Efficient energy and electron transfer between donor and acceptor chromophores in aluminophosphate hybrid materials

Article abstract of DOI:10.1002/jccs.201000078

The first organic-inorganic hybrid materials (OIHMs) having one or a combination of two chromophores in different ratios are obtained from the aryl phosphonic acid and aluminum lactate via sol gel process. The structures of these OIHMs are analyzed by the ²⁷Al and ³¹P NMR. The fluorescence resonance energy transfer (FRET) as well as photoinduced electron transfer (PET) between donor and acceptor chromophores in these hybrid materials have been investigated and the efficiencies can be up to 97 and 93%, respectively.

Full text of DOI:10.1002/jccs.201000078

Journal of the Chinese Chemical Society, 2010, 57, 539-546
539
Efficient Energy and Electron Transfer between Donor and Acceptor
Chromophores in Aluminophosphate Hybrid Materials
Chih-Yuan Loa (
Long Zhangb (
), Chih-Hsien Chena (
), Tsong-Shin Limc (
), Tim W. T. Tsaia (
), Wunshain Fannd (
),
),
Jerry C. C. Chana* (
) and Tien-Yau Luha* (
)
aDepartment of Chemistry, National Taiwan University, Taipei 106, Taiwan, R.O.C.
bShanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211,
Shanghai 201800, P. R. China
cDepartment of Physics, Tung Hai University, Taichung 407, Taiwan, R.O.C.
dInstitute of Atomic and Molecular Science, Academia Sinica, Taipei 106, Taiwan, R.O.C.
The first organic-inorganic hybrid materials (OIHMs) having one or a combination of two chromo-
phores in different ratios are obtained from the aryl phosphonic acid and aluminum lactate via sol gel pro-
cess. The structures of these OIHMs are analyzed by the 27Al and 31P NMR. The fluorescence resonance
energy transfer (FRET) as well as photoinduced electron transfer (PET) between donor and acceptor
chromophores in these hybrid materials have been investigated and the efficiencies can be up to 97 and
93%, respectively.
Keywords: FRET; PET; Sol gel; Organic-inorganic hybrid materials; Aluminum phosphate
gels.
INTRODUCTION
The sol gel technique offers an important process to
glasses.6-8 Structurally, aluminum phosphate gels or glasses
can be considered to be isoelectronic to silicon-based ana-
logues. It is interesting to compare the environment gener-
ated by the alumina-phosphate network with those of the
silica-based materials. Incorporation of organic chromo-
phores covalently bonded to phosphate matrices has been
briefly explored.8 Since arylphosphonic acid can readily be
prepared from the corresponding aryl halides.9 We now
wish to report the first OIHMs obtained from the aryl phos-
phonic acid and aluminum lactate via sol gel process and
their applications in fluorescence resonance energy trans-
fer (FRET) investigations.
bridge solid state and molecular chemistry.1 Amalgamation
of organic moieties into the metal oxide matrix by hydro-
lytic polycondensation has been shown to be a versatile
protocol leading to the formation of homogeneous or-
ganic-inorganic hybrid materials (OIHMs).1,2 Materials
and devices are thus fabricated so that the individual units
are engineered down to the nanometric scale. Silicon-based
hybrid materials have been extensively studied because of
the accessibility of both organic and inorganic molecular
precursors.1,2 Recently, we have shown that silicon-based
OIHMs having different kinds of organic chromophores
can serve as light harvesting models to mimic the natural
process of energy transfer3,4 and be used in photovoltaic
applications.4,5 Glass or mesoporous materials derived
from oxides of main group elements other than silicon are
also well documented.6-8 For example, a novel sol-gel route
based on aluminum lactate and sodium polyphosphate so-
lution has recently been developed to prepare homoge-
neous transparent sodium aluminum phosphate gels and
RESULTS AND DISCUSSION
Synthesis
Nickel-catalyzed coupling of 1 with (EtO)3P gave the
corresponding diphosphonate 2 which was treated with
Me3SiBr to afford bisphosphonic acids 3 (Scheme I).9
OIHM A’s prepared from different ratios of Al(lact)3 and
3a at pH 5 were analyzed by solid-state NMR. Similarly,
Dedicated to the memory of Professor Wunshain Fann (1961–2008).
