1,4-Phenylene-bridged hexaphyrin dimers

Article abstract of DOI:10.1002/ejoc.201200080

1,4-Phenylene-bridged [26]hexaphyrin dimer 3 was synthesized by the condensation of 1,4-phenylene-bridged tetrapyrrole carbinol 7 with tetrapyrromethane 8. The dimeric structure of 3 was confirmed by X-ray analysis. ¹H NMR spectroscopy revealed

Full text of DOI:10.1002/ejoc.201200080

FULL PAPER
DOI: 10.1002/ejoc.201200080
1,4-Phenylene-Bridged Hexaphyrin Dimers
Hirotaka Mori,[a] Naoki Aratani,[a,b] and Atsuhiro Osuka*[a]
Keywords: Porphyrinoids / Hexaphyrin / Rhodium / Aromaticity
1,4-Phenylene-bridged [26]hexaphyrin dimer 3 was synthe-
sized by the condensation of 1,4-phenylene-bridged tetra-
pyrrole carbinol 7 with tetrapyrromethane 8. The dimeric
structure of 3 was confirmed by X-ray analysis. 1H NMR
complexes 9, which were prepared by RhI metalation of 4.
Complexes 9 were quantitatively oxidized by MnO2 to
[26]hexaphyrn dimers 10 without conformational change.
The structure of 10LL-dl was determined by X-ray analysis
spectroscopy revealed that 3 and its [28]hexaphyrin conge- to confirm the caterpillar-type conformational isomerization.
ners 4 exist as conformational mixtures in solution. Such con-
formational dynamics were found to be frozen for their RhI
The RhI complexes 9 constitute rare examples of covalently
linked, antiaromatic porphyrinoid dimers.
in terms of its rectangular and planar conformation, strong
aromaticity and small HOMO–LUMO gap (ca. 1.21 eV).
Introduction
In recent years, increasing attention has been focused on
expanded porphyrins that consist of more than five pyrrolic
subunits.[1] Continuous efforts have been devoted to reveal
the appealing properties of expanded porphyrins, such as
multimetal coordination,[2] facile aromatic-to-antiaromatic
switching,[3] a large two-photon absorption cross-section[4]
and molecular twists to form Möbius aromatic and an-
tiaromatic systems,[5,6] which are not shared with por-
phyrins. Despite this progress, there have been only a few
examples of covalently linked expanded porphyrin oligo-
mers due to their difficult syntheses.[7] This is in sharp con-
trast to the chemistry of porphyrin oligomers, which has
been extensively studied in relation to artificial photosyn-
thesis, oxygen-reducing catalysts, etc.[8] A recent active re-
search trend is to explore highly conjugated porphyrin
oligomers that have low-energy absorption bands, a large
nonlinear optical response or high electron conductivity.[9]
For these purposes, expanded porphyrin oligomers may be
more promising owing to their large electronic circuits and
lower highest occupied molecular orbital (HOMO)–lowest
unoccupied molecular orbital (LUMO) gaps. Despite this
promise, rational synthetic routes to covalently linked ex-
panded porphyrins have been scarcely developed.
Hexaphyrin
1 can be reduced to [28]hexaphyrin 2
(Scheme 1), which exists as a dynamic conformational mix-
ture in solution and includes twisted Möbius aromatic con-
formers.[6b]
We wish to report the synthesis of a 1,4-phenylene-
bridged [26]hexaphyrin dimer and its RhI complexes as the
first step to explore conjugated expanded oligomers. [26]-
Hexaphyrin 1,[1e,10] is a representative expanded porphyrin
Scheme 1. Redox interconversion between 1 and 2, and 3 and 4.
Results and Discussion
[a] Department of Chemistry, Graduate School of Science, Kyoto
University,
The synthetic route to 1,4-phenylene-bridged [26]hexa-
phyrin 3 is outlined in Scheme 2. α-Selective tetraacylation
of 1,4-phenylene-bridged bis(dipyrromethane) 5[11] with
phenylmagnesium bromide and pentafluorobenzoyl chlor-
ide provided 6 in 79% yield, which was quantitatively re-
duced with NaBH4 to tetracarbinol 7. The condensation
Sakyo-ku, Kyoto 606-8502, Japan
Fax: +81-75-753-3970
E-mail: osuka@kuchem.kyoto-u.ac.jp
[b] PRESTO Japan Science and Technology Agency,
Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200080.
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H. Mori, N. Aratani, A. Osuka
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reaction of 7 with tetrapyrromethane 8 was conducted in a conformational mixture. The UV/Vis/NIR spectrum of 3SS
ratio of 1:2.2 in CH2Cl2 with the aid of p-toluenesulfonic exhibited a sharp Soret-like band at 569 nm and weak Q-
acid for 2 h, and the resulting reaction mixture was oxidized like bands at 723, 788, 909 and 1031 nm, which is very sim-
with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ, ilar to that of a mixture of 3 (Figure 2), indicating that the
8.0 equiv.) for an additional 1 h.[12] After the usual workup, conformational changes may have only a minor influence
repeated column chromatography gave 3 in 7% yield. on the absorption characteristics. Exciton coupling of the
HRMS (ESI-TOF) indicated the parent ion peak of 3 at two hexaphyrin chromophores is suggested as the full width
m/z = 2662.1943 (calcd. for C126H31N12F50 [M – H]– at half maximum of the Soret-like band is 2431 cm–1 in 3,
1
2662.2022). The H NMR spectrum of 3 displayed a com- which is wider than that in 1 (1459 cm–1).
