Gallium(III) organophosphonate adducts with the bidentate amines 2,2′-bipyridyl and 1,10-phenanthroline

Article abstract of DOI:10.1016/S0020-1693(01)00471-6

A number of gallium(III) organophosphonates form adducts with the bidentate amines 2,2′-bipyridyl and 1,10-phenanthroline. These adducts contain a 1:2:1 molar ratio of metal/phosphorus/amine and have the proposed formulations Ga(O₃PR)(O₂P(OH)R)(C₁₀H₈N ₂)·H₂O and Ga(O₃PR)(O₂P(OH)R)(C₁₂H₈N ₂)·H₂O (where R = CH₃, C₆H₅ and CH₂C₆H₅; C₁₀H₈N₂ is 2,2′-bipyridyl and C₁₂H₈N₂ is 1,10-phenanthroline). Unlike the parent gallium(III) organophosphonates, which conform to the general formula Ga(OH)(O₃PR)·xH₂O (x = 0 or 1), the amine adducts lack the hydroxo group, but contain the organophosphonate ligand in the partially as well as fully deprotonated forms. All compounds were isolated from aqueous solutions as monohydrates, with the exception of the bipyridyl adduct of gallium(III) phenylphosphonate, which is anhydrous. TGA measurements suggest that for the hydrates, the water molecule is not coordinated to the metal. The bipyridyl adducts of gallium(III) phenylphosphonate and gallium(III) methylphosphonate, like the parent gallium(III) organophosphonates, are very likely layered, as indicated by the powder XRD patterns. In contrast, the corresponding phenanthroline adducts are non-layered, and both the bipyridyl and phenanthroline adducts of gallium(III) benzylphosphonate are amorphous solids. FTIR, powder XRD, TGA, XPS, solid state ³¹P/¹³C MAS-NMR and BET surface area data are presented and discussed.

Full text of DOI:10.1016/S0020-1693(01)00471-6

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Inorganica Chimica Acta 320 (2001) 67–74
Gallium(III) organophosphonate adducts with the bidentate
amines 2,2%-bipyridyl and 1,10-phenanthroline
Julia Morizzi, Malcolm Hobday *, Colin Rix
Department of Applied Chemistry, RMIT Uni6ersity, 124 La Trobe St., Melbourne, Victoria 3000, Australia
Received 27 December 2000; accepted 17 April 2001
Abstract
A number of gallium(III) organophosphonates form adducts with the bidentate amines 2,2%-bipyridyl and 1,10-phenanthroline.
These adducts contain 1:2:1 molar ratio of metal/phosphorus/amine and have the proposed formulations
a
Ga(O3PR)(O2P(OH)R)(C10H8N2)·H2O and Ga(O3PR)(O2P(OH)R)(C12H8N2)·H2O (where R=CH3, C6H5 and CH2C6H5;
C10H8N2 is 2,2%-bipyridyl and C12H8N2 is 1,10-phenanthroline). Unlike the parent gallium(III) organophosphonates, which
conform to the general formula Ga(OH)(O3PR)·xH2O (x=0 or 1), the amine adducts lack the hydroxo group, but contain the
organophosphonate ligand in the partially as well as fully deprotonated forms. All compounds were isolated from aqueous
solutions as monohydrates, with the exception of the bipyridyl adduct of gallium(III) phenylphosphonate, which is anhydrous.
TGA measurements suggest that for the hydrates, the water molecule is not coordinated to the metal. The bipyridyl adducts of
gallium(III) phenylphosphonate and gallium(III) methylphosphonate, like the parent gallium(III) organophosphonates, are very
likely layered, as indicated by the powder XRD patterns. In contrast, the corresponding phenanthroline adducts are non-layered,
and both the bipyridyl and phenanthroline adducts of gallium(III) benzylphosphonate are amorphous solids. FTIR, powder
XRD, TGA, XPS, solid state 31P/13C MAS-NMR and BET surface area data are presented and discussed. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Gallium complexes; Organophosphonate complexes; Layered complexes
intercalates reported for a number of other metal phos-
phonate systems [1,8–14,16–18]. Similar work has been
conducted with mono- and bidentate compounds [19–
26], for instance, 2,2%-bipyridyl and 1,10-phenanthroline
have been intercalated into layered titanium [24] and
zirconium [20,21,25,26] phosphate structures, resulting
in an increased interlayer spacing.
