[Supporting Information (SI) to accompany:]
Turning on Catalysis: Incorporation of a Hydrogen-Bond-Donating Squaramide Moiety
into a Zr Metal−Organic Framework
C. Michael McGuirk,† Michael J. Katz, † Charlotte L. Stern, † Amy A. Sarjeant, † Joseph T.
Hupp,* † Omar K. Farha,* †‡ and Chad A. Mirkin*†
†
Department of Chemistry and the International Institute for Nanotechnology, Northwestern
University, 2145 Sheridan Road, Evanston, Illinois 60208−3113, United States
‡
Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
* [email protected]; [email protected]; [email protected]
Table of Contents
Synthesis of Squaramide Struts
Synthesis of Ethynyl−Squar
Synthesis of MOFs
Isotherms of MOFs
Heteronuclear NMR Spectra of Digested MOFs
S2−S3
S3
S3−S5
S5
S5−S11
SEM and TEM
S12
General Procedure for Catalysis
S13
1
S13−S14
Chiral HPLC
S14−S15
Filter Tests
S15−S16
H NMR Spectra of Reaction
MOF Recycling Test
Post Catalysis 1H NMR Spectrum
General Procedure for Catalysis with Pyrrole
Crystal Structures of Me2−Squar and Me2−Urea
S16
S16−17
S17
S17−S20
Idealized Structure of Urea Self-Association
S21
References
S21
S1
Synthesis of Me2−Squar
To a anhydrous mixture of toluene:dimethylformamide (19:1, 20 mL) was added
3−((3,5−bis(trifluoromethyl)phenyl)amino)−4−methoxycyclobut−3−ene−1,2−dione (1.08 g, 3.18
mmol) and zinc trifluoromethanesulfonate (230 mg, 0.63 mmol). The suspension was stirred
vigorously for 10 min at RT. To the mixture dimethyl 2−aminobiphenyl−4,4’−dicarboxylate
was added at once (1.00 g, 3.50 mmol). The mixture was heated to 100 °C and stirred overnight.
The reaction was cooled to −20 °C and filtered. The retentate was washed with toluene and
hexanes. The solid was dried to give a yellow solid (980 mg, 52% yield). 1H NMR (400.16 MHz,
25 °C, DMSO−d6): δ 10.19 (br s, 1H), 9.69 (br s, 1H) 8.05 (d, JH–H = 8 Hz, 2H), 7.94 (d, JH–H = 4
Hz, 2H), 7.86 (m, 2H), 7.71 (d, JH–H = 8 Hz, 2H), 7.68 (br s, 1H), 7.53 (d, JH–H = 8 Hz, 1H), 3.89
(s, 3H), 3.88 (s, 3H). ESIMS (m/z): 592 [M]+. Found 593.
Synthesis of H2−Squar
To 50 mL of acetic acid (99%) was added 800 mg (1.35 mmol) of Me2−Squar, and the mixture
was stirred for 5 min at RT. To the mixture was added 50 mL of H2SO4 (98%). With vigorous
stirring was added 10 mL of water dropwise, in order to maintain one homogenous phase. The
S2
reaction was stirred at 50 °C for 48 hr. The reaction was cooled to 0 °C, and ice water was added
dropwise with vigorous stirring. Upon cooling, the mixture was filtered over a glass frit. The
retentate was washed with water (3 x 200 mL). The solid retentate was dried under high vac to
yield H2−Squar as a yellow solid (343 mg, 45% yield). 1H NMR (400.16 MHz, 25 °C,
DMSO−d6): δ 10.21 (br s, 1H), 9.66 (br s, 1H), 8.04 (d, JH–H = 8 Hz, 2H), 7.84 (m, 2H), 7.68 (br
s, 1H), 7.67 (d, JH–H = 8 Hz, 2H), 7.57 (d, JH–H = 8 Hz, 1H), 7.51 (d, JH–H = 8 Hz, 1H), 7.46 (d,
JH–H = 8 Hz, 1H). 13C{1H} NMR (100.6 MHz, 25 °C, DMSO−d6): δ 185.3, 183.0, 167.5, 167.4, 167.1,
167.0, 142.4, 141.9, 137.2, 135.5, 131.5, 130.8, 130.5, 130.1, 129.9, 126.3, 125.6, 122.4, 119.4, 116.0.
