Effects of axial ligands on the formation of a layered structure in mono- and di-cationic charged tetraphenylporphyrinatoantimony(V)/synthetic clay composites

Article abstract of DOI:10.1246/bcsj.78.2251

Novel metalloporphyrin-clay composites were prepared from a synthetic clay (Sumecton SA: SSA) and cationic tetraphenylporphyrinatoantimony(V) bromide (SbTPP, 1-4) having various axial ligands. Both the crystal structure for SbTPP-SSA composites and the ad

Full text of DOI:10.1246/bcsj.78.2251

ꢀ 2005 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 78, 2251–2258 (2005) 2251
Effects of Axial Ligands on the Formation of a Layered Structure in
Mono- and Di-Cationic Charged Tetraphenylporphyrinatoantimony(V)/
Synthetic Clay Composites
ꢀ
Tsutomu Shiragami, Keiko Nabeshima, Satoko Nakashima, Jin Matsumoto,
Shinsuke Takagi,1 Haruo Inoue,1 and Masahide Yasuda
Department of Applied Chemistry, Faculty of Engineering, University of Miyazaki,
Gakuen-Kibanadai, Miyazaki 889-2192
1CREST, JST (Japan Science and Technology Agency), 4-1-8 Honcho, Kawaguchi 332-0012
Received June 2, 2005; E-mail: t0g109u@cc.miyazaki-u.ac.jp
Novel metalloporphyrin–clay composites were prepared from a synthetic clay (Sumecton SA: SSA) and cationic
tetraphenylporphyrinatoantimony(V) bromide (SbTPP, 1–4) having various axial ligands. Both the crystal structure for
SbTPP–SSA composites and the adsorption behaviors of SbTPP into SSA sheets are investigated regarding the relation
to the structure of an axial ligand at SbTPP by measuring the X-ray diffraction (XRD), IR, UV–vis, and fluorescence
spectroscopy. The XRD analysis revealed that powdered SbTPP–SSA composites could take a layered structure for
1, and an amorphous structure for 2, respectively. The IR spectrum of naked SSA showed a broad absorption band
around 3000–3600 cmꢁ1, which can probably be assigned as some adsorbed water molecules onto SSA. The intensity
of the broad absorption band became weaker with an increase of the loading level (%LL), which was defined as a ratio
of the concentration of the cationic sites of 1–4 to the concentration of anionic sites of SSA. The band completely dis-
appeared at 100%LL in both 2–SSA and 4–SSA composites with the amorphous structure, whereas the band remained
even at 100%LL in both 1–SSA and 3–SSA composites with the layered structure. Information about an aggregation
state of 1–4 into SSA was obtained by measuring both the UV–vis absorption spectra of 1–4 in an aqueous colloidal
clay solution and the fluorescence spectra of SbTPP–SSA composites in the solid state by using a confocal laser scanning
fluorescence microscope. Each spectral data indicated that the ammonium cationic part on an axial ligand of 1 only led to
effective non-aggregated adsorption onto SSA sheets, while 2–4 were located with the aggregated state on SSA sheets.
These results also support that an axial ligand structure can control not only the formation of the crystal structure, but
also the adsorption behaviors with aggregation or non-aggregation onto SSA sheets.