A series of lamellar gallium(III) organophosphonates
[27–29] have previously been prepared. In this study,
the potentially bidentate ligands 2,2%-bipyridyl and 1,10-
phenanthroline were combined with certain gallium(III)
organophosphonates to determine if the lamellar struc-
ture was retained on adduct formation, and if so, what
effect amine coordination would have on the interlayer
spacing. The corresponding organophosphonates of in-
dium(III) have also been investigated [29,30] and
analogous amine indium(III) organophosphonates pre-
pared [31].
1. Introduction
Lamellar metal organophosphonates are found to
have well-defined void spaces and coordination sites
which usually allow access of intercalating agents into
the internal surface of the layered structure [1]. Interca-
lation of alcohols [2–7] and amines [1,8–18] into metal
organophosphonates has received considerable atten-
tion. For example, vanadium(IV) organophosphonates
have been studied in terms of mono- and di-alcohol
intercalation, where the interlayer spacing is found to
increase according to the size of the alcohol chain [7].
Amine intercalation of vanadium(IV) organophospho-
nates has also been studied [15], with these types of
* Corresponding author. Tel.: +61-39-925-2117; fax: +61-39-639-
1321.
E-mail address: malcolm.hobday@rmit.edu.au (M. Hobday).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00471-6

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J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
2. Experimental
proposed
formulations
(C10H8N2=2,2%-bipyridyl,
C12H8N2=1,10-phenanthroline).
The gallium(III) compounds 1–6 were synthesised
from solutions of gallium(III) chloride, the organophos-
phonic acid and the amine ligand in a 1:2:2 or 1:3:2
molar ratio for the aromatic and alkylphosphonic
acids, respectively. The same products were obtained in
both water/ethanol (70% ethanol) and aqueous solvent
systems (water/ethanol was used initially for the reac-
tions of 2,2%-bipyridyl due to limited water solubility).
All chemicals were obtained from Aldrich Chemical
Co. or BDH Laboratory Supplies and were AR grade.
The metal ion solution was added with stirring to the
combined ligands in solution and the mixture sealed in
a Teflon-lined stainless-steel autoclave and heated at
160 °C for 2 days. A white solid was produced for the
methyl- and phenylphosphonate gallium(III) adducts
for both bipyridyl and phenanthroline. For the corre-
sponding benzylphosphonate compounds, the reaction
solutions were evaporated to half the volume before a
precipitate formed. The solids were washed with ultra-
pure water, then air-dried and stored over phosphorus
pentoxide prior to characterisation. (Note that the reac-
tion solutions were clear and colourless prior to auto-
clave treatment, but were transparent red and peach,
for the bipyridyl and phenanthroline derivatives, re-
spectively, following the autoclave treatment, pre-
sumably due to the presence of gallium bipyridyl and
phenanthroline complexes.) The resulting compounds
were characterised by elemental analysis, FTIR, TGA,
powder XRD, XPS, 31P/13C MAS-NMR and BET sur-
face area measurements. Analyses for Ga and P were
carried out at Perkin–Elmer Australia Pty. Ltd.; analy-
ses for C, H and N were carried out by HRL Technol-
ogy Pty. Ltd., Melbourne, Australia. Thermo-
gravimetric analyses (TGA) were performed under
flowing nitrogen gas in a Perkin–Elmer TGA 7/DX
thermogravimetric analyser. Infrared spectra were ob-
tained on a Perkin–Elmer 2000 Fourier transform in-
frared spectrometer using KBr discs. Powder XRD
patterns were acquired on a Philips automated diffrac-
tometer using monochromatised Cu Ka radiation. A
VG Scientific Scanning Auger Nanoprobe was used to
obtain X-ray photoelectron spectra using a non-
monochromatised magnesium filament (Mg Ka) as the
radiation source. Cross-polarisation solid state MAS-
NMR for 13C and 31P were acquired using a Varian 300
NMR spectrometer at 75.45 MHz for 13C and 121.46
MHz for 31P, with the 13C chemical shifts referenced to
TMS and the 31P chemical shifts referenced to potas-
sium dihydrogen orthophosphate. BET surface areas
were measured using a Micromeritics ASAP 2000 sur-
face area analyser with nitrogen as the absorbate gas.
