Two-dimensionally extended porphyrin tapes: Synthesis and shape-dependent two-photon absorption properties

Article abstract of DOI:10.1002/chem.200800776

We report the synthesis and characterization of L- and T-shaped porphyrin tapes as extensible structural motifs of two-dimensionally extended porphyrin tapes. The two-photon absorption (TPA) cross-section values (σ ⁽²⁾ for L- and T-shaped porphyrin tapes as well as those for linear trimeric and tetrameric porphyrin tapes were measured by an open-aperture Z-scan method at 2300 nm, a wavelength at which the one-photon absorption contribution is either zero or almost negligible. Under these conditions, the σ⁽²⁾ values for the linear porphyrin tape trimer and tetramer were determined to be 18500 and 41200 GM, respectively. The σ ⁽²⁾ value for the L-shaped trimer was determined to be 8700 GM, which is only half that of the linear trimer, whereas the σ⁽²⁾ value for the Tshaped tetramer was measured to be 35700 GM. These results clearly indicate the dependence of the TPA crosssection on the molecular shape, which underscores the importance of directionality in the jt-conjugation pathway for the enhancement of TPA crosssection.

Full text of DOI:10.1002/chem.200800776

FULL PAPER
DOI: 10.1002/chem.200800776
Two-Dimensionally Extended Porphyrin Tapes:
Synthesis and Shape-Dependent Two-Photon Absorption Properties
Yasuyuki Nakamura,[a] So Young Jang,[b] Takayuki Tanaka,[a] Naoki Aratani,[a]
Jong Min Lim,[b] Kil Suk Kim,[b] Dongho Kim,*[b] and Atsuhiro Osuka*[a]
Abstract: We report the synthesis and
characterization of L- and T-shaped
porphyrin tapes as extensible structural
motifs of two-dimensionally extended
porphyrin tapes. The two-photon ab-
sorption (TPA) cross-section values
(s(2)) for L- and T-shaped porphyrin
tapes as well as those for linear trimer-
ic and tetrameric porphyrin tapes were
measured by an open-aperture Z-scan
method at 2300 nm, a wavelength at
which the one-photon absorption con-
tribution is either zero or almost negli-
gible. Under these conditions, the s(2)
values for the linear porphyrin tape
trimer and tetramer were determined
to be 18500 and 41200 GM, respective-
ly. The s(2) value for the L-shaped
trimer was determined to be 8700 GM,
which is only half that of the linear
trimer, whereas the s(2) value for the T-
shaped tetramer was measured to be
35700 GM. These results clearly indi-
cate the dependence of the TPA cross-
section on the molecular shape, which
underscores the importance of direc-
tionality in the p-conjugation pathway
for the enhancement of TPA cross-
section.
Keywords: aromaticity
· conjuga-
tion · nonlinear optics · porphyri-
noids · two-photon adsorption
Introduction
polarizability are the key factors that contribute to a large
TPA cross-section.[8–22] Recent efforts have been directed to-
wards enhancing this TPA property by using donor(D)/ac-
ceptor(A)-type multichromophore systems with a D–p–A
arrangement,[11] introducing additional groups to perturb the
charge redistribution, and elongating the effective p-conju-
gation length.[18] Alternatively, intramolecular face-to-face
p-conjugated systems lead to large s(2) values as a result of
favorable cofacial p electronic interactions.[19] Dendrimers[20]
and expanded porphyrins[21] have also been shown to be
promising molecular platforms for large TPA properties. Oc-
tupolar effects have also been reported to be advantageous
for large TPA cross-section values.[22] Despite these exten-
sive studies, the effects of structure on this TPA property
are not clearly understood.
Porphyrin has been shown to be a very versatile pigment
that gives large TPA properties by appropriate chemical
modification.[23–31] Although porphyrin monomers usually
exhibit only small TPA cross-sections (<100 GM),[23] this
TPA property has been enhanced by effective conjuga-
tion.[24–31] In this respect, meso–meso,b–b,b–b triply linked
porphyrin arrays (porphyrin tapes)[32–35] are particularly
promising because the arrays are fully conjugated electronic
systems, as seen in their extremely redshifted absorption
bands. They are also interesting in light of their flat and
rigid molecular shapes,[32] their ability to store multiple
Two-photon absorption (TPA) is one of the nonlinear opti-
cal (NLO) phenomena in which a chromophore is excited
by simultaneous absorption of two low-energy photons to a
level at which normal high-energy one-photon absorption is
required. This TPA property can be linked to numerous po-
tential applications, for example, 3D microfabrication,[1,2]
optical storage,[3,4] optical-limiting devices,[5,6] and photody-
namic therapy.[7] Hence, extensive studies have been carried
out to elucidate the molecular structure–property relation-
ships for TPA. From these studies it has been concluded
that extended p-electron conjugation and large molecular
[a] Y. Nakamura, T. Tanaka, Dr. N. Aratani, Prof. Dr. A. Osuka
Department of Chemistry, Graduate School of Science
Kyoto University
Sakyo-ku, Kyoto 606-8502 (Japan)
Fax : (+81)75-753-3970
E-mail: osuka@kuchem.kyoto-u.ac.jp
[b] S. Y. Jang, J. M. Lim, K. S. Kim, Prof. Dr. D. Kim
Center for Ultrafast Optical Characteristics Control and
Department of Chemistry
Yonsei University, Seoul 120-749 (Korea)
Fax : (+82)2-2123-2434
E-mail: dongho@yonsei.ac.kr
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200800776.
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charges,[33] and their electroni-
cally communicative guest bind-
ing.[34] In fact, the TPA cross-
section values (s(2)) of dimer 2,
trimer 3, and tetramer 4 have
been revealed to be exception-
ally large, 11900, 33100, and
93600 GM, respectively, in an
open aperture Z-scan measure-
ment using femtosecond laser
pulse excitation at 1200 nm
(Scheme 1).[36] However, note
that the large TPA values for 3
and
4 contain non-negligible
contributions from the one-
photon absorption at 1200 nm.
Thus, it is highly desirable to
measure TPA values free from
the contribution of the one-
photon absorption by shifting
Scheme 1. Structures of porphyrin 1 and porphyrin arrays 2–5. The 1H NMR chemical shifts (d/ppm) are re-
ported (underlined values).
the
two-photon
excitation
wavelength further into the IR
region in which porphyrin
arrays do not absorb.
Triply linked porphyrin tapes
are also attractive for a study of
the shape-dependence of TPA
cross-sections because two-di-
mensionally extended porphy-
rin tapes, such as L- and T-
shaped arrays, would give the
relevant useful information. So
Scheme 2. L- and T-shaped porphyrin tapes studied in this paper.
far, however, porphyrin tapes have been limited to linear
arrays and two-dimensionally extended porphyrin tapelike
conjugated porphyrin oligomers have rarely been studied
with the exception of tetrameric porphyrin sheet 5. This
square-shaped tetramer exhibits a paratropic ring current
above the central cyclooctatetraene (COT) segment and ex-
hibits a small s(2) value of 2750 GM in spite of its tetrapor-
phyrin construction.[37] These results clearly indicate the de-
pendence of the TPA cross-section on the molecular shape
and electronic nature of the p-electron system. Consequent-
ly, the study of other two-dimensionally extended porphyrin
tapelike oligomers is strongly desirable.
Results
Moleculardesign and synthesis : L- and T-shaped porphyrin
tapes can be regarded as the constructs of a core porphyrin
segment (CP) and side-porphyrin segments (SP) (Figure 1).
In this paper, we report the synthesis of L- and T-shaped
porphyrin tapes as two-dimensionally extended porphyrin
tapes (Scheme 2). The molecular shapes of these porphyrin
tapes are interesting from the viewpoint of connectors for
direction change or for the multiple connection of a molecu-
lar wire in a molecular circuit. We also report the TPA prop-
erties of the L- and T-shaped porphyrin tapes as well as
those of the linear porphyrin tape trimer 3 and tetramer 4
determined by excitation at 2300 nm, a wavelength at which
their real absorptions are zero or almost negligible.[38]
Figure 1. Schematic representation of the structures of the 2D triply
linked porphyrin oligomers.
We thus planned to synthesize these molecules by coupling
the respective segments and subsequent oxidative ring clo-
sure (ORC) to provide L- and T-shaped porphyrin tapes
bearing direct triple linkages.[39] In the molecular design of
these fused porphyrin arrays, it is important to avoid severe
steric interactions between the meso-R substituents on the
side-porphyrins in the bay area because these substituents
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Extended Porphyrin Tapes
FULL PAPER
Scheme 3. Synthesis of the side-porphyrins. Reagents: i) NBS, CHCl3; ii) 8, [Pd2
ACHTREUNG
ACHTREUNG
are forced into close proximity (Figure 1). To circumvent
these steric interactions, we chose relatively long alkyl sub-
stituents for the meso-R groups with the expectation that
their flexible conformations would help mitigate such inter-
actions and would also help improve their solubility.