plicated feature, which indicated the existence of three con-
formational isomers, SS, SL and LL, formed by caterpillar-
type conformational isomerization[13] (Scheme 3); S and L
denote the short or long side, respectively, of the hexaphyrin
where the 1,4-phenylene spacer is linked. These isomers
were very difficult to separate because of severe tailing on
silica gel and fast conformational isomerization. Fortu-
nately, we obtained a crystal of 3 from a solution of the
isomeric mixture. The structure was revealed by X-ray dif-
fraction analysis to be SS, in which the two [26]hexaphyrin
moieties are planar and held in a coplanar manner (Fig-
ure 1). The 1,4-phenylene bridge is perpendicular to the
hexaphyrin planes with dihedral angles of 54.8° and 60.8°.
The 1H NMR spectrum of the crystal in CDCl3 was consis-
tent with the crystal structure and featured four signals in
the range of δ = 9.60–9.04 ppm due to the outer β-protons,
two signals at δ = –2.07 and –2.09 ppm due to the inner β-
protons, two broad signals at δ = –1.23 and –1.89 ppm due
to the inner NH groups and a singlet at δ = 8.97 ppm due
to the 1,4-phenylene unit. Upon standing, the 1H NMR
spectrum showed the gradual appearance of signals due to
3SL and 3LL and finally reached that of the equilibrated
Scheme 3. Conformational isomers of [26]hexaphyrin dimer RhI
complexes. meso-Pentafluorophenyl substituents are omitted for
clarity.
Figure 1. X-ray crystal structure of 3SS. (a) Top and (b) side view.
The thermal ellipsoids are shown at 50% probability. Solvent mole-
cules are omitted for clarity.
According to the known chemistry of 1 and 2, dimer 3
was reduced with NaBH4 to [28]hexaphyrin dimer 4, which
was oxidized back to 3 with MnO2, both quantitatively. In
line with its structure, HRMS (ESI) revealed the parent ion
peak of 4 at m/z = 2666.2323 (calcd. for C126H35N12F50
1
[M – H]– 2666.2335). The H NMR spectrum of 4 showed
a broad singlet at δ = 8.11 ppm due to the outer NH groups,
eight signals in the range of δ = 7.70–7.56 ppm due to the
outer β-protons, two signals at δ = 4.77 and 4.60 ppm due
Scheme 2. Synthesis of 3.
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1,4-Phenylene-Bridged Hexaphyrin Dimers
Figure 2. UV/Vis/NIR absorption spectra of 1, 2, 3 and 4 in
CH2Cl2.
to the inner NH groups, four signals due to the inner β-
protons in the range of δ = 2.90–2.42 ppm and a singlet at
δ = 7.42 ppm due to the 1,4-phenylene unit. On the basis
of the detailed 1H NMR spectroscopy of 2,[6b] this spectrum
was interpreted in terms of the presence of a planar con-
former (antiaromatic) and several Möbius twisted conform-
ers (aromatic) that equilibrate faster than the 1H NMR
spectroscopic timescale. An increase in temperature led to
Scheme 4. Rhodium(I) metalation of 4 to give 9LL-meso, 9LL-dl,
and 9SL. meso-Pentafluorophenyl substituents are omitted for clar-
ity.
downfield shifts of the signals of the inner β-protons and almost perpendicular to each other, and the rhodium atoms
NH protons, indicating that the twisted Möbius aromatic are all coordinated to the interior side of the dimer. Consis-
1
conformers are more stable than the planar antiaromatic tent with the crystal structure, the H NMR spectrum of
conformer. The UV/Vis/NIR absorption spectrum of 4 ex- 10LL-dl exhibits eight doublets due to the outer β-protons
hibited a Soret-like band at 594 nm and Q-like bands at 771 in the range of δ = 9.99–9.22 ppm and four doublets due to
and 885 nm, which are similar to those of 2 (Figure 2). the inner β-protons in the range of δ = –3.28 to –3.48 ppm.
These features indicate a diatropic ring current for 4, proba- Importantly, the 1,4-phenylene protons were observed as
1
bly due to the preference of the twisted Möbius aromatic two singlets at δ = 11.34 and 8.93 ppm in the H NMR
conformers for [28]hexaphyrin segments similar to 2.
spectrum measured at –60 °C. The structural assignments
Next, we examined the RhI metalation of 4[3c,14] with the of 10LL-meso and 10SL are straightforward as the former
hope of separating each isomer as a stable conformer. [28]- exhibits four doublet signals due to the inner β-protons in
Hexaphyrin dimer
4 was treated with 20 equiv. of the range of δ = –3.20 to –3.48 ppm, and the latter exhibits
[RhCl(CO)2]2 and 10 equiv. of NaOAc in a mixture of eight doublets due to the inner β-protons in the range of δ
CH2Cl2 and methanol for 1 h to give RhI complexes 9LL- = –3.27 to –3.54 ppm. In accord with the structure, the sig-
meso and 9LL-dl in 35 and 16% yield, respectively nals due to the 1,4-phenylene units of 10LL-meso were ob-
(Scheme 4). When the same metalation was conducted in served as two doublets at –60 °C (see Supporting Infor-
CH2Cl2 without NaOAc for 12 h, 9SL was obtained in 4% mation). The UV/Vis/NIR spectra of 10LL-meso, 10LL-dl
yield in addition to 9LL-meso (31%) and 9LL-dl (14%). and 10SL display distinct Soret-like bands and Q-like
Importantly, 9LL-meso, 9LL-dl and 9SL were all conforma- bands, which reflect their aromatic characters (Figure 4b).