The hybridization of some functional molecules into multi-
layered inorganic materials, such as clay minerals, is now at-
tracting much attentions from the viewpoints of constructing
inorganic/organic hybrid systems with new functionalities.1–6
Clay minerals are known to provide two-dimensional spaces
with highly ordered nano-structured environments for chemi-
cal reactions.7–10 It is, therefore, expected that some organic
compounds as guests adsorbed onto nano-clay sheets or inter-
calated nano-space interlayer can induce unique chemical be-
haviors by hybridization with clays as inorganic hosts. Recent-
ly, several studies on the photochemical properties of dye
molecules onto a clay surface, or in the interlayer space, have
elucidated that aggregation caused a disadvantage for a photo-
reaction owing to a decrease of the excited-state lifetime.7–20
Therefore, the control of dye aggregation is very important to
make a photoreaction effective in a clay system. Our research
group has recently reported that unique hybrids in which por-
phyrin derivatives having þ4 pyridinium cationic substitutes
adsorb on the synthetic cation-exchangeable smectite clay
(Sumecton SA: SSA) at high density without aggregation.21–24
This effect was explained as being a size-matching effect i.e.,
the distance between a positive charged site in porphyrin mole-
cules is matched with negatively charged sites on the clay
sheet. The photochemical energy transfer in the size-matching
effect in the porphyrin–clay system proceeded efficiently.24
On the other hand, porphyrin and metalloporphyrin dyes are
of interest because of their photochemical activity as well
as their biochemical and catalytic functionality.25 We have
previously reported that tetraphenylporphyrinatoantimony(V)
complexes (SbTPP) derivatives could work not only as sensi-
tizers,26–29 but also as photocatalysts.30–35 In most reports on
the porphyrin–clay system, porphyrins having þ4 charged sub-
stituents at the meso-position (e.g. alkyl pyridinium salt) were
used as guest molecules for clay, as described above. SbTPP
complexes are a ‘‘þ1 charged cationic complex’’ where the
positive charge can delocalize in a ꢀ-electron system of a por-
phyrin ring and have two axial ligands. They are a different
type from the þ4 cationic pyridinium-type porphyrin com-
plexes. Therefore, we have recently reported on the adsorp-
tion and intercalation of a new type of cationic SbTPP into
SSA.36–38 In recent reports, we elucidated that the formation
of the crystal structure of SbTPP–SSA composites strongly de-
pended on the change of the axial ligand structure with SbTPP.
This result gives new significant information as to how to con-
trol both the orientation of the cationic porphyrin adsorbed
onto the clay surface and the structure of the porphyrin–clay
Published on the web December 9, 2005; DOI 10.1246/bcsj.78.2251

2252 Bull. Chem. Soc. Jpn., 78, No. 12 (2005)
Structure of Cationic SbTPP/Clay Composites
mony(V) bromide ([SbTPP(Br)2]þBrꢁ) was performed in MeOH–
MeCN (1:1 v/v) to give [SbTPP(Br)(OMe)]þBrꢁ. A MeCN–pyr-
idine solution (5:1 v/v 50 mL) containing [SbTPP(Br)(OMe)]þ-
Brꢁ (1.1 mmol) and N,N-dimethyl-3-amino-1-propanol (30 mmol)
was heated for 2 h at 65 ꢂC. The solvent was evaporated and the
residue was solved in CH2Cl2. The CH2Cl2 solution was washed
three times with 50 mL portions of H2O. After evaporation, the
crude product was chromatographed on silica gel (Fiji Silysia
BW-300) using CHCl3–MeOH (10:1 v/v) as an eluent to give
2a. For methylation of the dimethylamino group, MeI (32 mmol)
was added to a MeCN–pyridine solution (5:1 v/v 50 mL) of 2a
(1.1 mmol) and then heated for 2 h at 65 ꢂC. The purification of
1a was performed by a similar procedure for the case of 2a. Com-
plex 1b was basically synthesized by a similar procedure with the
synthesis of 1a. A MeCN–pyridine solution (5:1 v/v 50 mL) con-
taining [SbTPP(Br)(OMe)]þBrꢁ (1.1 mmol) and 2-(N,N-dimethyl-
Sumecton SA (SSA)
Mn+ = Na+ or Mg2+
1
+
OR
N
Mn+ Mn+
N
0.40 nm
Br −
Sb
N
N
2
Mn+ Mn+ Mn+
OR
1.75 nm
-
1
2
1a; R = -(CH ) -NMe
I
R = Me
2 3
3
-
1
2
1b; R = -(CH ) -O-(CH ) -NMe
I
R
= Me
2 2
2 2
3
1
2
2a; R = -(CH ) -NMe
R = -Me
2 3
2
1
2
2b; R = -(CH ) -O-(CH ) -NMe
R
= Me
2 2
2 2
2
1
2
1
2
3; R = R = H
4; R = R = Me
ꢂ
aminoethoxy)ethanol (30 mmol) was heated for 2 h at 65 C, and
then methylation of the dimethylamino group by MeI (32 mmol)
to give 1b.
