Dynamic figure eight loop structure of meso-tetraaryl[32]octaphyrins(1.0.1. 0.1.0.1.0)

Article abstract of DOI:10.1021/jo9001189

3,3′-Diethyl substituents of the 2,2′-bipyrrole components in meso-tetraaryl[32]octaphyrins(1.0.1.0.1.0.1.0) affect the cavity shape through CH/π interactions and remarkably accelerate syn - anti conformational change of the 2,2′-bipyrrole components lead

Full text of DOI:10.1021/jo9001189

SCHEME 1. Unwinding-Rewinding Helicity Change in the
[36]Octaphyrin(2.1.0.1.2.1.0.1)
Dynamic Figure Eight Loop Structure of
meso-Tetraaryl[32]octaphyrins(1.0.1.0.1.0.1.0)
Megumi Mori, Toshifumi Okawa, Noriko Iizuna,
Kana Nakayama, Juha M. Lintuluoto,† and
Jun-ichiro Setsune*
Department of Chemistry, Graduate School of Science, Kobe
UniVersity, Nada-ku, Kobe 657-8501, Japan
setsunej@kobe-u.ac.jp
ReceiVed January 18, 2009
Mo¨bius aromaticity,6 inspired by a detailed analysis of twisted
π-systems of octaphyrins in the design of Mo¨bius molecules
by Herges.7 The unique stereochemical feature of octaphyrins
has potential application to chirality sensing and asymmetric
catalysis. In fact, we have reported that these octaphyrins can
undergo unidirectional helicity induction by reversible com-
plexation with optically active carboxylic acids,3e or by ir-
reversible metalation in the presence of optically active ancillary
ligand.3f Understanding dynamics of the figure eight confor-
mational change is fundamental for further exploring the
stereochemical aspect of octaphyrins, and thus the inversion
barriers of the figure eight loop in the [34]-octaphy-
rin(1.1.1.0.1.1.1.0) and [36]octaphyrin(2.1.0.1.2.1.0.1) were
estimated by Vogel and co-workers to be at least 85 kJ mol-1.2b,c
As a matter of fact, enantiomeric separation of the latter was
successfully performed.2c These octaphyrins are made of two
pairs of different dipyrrolic components and the inversion of
the helical figure eight loop requires unwinding of the molecular
twist followed by rewinding in the opposite way as depicted in
Scheme 1.
3,3′-Diethyl substituents of the 2,2′-bipyrrole components
in meso-tetraaryl[32]octaphyrins(1.0.1.0.1.0.1.0) affect the
cavity shape through CH/π interactions and remarkably
accelerate syn-anti conformational change of the 2,2′-
bipyrrole components leading to helicity change in the figure
eight loop of [32]octaphyrins.
Octaphyrins are composed of eight pyrrole units and some
structural variations in the number of π-electrons (30, 32, 34,
36, and 38) and of bridging meso-like carbons (0, 2, 4, 6, and
8) are known.1-5 The π-conjugation systems of octaphyrins in
a helical figure eight conformation are of great interest.2,3 For
example, Osuka reported octaphyrin metal complexes with
In contrast, it was shown that 2,3,6,7,11,12,15,16,20,21,24,25,
29,30,33,34-hexadecaethyl[32]octaphyrin(1.0.1.0.1.0.1.0) 1a hav-
ing four parts of 3,3′,4,4′-tetraethyl-2,2′-bipyrrole was rapidly
interchanging between the figure eight enantiomeric forms and
† Present address: Department of Synthetic Chemistry and Biochemistry,
Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
(1) (a) Sessler, J. L.; Seidel, D. Angew. Chem., Int. Ed. 2003, 42, 5134–
5175. (b) Latos-Gran´yn´ski, L. Angew. Chem., Int. Ed. 2004, 43, 5124–5128.
(2) (a) Vogel, E.; Bro¨ring, M.; Fink, J.; Rosen, D.; Schmickler, H.; Lex, J.;
Chan, K. W. K.; Wu, Y. D.; Plattner, D. A.; Nendel, M.; Houk, K. N. Angew.