The elemental analyses for Ga, P, C, H and N in the
bipyridyl and phenanthroline derivatives of gallium(III)
organophosphonates gave good agreement with the
Anal. Found: Ga, 13.3; P, 11.7; C, 48.9; H, 3.1; N,
5.0. Calc. for Ga(O3PC6H5)(O2P(OH)C6H5)(C10H8N2)
(1): Ga, 13.0; P, 11.5; C, 49.2; H, 3.2; N, 5.2% (%
yield=58).
Anal. Found: Ga, 12.3; P, 11.0; C, 50.1; H, 4.1; N,
5.0. Calc. for Ga(O3PCH2C6H5)(O2P(OH)CH2C6H5)-
(C10H8N2)·H2O (2): Ga, 12.3; P, 11.0; C, 51.0; H, 4.1;
N, 5.0% (% yield=71).
Anal. Found: Ga, 16.0; P, 14.4; C, 33.4; H, 3.5; N,
6.2. Calc. for Ga(O3PCH3)(O2P(OH)CH3)(C10H8N2)·
H2O (3): Ga, 16.2; P, 14.4; C, 33.4; H, 3.5; N, 6.5% (%
yield=33).
Anal. Found: Ga, 11.9; P, 10.6; C, 49.3; H, 3.7; N,
4.9. Calc. for Ga(O3PC6H5)(O2P(OH)C6H5)(C12H8N2)·
H2O (4): Ga, 12.0; P, 10.7; C, 49.6; H, 3.6; N, 4.8% (%
yield=54%).
Anal. Found: Ga, 11.5; P, 10.4; C, 50.1; H, 4.0; N,
4.9. Calc. for Ga(O3PCH2C6H5)(O2P(OH)CH2C6H5)-
(C12H8N2)·H2O (5): Ga, 11.7; P, 10.4; C, 50.4; H, 3.9%;
N, 4.7% (% yield=73%).
Anal. Found: Ga, 15.2; P, 13.5; C, 36.7; H, 3.8; N,
6.1. Calc. for Ga(O3PCH3)(O2P(OH)CH3)(C12H8N2)·
H2O (6): Ga, 15.3; P, 13.6; C, 36.8; H, 3.8; N, 6.1% (%
yield=32%).
3. Results and discussion
3.1. Elemental analysis
For the bipyridyl and phenanthroline adducts of
gallium(III) methyl- (3, 6), phenyl- (1, 4) and ben-
zylphosphonate (2, 5), the elemental analyses indicate a
1:2:1 molar ratio of Ga/P/amine, consistent with the
organophosphonate being present in both the fully and
partially deprotonated forms. Analogous organophos-
phonate compounds with mono- and di-anionic
organophosphonate groups have previously been ob-
tained for indium [29,30], as well as cerium [32], lan-
thanum [33], uranyl [34], manganese [35], iron [36] and
aluminium [37,38]. The bipyridyl and phenanthroline
amine adducts of indium(III) organophosphonates have
been shown to possess the same In/P/amine composi-
tion of 1:2:1 [31]. Compounds 2, 3, 4, 5, and 6 are
monohydrates, whereas 1 is anhydrous. These formula-
tions are consistent with the results from FTIR, TGA
and other characterisation techniques. It is interesting
to note that the parent gallium organophosphonates
have the general form Ga(OH)(O3PR)·xH2O (where R
is an organic group, x=0 or 1), whereas the bidentate
amine
adducts
are
generally
Ga(O3PR)(O2P-
(OH)R)(amine)·xH2O. The presence of the hydroxo
group in the parent gallium(III) organophosphonates

J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
69
was attributed [29] to the polarisation of coordinated
water by the metal, leading to hydroxo formation by
the loss of protons. Presumably for compounds 1–6,
where there are no hydroxo groups, the coordination of
the amine reduces the polarising ability of the metal
ion, preventing hydroxo group formation.