Fig. 1. Structure of tetraphenylporphyrinatoantimony(V)
complexes and SSA.
3-Trimethylammoniopropoxo(methoxo)tetraphenylporphyrinato-
antimony(V) bromide (1a): Yield 94% from 2a; UV–vis (MeOH)
composite, revealing that the adsorption can be controlled by
the position and structure of an interactive site located in the
horizontal direction as well as the vertical direction for por-
phyrin plane. Since it was suggested that the effect of the axial
ligand on the formation of the SbTPP–SSA composites struc-
ture could be attributed to a strong interaction between an axial
ligand and the anionic clay sheets, the use of SbTPP having
organo cations as an axial ligand, which are known to undergo
interactions with the anionic clay sheets,39 can be a clue to
clarify the role of axial ligands in the SbTPP–SSA composites
system.
In this paper, we report on the adsorption and intercalation
behaviors of novel SbTPP 1 having an ammonium cationic part
as an axial ligand (Fig. 1) into SSA in order to elucidate the
relationships between the structure of the axial ligand and the
formation of the layer structure of SbTPP–SSA composites or
the SbTPP molecular orientation adsorbed into SSA sheets.
ꢂ
max/nm (log "): 419 (5.48), 551 (4.15), and 591 (3.93); SIMS:
m=z 881 (Mþ ꢁ 2); H NMR (CDCl3/ppm) ꢃ ꢁ2:59 (2H, t, J ¼
6:0 Hz, –OCH2–), ꢁ2:24 (3H, s, –OMe), ꢁ1:14 (2H, quint, J ¼
6:0 Hz, –CH2–), 0.89 (2H, t, J ¼ 6:0 Hz, –CH2–þN–), 2.18 (9H, s,
–þNMe3), 7.83–8.00 (12H, m, Ph), 8.24 (4H, d, J ¼ 6:6 Hz, Ph),
8.67 (4H, d, J ¼ 6:6 Hz, Ph), 9.58 (8H, s, pyrrole).
1
3-(Dimethylamino)propoxo(methoxo)tetraphenylporphyrinato-
antimony(V) bromide (2a): Yield 80%; UV–vis (MeOH) ꢂmax
/
nm (log "): 419 (5.58), 551 (4.25), and 591 (4.09); SIMS: m=z
866 (Mþ ꢁ 2); 1H NMR (CDCl3/ppm) ꢃ ꢁ2:65 (2H, t, J ¼ 6:2
Hz, –OCH2–), ꢁ2:29 (3H, s, –OMe), ꢁ1:58 (2H, quint, J ¼ 6:2
Hz, –CH2–), 0.20 (2H, t, J ¼ 6:2 Hz, –CH2–N–), 1.40 (6H, s,
–NMe2), 7.79–7.93 (12H, m, Ph), 8.23 (4H, d, J ¼ 6:7 Hz, Ph),
8.34 (4H, d, J ¼ 6:7 Hz, Ph), 9.48 (8H, s, pyrrole).
2-(2-Trimethylammonioethoxy)ethoxo(methoxo)tetraphenylpor-
phyrinatoantimony(V) bromide (1b): Yield 40%; UV–vis (MeOH)
ꢂ
max/nm (log "): 420 (5.68), 552 (4.29), and 591 (4.08); SIMS:
m=z 911 (Mþ); 1H NMR (CDCl3/ppm) ꢃ ꢁ2:40 (2H, t, J ¼ 4:7
Hz, Sb–OCH2–), ꢁ2:14 (3H, s, –OMe), 0.35 (2H, t, J ¼ 4:7 Hz,
–CH2–O–), 2.15 (2H, t, J ¼ 5:0 Hz, –CH2–þNMe3), 2.35 (9H, s,
–þNMe3), 2.60 (2H, t, J ¼ 5:0 Hz, –O–CH2–), 7.95–8.09 (12H,
m, Ph), 8.38–8.44 (8H, m, Ph), 9.69 (8H, s, pyrrole).