Chem., Int. Ed. 1995, 34, 2511–2514. (b) Bro¨ring, M.; Jendrny, J.; Zander, L.;
Schmickler, H.; Lex, J.; Wu, Y. D.; Nendel, M.; Chen, J. G.; Plattner, D. A.;
Houk, K. N.; Vogel, E. Angew. Chem., Int. Ed. 1995, 34, 2515–2517. (c) Werner,
A.; Michels, M.; Zander, L.; Lex, J.; Vogel, E. Angew. Chem., Int. Ed. 1999,
38, 3650–3653. (d) Vogel, E.; Michels, M.; Zander, L.; Lex, J.; Tuzun, N. S.;
Houk, K. N. Angew. Chem., Int. Ed. 2003, 42, 2857–2862. (e) Bley-Escrich, J.;
Gisselbrecht, J.-P.; Michels, M.; Zander, L.; Vogel, E.; Gross, M. Eur. J. Inorg.
Chem. 2004, 49, 2–499.
(3) (a) Setsune, J.; Maeda, S. J. Am. Chem. Soc. 2000, 122, 12405–12406.
(b) Setsune, J.; Katakami, Y.; Iizuna, N. J. Am. Chem. Soc. 1999, 121, 8957–
8958. (c) Setsune, J.; Mori, M.; Okawa, T.; Maeda, S.; Lintuluoto, J. M. J.
Organomet. Chem. 2007, 692, 166–174. (d) Mori, M.; Setsune, J. Chem. Lett.
2007, 36, 244–245. (e) Lintuluoto, J. M.; Nakayama, K.; Setsune, J. Chem.
Commun. 2006, 69, 3492–3494. (f) Setsune, J.; Tsukajima, A.; Okazaki, N.;
Lintuluoto, J. M.; Lintuluoto, M. Angew. Chem., Int. Ed. 2009, 48, 771–775.
(4) (a) Seidel, D.; Lynch, V.; Sessler, J. L. Angew. Chem., Int. Ed. 2002, 41,
1422–1425. (b) Sessler, J. L.; Seidel, D.; Lynch, V. J. Am. Chem. Soc. 1999,
121, 11257–11258.
the theoretically estimated inversion barrier was as low as 25
2c
kJ mol-1
.
This helicity change of 1a occurs with keeping
diastereotopicity of the CH2 protons at the pyrrole ꢀ-position,
which is not consistent with the unwinding-rewinding mech-
anism. The helicity change is enabled by an alternating
stretching-compressing distortion of the rhombic cavity that
is enclosed by four panels of the planar dipyrrin unit connected
with four hinges in the form of bipyrrole C2-C2′ bonds
(Scheme 2). That is, stretching along a shorter diagonal axis of
the rhombic cavity accompanied by compressing along a longer
diagonal axis leads to a mirror image, whereby a bisdipyrrin
unit drawn with a heavy black line in Scheme 2 is interchanging
between anti and syn conformation. Vogel originally described
that the two enantiomers are interchanging via “tub” conforma-
tion like cyclooctatetraene,2b but its detailed dynamic feature
has remained to be clarified.
(5) (a) Shimizu, S.; Shin, J.-Y.; Furuta, H.; Ismael, R.; Osuka, A. Angew.
Chem., Int. Ed. 2003, 42, 78–82. (b) Shin, J.-Y.; Furuta, H.; Yoza, K.; Igarashi,
S.; Osuka, A. J. Am. Chem. Soc. 2001, 123, 7190–7191. (c) Geier, G. R., III;
Grindrod, S. C. J. Org. Chem. 2004, 69, 6404–6412.
(6) Tanaka, Y.; Saito, S.; Mori, S.; Aratani, N.; Shinokubo, H.; Shibata, N.;
Higuchi, Y.; Yoon, Z. S.; Kim, K. S.; Noh, S. B.; Park, J. K.; Kim, D.; Osuka,
A. Angew. Chem., Int. Ed. 2008, 47, 681–684.
(7) Herges, R. Chem. ReV. 2006, 106, 4820–4842.
10.1021/jo9001189 CCC: $40.75
Published on Web 03/27/2009
2009 American Chemical Society
J. Org. Chem. 2009, 74, 3579–3582 3579

SCHEME 2. Stretching-Compressing Helicity Change in
the [32]Octaphyrins(1.0.1.0.1.0.1.0)
1
FIGURE 1. Variable-temperature H NMR spectra of 1b in toluene-
d8 in the range -60 to 20 °C.