ESIMS (m/z): 582 [M+H2O]+. Found 583.
Synthesis of
3−((3,5−bis(trifluoromethyl)phenyl)amino)−4−((4−ethynylphenyl)amino)−3−ene−1,2−dione
(Ethynyl−Squar)
To a anhydrous mixture of toluene:dimethylformamide (6:1, 10 mL) was added
3−((3,5−bis(trifluoromethyl)phenyl)amino)−4−methoxycyclobut−3−ene−1,2−dione (540 mg,
1.59 mmol) and zinc trifluoromethanesulfonate (115 mg, 0.32 mmol). The suspension was stirred
vigorously for 10 min at RT. To the mixture 4−ethynylaniline was added at once (146 mg, 1.25
mmol). The mixture was heated to 50 °C and stirred for 3 days. The reaction was cooled to RT
and filtered. The retentate was washed with toluene and hexanes. The retentate was then
recrystallized from DMSO. The resulting precipitate was filtered and washed with DMSO and
diethyl ether. The solid was dried to give a pale yellow/white solid (318 mg, 60% yield). 1H
NMR (400.16 MHz, 25 °C, DMSO−d6): δ 10.37 (br s, 1H), 10.17 (br s, 1H), 8.05 (s, 2H), 7.75
(s, 1H), 7.49 (d, JH–H = 8 Hz, 2H), 7.43 (d, JH–H = 8 Hz, 2H), 4.15 (s, 1H). ESIMS (m/z): 424
[M]−. Found 423.
Synthesis of UiO−67
All UiO−67 materials were synthesized using the following general procedure. An 8-dram vial
was loaded with ZrCl4 (67 mg, 0.29 mmoles), which was purchased from Aldrich and kept in an
Ar(g) glovebox, one third of the DMF, and 0.5 mL of HCl before being sonicated for 20 minutes
until fully dissolved. The mixture of ligands (Table S1) and the remainder of the DMF were then
added and the mixture was sonicated an additional 20 minutes before being heated at 80 °C
overnight (bpdc was not completely soluble under these conditions). For UiO−67, the resulting
solid was filtered and washed first with DMF (2x 30 mL) and then with EtOH (2x 30mL).
UiO−67 was subsequently heated at 90 °C under vacuum until a pressure of 100 mtorr was
S3
reached. The samples were then heated to 150 °C under vacuum for 24 hours. For all the other
samples, the reaction mixture was centrifuged and the solvent exchanged for DMF several times
in order to remove any unreacted starting material. Subsequently, the MOF was soaked in EtOH
for 3 days, replacing both at the beginning and end of the day to ensure complete solvent
exchange. Samples were subsequently supercritical CO2 dried.
Table S1: Masses of linkers used to make various UiO−67 derivatives.
MOF
Amount of bpdc
(mmoles)
Amount of other linker
(mmoles)
BET surface area
(m2/g)
UiO−67
90 mg (0.372)
0 mg
2500 4
UiO−67−Squar
0 mg
210 mg (0.372)
530
UiO−67−Squar/bpdc 45 mg (0.186)
105 mg (0.186)
1700
UiO−67−Urea
0 mg
153 mg (0.372)
390 2
UiO−67−Urea/bpdc
45 mg (0.186)
77 mg (0.186)
1550 2
Figure S1: General synthesis scheme for UiO-67-Urea/bpdc
Synthesis of UiO−66
UiO−66 was synthesized using the following procedure. An 8-dram vial was loaded with ZrCl4
(67 mg, 0.29 mmoles), which was purchased from Aldrich and kept in an Ar(g) glovebox, one
third of the DMF, and 0.5 mL of HCl before being sonicated for 20 minutes until fully dissolved.