* Corresponding author. E-mail: tyluh@ntu.edu.tw

540 J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010
Lo et al.
Table 1. The molar compositions of OIHM A’s, B’s, C’s and D’s
Scheme I
Al(lact)3
3a
3b
3c
3d
3e
A1
A2
A3
A4
A5
B1
B2
B3
B4
B5
B6
B7
C1
C2
D1
D2
2
1
1
4
3
1
1
1
1
1
1
1
4
4
4
4
9
3
1
3
1
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
0.05
0.95
1
0
0.5
0.5
0
1
0.5
0.5
[–OP(=O)(Ar)O–]2–x} and there might be substantial
amount of [Al(lact)3]. When the P/Al ratio was increased to
3/2, {Al(lact)(H2O)x[–OP(=O)(Ar)O–]4–x} would become
the major species. Overall, the relative peak intensity of
{Al(lact)(H2O)x[–OP(=O)(Ar)O–]4–x} may increase as the
P/Al ratio increases. The observation is consistent with the
reaction between Al(lact)3 and phosphoric acid.6,7 Interest-
ingly, {Al(lact)(H2O)x[–OP(=O)(Ar)O–]4–x} would remain
to be the major species for the A1, which has the highest
P/Al ratio in the series. As can be seen from Fig. 1, the rela-
tive amount of {Al(H2O)x[–OP(=O)(Ar)O–]6–x} does not
increase with the P/Al ratio in OIHM A’s. It is striking to
note that these results are different from those obtained in
sodium aluminum phosphate glasses without organic chro-
mophore.6-8
Fig. 2 shows the 31P MAS NMR spectra measured for
OIHM A’s. The 31P peaks at 14, 3, and -4 ppm were as-
signed to the phosphorus species of [HOP(=O)(Ar)OH],
[Al–OP(=O)(Ar)OH], and [Al–OP(=O)(Ar)O–Al], re-
spectively, where Ar is defined previously. The presence
of free hydroxyl group in these hybrid materials was con-
firmed by the strong and broad infrared absorption around
3450 cm-1. For the A5 with the lower P/Al ratio (2/3), the
amount of [Al–OP(=O)(Ar)OH] and [Al–OP(=O)(Ar)O–
Al] were comparable, and the contribution from [HOP-
(=O)(Ar)OH] would be no more than 6%. As expected,
[Al–OP(=O)(Ar)OH] became the dominant species in A4
when the P/Al ratio was increased to be 3/2. Because the
formation of Al-O-Al linkage might be dissimilar under
OIHM B’s, C’s, and D’s were prepared from different ra-
tios of Al(lact)3 and bisphosphonic acids 3b-d at pH 6. The
compositions of OIHM A-D’s are listed in Table 1.
Solid State NMR of A’s
The 27Al MAS NMR spectra of the OIHM A’s mea-
sured at 104.3 MHz are shown in Fig. 1a. The line shapes of
the 27Al MAS spectra were quite similar to those measured
for the glass materials prepared from Al(lact)3 and phos-
phoric acid.6,7 According to spectral deconvolution, the
27Al MAS spectrum of OIHM A4 may contain four compo-
nent peaks positioned at 19, 3, -8, and -18 ppm, which were
assigned to the moieties of [Al(lact)3], {Al(lact)2(H2O)x-
[–OP(=O)(Ar)O–]2–x}, {Al(lact)(H2O)x[–OP(=O)(Ar)O–]4–x},
and {Al(H2O)x[–OP(=O)(Ar)O–]6–x}, respectively, where
Ar represents the –C6H4PO(=O)O– module which could
form covalent bond with another aluminum species in these
OIHM A’s (Fig. 1b).7 Water ligands (x equivalents) would
be incorporated to accommodate each of hexacoordinate
aluminum species. For the sample with the lowest P/Al ra-
tio in A5, the major species would be {Al(lact)2(H2O)x-

Aluminophosphate Hybrid Materials
J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010 541
different reaction conditions, the bridging species such as
[Al–O(=O)(OH)PC6H4P(=O)(OH)O–Al] would be re-
sponsible for the formation of a giant structural network in
A’s. As shown in Fig. 2, because of higher P/Al ratios in A1,
A2, and A3, the contribution of the free phosphonic acid
species [HOP(=O)(Ar)OH] would increase accordingly.
