule, 1D
pore channel confinement within porous MOF materials is
necessary for the incorporation of the ordered dipolar
chromophores and generation of second-order nonlinear
optical activity. For comparison, a DPASD-including MOF
NOTT-210ꢀDPASD (NOTT-210 = In-TPTC, TPTC = ter-
phenyl-3,3’’,5,5’’-tetracarboxylic acid)[31] with 3D intersecting
pores/channels of about 6.1 ꢀ 12.0 and 6.8 ꢀ 6.8 ꢁ2 has no
detectable SHG signals. Furthermore, the MOF bio-MOF-
Figure 3. a) SHG spectra of ZJU-28ꢀDPASD. Inset: The SHG intensity
of ZJU-28ꢀDPASD as a function of the energy of the fundamental
frequency laser. b) Confocal scanning microscopic images of a triangu-
lar prism crystal of ZJU-28ꢀDPASD in a depth scanning mode imaged
using SHG signals. c) Comparison of the SHG intensities of a quartz,
ZJU-28, and the chromophore-including ZJU-28.
1ꢀDPASD
(bio-MOF-1 = Zn8(ad)4(BPDC)6O·2Me2NH2,
from NLO inactive to NLO active materials ZJU-
28ꢀDPASM, ZJU-28ꢀDPASB, ZJU-28ꢀDPASN, and ZJU-
28ꢀDPASD observed at 532 nm, with powder SHG inten-
sities of 0.25, 0.28, 3.5, and 18.3, respectively, versus a quartz.
The high SHG intensity of 18.3 in ZJU-28ꢀDPASD is
remarkable. The SHG intensity is proportional to the
square of the energy of the fundamental frequency beam. In
theory, the SHG intensity I2w from any interface of the crystals
in either reflection or transmission geometry is proportional
to the square of the NLO coefficient c(2) and to the energy of
the fundamental frequency beam Iw [Eq. (1)]:
ad = adeninate, BPDC = biphenyldicarboxylate),[32] with
larger 1D pore channels of about 5.8 ꢀ 5.8 and 8.9 ꢀ 8.9 ꢁ2
does not show any NLO properties because of the poor pore
channel confinement of bio-MOF-1 for the DPASD ions
(Figure S9–S14).
Nonlinear optical MOF materials have been exclusively
constructed from dipolar organic linkers before.[11] This
traditional strategy still suffers from unpredictabe resulting
MOF structures which do not necessarily fulfill the require-
ment of noncentrosymmetric crystal packing. As shown in our
first example of the anionic MOF ZJU-28 which was used to
align ordered pyridinium hemicyanine chromophores into the
1D channels and generate high nonlinear optical activity, we
developed an approach to construct NLO MOF materials.
This strategy will broaden research on NLO MOF materials
because any kind of organic linker can now be used. The
combination of a wide variety of dipolar organic chromo-
phores with high b values and MOF materials of diverse pore/
32p3w2s2q2w
ꢀ
ꢀ
ꢀ
ꢀ
À
Á
2
2
2
ð1Þ
I2w
¼
e2w ꢁ cð2Þe2w Iw
/
cð2Þ Iw2
c3
where q is the angle from the surface normal, at which the
SHG signal occurs, the vectors ew and e2w describe the
fundamental and the second harmonic light fields at the
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[6] J. Gao, Y. Cui, J. Yu, Z. Wang, M. Wang, J. Qiu, G. Qian,
Macromolecules 2009, 42, 2198 – 2203.
[7] W. Lin, Y. Cui, J. Gao, J. Yu, T. Liang, G. Qian, J. Mater. Chem.
2012, 22, 9202 – 9208.
channel structures and tunable pore/channel sizes will result
in highly active NLO MOF materials in the future.
[8] M. OꢂKeeffe, O. M. Yaghi, Chem. Rev. 2012, 112, 675 – 702.
[9] B. Chen, S. Xiang, G. Qian, Acc. Chem. Res. 2010, 43, 1115 –
1124.
[10] Y. Cui, Y. Yue, G. Qian, B. Chen, Chem. Rev. 2012, 112, 1126 –
1162.
[11] C. Wang, T. Zhang, W. Lin, Chem. Rev. 2012, 112, 1084 – 1104.