Terephthalic acid and the remainder of the DMF were then added and the mixture was sonicated
an additional 20 minutes before being heated at 80 °C overnight. The resulting solid was filtered
and washed first with DMF (2x 30 mL) and then with EtOH (2x 30mL). UiO−66 was
subsequently heated at 90 °C under vacuum until a pressure of 100 mtorr was reached. The
S4
sample was then heated to 150 °C under vacuum for 24 hours. Samples were subsequently
supercritical CO2 dried.
Figure S2: N2 isotherms of UiO−67 (blue circles), UiO−67−Squar/bpdc (red triangles), and
UiO−67−Squar (green squares). The isotherms of the urea derivatives have been reported
elsewhere.2
(A)
(B)
(C)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ppm
Figure S3: 1H NMR spectra (400 MHz) of (A) UiO−67, (B) UiO−67−Squar, and (C)
UiO−67−Squar/bpdc. Samples were prepared in DMSO−d6 with minimal D2SO4.
S5
(A)
(B)
bpdc strut
(4H)
(C)
8.45
8.35
8.25
8.15
8.05
7.95
7.85
7.75 7.65
ppm
7.55
0.83
1.10
1.00
3.82
Squaramide strut
(3H)
7.45
7.35
7.25
7.15
7.05
6.95
Figure S4: Zoomed in 1H NMR spectra (400 MHz) of (A) UiO−67, (B) UiO−67−Squar, and (C)
UiO−67−Squar/bpdc. Samples were prepared in DMSO−d6 with minimal D2SO4.
(A)
(B)
(C)
10.0
9.0
8.0
7.0
6.0
5.0
ppm
4.0
3.0
2.0
1.0
0.0
S6
Figure S5: 1H NMR spectra (400 MHz) of (A) UiO−67, (B) UiO−67−Urea, and (C)
UiO−67−Urea/bpdc. Samples were prepared in DMSO−d6 with minimal D2SO4.
(A)
(B)
bpdc strut
(4H)
(C)
8.40
8.30
8.20
8.10
8.00
1.00
4.04
Urea strut
(1H)
7.90
7.80
7.70
ppm
7.60
7.50
7.40
7.30
7.20
7.10
7.00
Figure S6: Zoomed in 1H NMR spectra (400 MHz) of (A) UiO−67, (B) UiO−67−Urea, and (C)
UiO−67−Urea/bpdc. Samples were prepared in DMSO−d6 with minimal D2SO4.
S7
Figure S7: Zoomed in 1H NMR Spectrum (400 MHz) of UiO−67−Squar/bpdc with CH2Cl2
internal standard. Sample was prepared in DMSO−d6 with minimal D2SO4. CH2Cl2 loaded at
approximately 12-fold moles compared to calculated MOF unit cell. Integrations confirm
average Zr6(OH)4(O)4(Squar)2(bpdc)2 unit cell.
Figure S8: Zoomed in 1H NMR Spectrum (400 MHz) of UiO−67−Squar/bpdc with
dichloroethane (4H) internal standard. Sample was prepared in DMSO−d6 with minimal D2SO4.
Dichloroethane loaded at approximately 10-fold moles compared to calculated MOF unit cell.
Integrations confirm average Zr6(OH)4(O)4(Squar)2(bpdc)2 unit cell.
S8
Figure S9: 13C{1H} NMR spectrum (100.6 MHz) of UiO−67−Squar/bpdc. Sample was prepared
in DMSO−d6 with minimal D2SO4. 20,000 scans were taken of saturated solution. Spectrum
shows diagnostic peaks at 186.57 and 184.28 ppm belonging to squaramide moiety.
S9
Figure S10: Zoomed in 1H NMR spectra (400 MHz) of different synthesized batch of
UiO−67−Squar/bpdc. Sample prepared in DMSO−d6 with minimal D2SO4. All synthesized
batches consistently show same 1:1 ratio of squaramide ligand and bpdc ligand.