Structurally, both 27Al and 31P MAS NMR spectra suggest
the formation of Al–O–P bonding in OIHM A’s and those
are consistent with the network structures in these hybrid
materials.
FRET in OIHM B’s
Chromophores in 3b and 3c were employed for the
FRET investigations of the OIHM B’s. The photophysical
properties of monomers 3b and 3c are summarized in Table
2.
The absorption and emission spectra of OIHM B’s are
shown in Fig. 3. As expected, the intensity of the absorp-
tion around 400 nm (lmax of the chromophore from 3c) in-
creased with increasing molar fraction of 3c for the prepa-
ration of the OIHM films. It is known that efficient FRET
between biphenyl and terphenylene-divinylene chromo-
phores in silicon-based hybrid materials would readily oc-
cur.3 Emission spectra (lex = 300 nm) of the OIHM B’s
films are shown in Fig. 3b. The donor emission was ob-
served around 400 nm in B1 whereas only the emission
from the acceptor chromophore around 480-490 nm was
observed in hybrid thin films B2-B6. It is noteworthy that
the emission intensities of acceptor increased with the in-
creasing donor molar fractions in these hybrid systems. Al-
though the acceptor chromophores in these hybrid films
may also absorb around 300 nm, the complete absence of
emission from the donor chromophore, even with rela-
tively high donor molar fractions (e.g. B2 or B3), may indi-
cate that FRET might readily take place and exhibit an an-
Fig. 1. (a) 27Al MAS NMR spectra of OIHM A’s as a
function of P/Al ratio. (b) 27Al MAS spectrum
of OIHM A4 (P/A = 3/2) after spectral decon-
volution. The solid and dotted traces represent
the experimental and deconvoluted spectra, re-
spectively. Other traces represent the individ-
ual components of the deconvoluted spectrum.
Fig. 2. 31P MAS NMR spectra of OIHM A’s as a func-
tion of P/Al ratio.

542 J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010
Lo et al.
Table 2. Photophysical properties and frontier orbital energies of
3b-d
HOMOd LUMOe
a
lmax
lem
V1/2
E0-0
(nm)
(nm)
(V)
(eV)
(eV)
(eV)
3b
3c
3d
3e
265
404
370
388
448
445
0.6
0.5
0.4
2.9b
3.0b
4.0c
-5.4
-5.3
-5.2
-2.5
-2.3
-1.2
a The first oxidation potentials were obtained by cyclic
voltammetry, and the potentials were referred to the
Cp2Fe/Cp2Fc+ couple.
b The zero-zero transition energy values were determined by the
cross point of absorption and emission spectra.
c The zero-zero transition energy was determined by absorption
edge of 3d.
d HOMO energy values were obtained from first oxidation
potential values (V1/2) and calculated by taking the HOMO
energy value of ferrocene to be -4.8 eV as standard.
e LOMO = HOMO + E0-0
.
tenna effect.3,4
As shown in Fig. 3b, efficient energy transfer without
leak of donor emissions was observed when the donor-to-
acceptor ratios ranged from 80 : 20 to 20 : 80. However,
when the molar fraction of the donor was larger than 0.9,
the emission from the donor chromophore started to emerge.
Such leak of donor emission may provide useful informa-
tion on the estimation of energy transfer efficiency in these
hybrid systems. It is noteworthy that similar leak has been
observed in silicon-based OIHMs.3 We have therefore ex-
amined the detailed photophysical properties of these ma-
terials. The ratio of donor 3b to acceptor 3c was chosen to
be 95 : 5 (OIHM B7) in aluminophosphate gel thin films.