Another key issue in the molecular design is to improve
the solubility of these porphyrin arrays. Based on our previ-
ous studies, meso–meso singly linked porphyrin oligomers
are expected to have good solubilities,[40–42] but fused por-
phyrin tapes with flat shapes should display only poor solu-
bilities, which will cause serious difficulties in manipulations
and poor reaction yields. This tendency would be worse for
two-dimensionally extended L- and T-shaped arrays. Fur-
thermore, the very poor solubility of meso-hexahexyl-substi-
tuted triply linked diporphyrin warns of seriously poor solu-
bility for L- and T-shaped porphyrin tapes with all-meso-
alkyl substituents.[43] Accordingly, we decided to employ
5,15-dinonyl-10-(4-dodecyloxyphenyl)porphyrin (10) and
5,15-dinonyl-10-(3,5-di-tert-butylphenyl)porphyrin (11) as
SPs and 5,10-bis(3,5-di-tert-butylphenyl)porphyrin (14)[44]
and 5-(3,5-di-tert-butylphenyl)porphyrin (17)[45] as CPs in
the synthesis of the L- and T-shaped porphyrin arrays, re-
spectively (Scheme 3).
Scheme 4. Synthesis of the core-porphyrins. Reagents: i) NBS, CHCl3;
ii) HBpin, [Pd(PPh3)2Cl2], Et3N, dichloroethane. Ar=3,5-di-tert-butyl-
A
phenyl, Bpin=4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl.
solubility and can be easily purified by silica gel column
chromatography. In the borylation reaction of 18, partially
debrominated bisborylated porphyrins (1:2 regioisomeric
1
mixture by H NMR spectroscopy analysis) were formed as
5,15-Dinonylporphyrin 6 was synthesized as the starting
byproducts.
compound for the synthesis of SP in 19% yield from bis
A
Cross-coupling between CP and SP was performed under
Suzuki–Miyaura reaction conditions (Scheme 5).[48] Namely,
compounds 16 and 12 (2.2 equiv) were heated at 1008C in
pyrryl)methane and decanal by using the acid-catalyzed con-
densation method of Lindsey et al.[46] Bromination of 6 with
N-bromosuccinimide (NBS) and subsequent Suzuki–
Miyaura cross-coupling with aryl boronates 8 and 9 gave tri-
substituted porphyrins 10 and 11, respectively. Bromination
of 10 and 11 with NBS afforded brominated SPs 12 and 13
in almost quantitative yields.
As synthetic precursors of the CP, multiply borylated por-
phyrins 16 and 19 were prepared from 14 and 17, respective-
ly, by a two-step conversion: bromination and borylation
(Scheme 4).[47] The bromination yields were 97 and 61% for
15 and 18, respectively, and the borylation yields were 88
and 64% for 16 and 19, respectively. Although brominated
porphyrins 15 and 18 are only poorly soluble in common or-
ganic solvents, borylated porphyrins 16 and 19 exhibit good
the presence of [Pd2(dba)3·CHCl3] (dba=dibenzylideneace-
A
tone), PPh3, Cs2CO3, and CsF for 12 h and subsequent sepa-
ration by GPC–HPLC gave trimer LHa in 57% yield. A
similar coupling reaction of 19 with 12 (3.3 equiv) afforded
tetramer THa in 62% yield. meso–meso linked oligomers
LHb and THb were similarly obtained by the coupling reac-
tion of 13 with 16 and 19, respectively, but the yields were
only moderate (36% for LHb and 20% for THb), probably
due to the lower solubility of 13. All-zinc-metalated oligo-
mers LZa, LZb, TZa, and TZb were prepared quantitatively
by the usual zinc metalation method. The synthesized oligo-
mers were fully characterized by mass spectrometry and
1H NMR spectroscopy (see the Supporting Information).
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A. Osuka, D. Kim et al.
Scheme 5. Synthesis of the L- and T-shaped-porphyrin arrays. Reagents: i) [Pd2
N
N
CHCl3; iii) DDQ, Sc
ACHTREUNG
Next, the ORC reactions of the L- and T-shaped meso–
meso linked porphyrin arrays were examined (Scheme 5).
Oxidation of LZa with 2,3-dichloro-5,6-dicyano-1,4-benzo-
1H NMR spectra: Porphyrin tapes have conjugated p-elec-
tron systems that are extensively delocalized over the whole
molecular array. These fully conjugated features are likely
to decrease the aromaticity in each porphyrin moiety, as
seen in the substantial upfield shifts of the peripheral b pro-
tons, which are increasingly eminent for longer porphyrin
tapes, as shown in Scheme 1. Namely, the b protons of the
porphyrin monomer 1 resonate at d=8.96 and 8.92 ppm,
which reflects a strong aromatic ring current, and the edge b
protons of dimer 2, trimer 3, and tetramer 4 resonate at d=
7.51, 7.53, and 7.45 ppm, respectively, whereas the inner pro-
tons resonate at a higher field.[49] These 1H NMR spectra
were recorded in CD2Cl2 in the presence of a small amount
of n-butylamine to suppress the aggregation of the porphy-
rin tapes by coordination of n-butylamine to the zinc ions of
quinone (DDQ) and Sc(OTf)3 (Tf=trifluoromethanesulfon-
A
yl) in toluene[32] and subsequent separation by alumina
column chromatography and recrystallization from CH2Cl2/
CH3CN gave triply linked L-shaped trimer FLZa in a high
yield of 89%. A similar ORC reaction of LZb gave FLZb in
77% yield. The MALDI-TOF mass spectra of the triply
linked porphyrin arrays showed the parent ion peaks at m/z
2511.2 for FLZa (calcd for C160H192N12O2Zn3: 2511.3) and at
m/z 2367.2 for FLZb (calcd for C152H176N12Zn3: 2367.2) (see
Figure S30 of the Supporting Information). The T-shaped
tetramers FTZa and FTZb were also obtained by the ORC
reaction of TZa and TZb in 85 and 75% yields, respectively.
Their mass spectra exhibit the parent ion peaks at m/z
3203.2 for FTZa (calcd for C202H242N16O3Zn4: 3203.8) and at
m/z 2987.7 for FTZb (calcd for C190H218N16Zn4: 2987.5).
Comparison of the weak but well-resolved isotope distribu-
tion patterns of TZb and FTZb clearly demonstrates the
loss of 12 hydrogen atoms from the corresponding meso–
meso linked porphyrin array compared with the porphyrin
tape (see Figure S32 of the Supporting Information). The
GPC chromatograms of the porphyrin tapes FLZa and
FTZa exhibit single peaks under high dilution conditions,
and their retention times are slightly but distinctly shorter
than those of the corresponding meso–meso singly linked
porphyrin arrays, which indicates that their hydrodynamic
volumes are smaller after the ORC reaction (see Fig-
1
the porphyrins. On the other hand, the H NMR spectrum
of the square planar porphyrin sheet 5 exhibits signals at d=
6.14 and 5.98 ppm for the outer b protons.[37] The unique
feature of 5 may be ascribed to its central COT segment,
which is forced to be planar because of the fused porphyrin
skeleton. This structure has been shown to produce a rather
strong paratropic ring current just above the COT core, as
evidenced by the downfield shifts of the guest protons coor-
dinated to 5.[37,50]
1
In this study, we examined the H NMR spectra of L- and
T-shaped porphyrin tapes in CD2Cl2/n-butylamine. Even
1
under these conditions, FLZa yielded a H NMR spectrum
with considerably broadened signals, probably due to its
strong stacking tendency. This porphyrin tape gives similar
broad 1H NMR spectra in CDCl3/n-butylamine and
ures S33 and S34 of the Supporting Information).
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Extended Porphyrin Tapes
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[D5]pyridine. Fortunately, we found that FLZb, which has
four bulky 3,5-di-tert-butylphenyl substituents, exhibits a
upon molecular shape. In this respect, the absorption spectra
of the L- and T-shaped porphyrin tapes are intriguing.
