An imine-based molecular cage with distinct binding sites for small and large alkali metal cations

Article abstract of DOI:10.1002/chem.201300098

The synthesis of a cylindrical, imine-based cage composed of two trimeric metallamacrocycles is described. The cage acts as a heterotopic receptor for alkali metal cations. The small cations Li⁺, Na⁺, and K⁺ bind to the outside of the cage with good selectivity for Li ⁺, whereas the larger cations Rb⁺ and Cs⁺ are bound inside the cage to form unusual π complexes with a good selectivity for Cs⁺. Negative heterotopic cooperativity between the two binding sites is observed. The complexation of Cs⁺ is associated with a color change, which enables the cage to be used as a specific sensor for Cs ⁺. Copyright

Full text of DOI:10.1002/chem.201300098

Supporting Information
ꢀ Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2013
An Imine-Based Molecular Cage with Distinct Binding Sites for Small and
Large Alkali Metal Cations
Clꢀment Schouwey, Rosario Scopelliti, and Kay Severin*[a]
chem_201300098_sm_miscellaneous_information.pdf

TABLE OF CONTENTS
1. Syntheses
S2
S3
S4
S6
S8
S9
2. Crystallographic data for compounds 4·CsCl and 4·(LiCl)2.
2. 1H and 13C NMR spectra of 3 and 4
3. High-resolution ESI+-MS spectra of 3 and 4
4. Supplementary 1H NMR data
5. UV-VIS titrations
S1

1. Syntheses
Compounds (S2) and (S3): to a solution of S1 (1.50 g, 5.49 mmol) and tert-Butyl carbamate
(2.00 g, 17.1 mmol) stirred in 50 mL degassed acetonitrile under N2 were added Et3SiH (2.70
mL, 17.1 mmol) and CF3COOH (1.31 mL,17.1 mmol). The resulting solution was stirred for
3 days at r.t. The solvent was then evaporated under reduced pressure and the residue was
dissolved in 50 ml DCM and the organic phase was washed with 50 mL sat. aq. NaHCO3 and
50 mL H2O, then dried over anhyd. Na2SO4. The solvent was removed under reduced pressure
and the residue was purified by column chromatography (Al2O3 neutral deactivated with 5
w/w % H2O; eluent: DCM to DCM/acetone 1:1) to give one fraction of S2 (493 mg, 24 %)
and one fraction of S3 (922 mg, 51 %) as pale-yellow oils. (S2) 1H NMR (400 MHz, CDCl3):
3
δ = 1.45 (s, 9H, CH3), 3.52 (s, 3H, CH3), 4.38 (d, 2H, J = 5.6 Hz, CH2), 5.14 (s, 2H, CH3),
5.42 (s, 2H, CH2), 6.89 (d, 1H, 3J = 5.1 Hz, Ar-H), 7.30-7.46 (m, 5H, Ar-H), 7.88 (d, 1H, 3J =
13
5.1 Hz, Ar-H); C NMR (100 MHz, CDCl3): δ = 28.4 (CH3), 39.1 (CH2), 57.6 (CH3), 67.9
(CH2), 79.6 (Cq), 98.5 (CH2), 117.3 (CH), 127.8 (CH), 127.9 (CH), 128.4 (CH), 137.1 (Cq),
138.8 (Cq), 141.2 (Cq), 141.5 (CH), 155.9 (Cq), 156.4 (Cq); HRMS (ESI+): m/z = 375.1916 [M
+ H]+; calcd. for [C20H26N2O5 + H]+: 375.1920. (S3) 1H NMR (600 MHz, CDCl3): δ = 1.44 (s,
9H, CH3), 4.26 (d, 2H, 3J = 6.1 Hz, CH2), 5.38 (s, 2H, CH2), 6.73 (d, 1H, 3J = 4.9 Hz, Ar-H),
7.26-7.40 (m, 5H, Ar-H), 7.61 (d, 1H, 3J = 4.9 Hz, Ar-H); 13C NMR (150 MHz, CDCl3): δ =
28.4 (CH3), 39.1 (CH2), 68.1 (CH2), 80.1 (Cq), 117.6 (CH), 127.9 (CH), 128.2 (CH), 128.4
(CH), 132.6 (Cq), 136.3 (CH), 136.9 (Cq), 138.9 (Cq), 152.8 (Cq), 156.9 (Cq); HRMS (ESI+):
m/z = 331.1667 [M + H]+; calcd. for [C18H22N2O4 + H]+: 331.1658.
Ligand (2): a solution of S2 (493 mg, 1.31 mmol) and S3 (922 mg, 2.79 mmol) in 40 mL of a
1:1 v/v mixture of DCM and CF3COOH was stirred at r.t overnight. The solvent was then
evaporated under reduced pressure and the residue was co-evaporated with 5 x 20 mL of
toluene. The resulting powder was suspended in 5 mL DCM, filtered, washed with Et2O and
dried under vacuum to afford 2 (956 mg, 92%) as an off-white powder. 1H NMR (400 MHz,
3
3
d4-MeOD): δ = 4.08 (s, 2H, CH2), 6.33 (d, 1H, J = 6.9 Hz, Ar-H), 7.00 (d, 1H, J = 6.8Hz,
Ar-H); 13C NMR (100 MHz, d4-MeOD): δ = 37.2 (CH2), 107.2 (CH), 115.6 (Cq), 118.0 (Cq),
19
121.8 (Cq), 123.6 (CH), 145.9 (Cq), 158.3 (Cq); F NMR (376 MHz, d4-MeOD): δ = -77.0
(CF3); HRMS (ESI+): m/z = 141.0661 [M]+; calcd. for [C6H9N2O2]+: 141.0664.
S2