Experimental
Instruments. The UV–vis absorption spectra and fluorescence
spectra of solutions were measured on a Hitachi U2001 spectrom-
eter and on a Hitachi F4500 spectrometer, respectively. X-ray dif-
fraction spectra (XRD) were measured on a RIGAKU RINT2500
spectrometer (Cu Kꢁ, 40 kV/50 mA). IR spectra were measured
on a JASCO Herscel FT/IR-300 spectrometer. 1H NMR spectra
were taken in CDCl3 using tetramethylsilane as an internal stan-
dard on a Bruker AC 250P spectrometer at 250 MHz. Mass analy-
sis was carried out by mass spectroscopy (SIMS method) on a
Hitachi M-2000AM. Fluorescence spectra of powdered samples
were measured on a confocal laser scanning fluorescence micro-
scope (CLSM) (FV-300, Olympus) equipped with a spectro-
photometer (STFL 250, Seki Technotron).
2-(2-Dimethylaminoethoxy)ethoxo(methoxo)tetraphenylporphy-
rinatoantimony(V) bromide (2b): Yield 36%; UV–vis (MeOH)
ꢂ
max/nm (log "): 421 (5.68), 553 (4.29), and 593 (4.06); SIMS:
m=z 896 (Mþ); 1H NMR (CDCl3/ppm) ꢃ ꢁ2:45 (2H, t, J ¼ 4:7
Hz, Sb–OCH2–), ꢁ2:20 (3H, s, –OMe), 0.18 (2H, t, J ¼ 4:7 Hz,
–CH2–O–), 1.80 (2H, t, J ¼ 5:0 Hz, –CH2–NMe2), 1.87 (6H, s,
–NMe2), 2.80 (2H, t, J ¼ 5:0 Hz, –O–CH2–), 7.93–8.04 (12H,
m, Ph), 8.27–8.40 (8H, m, Ph), 9.57 (8H, s, pyrrole).
Results
Materials. Sumecton SA (SSA) was received from Kunimine
Industries Co., Ltd. and used without further purification. Water
was deionized below 0.02 mS cmꢁ1 of the conductivity with a
MILLIPORE Elix 3 system equipped with a RO membrane mod-
ule before use.
Synthesis of SbTPP Derivatives (1–4). The syntheses of 3
and 4 were performed according to a reported method.30 The syn-
theses of 1 and 2 were carried out by the following procedures.
The mono-methanolysis of dibromo(tetraphenylporphyrinato)anti-
Preparation of SbTPP–SSA Composites. SbTPP–SSA
composites were prepared by mixing an aqueous SSA colloidal
solution with the respective aqueous 1–4 solutions under son-
ication at room temperature. The SSA concentration was set to
50 mg dmꢁ3 unless otherwise noted. The concentration of
anionic sites in a colloidal solution of SSA was calculated to
be 5:0 ꢃ 10ꢁ5 mol dmꢁ3 from the cation exchange capacity
(CEC) value of SSA.22

T. Shiragami et al.
Bull. Chem. Soc. Jpn., 78, No. 12 (2005) 2253
1.2
(A)
(B)
1.0
0.8
0.6
0.4
0.2
0.0
%LL = 20
%LL = 40
%LL = 20
%LL = 40
%LL = 60
%LL = 80
0
20 40 60 80 100
%LL
%LL = 60
%LL = 80
Fig. 3. Relationship between the %LL and the interlayer
distance determined by XRD measurement of 1a–SSA
composite.
%LL = 100
%LL = 100
assigned to be O–H stretching vibration of adsorbed water
molecules into SSA. The O–H band intensities of the 1a–
SSA composite decreased with an increase of %LL, but the
O–H band remained even at 100%LL. A similar behavior was
observed in the case of the 3–SSA composite (Fig. 5). In the
case of 2a–SSA and 4–SSA composites, on the other hand,
the O–H band completely disappeared at 100%LL, as shown
in Fig. 6. Figure 7 shows the dependence of %LL on a ratio
of the peak area of the O–H band at each %LL to that of the
naked SSA used as a standard. The 1a–SSA and 3–SSA com-
posites having the layer structure can keep the adsorbed water
molecules in the SSA layer.