The absorption spectra of FLZa and FTZa were mea-
sured in toluene containing 5% (v/v) n-butylamine to sup-
press aggregation and hence improve their solubility (see
Figure 3 and the Supporting In-
1
sharp H NMR spectrum in CD2Cl2/n-butylamine. Signal as-
1
signment was based on comprehensive H–1H COSY experi-
ments and by comparison with those of related porphyrins
formation). However, as judged
1
from the broad H NMR spec-
tra, these two porphyrin tapes
are considered not to escape
aggregation. Without n-butyl-
amine, the absorption spectra
of FLZa in various solvents
show a broader structure, which
indicates a slight solvent de-
pendency. On the other hand,
upon addition of 5% n-butyl-
Figure 2. 1H NMR spectrum of FLZb in CD2Cl2 containing 1% (v/v) n-butylamine.
(Figure 2). Three singlet peaks observed at d=7.76, 6.73,
and 6.71 ppm were assigned to 1-H, and 2-H or 3-H, respec-
tively, because these chemical shifts are similar to those of
3. The singlet at d=8.20 ppm was assigned to 8-H, which is
additionally influenced by the ring current of the diagonal
porphyrin thereby undergoing a further downfield shift. Two
sets of mutually coupled doublet peaks at d=8.24 and
8.15 ppm and at d=7.64 and 7.63 ppm have been assigned
to 4-H or 7-H and 5-H or 6-H, respectively. Overall, the
1H NMR spectrum of FLZb indicates that its ring current
effect is not so very different to that of 3, which suggests
that the aromaticity of the constituent porphyrins is not
strongly perturbed by the L shape of triply linked porphyrin
arrays.
The 1H NMR spectra of both FTZa and FTZb were
Figure 3. UV/Vis/NIR absorption spectra of FLZa (c) and FTZa
(a) in toluene containing 5% (v/v) n-butylamine.
found to exhibit rather broad signals in the coordinating sol-
vent systems CD2Cl2/n-butylamine and [D5]pyridine, even at
elevated temperatures, which indicates that the stacking of
T-shaped porphyrin tape structures is stronger than that of
L-shaped porphyrin tapes.
amine, the absorption bands in such solvents become sharp-
ened and redshifted as a consequence of coordination-in-
duced dissociation (see the Supporting Information). The
absorption spectrum of FLZa can be divided into three
major bands, bands I, II, and III in the ranges of 330–680,
700–900, and 1250–1800 nm, which seemingly correspond to
bands I, II, and III of the linear porphyrin tapes, respective-
ly. In these three regions, FLZa shows band peaks at 499,
788, and 1622 nm, which are almost the same, but slightly
redshifted compared with those of the linear trimer 3. Note,
however, that the relative intensities of the three bands are
different; the relative intensities of bands II and III of FLZa
are smaller than those of 3.
The absorption spectra of FTZa are also dependent upon
the solvent and n-butylamine (see the Supporting Informa-
tion). The absorption spectrum of FTZa in toluene in the
presence of n-butylamine shows complicated features with
band peaks at 419, 584, 716, 1010, 1504, and 1805 nm
(Figure 3). Whereas the peak position of the lowest-energy
band is comparable to that of linear tetramer 4 (1813 nm in
UV/Vis/NIR absorption spectra: One of the most attractive
features of the porphyrin tapes is their unusual absorption
spectra that reach into the infrared region as a consequence
of full conjugation over the arrays.[51] The absorption spectra
of the linear porphyrin tapes are divided into three regions:
two higher-energy bands (bands I and II) correspond to a
split Soret band and a lower-energy band (band III) that
corresponds to the Q band. With an increase in the number
of porphyrin units, bands II and III are increasingly redshift-
ed and intense, whereas band I remains at around 410 nm.
These spectral changes have been interpreted in terms of a
decrease in the HOMO–LUMO gap and decreased molecu-
lar symmetry upon elongation of the arrays.[32] In contrast,
porphyrin sheet 5 with a highly symmetric square structure
exhibits a weak and broad absorption band in the NIR
region.[37] These previous studies indicate that the absorption
spectra of the conjugated porphyrin tapes are dependent
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A. Osuka, D. Kim et al.
CHCl3/n-butylamine), the relative intensities of the absorp-
tion bands are quite different. The three strong absorption
bands at 419, 584, and 716 nm may correspond to band I,
whereas the band at 1010 nm and the bands at 1504 and
1805 nm may correspond to bands II and III, respectively.
Similarly to FLZa, the relative intensity of band III is con-
siderably smaller than that of linear porphyrin tape 4, prob-
ably as a consequence of the bent structure of the porphyrin
tape.
43000 GM at 2100 nm and 8700 and 35700 GM at 2300 nm,
respectively. The s(2) values at 2100 nm were measured to
assess the contribution of the small one-photon absorbance
especially for FTZa.
Discussion
Linear porphyrin tapes 2, 3, and 4 exhibit a continuous red-
shift of the lowest Q-band transition into the infrared
region, which indicates that 2, 3, and 4 are fully p-conjugat-
ed over all the porphyrin planes (see Figure S24 of the Sup-
porting Information). The X-ray structure of 2 shows that
the two porphyrin rings are fused to form a coplanar saddle-
like conformation with a mean plane deviation of 0.16 Š,[49]
which is quite favorable for full p conjugation. However,
compounds 2, 3, and 4 tend to aggregate due to intrinsically
strong p–p stacking. Thus we have employed n-butylamine
to dissociate aggregates of 2, 3, and 4 in solution. The ab-
sorption spectra of 2, 3, and 4 measured in toluene contain-
ing 5% n-butylamine exhibit a continuous redshift of the Q-
bands (band III) into the IR region in addition to the en-
hanced exciton-split Soret bands in the 400–800 nm region
(bands I and II) (see Figure S24 of the Supporting Informa-
tion). This indicates that the p-conjugation pathway is elon-
gated throughout the whole molecular framework in 2, 3,
and 4. The excited singlet state (p,p*) lifetimes of 4.5, 2.9,
and 0.7 ps for 2, 3, and 4, respectively, are also consistent
with a continuous decrease in the HOMO–LUMO gaps,
which leads to an acceleration of the internal conversion
processes from S1 to S0 in going from 2 to 3 to 4.[51] Porphy-
rin sheet 5 exhibits considerably broadened absorption
bands over a wide range, from the UV/Vis to the near-IR re-
gions, which can roughly be divided into three distinct spec-
tral regions: band I (300–600 nm), band II (600–1000 nm),
and band III (1000–1500 nm) (see Figure S25 of the Sup-
porting Information).[37] Band III is considerably weaker
than that of the one-dimensional tetrameric porphyrin tape
4. The transient absorption decay profile of 5 reveals a
single exponential decay with a time constant of 1.1 ps,
which indicates that the lifetime of the S1 (p,p*) state of 5 is
slightly longer than that of tetrameric porphyrin tape 4
(0.72 ps).
TPA properties: The electronic conjugative effects as well
as the shape dependence of various meso–meso,b–b,b–b
triply linked zinc(II) porphyrin arrays are further gleaned
from their TPA cross-section (s(2)) values, which are largely
proportional to the electron-delocalization strength of the
molecule. The TPA cross-section values were measured by
using an open-aperture Z-scan method by exciting the mole-
cule with IR pulses from an IR optical parametric amplifier
pumped by a femtosecond Ti:sapphire regenerative amplifi-
er system with a 130 fs pulse width (Figure 4).
The s(2) value for 2 without any contribution from one-
photon absorption was measured to be 11900 GM at
1200 nm in our previous work.[36] Because the absorption
spectra of 3 and 4 are spread across a wide spectral range
down to the IR region, we chose an excitation wavelength
of 2300 nm, a wavelength at which the ground-state contri-
butions to the TPA cross-section values should be negligible
(Table 1). The s(2) values for 3 and 4 were measured to be
18500 and 41200 GM. But these values are much smaller
than the values of 33100 and 93600 GM for 3 and 4, respec-
tively, measured at 1200 nm in our previous work, which in-
dicates that there was one-photon contribution to the s(2)
values. We think that the TPA cross-section value of
41200 GM for 4 is, to the best of our knowledge, the largest
Figure 4. Z-scan curves of FLZa, 3, FTZa, and 4 excited at 2300 nm in
toluene containing 5% (v/v) n-butylamine.
In this study, we chose an excitation wavelength of
2300 nm for the TPA measurements, a wavelength at which
the ground-state absorption contribution to the TPA cross-
section values is negligible. Note that at 2300 nm there is
almost no absorbance for 3 and 4 in CHCl3 containing 5%
(v/v) n-butylamine in which the TPA experiments were per-
formed. At 2300 nm the s(2) values for 3 and 4 were mea-
sured to be 18500 and 41200 GM, respectively. The s(2)
values for FLZa and FTZa were measured to be 9560 and
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Extended Porphyrin Tapes
FULL PAPER
Table 1. TPA cross-section (s(2)) values and excitation wavelengths (l)
for fused porphyrin arrays in toluene containing 5% (v/v) n-butylamine.