Time-resolved fluorescence spectroscopy was employed to
study the fluorescence lifetime and the rate of energy trans-
fer from donor to acceptor in these hybrid materials. The
time-resolved fluorescence spectra of OIHM B7 were mea-
sured (Fig. 4), and the efficiency of FRET (FEN) were esti-
mated by following two equations.3
Fig. 3. (a) Absorption and (b) emission spectra (lex=
300 nm) of hybrid materials at different donor
and acceptor ratios.
FEN = kET/(1/td)
kEN = 1/td – 1/t0
(1)
(2)
where td is the observed fluorescence decay lifetime of do-
nor moiety in OIHM B’s, and t0 is the fluorescence lifetime
of donor in the absence of acceptor moiety. The to was ob-
tained by monitoring the fluorescence decay lifetime of
OIHM B1, and the fluorescence lifetime of donor moiety
Fig. 4. Time-resolved fluorescence decay profiles of
B1 (circle) and B7 (square) monitored at 370-
390 nm.

Aluminophosphate Hybrid Materials
J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010 543
was 2200 ps. Biexponential fitting was used, and then, the
fluorescence lifetimes were 180 ps and 1970 ps. The shorter
lifetime may due to FRET from donor to acceptor moieties
in B7, and the longer lifetime may arise from the decay of
the donor chromophores without FRET in aluminophos-
phate gel matrices. Based on eqs. 1 and 2, the efficiency of
FRET in these hybrid materials (donor/acceptor = 95 : 5)
was 92%. Similarly, the efficiency of FRET in OIHMs B2-5
could also be estimated by eqs. 1 and 2, in which the td’s
were shorter than instrument limitation (1 ps), and thus, the
efficiencies were larger than 97%. These systems have pro-
vided comparable antenna effect and efficiency of energy
transfer to those of silicon-based OIHMs and related sys-
tems.3,10 The covalent bonding between energy donor and
acceptor might really enhance the efficiency of FRET.
in hybrid matrices. The rates of PET (ket) and correspond-
ing efficiencies (Fet) in OIHM C2 and D2 were estimated by
eqs 3 and 4.11a
ket = t-1 -t-s 1
–1
Fet = ket/t
(3)
(4)
As shown in Table 3, C2 (15 ps) and D2 (34 ps) exhib-
ited much shorter lifetimes than those of C1 and D1. Pre-
sumably PET between donor and acceptor chromophores
may take place in these hybrid materials. Although the free
energy changes of the PET processes in OIHMs might be
estimated because the redox potential of the quasi solid
films were intricate, the relative rates of these PET pro-
cesses were in the same order as those in polymer systems11
and related silicon-based OIHMs owning similar donor and
Electron Transfer in OIHM C’s and D’s
OIHM C’s and D’s were employed for photoinduced
electron transfer (PET) processes. The photophysical and
electrochemical properties of phosphonic acids 3c-e were
measured and the corresponding frontier orbital energies
were estimated. The results are summarized in Table 2.
Based on the relative frontier orbital energies, it is envi-
sioned that chromophores derived from 3c and 3d would be
electron acceptors and 3e would be electron donor. The
PET may take place between chromophores derived from
3c and 3e and from 3d and 3e in these hybrid materials
upon irradiation at lmax of the corresponding electron ac-
ceptor.
The emission spectra of OIHM C1 and C2 are shown
in Fig. 5a. It is noteworthy that the emission from 3c was ef-
ficiently quenched in the presence of the ferrocene chro-
mophore in OIHM C2. In this regard, the PET process
might be triggered from the HOMO of 3e (electron donor)
to the HOMO of 3c (electron acceptor) in OIHM C2 after
light irradiation. Similarly, the emission spectrum of OIHM
D1 showed characteristic emission band of chromophore in
3d, and the emission intensity was significantly reduced in
OIHM D2 (Fig. 5b) attributed to the PET from the HOMO
of 3e to the HOMO of 3d. Time-resolved fluorescence
spectra were employed to estimate the rates and efficien-
cies of PET in C’s and D’s, in which the lifetime decay pro-
files of acceptor moieties were monitored (Fig. 6). The ob-
served fluorescence lifetimes of OIHMs C1 and D1 (ts)
were 750 and 350 ps, respectively, and those represented
the intrinsic fluorescence decay lifetimes of chromophorese
Fig. 5. The emission spectra of (a) OIMH C1 (solid)
and C2 (dash), and (b) OIHM D1 (solid) and D2
(dash).