Absorption Spectra of SbTPP–SSA Composites in an
Aqueous Colloidal Solution. The ꢂmax of the Soret band
of 2a shifted to longer wavelength in ca.11–12 nm owing to
adsorption onto the clay along with the broadening and split-
ting of the Soret band with an increase of %LL (Fig. 8). A sim-
ilar spectral change was also observed in a colloidal SSA solu-
tion with 2b. However, the absorption spectrum of 1a showed
a smaller red shift, though a broadening and splitting of the
Soret band were not observed along with an increase of %LL,
as shown in Fig. 8. This result indicates that the ꢀ–ꢀ interac-
tion between the porphyrin rings with each other should be
weaker in the case of 1a. Since similar phenomena were also
observed in the colloidal 1b–SSA solution, the existence of a
cationic part on an axial ligand can be a requisite for a non-
broading and non-splitting of the Soret band in the SbTPP–
SSA system. The absorption data of SbTPP–SSA composites
are summarized in Table 1. All SbTPP (1–4) were adsorbed
onto SSA quantitatively, because of no observation of the
absorption peaks of 1–4 in their filtrates by the filtration of
SbTPP–SSA powder. The quantitative adsorption onto SSA
was also supported from the observation of free 1–4 in the
colloidal SSA solution at 120%LL.
3
4
5
6
7
8
9 10
3
4
5
6
7
8
9 10
2
θ / degree
2
/ degree
θ
Fig. 2. The XRD profiles of (A) 1a–SSA and (B) 2a–SSA
composites at various %LL.
The loading level (%LL) was defined as the ratio of the
concentration of cationic sites of 1–4 to the concentration of
the anionic sites of SSA. Various %LL were adjusted by the
addition of a given amount of SSA (5:0 ꢃ 10ꢁ6–5:0 ꢃ 10ꢁ5
mol dmꢁ3) to a solution of 1–4 (5:0 ꢃ 10ꢁ6 mol dmꢁ3). Mea-
surements of the absorption spectra were performed for a col-
loidal solution of SbTPP–SSA complexes with various %LL at
room temperature. The powdered complexes were collected by
filtration of the mixture prepared above through a membrane
filter (pore size = 1 mm) and dried at room temperature. They
were then subjected to measurements of XRD, IR spectra (KBr
method), and confocal laser scanning fluorescence microscope,
respectively.
XRD Analysis of SbTPP–SSA Composite Powders. An
XRD analysis was performed for the prepared samples by the
filtration of colloidal SbTPP–SSA particles. The XRD profile
of 1a–SSA composites showed that the layer structure of SSA
was kept at various %LL values irrespective of the addition of
1a (Fig. 2A). Also, similar profiles were observed in the cases
of 1b–SSA and 3–SSA composites. The interlayer distance
strongly depended on the %LL of SbTPP. Figure 3 is a typical
example for the case of the 1a–SSA composite. The resulting
interlayer distance became 1.03 nm for 1a–SSA, 0.97 nm for
1b–SSA, and 1.09 nm for 3–SSA in more than 60%LL, respec-
tively. On the other hand, the XRD profiles for the 2–SSA and
4–SSA composites showed no diffraction peaks, indicating the
formation of the amorphous structure shown in Fig. 2B. Ac-
cordingly, these results obviously demonstrate that 2 and 4
can not intercalate into SSA with a layer structure, but only
adsorb on the surface of SSA with an amorphous structure.
Fluorescence Spectra of SbTPP–SSA Composites in an
Aqueous Colloidal Solution and Solid State. The fluores-
cence spectra were measured for a air-purged colloidal
SbTPP–SSA solution with various %LL under excitation of
the porphyrin chromophore at room temperature. The fluores-
cence quantum yield (ꢀ) was determined by using 3 (ꢀ ¼
IR Spectra of SbTPP–SSA Composite Powders.
shown in Fig. 4, the IR spectrum of naked SSA gave a broad
absorption band at around 3000–3600 cmꢁ1, which can be
As

2254 Bull. Chem. Soc. Jpn., 78, No. 12 (2005)
Structure of Cationic SbTPP/Clay Composites
SSA
%LL = 60
%LL = 20
%LL = 40
%LL = 80
%LL = 100
4600
4000
3000
2000
1700
4600
4000
3000
2000
1700
Wavenumber / cm-1
Wavenumber / cm-1
Fig. 4. IR spectra of SSA and 1a–SSA composite at various %LL.