Conclusion
s
(2) [GM]
l [nm]
s(2) [GM]
l [nm]
L- and T-shaped porphyrin tapes have been prepared
through rational synthetic routes and have been fully char-
acterized with a particular focus on their TPA properties in
comparison with those of linear porphyrin tapes. The s(2)
values for the linear tri- and tetramer porphyrin tapes were
measured to be 18500 and 41200 GM, respectively, at an ex-
citation wavelength of 2300 nm. Under similar conditions,
the s(2) values for the L-shaped tapes FLZa and FTZa were
measured to be 8700 and 35700 GM. These data clearly sub-
stantiate the importance of directionality in the p-conjuga-
tion pathway for a large TPA. Thus we believe this work
provides benchmark results especially in relation to the
origin of the enhancement of TPA cross-section values for
p-conjugated porphyrin arrays, which will further help the
process of the molecular design of molecules with large
TPA properties.
3
20600ꢀ1000
2100
3
4
18500ꢀ800
41200ꢀ1000
8700ꢀ800
2300
2300
2300
2300
FLZa
FTZa
9560ꢀ1000
2100
2100
FLZa
FTZa
43000ꢀ1000
35700ꢀ1000
one without any one-photon contribution ever reported for
single chromophore macrocyclic dyes. The hyperpolarizabili-
ty (b) and s(2) values qualitatively exhibit a linear relation-
ship and they increase with elongation of the p-conjugation
length. In this context, the very large s(2) values for 2, 3, and
4 observed in this investigation suggest that p-electron de-
localization throughout the porphyrin array framework and
the completely flat structures are the determining factors
that enhance the NLO properties.
In our previous work, the s(2) value for 5 was determined
at 1600 nm, a wavelength at which the linear absorption is
almost negligible.[37] Despite its tetrameric porphyrin con-
struction, the porphyrin sheet exhibits a very small TPA
value of 2750 GM, which is much smaller than that of the
corresponding tetrameric porphyrin tape 4, which suggests
that the electronic structure of 5 is quite unique.[37] This indi-
cates that the two-dimensional elongation of the p-conjuga-
tion pathway does not guarantee enhanced TPA, which rein-
forces the belief that molecular polarizability is an impor-
tant factor in increasing the TPA cross-section values. Note
that, based on the NMR experiments, there is a strong para-
tropic ring current along the COT core that propagates
across the whole p network of 5, affecting the local 18p-
electron aromatic porphyrin systems, whereas the four
zinc(II) porphyrin subunits still preserve a weak diatropic
ring current.[37,50] Thus, the weakening of the overall aroma-
ticity by the central COT core in 5 seems to be responsible
for the much reduced TPA cross-section value of 5 com-
pared with the corresponding linear fused array 4.
Experimental Section
General procedures: All reagents and solvents were of commercial re-
agent grade and were used without further purification except where
noted. Dry toluene was obtained by distilling over CaH2. DMF was dis-
tilled from K2CO3 before use. 1H NMR spectra were recorded on a
JEOL ECA-delta-600 spectrometer (600 MHz); chemical shifts (d) are
reported in ppm relative to CHCl3 (d=7.26 ppm) or CH2Cl2 (d=
5.30 ppm). Mass spectra were recorded on a Shimadzu/KRATOS KOM-
PACT MALDI 4 spectrometer using the positive-MALDI ionization
method with a 9-nitroanthracene or dithranol matrix or on a Shimadzu/
AXIMA-CFR plus spectrometer using the positive-MALDI ionization
method with a dithranol matrix. Spectroscopic grade toluene and CHCl3
were used as solvents for all spectroscopic studies. UV/Vis absorption
spectra were recorded on a Shimadzu UV-3100 spectrophotometer. Prep-
arative separations were performed by silica gel flash column chromatog-
raphy (Merck Kieselgel 60H Art. 7736), silica gel gravity column chroma-
tography (Wako gel C-400), and size exclusion gel permeation chroma-
tography (Bio-Rad Bio-Beads S-X1, packed with toluene or CHCl3 in a
4”100 cm gravity flow column). Recycling preparative GPC–HPLC was
carried out on a JAI LC-908 instrument using a combination of prepara-
tive JAI-GEL-2H and 2.5H columns (CHCl3 as eluent).
To extend our investigation on the shape-dependent TPA
properties of porphyrin-fused arrays, we have examined the
TPA properties of FLZa and FTZa in which the constituent
porphyrin moieties are connected in L and T shapes. The
s(2) value (8700 GM) for FLZa is only half that of linear
trimer 3. Note that the s(2) value for FLZa is comparable to
that of dimer 2. On the other hand, the s(2) value for FTZa
was measured to be 35700 GM, which is still smaller than
that of the corresponding linear shape tetramer 4, but dis-
tinctly larger than that of the trimer 3. However, in FTZa
there is the possibility of a one-photon absorption contribu-
tion to the s(2) value due to a very weak absorption tail in
the two-photon excitation at a wavelength of 2300 nm.[52]
For this reason the s(2) value for FTZa may be smaller than
that of linear tetramer 4. Thus, this study clearly suggests
that the unidirectional change in the molecular polarizability
arising from p-electron delocalization throughout the molec-
ular framework is a key factor in the enhancement of the
TPA cross-section values.
5,5-Dimethyl-2-[4-(p-dodecyloxy)phenyl]-1,3,2-dioxaborinane (8) and 5,5-
dimethyl-2-(3,5-di-tert-butylphenyl)-1,3,2-dioxaborinane (9) were synthe-
sized from p-bromododecyloxybenzene and 3,5-di-tert-butylbromoben-
zene, respectively, following a conventional synthetic method.
In the 1H NMR spectra, some of the signals from the nonyl and dodecyl
groups were not identified.
Zinc insertion: A saturated solution of Zn(OAc)2 in methanol was added
G
to a solution of the free-base porphyrin in CHCl3 and the resulting mix-
ture was stirred for 2–3 h at ambient temperature (40–508C). The reac-
tion mixture was washed with aqueous NaHCO3, then water, and extract-
ed with CHCl3. The organic layer was dried with anhydrous Na2SO4,
passed through a short plug of silica gel, and evaporated to remove the
solvent. Purification was carried out by silica gel column chromatography
and recrystallization.
5,15-Dinonylporphyrin (6): Bis(2-pyrrolyl)methane (1.6 g, 11 mmol) and
freshly distilled decanal (0.70 mL, 11 mmol) were dissolved in deoxygen-
ated CH2Cl2 (2.05 L). After stirring for 10 min under a N2 atmosphere,
trifluoroacetic acid (0.1 equiv) was added to the solution and stirred for
10.5 h at room temperature in the dark. DDQ (3.7 g, 1.5 equiv) was
added to the reaction mixture and stirred for 1 h. Then the resulting mix-
ture was passed through an alumina and then a silica gel column. The
Chem. Eur. J. 2008, 14, 8279 – 8289
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8285

A. Osuka, D. Kim et al.
purple solution obtained was evaporated to remove the solvent and the
residue was purified by recrystallization from CH2Cl2/CH3CN (0.60 g,
19%). 1H NMR (CDCl3): d=10.16 (s, 2H; meso-H), 9.57 (d, J=4.6 Hz,
4H; b-H), 9.41 (d, J=4.6 Hz, 4H; b-H), 5.01 (t, J=8.0 Hz, 4H; C9H19-a),
2.55 (m, 4H; C9H19-b), 1.81 (m, 4H; C9H19-g), 1.53 (m, 4H; C9H19-d),
0.88 (t, J=7.1 Hz, 6H; C9H19-Me), 2.91 ppm (s, 2H; NH); MS (MALDI-
TOF): m/z: calcd for C38H50N4: 562.8; found: 561.6.
6H; C9H19-Me), ꢁ2.65ppm (s, 2H; NH); MS (MALDI-TOF): m/z: calcd
for C52H69BrN4 830.0; found: 831.0.
[5,10-Bis(3,5-di-tert-butylphenyl)-15,20-dibromoporphyrinato]zinc(II)
(15): NBS (100 mg, 2.1 equiv) was added to a solution of 14 (200 mg,
0.27 mmol) in CHCl3 purged with N2 (for 15 min) and a drop of pyridine,
and the solution was stirred for 3 min under a N2 atmosphere at 08C in
the dark. The reaction mixture was added to water and extracted with
CHCl3. The organic layer was washed with brine and water, dried with
anhydrous Na2SO4, and then evaporated to remove the solvent. The resi-
due was purified by silica gel column chromatography (CHCl3/hexane).
