Hydrogen-bonded network in biphenyl-4,4′-diphospho-nic acid

Article abstract of DOI:10.1107/S0108270107025152

The crystal structure of the title compound, C12H12O6P2, displays two different regions alternating along the a axis: a hydrogen-bonded region encompassing the end-positioned phospho-nic acid groups and a hydro-phobic region formed by the aromatic spacers. The asymmetric unit contains only half of the biphenyl-4,4′-diphospho-nic acid (4,4′-bpdp) mol-ecule, which is symmetric with an inversion centre imposed at the mid-point between the two aromatic rings. The periodic organization of the mol-ecules is controlled by two strong O - H...O inter-actions between the phospho-nic acid sites. Weak C - H...π inter-actions are established in the aromatic regions. International Union of Crystallography 2007.

Full text of DOI:10.1107/S0108270107025152

organic compounds
phosphonate groups in biphenyl-4,40-diphosphonic acid, (I),
allows for porosity of organic±inorganic hybrid networks
(Zhang et al., 1998; Poojary et al., 1996). Despite the usefulness
of arenediphosphonate molecules as ligands, the crystal
structures of the corresponding acids are not known. We
present here the crystal organization and the supramolecular
network of (I).
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Hydrogen-bonded network in
biphenyl-4,40-diphosphonic acid
a
a
b
b
Â
Â
G. Prochniak, J. Zon, M. Daszkiewicz, A. Pietraszko
a
Â
and V. Videnova-Adrabinska *
The acid molecule is symmetric with an inversion centre
imposed at the mid-point between the two benzene rings
(Fig. 1) and, thus, the asymmetric unit of the crystal comprises
only one-half of the molecule. The two benzene rings are
coplanar and slightly deformed. The PÐO bonds of the
phosphonic acid group are bisectional and the P O bond is
axial with respect to the mean molecular plane. Therefore, the
spatial orientations of the hydrogen-bond donor and acceptor
sites in (I) are not appropriate for the formation of the R22(8)
motifs (Bernstein et al., 1995) observed in the ribbon exten-
sions of dicarboxylic acids, and the studied compound displays
a three-dimensional supramolecular network.
.
aDepartment of Chemistry, Wrocøaw University of Technology, 27 Wybrzeze
Wyspianskiego Street, 50-370 Wrocøaw, Poland, and bInstitute of Low Temperature
Â
Â
and Structural Research, Polish Academy of Sciences, 1 Okolna Street, 50-422
Wrocøaw, Poland
Correspondence e-mail: veneta.videnova-adrabinska@pwr.wroc.pl
Received 2 April 2007
Accepted 23 May 2007
Online 23 June 2007
The crystal structure of the title compound, C12H12O6P2,
displays two different regions alternating along the a axis: a
hydrogen-bonded region encompassing the end-positioned
phosphonic acid groups and a hydrophobic region formed by
the aromatic spacers. The asymmetric unit contains only half
of the biphenyl-4,40-diphosphonic acid (4,40-bpdp) molecule,
which is symmetric with an inversion centre imposed at the
mid-point between the two aromatic rings. The periodic
organization of the molecules is controlled by two strong OÐ
HÁ Á ÁO interactions between the phosphonic acid sites. Weak
CÐHÁ Á Áꢀ interactions are established in the aromatic regions.
A search of the Cambridge Structural Database (CSD,
Version 5.27; Allen, 2002) revealed only a single diphosphonic
acid structure, the triclinic polymorph of butane-1,4-
diphosphonic acid, which forms ribbons via R22(8)
(Mahmoudkhani & Langer, 2002). Two different hydrogen-
bond interactions control the organization of the molecules in
the crystal structure. One of them, assigned as O1ÐHO1Á Á ÁO2
Ê
[2.546 (2) A], is used to connect the re¯ection-related mol-
ecules in order to form thick molecular monolayers (bc). The
Ê
second hydrogen bond, O3ÐHO3Á Á ÁO2 [2.568 (2) A], is
Comment
established between rotation-related molecules belonging to
neighbouring layers and, therefore, joins the monolayers. The
overall crystal structure displays two different regions alter-
nating along the a axis: the hydrophilic regions where the
phosphonic acid groups are arranged and the hydrogen-bond
interactions take place, and the hydrophobic regions, where
the aromatic spacers reside. The biphenyl rings in the latter
Studies aimed at building predictable structures span from
hydrogen-bonded supramolecular networks to hybrid metal±
organic frameworks (MOF). The establishment of porosity in
coordination polymer structures has been a challenging but
central goal in solid-state chemistry, since by analogy with
zeolites, it opens up possibilities for chemical separation, gas
sorption, ion exchange, sensing and catalysis. The most
important factors determining MOFs are the chemical and
geometrical preferences of the metal ion and the speci®city of
the bridging polydentate ligand. Therefore, variable metal±
organic phosphonates have been studied with respect to their
potential applications in many of the above areas (Kong et al.,
2006; Sharma et al., 2000; Cabeza et al., 2002). Bisphos-
phonates can bind with different coordination modes (from
ꢁ1ꢂ1 up to ꢁ6ꢂ6) depending upon the level of deprotonation
and the stereo-accessibility of the donating lone pairs from
one side, and the geometry of the metal ion `vacant' sites from
the other side. This allows for the formation of variable
Â
coordination arrays (Matczak-Jon & Videnova-Adrabinska,
2005). The use of a rigid spacer between the end-functional
sites in diphosphonates reduces the orientational freedom of
the ligand and makes the frameworks more predictable (Cao
Figure 1
The molecular structure of (I), showing the atom-labelling scheme.
Displacement ellipsoids are drawn at the 50% probability level.
[Symmetry code: (i) x, 1 y, 1 z.]
Ê
et al., 2004). A distance of 10.665 A between the two
o434 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107025152
Acta Cryst. (2007). C63, o434±o436