tionally stable and isolated as pure conformers by separa-
The structural assignments of 9LL-meso, 9LL-dl and
tion with a silica gel column. HRMS (ESI) revealed the 9SL were accomplished on the basis of the established
1
parent ion peaks of 9LL-meso, 9LL-dl and 9SL at m/z = chemical connection. The H NMR spectra of 9LL-meso
1648.3874, which is consistent with their structures (calcd. and 9LL-dl showed four doublet signals due to the inner β-
for C134H30N12F50O8Rh4 [M – 2 H]2– 1648.3876, see Sup- protons at an extremely low field of δ = 18.52–17.36 ppm
porting Information).
and eight signals due to the outer β-protons at a high field
The RhI complexes 9LL-meso, 9LL-dl and 9SL were all of δ = 4.82–3.32 ppm, indicating their distinct paratropic
quantitatively oxidized with MnO2 to the corresponding ring currents. The 1H NMR spectrum of 9SL displays eight
[26]hexaphyrin dimer RhI complexes 10LL-meso, 10LL-dl doublets due to the inner β-protons in the range of δ =
and 10SL without any detectable isomerization. Fortu- 18.52–16.18 ppm in line with its low-symmetry structure.
1
nately, we obtained crystals of 10LL-dl by the slow dif- These H NMR spectroscopic data indicate the antiarom-
fusion of heptane into its solution in toluene. As shown in atic character of 9LL-meso, 9LL-dl and 9SL. In line with
Figure 3, the structure of 10LL-dl was confirmed as one these assignments, the UV/Vis/NIR spectra of 9LL-meso,
conformer of the caterpillar-like isomerization,[13] in which 9LL-dl and 9SL exhibit ill-defined Soret-like bands at
the 1,4-phenylene bridge is connected to both long sides 586 nm and no Q-like bands. It is considered that RhI met-
of the hexaphyrins. Curiously, the two hexaphyrin rings are alation helps to maintain the planar conformation of the
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1915

H. Mori, N. Aratani, A. Osuka
FULL PAPER
[28]hexaphyrin moieties, hence realizing the antiaromatic
character. Lastly, it is interesting to note that these RhI
complexes of [28]hexaphyrins constitute rare examples of
dimeric Hückel antiaromatic molecules.
Conclusions
1,4-Phenylene-bridged [26]hexaphyrin dimer 3 was syn-
thesized by the condensation of 1,4-phenylene-bridged
tetrapyrrole carbinol 7 with tetrapyrromethane 8. 1H NMR
spectroscopy revealed that 3 and its reduced congener 4 ex-
ist as mixtures of conformational isomers in solution. Such
conformational dynamics were frozen for their RhI com-
plexes 9 and 10, and the conformational isomers of 9 and
10 were separated. Dimeric [28]hexaphyrin RhI complexes 9
constitute rare examples of covalently linked, antiaromatic
porphyrinoid dimers. This synthetic protocol is versatile
and promising for the construction of various expanded
porphyrin oligomers. The exploration of more conjugated
expanded porphyrin oligomers with this protocol are being
actively pursued in our laboratory.
Experimental Section
General: 1H and 19F NMR spectra were recorded with a JEOL
ECA-600 spectrometer (600 MHz for 1H and 565 MHz for 19F).
Chemical shifts are reported in ppm relative to the residual solvent
(CDCl3) as the internal reference for 1H NMR spectra (δ =
7.260 ppm), and hexafluorobenzene was used as the external refer-
ence for 19F NMR spectra (δ = –162.9 ppm). NMR spectra were
assigned from the 1H-1H COSY spectra and by comparison with
spectra in the presence of D2O (signals assigned to NH protons
disappear in the presence of D2O). UV/Vis spectra were recorded
with a Shimadzu UV-3100PC spectrometer. HRMS (ESI-TOF) in
acetonitrile were recorded with a Bruker microTOF instrument in
the positive or negative ion mode. X-ray data were recorded with
a Rigaku-Raxis imaging-plate system. Unless otherwise noted, ma-
terials obtained from commercial suppliers were used without fur-
ther purification. Silica gel column chromatography was performed
with Wakogel C-300 and C-400. TLC was carried out with alumi-
num sheets coated with silica gel 60 F254 (Merck 5554).
Figure 3. X-ray crystal structure of 10LL-dl. (a) Top and (b) side
view. The thermal ellipsoids are shown at 30% probability. meso-
Pentafluorophenyl groups and solvent molecules are omitted for
clarity.