544 J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010
Lo et al.
Table 3. The fluorescence lifetimes (t), rates (ket), and
efficiencies (Fet) of OIHM C’s and D’s
t (ps)
ket (s-1)
Fet
C1
C2
D1
D2
750
015
350
34
-
-
6.2 ´ 1010
0.93
-
-
2.6 ´ 1010
0.90
90:10. The PET processes also occurred efficiently in these
OIHMs.
EXPERIMENTAL SECTTION
General
Absorption spectra were measured with a Hitachi
U-3310 spectrophotometer and emission spectra with a
Hitachi F-4500 fluorescence spectrophotometer. All NMR
measurements were carried out at ambient temperature on
Bruker DSX-400 and DSX-500 spectrometers, equipped
with 4-mm and 2.5-mm MAS-NMR probes. At the two
field strengths of 9.4 Tesla and 11.7 Tesla, the resonance
frequencies were, respectively, 104.3 and 130.3 MHz for
27Al, and 161.9 and 202.5 MHz for 31P. The sample was
confined to the middle region of the rotor volume using
Teflon spacers. Typically, the recycle delay for 27Al and 31
P
MAS spectra were 1 s and 60 s, respectively. Unless stated
otherwise, magic-angle spinning (MAS) spectra were
measured at a spin rate of 10 kHz without proton decoup-
ling. The 27Al and 31P NMR chemical shifts are referenced
to 1 M Al(NO3)3 solution and 85% H3PO4, respectively.
Line shape deconvolution was carried out by the package
DMfit2003.12 In time-resolved fluorescence experiments,
a mode-locked Ti:sapphire laser (wavelength, 820 nm;
repetition rate, 76 MHz; pulse width, < 200 fs) passed
through an optical parametric amplifier. The fluorescence
of sample was reflected by a grating (150 g/mm; BLZ: 300
nm) and detected by an optically triggered streak camera
(Hamamatsu C5680) with a time resolution of about 0.3 ps.
The pH of these solutions was adjusted with freshly pre-
pared NaOH(aq) and controlled within 0.1 units by monitor-
ing with a pH meter (METTLER TOLEO pH meter S20).
Biphenyl diphosphonate (2b)
Fig. 6. Time-resolved fluorescence decay profiles of
(a) C1 (circle) and C2 (square) monitored at
470-490 nm; (b) D1 (circle) and D2 (square)
monitored at 480-500 nm.
acceptor pairs.3-5
CONCLUSIONS
We have demonstrated the first OIHMs obtained from
the aryl phosphonic acid and aluminum lactate via sol gel
process. The structure of organic-moieties containing alu-
minophosphate gel has been characterized by solid state
27Al and 31P NMR. The results show that the octahedrally
coordinated aluminum moieties such as {Al(lact)2(H2O)x-
[–OP(=O)(Ar)O–]2–x}, {Al(lact)(H2O)x[–OP(=O)(Ar)O–]4–x},
and {Al(H2O)x[–OP(=O)(Ar)O–]6–x} would contribute to
the formation of the hybrid network of the OIHM. Efficient
energy transfer and PET processes have been observed
both in steady state and kinetic measurements. The effi-
ciencies of FRET were estimated higher than 97% for the
OIHMs with donor to acceptor ratios ranging from 10:90 to
Under N2 atmosphere, a mixture of the 1b (310 mg,
1.0 mmol) and NiCl2 (24 mg 0.2 mmol) was stirred at 150
°C for 30 min. P(OEt)3 (1.0 g, 6.0 mmol) was slowly added
over a period of 4 h, and the mixture was stirred at 150 °C
for another 8 h. cooled to rt, poured into brine and extracted

Aluminophosphate Hybrid Materials
J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010 545
with EtOAc. The organic layer was dried (MgSO4) and
evaporated in vacuo to give the residue which was chro-
matographed on silica (ether) to afford 2b (540 mg, 63%):
mp 71-72 °C (lit. 68-69 °C); 1H NMR (CDCl3, 400 MHz) d
1.35 (t, J = 7.0 Hz, 12 H), 4.08-4.21 (m, 8 H), 7.67-7.70 (m,
4 H), 7.87-7.92 (m, 4 H); 13C NMR (CDCl3, 100 MHz) d
16.5 (d, J = 6.0 Hz), 62.2 (d, J = 5.3 Hz), 127.2 (d, J = 15.2
Hz), 127.8 (d, J = 187.7 Hz), 132.3 (d, J = 10.6 Hz), 143.7;
31P NMR (CDCl3, 161 MHz): d 19.7; IR (KBr) n 2983,
2929, 2901, 1603, 1441, 1387, 1245, 1134, 1049, 1023,
966, 792, 767, 703, 564, 536 cm-1; HRMS (EI) (M+1) calcd
for C20H29O6P2 427.1439, found 427.1439.