a similar spectrum to those of 1 and 2, with the phenyl
group absorptions absent and a slight shift in peak
frequencies. The only major difference is an absorption
due to the CH2 bending vibration around 1300 cm−1
arising from the methyl group. As observed for 1, both
the benzyl(2) and methylphosphonate (3) derivatives
contain a broad peak around 3400 cm−1 due to an OH
stretch associated with both water and the undissoci-
ated phosphonic acid group, but unlike 1 a weak
absorption is observed in 2 and 3 around 1630 cm−1
due to the OH bending vibration of water.
3.2. Fourier transform infrared spectroscopy (FTIR)
The FTIR spectra of 1–6 are typical of this class of
compounds, with peaks that are well resolved. For the
bipyridyl adducts, the spectrum of the gallium
phenylphosphonate derivative (1) is representative (see
Fig. 1) and is discussed here in detail. This spectrum
contains a broad band due to an OH stretch vibration
at 3434 cm−1 attributed to the undissociated phospho-
nic acid group. A relatively weak peak observed at 3056
cm−1 is due to the CH stretching mode for the phenyl
ring, with a very sharp and intense peak located at 1437
cm−1 also due to the aromatic CH. The vibrations
associated with the PO3 moiety are observed between
1000 and 1200 cm−1. The peaks characteristic of the
out-of-plane CH vibrations in C6H5 are located at 734,
718 and 697 cm−1. These peaks are characteristic of
phenylphosphonate systems and very similar absorp-
tions are found in the parent gallium(III) phenylphos-
phonate [29]. Other peaks observed in this region are
associated with the bipyridyl ligand, as are the peaks at
1601, 1578, 1475, and 1445 cm−1. Corresponding peaks
are observed at slightly lower frequencies in the uncom-
plexed 2,2%-bipyridyl [39] ligand. The increase in
bipyridyl absorption frequencies is consistent with the
coordination of the amine ligand to the metal, rather
than the amine non-covalently lodged between the lay-
ers of the lamellar parent gallium(III) phenylphospho-
nate. The FTIR spectrum of the benzylphosphonate (2)
differs from that of 1 only marginally, exhibiting a very
sharp peak around 1420 cm−1 due to the additional
CH2 group. The methylphosphonate (3) derivative has
The FTIR spectra for the phenanthroline analogues
are very similar to the corresponding bipyridyl deriva-
tives, for example the phenylphosphonate(4) derivative
exhibits a broad peak at 3424 cm−1 due to the OH
stretch, and a weak peak at 1627 cm−1 due to the OH
bending vibration of water. A relatively weak band due
to the CH stretching mode for the phenyl ring is
observed at 3047 cm−1, with a very sharp and intense
peak located at 1428 cm−1 also due to the aromatic
CH bend. The vibrations associated with the PO3 moi-
ety are observed between 1000 and 1200 cm−1. The
peaks characteristic of the out-of-plane CH vibrations
are located at 753, 717 and 698 cm−1. Other peaks
observed in this region, and those at 1587, 1520, and
1491 cm−1 are associated with the phenanthroline lig-
and and are consistent with coordination of the amine
to the metal [39]. The phenanthroline derivative of
gallium(III) benzylphosphonate (5) displays similar ab-
sorptions to (4), with the only major difference due to
the CH2 group absorbing at 1428 cm−1
methylphosphonate derivative (6) contains the methyl
CH band at 1314 cm−1
. The
.
