Preparation and Probable Structure of Layered Complexes of Vanadyl Phosphate with 1-Alkanols and 1,ω-Alkanediols

Article abstract of DOI:10.1021/ic970073s

The direct reaction of liquid (or melted solid) 1-alkanols or 1,ω-alkanediols with solid finely ground VOPO₄· 2H₂O in a microwave field leads to layered complexes of the composition VOPO₄·2C_nH_2n+₁OH (n = 1 - 18) or VOPO₄·C_nH_2n(OH)₂ (n = 2-10), respectively. The results of X-ray diffraction analysis show that the structures of all of these polycrystalline complexes (intercalates) retain the original layers of (VOPO₄)∞, The molecules of alcohols are placed between the host layers in a bimolecular way, being anchored to them by donor-acceptor bonds between the oxygen atom of an OH group and a vanadium atom as well as by hydrogen bonds. The molecules of diols, on the other hand, using similar bonds, form, in monomolecular arrangement, bridges linking the adjacent layers of the host. The aliphatic chains of both intercalated alcohol and diol molecules possess all-trans configurations, and their axes are perpendicular to the host layers.

Full text of DOI:10.1021/ic970073s

2850
Inorg. Chem. 1997, 36, 2850-2854
Preparation and Probable Structure of Layered Complexes of Vanadyl Phosphate with
1-Alkanols and 1,ω-Alkanediols
Ludv´ık Benesˇ,* Kla´ra Mela´nova´, and V´ıteˇzslav Zima
Joint Laboratory of Solid State Chemistry of Academy of Sciences of Czech Republic and
University Pardubice, Studentska´ 84, 53009 Pardubice, Czech Republic
Jaroslava Kalousova´ and Jirˇ´ı Votinsky´
Department of General and Inorganic Chemistry, University Pardubice, Na´m. Legi´ı 565,
53210 Pardubice, Czech Republic
ReceiVed January 22, 1997X
The direct reaction of liquid (or melted solid) 1-alkanols or 1,ω-alkanediols with solid finely ground VOPO4‚
2H2O in a microwave field leads to layered complexes of the composition VOPO4‚2CnH2n+1OH (n ) 1-18) or
VOPO4‚CnH2n(OH)2 (n ) 2-10), respectively. The results of X-ray diffraction analysis show that the structures
of all of these polycrystalline complexes (intercalates) retain the original layers of (VOPO4)∞. The molecules of
alcohols are placed between the host layers in a bimolecular way, being anchored to them by donor-acceptor
bonds between the oxygen atom of an OH group and a vanadium atom as well as by hydrogen bonds. The
molecules of diols, on the other hand, using similar bonds, form, in monomolecular arrangement, bridges linking
the adjacent layers of the host. The aliphatic chains of both intercalated alcohol and diol molecules possess
all-trans configurations, and their axes are perpendicular to the host layers.
Introduction
temperature and with sufficient amounts of the host molecules,
the guest chains in the complex possess the all-trans configu-
ration1 and their axes form with the host layers either an acute
angle (usually 55-60°)11,13 or a right angle,1,8,13 the guest layers
being most often bimolecular8,9,10,13 but also sometimes mono-
molecular.8,12
So far it has not been possible to apply direct X-ray diffraction
analysis to structure determination of the complexes mentioned
because these substances show no tendency to form crystals of
sufficient magnitude and suitable mechanical properties (they
have a gelatinous consistency) and all of them are readily
hydrolyzed in air.
Using a new preparation method, we have now succeeded in
obtaining the VOPO4 complexes with an extensive homologous
series of 1-alkanols up to 1-octadecanol, i.e., also those that
are solids at room temperature. Similarly we have prepared the
VOPO4 complexes with 1,ω-alkanediols up to 1,10-decanediol.
Having determined the lattice parameters of all of these
complexes, we suggest the most probable arrangement of the
alcohol and diol molecules between the host layers.
A number of recently published papers have reported attempts
to find the structural principles governing the intercalation of
aliphatic molecules (with terminal functional groups) between
the layers of hosts. With this aim have been investigated the
intercalations of, e.g., aliphatic alcohols, diols, amines with
unbranched carbon chains into some natural silicates,1-4 vanadyl
or niobyl sulfates and phosphates,5-7 vanadyl alkylphospho-
nates,8 and other similar hosts.