organic compounds
region are arranged with a c-translation distance in order to
form two differently oriented stacks alternating along the b
axis. CÐHÁ Á Áꢀ interactions are established between adjacent
(re¯ection-related) stacks in the monolayer (Fig. 2). However,
with regard to the basic forces responsible for the solid-state
organization of the compound and the observed supra-
molecular network, it is reasonable to describe the structure in
terms of pillared hydrogen-bonded monolayers. Thus, each
phosphonic acid group serves to bridge four neighbouring
phosphonic acid groups in order to form a two-dimensional
hydrogen-bonded network parallel to the bc crystallographic
plane (Fig. 3). The (P1Ð)O3ÐHO3Á Á ÁO2( P1) bond
extends the screw-related sites into formal chains along the b
axis and (P1Ð)O1ÐHO1Á Á ÁO2( P1) links the chains into a
puckered two-dimensional network. Two centrosymmetric
motifs R24(12) and R44(16) are generated between the c-glide
chains and propagate along the b axis. The biphenyl rings,
aligned from both sides of the monolayers, act as linkers
(pillars) between them and follow the symmetry demands of
the hydrogen-bond network.
Only four structures of unsubstituted diphosphonic acids
with functional sites not located on the same C atom were
found in the CSD and they all belong to the ꢃ,! aliphatic
family with between 2 and 4 C atoms. The crystal packing of
the even-numbered diacids displays some similarity to that of
(I). The phosphonic acid sites are also arranged in hydrogen-
bonded monolayers, but the connection patterns and
symmetry relations, both inside the monolayers and between
them, are different. Due to the shortness and ¯exibility of the
aliphatic linker, the pillaring effect is not well expressed. The
triclinic polymorph of butanediphosphonic acid demonstrates
a two-dimensional interpenetration of two symmetry-inde-
pendent hydrogen-bonded [via R22(8)] ribbons. Numerous
hydrogen bonds crosslink two symmetry-independent mol-
ecular units of propanediphosphonic acid extending them into
a three-dimensional network.
Experimental
The synthesis of the title compound was carried out in two steps
starting from 4,40-dibromobiphenyl (6.27 g, 0.020 mol) and following
a known procedure (Wang et al., 2003). However, the method of
isolation of tetraethyl biphenyl-4,40-diphosphonate was modi®ed and
1,3-diisopropylbenzene and other volatile components of the reaction
mixture were removed under reduced pressure. The black residue
obtained was extracted with cyclohexane (3 Â 50 ml), ®ltered, and
left for crystallization. The crystals were ®ltered off and dried in air in
order to obtain the crude product (yield: 7.08 g, 83%), which was
recrystallized from cyclohexane (30 ml) to obtain pure tetraethyl
biphenyl-4,40-diphosphonate (yielded: 5.73 g, 67%, m.p. 354±356 K).
1H NMR (300 MHz, CDCl3): ꢄ 1.29 (t, J = 7.1 Hz, 12H, CH3), 3.96±
4.18 (m, 8H, OCH2), 7.58±7.65 (m, 4H, C6H4), 7.78±7.88 (m, 4H,
C6H4). 31P{H} NMR (121 MHz, CDCl3): ꢄ 20.05 (s). IR (KBr,
Figure 2
A view of the pillared crystal structure demonstrating the relationships
between the differently oriented aromatic stacks. Hydrogen bonds are
shown as dashed lines.
ꢅ
max, cm 1): 2986, 2904, 1134, 1249, 1055, 1025, 960, 795, 768, 563, 536.
Biphenyl-4,40-diphosphonic acid was obtained by re¯uxing tetraethyl
biphenyl-4,40-diphosphonate (4.09 g, 0.0959 mol) in concentrated
HCl (40 ml) and water (40 ml) and stirring for 12 h. The resulting
solid was ®ltered off, washed with water (5 ml) and dried in air to
1
yield the ®nal product, (I) (yield: 2.08 g, 93%). H NMR (300 MHz,
D2O-NaOD): ꢄ 7.65±7.85 (m, C6H4). 31P{H} NMR (121 MHz,
D2O-NaOD): ꢄ 12.83 (s). IR (KBr, ꢅmax, cm 1): 2929, 2710, 2269,
2203, 1601, 1140, 1047, 1001, 547, 525. Crystals suitable for X-ray
measurements were obtained from a water±methanol mixture (3:1
v/v). The solution was heated and stirred for 2 h. The resulting clear
solution was sealed in small glass containers and heated at 348 K for
2 d. Small plate-shaped crystals were obtained upon slow cooling (at
a rate of 1 K h 1). The melting point was measured on an Electro-
thermal Engineering Ltd Melting Point Apparatus IA9100. Five
independent measurements show that the crystals melt in the
temperature range 632±637 K.
Figure 3
Presentation of the two-dimensional hydrogen-bonded network and the
ring motifs generated. Hydrogen bonds are shown as dashed lines.
ꢀ
Â
Acta Cryst. (2007). C63, o434±o436
Prochniak et al. C12H12O6P2 o435