3.3. Thermogra6imetric analyses (TGA)
The TGA of 1 shows two major thermal decomposi-
tions, the first mass loss occurring between 300 and
400 °C and the second between 540 and 670 °C. These
mass losses are attributable to the loss of the amine
ligand and the organic group of the organophospho-
nate, respectively (see Fig. 2). The TGA of the parent
gallium(III) phenylphosphonate showed a mass loss at
above 500 °C due to the phenyl group decomposition
[28]. This suggests that the second mass loss in 1 arises
from the loss of the organic phenyl group, and conse-
quently the first mass loss can be attributed to the
bipyridyl ligand (observed mass loss 29.2%, expected
28.9%). In metal organophosphonates, decomposition
of the organophosphonate group is usually incomplete
[40]. These TGA assignments are supported by the
observation that 2,2%-bipyridyl incorporated into a zir-
conium phosphate system decomposed between 330–
400 °C [21]. The TGA for the benzylphosphonate (2)
showed thermal decompositions due to loss of water
(30–100 °C), loss of bipyridyl (270–400 °C) and loss
Fig. 1. FTIR spectrum for Ga(O3PC6H5)(O2P(OH)C6H5)(C10H8N2)
(1).

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J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
played strong 001 diffractions, consistent with the pro-
posed lamellar structure. One reason for synthesising
the bidentate amine adducts 1–6 in this study, was to
investigate the influence of the coordinated ligands on
layering and interlayer spacing, relative to the parent
gallium(III) organophosphonates. The powder XRD
pattern of the bipyridyl derivative of gallium(III)
phenyphosphonate (1) contains a strong 001 diffrac-
tion, suggesting a lamellar structure with an interlayer
,
spacing of 14.08 A, which is slightly less than that
observed in the parent gallium(III) phenylphosphonate
,
(14.52 A) [29]. In contrast, the XRD pattern for the
corresponding phenanthroline derivative (4) does not
contain a strong 001 diffraction, suggesting a non-
lamellar structure (see Fig. 3).
Gallium(III) benzylphosphonate has a smaller inter-
,
layer spacing (13.04 A) than the corresponding galliu-
m(III) phenylphosphonate [29]. The reduced spacing
for the gallium(III) benzylphosphonate relative to the
phenyl analogue is indicative of the greater flexibility,
and hence reduced steric demands, of the benzyl group
containing the methylene (CH2) link. The addition of
the bipyridyl and phenanthroline ligands to form the
compounds 2 and 5, respectively, produces compounds
with amorphous solid state structures, as indicated by
powder XRD patterns. The compounds 2 and 5 did not
precipitate from the reaction mixture, as observed for
other compounds in the series, but were precipitated by
slow evaporation from a gel-like solution. These solu-
bility properties are consistent with a non-polymerised
solid state structure. Presumably, bidentate amine coor-
dination with the gallium(III) benzylphosphonate pro-
duces coordinately saturated gallium(III) without the
involvement of polymerisation. The bipyridyl (3)
derivative of gallium(III) methylphosphonate exhibited
an XRD pattern indicative of a lamellar system with a
Fig. 2. TGA for (a) Ga(O3PC6H5)(O2P(OH)C6H5)(C10H8N2) (1) and
(b) Ga(O3PC6H5)(O2P(OH)C6H5)(C12H8N2)·H2O (4).
of the benzyl group (510–600 °C). The methylphos-
phonate derivative (3) showed corresponding mass
losses between 33 and 130 °C due to loss of water, and
between 217–412 °C and 454–611 °C, for the amine
and organophosphonate, respectively.