[12] J. P. Zhang, Y. B. Zhang, J. B. Lin, X. M. Chen, Chem. Rev. 2012,
112, 1001 – 1033.
[13] G. K. H. Shimizu, R. Vaidhyanathan, J. M. Taylor, Chem. Soc.
Rev. 2009, 38, 1430 – 1449.
[14] J. R. Li, J. Sculley, H. C. Zhou, Chem. Rev. 2012, 112, 869 – 932.
[15] H.-L. Jiang, Y. Tatsu, Z.-H. Lu, Q. Xu, J. Am. Chem. Soc. 2010,
132, 5586 – 5587.
[16] S.-T. Zheng, J. J. Bu, T. Wu, C. Chou, P. Feng, X. Bu, Angew.
Chem. 2011, 123, 9020 – 9024; Angew. Chem. Int. Ed. 2011, 50,
8858 – 8862.
[17] Y. Liu, X. Xu, F. Zheng, Y. Cui, Angew. Chem. 2008, 120, 4614 –
4617; Angew. Chem. Int. Ed. 2008, 47, 4538 – 4541.
[18] Y. Liu, G. Li, X. Li, Y. Cui, Angew. Chem. 2007, 119, 6417 – 6420;
Angew. Chem. Int. Ed. 2007, 46, 6301 – 6304.
[19] J. An, C. M. Shade, D. A. Chengelis-Czegan, S. P. Petoud, N. L.
Rosi, J. Am. Chem. Soc. 2011, 133, 1220 – 1223.
[20] C. Wang, K. E. deKrafft, W. Lin, J. Am. Chem. Soc. 2012, 134,
7211 – 7214.
[21] W. Zhou, H. Wu, T. Yildirim, J. Am. Chem. Soc. 2008, 130,
15268 – 15269.
[22] S. Yang, X. Lin, A. J. Blake, G. S. Walker, P. Hubberstey, N. R.
Champness, M. Schrçder, Nat. Chem. 2009, 1, 487 – 493.
[23] S. Yang, X. Lin, W. Lewis, M. Suyetin, E. Bichoutskaia, J. E.
Parker, C. C. Tang, D. R. Allan, P. J. Rizkallah, P. Hubberstey,
N. R. Champness, K. Mark Thomas, A. J. Blake, M. Schrçder,
Nat. Mater. 2012, DOI: 10.1038/nmat3343.
[24] T. Uemura, D. Hiramatsu, Y. Kubota, M. Takata, S. Kitagawa,
Angew. Chem. 2007, 119, 5075 – 5078; Angew. Chem. Int. Ed.
2007, 46, 4987 – 4990.
Experimental Section
Synthesis of [(CH3)2NH2]3[In3(BTB)4]·12DMF·22H2O (ZJU-28): In
a solution of DMF (36 mL), 1,4-dioxane (24 mL), water (4 mL), and
nitric acid (0.25 mL) 4,4’,4’’-benzene-1,3,5-triyl-tri-benzoic acid
(H3BTB, 532.0 mg, 1.2 mmol) and InCl3 (582.4 mg, 2.4 mmol) were
dissolved. After the resulting solution had been kept at 1308C for
24 h, it was cooled to room temperature and colorless needle-like
crystals were collected by filtration and washed with DMF (0.81 g,
58% based on H3BTB). Elemental analysis: Calcd (%) for
[(CH3)2NH2]3[In3(BTB)4]·12DMF·22H2O
(C150H212In3N15O58,
3496.12): C, 51.51; H, 6.11; N, 6.01; Found: C, 51.14; H, 5.48; N, 6.65.