Yield: 235 mg, 0.26 mmol, 97%; 1H NMR (CDCl3): d=9.64 (d, J=
4.7 Hz, 2H; b-H), 9.53 (s, 2H; b-H), 8.97 (d, J=4.7 Hz, 2H; b-H), 8.94
(s, 2H; b-H), 8.05 (s, 4H; Ar-H), 7.81 (s, 2H; Ar-H), 1.55 ppm (s, 36H;
tBu); MS (MALDI-TOF): m/z: calcd for C48H50Br2N4Zn 908.2; found:
907.5; UV/Vis (CHCl3): lmax =606, 565, 428 nm.
5,15-Dinonyl-10-(p-dodecyloxyphenyl)porphyrin (10): NBS (47 mg,
0.26 mmol) was added to a solution of 6 (250 mg, 0.44 mmol) in CHCl3
purged with N2 (for 15 min) and the solution was stirred for 10 min under
a N2 atmosphere at 08C in the dark. The reaction mixture was poured
into water and extracted with CHCl3. The organic layer was washed with
brine and water, dried with anhydrous Na2SO4, and then evaporated to
remove the solvent. The purple residue, compound 8 (260 mg, 1.8 equiv),
[Pd2(dba)3·CHCl3] (21 mg, 6 mol%), PPh3 (25 mg, 24 mol%), and K2CO3
N
(230 mg, 1.8 equiv) were dissolved in a mixture of toluene (1.5 mL) and
DMF (1.0 mL). The solution was deoxygenated through freeze–pump–
thaw cycles and the resulting solution was heated at 858C for 15 h under
an argon atmosphere. After cooling, the reaction mixture was washed
with water and extracted with CHCl3. The organic layer was dried with
anhydrous Na2SO4, passed through a short plug of silica gel, and evapo-
rated to remove the solvent. The product was purified by silica gel
column chromatography (CH2Cl2/hexane) and recycling preparative
GPC–HPLC (91 mg, 42% from 6). 1H NMR (CDCl3): d=10.04 (s, 1H;
meso-H), 9.54 (d, J=4.7 Hz, 2H; b-H), 9.43 (d, J=4.7 Hz, 2H; b-H),
9.34 (d, J=4.7 Hz, 2H; b-H), 8.93 (d, J=4.7 Hz, 2H; b-H), 8.09 (d, J=
8.0 Hz, 2H; Ar-H), 7.27 (d, J=8.0 Hz, 2H; Ar-H), 4.97 (t, J=8.2 Hz,
4H; C9H19-a), 4.27 (t, J=6.6 Hz, 4H; C12H25-a), 2.53 (m, 4H; C9H19-b),
2.02 (m, 4H; C12H25-b), 1.79 (m, 4H; C9H19-g), 1.65 (m, 4H; C12H25-g),
ꢁ2.84 ppm (s, 2H; NH); MS (MALDI-TOF): m/z: calcd for C56H78N4O:
823.2; found: 823.8.
AHCTREUNG
A
ACHTREUNG
a
a
AHCTREUNG
purged with argon (for 15 min) and the solution was stirred for 2 h at
reflux under an argon atmosphere. The resulting mixture was passed
through a short plug of silica gel with CH2Cl2 as eluent and purified by
silica gel column chromatography (CH2Cl2/hexane). The first band was
14 (231 mg, 0.23 mmol, 88%), the second band was 5,10-bis(3,5-di-tert-
butylphenyl)-15-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
ylporphyrinato)
zinc(II), and the third was 16. 1H NMR (CDCl3): d=
A
10.05 (s, 2H; b-H), 9.87 (d, J=4.6 Hz, 2H; b-H), 9.11 (d, J=4.6 Hz, 2H;
b-H), 9.00 (s, 2H; b-H), 8.06 (s, 4H; Ar-H), 7.79 (s, 2H; Ar-H), 1.88 (s,
24H; Bpin), 1.52 ppm (s, 36H; tBu); UV/Vis (CHCl3): lmax =550,
421 nm; MS (MALDI-TOF): m/z: calcd for C60H74B2N4O4Zn: 1002.3;
found: 1002.3.
5,15-Dinonyl-10-(p-dodecyloxyphenyl)-20-bromoporphyrin (12): NBS
(21 mg, 1.2 equiv) was added to a solution of 10 (85 mg, 0.10 mmol) in
CHCl3 purged with N2 (for 15 min) and the solution was stirred for
15 min under a N2 atmosphere at 08C in the dark. The reaction mixture
was added to water and extracted with CHCl3. The organic layer was
washed with brine and water, dried with anhydrous Na2SO4, and then
evaporated to remove the solvent. The residue was purified by silica gel
column chromatography (CHCl3/hexane). Yield: 88 mg, 95%; 1H NMR
(CDCl3): d=9.73 (d, J=4.6 Hz, 2H; b-H), 9.47 (d, J=4.8 Hz, 2H; b-H),
9.36 (d, J=4.8 Hz, 2H; b-H), 8.85 (d, J=4.6 Hz, 2H; b-H), 8.04 (d, J=
6.4 Hz, 2H; Ar-H), 7.28 (d, J=6.4 Hz, 2H; Ar-H), 4.91 (t, J=8.1 Hz,
4H; C9H19-a), 4.27 (t, J=6.4 Hz, 2H; C12H25-a), 2.49 (m, 4H; C9H19-b),
2.00 (m, 2H; C12H25-b), 1.77 (m, 4H; C9H19-g), 1.64 (m, 2H; C12H25-g),
1.50 (m, 4H; C9H19-d), 1.43 (m, 2H; C12H25-d), 0.91 (t, J=7.1 Hz, 3H;
C12H25-Me), 0.87 (t, J=7.0 Hz, 6H; C9H19-Me), ꢁ2.66ppm (s, 2H; NH);
MS (MALDI-TOF): m/z: calcd for C56H77BrN4O: 902.1; found: 901.9.
[5-(3,5-Di-tert-butylphenyl)-10,15,20-tribromoporphyrinato]zinc(II) (18):
NBS (21 mg, 3.3 equiv) was added to a solution of 17 (20 mg, 36 mmol) in
CHCl3 purged with N2 (for 15 min) and a drop of pyridine, and the solu-
tion was stirred for 10 min under a N2 atmosphere at 08C in the dark.
The reaction mixture was added to water and extracted with CHCl3. The
organic layer was washed with brine and water, dried with anhydrous
Na2SO4, and then evaporated to remove the solvent. The residue was pu-
rified by silica gel column chromatography (CHCl3/hexane). Yield:
17.4 mg, 22 mmol, 61%; 1H NMR (CDCl3): d=9.66 (m, 4H; b-H), 9.62
(d, J=4.6 Hz, 2H; b-H), 8.94 (d, J=4.4 Hz, 2H; b-H), 8.01 (s, 2H; Ar-
H), 7.84 (s, 1H; Ar); UV/Vis (CHCl3): lmax =611, 569, 430 nm; MS
(MALDI-TOF): m/z: calcd for C34H29Br3N4Zn: 798.7; found: 798.3.
[5-(3,5-Di-tert-butylphenyl)-10,15,20-tris(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)porphyrinato]zinc(II)
39 equiv) was added with syringe to
0.15 mmol), 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.52 mL, 24 equiv),
and [Pd(PPh3)2Cl2] (10 mg, 10 mol%) in dry 1,2-dichloroethane (10 mL)
(19):
Triethylamine
(0.83 mL,
a
a solution of 18 (112 mg,
5,15-Dinonyl-10-(3,5-di-tert-butylphenyl)porphyrin (11): This porphyrin
was prepared from 7 and 9 using the procedure as that used for the prep-
aration of 10. Yield: 93 mg, 30%; 1H NMR (CDCl3): d=10.05 (s, 1H;
meso-H), 9.55 (d, J=4.1 Hz, 2H; b-H), 9.43 (d, J=4.6 Hz, 2H; b-H),
9.35 (d, J=5.0 Hz, 2H; b-H), 8.91 (d, J=4.6 Hz, 2H; b-H), 8.04 (s, 2H;
Ar-H), 7.81 (s, 1H; Ar-H), 4.98 (t, J=8.7 Hz, 4H; C9H19-a), 2.55 (m, 4H;
C9H19-b), 1.52 (s, 18H; tBu), 0.85 (t, J=6.9 Hz, 6H; C9H19-Me),
ꢁ2.82ppm (s, 2H; NH); MS (MALDI-TOF): m/z: calcd for C52H70N4:
751.1; found: 901.9.
