A novel (3,4,10)-connected three-dimensional hydrogen-bonded supra­molecular network containing a cyclic water hexa­mer

The title compound, 4,4′-(1,1,1,3,3,3-hexa­fluoro­isopropyl­idene)diphthalic acid hexa­hydrate, C₁₉H₁₀F₆O₈·6H₂O, crystallizes in the centrosymmetric space group Pbcn, with half of the diphthalic acid residue and three water mol­ecules in the asymmetric unit. The organic mol­ecule is located on a crystallographic twofold axis. In the solid, cyclic water hexa­mers in chair conformations have crystallographically imposed inversion symmetry. Strong O—H...O hydrogen bonds between the hexa­mers and organic mol­ecules result in a unique three-dimensional supra­molecular network [O...O = 2.554 (2)–2.913 (2) Å]. This compound represents the first example of a (3,4,4,10)-connected four-nodal supra­molecular topology with the Schläfli symbol (4³.5.6.7)₂(4³.5².7)₂(4³)₂(4⁶.5⁶.6².7⁸.8¹⁴.9⁹).

S1. Comment

Great attention have been paid to small water clusters both in theoretical and experimental studies not only with the aim to understand hydrogen-bonding interactions and the behavior of bulk water, but also due to their fascinating topology when associated with organic molecules or metal-organic frameworks (Ludwig, 2001; Ugalde et al., 2000; Maheshwary et al., 2001; Chesnut, 2002; Sadlej et al., 1999; Custelcean et al., 2000; López et al., 2008). Many discrete water clusters, including tetramers, hexamers, octamers, decamers and higher clusters, have been identified. Among the water clusters, cyclic hexamers are of special interest because they are the building blocks of ice I_h (reference?) and expected to be relevant for the structure of liquid water. Theoretical calculations suggest that several different isomers for the water hexamer, such as ring, book, cage, cyclic and prism, represent nearly isoenergetic clusters (Ludwig, 2001; Chesnut, 2002). However, understanding how the water clusters link into higher dimensional networks is still challenging. Recently, water clusters associated with organic, inorganic, or metal–organic frameworks have been studied. One-dimensional aggregates such as water chains and tapes and a few examples of two- or three-dimensional polymers (Wang et al., 2006; Michaelides et al., 2003; Hu et al., 2007; Mukhopadhyay et al., 2005; Ye et al., 2004; Neogi et al., 2005; Zheng et al., 2005; Ghosh et al., 2004; Ghosh et al., 2005; Ghosh et al., 2003) have been described. In this contribution, we report the synthesis of the title compound under hydrothermal conditions, which contains an unexpected cyclic water hexamer in a chair conformation. Interestingly, an unique three-dimensional supramolecular network is formed by strong intermolecular O—H···O hydrogen bonds between these hexamers and the large organic residue. To our knowledge, this compound is the first example for a (3,4,4,10)-connected 4-nodal supramolecular topology associated with the Schläfli symbol (4³.5.6.7)₂(4³.5².7)₂(4³)₂(4⁶.5⁶.6².7⁸.8¹⁴.9⁹).

The asymmetric unit of (I) consists of one half the 4,4'-(hexafluoroisopropylidene)bis(phthalic acid) (H₄hfipdpt) molecule and three water molecules (Fig. 1). The benzene rings of the bent H₄hfipdpt molecule subtend a dihedral angle of 65.8(?)°. As shown in Fig. 2, the carboxylate groups of H₄hfipdpt adopt syn–syn 1,3-µ₂-carboxylate and 1,1,3-µ₃-carboxylate coordination modes, which are crosslinked by different cyclic hexameric water clusters via strong O—H···O intermolecular hydrogen bonds. In each cyclic hexamer unit, the average O···O distance is 2.817(?)Å, which is in the range of the corresponding values in ice I_h (2.759(?)Å; Ludwig, 2001) at 183 K and in liquid water (2.85(?)Å; Ludwig, 2001). The O···O···O angles range from 86.71(?) to 107.85(?)° and are smaller than the value of 109.3° in hexagonal ice (Ludwig, 2001; Michaelides et al., 2003). The water molecules (O5, O6 and O7) of the hexamers adopt 4-, 4- and 3-connected modes, respectively. The hexamers in the subunits are crosslinked with different organic H₄hfipdpt molecules via strong intermolecular O—H···O hydrogen bonds [O···O = 2.554 (2)–2.913 (2)Å], which give rise to a unique three-dimensional hydrogen-bonded supramolecular network (Fig. 3). The geometric parameters of the hydrogen bonds are listed in Table 1. The resulting three-dimensional supramolecular framework exhibits an interesting (3,4,4,10)-connected topology. A calculation of the vertex symbol with the help of the program TOPOS (Blatov et al., 2000) shows that the title compound exhibits a unique (3,4,4,10)-connected 4-nodal supramolecular topology with the Schläfli symbol (4³.5.6.7)₂(4³.5².7)₂(4³)₂(4⁶.5⁶.6².7⁸.8¹⁴.9⁹) (Fig. 4).

