1518
Y. Shiraishi et al. / Tetrahedron Letters 52 (2011) 1515–1519
Figure 7. Energy diagrams of the HOMO and LUMO orbitals for 2(MC) and the HOMO-1 and LUMO+1 orbitals for 2–CNꢀ, calculated at the DFT level using a B3LYP/6-31+G⁄
basis set.
3.48 eV, suggesting that 2–CNꢀ has larger transition energy. This is
Acknowledgments
explained by the electronic configuration of respective orbitals. The
p
-electrons of 2(MC) are distributed over the entire molecule. In
This work was supported by Grant-in-Aids for Scientific Re-
search (No. 21760619) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan (MEXT).
contrast,
p
-electrons of 2–CNꢀ are localized on the dinitropheno-
late moiety. This is due to the decrease in electron density of the
indole moiety upon CNꢀ addition. The S0?S1 transition energy
for 2(MC) is 500 nm (2.48 eV, Table S1, Supplementarydata), which
is similar to kmax of the 2(MC) spectrum (523 nm, Fig. 1). In con-
trast, the S0?S4 transition energy for 2–CNꢀ (401 nm, 3.09 eV) is
much lower than that of 2(MC) and is similar to kmax of the 2–
CNꢀ spectrum (396 nm). These closely matched results indicate
Supplementary data
Supplementary data (experimental details, Figures S1–S11, Ta-
ble S1, and Cartesian coordinates for compounds) associated with
this article can be found, in the online version, at doi:10.1016/
that the CNꢀ addition to 2 leads to a localization of the
p-electrons
on the dinitrophenolate moiety, thus resulting in a blue-shift of the
absorption spectrum.
References and notes
The probe 2 reacts with CNꢀ very rapidly; as shown in Figure 3,
the reaction terminates within 1 min. As summarized in Table 1,
1. (a) Koenig, R. Science 2000, 287, 1737–1738; (b) Baud, F. Hum. Exp. Toxicol.
2007, 26, 191–201.
2. Camerino, P. W.; King, T. E. J. Biol. Chem. 1966, 241, 970–979.
3. Guidelines for Drinking-Water Quality; World Health Organization: Geneva,
1996.
kinetic absorption analysis8 reveals that the rate constant (kCN
)
for the reaction of
2
with CNꢀ (30 equiv) in the dark is
6.69 ꢁ 10ꢀ2 sꢀ1 (25 °C). In constant, kCN for the reaction of 1 with
CNꢀ obtained under UV irradiation is 1.83 ꢁ 10ꢀ3 sꢀ1 (25 °C). This
suggests that the nucleophilic CNꢀ addition to 2 occurs much faster
than that to 1.
4. Colorimetric receptors: (a) Lou, X.; Zhang, L.; Qin, J.; Li, Z. Chem. Commun. 2008,
5848–5850; Fluorometric receptors: (b) Kwon, S. K.; Kou, S.; Kim, H. N.; Chen,
X.; Hwang, H.; Nam, S.-W.; Kim, S. H.; Swamy, K. M. K.; Park, S.; Yoon, J.
Tetrahedron Lett. 2008, 49, 4102–4105; (c) Jamkratoke, M.; Ruangpornvisuti, V.;
Tumcharern, G.; Tuntulani, T.; Tomapatanaget, B. J. Org. Chem. 2009, 74, 3919–
3922; (d) Lin, Y.-C.; Chen, C.-T. Org. Lett. 2009, 11, 4858–4861.
5. Colorimetric receptors: (a) García, F.; García, J. M.; García-Acosta, B.; Martínez-
Máñez, R.; Sancenón, F.; Soto, J. Chem. Commun. 2005, 2790–2792; (b) Ros-Lis, J.
V.; Martínez-Máñez, R.; Soto, J. Chem. Commun. 2005, 5260–5262; Fluorometric
receptors: (c) Hudnall, T. W.; Gabbaï, F. P. J. Am. Chem. Soc. 2007, 129, 11978–
11986; (d) Jo, J.; Lee, D. J. Am. Chem. Soc. 2009, 131, 16283–16291.
6. Colorimetric receptors: (a) Tomasulo, M.; Raymo, F. M. Org. Lett. 2005, 7, 4633–
4636; (b) Tomasulo, M.; Sortino, S.; White, A. J. P.; Raymo, F. M. J. Org. Chem.
