Multi-Photon Absorption in Metal–Organic Frameworks

Article abstract of DOI:10.1002/anie.201706492

Multi-photon absorption (MPA) is among the most prominent nonlinear optical (NLO) effects and has applications, for example in telecommunications, defense, photonics, and bio-medicines. Established MPA materials include dyes, quantum dots, organometallics

Full text of DOI:10.1002/anie.201706492

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Accepted Article
Title: Multi-Photon Absorption in Metal-Organic Frameworks
Authors: Raghavender Medishetty, Lydia Nemec, Venkatram Nalla,
Sebastian Henke, Marek Samoc, Karsten Reuter, and Roland
A. Fischer
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Multi-Photon Absorption in Metal-Organic Frameworks
Raghavender Medishetty,†[a] Lydia Nemec,†[b] Venkatram Nalla,* Sebastian Henke, Marek Samoć,
[c]
[d]
[e]
[b]
[a]
Karsten Reuter,* Roland A. Fischer*
Abstract: Multi-photon absorption (MPA) is among the most
prominent nonlinear optical (NLO) effects and has applications, for
example in telecommunications, defense, photonics and bio-
medicines. Established MPA materials include dyes, quantum dots,
organometallics and conjugated polymers, most often dispersed in
solution. We demonstrate how metal-organic frameworks (MOFs), a
novel NLO solid-state materials class, can be designed for
exceptionally strong MPA behavior. MOFs consisting of zirconium-
and hafnium-oxo-clusters and featuring a chromophore linker based
on the tetraphenylethene (TPE) molecule exhibit record high two-
photon absorption (2PA) cross section values, up to 3600 GM. The
unique modular building-block principle of MOFs allows enhancing
and optimizing their MPA properties in a theory guided approach by
combining tailored charge polarization, conformational strain, three-
dimensional arrangement and alignment of the chromophore linkers
in the crystal.
A new material class, metal-organic frameworks (MOFs),
offers an elegant way to overcome these challenges. MOFs
consist of metal ion/cluster nodes bound to organic molecules
called linkers and self-assembled into crystalline structures[ with
unique packing of the linkers (Figure 2). MOFs have mainly been
investigated in the context of gas storage, gas separation and
catalysis.[8] Intrinsic nonlinear optical (NLO) properties can be
tuned in MOFs by choosing chromophores as linkers.[
Alternatively, MOFs can be loaded (by impregnation) with dyes to
achieve NLO (extrinsic) properties and multi-photon pumped
lasing.[10] Particularly, the spatial arrangement, rigidification and a
specific conformation of the linker, caused by the pinning of the
linker between the metal nodes leads to materials which
outperform any solid-state MPA material known so far. We
identified five important design criteria to obtain MOFs with record
high MPA cross section values.
7]
9]
Multi-photon absorption (MPA) is a process in which two or more
photons are simultaneously absorbed by a material (Figure 1).
MPA facilitates important applications, such as two-photon
[
1]
fluorescence microscopy , three-dimensional (3D) optical data
[
2]
[3]
[4]
storage , optical limiting , and 3D microfabrication , to name a
few. So far, the search for materials with high MPA cross section
values has focused on organic dye molecules, polymers,
organometallic compounds and nanoparticles.[5] However,
commonly used MPA materials are mainly usable only as low
concentrated solutions (~10-2 mol/dm3)[5a] to avoid unwanted
aggregation and concentration quenching of the MPA excited
emission, along with low optical stability.[6]
Figure 1. A scheme depicting the excitation of a metal-organic framework
(MOF) crystal and the observation of multi-photon excited fluorescence.
Middle: Emission of green fluorescence upon excitation of a yellow MOF crystal
by a focused beam of a femtosecond laser. Left: Energy level diagram showing
the simultaneous absorption of one to multiple photons and the green
fluorescence emission from the excited state. Right: Schematic view of the MOF,
with the metal-nodes (red spheres) interlinked by the chromophore linker (blue/
grey structures). Note, the conformation of the biphenyl units of the linker is
simplified for clarity (see Supporting Information).