organic compounds
Crystal data
Table 2
Hydrogen-bond geometry (A, ).
ꢁ
Ê
3
Ê
V = 616.07 (17) A
C12H12O6P2
Mr = 314.16
Monoclinic, P21=c
Ê
a = 13.0552 (18) A
Z = 2
Mo Kꢃ radiation
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
1
ꢂ = 0.38 mm
T = 293 K
O1ÐHO1Á Á ÁO2ii
0.83 (3)
0.83 (3)
1.72 (3)
1.74 (3)
2.546 (2)
2.567 (2)
171 (3)
170 (3)
Ê
b = 7.0852 (10) A
O3ÐHO3Á Á ÁO2iii
Ê
c = 6.7287 (13) A
0.53 Â 0.35 Â 0.02 mm
ꢆ = 98.176 (14)ꢁ
Symmetry codes: (ii) x; y ‡ 12; z 21; (iii) x ‡ 1; y ‡ 21; z ‡ 12.
Data collection
Kuma KM-4 diffractometer with a
CCD area detector
Absorption correction: numerical
(X-SHAPE; Stoe & Cie, 1998)
Tmin = 0.873, Tmax = 0.988
6361 measured re¯ections
1246 independent re¯ections
879 re¯ections with I > 2ꢇ(I)
Rint = 0.044
Diffraction, 2003); program(s) used to solve structure: SHELXS97
(Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97
(Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); soft-
ware used to prepare material for publication: publCIF (Westrip,
2007).
Re®nement
R[F2 > 2ꢇ(F2)] = 0.036
wR(F2) = 0.088
S = 0.98
109 parameters
Only H-atom coordinates re®ned
Financial support from Wrocøaw University of Technology
is gratefully acknowledged.
3
Ê
Áꢈmax = 0.32 e A
3
Ê
0.49 e A
1246 re¯ections
Áꢈmin
=
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: AV3089). Services for accessing these data are
described at the back of the journal.
Table 1
Selected geometric parameters (A, ).
ꢁ
Ê
P1ÐO2
P1ÐO3
P1ÐO1
P1ÐC4
C1ÐC6
C1ÐC2
1.4920 (15)
1.5287 (17)
1.5329 (17)
1.777 (2)
1.382 (3)
1.386 (3)
C1ÐC1i
C2ÐC3
C3ÐC4
C4ÐC5
C5ÐC6
1.496 (4)
1.383 (3)
1.380 (3)
1.388 (3)
1.379 (3)
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ꢀ
Â
o436 Prochniak et al. C12H12O6P2
Acta Cryst. (2007). C63, o434±o436