Recently we determined the composition and lattice param-
eters of layered complexes formed by intercalation of aliphatic
alcohols (C1-C8),9,10 amines (C2-C10),11 and carboxylic acids
(C1-C4)12 into three isostructural layered hosts: vanadyl
phosphate (VVOPO4), vanadyl arsenate (VVOAsO4), and vanadyl
sulfate (VIVOSO4).
From the experiments carried out so far it follows that the
intercalated molecules of the given kind are always anchored
to the host layers by their functional groups.13,14 At room
X Abstract published in AdVance ACS Abstracts, June 1, 1997.
(1) Lagaly, G.; Fritz S.; Weiss, A. Clays Clay Miner. 1975, 23, 45.
(2) Lagaly, G. Angew. Chem. 1976, 88, 628.
(3) Behrend, D.; Beneke, K.; Lagaly, G. Angew. Chem. 1976, 88, 608.
(4) Lagaly, G. Clay Miner. 1981, 16, 1.
Experimental Section
Preparation. Vanadyl phosphate dihydrate VOPO4‚2H2O (for
structure see refs 15 and 16 ) was obtained by long-term boiling of a
V2O5 suspension in aqueous phosphoric acid.17
The layered complexes with alcohols and diols were prepared by
suspending microcrystalline VOPO4‚2H2O (ca. 1 g; grain size 0.01-
0.08 mm) in dry liquid alcohol (ca. 7-10 g) or mixing with solid
alcohol, and subsequent short exposure (0.5-5 min) to a microwave
field; the reaction mixture was placed in a 15 cm3 glass flask equipped
(5) Ladwig, G. Z. Chem. 1980, 20 (2), 70.
(6) Beneke, K.; Lagaly, G. Inorg. Chem. 1983, 22, 1503.
(7) Garcia-Ponce, A. L.; Moreno-Real, L.; Jimenez-Lopez, A. J. Solid
State Chem. 1990, 87, 20.
(8) Johnson, J. W.; Jacobson, A. J.; Butler, W. M.; Rosenthal, S. H.; Brody,
J. F.; Lewandowski, J. T. J. Am. Chem. Soc. 1989, 111, 381.
(9) Benesˇ, L.; Votinsky´, J.; Kalousova´, J.; Klikorka, J. Inorg. Chim. Acta
1986, 114, 47.
(10) Votinsky´, J.; Benesˇ, L.; Kalousova´, J.; Klikorka, J. Inorg. Chim. Acta
1987, 126, 19.
(11) Benesˇ, L.; Hyklova´, R.; Kalousova´, J.; Votinsky´, J. Inorg. Chim. Acta
1990, 177, 71.
(12) Benesˇ, L.; Votinsky´, J.; Kalousova´, J.; Handl´ırˇ, K. Inorg. Chim. Acta
1990, 176, 255.
(14) Whittingham, M. S., Jacobson, A. J., Eds. Intercalation Chemistry;
Academic Press: New York, 1982.
(15) Jordan, B.; Calvo, C. Can. J. Chem. 1973, 51, 2621.
(16) Jordan, B.; Calvo, C. Acta Crystallogr., Sect. B 1976, 32, 2899.
(17) Ladwig, G. Z. Anorg. Allg. Chem. 1965, 338, 266.
(13) Lagaly, G.; Beneke, K. Colloid Polym. Sci. 1991, 269, 1198.
S0020-1669(97)00073-6 CCC: $14.00 © 1997 American Chemical Society

Complexes of Vanadyl Phosphate with Alcohols
Inorganic Chemistry, Vol. 36, No. 13, 1997 2851
with a reflux condenser and put into the waveguide of microwave
generator with stirring and heating. After cooling, the solid product
formed was filtered off. When the starting material was a solid alcohol,
the suspension was separated from the melt by hot filtration. The
samples for X-ray diffraction analyses were left wetted with a small
residue of the respective alcohol, and also in the preparations starting
from melted alcohols the residues of solid alcohols were not removed.
On the other hand, the samples for thermogravimetric and differential
thermal analyses and for IR spectral measurements were washed with
pentane (intercalates with liquid alcohols) or toluene followed by
pentane (intercalates with solid alcohols).
The microwave apparatus used for preparing the complexes was
specially constructed by Radan Ltd., Pardubice, the Czech Republic.
It operates at a frequency of 2450 ( 30 MHz with a total generator
output of 800 W, out of which 30-50 W is absorbed by the reaction
mixture. The metal waveguide with a square cavity (5.2 × 5.2 cm) is
equipped with an opening of 2 cm diameter, which serves for locating
the reaction vessel into the waveguide axis.