We have already shown that meso-tetraaryl[32]octaphyrins-
(1.0.1.0.1.0.1.0) are obtainable by the Rothemund-type reaction
of 2,2′-bipyrrole and arylaldehyde under acidic conditions or
by the “2+2” type condensation reaction of 2,2′-bipyrrole and
the corresponding bisazafulvene under neutral conditions.3a-c,8
The latter synthetic method reliably affords meso-tetraaryl[32]-
octaphyrins(1.0.1.0.1.0.1.0) as a main product. In the present
work, four meso-tetraphenyl[32]octaphyrins(1.0.1.0.1.0.1.0),
1b,3a,b 1c, 1d,3c and 1e,3c with different alkyl substituents on
the 2,2′-bipyrrole components were used to investigate the
dynamics of the figure eight loop inversion. meso-Tetra(3,5-
dimethoxyphenyl)[32]octaphyrin(1.0.1.0.1.0.1.0) 1c′ that is suited
for the VT NMR study because of its much better solubility than
1c was also prepared from 3,3′-diethyl-4,4′-dimethyl-2,2′-bipyrrole
by way of 5,5′-di(3,5-dimethoxybenzoyl)-3,3′-diethyl-4,4′-dimethyl-
2,2′-bipyrrole 2c′ and 6,6′-di(3,5-dimethoxyphenyl)-3,3′-diethyl-
4,4′-dimethyl-2,2′-bisazafulvene 3c′.
1
FIGURE 2. Variable-temperature H NMR spectra of 1d in toluene-
d8 in the range -40 to 80 °C.
1
Variable-temperature H NMR in d8-toluene of 1b and 1c′
which gave activation parameters ∆Hq (65.0 ( 1.3 kJ mol-1
)
having four parts of 3,3′,4,4′-tetraethyl-2,2′-bipyrrole and 3,3′-
diethyl-4,4′-dimethyl-2,2′-bipyrrole, respectively, showed only
one set of signals for the 2,2′-bipyrrole units even at -60 °C
(Figure 1 and Supporting Information). Therefore, the syn-anti
conformational change of the 2,2′-bipyrrole units is very fast
on the NMR time scale for 1b and 1c′ as well as for 1a. Since
the 3,3′- and 4,4′-diethyl groups appeared as a ABX3 pattern,
stretching-compressing helicity change is taking place.
In contrast, 1H NMR in d8-toluene of 1d having four parts of
4,4′-diethyl-3,3′-dimethyl-2,2′-bipyrrole showed two singlets at
2.90 and 1.94 ppm at -40 °C (Figure 2). They are associated
with the 3,3′-dimethyl protons of the 2,2′-bipyrrole units in the
syn and anti conformations. These two singlets coalesced at 40
°C and gave a broad singlet at 2.29 ppm at 80 °C. Since signals
due to the 4,4′-diethyl groups of 1d appear as a ABX3 pattern
(1.91, 1.62, 0.72 ppm) at 80 °C, stretching-compressing helicity
change is taking place. The activation energy (∆Gq313) calculated
on the basis of the coalescence temperature and the frequency
and ∆Sq (17.5 ( 0.4 J K-1 mol-1). The ∆Gq313 value calculated
by using these two parameters was 59.5 kJ mol-1, which is in
1
good agreement with the value based on the H NMR signal
coalescence shown above. It is remarkable that the coalescence
temperature of 1b and 1d differs by more than 100 °C, which
corresponds to the difference of activation energy by at least
ca. 20 kJ mol-1
.
1H NMR in d8-toluene at -20 °C of 1e having four parts of
3,3′-diisobutyl-4,4′-dimethyl-2,2′-bipyrrole also showed two
singlets at 1.66 and 1.36 ppm due to the 4,4′-dimethyl protons
of the 2,2′-bipyrrole units in the syn and anti conformations.
These two singlets coalesced at 30 °C to lead to a singlet at
1.45 ppm at 60 °C, which is indicative of similar site-exchanging
rate of 1e to that of 1d (Supporting Information). The activation
energy (∆Gq303) of 1e calculated on the basis of the coalescence
temperature and the frequency difference between the two
exchanging methyl sites is 62.2 kJ mol-1. These results indicate
that the 3,3′-diethyl groups of the 2,2′-bipyrrole components
drive the helicity change of the [32]octaphyrin(1.0.1.0.1.0.1.0)
much faster than the less bulky 3,3′-dimethyl groups and the
more bulky 3,3′-diisobutyl groups.
difference between the two exchanging methyl sites is 61.3 kJ
9a
mol-1
.
This helicity change of 1d was further studied by the
spin saturation transfer experiment (Supporting Information),9b
(8) Setsune, J.; Tanabe, A.; Watanabe, J.; Maeda, S. Org. Biomol. Chem.
