C O M M U N I C A T I O N S
Supporting Information Available: Experimental procedures, NMR
and ESR spectra, and X-ray structural data in CIF format. This material
is available free of charge via the Internet at http://pubs.acs.org.
References
(
1) Catalysis by coordination networks: (a) Wang, Z.; Chen, G.; Ding, K. Chem.
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2, 7353.
(
3) Retinal is an essential polyene chromophore whose 11-cis to all-trans
photoisomerization is responsible for human and animal vision: (a) Unger,
V. M.; Hargrave, P. A.; Baldwin, J. M.; Schertler, G. F. Nature 1997, 389,
203. (b) Palczewski, K.; Kumasaka, T.; Hori, T.; Behnke, C. A.; Motoshima,
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Figure 3. (a) Crystal structure of {[(ZnI
2
)
3
(TPT)
2
n
]·(retinal)1.1 ·(cyclohexane)} .
Retinal A (orange, ∼90% occupancy) is observed as the all-trans isomer,
while retinal B (blue, ∼20% occupancy) is considerably disordered. The
disordered structures have been overlaid except for those drawn in the
space-filling presentation. Cyclohexane has been omitted for clarity. (b)
ORTEP drawing of retinal A. Ellipsoids are set at the 30% probability level.
(
(
4) The photoisomerization of all-trans-retinal to the 13-cis form in bacteri-
orhodopsin drives the proton gradient across biomembranes: (a) Hampp,
N. Chem. ReV. 2000, 100, 1755. (b) Lanyl, J. K. Mol. Membr. Biol. 2004,
hampered when the catalyst crystals were removed by filtration
during the isomerization (Figure S6).
2
1, 143.
1
0,11
5) Binding of retinal by artificial receptors or porous materials: (a) Tabushi,
I.; Kuroda, Y.; Shimokawa, K. J. Am. Chem. Soc. 1979, 101, 4759. (b)
Mu n˜ oz-Botella, S.; Mart ´ı n, M. A.; del Castillo, B.; Lerner, D. A.; Men e´ ndez,
J. C. Anal. Chim. Acta 2002, 468, 161. (c) Kpegba, K.; Murtha, M.; Nesnas,
N. Bioorg. Med. Chem. Lett. 2006, 16, 1523. (d) Liu, R. S. H.; Yang, L.-
Y.; Liu, J. Photochem. Photobiol. 2007, 83, 2. (e) Liu, R. S. H.; Hammond,
G. S. Acc. Chem. Res. 2005, 38, 396.
X-ray crystallographic analysis of the retinal-treated crystals
unequivocally revealed the presence of retinal in the network pores.
Two crystallographically independent retinal molecules (A and B)
were observed in single crystals of 1 (Figure 3). Retinal A exists
as the all-trans form. The molecular structure of retinal falls within
normal parameters (Figure 3b), and no specific van der Waals
contacts with surrounding TPT ligands or Zn(II) ions are observed.
No disorder indicating the presence of the 13-cis isomer was
observed. In contrast, the other retinal, retinal B, is considerably
disordered. The refinement of retinal B into a reasonable structure
was unsuccessful because of many possible conformations, and no
appropriate frameworks without severe distortions were obtained.
Nevertheless, the obtained X-ray crystal structure clearly shows
that retinal molecules do exist in the pores of 1, suggesting that
these pores serve as favorable sites into which retinal molecules
can penetrate.
(6) (a) Biradha, K.; Fujita, M. Angew. Chem., Int. Ed. 2002, 41, 3392. (b)
Ohmori, O.; Kawano, M.; Fujita, M. J. Am. Chem. Soc. 2004, 126, 16292.
(c) Haneda, T.; Kawano, M.; Kojima, T.; Fujita, M. Angew. Chem., Int.
Ed. 2007, 46, 6643.
2
7) ZnI -TPT related complexes: (a) Ohmori, O.; Kawano, M.; Fujita, M.
(
Angew. Chem., Int. Ed. 2005, 44, 1962. (b) Haneda, T.; Kawano, M.;
Kawamichi, T.; Fujita, M. J. Am. Chem. Soc. 2008, 130, 1578. (c)
Kawamichi, T.; Kodama, T.; Kawano, M.; Fujita, M. Angew. Chem., Int.
Ed. 2008, 47, 8030.
(
8) All of the experiments regarding the isomerization of retinal were carried
out in the dark under an Ar atmosphere since retinal is easily
photoisomerized.
(
9) This complex was prepared as a microcrystalline powder by rapid mixing
of ZnI and TPT: Ohara, K.; Mart ´ı -Rujas, J.; Haneda, T.; Kawano, M.;
Hashizume, D.; Izumi, F.; Fujita, M. J. Am. Chem. Soc. 2009, 131, 3860.
2
(
(
10) Simple Lewis acid catalysis by the Zn(II) center in the pore is plausible
since homogeneous ZnI (pyridine) catalyst also promoted the isomerization.
2
4
2
For acid- or I -catalyzed isomerization of retinal, see: (a) Sperling, W.;
Carl, P.; Rafferty, C. N.; Dencher, N. A. Biophys. Struct. Mech. 1977, 3,
In summary, we have found that catalytic thermal isomerization
of an olefin proceeded within an artificial porous coordination
network. We note that the present results clearly demonstrate that
the catalysis proceeded inside the pore, in contrast to previous
reports in which it could not be clearly determined whether the
7
9. (b) Hubbard, R. J. Biol. Chem. 1966, 241, 1814. (c) Groenendijk,
G. W. T.; Jacobs, C. W. M.; Bonting, S. L.; Daemen, F. J. M. Eur.
J. Biochem. 1980, 106, 119.
11) ESR analysis showed the presence of radical species in the retinal-containing
crystals, whereas the empty crystals (containing only nitrobenzene) were
ESR-silent (Figure S2). Since we have previously observed charge/electron
transfer from electron-rich guests to electron-deficient Pd(II)-TPT cagelike
2
,13
reaction proceeds on the surface or within the network pores.
1
2
Given the nature of the pores and increased host-guest electronic
interaction, we expect that more organic transformations can potentially
be catalyzed and controlled with high regio- and stereoselectivity within
porous networks.
coordination hosts, isomerization via radical species could also account
for the isomerization. For cis-trans isomerization of polyenes via electron
transfer, see: (a) Polyakov, N.; Leshina, T.; Kispert, L. RIKEN ReV. 2002,
44, 140. (b) Yamabe, T.; Akagi, K.; Ohzeki, K.; Fukui, K.; Shirakawa, H.
J. Phys. Chem. Solids 1982, 43, 577.
(
12) (a) Yoshizawa, M.; Miyagi, S.; Kawano, M.; Ishiguro, K.; Fujita, M. J. Am.
Chem. Soc. 2004, 126, 9172. (b) Furutani, Y.; Kandori, H.; Kawano, M.;
Nakabayashi, K.; Yoshizawa, M.; Fujita, M. J. Am. Chem. Soc. 2009, 131,
4764.
Acknowledgment. This research was supported in part by
KAKENHI (20044006), JSPS, and the Global COE Program,
MEXT, Japan. This work has been approved by the Photon Factory
Program Advisory Committee (Proposal 2008G052).
(
13) Feinstein-Jaffe, I.; Efraty, A. J. Mol. Catal. 1987, 49, 1.
JA908794N
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