[
a]
Dr. Raghavender Medishetty, Prof. Dr. Roland A. Fischer
Chair of Inorganic and Metal-Organic Chemistry, Technische
Universität München, Lichtenbergstraße 4, 85747 Garching,
Germany.
E-mail: roland.fischer@tum.de
Our design concept for a perfect MOF for superior MPA
applications follows several criteria that are similar to those
employed for organic or organometallic NLO chromophore
molecules:[5b, 11] a) molecular dipole or multipolar structural units
[
b]
c]
Dr. Lydia Nemec, Prof. Dr. Karsten Reuter
Chair of Theoretical Chemistry, Technische Universität München,
Lichtenbergstraße 4, 85747 Garching, Germany.
E-mail: karsten.reuter@ch.tum.de
[
Dr. Venkatram Nalla
for an enhanced polarization of the charge distribution, b)
presence of planar structural motifs with long π-conjugation, c)
high fluorescence quantum yield, d) narrow one-photon
absorption (1PA) and two-photon (2PA) absorption bands, as well
as significant wavelength differences between them, and e)
Centre for Disruptive Photonic Technologies, School of Physical and
Mathematical Sciences, Nanyang Technological University,
Singapore 637371, Singapore.
E-mail: VNalla@ntu.edu.sg
Dr. Sebastian Henke
Department of Chemistry and Chemical Biology, Technische
Universität Dortmund, Otto-Hahn-Straße 6, 44227 Dortmund,
Germany.
Prof. Dr. Marek Samoć
Advanced Materials Engineering and Modelling Group, Wroclaw
University of Science and Technology, Wyb. Wyspiańskiego 27, PL-
[
d]
e]
3
alignment and high packing density (concentration mol/dm ) of
the NLO chromophore. A very desirable aspect and so far
unresolved challenge to match the last criterion is the rational
control of organization and arrangement of the chromophores, i.e.
donor and acceptor units in 3D space.[ MOFs offer a unique
access to a “targeted design” of this property.
[
12]
50370, Wrocław, Poland.
†
These authors contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
In this work, we demonstrate how the 2PA cross section
values of the parent tetrakis[4-(4-carboxyphenyl)phenyl]ethylene
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COMMUNICATION
analogues (Figure 2; MOFs 2, 5,
6). In addition, we obtain
electron-withdrawing TFA-
bonded structures (3, 5) and
TFA-hydrolyzed structures (4, 6)
to demonstrate the modulation of
charge transfer. The hydrolyzed
structures feature OH and H
co-ligands instead of TFA.
2
O
There are various methods to
investigate
properties.[
MPA
optical
5a, 11, 14]
We use multi-
photon excited fluorescence
MPEF) measurements with an
(
internal reference, in order to
minimize the uncertainties due to
scattering effects (the MOFs are
suspended
solutions;
Information, Section 2).
in
see
rhodamine-B
Supporting
[9a]
We
start our investigations of MPA
optical properties with the cubic
structures 1 and 2, which are
found to show 2PA action cross
section values of 1035 GM and
Figure 2. Basic building blocks and structures of the investigated MOFs (compound 1-6). Top left: The basic
building blocks are zirconium- and hafnium-oxo cluster nodes {M
co-ligands (trifluoroacetate or hydroxide). Bottom left: a schematic view of the cubic MOFs 1, Zr/TCPEcubic
Zr (OH) (TCPE) ] and 2, Hf/TCPEcubic, [Hf (OH) (TCPE) ], where the nodes are coordinated by 12 carboxylate
groups of the TCPE linkers (12-connected node). Right: hexagonal kagome-type lattice MOFs 3-6 (M/X/TCPEkagome
(OH) (H O) (X) (TCPE) ], M = Zr or Hf, X = OH or CO CF ), where the nodes are coordinated by 8 carboxylate
groups (8-connected node) resulting in the formation of a mesoporous structure with 1D channels along the z-axis.