AHCTREUNG
purged with argon (for 15 min), and the solution was stirred for 1.5 h at
steady reflux under an argon atmosphere. The resulting mixture was
passed through a short plug of silica gel with CH2Cl2 and purified by
silica gel column chromatography (Et2O/hexane). The first fraction was
17, the second was monoborylated porphyrin, the third was bis-borylated
porphyrin, and the forth was 19 (91 mg, 0.097 mmol, 64%). 1H NMR
(CDCl3): d=10.08 (d, J=4.7 Hz, 2H; b-H), 10.50 (d, J=4.7 Hz, 2H; b-
H), 9.91 (d, J=4.7 Hz, 2H; b-H), 9.14 (d, J=4.7 Hz, 2H; b-H), 8.08 (d,
J=1.8 Hz, 2H; Ar), 7.83 ppm (t, J=1.7 Hz, 1H; Ar); UV/Vis (CHCl3):
lmax =585, 550, 418 nm; MS (MALDI-TOF): m/z: calcd for
C52H65B3N4O6Zn: 939.9; found: 939.3.
5,15-Dinonyl-10-(3,5-di-tert-butylphenyl)-20-bromoporphyrin (13): NBS
(11 mg, 1.2 equiv) was added to a solution of 11 (39 mg, 0.052 mmol) in
CHCl3 purged with N2 (for 15 min) and the solution was stirred for
15 min under a N2 atmosphere at 08C in the dark. The reaction mixture
was added to water and extracted with CHCl3. The organic layer was
washed with brine and water, dried with anhydrous Na2SO4, and then
evaporated to remove the solvent. The residue was purified by silica gel
column chromatography (CHCl3/hexane). Yield: 41 mg, 95%,
Typical procedure for the palladium-catalyzed Suzuki–Miyaura cross-cou-
pling reactions: The borylated porphyrin 16 or 19 (1.0 equiv), the bromi-
nated porphyrin 12 or 13 (2.2 equiv for the L-shaped array, 3.3 equiv for
the T-shaped array), [Pd2(dba)3·CHCl3] (5 mol% versus brominated por-
R
1
0.049 mmol; H NMR (CDCl3): d=9.72 (d, J=4.8 Hz, 2H; b-H), 9.47 (d,
phyrin), PPh3 (20 mol% versus brominated porphyrin), Cs2CO3
(2.0 equiv versus brominated porphyrin), and CsF (1.5 equiv versus bro-
minated porphyrin) were dissolved in a mixture of toluene and DMF
(2:3). The solution was deoxygenated by freeze–pump–thaw cycles and
J=4.6 Hz, 2H; b-H), 9.36 (d, J=4.1 Hz, 2H; b-H), 8.85 (d, J=4.6 Hz,
2H; b-H), 8.01 (s, 2H; Ar-H), 7.81 (s, 1H; Ar-H), 4.91 (t, J=7.8 Hz, 4H;
C9H19-a), 2.51 (m, 4H; C9H19-b), 1.52 (s, 18H; tBu), 0.87 (t, J=7.1 Hz,
8286
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8279 – 8289

Extended Porphyrin Tapes
FULL PAPER
the resulting solution was heated at 1008C for 12 h under an argon at-
mosphere. After cooling, the reaction mixture was poured into water and
extracted with CHCl3. The organic layer was dried with anhydrous
Na2SO4, passed through a short plug of silica gel, and evaporated to
remove the solvent. The product was purified by recycling preparative
GPC–HPLC. Insertion of zinc(II) into the isolated compounds by using
b-H), 8.85 (d, J=4.8 Hz, 2H; b-H), 8.46 (d, J=4.6 Hz, 4H; b-H), 8.44 (d,
J=5.0 Hz, 2H; b-H), 8.27 (d, J=4.6 Hz, 4H; b-H), 8.20 (d, J=1.6 Hz,
2H; o-Ar-H), 8.17 (dd, J=8.1 Hz, J=2.1 Hz, 2H; o-Ar-H), 8.10 (dd, J=
8.1 Hz, J=2.2 Hz, 2H; o-Ar-H), 8.02 (d, J=8.8 Hz, 2H; o-Ar-H), 7.90 (d,
J=5.0 Hz, 2H; b-H), 7.88 (d, J=5.0 Hz, 2H; b-H), 7.66 (s, 1H; p-Ar-H),
7.32 (dd, J=8.3 Hz, J=2.6 Hz, 2H; m-Ar-H), 7.28 (dd, J=8.2 Hz, J=
2.6 Hz, 2H; m-Ar-H), 7.22 (d, J=8.9 Hz, 2H; m-Ar-H), 4.99 (t, J=
7.7 Hz, 8H; C9H19-a), 4.89 (t, J=7.6 Hz, 4H; C9H19-a), 4.29 (t, J=6.5 Hz,
4H; C12H25-a), 4.23 (t, J=6.6 Hz, 2H; C12H25-a), 2.57 (m, 8H; C9H19-b),
2.47 (m, 4H; C9H19-b), 2.02 (m, 4H; C12H25-b), 1.96 (m, 2H; C12H25-b),
1.82 (m, 8H; C9H19-g), 1.75 (m, 4H; C9H19-g), 1.66 (m, 4H; C12H25-g),
1.60 (m, 2H; C12H25-g), 1.52 (s, 18H; tBu), 0.91 (t, J=6.9 Hz, 6H; C12H25-
Me), 0.88 (t, J=7.0 Hz, 3H; C12H25-Me), 0.81 (t, J=7.0 Hz, 12H; C9H19-
Me), 0.77 ppm (t, J=7.0 Hz, 6H; C9H19-Me); UV/Vis (CHCl3): lmax(e)=
572 (75500), 475 (264000), 413 nm (294000mꢁ1 cmꢁ1); MS (MALDI-
TOF): m/z: calcd for C202H254N16O3Zn4: 3215.7; found: 3215.8.
THb: Yield: 20%; 1H NMR (CDCl3): d=9.44 (d, J=4.6 Hz, 4H; b-H),
9.34 (d, J=4.8 Hz, 2H; b-H), 9.25 (d, J=4.6 Hz, 4H; b-H), 9.20 (d, J=
4.8 Hz, 2H; b-H), 8.95 (d, J=4.6 Hz, 4H; b-H), 8.86 (d, 4.8 Hz, 2H; b-
H), 8.84 (d, J=4.8 Hz, 2H; b-H), 8.35 (d, J=4.4 Hz, 4H; b-H), 8.33 (d,
J=4.8 Hz, 2H; b-H), 8.31 (d, J=4.8 Hz, 2H; b-H), 8.20 (s, 2H; o-Ar-H),
8.11 (s, 2H; o-Ar-H), 8.06 (s, 2H; o-Ar-H), 7.98–7.97 (m, 4H; o-Ar-H
and b-H), 7.96 (d, J=4.8 Hz, 2H; b-H), 7.83 (t, J=1.7 Hz, 2H; p-Ar-H),
7.76 (s, 1H; p-Ar-H), 7.68 (s, 1H; p-Ar-H), 4.94 (t, J=7.0 Hz, 8H; C9H19-
a), 4.85 (t, J=7.1 Hz, 4H; C9H19-a), 2.54 (m, 8H; C9H19-b), 2.44 (m, 4H;
C9H19-b), 1.79 (m, 8H; C9H19-g), 1.72 (m, 4H; C9H19-g), 1.59 (s, 18H;
tBu), 1.54 (s, 18H; tBu), 1.49 (s, 18H; tBu), 1.44 (s, 18H; tBu), 0.82 (t,
J=6.9 Hz, C9H19-Me), 0.78 (t, J=6.9 Hz, C9H19-Me), ꢁ2.07 (brs, 4H;
NH), ꢁ2.22 ppm (brs, 2H; NH); MS (MALDI-TOF): m/z: calcd for
C190H236N16Zn: 2809.4; found: 2809.4.
[Zn(OAc)2·2H2O] gave the all-zinc-metalated compounds.