1,4-Bis[1Ј,9Ј-bis(pentafluorobenzoyl)dipyrromethyl]benzene (6): To a
suspension of 1,4-bis(dipyrromethyl)benzene (5) (1.00 g,
2.73 mmol) in dry toluene (40 mL) was added a solution of
PhMgBr in tetrahydrofuran (THF) (16.4 mmol, 1.1 m) at 0 °C. Af-
ter 15 min, pentafluorobenzoyl chloride (1.57 mL, 10.9 mmol) was
added slowly to the reaction mixture, and the resulting solution
was stirred for an additional 15 min. The slow addition of PhMgBr
(16.4 mmol, 1.1 m) and the aroyl chloride (1.57 mL, 10.9 mmol)
was repeated over 30 min. After stirring for 15 min, the reaction
was quenched by the addition of saturated aqueous NH4Cl solu-
tion (100 mL). The product was extracted with ethyl acetate. The
combined organic extracts were washed with water and dried with
anhydrous Na2SO4. After the solvent was removed, precipitation
from CH2Cl2 afforded the crude product, which was purified by
recrystallization from AcOEt/CH2Cl2 to give 6 (2.47 g, 79%) as a
red powder. 1H NMR (600 MHz, [D6]DMSO, 298 K): δ = 12.58
(br. s, 4 H, NH), 7.23 (s, 4 H, phenylene-H), 6.84 (br. s, 4 H, β-H),
6.07 (d, J = 3.7 Hz, 4 H, β-H), 5.71 (s, 2 H, meso-H) ppm. 19F
NMR (565 MHz, CDCl3, 298 K): δ = –142.43 (d, J = 22.0 Hz, 8
Figure 4. UV/Vis/NIR spectra of (a) 9LL-meso, 9LL-dl and 9SL
and (b) 10LL-meso, 10LL-dl and 10SL in CH2Cl2.
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1,4-Phenylene-Bridged Hexaphyrin Dimers
F, o-F), –152.98 (t, J = 22.0 Hz, 4 F, p-F), and –160.78 (dt, J1
7.3 Hz, J2 = 22.0 Hz, 8 F, m-F) ppm.
=
Tetrakis(dicarbonylrhodium) complexes of [28]Hexaphyrin Dimer
(9SS, 9SL and 9LL). Method A: [28]Hexaphyrin dimer 4 (21.0 mg,
7.9 μmol) was dissolved in a 9:1 mixture of dichloromethane/meth-
anol (10 mL) in a round-bottomed flask. To this were added so-
dium acetate (6.4 mg, 10.0 equiv.) and [RhCl(CO)2]2 (60.7 mg,
20.0 equiv.), and the reaction mixture was stirred under nitrogen
for 1 h. The mixture was passed through a short Florisil column to
remove the rhodium salts followed by evaporation of the solvent
under reduced pressure. Repeated silica gel column chromatog-
raphy gave 9LL-dl (8.9 mg, 35%) and 9LL-meso (4.2 mg, 16%) as
the first and second violet fractions, respectively. Method B: [28]-
Hexaphyrin dimer 4 (70.6 mg, 25.5 μmol) was dissolved in di-
chloromethane (35 mL) in a round-bottomed flask. To this was
added [RhCl(CO)2]2 (198.6 mg, 20.0 equiv.), and the reaction mix-
ture was stirred under nitrogen for 12 h. The mixture was passed
through a short Florisil column to remove the rhodium salts fol-
lowed by evaporation of the solvent under reduced pressure. Re-
peated silica gel column chromatography gave 9SL (4.0 mg, 4%) as
the third fraction in addition to 9LL-dl (25.4 mg, 31%) and 9LL-
meso (12.2 mg, 14%).
1,4-Phenylene-Bridged [26]Hexaphyrin Dimer (3SS): Bis(dipyrro-
methane) 6 (600 mg, 0.53 mmol) was reduced with excess NaBH4
in a 9:1 mixture of THF/methanol (50 mL). After 30 min, the reac-
tion was quenched by the addition of saturated aqueous NH4Cl
solution (50 mL), and the organic layer was separated, washed with
water and dried with anhydrous Na2SO4. The solvent was removed
under reduced pressure to yield tetracarbinol 7 in a quantitative
yield. This compound was found to be unstable at ambient tem-
perature and hence was used immediately. Tetracarbinol 7 was dis-
solved in a solution of tetrapyrromethane 8 (930 mg, 2.2 equiv.) in
dry CH2Cl2 (50 mL). After the solution was stirred in the absence
of light under an inert gas for 15 min, p-toluenesulfonic acid
(20 mg, 0.11 mmol) was added, and stirring was continued for
120 min. DDQ (950 mg, 8.0 equiv.) was added, and the resulting
