1 For a general review, see: (a) V. Balzani, A. Credi and M. Venturi,
Molecular Devices and Machines, Wiley-VCH, Weinheim, 2003; (b)
A. Mateo-Alonso, G. Fioravanti, M. Marcaccio, F. Paolucci,
G. M. A. Rahman, C. Ehli, D. M. Guldi and M. Prato, Chem.
Commun., 2007, 1945; (c) D. S. Marlin, D. G. Cabrera, D. A. Leigh and
A. M. Z. Slawin, Angew. Chem., Int. Ed., 2006, 45, 1385; (d)
H. Murakami, A. Kawabuchi, R. Matsumoto, T. Ido and
N. Nakashima, J. Am. Chem. Soc., 2005, 127, 15891; (e) G. Bottari,
F. Dehez, D. A. Leigh, P. J. Nash, E. M. Perez, J. K. Y. Wong and
F. Zerbetto, Angew. Chem., Int. Ed., 2004, 42, 5886; (f) G. Bottari,
D. A. Leigh and E. M. Perez, J. Am. Chem. Soc., 2003, 125, 13360; (g)
for the original report of a molecular shuttle, see: P. L. Anelli, N. Spencer
and J. F. Stoddart, J. Am. Chem. Soc., 1991, 113, 5131.
2 (a) A. Mateo-Alonso, C. Ehli, G. M. A. Rahman, D. M. Guldi,
G. Fioravanti, M. Marcaccio, F. Paolucci and M. Prato, Angew. Chem.,
Int. Ed., 2007, 46, 3521; (b) A. B. Braunschweig, W. R. Dichtel,
O. S. Miljanic, M. A. Olson, J. M. Spruell, S. I. Khan, J. R. Heath and
J. F. Stoddart, Chem.–Asian J., 2007, 2, 634; (c) V. Balzani,
M. Clemente-Leon, A. Credi, M. Semeraro, M. Venturi, H.-R. Tseng,
S. Wenger, S. Saha and J. F. Stoddart, Aust. J. Chem., 2006, 59, 193; (d)
K. Noergaard, B. W. Laursen, S. Nygaard, K. Kjaer, H.-R. Tseng,
A. H. Flood, J. F. Stoddart and T. Bjoernholm, Angew. Chem., Int. Ed.,
2005, 44, 7035; (e) A. Altieri, G. Bottari, F. Dehez, D. A. Leigh,
J. K. Y. Wong and F. Zerbetto, Angew. Chem., Int. Ed., 2003, 42, 2296;
(f) for an example containing a 1,2-bis(pyridinium) recognition site, see:
A. M. Elizarov, S. H. Chiu and J. F. Stoddart, J. Org. Chem., 2002, 67,
9175.
Fig. 4 Fluorescence emission spectra for 52+ and H-53+ in CH2Cl2
solution at a concentration of 2.0 6 1023 M. Excitation wavelength =
250 nm, * denotes an artefact of the instrumentation which occurs at
double the excitation wavelength; 500 nm.
With the elimination of the ICT absorption band, three absorption
maxima of the anthracene fragment become apparent at 389, 368
and 348 nm. Fig. 4 shows the emission spectra of 52+ and H-53+ in
CH2Cl2. The spectrum of 52+ is complicated but definitely shows
stunted emission, probably due primarily to quenching of
fluorescence by the lone pair of electrons on the aniline nitrogen.11
Protonation partially restores normal anthracene fluorescence as
3 (a) E. M. Perez, D. T. F. Dryden, D. A. Leigh, G. Teobaldi and
F. Zerbetto, J. Am. Chem. Soc., 2004, 126, 12210; (b) D. H. Qu,
G. C. Wang, J. Ren and H. Tian, Org. Lett., 2004, 6, 2085; (c)
Q. C. Wang, D. H. Qu, J. Ren, K. C. Chen and H. Tian, Angew. Chem.,
´
Int. Ed., 2004, 43, 2661; (d) D. A. Leigh, M. A. F. Morales, E. M. Pe´rez,
J. K. Y. Wong, C. G. Saiz, A. M. Z. Slawin, A. J. Carmichael,
D. M. Haddleton, A. M. Brouwer, W. J. Burma, G. W. H. Wurpel,
S. Leo´n and F. Zerbetto, Angew. Chem., Int. Ed., 2005, 44, 3062.
4 S. J. Loeb, J. Tiburcio and S. J. Vella, Org. Lett., 2005, 7, 4923.
5 (a) S. J. Loeb and J. A. Wisner, Angew. Chem., Int. Ed., 1998, 37, 2838;
(b) S. J. Loeb and J. A. Wisner, Chem. Commun., 1998, 2757; (c)
S. J. Loeb and J. A. Wisner, Chem. Commun., 2000, 845; (d)
A. L. Hubbard, G. J. E. Davidson, R. H. Patel, J. A. Wisner and
S. J. Loeb, Chem. Commun., 2004, 138; (e) S. J. Loeb and J. A. Wisner,
Chem. Commun., 2000, 1939; (f) S. J. Loeb and D. A. Tramontozzi,
Org. Biomol. Chem., 2005, 3, 1393.
