J. Am. Chem. Soc. 1997, 119, 8363-8364
8363
Synthesis and Cation-Mediated Electronic
Interactions of Two Novel Classes of
Scheme 1
Porphyrin-Fullerene Hybrids
†
Phil S. Baran, Regina R. Monaco, Ahsan U. Khan,
David I. Schuster,* and Stephen R. Wilson*
Department of Chemistry, New York UniVersity
Scheme 2. Synthesis of Hybrids 5-7a
New York, New York 10003
ReceiVed February 14, 1997
The unique photophysical properties of C60 have generated
significant research focused on its use as the acceptor in
covalently bound donor-acceptor pairs.1 In particular, photo-
physical properties of porphyrin-linked C60 hybrids have
received considerable attention.2 It has been shown that
intramolecular electron transfer from the porphyrin to C60 to
generate ion pairs occurs extremely rapidly with zinc porphyrins
and with free base dyads in polar solvents; in nonpolar solvents,
3
2a,g,3
efficient formation of C60* was seen.
The extent of such
interactions in the ground state has been attributed to the rigid
conformation enforced by the linker.2
,3
Herein we report the efficient synthesis as well as compu-
tational and photophysical studies of two novel classes of
porphyrin-C60 hybrids. These hybrids (i.e., dyads) are unique
in that (i) their synthesis utilizes a convergent strategy, providing
access to a rich array of new structures, including the first aza-
linked porphyrin-fullerene hybrid, (ii) despite the fact that the
porphyrin moiety is not rigidly connected to C60, electronic
interactions still occur in the ground state, and (iii) cations induce
formation of a complex with open-chain crown-ether mimics 6
and 8 in which there is a dynamic equilibrium between
complexed and uncomplexed states (see Scheme 1). In the
former state, the two chromophores are brought closer together,
significantly increasing intramolecular interactions.
a
Reagents and conditions: (a) 3 equiv of monosilyl-protected glycol,
equiv of DCC, 0.2 equiv of DMAP, 1.1 equiv of BtOH, PhBr:DMSO
3
(
5:1), 50°, 12 h 50-70%. (b) 5% oxalic acid:MeOH, 5 min. (c) CH
2 2
Cl :
-4
0.1 N HCl/EtOH:CS :H O (5:1:0.25:10 ), 1 h (TBDMS)-8 h (TIPS),
2
2
2 2
95%. (d) 1 equiv of EDC, 1 equiv of DMAP, CH Cl , 12 h, 48-70%.
Scheme 3. Second-Generation Hybrid Synthesisa
Armed with a facile high-yield route to carboxylic acid 1
4
via sulfonium ylide addition and subsequent hydrolysis,
fullerenes possessing linkers with terminal hydroxyl groups were
synthesized through a protection-deprotection sequence by
5
coupling of monoprotected diols with 1, followed by EDC-
6,7
mediated coupling with 5-(4′-carboxyphenyl)-10,15,20-triph-
enylporphine (3, Scheme 2).7 Flexibility in the choice of the
,8
†
Current address: The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, CA 92037.
(1) (a) Khan, S. I.; Oliver, A. M.; Paddon-Row, M. N.; Rubin, Y. J.
Am. Chem. Soc. 1993, 115, 4919. (b) Rasinkangas, M.; Pakkanen, T. T.;
Pakkanen, T. A. J. Organomet. Chem. 1994, 476, C6. (c) Imahori, H.;
Cardoso, S.; Tatman, D.; Lin, S.; Noss, L.; Seely, G. R.; Sereno, L.; de
Silber, J. C.; Moore, T. A.; Moore, A. L.; Gust, D. Photochem. Photobiol.
a
Reagents and conditions: (a) 1 equiv of SOCl
, DMSO, 60 °C, 20 h. (c) C60, chlorobenzene, reflux 24 h
53% based on unrecovered C60). (d) EDC (1.1 equiv), DMAP (1.1
2
, toluene, reflux 2
h. (b) NaN
3
(
1
995, 62, 1009. (d) Sariciftci, N. S.; Wudl, F.; Heeger, A. J.; Maggini,
M.;Scorrano, G.; Prato, M.; Bourassa, J.; Ford, P. C. Chem. Phys. Lett.
995, 247, 510. (e) Linssen, T. G.; Durr, K.; Hanack, M.; Hirsch, A. J.
equiv), 24 h (63%).