solution was stirred for a further 60 min. The reaction mixture was
passed through a basic alumina column to remove the tar products
followed by evaporation of the solvent under reduced pressure. The
residue was purified by silica gel chromatography using a 1:1 to 3:1
mixture of hexane/dichloromethane. Recrystallization from chloro-
9LL-dl: 1H NMR (600 MHz, CDCl3, 298 K): δ = 17.82 (d, J =
5.0 Hz, 2 H, inner β-H), 17.76 (d, J = 5.3 Hz, 2 H, inner β-H),
benzene and nonane provided 3SS (95 mg, 7%) as deep green crys-
1
tals. H NMR (600 MHz, CDCl3, 298 K): δ = 9.60 (d, J = 4.6 Hz, 17.46 (d, J = 5.0 Hz, 2 H, inner β-H), 17.36 (d, J = 5.3 Hz, 2 H,
4 H, outer β-H), 9.50 (d, J = 4.6 Hz, 4 H, outer β-H), 9.41 (d, J =
inner β-H), 5.74 (br. s, 4 H, phenylene-H), 4.82 (d, J = 4.5 Hz, 2
4.6 Hz, 4 H, outer β-H), 9.04 (d, J = 4.6 Hz, 4 H, outer β-H), 8.97 H, outer β-H), 4.75 (m, 6 H, outer β-H), 3.74 (d, J = 4.5 Hz, 2 H,
(s, 4 H, phenylene-H), –1.23 (br. s, 2 H, inner NH), –1.89 (br. s, 2
outer β-H), 3.65 (d, J = 4.5 Hz, 2 H, outer β-H), 3.60 (d, J =
4.5 Hz, 2 H, outer β-H), 3.57 (d, J = 4.5 Hz, 2 H, outer β-H), 3.47
H, inner NH),–2.07 (d, J = 4.6 Hz, 4 H, inner β-H), and –2.09 (d,
J = 4.6 Hz, 4 H, inner β-H) ppm. 19F NMR (565 MHz, CDCl3, (br. s, 2 H, outer NH), 2.95 (br. s, 2 H, outer NH) ppm. 19F NMR
298 K): δ = –136.31 (dd, J1 = 7.3 Hz, J2 = 22.0 Hz, 4 F, o-F),
–136.80 (d, J = 22.0 Hz, 8 F, o-F), –136.94 (d, J = 22.0 Hz, 8 F, o-
F), –150.08 (t, J = 22.0 Hz, 2 F, p-F), –152.57 (t, J = 22.0 Hz, 4 F,
(565 MHz, CDCl3, 298 K): δ = –131.90 (br. s, 2 F, o-F), –132.07
(br. s, 2 F, o-F), –132.33 (br. s, 2 F, o-F), –136.03 (br. s, 2 F, o-F),
–137.06 (br. s, 4 F, o-F), –139.25 (d, J = 18.4 Hz, 2 F, o-F), –139.47
p-F), –152.99 (t, J = 22.0 Hz, 4 F, p-F), –160.39 (t, J = 22.0 Hz, 4 (d, J = 22.0 Hz, 2 F, o-F), –139.59 (d, J = 18.4 Hz, 2 F, o-F),
F, m-F), –162.94 (m, 16 F, m-F) ppm. UV/Vis (CH2Cl2): λmax (ε) = –139.74 (d, J = 22.0 Hz, 2 F, o-F), –151.46 (br. s, 2 F, p-F), –151.92
569 (404000), 723 (64000), 788 (34600), 905 (17200), 1031
(19200 m–1 cm–1) nm. HRMS (ESI-TOF negative mode): calcd. for
C126H31N12F50 [M – H]– 2662.2022; found 2662.1943. Crystallo-
graphic data for 3SS: C126H32F50N12·(PhCl)5.8·(nonane)0.4 (Mr =
(m, 4 F, p-F), –152.53 (t, J = 22.0 Hz, 2 F, p-F), –152.71 (t, J =
22.0 Hz, 2 F, p-F), –157.92 (br. s, 2 F, m-F), –158.97 (br. s, 4 F, m-
F), –159.85 (m, 4 F, m-F), –160.00 (m, 2 F, m-F), –160.16 (m, 2 F,
m-F), –160.79 (br. s, 2 F, m-F), –161.22 (m, 2 F, m-F), –161.36 (m,
2 F, m-F) ppm. UV/Vis (CH2Cl2): λmax (normalized) = 361 (0.324),
538 (1.000), 597 (0.930), 680 (0.343) nm. HRMS (ESI-TOF positive
¯
3358.65), triclinic, space group P1 (No. 2), a = 15.0545(3), b =
16.1666(3), c = 30.2790(6) Å, α = 82.5552(8), β = 101.3326(8), γ =
100.9687(8)°, V = 7148.2(2) Å3, Z = 2, ρcalcd. = 1.560 gcm–3, T = mode): calcd. for C134H30N12F50O8Rh4 [M – 2 H]2– 1648.3876;
93(2) K, R1 = 0.1017 [IϾ2σ(I)], Rw = 0.3380 (all data), GOF =
found 1648.3874.
1.045.
1
9LL-meso: H NMR (600 MHz, CDCl3, 298 K): δ = 18.42 (d, J =
1,4-Phenylene-Bridged [28]Hexaphyrin Dimer (4): To a solution of
3 in a 9:1 mixture of dichloromethane/methanol was added excess
NaBH4, and the mixture was stirred for 30 min. The reaction was
quenched with saturated aqueous NH4Cl solution, and the organic
layer was separated, washed with water and dried with anhydrous
Na2SO4. The solvent was removed under reduced pressure to give
4.1 Hz, 2 H, inner β-H), 18.31 (d, J = 4.1 Hz, 2 H, inner β-H),
18.11 (d, J = 4.1 Hz, 2 H, inner β-H), 17.95 (d, J = 4.1 Hz, 2 H,
inner β-H), 5.60 (s, 4 H, phenylene-H), 4.60 (d, J = 4.8 Hz, 2 H,