6 S. J. Vella, J. Tiburcio and S. J. Loeb, Org. Lett., 2006, 8, 3421.
7 This is a known compound which is also commercially available.
8 (a) G. J. E. Davidson, S. J. Loeb, N. A. Parekh and J. A. Wisner,
J. Chem. Soc., Dalton Trans., 2001, 3135; (b) S. J. Loeb, J. Tiburcio and
S. J. Vella, Chem. Commun., 2006, 1598.
seen in the spectrum of H-53+
.
Molecular shuttles combining 1,2-bis(pyridinium)ethane and
benzylanilinium recognition sites and utilising DB24C8 as the
mobile fragment have been described. The system incorporates a
4-pyridinium aniline chromophore unit, and is modular enough to
allow easy incorporation of bulky stoppers that may also possess
1
useful spectroscopic handles. While H NMR spectroscopy was
ultimately used to elucidate the position of the crown ether on the
axle, the protonation/deprotonation steps used to drive switching
could be sensed optically by a measurable change in colour or
fluorescence intensity and thus provide indirect evidence of
molecular shuttling.
9 For examples of the C-conformation for DB24C8 with this recognition
motif see ref. 4, and D. J. Hoffart and S. J. Loeb, Angew. Chem., Int.
Ed., 2005, 44, 901.
10 S. J. Loeb, J. Tiburcio, S. J. Vella and J. A. Wisner, Org. Biomol. Chem.,
2006, 4, 667.
Notes and references
11 (a) A. P. de Silva, Chem. Rev., 1997, 97, 1515, and references therein; (b)
P. R. Ashton, R. Ballardini, V. Balzani, I. Baxter, A. Credi, M. C. T.
Fyfe, M. T. Gandolfi, M. Gomez-Lopez, M.-V. Martinez-Diaz,
A. Piersanti, N. Spencer, J. F. Stoddart, M. Venturi, A. J. P. White
and D. J. Williams, J. Am. Chem. Soc., 1998, 120, 11932; (c) F. Han,
Y. Bao, Z. Yang, T. M. Fyles, J. Zhao, X. Peng, J. Fan, Y. Wu and
S. Sun, Chem.–Eur. J., 2007, 13, 2880; (d) Y. Shiraishi, Y. Tokitoh,
G. Nishimura and T. Hirai, Org. Lett., 2005, 7, 2611; (e) V. Amendola,
L. Fabbrizzi, C. Mangano, P. Pallavicini, A. Perotti and A. Taglietti,
J. Chem. Soc., Dalton Trans., 2000, 185; (f) K. Ghosh and G. Masanta,
Chem. Lett., 2006, 35, 414.
{ X-Ray crystal data were collected on a Bru¨ker APEX CCD
diffractometer following standard procedures.12,13 The crystals were of
poor quality which is reflected in the quality of the data as represented by
Rint. However, the solution was straightforward and the metric parameters
chemically reasonable. One of the triflate anions was poorly defined and
restrained to have the same geometry as the well defined one. Summary of
crystal data for [3][OTf]2?2H2O: C55H65F12N3O16S2, M = 1316.22, T =
173(2) K, monoclinic, space group P21/c, a = 23.985(10), b = 15.436(6),
3
c = 17.782(7) A, b = 102.815(8)u, V = 6420(4) A , Dc = 1.362 g cm23, m =
0.183 mm21, Z = 4, reflections collected = 33416 (Rint = 0.1162), final R
indices [I . 2s(I)]: R1 = 0.1189, wR2 = 0.3152, R indices (all data): R1 =
0.2993. wR2 = 0.4122, GoF = 0.976 with data/variables/restraints = 11273/
784/31. CCDC 656476. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/b710708k
˚
˚
12 G. M. Sheldrick, SHELXTL 5.03 Program Library, Bru¨ker Analytical
Instrument Division, Madison, WI, USA.
13 DIAMOND 3.1 - Visual Crystal Structure Information System
CRYSTAL IMPACT, Postfach 1251, D-53002 Bonn, 2006.
4754 | Chem. Commun., 2007, 4752–4754
This journal is ß The Royal Society of Chemistry 2007