N
LHa: Yield: 57%; 1H NMR (CDCl3): d=9.40 (d, J=4.3 Hz, 4H; b-H),
9.17 (d, J=4.3 Hz, 4H; b-H), 9.14 (s, 2H; b-H), 8.92 (d, J=4.3 Hz, 4H;
b-H), 8.81 (d, J=4.8 Hz, 2H; b-H), 8.22–8.19 (m, 12H), 8.13 (d, J=
8.2 Hz, 2H; o-Ar-H), 8.07 (d, J=8.2 Hz, 2H; o-Ar-H), 7.87 (s, 2H; b-H),
7.76 (s, 2H; b-H), 4.88 (brs, 8H; C9H19-a), 4.27 (t, J=6.2 Hz, 4H;
C12H25-a), 2.47 (m, 8H; C9H19-b), ꢁ2.16 ppm (s, 4H; NH) (m-Ar-H sig-
nals were obscured by the CHCl3 peak); UV/Vis (CHCl3): lmax(e)=658
(12600), 599 (21600), 561 (66300), 523 (58100), 457 (294000), 412 nm
(233000mꢁ1 cmꢁ1); MS (MALDI-TOF): m/z: calcd for C160H204N12O2Zn:
2392.8; found: 2391.3.
LZa: Yield: quant; 1H NMR (CDCl3): d=9.52 (d, J=4.8 Hz, 4H; b-H),
9.29 (d, J=4.8 Hz, 4H; b-H), 9.15 (s, 2H; b-H), 9.02 (d, J=4.9 Hz, 4H;
b-H), 8.79 (d, J=4.6 Hz, 2H; b-H), 8.13 (d, J=4.8 Hz, 4H; b-H), 8.20 (d,
J=1.9 Hz, 4H; o-Ar-H), 8.16 (d, J=4.6 Hz, 2H; b-H), 8.14 (dd, J=
9.4 Hz, J=2.2 Hz, 2H; o-Ar-H), 8.07 (dd, J=8.4 Hz, J=2.2 Hz, 2H; o-
Ar-H), 7.81 (s, 2H; b-H), 7.75 (t, J=1.9 Hz, 2H; p-Ar-H), 7.30 (dd, J=
8.4 Hz, J=2.6 Hz, 2H; m-Ar-H), 7.26 (dd, J=8.0 Hz, J=2.6 Hz, 2H; m-
Ar-H), 4.93 (t, J=7.3 Hz, 8H; C9H19-a), 4.27 (t, J=6.7 Hz, 4H; C12H25-
a), 2.52 (m, 8H; C9H19-b), 2.00 (m, 4H; C12H25-b), 1.77 (m, 8H; C9H19-g),
1.64 C12H25-g), 1.50 (s, 36H; tBu), 0.90 (t, J=7.1 Hz, 6H; C12H25-Me),
0.78 ppm (t, J=6.9 Hz, 12H; C9H19-Me); UV/Vis (CHCl3): lmax(e)=566
(60300), 461 (261000), 414 nm (213000mꢁ1 cmꢁ1); MS (MALDI-TOF):
calcd for C160H200N12O2Zn3: 2519.4; found: 2519.2.
TZb: Yield: quant; 1H NMR (CDCl3): d=9.58 (d, J=4.6 Hz, 4H; b-H),
9.48 (d, J=4.8 Hz, 2H; b-H), 9.39 (d, J=4.8 Hz, 4H; b-H), 9.33 (d, J=
4.8 Hz, 2H; b-H), 9.06 (d, J=4.6 Hz, 4H; b-H), 8.96 (d, J=4.9 Hz, 2H;
b-H), 8.87 (d, J=4.9 Hz, 2H; b-H), 8.47 (d, J=4.6 Hz, 4H; b-H), 8.46 (d,
J=4.8 Hz, 2H; b-H), 8.29 (d, J=4.6 Hz, 2H; b-H), 8.22 (d, J=1.6 Hz,
2H; o-Ar-H), 8.14 (t, J=1.6 Hz, 2H; o-Ar-H), 8.07 (t, J=1.6 Hz, 2H; o-
Ar-H), 8.00 (d, J=1.6 Hz, 2H; o-Ar-H), 7.92 (d, J=4.8 Hz, 2H; b-H),
7.90 (d, J=4.8 Hz, 2H; b-H), 7.83 (d, J=1.6 Hz, 2H; p-Ar-H), 7.76 (d,
J=1.6 Hz, 2H; p-Ar-H), 7.67 (d, J=1.6 Hz, 2H; p-Ar-H), 5.00 (t, J=
7.7 Hz, 8H; C9H19-a), 4.92 (t, J=8.0 Hz, 4H; C9H19-a), 2.60 (m, 8H;
C9H19-b), 2.50 (m, 4H; C9H19-b), 1.86 (m, 8H; C9H19-g), 1.77 (m, 4H;
C9H19-g), 1.59 (s, 18H; tBu), 1.55 (s, 18H; tBu), 1.50 (s, 18H; tBu), 1.44
(s, 18H; tBu), 0.83 (t, J=6.9 Hz, C9H19-Me), 0.79 ppm (t, J=6.9 Hz,
C9H19-Me); MS (MALDI-TOF): calcd for C190H230N16Zn4: 2999.6; found:
2999.2.
LHb: Yield: 22%; 1H NMR (CDCl3): d=9.42 (d, J=4.8 Hz, 4H; b-H),
9.19 (d, J=4.3 Hz, 4H; b-H), 9.16 (s, 2H; b-H), 8.92 (d, J=4.8 Hz, 2H;
b-H), 8.83 (d, J=4.6 Hz, 2H; b-H), 8.23 (d, J=4.6 Hz, 4H; b-H), 8.21 (d,
J=1.9 Hz, 4H; o-Ar-H), 8.09 (t, J=1.6 Hz, 2H; o-Ar-H), 8.04 (t, J=
1.6 Hz, 2H; o-Ar-H), 7.91 (s, 2H; b-H), 7.82 (t, J=1.7 Hz, 2H; p-Ar-H),
7.77 (t, J=1.7 Hz, 2H; p-Ar-H), 4.89 (t, J=7.9 Hz, 8H; C9H19-a), 2.49
(m, 8H; C9H19-b), 1.75 (m, 8H; C9H19-g), 1.57 (s, 18H; tBu), 1.53 (s,
18H; tBu), 1.52 (s, 36H; tBu), 0.79 (t, J=6.3 Hz, 12H; C9H19-Me),
ꢁ2.12 ppm (brs, 4H; NH); MS (MALDI-TOF): m/z: calcd for
C
152H188N12Zn: 2248.6; found: 2249.5.
LZb: Yield: quant; 1H NMR (CDCl3): d=9.54 (d, J=4.8 Hz, 4H; b-H),
9.30 (d, J=4.8 Hz, 4H; b-H), 9.16 (s, 2H; b-H), 9.03 (d, J=4.8 Hz, 4H;
b-H), 8.81 (d, J=4.6 Hz, 2H; b-H), 8.33 (d, J=4.8 Hz, 4H; b-H), 8.21
(s,4H; o-Ar-H), 8.19 (d, J=4.8 Hz, 2H; b-H), 8.11 (s, 2H; o-Ar-H), 8.04
(s, 2H; o-Ar-H), 7.83 (s, 2H; b-H), 7.81 (s, 2H; p-Ar-H), 7.76 (s, 2H; p-
Ar-H), 4.94 (t, J=7.8 Hz, 8H; C9H19-a), 2.54 (m, 8H; C9H19-b), 1.79 (m,
8H; C9H19-g), 1.57 (s, 18H; tBu), 1.52 (s, 18H; tBu), 1.51 (s, 36H; tBu),
0.79 ppm (t, J=6.8 Hz, 12H; C9H19-Me); MS (MALDI-TOF): m/z: calcd
for C152H184N12Zn3: 2375.4; found: 2374.4.
THa: Yield: 62%; 1H NMR (CDCl3): d=9.43 (d, J=4.8 Hz, 4H; b-H),
9.33 (d, J=4.9 Hz, 2H; b-H), 9.23 (d, J=4.8 Hz, 4H; b-H), 9.17 (d, J=
5.0 Hz, 2H; b-H), 8.94 (d, J=4.6 Hz, 4H; b-H), 8.83 (d, J=4.8 Hz, 4H;
b-H), 8.31 (d, J=4.6 Hz, 2H; b-H), 8.29 (d, J=4.9 Hz, 2H; b-H), 8.27 (d,
J=4.9 Hz, 2H; b-H), 8.18 (s, 2H; o-Ar-H), 8.15 (d, J=8.0 Hz, 2H; o-Ar-
H), 8.09 (d, J=8.0 Hz, 2H; o-Ar-H), 8.01 (d, J=8.0 Hz, 2H; b-H), 7.90
(d, J=4.9 Hz, 2H; b-H), 7.66 (s, 1H; p-Ar-H), 7.31 (d, J=7.8 Hz, 2H; m-
Ar-H), 7.28 (d, J=8.0 Hz, 2H, m-Ar-H), 7.22 (d, J=8.7 Hz, 4H; m-Ar-
H), 4.92 (brt, 8H; C9H19-a), 4.83 (brt, 4H; C9H19-a), 4.28 (t, J=6.5 Hz,
4H; C12H25-a), 4.22 (t, J=6.6 Hz, 2H; C12H25-a), 2.51 (m, 8H; C9H19-b),
2.41 (m, 4H; C9H19-b), 2.01 (m, 4H; C12H25-b), 1.96 (m, 2H; C12H25-b),
ꢁ2.11 (s, 4H; NH), ꢁ2.27 ppm (s, 2H; NH) (m–Ar-H signals were ob-
scured by the CHCl3 peak); UV/Vis (CHCl3): lmax(e)=659 (16100), 601
(33900), 566 (84800), 524 (92000), 472 (272000), 410 nm
(296000mꢁ1 cmꢁ1); MS (MALDI-TOF): m/z: calcd for C202H260N16O3Zn:
3025.7; found: 3025.8.