%LL = 20
%LL = 40
%LL = 60
%LL = 100
4600
4000
3000
2000
1700
4600
4000
3000
2000
1700
Wavenumber / cm-1
Wavenumber / cm-1
Fig. 5. IR spectra of 3–SSA composite at various %LL.
0:0518 in MeCN) as an actinometer, according to the reported
method.28 Table 1 gives the fluorescence spectra and fluores-
cence quantum yield (ꢀf) of SbTPP–SSA composites. The
ꢂmax values of the fluorescence spectra of 1–SSA and 2–
SSA also show red shifts (ca. 7 nm) owing to adsorption onto
the clay. In a previous report,37 ꢀf of 3 adsorbed onto SSA
(%LL = 80%) extremely decreased (ꢀf ¼ 4:5 ꢃ 10ꢁ3), com-
pared with that of a MeOH solution of 3 (ꢀf ¼ 45:6 ꢃ 10ꢁ3),
as shown in Table 1. On the other hand, the fluorescence quan-
tra were observed at 40%LL of SbTPP–SSA composites and
normalized at 620 nm. Interestingly, the shape of the fluores-
cence spectrum of 1a–SSA was very close to that of 1a in
solution, whereas another SbTPP–SSA composite gave more
broading fluorescence spectra, probably due to the aggregation
of SbTPP into SSA.
Discussion
The results of an XRD analysis revealed that the structure of
an axial ligand at SbTPP serves a crucial role to form a layered
structure in the SbTPP–SSA composite. The 1–SSA and 3–
SSA composites having a cationic part and an OH group as
tum yield of 1a–SSA was determined to be ꢀf ¼ 29:3 ꢃ 10ꢁ3
.
Figure 9 shows the fluorescence spectra of powdered SbTPP–
SSA composites in the solid state by using CLSM. These spec-

T. Shiragami et al.
Bull. Chem. Soc. Jpn., 78, No. 12 (2005) 2255
(B)
%LL = 20
%LL = 40
%LL = 20
(A)
%LL = 40
%LL = 60
%LL = 60
%LL = 100
%LL = 100
4600
4000
3000
2000
1700
4600
4000
3000
2000
1700
Wavenumber / cm-1
Wavenumber / cm-1
Fig. 6. IR spectra of (A) 2a–SSA and (B) 4–SSA composite at various %LL.
1.5
1a
100
80
without SSA
%LL
10
1
0.5
0
20
40
60
60
80
100
40
20
350
400
450
500
Wavelength / nm
2
1.5
1
2a
0
20
40
60
80
100
without SSA
%LL
%LL
10
20
Fig. 7. Plots of %LL vs ratio of peak area of O–H band at
%LL with that of naked SSA as standard; 1a (– –), 2a
(– –), 3 (– –), and 4 (– –).
40
60
0.5
0
80
an axial ligand can take a layered structure, respectively. An
evaluation of the interlayer distance of 1–SSA and 3–SSA
composites by XRD measurements can provide information
on the orientation of 1 and 3 into SSA. The interlayer distance
(1.03 nm) for the 1a–SSA composite is closed to the thickness
(0.94 nm) of 1a for the axial ligand direction estimated by a
PM3 calculation, as shown in Table 1. Also, the PM3 calcula-
tion of 1b, having a longer chain as an axial ligand, gave a
folded structure of an axial ligand chain as a most stable struc-
ture, resulting that the thickness of 1b for an axial direction
was estimated to be 0.86 nm. This value is almost the same
100
350
400
450
500
Wavelength / nm
Fig. 8. Absorption spectra of 1a and 2a in aqueous colloi-
dal SSA solution at various %LL.
as the interlayer distance (0.97 nm) of the 1b–SSA composite.
