Tetramethyleneethane Radical Cation and Biradical
A R T I C L E S
100), 303 (14), 224 (13), 211 (14), 172, (14), 121 (19). Anal. Calcd
for C22H20O3: C, 79.50; H, 6.07. Found: C, 79.30; H, 6.12.
9a. Colorless powder (CH2Cl2-ether), mp 210-212 °C. H NMR
DFT calculation and careful consideration to the spin contami-
nation in 7a••.30 Our TDDFT calculation of 7a•• may not be
accurate because of spin contamination. However, the conclusion
that the ground state of 7a•• is the singlet is still adequate by a
process of elimination. Note that the TDDFT calculation of the
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(200 MHz, CDCl3): δppm 2.8-2.9 (m, 4 H), 3.30 (d, J ) 4.4 Hz, 1 H),
3.44 (dd, J ) 4.8, 4.4 Hz, 1 H), 5.53 (s, 1 H), 5.57 (d, J ) 4.8 Hz, 1
H), 7.2-7.5 (m, 10 H). 13C NMR (50 MHz, CDCl3) δppm 28.3, 28.6,
38.0, 39.2, 79.0, 81.6, 116.8, 118.0, 126.6 (2 C), 126.7 (2 C), 128.1,
128.2, 128.7 (2 C), 128.8, 129.0 (2 C), 131.1, 131.4, 132.4, 138.7,
139.1. IR (KBr): ν 3400, 3050, 2950, 2850, 2800, 2230, 1600, 1495,
1460, 1365, 1310, 1275, 1185, 1165, 1025, 1010, 960, 925, 905, 850,
815, 760, 755 cm-1. MS (25 eV) m/z (relative intensity/%): 350 (M+,
33), 272 (100, M+ - FN), 271 (22), 270 (13), 243 (28), 181 (10).
Anal. Calcd for C24H18N2O: C, 82.26; H, 5.18; N, 7.99. Found: C,
81.99; H, 5.34; N, 7.94.
3
pure triplet state 7a•• cannot explain the observed transient
absorption spectra of 7a••.
The results serve as the foundation of a new method to
produce a variety of aryl-substituted TME radical cations and
biradicals and to analyze their properties. As a matter of fact,
we also studied similar PET reactions of thiophene, pyrrole,
and 5,5-dimethyl-1,3-cyclopentadiene analogues (Chart 4, 21a-
23a) of 6; the results will be reported elsewhere. As compared
to trimethylenemethane,31 TME has not been used very much
for applications. Therefore, our results provide meaningful
information not only for pure TME chemistry but also for the
molecular design of TMEs for many applications, such as in
organic syntheses and molecular devices, where the TME
framework can be used as a building block of functionalized
organic materials.
14a. Colorless powder (CH2Cl2-ether), mp 218-220 °C. 1H NMR
(200 MHz, CDCl3): δppm 2.6-3.2 (m, 4 H), 3.32 (s, 3 H), 3.96 (s, 3
H), 5.98 (s, 2 H), 7.2-7.6 (m, 10 H). 13C NMR (50 MHz, CDCl3):
δppm 28.0, 29.6, 54.0, 55.1, 57.8, 58.9, 83.6, 85.5, 113.4, 115.7, 126.4
(2 C), 126.7 (2 C), 128.1, 128.2, 128.8 (2 C), 128.9 (2 C), 130.4 (2 C),
132.0, 132.5, 138.8, 139.0, 161.1, 163.6. IR (KBr): ν 3450, 3050, 2950,
2850, 2250, 1760, 1680, 1630, 1600, 1575, 1495, 1445, 1435, 1360,
1240, 1190, 1160, 1140, 1115, 1075, 1050, 1025, 1010, 955, 935, 910
cm-1. MS (70 eV) m/z (relative intensity/%): 466 (M+, 8), 330 (25),
273 (24), 272 (100, M+ - DMDCF), 271 (21), 270 (54), 243 (28),
241 (21), 165 (20), 163 (21), 91 (55). Anal. Calcd for C28H22N2O5‚
(H2O)0.67: C, 70.28; H, 4.92; N, 5.85. Found: C, 70.30; H, 4.84; N,
5.90.
Experimental Section
General Methods. All melting points are uncorrected. Elemental
analyses were performed by the Research and Analytical Center for
Giant Molecules, Graduate School of Science, Tohoku University. 1H
NMR spectra were recorded at 200 MHz on a Varian Gemini 2000.