Analyses. The TGAs of the intercalates were performed with a
Derivatograph MOM (Hungary), the measurements being carried out
in the temperature interval of 30-700 °C in an N2 atmosphere at heating
rates of 5 °C min-1. The weight of the samples was 100 mg.
In some cases, particularly with complexes of solid alcohols, the
composition was determined by elemental analysis (C, H).
Diffraction Measurements. The powder data of the intercalates
with a minor surplus of the guest alcohol were obtained with an X-ray
diffractometer (HZG-4, Germany) using CuKR1 radiation (λ ) 1.5405
Å) with discrimination of the Cu Kâ by an Ni filter. The CuKR2
intensities were removed from the original data. Silicium (a ) 5.430 55
Å) was used as internal standard. Diffraction angles were measured
from 1.5° to 50° (2Θ). The obtained data were refined by a least-
squares program minimizing (2Θexp - 2Θcalc)2.
Figure 1. Representation of simplified shape and dimensions of
molecules of 1-alkanols (a) and 1,ω-diols (b). All of the aliphatic chains
assume all-trans configurations.
IR Spectral Measurements. The absorption IR spectra of all of
the complexes in Nujol suspension were recorded in the region 4000-
400 cm-1 on a Perkin-Elmer 684 spectrometer.
Calculation of Steric Demands of 1-Alkanol and 1,ω-Alkanediol
Molecules. Introduction of foreign molecules between host layers such
as layers of vanadyl phosphate is usually accompanied by a distinct
increase in the basal spacing c of the solid. The magnitude of this
change is governed by the van der Waals dimensions of the entering
molecules, their numbers, their way of location in the interlayer space,
and also the lengths of the bonds anchoring these molecules to the
host layers.
The 1-alkanol and 1,ω-alkanediol molecules, provided that their
chains are present in the all-trans configuration, can roughly be viewed
as rotational cylinders with the van der Waals diameters of about 5.20
Å. If the bases of the cylinders are located (see Figure 1) in such a
way that one of them crosses the oxygen atom of the OH group and
the other the carbon atom of the CH3 group (in 1-alkanols) or both
cross the oxygen atoms of terminal OH groups (in 1,ω-alkanediols),
then the heights of these cylinders are expressed by the following
equations:
Figure 2. The basic idea about steric demands of 1-alkanol (a) and
1,ω-diol (b) molecules for necessary gapping of rigid layers of host.
is, of course, affected by the angle (R) formed by the axis of its chain
and the host layer.
Similarly, the steric demands of 1,ω-alkanediol molecules (Figure
2b) are given by the perpendicular distances oxygen-layer (b, b′) which
need not be the same, by the length of the molecule (hdiol), and by the
inclination of its axis (R).
halc ) (n - 1)lCC sin â + lOC sin γ
hdiol ) (n - 1)lCC sin â + 2lOC sin γ
(1)
(2)
The transition from considering the steric demands of a single
molecule to considering those of whole layers of such molecules can
bring certain complications. For instance, the guest particles can form
not only a monomolecular layer as that expected with diols (Figure
3a) but also a bimolecular layer (Figure 3b), which is more likely in
the case of monobasic alcohols. In the latter case the terminal methyl
groups must slightly “overlap”, and the demand of the bimolecular layer
for gapping of the host structure must thereby be decreased (-k). In
the case of diols it cannot be excluded that their molecules could be
anchored by both OH groups to the same host layer, which would result
in the basal spacing of such complexes not increasing with increasing
length of the aliphatic chain.
where n represents the number of carbon atoms in the unbranched
aliphatic chain of the molecule, l designates bond length (lCC ) 1.537
Å, lOC ) 1.40 Å),18 and â and γ are the angles characterizing the spatial
arrangement of the aliphatic chain (1/2 CCC ) â ) 56.3°, OCC
- â ) γ ) 53.2°).19
The demands of the guest 1-alkanol molecule for the gapping of
host layers are obviously given (see Figure 2a) by the sum of the
perpendicular distance (b) of the oxygen atom of the OH group from
the host layer, the chain length (halc), and the van der Waals radius of
the methyl group (rCH3). The contribution of the length of the molecule
In spite of these and other possible complications, it is obvious that
there is a simple way of deriving the probable geometry of incorporation
of the chains from the experimentally determined dependence of basal
spacing (c) of the complexes prepared on the number of carbon atoms
(18) Rodd, E. H. Chemistry of Carbon Compounds; Elsevier: Amsterdam,
1964.