Figure S11: Zoomed in 1H NMR spectra (400 MHz) of different synthesized batch of
UiO−67−Urea/bpdc. Sample prepared in DMSO−d6 with minimal D2SO4. All synthesized
batches consistently show same 1:1 ratio of urea ligand and bpdc ligand.
S10
35
Figure
S12:
Cl
NMR
(39.3
MHz)
of
chloride-containing
control,
bis(triphenylphosphine)iminium chloride (PPNCl). Loaded 5 mg (MW = 574.03) in 0.5 mL
DMSO−d6. 16 scans taken.
S11
Figure S13: 35Cl NMR (39.3 MHz) of saturated solution of UiO−67−Squar/bpdc. Sample
prepared in DMSO−d6 with minimal D2SO4. 5,000 scans taken. Additionally, elemental analysis
showed no detectable chloride in UiO−67−Squar/bpdc.
Figure S14: SEM (left) and TEM (right) images of UiO−67−Squar/bpdc. UiO−67−Squar/bpdc
was analyzed using a Hitachi HD-2300 scanning transmission electron microscope (STEM) in
the SE and TE mode with an accelerating voltage of 200 kV. Samples were dispersed onto TEM
grids by dropcasting a dilute MeOH solution containing the MOF directly onto TEM grids.
S12
General Procedure for Catalysis Experiments
To a stirring slurry of 10 mol% catalyst in CD2Cl2 (0.3 mL) at 0 °C was added a solution of
β−nitrostyrene (2.1 mg in 0.2 mL CD2Cl2). Then, a solution of indole (2.4 mg in 0.2 mL CD2Cl2)
was added. The reaction was stirred at RT for 24 hr. Aliquots were taken and diluted with
CD2Cl2. Reaction progress was monitored by 1H NMR spectroscopy using the integration of
α−vinyl proton of β−nitrostyrene (δ = 8.05 ppm) and the resulting aliphatic protons of the
product 3−(2−Nitro−1−phenylethyl)−1H−indole (δ = 5.00−5.06 ppm). Mesitylene was used as
the internal standard. Product can be isolated by filtration, removal of solvent under reduced
pressure, then silica gel column chromatography (10:1 petroleum ether:ethyl acetate, then pure
ethyl acetate). ee% determined by chiral HPLC.5
Figure S15: Zoomed in in situ 1H NMR spectrum (400 MHz) of catalytic reaction between
indole and β−nitrostyrene to form 3−(2−Nitro−1−phenylethyl)−1H−indole in the presence of
UiO−67−Squar/bpdc in CD2Cl2 at RT.
S13
Figure S16: 1H NMR spectrum
3−(2−Nitro−1−phenylethyl)−1H−indole.
(400
MHz,
CD2Cl2)
of
isolated
product,
Chiral HPLC for ee% Determination
Table S2: Data from three runs on chiral HPLC for product isolated from reaction catalyzed
with UiO−67−Squar/bpdc in CD2Cl2 at RT.
Column:
Solvent:
Flow Rate:
Major Peak Rf
Major Peak Area
Minor Peak Rf
Minor Peak Area
% Major
% Minor
% ee
Chiralcel
OD-H
Hex / IPA (70/30)
1 mL/min
Run 1
21.88
2332.91
19.13
2327.71
50.06
49.94
0.11
Run 2
18.77
2301.83
21.49
2287.36
50.16
49.84
0.32
Run 3
21.46
2314.54
18.728
2313.15
50.02
49.98
0.03
Average
50.08
49.92
0.15
S14
Figure S17: Chiral HPLC traces from three runs on chiral HPLC for product isolated from
reaction catalyzed with UiO−67−Squar/bpdc in CD2Cl2 at RT.