13C NMR spectra were obtained at 50 MHz on a Varian Gemini 2000.
Mass spectrometry (MS) was performed on a Hitachi M-2500 mass
spectrometer with electron impact. Steady-state photolysis was carried
out at 20 ( 1 °C using an Ushio 2-kW Xe short arc lamp through an
aqueous IR filter and a Toshiba L-39 cutoff filter (λ > 360 nm) for
DCA. CH3CN was dried and distilled successively from P2O5 and CaH2.
CH2Cl2 was dried and distilled from CaH2.
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exo-15a. Colorless powder (CH2Cl2-ether), mp 231-234 °C. H
NMR (200 MHz, CDCl3): δppm 2.6-3.0 (m, 4 H), 3.59 (s, 2 H), 5.63
(s, 2 H), 7.3-7.5 (m, 10 H). 13C NMR (50 MHz, CDCl3): δppm 28.1
(2 C), 50.4 (2 C), 81.5 (2 C), 126.6 (4 C), 128.0 (2 C), 128.1 (2 C),
128.9 (4 C), 133.2 (2 C), 138.8 (2 C), 170.1 (2 C). IR (KBr): ν 3900
(br), 1875, 1840, 1785, 1670, 1620, 1595, 1570, 1490, 1440, 1365,
1300, 1245, 1230, 1210, 1170, 1155, 1075, 1040, 1025, 975, 940, 920,
890, 870, 855, 840, 820, 780, 755, 735 cm-1. MS (70 eV) m/z (relative
intensity/%): 371 (M+ + 1, 23), 370 (M+, 91), 273 (22), 272 (100,
M+ - MA), 243 (20). Anal. Calcd for C24H18O4‚(H2O)0.33: C, 76.58;
H, 5.00. Found: C, 76.62; H, 5.03.
Physical Data of 6, 9, and 14-16. 6a. Colorless cubes (n-hexane),
mp 82-84 °C. 1H NMR (200 MHz, CDCl3): δppm 5.24 (s, 4 H), 7.1-
7.2 (m, 10 H), 7.41 (s, 2 H). 13C NMR (50 MHz, CDCl3): δppm 114.8
(2 C), 126.2 (2 C), 127.2 (4 C), 127.5 (4 C), 127.9 (2 C), 140.3 (2 C),
140.4 (2 C), 142.1 (2 C); IR (KBr) ν 3150, 3100, 3050, 1600, 1570,
1530, 1490, 1445, 1320, 1300, 1220, 1200, 1140, 1120, 1080, 1055,
1025, 900, 895, 880, 830, 810, 780, 775 cm-1. MS (25 eV) m/z (relative
intensity/%): 273 (M+ + 1, 15), 272 (M+, 100), 243 (33), 181 (21),
165 (52), 91 (17). Anal. Calcd for C20H16O: C, 88.20; H, 5.92. Found:
C, 88.06; H, 6.06.
6b. Pale yellow solid (n-hexane), mp 79-80 °C. 1H NMR (200 MHz,
CDCl3): δppm 3.79 (s, 6 H), 5.16 (d, J ) 1.6 Hz, 4 H), 6.73 (AA’BB’,
J ) 8.9 Hz, 4 H), 7.11 (AA′BB′, J ) 8.9 Hz, 4 H), 7.41 (s, 2 H); 13C
NMR (50 MHz, CDCl3) δppm 55.2 (2 C), 113.2 (4 C), 126.4 (4 C),
128.3 (4 C), 133.1 (2 C), 139.6 (2 C), 142.0 (2 C), 159.2 (2 C). IR
(KBr): ν 1603, 1578, 1533, 1508, 1458, 1394, 1304, 1178, 1138, 1113,
1022, 841, 750 cm-1. MS (70 eV) m/z (relative intensity/%): 332 (M+,
1
endo-15a. Colorless powder (CH2Cl2-ether), mp 247-249 °C. H
NMR (200 MHz, CDCl3): δppm 2.7-4.0 (m, 4 H), 3.94 (dd, J ) 4.0,
2.3 Hz, 2 H), 5.67 (dd, J ) 4.0, 2.3 Hz, 2 H), 7.3-7.5 (m, 10 H). 13
C
NMR (50 MHz, CDCl3): δppm 28.5 (2 C), 52.5 (2 C), 79.1 (2 C), 126.4
(4 C), 127.9 (2 C), 128.6 (4 C), 130.4 (2 C), 131.4 (2 C), 139.1 (2 C),
167.9 (2 C). IR (KBr): ν 3450 (br), 1870, 1785, 1490, 1440, 1360,
1300, 1220, 1110, 1070, 1025, 980, 960, 930, 835, 810, 770 cm-1
.