The FT–IR spectrum was interpreted in the light of the structural results. The stretching frequency of the O—H bonds was observed at ca 3540 and 3400 cm^-1, which is both due to the hexameric water cluster and the carboxyl group. The first peak is close to the value of 3490 cm^-1 reported for liquid water, while the second peak is slightly greater than the value of the reported cyclic water hexamer (3335 cm^-1) formed in liquid helium and the measured band at 3359 cm^-1 for the hexamer in an organic molecular crystal host because of the co-operative effects between the clusters and organic molecules (Custelcean et al., 2000; Michaelides et al., 2003; Buck & Huisken, 2000).

Related literature

For related literature, see:

S2. Experimental

A mixture of Pb(NO₃)₂ (108.7 mg, 0.33 mmol), 4,4'-bipyridine (18.8 mg, 0.12 mmol) and 4,4'-(hexafluoroisopropylidene)bis(phthalic anhydride) (69.6 mg, 0.16 mmol) in H₂O (8 ml) was sealed in a 25 ml Teflon-lined stainless steel reactor and heated at 443 K for 72 h. A crop of colorless single crystals of the title compound was obtained after cooling the solution to room temperature. Platelet-shaped crystals were collected and washed with distilled water. The yield is ca 55% based on 4,4'-(hexafluoroisopropylidene)bis(phthalic anhydride). IR (KBr, ν/cm^-1): 3540 (vs), 3400 (vs), 2930 (w), 2827 (w), 2653 (w), 2549 (w), 1973 (m), 1713 (vs), 1312 (w), 1254 (w), 1234 (w), 1072 (s), 982 (s), 840 (s), 795 (m), 750 (w), 703 (w), 658 (w), 600 (w).

S3. Refinement

All water H atoms were positioned from Fourier difference maps and refined subject to the constraint O—H = 0.82Å. The remaining H atoms were positioned geometrically and allowed to ride on their respective parent atoms at distances of C—H = 0.93Å and O—H = 0.82Å (for the carboxyl group), and with U_iso(H) = 1.2U_eq(C) or U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL'(Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The symmetric unit of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry code: (i) -x, y, -z+1/2.]
	Fig. 2. Perspective view showing the (3,4,4)-connected modes of hexamers, which are crosslinked with H4hfipdpt via strong intermolecular O—H···O hydrogen bonds. The hexamer, highlight in blue color, consist of the atoms (O5, O6, O7, O5^i, O6^i, O7^i). [Symmetry codes: (i) -x, y, -z+1/2; (ii) -x, 1-y, 1-z; (iii) -x+1/2, 0-y+1/2, z+1/2; (iv) x-0.5, y+1/2, -z+1/2; (v) 1-x, y, -z+1/2.]
	Fig. 3. The extended structure of the three-dimensional supramolecular network Of (I). All non-interacting H atoms have been omitted for clarity.
	Fig. 4. View of the (3,4,4,10)-connected four-nodal topology Five- and ten-connected nodes denote H4hfipdpt (blue in the electronic version of the paper) and all others are H2O (red).

4,4'-(1,1,1,3,3,3-hexafluoroisopropylidene)diphthalic acid hexahydrate

Crystal data

C19H10F6O8·6H2O	F(000) = 1208
Mr = 588.37	Dx = 1.558 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 22570 reflections
a = 6.9425 (14) Å	θ = 3.3–27.5°
b = 12.366 (3) Å	µ = 0.16 mm^−1
c = 29.220 (6) Å	T = 298 K
V = 2508.5 (9) Å^3	Platelet, colorless
Z = 4	0.46 × 0.39 × 0.09 mm

Data collection

Rigaku R-AXIS RAPID diffractometer	2852 independent reflections
Radiation source: sealed tube	2030 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.067
ω scans	θmax = 27.5°, θmin = 3.3°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = −9→7
Tmin = 0.929, Tmax = 0.986	k = −16→16
22570 measured reflections	l = −37→37