In the case of 3, Zr/CO CF /TCPEkagome and 5, Hf/CO CF /TCPEkagome the nodes are also coordinated by
trifluoroacetate co-ligands (top right), whereas in 4, Zr/OH/TCPEkagome and 6, Hf/OH/TCPEkagome the nodes are
coordinated by additional OH and H O (bottom right).
6 4 4
O (OH) }, a flexible TCPE linker and two different
,
[
6
O
4
4
3
O
6 4
4
3
292 GM, respectively. The action
,
cross section is a product of the
absorption cross section (σ) and
the luminescence quantum yield
[
M
6
O
4
6
2
4
2
2
2
3
2
3
2
3
2
(η). Figure
3
shows the
measured 2PA (a), 3PA and 4PA
b) action cross section values of 1-6. For comparison, a sample
4
(H TCPE) NLO chromophore can be increased by two orders of
(
magnitude by integrating them as TCPE linkers into a rigid MOF
structure. Optimizing TCPE-based MOFs by synthesis to fulfill the
above mentioned design criteria, we achieve record high 2PA
action cross section values of 3582 GM (GM abbreviates the unit
4
of the parent chromophore H TCPE exhibits a weak 2PA action
cross section of 55 GM, while its 3PA is already too weak to be
measured (Supporting Information, Table S5). The two MOFs 3
2
and 4 give the strongest action cross section values (ησ = 3582
GM and 2590 GM, respectively) ever found for any solid MPA
material in the literature.[15] The Zr-based materials 1, 3 and 4
show higher 2PA, 3PA and 4PA action cross section values than
their respective Hf analogues. Although the cubic MOFs 1 and 2
have a higher TCPE concentration, they show reduced, however,
still very high 2PA action cross section values compared to dyes,
quantum dots, porphyrins and other MOFs (see Supporting
Information, Section 3); the same trend holds for the 3PA and 4PA
Göppert-Mayer, 1GM = 10-50 cm s photon ).
4
-1
To demonstrate the effect of the nature of the building blocks
on the MPA efficiency, we choose zirconium- and hafnium-oxo
clusters as inorganic nodes and trifluoroacetate (TFA) or
hydroxide (OH) as additional co-ligands (Figure 2). Employing
these building blocks, we synthesize a series of chemically robust
MOFs (1-6 in Figure 2) (see Supporting Information, Section 1).
All six compounds feature nodes with an octahedral core unit
(
Figure 3b).
{
6 4 4
M O (OH) }, where M stands for the respective metal ion. The
MOFs 1 and 2 crystallize in the cubic space group Pm-3m, where
the 12-connected metal ion nodes are located at the cube corners
and TCPE linkers cover the cubes faces.[9b] MOF 3-6 crystallize
in the hexagonal space group P6/mmm and contain three 8-
connected nodes and six highly strained TCPE linkers per unit cell
forming a 3D-kagome lattice. This structural arrangement leads to
one of the largest known 1D open channels among MOFs.[13]
Nevertheless, a comparably dense packing of the TCPE can still
be achieved,[ leading to chromophore linker concentrations of
For a better understanding of this discovery, we perform
electronic structure calculations on the level of time-dependent
density functional theory (TDDFT)[16] (see Supporting Information,
Section 4) using the long-range corrected hybrid functional cam-
B3LYP.[17] We systematically investigate the origin of the
massively increased 2PA cross section by exploring the influence
of charge transfer, polarization and structural arrangement on the
non-linear optical properties.