2. Crystallographic data for compounds 4·CsCl and 4·(LiCl)2.
Complex
4∙CsCl∙(CHCl3)3
C99H108Cl9CsN9O12Ru6
2674.32
4∙(LiCl)2
Empirical formula
Formula weight
C96H105Cl2Li2N9O12Ru6
2268.09
Temperature [K]
100(2)
100(2)
Wavelength [Å]
0.71073
0.71073
Crystal system
Monoclinic
C2/c
Monoclinic
C2/c
Space group
a [Å]
32.273(9)
21.362(3)
36.5880(18)
90
18.7149(10) Å
23.060(3) Å
26.181(4) Å
90
b [Å]
c [Å]
a [°]
b [°]
90.267(17)
90
108.343(9)
90
g [°]
Volume [Å3]
25224(8)
8
10725(2)
4
Z
Density (calculated) [g/cm3]
Absorption coefficient [mm‐1]
F(000)
1.408
1.405
1.227
0.93
10664
4576
Crystal size [mm3]
Theta range for data collection
Index ranges
0.56 x 0.37 x 0.34
3.01 to 25.00°.
‐38 ≤ h ≤ 38
0 ≤ k ≤ 25
0 ≤ l ≤ 43
21558
0.48 x 0.33 x 0.17
3.03 to 25.00°.
‐21 ≤ h ≤ 22
‐27 ≤ k ≤ 27
‐31 ≤ k ≤ 31
55785
Reflections collected
Independent reflections (Rint)
21558 (0.0000)
9335 (0.0500)
98.6%
Completeness to theta = 25.00° 97.1%
Absorption correction
Semi‐empirical from
equivalents
Semi‐empirical from
equivalents
Max./min. transmission
Refinement method
0.7452 / 0.6278
0.7452 / 0.4902
Full‐matrix least‐squares on
Full‐matrix least‐squares on
F2
F2
Data / restraints / parameters
Goodness‐of‐fit on F2
21558 / 840 / 1236
1.045
9335 / 276 / 574
1.069
Final R indices [I>2s(I)] R1, wR2
R indices (all data) R1, wR2
Largest diff. Peak/hole [e Å‐3]
0.1057, 0.2813
0.1335, 0.3002
1.945/‐2.139
0.0835, 0.2215
0.1041, 0.2365
1.890/‐1.245
S3