1
diol renders this approach extremely useful in the elaboration
of porphyrin-C60 hybrids in which the topographical relation-
ship of the two chromophores can be varied and controlled.
A second-generation approach (Scheme 3) was undertaken
to ascertain the effect of an aza-fullerene linkage ([6,5] open)
on photophysics and cation complexation (Vide infra). Monochlo-
rination of the diol linker followed by NaN3 displacement
furnished the azide which afforded the desired fullerene syn-
Chem. Soc., Chem. Commun. 1995, 103. (f) Diederich, F.; Dietrich-
Buchecker, C.; Nierengarten, J.-F.; Sauvage, J.-P. J. Chem. Soc., Chem.
Commun. 1995, 781. (g) Maggini, M.; Dono, A.; Scorrano, G.; Prato, M.
J. Chem. Soc., Chem. Commun. 1995, 845. (h) Williams, R. M.; Zwier, J.
M.;Verhoeven, J. W. J. Am. Chem. Soc. 1995, 117, 4093. (i) Armspach,
D.; Constable, E. C.; Diederich, F.; Housecroft, C. E.; Nierengarten, J.-F.
J. Chem. Soc., Chem. Commun. 1996, 2009.
(2) (a) Liddell, P. A.; Sumida, J. P.; Macpherson, A. N.; Noss, L.; Seely,
G. R.; Clark, K. N.; Moore, A. L.; Moore, T. A.; Gust, D. Photochem.
Photobiol. 1994, 60, 537. (b) Imahori, H; Hagiwara, K.; Akiyama, T.;
Taniguchi, S.; Okada, T.; Sakata, Y. Chem. Lett. 1995, 265. (c) Drovetskaya,
T.; Reed, C. A.; Boyd, P. Tetrahedron Lett. 1995, 36, 7971. (d) Imahori,
H.; Sakata, Y. Chem. Lett. 1996, 199. (e) Ranasinghe, M. G.; Oliver, A.
M.; Rothenfluh, D. F.; Salek, A.; Paddon-Row: M. N. Tetrahedron Lett.
9
thon. EDC-mediated coupling with 3 afforded hybrid 8.
UV-vis studies of hybrids 5-7 and their metalated deriva-
tives reveal considerable ground state interactions between the
two chromophores. Bathochromic shifts of 6-10 nm are
1
996, 27, 4797. (f) Akiyama, T.; Imahori, H.; Ajawakom, A.; Sakata, Y.
Chem. Lett. 1996, 907. (g) Imahori, H.; Hagiwara, K.; Aoki, M.; Akiyama,
T.; Taniguchi, S.; Okada, T.; Shirakawa, M.; Sakata, Y. J. Am. Chem. Soc.
(5) Isaacs, L.; Wehrsig, A.; Diederich, F. HelV. Chim. Acta 1993, 76,
1231. Isaacs, L.; Diederich, F. Ibid. 1993, 76, 2454. Toniolo, C.; Bianco,
A.; Maggini, M.; Scorrano, G.; Prato, M.; Marastoni, M.; Tomatis, R.;
Spisani, S.; Palu, G.; Blair, E. D. J. Med. Chem. 1994, 37, 4558.
(6) Dhaon, M. K.; Olsen, R. K.; Ramasamy, K. J. Org. Chem. 1982, 47,
7, 1962. EDC ) N-(3-(dimethylamino)propyl)-N′-ethylcarbodiimide hy-
drochloride.
1
996, 118 (8), 11771. For a recent report of a related triad, see: Liddell, P.
A.; Kuciauskas, D.; Sumida, J. P.; Nash, B.; Nguyen, D.; Moore, A. L.;
Moore, T. A.; Gust, D. J. Am. Chem. Soc. 1997, 119, 1400.
(3) Kuciauskas, D.; Lin, S.; Seely, G. R.; Moore, A. L.; Moore, T. A.;
Gust, D.; Drovetskaya, T.; Reed, C. A.; Boyd, P. J. Phys. Chem. 1996,
1
00, 15926.
4) Wang, Y.; Cao, J.; Schuster, D. I.; Wilson, S. R. Tetrahedron Lett.
995, 36, 6843.
(
(7) Novkova, S.; Philipova, I.; Blagoev, B.; Matile, S.; Berova, N.;
Nakanishi, K. J. Am. Chem. Soc. 1995, 117, 7021.
1
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