9c]
3
3
First, we study the effect of the metal-oxo cluster node and
co-ligands on the charge transfer between the TCPE linker and
the node by calculating Hirshfeld charges.[18] For the two cubic
0.52 mol/dm (1, 2) and 0.28 mol/dm (3-6). The electrophilic
charge polarization influence of the node on the chromophore
linker is explored by including two series of MOFs, Zr-based
nodes (Figure 2; MOFs 1, 3, 4) and their isostructural Hf-
-
MOFs 1 and 2, we obtain a charge transfer of 1e per linker,
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Figure 3. MPA action cross section values of MOFs 1-6 and H
4
TCPE (L). (a) Comparison of 2PA cross section values ησ
2
(dark blue) of MOFs 1-6 (Figure 2)
-
50
4
-1
with H
4
TCPE (1GM = 10 cm s photon ), (b) 3PA (ησ
3
, deep blue) and 4PA (ησ
4
, light blue) action cross section values of MOFs 1-6. The gray bars indicate the
experimental error.
leading to a positively charged TCPE. Here, the choice of Zr
versus Hf shows no effect on the charge transfer. For the kagome
lattice Zr-MOF 4 with hydroxide co-ligands, the charge transfer is
equal to 1 and 2 (1e- per TCPE). However, if an electron-
charge case, it exhibits a clear maximum for a C-C distance of
16 Å. The absolute value is furthermore a factor of three larger for
the charged molecule, which we expect to better represent the
TCPE linker in the MOFs. If the 2PA cross section value is indeed
influenced by an increased charge polarization (design criterion
a) listed above, then this would suggest highest 2PA cross section
values for a C-C distance of 16 Å.
withdrawing TFA group is connected to the metal node of Zr-MOF
-
3
, the charge transfer increases to 1.2 e , while the conformation
and strain of the incorporated TCPE is hardly affected. Thus, the
only significant difference between 3 and 4 is the enhanced
charge transfer in 3 caused by the TFA co-ligand. In line with
design criterion a) above, we thus attribute the increased MPA of
the top performing MOF 3 (Figure 2) to this enhanced polarization
of the chromophore.
To our knowledge, this is the first time that the influence of
strain-induced charge polarization on 2PA cross section values of
chromophore molecules has been investigated. As the explicit
calculation of the 2PA cross section values for a charged
chromophore is an unresolved challenge, we focus here on the
In addition to the charge transfer, the TCPE linker in a MOF is
strained and constrained in a plane. According to design criterion
a) an increased charge polarization of a chromophore molecule
4
neutral H TCPE. The two-photon transition tensor elements for a
transition from the ground state ⟨0| to the excited state |푓⟩ are
calculated by the sum-over-state formula
enhances its NLO properties.[5b,
12,
19]
However, it is not
훼
훽
훽
훼
immediately clear how the charge polarization of a molecule is
affected by strain. To assess this, we again use computed
Hirshfeld charges and focus on the neutral and the positively
⟨0|휇 |푖⟩ꢀ푖ꢁ휇 ꢁ푓ꢂ ꢀ0ꢁ휇 ꢁ푖ꢂ⟨푖|휇 |푓⟩
푆훼훽 = ∑ [
+
] ,
(1)
휔ꢄ
휔ꢄ
휔 −
휔 −
ꢃ
푖
ꢃ
2
2
where ω
흁
i
is the excitation energy for the intermediate state |풊⟩ and
is the electronic dipole operator. For randomly oriented gas-
4
charged free H TCPE molecule as simple model for the MOF-
휶,휷
incorporated TCPE linker. Specifically, we consider the difference
of the Hirshfeld charges on the inner tetraphenylethylene group
and the Hirshfeld charges on the four outer phenyl carboxylic acid
groups as an effective measure of a desirable multipolar charge
distribution. With a net negative charge on the inner group and a
phase molecules, the 2PA cross section is given by orientational
averaging over the two-photon absorption probability.[20] Figure 4b
shows the three highest 2PA values and their transition energies.
Comparing Figure 4a and Figure 4b, we see that the change in
charge polarization as derived from the Hirshfeld charge measure
indeed impacts the 2PA as expected. Exactly as found for the
Hirshfeld charges, the 2PA is highest for a C-C distance of 16 Å
net positive charge on the outer groups, already the free H
4
TCPE
molecule exhibits such multipolarity. To mimic the
a
conformational strain of the TCPE linker caused by binding to the
metal nodes within a MOF, we now vary the C-C distances
between the carboxylate carbon atoms in the range between 12
Å and 19 Å as illustrated in Figure 4. In MOFs 1-6 the carboxylate
groups of the TCPE linker are fixed in one common plane by the
(
Supporting Information, Table S10), i.e. a value that is close to
the strain parameters of MOFs 1, 2 and 3 (vertical lines in Figure
b).
