Supporting Information

© Wiley-VCH 2008

69451 Weinheim, Germany

1

A Self-Assembled Spin Cage

Koji Nakabayashi, Yusuke Ozaki, Masaki Kawano, Makoto Fujita*

Supporting Information (15 pages)

1. Synthesis of radical ligand 1.

2. CSI-MS spectrum of 2 (PF6 salt), Figure S1.

3. ESR spectra of 2 in several microwave powers at 293 K, Figure S2

4. Titration experiment of radical ligand 1 to (bpy)Pd(NO3)2, Figure S3.

5. ESR spectra of 2 in several concentrations and temperatures, Figure S4, S5.

6. The T-T plot of 2 and 2·3, Figure S6.

7. Extraction experiments of 2·3 and 2·(4)2 complex.

8. Thermal ellipsoid plots of the radical cage of 2, Figure S7.

9. Molecular models of 2·3, Figure S8.

10. Enclathration experiment of neutral molecules, Table S1.

11. Synthesis of radical guests 3.

12. Instrumentation and materials.

___________________________________

[*] K. Nakabayashi, Yusuke Ozaki, Dr. M. Kawano, and Prof. Dr. M. Fujita

Department of Applied Chemistry, School of Engineering,

The University of Tokyo,

and CREST, Japan Science and Technology Agency (JST),

7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

FAX: +81-3-5841-7257

E-mail: mfujita@appchem.t.u-tokyo.ac.jp

2

N

NN N

N

N NH

N

OH

O

OH

N NH2 , NaNO2

NaOH

, HCl

1. Preparation of radical ligand 1.

3-(4-Pyridyl)-2-oxopropionic acid was prepared as described in the literature. P.

Busca, F. Paradisi, E. Moynihan, A. R. Maguire, P. C. Engle, Org. Biomol. Chem.

2004, 2, 2684-2691.

Sodium nitrite (8.28 g, 120 mmol) was dissolved in 22.5 ml water and cooled to

about – 5 °C. This solution was added to the solution of 4-Aminopyridine (11.30 g,

120 mmol) in Hydrochloric acid (35.5 w%, 120 ml) at - 15 °C, resulting in the

diazonium salt of 4-Aminopyridine. The solution of diazonium salt was slowly

added dropwize to the solution of 3-(4-Pyridyl)-2-oxopropionic acid (2.45 g, 14.95

mmol) dissolved in 4 M Sodium hydroxide (33 ml) at - 15 °C. The reactive solution

was stirred at - 15 °C for 10 hours, turned to a sticky reddish-brown solution. The

sticky solution was extracted by Chloroform, and the organic phase was dried over

anhydrous Na2SO4, evaporated in vacuo. The crude product was purified by

column chromatography on silica gel (from CHCl3 to CHCl3: MeOH = 20 : 1) to give

1,3,5-tris-(4-pyridyl)-formazan as a reddish-brown solid (1.37g, 4.52 mmol) in 30%

yield: 1H NMR (500 MHz, CDCl3) (ppm) = 7.57 (dd, J1 = 5.0 Hz, J2 = 1.5 Hz, 4H),

7.99 (dd, J1 = 4.5 Hz, J2 = 2 Hz, 2H), 8.74 (dd, J1 = 4.5 Hz, J2 = 2 Hz, 2H), 8.76 (dd,

J1 = 5.0 Hz, J2 = 1.5 Hz, 4H). ESI-MS m/z: 304.13 [M + H]+. Elemental Anal.

Calcd for C16H13N7: C, 63.33; H, 4.43; N, 32.49. Found: C, 63.36; H, 4.32; N, 32.32.

3

N

NN N

N

N NH

N

NN N

N

N N

1. KHSO4, (CH2O)n

2. NaOH, O2

DMF

1,3,5-tri-(4-pyridyl)-formazan(195.5 mg, 0.654 mmol), Paraformaldehyde(2.57 g)

and Potassium hydrogen sulfate(1.40 g, 10.3 mmol) were stirred for 6 h in 60 ml

DMF at r. t. The reactive solution was diluted with 300 ml distilled water, and then,

Sodium hydroxide (4 mol/L, 6 mL) was added slowly dropwise to it, stirred for 24 h at

r. t. with air bubbling. The resultant green solid was filtered, washed with distilled

water and Acetone and dried up in vacuo. The crude solid was purified by

recrystalization in CHCl3-MeOH solution to give 1, 3, 5- tri - (4-pyridyl) – verdazyl as

a green solid (131.2mg, 0.415mmol) in 64% yield: ESI-MS m/z: 316.1 [M-].