(A)
(A)
(B)
B)
S15
Figure S18: Filter tests were performed with the same procedure detailed above under “General
Procedure for Catalysis Experiments”. For UiO−67−Squar/bpdc (A), reaction progress was
measured after 2.5 hr, and then the mixture was filtered through a PTFE microfilter. Reaction
progress was again measured after 24 hr. For UiO−67, reaction progress was measured after 4 hr
(B), and then the mixture was filtered through a PTFE microfilter. Reaction progress was again
measured after 24 hr.
Figure S19: Recycling test performed with UiO−67−Squar/bpdc in CD2Cl2 at RT. MOF isolated
by filtration after each use. We attribute the slight decrease in activity to catalyst loss during
filtration.
S16
Figure S20: Zoomed in 1H NMR spectrum (400 MHz, CD2Cl2) of UiO−67−Squar/bpdc isolated
by filtration post-catalysis (RT, CD2Cl2). After filtration, the sample was prepared in DMSO−d6
with minimal D2SO4. Importantly, we see the squaramide moiety remains intact (~7.4−7.6 ppm).
Additionally, there is no detectable product trapped in the MOF (~4.8−5.2 ppm).
General Procedure for Catalysis Experiments with Pyrrole
To a stirring slurry of 10 mol% catalyst in CD2Cl2 (0.3 mL) at 0 °C was added a solution of
β−nitrostyrene (2.1 mg in 0.2 mL CD2Cl2). Then, a solution of pyrrole (1.4 μL in 0.2 mL
CD2Cl2) was added. The reaction was stirred at RT for 24 hr. Aliquots were taken and diluted
with CD2Cl2. Reaction progress was monitored by 1H NMR spectroscopy using the integration of
α−vinyl proton of β−nitrostyrene (δ = 8.05 ppm) and the resulting aliphatic protons of the
product 2-(2-Nitro-1-phenylethyl)-1H-pyrrole (δ = 4.70−5.00 ppm). Mesitylene was used as the
internal standard.
Figure S21: Single crystals of Me2−Squar suitable for an X-ray diffraction study were grown via
recrystallization from hot DMSO. The solid-state structure confirms the modification of the
amino-functionalized strut with the HBD squaramide functionality. The squaramide moiety is
S17
coplanar with the electron withdrawing 3,5−bis(trifluoromethyl)phenyl group. Also, in the solidstate the squaramide moiety demonstrates the ability to rotate out of the plane of the biphenylene
backbone, therefore adopting preferential spatial conformations for accessing HBA substrates.
Thermal ellipsoids drawn to 50 % probability: C, gray; O, red; N, blue; F, green; S, yellow; H,
white.
A suitable crystal was selected and mounted in inert oil and transferred to the cold gas
stream of a Bruker Kappa APEX CCD area detector diffractometer. The crystal was kept at
99.99 K during data collection. Using Olex2, the structure was solved with the XM [2] structure
solution program using Dual Space and refined with the XL refinement package using Least
Squares minimization.
Chemically equivalent distances in disordered species were refined with similarity
restraints (SADI). The disordered atoms of the DMSO molecule were refined with group
anisotropic displacement parameters. The enhanced rigid bond restraint (RIGU) was applied
globally. Crystals of this material showed evidence of a supercell of approximately 12.6 35.2
13.6 90 108.8 90. A structure was obtained for this cell in the spacegroup P2(1) however, data
quality were poor and most atoms remained non-positive definite. We elected to present the
substructure here with this disordered model, which represents four unique molecules (and
DMSO solvents) in the superstructure.