4
The 2PA values from Figure 4b are calculated assuming a
random orientation of H TCPE in the gas phase. However, the
metal nodes. To account for this, we keep the CO
2
H groups fixed
4
in the xy-plane, while the remaining H TCPE molecule is fully
4
samples in this work are powders of micro-crystalline MOFs. Only
these crystals are randomly oriented during the measurement,
while within a MOF crystal the linkers are specifically ordered. At
present, the calculation of NLO properties for periodic systems
relaxed. Figure 4a shows that the charge polarization as
measured by the Hirshfeld charge difference is indeed strongly
affected by the conformational strain. For both the neutral and the
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with up to 648 atoms is
computationally
prohibitive.
Nevertheless, if the linkers behave
near independently, then their
contributions will be additive.[12] To
approximately account for the short-
range molecular order within a MOF
crystal, we thus use the molecular
푺휶휷 (Supporting Information, Table
S10) to calculate the two-photon
transition tensor elements of the unit
cell in a simplified model. This model
neglects any molecular correlation
effects beyond their tensor elements
푺휶휷, as well as the influence of the
nodes
and
co-ligands.
After
summing up the corresponding
tensor elements 푺휶휷 of each
molecule in the MOF structure,
orientational averaging is applied to
account for the random orientation of
the MOF micro-crystals (see
Supporting Information, Section 4.4).
For 1 and 2 (cubic lattice), we
use 푆훼훽 of H
distance of 15 Å, and for 3-6
kagome lattice) the 17 Å tensor
elements are used. This leads to
PA cross section values of 35
GM/chromophore for 1 and 2 and
63 GM/chromophore for 3-6. This
relative trend is in excellent
agreement with our experimental
findings, which differentiates the
MOFs 1-6 into two groups (Figure 3).
These results demonstrate the
importance of the details of the linker
4
TCPE with a C-C
(
2
Figure 4. Calculated change in charge polarization, the symmetry allowed energy transitions and the
4
2PA for a free H TCPE molecule. As illustrated by the molecular geometries in the top row, the C-C
1
distance of the molecule is varied from 12 Å to 19 Å to mimic the conformational strain on a TCPE linker
in a MOF. a) Difference of calculated Hirshfeld charges on the inner tetraphenylethylene group and on the four
outer phenyl carboxylic acid groups as effective measure of a desirable multipolar charge distribution. The two
molecular moieties are drawn with different shadings in the molecules in the top row. A positively charged
1
H
4
TCPE+ exhibits a three times enhanced polarization as compared to the neutral H
4
TCPE molecule (see text).
2
, colored triangles; right hand axis) and their transition energies (colored
b) The three highest 2PA values (
bars; left hand axis) for the neutral molecule. Both, the Hirshfeld charge difference and the 2PA, are highest for
a C-C distance of 16 Å, i.e. a value that falls between the strain parameters of MOFs 1, 2 (vertical dashed lines)
and MOF 3 (vertical solid line).
conformation,
strain,
crystal
structure and the arrangement of the
4
300 GM for this latter compound, i.e. a value that even exceeds
linkers when designing MOFs for MPA applications. The MPA
properties are most likely further enhanced by additional
intermolecular coupling of the linkers, charge transfer through the
nodes and co-ligands. Indeed, the enhanced MPA properties of
the one of our previously top-performing MOF 3 (Supporting
Information, Figure S17 and Table S4). The model presented in
this work is correspondingly
a first step to evaluate the
chromophore linker arrangement quantitatively and it can give a
first indication whether a MOF is a promising candidate for MPA
applications. However, if correlation effects between the
chromophore linkers beyond the 푆훼훽 tensor elements play a
dominant role, the model will not be sufficient to describe the
system.