Elemental Anal. Calcd for C17H14N7: C, 64.55; H, 4.46; N, 30.99. Found: C, 64.31; H,

4.65; N, 30.71. UV – vis (CHCl3). max (nm): 404 ( = 7.8 103), 424 ( = 7.7 103),

682 ( = 3.8 103). m. p. = 261-262°C (decomposed temperature = 175-176.5°C)

ESR: g = 2.003, aN = 0.56 mT.

4

4+

5+

6+

7+

m/z found calculated

4+ 509.529 509.313

5+ 618.287 618.359

6+ 771.100 771.023

7+ 1000.085 1000.020

2. CSI–MS spectrum of spin cage 2, Figure S1.

The counter anion of spin cage was exchanged from NO3- to PF6

-. An excess of

NaPF6 was added to the H2O solution of the cage with NO3-, stirred for 2 h at r. t. and

the precipitate was filtered to give the radical cage 2 with PF6- quantitatively.

Figure S1 CSI-MS spectrum of 2 with PF6-.

5

3. ESR spectra of 2 in several microwave powers at 293 K, Figure S2.

We examined power dependence of an ESR spectrum of M6L4 spin cage 2 in H2O

to confirm that radical species existing in the solution is only spin cage 2. The

shape of the broad signal should change or distort depending on microwave powers

if some kinds of radical species are contain in the solution. However, the signal

profiles in respective powers were identical (Figure S2), suggesting that the

complexation of 2 was progressed quantitatively. This quantitative complexation of

2 was also supported by titration experiments, temperature dependence and

concentration dependence, Figure S3, S4 and S5 respectively.

Figure S2. ESR spectra of 2 mM spin cage 2 in respective powers at 293 K.

50 mW

16 mW

4 mW

1 mW

0.1 mW

0.01 mW

6

4. Titration experiment of radical ligand 1 to (bpy)Pd(NO3)2, Figure S3.

Composition of M6L4 radical cage was also confirmed by titration of the ligand to

palladium. A (bpy)Pd(NO3)2 and radical ligand 1 in 6:3, 6:4 and 6:5 ratio were

mixed in H2O, after filtration of surplus ligand, the ESR spectra of the respective

solutions were measured. Intensity of the ESR signal was saturated just when ratio

of the ligand to palladium is 4 to 6.

Figure S3. ESR spectra of 2 in the respective ratio of the ligand to (bpy)Pd(NO3)2 at 293

K.

6 : 5

6 : 4

6 : 3

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5. ESR spectra of 2 in several temperatures and concentrations.

While the radical ligand 1 shows split signals to nine due to four nitrogen nuclei,

the spin cage 2 shows a broad ESR signal. In general, line broadening stems

from motional broadening and electron-spin exchange. If the cause is motional

broadenig, the broad signal should gradually become the nine split signals similar

to a ligand according to heating. However, the configuration of ESR spectra in

spin cage 2 is identical (not split) even at 90°C (Figure S4). Thus, this broadening

is owing to dipolar interaction and/or relatively strong exchange interaction

compared to the hyperfine interaction (aN = 0.56 mT). Although these

interactions are derived from inter- or intramolecular interaction, in the case of spin

cage 2 intermolecular interaction is neglected because the ESR spectrum of 2 has

a broad signal even in low concentration of 2, 0.04 mM (Figure S5).

Figure S4. ESR spectra of 0.2 mM 2 at 30, 60 and 90 °C in H2O.

90 °C

60 °C

30 °C

8

1 mM

0.2 mM

0.04 mM

Figure S5. ESR spectra of 2 in respective concentrations at 295 K in H2O.

9

6. The T-T and -T plots of 2 and 2·3, Figure S6.

Spin cage 2 and clathrate complex 2·3 showed paramagnetic behavior (Figure

S6a and b). The numerical fit to Curie-Weiss law for -T plots of 2 and 2·3 gave

Weiss constant, -0.1 K and -0.4 K respectively. In T-T plot, the T value of 2·3 is

about 0.4 more than that of 2, supporting 1:1 host-guest complex because the value

of 0.4 corresponds a value of one molar free spins, 0.375. Clathrate complex

showed a steeper decrease of T value in a low temperature region than spin cage

2. This result indicates that the close proximity of spin centers between the host

and the guest in the cavity induces an effective spin-spin interaction.

Figure S6. The -T plot of (a) 2 and (b) 2·3. (c) T-T plots of 2 and 2·3.

(a) spin cage 2 (b) clathrate complex 2·3

2·3

2

~ 0.4

10

7. Extraction experiments of 2·3 and 2·(4)2 complex.

An excess of powdered nitrosyl radical 4 was suspended in an aqueous solution

of 2 (1 ml) at 20 °C for 1 h to give, after filtration of surplus radical guest, clathrate

compound 2·(4)2. The 1:2 host-guest stoichiometry was confirmed by the

extraction of the guest with chloroform. The 400 l resultant solution was

extracted with 400 l CHCl3. The quantity of 4 in the organic phase was

estimated by UV-vis spectrum. The host-guest stoichiometry of 2·3 was also

confirmed in same manner.