The TGA results for the phenanthroline adducts are
similar to those of the bipyridyl analogues. Compounds
4, 5 and 6 exhibit three major mass losses consistent
with the loss of water, loss of amine ligand and decom-
position of the organophosphonate. The thermal de-
compositions for the phenylphosphonate (4) are
observed between 20–120 °C (water), 210–400 °C
(phenanthroline; observed 29.5%, expected 31.0%) and
420–610 °C (see Fig. 2). The thermal decompositions
in the benzylphosphonate (5) system are found over the
temperature ranges 20–100 °C (water), 200–380 °C
(phenanthroline; observed 30.0%, expected 29.6%) and
400–600 °C. Similarly, for the methylphosphonate (6),
the three mass losses occur at 66–222 °C, 225–343 °C
and 347–697 °C. In all cases, the thermal decomposi-
tion of the organic group of the organophosphonate is
incomplete [40]. The relatively low temperature range
corresponding to the loss of water for compounds 2–6
indicates that the water is not coordinated to the metal.
This is in contrast to coordinated or interlamellar water
loss in the gallium(III) benzylphosphonate, Ga(OH)-
(O3PCH2C6H5)·H2O, which occurred over the tempera-
ture range 100–150 °C [29].
,
d001 spacing of 8.98 A, a reduced interlayer spacing
compared with that in the parent gallium(III)
,
methylphosphonate (9.76 A) [29]. The XRD pattern for
the phenanthroline adduct (6) indicated a non-lamellar
structure.
3.5. Solid state MAS-NMR
The 31P MAS-NMR spectrum of 1, the bipyridyl
derivative of gallium(III) phenylphosphonate, con-
tained two phosphorus resonances (7 and −5 ppm),
consistent with the presence of di- and mono-anion
forms of the phosphonate ligand. The 13C MAS-NMR
for the original phenylphosphonate compound con-
tained one peak at 135 ppm due to the aromatic phenyl
carbons [29]. The 13C MAS-NMR spectrum for 1 con-
tained a broad peak centred at 134 ppm (phenyl group),
with two smaller peaks at 147 and 153 ppm attributable
to the aromatic carbons associated with the heterocyclic
groups in the bipyridyl ligand (see Fig. 4a). The 31P
3.4. Powder X-ray diffraction (XRD)
The powder XRD pattern for the previously reported
gallium(III) phenylphosphonate [29] compound dis-

J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
71
MAS-NMR spectrum of the corresponding phenan-
throline derivative (4) contained a broad 31P signal due
to two unresolved peaks centred at −1.4 ppm (shoul-
der at 4 ppm). The 13C MAS-NMR spectrum contained
one broad 13C peak at 126 ppm attributed to the
aromatic carbons in the phenyl and phenanthroline
groups, together with a smaller peak at 138 ppm,
attributed to the aromatic carbons in the heterocyclic
portions of the phenanthroline ligand (see Fig. 4b). In
the same way, 31P and 13C MAS-NMR spectra for 2, 3,
5 and 6 are consistent with at least two 31P sites, and
with the presence of the organic group and amine
ligand, respectively. The 31P MAS-NMR spectra for 2
and 5 contain a broad peak at about 10 ppm with a
shoulder at about 8 ppm. For 3 and 6, a very broad 31P
peak is observed (peak width at half height is 6 ppm),
indicative of at least two sites, as suggested by others
[23]. The 13C MAS-NMR spectra for2 and 5 display
signals due to the aromatic phenyl ring and amine
group centred at 134 ppm, with another peak at 153
ppm for 2, and two small shoulders at 144 and 154 ppm
for 5 due to the aromatic carbons in the bipyridyl and
phenanthroline groups, respectively. The 13C MAS-
NMR spectra for both 2 and 5 contain peaks at ap-
proximately 43 ppm due to the CH2 of the benzyl
group, whereas the 13C spectra of 3 and 6 contain peaks
at approximately 23 ppm due to the methyl group. The
13C MAS-NMR signal due to the aromatic carbons in
the amine ligands, the only aromatic group present in
the methylphosphonate systems 3 and 6, is present at
around 134 ppm, with a small shoulder at 154 ppm.