some thin film materials which feature aggregated chromophores,
e.g. porphyrins, were assigned to such intramolecular coupling.[12]
From our model, we deduce that the 2PA would be maximized
in a MOF with a planar arrangement of the TCPE linker, as then
the 푆훼훽 would be the sum of all molecules. A good representation
of such an ideal arrangement is for example given by [Zn (TCPE)],
2
a MOF known for its high quantum efficiency.[9c] The model thus
In conclusion, the modular building block principle and
reticular chemistry of crystalline coordination networks, of which
allows to quickly evaluate existing TCPE-based MOF structures
for their MPA performance. For example, we estimate 2PA cross
MOFs represent
a prominent sub-class, provide unique
opportunities to design crystalline structures with distinct NLO and
section
Cd (TCPE)1.5(H
K[Bi(TCPE)(DMF)
GM/chromophore for the above mentioned [Zn
Indeed, in full accordance with the model we measure a value of
values
O)
] (DMF = N,N-dimethylformamide) , and 170
of
(DMF)] [21], 165 GM/chromophore for
2
156
GM/chromophore
for
other photo-physical properties.[7b,
23]
Framework-integrated
[
3
2
[
22]
chromophores in MOFs show increased stability against thermal,
chemical and light induced degradation, along with reduced
sensitivity towards water and various solvents.[9b, 13, 15] The metal
ions of the nodes can be chosen to facilitate the synthesis process
2
(TCPE)] 9c].
[
2
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and to enhance the stability of the crystal. In this contribution, we
demonstrated how such MOFs can be specifically designed for
MPA applications by fulfilling a range of design concepts. This
allowed us to reach unprecedentedly high 2PA values. We
developed a quantitative model that is useful to evaluate existing
structures of MOFs and crystalline coordination networks in
general. It predicts that the intrinsic MPA properties can be further
increased in MOFs by maximizing the two-photon transition
tensor of the unit cell. Our results show how this can be achieved
by the control of the arrangement of rigidified and at the same
time suitably strained NLO chromophore linkers in a high packing
density together with the adjustment of charge transfer by
additional co-ligands attached to the nodes.
[6]
a) A. Burns, H. Ow, U. Wiesner, Chem. Soc. Rev. 2006, 35, 1028-1042;
b) S. W. Thomas, G. D. Joly, T. M. Swager, Chem. Rev. 2007, 107, 1339-
1386.
[
[
7]
8]
a) O. M. Yaghi, M. O'Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, J.
Kim, Nature 2003, 423, 705-714; b) H. Furukawa, K. E. Cordova, M.
O’Keeffe, O. M. Yaghi, Science 2013, 341, 1230444.
a) H. K. Chae, D. Y. Siberio-Perez, J. Kim, Y. Go, M. Eddaoudi, A. J.
Matzger, M. O'Keeffe, O. M. Yaghi, Nature 2004, 427, 523-527; b) H.-C.
Zhou, J. R. Long, O. M. Yaghi, Chem. Rev. 2012, 112, 673-674.
a) R. Medishetty, J. K. Zareba, D. Mayer, M. Samoc, R. A. Fischer, Chem.
Soc. Rev. 2017, 46, 4976-5004; b) Z. Wei, Z.-Y. Gu, R. K. Arvapally, Y.-
P. Chen, R. N. McDougald, J. F. Ivy, A. A. Yakovenko, D. Feng, M. A.
Omary, H.-C. Zhou, J. Am. Chem. Soc. 2014, 136, 8269-8276; c) Z. Hu,
G. Huang, W. P. Lustig, F. Wang, H. Wang, S. J. Teat, D. Banerjee, D.
Zhang, J. Li, Chem. Commun. 2015, 51, 3045-3048.