130.5, 136.9; 31P NMR (DMSO-d6, 161 MHz): d 18.0;
HRMS (EI): calcd for C6H9O6P2 238.9874; found 238.9879.
Biphenyl diphosphonic acid (3b)
In a manner similar to that described above, 2b (0.21
g, 0.5 mmol) was converted into 3b (0.19 g, 95 %): mp
303-304 °C; 1H NMR (DMSO-d6, 400 MHz) d 7.74-7.78
(m, 8H); 13C NMR (DMSO-d6, 100 MHz) d 127.2 (d, J =
14.5 Hz), 131.8 (d, J = 9.8 Hz), 134.0 (d, J = 180.9 Hz),
142.2; 31P NMR (DMSO-d6, 161 MHz) 18.7; IR (KBr) n
3426, 2245, 2122, 1650, 1049, 1026, 995, 824, 764, 627
cm-1; HRMS (EI) (M+1) calcd for C12H13O6P2 315.0187,
found 315.0182.
Tetraethyl diphosphonate (2c)
Tetraethyl diphosphonic acid (3c)
In a manner similar to that described above, a mixture
of 1c13 (500 mg, 1.0 mmol), NiCl2 (24 mg, 0.2 mmol) and
P(OEt)3 (1.0 g, 6.0 mmol) was converted into 2c (245 mg,
40%): mp 167-168 °C; 1H NMR (CDCl3, 400 MHz): d 1.35
(t, J = 7 Hz, 12H), 3.95 (s, 6H), 4.08-4.18 (m, 8H), 7.13 (s,
2H), 7.14 (d, J = 16.2 Hz, 2H), 7.58 (d, J = 16.2 Hz, 2H),
7.63 (dd, J = 8.5, 3.8 Hz, 4H), 7.89 (dd, J = 12.6, 8.5 Hz,
4H); 13C NMR (CDCl3, 100 MHz) d 16.8, 56.6, 62.4,
109.4, 125.8, 126.6, 126.7, 127.8, 128.1, 132.3, 141.8,
151.8; 31P NMR (CDCl3, 161 MHz): d 20.3; HRMS (EI)
(M+1, C32H41O8P2) calcd 615.2277; found 615.2284.
Terthiophene diphosphonate (2d)
In a manner similar to that described above, 2c (0.240
g, 0.391 mmol) was converted into 3c (0.176 g, 90%): mp
1
223-224 °C; H NMR (DMSO-d6, 400 MHz): d 3.90 (s,
6H), 7.36 (s, 2H), 7.38 (d, J = 16.4 Hz, 2H), 7.51 (d, J =
16.4 Hz, 2H), 7.60-7.70 (m, 8H); 13C NMR (DMSO-d6,
100 MHz): d 55.9, 109.0, 123.6, 125.3, 125.5; 31P NMR
(DMSO-d6, 161 MHz): d 18.7; HRMS (EI) (M+1, C24H25O8P2)
calcd 503.1025; found 503.1022.
