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Figure 3. The proposed distorted conjugation of 1.
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same tilt angle with the molecule above it (not shown for
simplicity). The other carbonꢀcarbon triple bond in
molecule A has a tilt angle q2=30.2° with the penta-
fluorophenyl ring of molecule B and tilt angle q3=31.5°
with the phenyl ring of molecule C. Moreover, we think
interactionsbetweenthefluorineatomsinmoleculeBwith
the p-orbitals of the acetylene in molecule A also
contribute to the solid stacking. Therefore, the coulombic
interactions and the acetylene–arene p–p interactions, in
addition to the fluorine–p interactions, contribute to the
high order stacking of 1.
13. Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron
Lett. 1975, 4467–4470.
Though aggregation was not evident from the 1H NMR
spectrum of 1 [32.5 and 155 mM in CDCl3], a red shift
intheUV-spectrum(hexaneandacetonitrile)doessuggest
aggregation in less polar solvents as the concentration is
increased.
14. Pure product 1 (yellow solid) was isolated in 55%: mp
135–137°C. 1H NMR (200 MHz, CDCl3): l 6.92–6.93 (dd,
1H, J1=2.4 Hz, J2=1.1 Hz), 7.32–7.45 (m, 8H), 7.54–7.59
(m, 2H). 19F NMR (376 MHz, CDCl3): l −136.2 (sm, 2F),
−154.2 (m, 1F), −162.9 (sm, 2F). 13C NMR (50 MHz,
CDCl3) l 84.95 (C), 87.03 (C), 90.58 (C), 93.67 (C), 95.53
(C), 110.79–111.52 (C, dt, J1=3.3, J2=17.3 Hz), 121.97–
122.07 (C, d, J=5.45 Hz), 126.61 (CH), 129.41 (CH),
129.08 (CH), 129.21 (CH), 131.74 (CH), 131.88 (CH) and
a series of broad peaks in the aromatic region (Ar C-F).
HR-MS: calcd for m/z 394.078092, found m/z 394.077464.
15. Single-crystal X-ray diffraction analysis of 1. Crystal
structure data for 1 (single crystal from dichloromethane/
isopropanol): formula C24H11F5, M=394.33, crystal
dimensions 0.3×0.2×0.25 mm, monoclinic, space group
The X-ray confirms that the conjugation of the chro-
mophore of 1 is distorted. The hydrogen bonded to C7
(H7) is 45° out of the plane of the pentafluoro ring
(dihedral angle of (H7C7C1) and the mean plane of the
pentafluorophenyl ring is 135°). This requires the p-
orbitalofC7 tobeat45°withthatofC1 (Fig. 3). Therefore,
the pentafluoro ring is in ‘semi’ conjugation with the rest
of the chromophore.
,
P21, a=7.6530(4), b=13.4288(8), c=8.9323(4) A, i=
Acknowledgements
3
94.340(2)°, V=915.35(8) A , Z=2, zcalcd=1.431 g cm−3
.
,
The authors are grateful to Mr. Y.-S. Chen, Dr. K.
Kirschbaum and Dr. E. A. Zhurova for the valuable
comments during X-ray measurement. We also thank
Professor J. Gano, Professor G. S. Hammond and
Professor T. H. Kinstle for the insightful discussions. A
Fellowship from the McMaster Endowment to one of the
authors (B.R.K.) is gratefully acknowledged. This work
was supported by the National Science Foundation NSF
c DMR-0091689. The authors sincerely appreciate this
support.
Bruker AXS SMART platform diffractomator (Ag-Ka,
u=0.56086 A), three different settings and 0.3° incre-
,
ment ꢀ scan, 2q<40°, T=150 K. 5804 measured reflections,
all 3144 independent reflections were used in the refine-
ment. Data integration was carried out with SAINT,
corrections for absorption and decay were applied using
SADABS. Structure solution and refinement: direct meth-
ods, non-hydrogen atoms were refined including
anisotropic thermal parameters, hydrogen atoms were
refined isotropically, R=0.0553 [I>2|(I)].
16. Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc.
1996, 118, 1019–1027.
References
17. The distance between the aromatic centroid of the pen-
tafluoro phenyl ring in molecule A and the center of the
,
1. (a) Desiraju, G. R. Crystal Engineering: Design of Organic
carbonꢀcarbon triple bond in molecule B is 4.097 A.