[9]
[
10] a) J. Yu, Y. Cui, C. Wu, Y. Yang, Z. Wang, M. O'Keeffe, B. Chen, G. Qian,
Angew. Chem. Int. Ed. 2012, 51, 10542-10545; b) J. Yu, Y. Cui, H. Xu,
Y. Yang, Z. Wang, B. Chen, G. Qian, Nature Commun. 2013, 4, 2719; c)
H. He, E. Ma, Y. Cui, J. Yu, Y. Yang, T. Song, C.-D. Wu, X. Chen, B.
Chen, G. Qian, Nature Commun. 2016, 7, 11087.
Acknowledgements
R.M. is grateful to the Alexander von Humboldt foundation for a
post-doctoral fellowship. L.N. and K.R. acknowledge funding by
the German Federal Ministry of Education and Research (BMBF)
within project "ELPA-AEO" (project number 01IH15001). V.N.
would like to thank the Singapore Ministry of Education Academic
Research Fund Tier 3 (Grant MOE2011-T3-1-005) for financial
[
[
11] G. S. He, Nonlinear Optics and Photonics, Oxford University Press, 2014.
12] E. Collini, Phys. Chem. Chem. Phys. 2012, 14, 3725-3736.
[13] Q. Zhang, J. Su, D. Feng, Z. Wei, X. Zou, H.-C. Zhou, J. Am. Chem. Soc.
2015, 137, 10064-10067.
[14] a) M. Rumi, J. W. Perry, Adv. Opt. Photon. 2010, 2, 451-518; b) N. S.
Makarov, M. Drobizhev, A. Rebane, Opt. Express 2008, 16, 4029-4047.
[15] R. Medishetty, V. Nalla, L. Nemec, S. Henke, D. Mayer, H. Sun, K. Reuter,
R. A. Fischer, Adv. Mater. 2017, 29, 1605637.
[
support.
013/10/A/ST4/00114. R.A.F. acknowledges the German
Research Foundation for the installation of Priority Program 1928
COORNETs” (http://www.coornets.tum.de). The authors also
M.S.
acknowledges
NCN
grant
UMO-
2
16] K. Aidas, C. Angeli, K. L. Bak, V. Bakken, R. Bast, L. Boman, O.
Christiansen, R. Cimiraglia, S. Coriani, P. Dahle, E. K. Dalskov, U.
Ekström, T. Enevoldsen, J. J. Eriksen, P. Ettenhuber, B. Fernández, L.
Ferrighi, H. Fliegl, L. Frediani, K. Hald, A. Halkier, C. Hättig, H. Heiberg,
T. Helgaker, A. C. Hennum, H. Hettema, E. Hjertenæs, S. Høst, I.-M.
Høyvik, M. F. Iozzi, B. Jansík, H. J. A. Jensen, D. Jonsson, P. Jørgensen,
J. Kauczor, S. Kirpekar, T. Kjærgaard, W. Klopper, S. Knecht, R.
Kobayashi, H. Koch, J. Kongsted, A. Krapp, K. Kristensen, A. Ligabue,
O. B. Lutnæs, J. I. Melo, K. V. Mikkelsen, R. H. Myhre, C. Neiss, C. B.
Nielsen, P. Norman, J. Olsen, J. M. H. Olsen, A. Osted, M. J. Packer, F.
Pawlowski, T. B. Pedersen, P. F. Provasi, S. Reine, Z. Rinkevicius, T. A.
Ruden, K. Ruud, V. V. Rybkin, P. Sałek, C. C. M. Samson, A. S. de Merás,
T. Saue, S. P. A. Sauer, B. Schimmelpfennig, K. Sneskov, A. H. Steindal,
K. O. Sylvester-Hvid, P. R. Taylor, A. M. Teale, E. I. Tellgren, D. P. Tew,
A. J. Thorvaldsen, L. Thøgersen, O. Vahtras, M. A. Watson, D. J. D.
Wilson, M. Ziolkowski, H. Ågren, WIREs Comput. Mol. Sci. 2014, 4, 269-
284.