Table S3: Crystallographic Information Table for Me2−Squar
Empirical formula
C30H24F6N2O7S
Formula weight
670.57
Temperature (K)
99.99
Crystal system
monoclinic
Space group
P21/c
A (Å), b (Å), c (Å)
10.6680(4), 35.2141(14), 7.6499(3)
α (°), β (°), γ (°)
90, 94.455(2), 90
Volume (Å3)
2865.11(19)
Z
4
Calculated Density (mg mm-3)
1.555
Absorption Coefficient (mm-1)
1.835
F(000)
1376
Crystal size (mm3)
0.108 × 0.086 × 0.038
S18
2Θ range for data collection
5.018 to 132.856°
Index ranges
-9 ≤ h ≤ 12, -39 ≤ k ≤ 41, -6 ≤ l ≤ 9
Reflections collected
13880
Independent reflections
4961[R(int) = 0.0177]
Data/restraints/parameters
4961/666/543
Goodness-of-fit on F2
1.037
Final R indexes [I>2σ (I)]
R1 = 0.0432, wR2 = 0.0987
Final R indexes [all data]
R1 = 0.0474, wR2 = 0.1017
Largest diff. peak/hole (e Å-3)
0.504/-0.818
Figure S22: Single crystals of Me2−Urea suitable for an X-ray diffraction study were grown via
recrystallization from hot MeCN. The solid-state structure confirms the modification of the
amino-functionalized strut with the HBD urea functionality. In the solid-state, the urea moiety is
coplanar with both the electron withdrawing 3,5−bis(trifluoromethyl)phenyl group and the
biphenylene backbone. Thermal ellipsoids drawn to 50 % probability: C, gray; O, red; N, blue; F,
green; H, white.
S19
A suitable crystal was selected and mounted in inert oil and transferred to the cold gas
stream of a Kappa Apex 2 diffractometer. The crystal was kept at 100.02 K during data
collection. Using Olex2, the structure was solved with the ShelXT [2] structure solution program
using Direct Methods and refined with the ShelXL refinement package using Least Squares
minimization.
No special refinement necessary.
Table S4: Crystallographic Information Table for Me2−Urea
Empirical formula
C27H21F6N3O5
Formula weight
581.47
Temperature (K)
100.02
Crystal system
triclinic
Space group
P-1
A (Å), b (Å), c (Å)
10.8859(4), 11.4845(5), 11.4884(5)
α (°), β (°), γ (°)
70.1060(18), 71.073(2), 89.5000(19)
Volume (Å3)
1269.17(9)
Z
2
Calculated Density (mg mm-3)
1.522
Absorption Coefficient (mm-1)
0.135
F(000)
596
Crystal size (mm3)
0.34 × 0.214 × 0.183
2Θ range for data collection
5.296 to 62.462°
Index ranges
-15 ≤ h ≤ 15, -12 ≤ k ≤ 16, -16 ≤ l ≤ 16
Reflections collected
17525
Independent reflections
8021[R(int) = 0.0339]
Data/restraints/parameters
8021/0/381
Goodness-of-fit on F2
0.864
Final R indexes [I>2σ (I)]
R1 = 0.0442, wR2 = 0.1164
Final R indexes [all data]
R1 = 0.0647, wR2 = 0.1275
S20
Largest diff. peak/hole (e Å-3)
0.615/-0.432
Figure S23: Idealized self-association of urea-based HBD organocatalysts.
References
(1) Ol’khovik, V. K.; Pap, A. A.; Vasilevskii, V. A.; Galinovskii, N. A.; Tereshko, S. N. Russ. J.
Org. Chem. 2008, 44, 1172.
(2) Siu, P. W.; Brown, Z. J.; Farha, O. K.; Hupp, J. T.; Scheidt, K. A. Chem. Commun. 2013, 49,
10920.
(3) Yang, W.; Du, D.-M. Org. Lett. 2010, 12, 5450.
(4) Katz, M. J.; Brown, Z. J.; Colon, Y. J.; Siu, P. W.; Scheidt, K. A.; Snurr, R. Q.; Hupp, J. T.;
Farha, O. K. Chem. Commun. 2013, 49, 9449.
(5) Liu, H; Du, D-M. Eur. J. Org. Chem. 2010, 11, 2121.
**Reference 1** For the synthesis of (II) equivalent moles of nitric acid and dimethyl
biphenyl−4,4’−dicarboxylate were used. The as written procedure gives the disubstituted
product.
S21