outer β-H), 4.55 (d, J = 4.8 Hz, 2 H, outer β-H), 4.54 (d, J =
4.8 Hz, 2 H, outer β-H), 4.51 (d, J = 4.8 Hz, 2 H, outer β-H), 3.51
(d, J = 4.8 Hz, 2 H, outer β-H), 3.44 (d, J = 4.8 Hz, 2 H, outer β-
H), 3.37 (d, J = 4.8 Hz, 2 H, outer β-H), 3.32 (d, J = 4.8 Hz, 2 H,
outer β-H), 2.75 (br. s, 2 H, outer NH), 2.62 (br. s, 2 H, outer NH)
ppm. 19F NMR (565 MHz, CDCl3, 298 K): δ = –131.61 (br. s, 2 F,
o-F), –131.92 (d, J = 25.6 Hz, 2 F, o-F), –132.23 (d, J = 25.6 Hz,
1
4 in a quantitative yield. H NMR (600 MHz, CDCl3, 298 K): δ =
8.11 (br. s, 4 H, outer NH), 7.70 (m, 6 H, outer β-H), 7.63 (m, 4
H, outer β-H), 7.59 (d, J = 4.6 Hz, 2 H, outer β-H), 7.56 (m, 4 H,
outer β-H), 7.42 (br. s, 4 H, phenylene-H), 4.77 (br. s, 2 H, inner
NH), 4.60 (br. s, 2 H, inner NH), 2.90 (br. s, 4 H, inner β-H), 2.46 2 F, o-F), –136.05 (br. s, 2 F, o-F), –136.96 (m, 2 F, o-F), –137.15
(br. s, 2 H, inner β-H), and 2.42 (d, 2 H, inner β-H) ppm. 19F NMR
(565 MHz, CDCl3, 298 K): δ = –137.33 (m, 4 F, o-F), –137.43 (m,
(m, 2 F, o-F), –139.56 (m, 4 F, o-F), –139.86 (d, J = 25.6 Hz, 2 F,
o-F), –140.32 (d, J = 18.4 Hz, 2 F, o-F), –151.85 (t, J = 22.0 Hz, 2
4 F, o-F), –137.62 (m, 12 F, o-F), –150.93 (t, J = 22.0 Hz, 2 F, o- F, p-F), –151.97 (t, J = 22.0 Hz, 2 F, o-F), –152.66 (t, J = 22.0 Hz,
F), –151.23 (m, 4 F, p-F), –152.72 (t, J = 22.0 Hz, 2 F, p-F), –152.93
(t, J = 22.0 Hz, 2 F, p-F), –160.21 (m, 10 F, m-F), –150.93 (m, 10
2 F, p-F), –152.77 (t, J = 22.0 Hz, 2 F, p-F), –154.68 (br. s, 2 F, p-
F), –158.62 (br. s, 2 F, m-F), –158.83 (br. s, 2 F, m-F), –158.96 (br.
F, m-F) ppm. UV/Vis (CH2Cl2): λmax (ε) = 312 (77900), 395 s, 2 F, m-F), 159.84 (dt, J1 = 7.3 Hz, J2 = 25.6 Hz, 2 F, m-F), 160.01
(83100), 594 (341000), 771 (40500), 895 (29300 m–1 cm–1) nm.
HRMS (ESI-TOF negative mode): calcd. for C126H35N12F50 [M –
H]– 2666.2335; found 2666.2323.
(dt, J1 = 7.3 Hz, J2 = 25.6 Hz, 2 F, m-F), 160.13 (dt, J1 = 7.3 Hz,
J2 = 25.6 Hz, 2 F, m-F), –160.70 (m, 4 F, m-F), –161.17 (br. s, 2
F, m-F), –161.37 (br. s, 2 F, m-F) ppm. UV/Vis (CH2Cl2): λmax
Eur. J. Org. Chem. 2012, 1913–1919
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1917

H. Mori, N. Aratani, A. Osuka
FULL PAPER
(normalized) = 359 (0.353), 541 (1.000), 598 (0.976), 695 (0.327)
nm.
(d, J = 4.1 Hz, 2 H, outer β-H), 9.74 (d, J = 4.6 Hz, 2 H, outer β-
H), 9.25 (d, J = 4.1 Hz, 2 H, outer β-H), 9.22 (d, J = 4.6 Hz, 2 H,
outer β-H), 9.20 (d, J = 4.6 Hz, 2 H, outer β-H), 9.08 (d, J =
5.0 Hz, 2 H, outer β-H), –3.20 (d, J = 4.1 Hz, 2 H, inner β-H),
–3.30 (d, J = 4.1 Hz, 2 H, inner β-H), –3.43 (d, J = 4.1 Hz, 2 H,
inner β-H), –3.48 (d, J = 4.1 Hz, 2 H, inner β-H) ppm; the signals
due to phenylene-H were observed at –60 °C: δ = 11.34 (d, J =
6.4 Hz, 2 H), 8.93 (d, J = 6.4 Hz, 2 H) ppm. 19F NMR (565 MHz,
CDCl3, 298 K): δ = –133.41 (br. s, 4 F, o-F), –133.79 (br. s, 2 F, o-
F), –134.57 (d, J = 22.0 Hz, 2 F, o-F), –134.86 (d, J = 22.0 Hz, 2
F, o-F), –136.93 (m, 4 F, o-F), –140.51 (d, J = 22.0 Hz, 2 F, o-F),
–140.68 (m, 4 F, o-F), –150.07 (t, J = 22.0 Hz, 4 F, p-F), –150.89
(t, J = 22.0 Hz, 2 F, p-F), –150.99 (t, J = 22.0 Hz, 2 F, p-F), –151.19
(t, J = 22.0 Hz, 2 F, p-F), –160.52 (m, 8 F, m-F), –161.80 (m, 6 F,
p-F), –162.96 (m, 4 F, m-F), –163.30 (br. s, 2 F, o-F) ppm. UV/Vis
(CH2Cl2): λmax (ε) = 353 (90800), 587 (308000), 760 (45500), 864
(80400 m–1 cm–1) nm. Crystallographic data for 10LL-dl:
C134H28F50N12O8Rh4·(toluene)1.55·(heptane)2.68 (Mr = 4006.16),
monoclinic, space group C2/c (No. 15), a = 53.7715(10), b =
11.9675(2), c = 32.5977(6) Å, β = 121.3850(7)° V = 17908.6(6) Å3,
Z = 4, ρcalcd. = 1.486 gcm–3, T = 93(2) K, R1 = 0.0760 [IϾ2σ(I)],
Rw = 0.2270 (all data), GOF = 0.999.