8. Thermal ellipsoid plots of the radical cage of 2, Figure S8.

Figure S7. Thermal ellipsoid plots (30 % probability level) of the molecular structure

of 2. All independent atoms including water and nitrate ions with labels. Hydrogen

atoms are omitted for clarity.

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9. Molecular model of 2·3, Figure S9.

Figure S8. Molecular model of 2·3. The geometry of guest 3 was optimized using a

force-field calculation on Materials Studio 4.2. The coordinates of spin cage 2 are

derived from the crystallographic data. Spin centers of 2 and 3 are colored by blue.

12

10. Enclathration experiment of neutral molecules.

The excess amount of adamantane (about 50 equivalent to the cage 2) was

suspended in 0.85 mM radical cage solution (1 ml) and stirred for 1h at 20 °C or 80

°C. The residual adamantane was filtered off, and the 200 μl resultant solution was

extracted with 400 μl CHCl3. Presence of guests in the extracted solution was

confirmed by a GC-MS spectrum. The eclathration experiments about other guests

listed below were tried in same manner. Using (bpy)Pd(NO3)2 solution (5.1 mM),

the control experiment also was tried in same manner.

In the conclusion, guests A and D-G were enclathrated in hydrophobic cavity of

spin cage 2.

Notice that all guest molecules are insoluble or less soluble in water.

Guest molecules 80 °C 20 °C Control

A Adamantane 26.6 23.0 0

B Norbornane 0 0 0

C 2- Norbornene 0 0 0

D Naphthalene 5.8 4.6 1.4

E Phenanthrene 6.2 6.3 0

F Octafluoronaphthalene 1.7 1.6 0

G 2,3,5,6- Tetramethyl -1,6-

benzoquione

18.0 15.6 2.5

TIC/104

Table S1. Total ion chromatogram (TIC) values of respective guests detected by a

GC-MS instrument.

13

11. Synthesis of radical guests 3.

9-Phenanthrenecarboxaldehyde (41 mg, 0.2 mmol) in diethyl ether (2.5 ml) was

added drop wise to a solution of 2,3-diamino-2,3-dimethylbutane (31 mg, 0.26

mmol) in diethyl ether (2 ml). Condensation was complete in 9 hours on refluxing.

The crude solid of 3a was obtained in about 80 % yield after evaporation. Although

the crude contained a little impurity, we used it in next step without any purification.

1H NMR (500 MHz, CDCl3) (ppm) = 1.15 (s, 6H), 1.31 (s, 6H), 5.81 (s, 1H)

7.57-7.66 (m, 4H), 7.94 (d, J = 8.0 Hz, 1H), 8.39 (s, 1H), 8.53 (m, 1H), 8.65 (d, J =

8.0 Hz, 1H), 8.71 (m, 1H). MALDI TOF-MS m/z: 305.1 [M + H]+.

A solution of m-chloroperbenzoic acid (44 mg, 0.25 mmol) in CH2Cl2 (0.5 ml) was

added dropwise to a mixture of 3a (31 mg, ~ 0.1 mmol) in CH2Cl2 (1 ml) and

saturated NaHCO3 (0.6 ml) in an ice bath. Stirring was continued for 1 h, and a

solution of NaIO4 (32 mg, 0.15 mmol) in water (0.5 ml) was added dropwise.

Appearance of the nitronyl nitroxide was followed by TLC (SiO2, ethylacetate:hexane

= 1:1). Drying (Na2SO4), evaporation of the organic phase, and chromatography

(SiO2, ethylacetate:hexane = 1:1) led to pure 3 in 67% yield (22.4 mg, 0.067 mmol).

Elemental Anal. Calcd for C16H13N7: C, 75.65; H, 6.35; N, 8.40. Found: C, 75.75; H,

6.54; N, 8.36. ESR: g = 2.006, aN = 0.76 mT.

N+

N

-O

O

3

N

N

H

H

3a

CHOH2N NH2

1. MCPBA2. NaIO4

14

12. Instrumentation and materials.

All ESR spectra were recoded on a JEOL JES-RE1X spectrometer. Modulation

frequency is 100 kHz. ESR spectra in solution were measured using a LABOTEC

capillary tube. The magnetic susceptibility measured by SQUID (MPMS-5S,

Quantum Design). UV-vis spectra were recorded on a SHIMADZU UV-3150.

Solvents and reagents were purchased from TCI Co., Ltd., WAKO Pure Chemical

Industries Ltd., and Aldrich Chemical, Ltd.