“
would like to thank Prof. Dr. Egbert Zojer and Dr. Ashok Keerthi
for fruitful discussions. R.M., L.N., V.N., K.R. and R.A.F.
conceived the idea. R.M. synthesized and characterized the
compounds. L.N. performed DFT and TDDFT calculations of
optical properties calculations and the theoretical modeling. V.N.
performed the experimental nonlinear optical studies. S.H.
performed the crystallographic analyses. M.S. helped discussing
the measurement procedures. L.N., R.M., K.R., R.A.F. wrote the
manuscript with contributions from all the authors.
Conflict of interest
[
[
[
17] T. Yanai, D. P. Tew, N. C. Handy, Chem. Phys. Lett. 2004, 393, 51-57.
18] F. L. Hirshfeld, Theor. Chim. Acta 1977, 44, 129-138.
The authors declare no conflict of interest.
19] E. Zojer, D. Beljonne, P. Pacher, J.-L. Brédas, Chem. Eur. J. 2004, 10,
2
668-2680.
Keywords: metal-organic frameworks • nonlinear optics •
photon upconversion • TDDFT • charge polarization
[
20] P. R. Monson, W. M. McClain, J. Chem. Phys. 1970, 53, 29-37.
[21] W. Yang, G. Chang, H. Wang, T.-L. Hu, Z. Yao, K. Alfooty, S. Xiang, B.
Chen, Eur. J. Inorg. Chem. 2016, 2016, 4470-4475.
[
[
22] B. J. Deibert, E. Velasco, W. Liu, S. J. Teat, W. P. Lustig, J. Li, Cryst.
Growth Des. 2016, 16, 4178-4182.
[
[
[
1]
2]
3]
F. Helmchen, W. Denk, Nat. Methods 2005, 2, 932-940.
M. Wuttig, N. Yamada, Nature Mater. 2007, 6, 824-832.
23] a) C. E. Wilmer, M. Leaf, C. Y. Lee, O. K. Farha, B. G. Hauser, J. T. Hupp,
R. Q. Snurr, Nature Chem. 2012, 4, 83-89; b) H. S. Quah, W. Chen, M.
K. Schreyer, H. Yang, M. W. Wong, W. Ji, J. J. Vittal, Nature Commun.
P.-A. Bouit, G. Wetzel, G. Berginc, B. Loiseaux, L. Toupet, P. Feneyrou,
Y. Bretonnière, K. Kamada, O. Maury, C. Andraud, Chem. Mater. 2007,
19, 5325-5335.
2015, 6, 7954.
[
[
4]
5]
S. Kawata, H. B. Sun, T. Tanaka, K. Takada, Nature 2001, 412, 697-698.
a) G. S. He, L.-S. Tan, Q. Zheng, P. N. Prasad, Chem. Rev. 2008, 108,
1245-1330; b) M. Pawlicki, H. A. Collins, R. G. Denning, H. L. Anderson,
Angew. Chem. Int. Ed. 2009, 48, 3244-3266; c) M. Albota, D. Beljonne,
J.-L. Brédas, J. E. Ehrlich, J.-Y. Fu, A. A. Heikal, S. E. Hess, T. Kogej, M.
D. Levin, S. R. Marder, D. McCord-Maughon, J. W. Perry, H. Röckel, M.
Rumi, G. Subramaniam, W. W. Webb, X.-L. Wu, C. Xu, Science 1998,
281, 1653-1656.
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Angewandte Chemie International Edition
10.1002/anie.201706492
COMMUNICATION
Table of Contents
COMMUNICATION
†
Raghavender Medishetty, Lydia
†
Nemec, Venkatram Nalla,* Sebastian
Henke, Marek Samoć, Karsten Reuter,*
Roland A. Fischer*
Page No. – Page No.
Multi-Photon Absorption in Metal-
Organic Frameworks
Text for Table of Contents
Nonlinear optical properties in MOFs have been enhanced to record high multi-photon absorption
cross section values by following five design criteria, supported by theory.
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