2.1H and 13C NMR spectra of 3 and 4
Figure S1: 1H (top panel, 600 MHz) and 13C (bottom panel, 150 MHz) NMR spectra of dimer 3 in CDCl3.
S4

Figure S2: 1H (top panel, 600 MHz) and 13C (bottom panel, 150 MHz) NMR spectra of cage 4 in CDCl3.
S5

3. High-resolution ESI+-MS spectra of 3 and 4
375.0656
100
749.1234
748.1239
374.5659
374.0657
747.1235
746.1240
373.5659
376.0658
751.1237
373.0661
372.0665
745.1245
743.1252
742.1262
376.5671
377.0663
752.1263
753.1248
371.5670
0
375.0357
100
374.0498
377.0510
373.0495
372.0505
369.0693
749.1486
747.1533
745.1606
751.1579
378.0884
0
300
m/z
1000
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
800
820
840
860
880
900
920
940
960
980
Figure S3: high-resolution (ESI+) mass spectrum (top panel: calculated isotopic distribution of charged series, bottom panel:
experimental data) of 3 in MeOH.
S6

547.0634
547.3134
729.0819
729.4152
1093.1189
1093.6189
100
546.5634
728.4153
1092.1190
547.5634
729.7485
1094.1189
546.3134
728.0820
1091.6190
547.8134
730.0819
1094.6190
546.0635
545.8135
727.7487
727.4155
727.0822
1091.1191
1090.6193
1090.1194
548.0634
548.3135
730.4153
1095.1190
1095.6191
730.7487
731.0822
545.5636
545.3137
726.7490
726.4157
1089.6195
1089.1196
548.5635
548.8137
1096.1193
1096.6194
545.0637
544.8138
1097.1196
1097.6199
544.5639
544.3140
0
728.7939
100
728.4858 729.1460
727.8039
729.4761
729.8064
727.4742
727.1554
730.1588
726.8038
730.4782
726.5071
730.8197
726.1337
725.7933
731.1172
725.4968
731.4699
725.1565
546.8678
744.1454
0
m/z
1180
480
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
800
820
840
860
880
900
920
940
960
980
1000
1020
1040
1060
1080
1100
1120
1140
1160
Figure S4: high-resolution (ESI+) mass spectrum (top panel: calculated isotopic distribution of charged series, bottom panel:
experimental data) of 4 in MeOH. Minor peaks correspond to singly hydrolysed product, MeOH adduct or K+ adduct.
S7

4. Supplementary 1H NMR data
1
Figure S5: H NMR of a 1 mM solution of 4 in CD3OD with 10 eq. of RbCl (top); 1 eq of LiCl and X eq of RbCl, major
products are Rb+@LiCl·4, LiCl·4 and CD3OD@LiCl·4, minor products are Rb+@4, (LiCl)2·4 and CD3OD@(LiCl)2·4
(middle); 1eq of LiCl (bottom).
S8

5. UV-VIS titrations
0.10
0.08
0.06
0.04
0.02
0.00
2.0x10-5
4.0x10-5
0.0
[CsO2CCF3] (M)
Figure S6: UV-VIS titration data (black) and calculated binding isotherm (red) of cage 4 in MeOH.
0.04
0.03
0.02
0.01
0.00
0.0
1.0x10-5
2.0x10-5
3.0x10-5
[CsO2CCF3] (M)
Figure S7: UV-VIS titration data (black) and calculated binding isotherm (red) of cage 4 in MeOH in the presence of 2.2 eq.
of LiCl.
S9

0.10
0.08
0.06
0.04
0.02
0.00
without LiCL
with LiCL
1.0x10-5
2.0x10-5
3.0x10-5
4.0x10-5
0.0
[CsCF3COOH] (M)
Figure S8: UV-VIS titration data of cage 4 in MeOH without (red circles) and with (black squares) 2.2 eq of LiCL.
S10