(19) Chapman, N. B., Ed. Aliphatic Compounds; Butterworths: London,
1973.

2852 Inorganic Chemistry, Vol. 36, No. 13, 1997
Benesˇ et al.
Figure 3. Steric demand of monomolecular (a) and bimolecular (b) layers of 1-alkanol in interlayer space of host.
Table 1. Lattice Parameters a, Number of (00l) Lines, and
Measured and Calculated Basal Spacings of the Intercalates of
Vanadyl Phosphate with 1-Alkanols and 1,ω-Alkanediols
(n) in the chain of intercalated molecules. In most cases the basal
spacing c will change with n according to the relation
∆c/∆n ) m(∆h/∆n) sin R
(3)
basal spacing (Å)
no. of
composition
a (Å) lines (00l)
measd
calcd
where m is the number of layers of guest molecules in one interlayer
space of the host, R is the inclination of the axis of the carbon chain
of the individual molecule, and the ratio ∆h/∆n (calculated by
differentiating eq 1 or 2) has the value of 1.279 for both 1-alkanols
and 1,ω-alkanediols.
VOPO4‚2CH3CH2OH
6.22
6.19
6.21
6.21
6.22
6.22
6.21
6.19
6.19
5
4
3
4
5
6
5
7
9
4
8
4
7
6
5
5
5
13.17
14.36
17.90
19.71
22.73
25.09
28.44
30.62
33.50
35.68
38.24
41.07
43.40
46.21
48.36
50.92
54.01
12.26
15.04
17.42
20.12
22.58
25.26
27.76
30.40
32.92
35.54
38.08
40.70
43.24
45.86
48.40
51.02
53.58
VOPO4‚2CH3(CH2)2OH
VOPO4‚2CH3(CH2)3OH
VOPO4‚2CH3(CH2)4OH
VOPO4‚2CH3(CH2)5OH
VOPO4‚2CH3(CH2)6OH
VOPO4‚2CH3(CH2)7OH
VOPO4‚2CH3(CH2)8OH
VOPO4‚2CH3(CH2)9OH
Results and Discussion
Preparation and Composition of Complexes. The applica-
tion of microwave radiation to the suspension of hydrated host
(VOPO4‚2H2O) in an excess of liquid guest has been described
recently.20 It turned out to be a highly efficient method of
preparation of the respective intercalates in the case of applica-
tion of liquid or melted 1-alkanols or 1,ω-alkanediols. The
absorption of microwaves by the water molecules present in
the structure of the hydrate results in rapid removal of these
molecules from the space between the (VOPO4)∞ to the
surrounding dry alcohol and in exfoliation of host.
During exposure to a microwave field, the reaction mixture
with volatile alcohol was heated to its boiling point. If the
alcohol intercalated had a longer chain, then the temperature
of the reaction mixture reached ca. 150 °C. The alcohols of
higher molecular weight required a longer exposure and, hence,
also a higher temperature. After finishing the exposure and
partially cooling the reaction mixture the (VOPO4)∞ are re-
associated taking the molecules of new guest between them a
microcrystalline intercalate without water is formed. In this
way the following exchange takes place:
VOPO4‚2CH3(CH2)10OH 6.20
VOPO4‚2CH3(CH2)11OH 6.20
VOPO4‚2CH3(CH2)12OH 6.21
VOPO4‚2CH3(CH2)13OH 6.21
VOPO4‚2CH3(CH2)14OH 6.21
VOPO4‚2CH3(CH2)15OH 6.19
VOPO4‚2CH3(CH2)16OH 6.21
VOPO4‚2CH3(CH2)17OH 6.21
VOPO4‚HO(CH2)2OH
VOPO4‚HO(CH2)3OH
2
1
3
3
4
4
4
5
3
8.56
10.05
11.54
12.40
14.04
15.13
16.68
17.92
18.95
8.82
10.01
11.36
12.59
13.92
15.17
16.50
17.76
19.07
VOPO4‚HO(CH2)4OH
VOPO4‚HO(CH2)5OH
VOPO4‚HO(CH2)6OH
VOPO4‚HO(CH2)7OH
VOPO4‚HO(CH2)8OH
VOPO4‚HO(CH2)9OH
VOPO4‚HO(CH2)10OH
6.19
6.22
6.20
6.20
6.21
6.20
6.20
orientation. The (hk0) and (hkl) lines were not found in most
intercalates. The values found for the lattice parameters a and
c are presented in Table 1 for all the intercalates prepared.