3.6. BET surface areas
The lamellar nature of metal organophosphonates
suggests that these compounds may have accessible
surface areas that are larger than corresponding non-
lamellar systems. Others [41] have found that for bis(-
methylphosphonato)zirconium(IV), surface area is
influenced by particle size, with surface areas increasing
as particle size is decreased. A direct correlation was
also found between molecular volume and interlayer
spacing for a series of isostructural lamellar metal(IV)
phosphates and phosphonates [42]. The BET surface
areas for compounds 1–6, the parent gallium(III)
organophosphonates and related indium(III) com-
pounds, are summarised in Table 1, where data is either
from this study, or from Morizzi et al. [29,31]. The
Fig. 3. Powder XRD patterns for (a) Ga(O3PC6H5)(O2P(OH)C6H5)(C10H8N2) (1) and (b) Ga(O3PC6H5)(O2P(OH)C6H5)(C12H8N2)·H2O (4).

72
J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
produces a relatively minor decrease (to 20 m2 g−1).
From these observations, however, there appears to be
no simple correlation between interlayer spacing and
BET surface area.
3.7. X-ray photoelectron spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) is a useful
tool for the analysis of surface composition, surface
atom oxidation states and the estimation of core-elec-
tron binding energies. XPS involves X-ray stimulation
of electron emission from the valence and inner shells
of the surface atoms [43]. In the present study, the area
of particular interest was the binding energies associ-
ated with the C- and N-bonds of the heterocyclic amine
ligands incorporated into the organophosphonate
systems.
As shown earlier, comparison of the FTIR spectra
for the free molecules, 2,2%-bipyridyl and 1,10-phenan-
throline, and the same molecules held in the metal(III)
organophosphonate systems, demonstrated slight in-
creases in peak frequencies associated with the amine
ligand in the metal complexes. The increase in these
absorption frequencies is consistent with coordination
of the amine ligand to the metal, rather than a simple
mixture, or the amine groups non-covalently lodged
between the layers of the lamellar parent metal(III)
organophosphonate. To verify these observations in the
FTIR spectra, XPS studies were conducted on the
bipyridyl(1) and phenanthroline(4) adducts of galliu-
m(III) phenylphosphonate. In addition to the samples
analysed by XPS, the free ligand 1,10-phenanthroline
was also analysed and used as a reference. It should be
Fig. 4. Solid state 13C MAS-NMR spectra for (a) Ga(O3PC6H5)-
(O2P(OH)C6H5)(C10H8N2)
(1)
and
(b)
Ga(O3PC6H5)(O2-
P(OH)C6H5)(C12H8N2)·H2O (4).
parent gallium(III) and indium(III) organophosphonate
compounds are found to have surface areas in the
ranges 17–52 m2 g−1 and 14–46 m2 g−1, respectively.
In all cases, adduct formation with bipyridyl or
phenanthroline produces a decrease in BET surface
area that is often substantial. The one exception occurs
for gallium(III) benzylphosphonate (surface area 25
m2 g−1) where conversion to the phenanthroline adduct
Table 1
BET surface areas and interlayer spacing for gallium(III) and indium(III) organophosphonates and their 2,2%-bipyridyl and 1,10-phenanthroline
adducts
Compound (bipy=2,2%-bipyridyl) (phen=1,10-phenanthroline) BET surface area (m2 g−1
)
Interlayer spacing (A)
,
Ga(OH)(O3PC6H5) (parent)
52
4
6
25
10
20
17
5
14.52
14.10
NL a
13.04
NL a
NL a
9.76
Ga(O3PC6H5)(O2P(OH)C6H5)bipy (1)
Ga(O3PC6H5)(O2P(OH)C6H5)phen·H2O (4)
Ga(OH)(O3PCH2C6H5)·H2O (parent)
Ga(O3PCH2C6H5)(O2P(OH)CH2C6H5)bipy·H2O (2)
Ga(O3PCH2C6H5)(O2P(OH)CH2C6H5)phen·H2O(5)
Ga(OH)(O3PCH3) (parent)
Ga(O3PCH3)(O2P(OH)CH3)bipy·H2O(3)
Ga(O3PCH3)(O2P(OH)CH3)phen·H2O(6)
In(O3PC6H5)(O2P(OH)C6H5)·H2O (parent)
In(O3PC6H5)(O2P(OH)C6H5)bipy·H2O
In(O3PC6H5)(O2P(OH)C6H5)phen·H2O
In(O3PCH2C6H5)(O2P(OH)CH2C6H5)·H2O (parent)
In(O3PCH2C6H5)(O2P(OH)CH2C6H5)bipy·H2O
In(O3PCH2C6H5)(O2P(OH)CH2C6H5)phen·H2O
In2(O3PCH3)3·2H2O (parent)
8.90
6
NL a
15.06
11.34
NL a
14.81
NL a
NL a
7.58
30
18
13
14
4
7
46
9
In(OH)(O3PCH3)bipy
In(OH)(O3PCH3)phen·2H2O
8.83
7
NL a
a NL=non-layered.