Single-crystal data were collected on an Oxford Xcalibur Gemini
Ultra diffractometer with an Atlas detector. The data were collected
using graphite monochromatic Cu-Ka radiation (l = 1.54178 ꢁ) at
293 K. The data sets were corrected by empirical absorption
correction using spherical harmonics, implemented in the SCALE3
ABSPACK scaling algorithm. The structure was solved by direct
methods, and refined by full-matrix least-square methods with the
SHELX-97 program package. The hydrogen atoms were refined with
geometric constrains. The solvents in the crystal are highly disor-
dered, and the SQUEEZE subroutine of the PLATON software suit
was conducted. X-ray crystal data for ZJU-28: C108H60In3O24, Mw =
3
¯
2086.02, 0.15 ꢀ 0.23 ꢀ 0.49 mm , hexagonal, P62c a = b = 26.4797(9) ꢁ,
c = 17.4830(4) ꢁ, V= 10616.3(6) ꢁ3, Z = 2, T= 293 K, 1calcd
=
0.653 gcmꢂ3, m = 2.864 mmꢂ1, F(000) = 2094, 50712 reflections, 6565
independent reflections, Rint = 0.122, R1[I>2s(I)] = 0.0712, wR2 =
0.1782, GOF = 1.057. CCDC 884010 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.
Received: May 29, 2012
Published online: && &&, &&&&
[25] T. Uemura, N. Yanai, S. Kitagawa, Chem. Soc. Rev. 2009, 38,
1228 – 1236.
Keywords: chromophores · ion exchange ·
mesoporous materials · metal–organic frameworks ·
nonlinear optics
.
[26] L. Alaerts, C. E. A. Kirschhock, M. Maes, M. A. van der Veen,
V. Finsy, A. Depla, J. A. Martens, G. V. Baron, P. A. Jacobs,
J. E. M. Denayer, D. E. De Vos, Angew. Chem. 2007, 119, 4371 –
4375; Angew. Chem. Int. Ed. 2007, 46, 4293 – 4297.
[27] O. Delgado-Friedrichs, M. OꢂKeeffe, O. M. Yaghi, Phys. Chem.
Chem. Phys. 2007, 9, 1035 – 1043.
[1] L. R. Dalton, P. A. Sullivan, D. H. Bale, Chem. Rev. 2010, 110,
25 – 55.
[2] T. P. Radhakrishnan, Acc. Chem. Res. 2008, 41, 367 – 376.
[3] D. Frattarelli, M. Schiavo, A. Facchetti, M. A. Ratner, T. J.
Marks, J. Am. Chem. Soc. 2009, 131, 12595 – 12612.
[4] Z. Li, W. Wu, Q. Li, G. Yu, L. Xiao, Y. Liu, C. Ye, J. Qin, Z. Li,
Angew. Chem. 2010, 122, 2823 – 2827; Angew. Chem. Int. Ed.
2010, 49, 2763 – 2767.
[5] Y. Liao, S. Bhattacharjee, K. A. Firestone, B. E. Eichinger, R.
Paranji, C. A. Anderson, B. H. Robinson, P. J. Reid, L. R.
Dalton, J. Am. Chem. Soc. 2006, 128, 6847 – 6853.
[28] M. OꢂKeeffe, M. A. Peskov, S. J. Ramsden, O. M. Yaghi, Acc.
Chem. Res. 2008, 41, 1782 – 1789.
[29] S. K. Kurtz, T. T. Perry, J. Appl. Phys. 1968, 39, 3798 – 3813.
[30] R. M. Corn, D. A. Higgins, Chem. Rev. 1994, 94, 107 – 125.
[31] S. Yang, S. K. Callear, A. J. Ramirez-Cuesta, W. I. F. David, J.
Sun, A. J. Blake, N. R. Champness, M. Schrçder, Faraday
Discuss. 2011, 151, 19 – 36.
[32] J. An, N. L. Rosi, J. Am. Chem. Soc. 2010, 132, 5578 – 5579.
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Communications
Metal–Organic Frameworks
Frequency doubling: A strategy for incor-
porating dipolar organic chromophores
into the one-dimensional channels of an
anionic metal–organic framework (MOF)
has been developed to generate highly
active nonlinear optical materials (see
picture). The resulting MOF material
shows a second-harmonic generation
intensity of 18.3 versus a quartz.
J. C. Yu, Y. J. Cui,* C. D. Wu, Y. Yang,
Z. Y. Wang, M. O’Keeffe, B. Chen,*
G. D. Qian*
&&&& — &&&&
Second-Order Nonlinear Optical Activity
Induced by Ordered Dipolar
Chromophores Confined in the Pores of
an Anionic Metal–Organic Framework
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