2006, 71, 744–753; (c) Männel-Croisé, C.; Zelder, F. Inorg. Chem. 2009, 48,
1272–1274; Fluorometric receptors: (d) Sun, Y.; Liu, Y.; Guo, W. Sens. Actuators,
B 2009, 143, 171–176; (e) Sun, Y.; Liu, Y.; Chen, M.; Guo, W. Talanta 2009, 80,
996–1000.
7. (a) Minkin, V. I. Chem. Rev. 2004, 104, 2751–2776; (b) Raymo, F. M.; Tomasulo,
M. Chem. Soc. Rev. 2005, 34, 327–336.
8. Shiraishi, Y.; Adachi, K.; Itoh, M.; Hirai, T. Org. Lett. 2009, 11, 3482–3485.
9. (a) Sunamoto, J.; Iwamoto, K.; Akutagawa, M.; Nagase, M.; Kondo, H. J. Am.
Chem. Soc. 1982, 104, 4904–4907; (b) Shimizu, I.; Kokado, H.; Inoue, E. Bull.
Chem. Soc. Jpn 1969, 42, 1730–1734.
10. (a) Hobley, J.; Malatesta, V.; Millini, R.; Montanari, L.; Parker, W. O. N., Jr. Phys.
Chem. Chem. Phys. 1999, 1, 3259–3267; (b) Hobley, J.; Malatesta, V.; Giroldini,
W.; Stringo, W. Phys. Chem. Chem. Phys. 2000, 2, 53–56; (c) Hobley, J.; Pfeifer-
Fukumura, U.; Bletz, M.; Asahi, T.; Masuhara, H.; Fukumura, H. J. Phys. Chem. A
2002, 106, 2265–2270.
The enhanced CNꢀ addition to 2 is due to the formation of a lar-
ger amount of MC form and the strong positive charge of the spi-
rocarbon. The equilibrium mol fraction of the MC form of 2 at
25 °C in the dark is determined by a molar absorption coefficient
(Table 1)16 to be 54%, which is much larger than that of 1 obtained
under UV irradiation (24%). This indicates that larger amount of MC
form of 2 is produced even without UV irradiation, which might be
one of the reasons for rapid reaction with CNꢀ. As shown in Figure
2, the activation enthalpy,
D
H–, for the reaction of 2 with CNꢀ is
13.7 kJ molꢀ1, which is much lower than that of 1 with CNꢀ
(22.6 kJ molꢀ1). This suggests that the nucleophilic addition of
CNꢀ to 2 is energetically more favorable. The Mulliken atomic
charge on the spirocarbon of 2(MC), as determined by the DFT cal-
culation, is 0.804, which is much higher than that of 1(MC) (0.756).
This is due to the strong withdrawal of p-electrons by the two nitro
groups. The strong positive charge of the spirocarbon of 2(MC),
therefore, probably lowers the activation energy for nucleophilic
CNꢀ addition.17 The above results suggest that the larger amount
of MC form and the strong positive charge of the spirocarbon of
2 enable the rapid reaction with CNꢀ.
In conclusion, we found that the spiropyran derivative, 2, con-
taining a dinitrophenolate moiety enables rapid, selective, and sen-
sitive CNꢀ detection in aqueous media18 without UV irradiation.
This is achieved by the stabilized MC form and the strong positive
charge of the spirocarbon of 2. The results presented here may con-
tribute to the design and development of more efficient and more
useful CNꢀ receptors based on the spiropyran platform.
11. Shiraishi, Y.; Itoh, M.; Hirai, T. Phys. Chem. Chem. Phys. 2010, 12, 13737–13745.
12. Flannery, J. B., Jr. J. Am. Chem. Soc. 1968, 90, 5660–5671.
13. Malatesta, V.; Neri, C.; Wis, M. L.; Montanari, L.; Millini, R. J. Am. Chem. Soc.
1997, 119, 3451–3455.
14. (a) Guo, X.; Zhou, Y.; Zhang, D.; Yin, B.; Liu, Z.; Liu, C.; Lu, Z.; Huang, Y.; Zhu, D. J.
Org. Chem. 2004, 69, 8924–8931; (b) Yagi, S.; Nakamura, S.; Watanabe, D.;
Nakazumi, H. Dyes Pigm. 2009, 80, 98–105.
15. (a) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R., Jr.; Montgomery, J. A.; Vreven, T.; Kudin, K. N.; Burant, J. C.;
Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.;
Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.;