2006, 4, 2247–2252.
(9) (a) Gutowsky, H. S.; Holm, C. H. J. Chem. Phys. 1956, 25, 1228–1234.
(b) Jarek, R. L.; Flesher, R. J.; Shin, S. K. J. Chem. Educ. 1997, 74, 978–982.
X-ray crystallography of 1e shows that all the isobutyl groups
at the 3,3′-positions of the anti-2,2′-bipyrrole units at the figure
eight crossing point are pushed out of the cavity (Figure 3, right),
3580 J. Org. Chem. Vol. 74, No. 9, 2009

SCHEME 3. A Model for Transition State Conformation
with a Square-Shaped Cavity (top) Stabilized by CH/π
Interactions of the Ethyl Terminal Protons and the Pyrrole
Rings (bottom)
FIGURE 3. Transannular close contact between C(28)-H and N(1′)
seen in the partial X-ray structure of 1b (left); X-ray structures of 1b
(center) and 1e (right). Ethyl and isobutyl groups at the crossing point
are shown by a ball-and-stick model.
so that the anti-2,2′-bipyrrole units come close together in the
region (3.4 Å) of van der Waals contact. This rhombic cavity
shape of 1e has a maximum overlap of π-orbitals along the
figure eight loop conformation. On the other hand, X-ray
crystallography of 1a and 1b indicates that all the 3,3′-diethyl
groups of the anti-2,2′-bipyrrole units at the crossing point of
the figure eight loop are directed inside the cavity (Figure 3,
center).2b,3e Figure 3 (left) shows that the ethyl terminal carbon
C(28) attached to the N(3)-pyrrole of 1b is positioned 3.418 Å
from the pyrrole nitrogen N(1′). One of the methyl protons
C(28)-H at an ideal gauche position is right over the N(1′) atom
at a distance of ca. 2.6 Å. This is in the range of the van der
Waals contact between N and H atom. There are four such
transannular CH/π interactions10 with the same geometry. The
transannular distances 4.6 and 4.8 Å at the figure eight crossing
point of 1a and 1b, respectively, are longer than that of 1e.
Actually, a torsion angle N-CR-CR-N (34.9° on average) in
the syn-2,2′-bipyrrole units of 1b is larger than that (21.6°) of
1e and a torsion angle N-CR-CR-N (148.1°) in the anti-2,2′-
bipyrrole units of 1b is smaller than that (161.1° on average)
of 1e.
The UV-vis absorption maximum of 1d at 578 nm is very
similar to that of 1e at 580 nm in CH2Cl2, but it is red-shifted
with respect to that of 1b and 1c at 570 nm. These spectral
features suggest that 1d has a π-conjugation system enclosing
a narrower rhombic cavity like that of 1e and that 1c has a
π-conjugation system enclosing a wider rhombic cavity like that
of 1b as seen in the X-ray crystallography. Similar site-
exchanging rates and UV-vis absorption maxima of 1d and
1e suggest that the steric crowding of the 3,3′-dialkyl groups
does not affect much the shape of the rhombic cavity and the
dynamics of the helicity change. The decrease in the π-conjuga-
tion of 1b relative to 1d and 1e seems to be compensated by
the quadruple CH/π interactions of the ethyl terminal protons
at the figure eight crossing point as noted above.
explain the reason why ethyl groups at the 3,3′-position of the
2,2′-bipyrrole units are remarkably promoting helicity change
of the [32]octaphyrins.
In summary, the substitution pattern of peripheral alkyl groups
of [32]octaphyrin(1.0.1.0.1.0.1.0) has a great influence not only
on the conformation but also on the dynamics of the figure eight
loop. The present finding on the helicity change of [32]octa-
phyrins is of valuable in their application to chirality-related
functional materials.
Experimental Section
5,5′-Di(3,5-dimethoxybenzoyl)-3,3′-diethyl-4,4′-dimethyl-2,2′-
bipyrrole (2c′). POCl3 (0.78 mL, 8.4 mmol) was added by syringe
to N,N-dimethyl-3,5-dimethoxybenzamide (1.67 g, 8.0 mmol) under
argon and the mixture was stirred for 2 h at room temperature to
afford yellow solid. To this reaction mixture was added 3,3′-diethyl-
4,4′-dimethyl-2,2′-bipyrrole (346 mg, 1.60 mmol) dissolved in 1,2-
dichloroethane (7.9 mL) through syringe. The resulting solution
was stirred under argon overnight, and then heated at 70-80 °C
with stirring for 6 h. After K2CO3 aqueous solution (4.6 g/8 mL)
was added carefully, the mixture was refluxed for 3 h and then
partitioned between CH2Cl2 and water. The organic layer was dried
over anhydrous K2CO3 and then evaporated under vacuum. The
residue was chromatographed on silica gel with CH2Cl2-acetone
(5:1). The red fraction was collected and recrystallized from
CH2Cl2-hexane to give pale violet powders (680 mg, 1.25 mmol).