The results of thermogravimetry of all the complexes together
with several checking analyses of carbon and hydrogen content
showed that the intercalates of 1-alkanols (except for methanol)
have the stoichiometric quotient x ) 1.92 ( 0.07, hence their
composition most probably corresponds to the formula
VOPO4‚2CnH2n+1OH. In contrast, 1,ω-alkanediols form com-
plexes with x ) 0.95 ( 0.08 corresponding to the formula
VOPO4‚CnH2n(OH)2.
VOPO4‚2H2O(s) + xG(l) f VOPO4‚xG(s) + 2H2O(l,g)
The samples of intercalates prepared in the given way were
crystalline, and their diffractograms showed a series of relatively
sharp (00l) reflections (see Table 1). The a parameter of the
tetragonal lattice of the intercalates was determined from the
position of diffraction line (200), which had a relatively low
intensity in all of the samples due to formation of the preferred
According to our preliminary results, vanadyl phosphate
dihydrate reacts similarly also with alkylamines, alkanoic acids,
amino acids, and some other substances. It is worth mentioning
that no reaction in the microwave field takes place if anhydrous
(20) Chatakondu, L.; Green, M. L. H.; Mingos, D. M. P.; Reynolds, S. M.
J. Chem. Soc., Chem. Commun. 1989, 1515.

Complexes of Vanadyl Phosphate with Alcohols
Inorganic Chemistry, Vol. 36, No. 13, 1997 2853
Figure 4. The dependence of basal spacing of all prepared complexes
on the number of carbon atoms in the aliphatic chain of intercalated
alcohols and diols.
VOPO4 instead of the dihydrate is suspended in any of the
above-mentioned liquid guests.
Orientation of Chains with Respect to Host Layers. Figure
4 presents graphically the dependence of basal spacing c on
the number of chain carbon atoms in the intercalated molecules.
Figure 5. The principles of location of 1-alkanol molecules in the
interlayer space of the VOPO4 host. The donor-acceptor bond length
For the intercalates of 1-alkanols the set of experimental
points fits the straight line c ) (2.58 ( 0.02)n + (7.33 ( 0.2)
with the correlation coefficient r ) 0.9996. The slope found
for this straight line corresponds very well (see eq 3) to the
situation of bimolecular arrangement of the guest 1-alkanol in
the interlayer space (m∆halc/∆n ) 2.56, m ) 2) and perpen-
dicular orientation of the chain axes with respect to the host
layers (R ) 90°).
O
alcfV is denoted as b. The hydrogen bond length Oalc-H‚‚‚OVdO is
denoted as b′. The axial heights of the cylinders representing the
aliphatic chains are slightly shortened.
The layered complexes of 1,ω-alkanediols again show a linear
dependence of their c parameters on the number of carbon
atoms. The fitting straight line has the equation c ) (1.30 (
0.02)n + (6.10 ( 0.12) (r ) 0.9990). Its slope is half of that
in the previous case and indicates a monomolecular arrangement
of diol molecules (m∆hdiol/∆n ) 1.30, m ) 1), but again with
the chains perpendicular to host layers (R ) 90°).
This conclusion perfectly agrees with the difference found
between the stoichiometries of the intercalates: it is 1:2 for
1-alkanols and 1:1 for 1,ω-alkanediols.
IR Spectral Analysis. The above idea about the structure
of the intercalates is supported by analysis of their IR spectra.
The valence vibration band of the vanadyl group ν(VdO) in
vanadyl salts was usually found within the frequency region
1050-980 cm-1 (see ref 21 ), and it is sensitive to the donor
ability of the ligand which coordinates the vanadium atom at
the position opposite to the oxygen atom.22 In anhydrous
vanadyl phosphate ν(VdO) is found at 1027 cm-1. In this
compound the above-mentioned position is occupied by an
oxygen atom from the neighboring layer, but with respect to
the large bonding distance between both of these atoms (2.50
Å),15 it can rather be considered unoccupied. In the hydrate
VOPO4‚2H2O, where water molecules are bound to vanadium
Figure 6. The principles of location of 1,ω-alkanediol molecules in
the interlayer space of the VOPO4 host. The diol molecules are anchored
to the layers by the same bonds as in the case of 1-alkanols.