These results strongly suggest that 1 should be intercalated in-
to the SSA interlayer space at high %LL, and that the orienta-

2256 Bull. Chem. Soc. Jpn., 78, No. 12 (2005)
Structure of Cationic SbTPP/Clay Composites
Table 1. Characteristic Data of SbTPP–SSA Composites
Soret band
(ꢂmax/nm)
Fluorescence
(ꢂmax/nm)
ꢀf
/10ꢁ3
Thickness
/nma)
Interlayer
Distance/nm
SbTPP
%LL =
0
20
80
0
20
0b)
80
1a
1b
2a
2b
3
418
419
419
418
417
417
431
436
421 442c)
436
419 443c)
430 445c)
430 445c)
595
595
595
595
594
594
602
602
602
602
600
600
50.0
d)
29.3
d)
0.94
0.86
0.86
0.86
0.42e)
0.73
1.03
0.97
—
431
431
431
430
431
—
51.2
—
21.4
d)
d)
—
—
—
45.6
48.8
4.5
6.4
1.09f)
—
4
a) Estimated by PM3 calculation for axial direction. b) Measured in methanol. c) Soret band was splitted. d) Not mea-
sured. e) Determined by X-ray crystallographic analysis (See Ref. 36). f) Two SbTPP molecules were intercalated into
a interlayer of SSA (See Ref. 37).
1.5
1
ture of 1–SSA and 3–SSA through the coagulation process
from the colloidal SbTPP–SSA composites. This speculation
is supported by the following results: (1) The value of the ex-
panded interlayer distance (1.03 nm) of SSA was not paradox-
ical with our proposition as for taking the parallel position for
SSA sheets on the orientation of 1a ring, as describe above, (2)
the Soret band of 1a showed neither a larger broadening nor
splitting in a colloidal SSA solution, (3) the shape of the fluo-
rescence spectrum of 1a into SSA under a powdered state was
very close with that of 1a obtained in a solution, and (4) an ex-
treme decrease of the fluorescence quantum yield in the 1a–
SSA composite was not observed, compared with much fluo-
rescence quenching, such as in the 3–SSA composite.
3
4
0.5
0
1a
2a
600
650
Wavelength / nm
700
Since there is a relationship between the crystal structure of
SbTPP–SSA composites and the disappearance of the O–H
band with an increase of %LL, the presence of adsorbed water
molecules can be operated for forming a layer structure of
SbTPP–SSA composites. A cationic part and a hydroxy group
on an axial ligand operates effectively to form a layer structure
in 1–SSA and 3–SSA composites.
Fig. 9. Fluorescence spectra of the powdered SbTPP–SSA
complexes by confocal laser scanning fluorescence micro-
scope. These spectra were measured at 40%LL and nor-
malized at 620 nm.
tion of the porphyrin plane should be almost parallel to the
SSA sheets. If 1 is oriented vertically to the SSA sheets, the
expanded interlayer distance should be about 1.75 nm.
Conclusion
The information on the orientation of 1 into the SSA inter-
layer space can also be estimated from the shape of the absorp-
tion and fluorescence spectra. Generally, it is well known that
the absorption band of dye molecules adsorbed or intercalated
into clay change to some broadening or splitting band, owing a
strong ꢀ–ꢀ interaction stemming from a compact aggregation
of dye molecules with each other.40–43 In fact, larger broaden-
ing and splittings of the Soret band were observed in each col-
loidal SSA solution containing 2–4. These spectral changes
clearly indicate the aggregation of 2–4 onto the SSA surface,
or in the interlayer space of SSA, as has been reported for an-
other dye–clay system.7–20 Fluorescence analysis on CLSM is
very convenient for probing the orientation or aggregation of
dye intercalated into clay under the powdered state, not the
colloidal state. As shown in Fig. 9, the abnormal shape of
the fluorescence spectra of 2–SSA and 4–SSA composites un-
der the powdered state also shows the aggregation of 2–4 into
SSA. However, the 1–SSA system generated a quite different
phenomenon concerning the behaviors of 1.