MS (70 eV) m/z (relative intensity/%): 371 (M++ 1, 15), 370 (M+,
56), 273 (22), 272 (100, M+ - MA), 243 (24), 181 (12), 165 (19), 91
(12). Anal. Calcd for C24H18O4‚(H2O)0.25: C, 76.89; H, 4.97. Found:
C, 76.93; H, 4.96.
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trans-16a. Colorless needles (CH2Cl2-ether), mp 151-152 °C. H
NMR (200 MHz, CDCl3): δppm 2.5-2.6 (m, 4 H), 3.13 (s, 3 H), 3.53
(d, J ) 4.8 Hz, 1 H), 3.70 (dd, J ) 5.4, 4.8 Hz, 1 H), 3.79 (s, 3 H),
5.46 (s, 1 H), 5.78 (d, J ) 5.4 Hz, 1 H), 7.3-7.5 (m, 10 H). 13C NMR
(50 MHz, CDCl3): δppm 27.2, 29.8, 50.0, 50.8, 51.5, 52.6, 79.1, 81.7,
125.6, 126.4 (2 C), 126.8 (2 C), 127.1, 127.3, 127.9, 128.4 (4 C), 133.5,
136.0, 139.7, 140.2, 170.3, 172.2. IR (KBr): ν 3450, 3050, 2950, 2850,
1745, 1735, 1595, 1495, 1430, 1365, 1320, 1305, 1075, 1015, 980,
900, 865, 820, 760, 700, 680 cm-1. MS (70 eV) m/z (relative intensity/
%): 417 (M+ + 1, 14), 416 (M+, 45), 273 (23), 272 (100, M+ - DMF),
243 (22), 181 (12), 165 (15), 91 (15). Anal. Calcd for C26H24O5: C,
74.98; H, 5.81. Found: C, 74.82; H, 5.86.
exo, cis-16a. Colorless needles (CH2Cl2-ether), mp 177-179 °C.
1H NMR (200 MHz, CDCl3): δppm 2.5-3.0 (m, 4 H), 3.44 (s, 2 H),
3.75 (s, 6 H), 5.49 (s, 2 H), 7.2-7.5 (m, 10 H). 13C NMR (50 MHz,
CDCl3): δppm 28.1 (2 C), 51.3 (2 C), 52.4 (2 C), 80.3 (2 C), 125.8 (2
C), 126.7 (4 C), 127.4 (2 C), 128.6 (4 C), 135.8 (2 C), 139.5 (2 C),
(30) As one of the referee pointed out, it is not a good idea to judge the electronic
state of 7••, especially the singlet state 17••, with UDFT calculation, because
these “singlet” species must be a mixture of singlet and triplet states (spin
contamination). The most straightforward way to solve the problem of
multiplicity may be an ESR study of 7•• and a calculation study of 7•• by
uisng MP2, the complete active space SCF (CASSCF), or the perfect-pairing
general valence bond (GVB-PP) method. These studies are now in progress
and will be published elsewhere.
(31) (a) Maiti, A.; Gerken, J. B.; Masjedizadeh, M. R.; Mimieux, Y. S.; Little,
R. D. J. Org. Chem. 2004, 69, 8574-8582. (b) Allan, A. K.; Carroll, G.
L.; Little, R. D. Eur. J. Org. Chem. 1998, 1-12. (c) Little, R. D. Chem.
ReV. 1996, 96, 93-114. (d) Bregant, T. M.; Groppe, J.; Little, R. D. J.
Am. Chem. Soc. 1994, 116, 3635-3636. (e) Jacobs, S. J.; Shultz, D. A.;
Jain, R.; Novak, J.; Dougherty, D. A. J. Am. Chem. Soc. 1993, 115, 1744-
1753. (f) Matsumoto, T.; Ishida, T.; Koga, N.; Iwamura, H. J. Am. Chem.
Soc. 1992, 114, 9952-9959. (g) Dougherty, D. A. Acc. Chem. Res. 1991,
24, 88-94. (h) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1986, 25, 1-20.
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