analogous to the bond of water molecules to the (VOPO4)∞ layer
in the structure VOPO4‚2H2O.25
Weak and medium intense bands were found in the regions
3560-3530 cm-1 and 3400-3300 cm-1. The first of these
regions can be assigned to the mutual interaction of these
alcohols,24 and the second could possibly correspond to the
valence vibration of an OH group affected by the interaction
between the alcohol molecule and the host. Broad intense bands
in the region 3180-3165 cm-1 belong most probably to the
interaction of the alcohol with the host lattice resulting in the
hydrogen bonding between oxygen atoms of the host lattice and
the OH group of the alcohol molecules.
Probable Structure of Intercalates. If we take into account
both the stoichiometry of the complexes prepared and the fact
that the aliphatic chains of the guest molecules have their axes
perpendicular to the host layers, and finally also the fact that
probably half of the OH groups of the intercalated molecules
are bound by a donor-acceptor bond to vanadium atoms while
atoms,23 the wavenumber of the band mentioned is 1015 cm-1
The IR spectra of all of the intercalates of alcohols and diols
contain the ν(VdO) band in the region 1010-1020 cm-1
.
,
overlapping the intense bands of the PO4 tetrahedron. This
indicates the presence of a donor-acceptor bond between an
oxygen atom of the alcohol or diol and the vanadium atom
(21) Nakamoto, K. Infrared Spectra of Inorganic and Coordination
Compounds; Wiley: New York, 1964.
(22) Johnson, J. W.; Jacobson, A. J.; Brody, J. F.; Rich, S. M. Inorg. Chem.
1982, 21, 3820.
(23) Tachez, M.; Theobald, F.; Bernard, J.; Hewat, A. W. ReV. Chim. Miner.
1982, 19, 29.
(25) Cˇ apkova´, P.; Va´cha, J.; Votinsky´, J. J. Phys. Chem. Solids 1992, 53,
(24) Gamo, I. Bull. Chem. Soc. Jpn. 1962, 35, 1058.
215.

2854 Inorganic Chemistry, Vol. 36, No. 13, 1997
Benesˇ et al.
the other half are anchored to oxygen atoms of vanadyl groups
through a hydrogen bridge, we can suggest a possible structure
of these compounds: it is schematically represented in Figures
5 and 6.
If all of the experimentally found values of basal spacing of
complexes with diols are treated in such a way that the
calculated chain lengths (hdiol) as well as the coordinates of V
and O atoms in the (VOPO4)∞ layer are subtracted from them,
we get a remarkably constant and well-acceptable value of (b
+ b′) ) 3.86 ( 0.15 Å in all of the complexes (b is the bond
length between the diol oxygen atom and vanadium, and b′ is
the bond length in the hydrogen bridge of Odiol-H‚‚‚OVdO).
Reintroducing this mean value of distance (b + b′), we obtain
the c parameter for all of the complexes with diols (see the ccalc
values given in Table 1).
Figure 7. Covering of a host layer by perpendicularly oriented aliphatic
chains of the intercalated molecules. The van der Waals diameter of
chains is represented by an ellipse of 5.2 × 4.2 Å dimensions.
If the bond lengths b and b′ are retained also in the complexes
with 1-alkanols (which is highly probable), a simple calculation
will show that the “overlap” of methyl groups (-k) in the
respective bimolecular layers must amount to about -2.60 (
0.15 Å. The results of back-calculated ccalc values of the
complexes with 1-alkanols are given in Table 1.
In spite of the highly satisfactory agreement between the
results of the calculations carried out, our balance approach must
only be considered a mere attempt at speculative finding of the
structural principles governing the location of alcohol and diol
molecules between the layers of one of the hosts.
It is useful to evaluate the steric demands of a set of aliphatic
chains covering a certain plane and oriented perpendicularly to
it. The projection of a chain in its all-trans conformation on
the plane perpendicular to its axis represents an ellipse of 5.2
× 4.2 Å dimensions. Figure 7 gives an example of a possible
way of covering a (VOPO4)∞ layer with the alcohol molecules.
Acknowledgment. This study was supported by the Grant
Agency of the Czech Republic (Grant No. 203/95/1321) and
by the Academy of Sciences of the Czech Republic, Key Project
No. 12.
IC970073S