Terthiophene diphosphonic acid (3d)
In a manner similar to that described above, 2d (200
mg, 0.45 mmol) was converted into 3d (180 mg, 91%): mp
1
173-174 °C (dec.); H NMR (DMSO-d6, 400 MHz) d
In a manner similar to that described above, a mixture
of 1d13 (410 mg, 1.0 mmol), NiCl2 (24 mg, 0.2 mmol) and
P(OEt)3 (1.0 g, 6.0 mmol) was converted into 2d (180 mg,
35%): mp 167-168 °C; 1H NMR (CDCl3, 400 MHz) d 1.37
(t, J = 7.2 Hz, 12H), 4.13-4.21 (m, 8H), 7.19 (s, 2H), 7.22
(t, J = 3.6 Hz, 2H), 7.56 (dd, J = 9.4, 3.6 Hz, 2H); 13C NMR
(CDCl3, 100 MHz) d 16.4 (d, J = 6.1 Hz), 62.8 (d, J = 5.3
Hz), 124.5 (d, J = 15.7 Hz), 125.8, 126.5 (d, J = 209.0 Hz),
136.0, 137.4 (d, J = 11.4 Hz), 144.3 (d, J = 8.3 Hz); 31P
NMR (CDCl3, 161 MHz): d 12.2; IR (KBr) n 3072, 2980,
2929, 2894, 1432, 1251, 1159, 1096, 1045, 1017, 969, 798,
580 cm-1; HRMS (EI) (M+1) calcd for C22H27O6P2S3
521.0445, found 521.0440.
7.37-7.40 (m, 6H); 13C NMR (DMSO-d6, 100 MHz) d
125.4 (d, J = 16.0 Hz), 126.7, 134.9 (d, J = 195.3 Hz), 135.2
(d, J = 9.9 Hz), 135.7, 141.3 (d, J = 6.8 Hz); 31P NMR
(DMSO-d6, 161 MHz) d 10.3; IR (KBr) n 3436, 2252,
2128, 1650, 1045, 1023, 995, 824, 764 cm-1; HRMS calcd
for C24H25O8P2 407.9115, found 407.9107.
Preparation of Bulk Samples and Thin Films
In a typical preparation, aluminium phosphate gel
samples containing a combination of one or two kinds of
organic group were prepared via the sol-gel route in aque-
ous solutions. The Al(lact)3 (0.1 M) solution was prepared
by dissolving Al(lact)3 in water, and the diphosphonic acid
compound (0.1 M) solution was prepared by dissolving
diphosphonic acid compound in water. The pH of the pre-
cursor solutions was adjusted with NaOH (0.01 M). The
diphosphonic acid solution was added into Al(lact)3 solu-
tion, according to the desired P/Al molar ratio and the do-
nor/acceptor ratio in the mixture, to afford the correspond-
ing sol solution which was spin-coated on a quartz plate.
1,4-Phenylenediphosphonic acid (3a)
Under N2 atmosphere, to a CH2Cl2 (5 mL) solution of
2a10a (0.30 g, 0.86 mmol) was added bromotrimethylsilane
(1.53 g, 10 mmol) dropwise by syringe pump over a period
of 1 min. The mixture was stirred at rt for 4 h, cooled to 0 °C
and quenched with water. The insoluble material was fil-
tered. Removal of water in vacuo to afford 3a (0.19 g,
91%): mp 265-266 °C; 1H NMR (DMSO-d6, 400 MHz): d
7.60-7.95 (brs, 4H); 13C NMR (DMSO-d6, 100 MHz): d
ACKNOWLEDGEMENTS
We thank the National Science Council and National

546 J. Chin. Chem. Soc., Vol. 57, No. 3B, 2010
Lo et al.
6. Zhang, L.; Chan, J. C. C.; Eckert, H.; Helsch, G.; Hoyer, L.
P.; Frischat, G. H. Chem. Mater. 2003, 15, 2702.
TaiwanUniversity for financialsupport. Thanks are also
due to Professor Hellmut Eckert for his generoussupport.
The NMR measurements were carried out at the University
of Münster Solid State NMR facility supported by the
Ministerium für Wissenschaft und Forschung Nordrhein-
Westfaelen.
7. Zhang, L.; Echert, H. Solid State Nucl. Magn. Reson. 2003,
26, 132.
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