Yield 78%. 1H NMR (400 MHz, δ value, in CDCl3) 8.80 (br, 2H),
6.82 (s, 4H), 6.62 (s, 2H), 3.84 (s, 12H), 2.54 (q, 4H), 2.15 (s,
6H), 1.11 (t, 6H). ESI-MS (found/calcd for C32H36N2O6 + H+)
545.17/545.27. Anal. Calcd for C32H36N2O6: C, 70.57; H, 6.66; N,
5.14. Found: C, 70.27; H, 6.79; N, 5.22.
6,6′-Di(3,5-dimethoxyphenyl)-3,3′-diethyl-4,4′-dimethyl-2,2′-
bisazafulvene (3c′). NaBH4 (890 mg, 23.6 mmol) was added in
small portions over 30 min to a stirred solution of 5,5′-di(3,5-
dimethoxybenzoyl)-3,3′-diethyl-4,4′-dimethyl-2,2′-bipyrrole (256
mg, 0.47 mmol) in a mixture of MeOH (10 mL) and THF (15 mL)
under argon. The resulting reaction mixture was stirred at room
temperature for 3 h and then partitioned between CH2Cl2 and water.
The organic layer was dried over anhydrous K2CO3 and then
evaporated under vacuum. A mixture of the vacuum-dried crude
diol, di-tert-butyl dicarbonate (307 mg, 1.41 mmol), and 4-dim-
ethylaminopyridine (2.9 mg, 0.024 mmol) in dry THF (24 mL) was
stirred at room temperature for 2 h under argon. The reaction
mixture was evaporated under vacuum and the residue was washed
with MeOH to give the product (193 mg, 0.38 mmol). Yield 80%.
1H NMR (400 MHz, δ value, in CDCl3) 7.48 (s, 4H), 6.89 (s, 2H),
6.52 (s, 2H), 3.86 (s, 12H), 3.04 (q, 4H), 2.20 (s, 6H), 1.15 (t, 6H).
ESI-MS (found/calcd for C32H36N2O4 + H+) 513.25/513.28. Anal.
The transition state in the stretching-compressing motion
of [32]octaphyrins would take conformation with a square-
shaped cavity where π-conjugation through a bipyrrole 2,2′-
bond is cut off (Scheme 3). Molecular modeling suggests that
8-fold CH/π interactions between the ꢀ-pyrrolic ethyl terminal
protons and the adjacent pyrrole π-systems can take place within
the orthogonally twisted 2,2′-bipyrrole units to stabilize the
square-shaped transition state in the helicity change. This might
(10) (a) Tsuzuki, S.; Honda, K.; Uchimaru, T.; Mikami, M.; Tanabe, K. J. Am.
Chem. Soc. 2000, 122, 11450–11458. (b) Tsuzuki, S.; Honda, K.; Uchimaru,
T.; Mikami, M.; Tanabe, K. J. Am. Chem. Soc. 2000, 122, 3746–3753.
J. Org. Chem. Vol. 74, No. 9, 2009 3581

Calcd for C32H36N2O4: C, 74.97; H, 7.08; N, 5.46. Found: C, 74.98;
H, 6.99; N, 5.00.
sadabs program. The structure was solved and refined by full-matrix
least-squares calculations on F2, using the shelxtl 97 program
package.11 M ) 1434.04, T ) 193(2) K, monoclinic, space group
P2(1)/c, a ) 25.9786(18) Å, b ) 16.6372(12) Å, c ) 20.7138(14)
Å, ꢀ ) 105.2820(10)°, V ) 8636.2(10) Å3, Z ) 4, Fcalc ) 1.103 g
cm-3, µ(Mo KR) ) 0.064 mm-1, reflections collected 44038, unique
reflections 15589 (Rint ) 0.0450), GOF ) 1.049, final R indices [I
> 2σ(I)]: R1 ) 0.0582, wR2 ) 0.1339, R indices (all data) R1 )
0.1230, wR2 ) 0.1640. CCDC reference number 721780.