Typical procedure for DDQ/Sc
ACHTREUNG
meso linked oligomer, DDQ, and Sc
AHCTREUNG
from light were heated at 908C under an argon atmosphere. After cool-
ing to room temperature, THF was added to the reaction mixture and
the resulting solution was passed through an alumina column with THF
as eluent. The solution obtained was evaporated to remove the solvent
and the residue was recrystallized from CH2Cl2/CH3CN.
FLZa: A mixture of LZa (21.5 mg, 8.5 mmol), DDQ (20 mg, 88 mmol),
and Sc(OTf)3 (40 mg, 82 mmol) in toluene (15 mL) shielded from light
C
was heated at 908C for 3 h under an argon atmosphere. Yield: 19.1 mg,
7.6 mmol, 89%; 1H NMR ([D5]pyridine): d=8.67 (br, 2H), 8.62 (d, J=
4.1 Hz, 2H), 8.45 (br, 2H), 8.05 (d, J=4.6 Hz, 2H), 8.01 (d, J=4.13 Hz,
2H), 7.93 (d, J=7.3 Hz, 4H), 7.87 (br, 6H), 7.37 (d, J=8.3 Hz, 4H), 4.43
(br, 4H), 4.31 (t, J=6.4 Hz, 4H), 2.75 (t, J=6.8 Hz, 4H), 2.57 (m, 4H),
2.17 (m, 4H), 2.04 (m, 4H), 1.93 ppm (m, 4H) (several peaks were ob-
scured by a large solvent signal); UV/Vis (toluene/5% n-butylamine):
lmax(e)=499 (48600), 788 (25300), 1622 nm (9800mꢁ1 cmꢁ1); MS
(MALDI-TOF): m/z: calcd for C160H192N12O2Zn3: 2511.3; found: 2511.2.
FLZb: A mixture of LZb (8.1 mg, 3.4 mmol), DDQ (15 mg, 66 mmol), and
Sc(OTf)3 (30 mg, 61 mmol) in toluene (3 mL) shielded from light was
A
TZa: Yield: quant; 1H NMR (CDCl3): d=9.56 (d, J=4.9 Hz, 4H; b-H),
9.46 (d, J=4.8 Hz, 2H; b-H), 9.38 (d, J=4.8 Hz, 4H; b-H), 9.31 (d, J=
4.8 Hz, 2H; b-H), 9.05 (d, J=4.6 Hz, 4H; b-H), 8.94 (d, J=4.8 Hz, 2H;
heated at 908C for 3 h under an argon atmosphere. Yield: 6.1 mg,
2.6 mmol, 77%; 1H NMR (CD2Cl2/1% n-butylamine (v/v)): d=8.24 (d,
J=4.6 Hz, 2H; b-H), 8.20 (s, 2H; b-H), 8.15 (d, J=4.6 Hz, 2H; b-H),
Chem. Eur. J. 2008, 14, 8279 – 8289
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8287

A. Osuka, D. Kim et al.
7.76 (s, 2H; b-H), 7.64 (d, J=4.4 Hz, 2H; b-H), 7.63–7.61 (m, 8H; b-H,
o-Ar-H, p-Ar-H), 7.56 (t, J=1.9 Hz, 2H; p-Ar-H), 7.43 (d, J=1.9 Hz,
4H; o-Ar-H), 6.73 (s, 2H; b-H), 6.71 (s, 2H; b-H), 4.05 (t, J=8.3 Hz,
4H; nonyl-a), 3.73 (t, J=8.0 Hz, 4H; nonyl-a), 2.24 (m, 4H; nonyl-b),
2.01 (m, 4H; nonyl-b), 1.44 (s, 36H; tBu), 1.43 ppm (s, 36H; tBu) (the
other signals arising from the C9H19 chain were obscured by signals from
n-butylamine and could not be identified); MS (MALDI-TOF): m/z:
calcd for C152H176N12Zn3: 2367.2; found: 2367.2.
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and Sc(OTf)3 (30 mg, 61 mmol) in toluene (15 mL) shielded from light
A
was heated at 908C for 2.5 h under an argon atmosphere. Yield: 13.9 mg,
4.3 mmol, 85%; UV/Vis (toluene/5% n-butylamine): lmax(e)=418
(103000), 584 (95700), 716 (102000), 1805 nm (28100mꢁ1 cmꢁ1); MS
(MALDI-TOF): m/z: calcd for C202H242N16O3Zn4: 3203.8; found: 3203.2.
FTZb: A mixture of TZb (9.1 mg, 3.0 mmol), DDQ (15 mg, 66 mmol), and
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Sc(OTf)3 (30 mg, 61 mmol) in toluene (3 mL) shielded from light was
A
heated at 908C for 3 h under an argon atmosphere. Yield: 6.8 mg,
2.3 mmol, 75%; MS (MALDI-TOF): m/z: calcd for C190H218N16Zn4
2987.5; found: 2987.7.
Measurement of the two-photon absorption cross-section (s(2)): The TPA
experiments were performed by using the open-aperture Z-scan
method[53] with 130 fs pulses from an optical parametric amplifier (Light
Conversion, TOPAS) operating at a 5 kHz repetition rate using a Ti:sap-
phire regenerative amplifier system (Spectra-Physics, Hurricane). The
laser beam was divided into two and detected by two identical InGaAs
photodiodes. One was monitored by an InGaAs PIN photodiode (New
Focus) as a reference of the intensity, and the other was used for trans-
mittance studies. After passing through an f=10 cm lens, the laser beam
was focused and passed through a quartz cell. The position of the sample
cell could be varied along the direction of the laser beam (z axis) and so
the local power density within the sample cell could be changed under a
constant laser power. The thickness of the cell was 1 mm. The laser beam
transmitted from the sample cell was then probed by using the photo-
diode used for reference monitoring. The on-axis peak intensity of the in-
cident pulses at the focal point I0 ranged from 40 to 60 GWcmꢁ1. Assum-
ing a Gaussian beam profile, the nonlinear absorption coefficient b can
be obtained by curve-fitting to the observed open-aperture traces using
Equation (1) in which a0 is the linear absorption coefficient, l is the
sample length, and z0 is the diffraction length of the incident beam. After
obtaining the nonlinear absorption coefficient b, the TPA cross-section
s(2) (given in units of 1 GM=10ꢁ50 cm4 sphotonꢁ1 moleculeꢁ1) of a single
solute molecule sample can be determined from Equation (2) in which
NA is the Avogadro constant, d is the concentration of the TPA com-
pound in solution, h is Planckꢁs constant, and n is the frequency of the in-
cident laser beam. To satisfy the condition a0l !1, which allows the pure
TPA s(2) values to be determined using a simulation procedure, the TPA
cross-section value for AF-50 was measured as a reference compound;
this control was found to exhibit a TPA value of 50 GM at 800 nm.
0 l
bI0ð1ꢁeꢁa
Þ
2
TðzÞ ¼ 1ꢁ
2a0½1 þ ðz=z0Þ ꢂ
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s
ð2ÞNAd ꢃ 10ꢁ3
b ¼
hn
Acknowledgements
The work at Kyoto was partly supported by a Grant-in-Aid from the
Ministry of Education, Culture, Sports, Science and Technology, Japan
(No. 1920006). The work at Yonsei University was supported by the Star
Faculty program from the Ministry of Education and Human Resources
Development, Korea. S.Y.J., J.M.L., and K.S.K. acknowledge the BK21
fellowship. The authors thank Prof. Hiromitsu Maeda and Mr. Takashi
Hashimoto, Ritsumeikan University, for MALDI-TOF MS measure-
ments.
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8288
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 8279 – 8289

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Received: April 24, 2008
Published online: July 30, 2008
Chem. Eur. J. 2008, 14, 8279 – 8289
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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8289