According to Fig. 10, nano-like SSA sheets are loosely
aggregated in the colloidal state.44 The coagulation from the
loose aggregates can be accelerated by the adsorption of
SbTPP. In fact, the rate of coagulation strongly depended on
%LL of SbTPP, i.e. the coagulation of colloidal SbTPP–SSA
composites at low %LL (10–40%) required several days in
aqueous solution, whereas the colloidal SbTPP–SSA compo-
sites at high %LL (80–100%) coagulated required several
hours in aqueous solution. These phenomena show that the co-
agulation process can be induced by a strong interaction be-
tween the axial ligand of SbTPP adsorbed on the first SSA
sheet with the anionic site on the second SSA sheet. The inter-
action between an axial ligand part with second anionic SSA
sheets should be regarded as a Coulombic attractive force
for 1–SSA composites or a hydrogen-bonding interaction for
the 3–SSA composite, respectively. Especially, the hydro-
gen-bonding networks formed by water molecules around the
axial ligand should be a crucial factor for taking the more sta-
ble layer structure during the coagulation process for the 3–
SSA composite.
We proposed that 1 should exist in a non-aggregated state in
1–SSA composite, where their porphyrin rings could be locat-
ed in an alternative orientation, such as head to tail. Figure 10
shows a plausible process for the formations of a layered struc-
Since 1 has a cationic part on an axial ligand, the strong
Coulombic attractive force with anionic SSA sheets can be at-

T. Shiragami et al.
Bull. Chem. Soc. Jpn., 78, No. 12 (2005) 2257
electrostatic force
RO
OR
MeO
N
RO
O
O
MeO
O
OMe
O
OMe
O
MeO
N
coagulation
OR
N
N
N
N
coagulation
1a
RO
OR
O
N
OR
MeO
O
RO
O
O
O
N
O
N
N
OMe
N
OR
OMe
OMe
OMe
RO
OMe
N
O
layer structure
OMe
OR
OR
RO
OR
RO
RO
OR
RO
colloidal state
hydrogen-bonding network
coagulation
H
H
HO
O
OH
OH
OH
O
H
H
H
H
H
OH
H
H
3
H
O
HO
H
O
O
coagulation
coagulation
OH
O
OH
O
OH
O
4
O
H
H
H
H
H
HO
H
O
OH
H
O
OH
HO
H
HO
HO
H
H
OH
HO
O
H
O
H
HO
OH
OH
H
OH
H
H
H
OH
H
O
HO
layer structure
MeO
OH
O
H
OMe
H
water molecules
MeO
OMe
MeO
OMe
MeO
OMe
OMe
N
O
OMe
OMe
OMe
OH
OH
OMe
MeO
MeO
OMe
4 =
3
1a =
MeO
OMe
MeO
MeO
OMe
SSA =
amorphous structure
Fig. 10. Plausible process for the formation of layer structure through the coagulation of collidal SbTPP–SSA sheets and the sup-
ports of some water molecules around axial ligand.
(1990).
12 H. Kaneyama, H. Suzuki, and A. Amano, Chem. Lett.,
1998, 1117.
13 E. P. Giannelis, Chem. Mater., 2, 627 (1990).
14 I. Ukrainczyk, M. Chibwe, T. J. Pinnavaia, and S. A. Boyd,
J. Phys. Chem., 98, 2668 (1994).
15 S. Bonnet, C. Forano, A. De Roy, and J. P. Besse, Chem.
Mater., 8, 1965 (1996).
16 M. E. Perez-Bernal, R. Ruano-Casero, and T. J. Pinnavaia,
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tributed to suppressing the aggregation of 1 with each other on
the SSA surface or in the SSA interlayer. Accordingly, it was
clarified that the change of an axial ligand structure can affect
not only the coagulation process for the formation of a crystal
structure from colloidal SbTPP–SSA particles, but also an ori-
entation and aggregation of SbTPP into SSA.
This research was supported by a Grand-in-Aid for Scien-
tific Research (Nos. 16550127 and 15033258, Scientific Re-
search in Priority Areas 417) from the Ministry of Education,
Culture, Sports, Science and Technology. We are grateful to
Mr. Kukizaki and Ms. Akazaki (Miyazaki Prefecture Industrial
Technology Center) for XRD measurements.
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