1
9SL: H NMR (600 MHz, CDCl3, 298 K): δ = 18.52 (s, 2 H, inner
β-H), 18.35 (d, J = 5.5 Hz, 1 H, inner β-H), 18.28 (d, J = 5.5 Hz,
1 H, inner β-H), 16.30 (d, J = 5.5 Hz, 1 H, inner β-H), 16.28 (d, J
= 5.5 Hz, 1 H, inner β-H), 16.18 (m, 2 H, inner β-H), 6.12 (br. s,
1 H, phenylene-H), 5.80 (br. s, 1 H, phenylene-H), 5.74 (d, J =
8.3 Hz, 2 H, phenylene-H), 5.00 (d, J = 4.5 Hz, 2 H, outer β-H),
4.67 (d, J = 4.8 Hz, 1 H, outer β-H), 4.58 (m, 4 H, outer β-H),
4.46 (d, J = 4.8 Hz, 1 H, outer β-H), 4.00 (d, J = 4.5 Hz, 2 H,
outer β-H), 3.84 (m, 2 H, outer β-H), 3.50 (br. s, 2 H, outer NH),
3.45 (d, J = 4.5 Hz, 1 H, outer β-H), 3.43 (d, J = 4.5 Hz, 1 H,
outer β-H), 3.41 (d, J = 4.5 Hz, 1 H, outer β-H), 3.32 (d, J =
4.5 Hz, 1 H, outer β-H), 2.94 (br. s, 1 H, outer NH), 2.64 (br. s, 1
H, outer NH) ppm. 19F NMR (565 MHz, CDCl3, 298 K): δ =
–131.62 (d, J = 18.4 Hz, 1 F, o-F), –131.83 (d, J = 18.4 Hz, 1 F, o-
F), –132.05 (d, J = 18.4 Hz, 1 F, o-F), –132.52 (m, 4 F, o-F),
–136.17 (br. s, 1 F, o-F), –136.84 (br. s, 4 F, o-F), –137.05 (br. s, 2
F, o-F), –139.41 (m, 3 F, o-F), –139.61 (d, J = 25.7 Hz, 1 F, o-F),
–139.83 (d, J = 25.7 Hz, 1 F, o-F), –140.10 (d, J = 25.7 Hz, 1 F, o-
F), –151.79 (m, 3 F, p-F), –151.98 (m, 3 F, p-F), –152.58 (m, 2 F,
p-F), –152.80 (m, 2 F, p-F), –158.58 (br. s, 1 F, m-F), –158.95 (br.
s, 3 F, m-F), –159.09 (br. s, 1 F, m-F), –159.45 (br. s, 1 F, m-F),
–159.97 (m, 6 F, m-F), –160.93 (br. s, 1 F, m-F), –161.23 (br. s, 7
F, m-F) ppm. UV/Vis (CH2Cl2): λmax (normalized) = 350 (0.290),
524 (0.951), 586 (1.000), 680 (0.179) nm.
1
10SL: H NMR (600 MHz, CDCl3, 298 K): δ = 10.09 (br. s, 1 H,
outer β-H), 10.02 (d, J = 4.5 Hz, 1 H, outer β-H), 9.91 (m, 3 H,
outer β-H), 9.85 (d, J = 4.5 Hz, 1 H, outer β-H), 9.83 (d, J =
4.5 Hz, 1 H, outer β-H), 9.76 (m, 5 H, 3 outer β-H and 2 phenylene-
H), 9.32 (d, J = 4.5 Hz, 2 H, outer β-H), 9.30 (d, J = 4.5 Hz, 1 H,
outer β-H), 9.22 (d, J = 4.5 Hz, 1 H, outer β-H), 9.20 (d, J =
4.5 Hz, 2 H, outer β-H), 8.52 (br. s, 2 H, phenylene-H), –3.27 (d,
J = 3.8 Hz, 1 H, inner β-H), –3.30 (d, J = 4.1 Hz, 1 H, inner β-H),
–3.31 (d, J = 3.8 Hz, 1 H, inner β-H), –3.35 (d, J = 4.1 Hz, 1 H,
inner β-H), –3.37 (d, J = 3.8 Hz, 1 H, inner β-H), –3.38 (d, J =
3.8 Hz, 1 H, inner β-H), –3.50 (d, J = 4.1 Hz, 1 H, inner β-H),
–3.54 (d, J = 4.1 Hz, 1 H, inner β-H) ppm. 19F NMR (565 MHz,
CDCl3, 298 K): δ = –133.49 (br. s, 5 F, o-F), –133.71 (d, J =
25.7 Hz, 1 F, o-F), –134.54 (d, J = 22.0 Hz, 1 F, o-F), –134.62 (d,
J = 22.0 Hz, 1 F, o-F), –134.75 (d, J = 25.7 Hz, 1 F, o-F), –136.84
(m, 2 F, o-F), –136.94 (d, J = 22.0 Hz, 1 F, o-F), –140.40 (d, J =
22.0 Hz, 1 F, o-F), –140.59 (m, 7 F, o-F), –149.76 (t, J = 22.0 Hz,
1 F, p-F), –149.86 (t, J = 22.0 Hz, 1 F, p-F), –150.05 (t, J = 22.0 Hz,
1 F, p-F), –150.33 (br. s, 1 F, p-F), –150.53 (m, 2 F, p-F), –150.70
(t, J = 22.0 Hz, 1 F, p-F), –150.80 (t, J = 22.0 Hz, 1 F, p-F), –151.03
(m, 2 F, p-F), –160.27 (dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 1 F, m-F),
–160.49 (m, 5 F, m-F), –161.05 (dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 2 F,
m-F), –161.69 (dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 2 F, m-F), –161.83
(m, 3 F, m-F), –162.08 (dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 1 F, m-F),
–162.53 (br. s, 1 F, m-F), –163.03 (m, 3 F, m-F), –163.24 (br. s, 2
F, m-F) ppm. UV/Vis (CH2Cl2): λmax (ε) = 354 (76100), 614
(412000), 762 (47800), and 837 (59800 m–1 cm–1) nm.