J. Morizzi et al. / Inorganica Chimica Acta 320 (2001) 67–74
73
noted that 2,2%-bipyridyl completely sublimed under the
sample analysis conditions, and hence could not be
analysed by XPS, however, similar results would be
anticipated for both compounds.
organophosphonates. Compounds 4 and 6 were found
to be non-lamellar in the solid state, whereas 2 and 5
were amorphous solids. There appears to be no correla-
tion between BET surface area and the layering of these
compounds in the solid state, however, BET surface
areas of the gallium(III) organophosphonates and their
indium analogues are substantially decreased by amine
coordination.
The binding energy data associated with carbon (1s)
in the phenanthroline ligand indicated only one type of
carbon with a peak maximum at 284.40 eV, whilst 1
and 4 were found to have two carbon sites, associated
with the presence of heterocyclic amine carbons of
phenanthroline or bipyridyl (ꢀ284 eV) and the aro-
matic carbons of the phenyl group (ꢀ286 eV). The
change in the binding energies of carbon (DC) associ-
ated with the phenanthroline group vary by 0.1–0.15
eV, from the free ligand to the metal complexes. The
binding energies of carbon associated with phenanthro-
line are not expected to change significantly from the
free ligand to the metal complexes because on complex-
ation of the heterocyclic amine to the organophospho-
nate system, the carbon atoms do not form any new
bonds. The small variations in the binding energy of the
free ligand and metal complexes are indicative of this.
The binding energies associated with nitrogen (1s) in
the free phenanthroline molecule indicated only one
type of nitrogen with a peak maximum of 398.39 eV,
and similarly, 1 and 4 were also found to have one
nitrogen site as expected, due to the presence of either
the phenanthroline or bipyridyl ligand. The change in
the binding energies of nitrogen (DN) from the free
ligand to the metal complex is in the range 0.98–1.15
eV. This increase in the binding energy associated with
nitrogen when the heterocyclic amine becomes incorpo-
rated into the organophosphonate system suggested
that the nitrogen atoms are indeed involved in different
types of bonds in comparison to the free ligand. For
example, the binding energies of BN and NH3 were
found to be 398.1 and 398.8 eV [44], respectively, which
illustrates that the binding energies of an element, such
as nitrogen, varies marginally when bonded to a differ-
ent species. The variation in binding energies of nitro-
gen from the free ligand to the metal complexes
strongly suggests that nitrogen binds to the metal on
addition to the organophosphonate system.
Acknowledgements
The authors thank the following people for their
assistance: Ian McPhail from RMIT for XRD measure-
ments; Matthew Glenn from RMIT for XPS measure-
ments; Tracy Lam and Dr Frances Separovic from
Melbourne University for assisting with MAS-NMR
spectra; and Vesna Dolic from Perkin–Elmer, Aus-
tralia, for assisting in ICP analyses. The authors thank
Bayswater Dental Pty.Ltd. for a donation of gallium
metal. Julia Morizzi gratefully acknowledges an APA
Scholarship.
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