3,6,12,15,21,24,30,33-Octaethyl-2,7,11,16,20,25,29,34-octa-
methyl-9,18,27,36-tetra(3,5-dimethoxyphenyl)[32]octaphyrin-
(1.0.1.0.1.0.1.0) (1c′). A mixture of 3,3′-diethyl-4,4′-dimethyl-2,2′-
bipyrrole (70 mg, 0.325 mmol) and 6,6′-di(3,5-dimethoxyphenyl)-
3,3′-diethyl-4,4′-dimethyl-2,2′-bisazafulvene (166 mg, 0.325 mmol)
in dry CH2Cl2 (8 mL) was stirred at room temperature under argon
for 16 h. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (221 mg,
0.975 mmol) was added to the reaction mixture and the resulting
blue violet solution was stirred at room temperature for 2 h. After
passing through Celite, the CH2Cl2 solution was washed with 1%
HClO4 aqueous solution and then with 10% NaOH aqueous
solution. The organic layer was separated, dried over anhydrous
Na2SO4, and chromatographed on silica gel with CH2Cl2-acetone
(10:1). The violet fraction was recrystallized from CH2Cl2-MeOH
to give 1c′ (35 mg, 0.024 mmol). Yield 15%. 1H NMR (400 MHz,
δ value, in CDCl3) 16.02 (s, 4H), 7.34 (s, 8H), 7.22 (s, 4H), 3.76,
3.46 (s × 2, 12H × 2), 3.23, 3.05 (q × 2, 8H × 2), 1.76 (s, 24H),
1.40 (t, 24H). UV-vis (λmax (log ꢀ) in CH2Cl2) 372.5 (4.51), 572
(4.99) nm. ESI-MS (found/calcd for C92H104N8O8 + H+) 1448.80/
1448.65. Anal. Calcd for C92H104N8O8: C, 76.21; H, 7.23; N, 7.73.
Found: C, 75.94; H, 7.34; N, 7.67.
Acknowledgment. This work was supported by Grant-in-
Aid for Scientific Research (No.18550058) from the Ministry
of Education, Culture, Sports, Science and Technology, Japan.
The author is also grateful to the CREST program (the Japan
Science and Technology Agent) and the VBL project (Kobe
University).
Supporting Information Available: Outline of the synthetic
procedure for 1c and 1c′ with characterization data for 5,5′-
dibenzoyl-3,3′-diethyl-4,4′-dimethyl-2,2′-bipyrrole (2c) and 6,6′-
diphenyl-3,3′-diethyl-4,4′-dimethyl-2,2′-bisazafulvene (3c) as the
synthetic precursors of 1c, details of spin saturation transfer
experiment of 1d including 1H NMR spectra at 243 K in toluene-
d8 with and without irradiation at one of the two exchanging
Me signals, and a plot of ln(k/T) as a function of T-1, variable-
temperature 1H NMR spectra of 1c′ and 1e in toluene-d8 between
-60 to 80 °C, and an Ortep drawing of 1e. This material is
available free of charge via the Internet at http://pubs.acs.org.
3,6,12,15,21,24,30,33-Octaethyl-2,7,11,16,20,25,29,34-octa-
methyl-9,18,27,36-tetraphenyl[32]octaphyrin(1.0.1.0.1.0.1.0)
1
(1c). Yield 12%. H NMR (400 MHz, δ value, in CDCl3) 15.05
(s, 4H), 7.53-7.42 (m, 20H), 2.73, 2.58 (br × 2, 8H × 2), 1.33
(br, 24H), 0.98 (t, 24H). UV-vis (λmax (log ꢀ) in CH2Cl2) 373
(4.64), 570.5 (5.09) nm. ESI-MS (found/calcd for C84H88N8 + H+)
1208.71/1208.66. Anal. Calcd for C84H88N8 ·(CH3OH): C, 80.22;
H, 7.46; N, 9.02. Found: C, 80.00; H, 7.47; N, 8.86.
JO9001189
X-ray Crystallography of (1e) C100H120N8. An X-ray diffrac-
tometer equipped with a CCD detector was used for data collection.
An empirical absorption correction was applied with use of the
(11) Sheldrick, G. M. SHELXTL 5.10 for Windows NT, Structure Determi-
nation Software Programs; Bruker Analytical X-ray Systems, Inc.: Madison, WI,
1997.
3582 J. Org. Chem. Vol. 74, No. 9, 2009