Tetrakis(rhodiumdicarbonyl) Complexes of [26]Hexaphyrin Dimers
(10SS, 10SL and 10LL): MnO2 (26.0 mg, 0.30 mmol) was added
to a solution of 9LL-meso, 9LL-dl or 9SL (10.0 mg, 3.0 μmol) in
dichloromethane (10 mL). An immediate colour change from dark
purple to light blue was observed. Stirring was continued for
15 min, and the solution was passed through Celite. The solvent
was evaporated under reduced pressure, and the residue was passed
through a short silica gel column with dichloromethane as an elu-
ent. Concentration of the vivid blue fraction to dryness yielded
10LL-meso, 10LL-dl or 10SL in quantitative yields. Crystals were
obtained by slow diffusion of heptane into a solution of 10LL-dl
in toluene.
10LL-dl: 1H NMR (600 MHz, CDCl3, 298 K): δ = 9.99 (d, J =
4.1 Hz, 2 H, outer β-H), 9.98 (d, J = 4.6 Hz, 2 H, outer β-H), 9.89
(d, J = 4.1 Hz, 2 H, outer β-H), 9.75 (d, J = 4.1 Hz, 2 H, outer β-
H), 9.46 (d, J = 4.1 Hz, 2 H, outer β-H), 9.34 (m, 4 H, outer β-H),
9.22 (d, J = 4.6 Hz, 2 H, outer β-H), –3.28 (d, J = 4.1 Hz, 2 H,
inner β-H), –3.31 (d, J = 4.1 Hz, 2 H, inner β-H), –3.46 (d, J =
4.1 Hz, 2 H, inner β-H), and –3.48 (d, J = 4.1 Hz, 2 H, inner β-H)
ppm; the signals due to phenylene-H were observed at –60 °C: δ =
12.01 (s, 2 H), 8.78 (s, 2 H) ppm. 19F NMR (565 MHz, CDCl3,
298 K): δ = –133.23 (d, J = 22.0 Hz, 2 F, o-F), –133.38 (br. s, 4 F,
o-F), –134.55 (d, J = 22.0 Hz, 2 F, o-F), –134.73 (br. s, 2 F, o-F),
–136.65 (d, J = 22.0 Hz, 2 F, o-F), –136.93 (d, J = 22.0 Hz, 2 F, o-
F), –140. 25 (d, J = 22.0 Hz, 2 F, o-F), –140.57 (d, J = 22.0 Hz, 2
F, o-F), –140.70 (d, J = 22.0 Hz, 2 F, o-F), –149.97 (m, 4 F, p-F),
–150.88 (br. s, 4 F, p-F), –151.03 (t, J = 22.0 Hz, 2 F, p-F), –160.27
(dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 2 F, m-F), –160.50 (m, 4 F, m-F),
–161.07 (dt, J1 = 7.3 Hz, J2 = 22.0 Hz, 2 F, m-F), –161.21 (dt, J1
= 7.3 Hz, J2 = 22.0 Hz, 2 F, m-F), –161.48 (dt, J1 = 7.3 Hz, J2 =
22.0 Hz, 2 F, m-F), –161.83 (m, 4 F, m-F), –162.93 (br. s, 2 F, m-
F), –163.32 (br. s, 2 F, m-F) ppm. UV/Vis (CH2Cl2): λmax (ε) =
353 (88400), 584 (306000), 760 (44700), 861 (80900 m–1 cm–1) nm.
HRMS (ESI-TOF positive mode): calcd. for C134H29N12F50O8Rh4
[M + H]+ 3295.7679; found 3295.7674.
CCDC-859719 (for 3SS) and -859720 (for 10LL-dl) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): 1H and 19F NMR spectra, HRMS (ESI-TOF), crystallo-
graphic data.
Acknowledgments
This work was supported by Grants-in-Aids for Scientific Research
from Ministry of Education, Culture, Sports, Science and Technol-
1
10LL-meso: H NMR (600 MHz, CDCl3, 298 K): δ = 9.88 (d, J =
5.0 Hz, 2 H, outer β-H), 9.81 (d, J = 4.6 Hz, 2 H, outer β-H), 9.80 ogy (MEXT), Japan [No. 22245006 (A) and 20108001 (“pi-Space”)].
1918
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Eur. J. Org. Chem. 2012, 1913–1919

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Received: January 24, 2012
Published Online: February 21, 2012
Eur. J. Org. Chem. 2012, 1913–1919
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1919