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.051	H-atom parameters constrained
wR(F^2) = 0.109	w = 1/[σ^2(Fo^2) + (0.0394P)^2 + 1.3747P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max < 0.001
2852 reflections	Δρmax = 0.20 e Å^−3
178 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0063 (8)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
F1	0.2076 (2)	0.52973 (11)	0.23850 (5)	0.0637 (5)
F2	0.32395 (18)	0.39289 (13)	0.27426 (4)	0.0575 (4)
F3	0.1190 (2)	0.49568 (12)	0.30730 (4)	0.0633 (5)
O1	0.3582 (2)	0.02704 (14)	0.10885 (5)	0.0548 (5)
O2	0.1164 (2)	0.08433 (12)	0.06539 (5)	0.0462 (4)
H2B	0.1557	0.0374	0.0479	0.069*
O3	0.4520 (3)	0.25157 (15)	0.07696 (5)	0.0632 (5)
O4	0.5445 (2)	0.36972 (13)	0.12927 (5)	0.0533 (5)
H4B	0.6269	0.3838	0.1101	0.080*
O5	1.0118 (2)	0.28172 (13)	0.01698 (5)	0.0504 (4)
H1	0.9807	0.2689	−0.0096	0.076*
H2	1.0313	0.2246	0.0305	0.076*
O6	0.8192 (2)	0.42691 (13)	0.07227 (5)	0.0505 (4)
H3	0.9150	0.4553	0.0836	0.076*
H4	0.8693	0.3771	0.0580	0.076*
O7	1.2915 (3)	0.44327 (13)	0.00541 (5)	0.0540 (5)
H5	1.2081	0.3974	0.0099	0.081*
H6	1.2514	0.4791	−0.0162	0.081*
C1	0.2269 (3)	0.08807 (16)	0.10163 (6)	0.0336 (5)
C2	0.1645 (3)	0.17074 (15)	0.13612 (6)	0.0304 (4)
C3	0.0027 (3)	0.14948 (16)	0.16214 (7)	0.0381 (5)
H3A	−0.0733	0.0897	0.1553	0.046*
C4	−0.0475 (3)	0.21627 (16)	0.19823 (7)	0.0354 (5)
H4A	−0.1569	0.2008	0.2154	0.043*
C5	0.0633 (3)	0.30591 (15)	0.20908 (6)	0.0267 (4)
C6	0.2207 (3)	0.33007 (15)	0.18159 (6)	0.0289 (4)
H6A	0.2932	0.3917	0.1876	0.035*
C7	0.2716 (3)	0.26332 (15)	0.14520 (6)	0.0291 (4)
C8	0.4323 (3)	0.29321 (17)	0.11384 (6)	0.0349 (5)
C9	0.0000	0.3763 (2)	0.2500	0.0276 (6)
C10	0.1639 (3)	0.44915 (18)	0.26746 (7)	0.0431 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0853 (11)	0.0453 (8)	0.0605 (9)	−0.0314 (8)	0.0293 (8)	−0.0090 (7)
F2	0.0335 (7)	0.0948 (11)	0.0443 (7)	−0.0123 (7)	0.0000 (6)	−0.0126 (7)
F3	0.0714 (10)	0.0733 (10)	0.0452 (8)	−0.0304 (8)	0.0230 (7)	−0.0328 (7)
O1	0.0591 (11)	0.0620 (11)	0.0432 (9)	0.0254 (9)	−0.0043 (8)	−0.0092 (8)
O2	0.0580 (10)	0.0459 (9)	0.0348 (8)	0.0108 (8)	−0.0097 (7)	−0.0139 (7)
O3	0.0741 (12)	0.0795 (12)	0.0359 (8)	−0.0297 (10)	0.0256 (9)	−0.0207 (9)
O4	0.0482 (9)	0.0673 (11)	0.0446 (9)	−0.0255 (8)	0.0206 (8)	−0.0167 (8)
O5	0.0684 (11)	0.0458 (9)	0.0370 (8)	−0.0036 (8)	−0.0073 (8)	−0.0028 (7)
O6	0.0381 (9)	0.0590 (10)	0.0544 (10)	−0.0132 (7)	0.0103 (7)	−0.0102 (8)
O7	0.0696 (12)	0.0512 (10)	0.0412 (8)	−0.0138 (9)	0.0040 (8)	−0.0091 (7)
C1	0.0402 (11)	0.0328 (10)	0.0277 (9)	0.0006 (9)	0.0021 (9)	0.0005 (8)
C2	0.0355 (11)	0.0329 (10)	0.0229 (9)	0.0012 (8)	0.0011 (8)	−0.0002 (8)
C3	0.0421 (12)	0.0360 (11)	0.0362 (11)	−0.0111 (9)	0.0056 (9)	−0.0066 (9)
C4	0.0345 (11)	0.0397 (11)	0.0321 (10)	−0.0083 (9)	0.0094 (9)	−0.0023 (9)
C5	0.0295 (10)	0.0288 (9)	0.0218 (8)	0.0006 (8)	0.0025 (7)	0.0003 (7)
C6	0.0306 (10)	0.0313 (10)	0.0249 (9)	−0.0033 (8)	0.0019 (8)	−0.0021 (8)
C7	0.0291 (10)	0.0348 (10)	0.0234 (9)	−0.0005 (8)	0.0022 (8)	0.0004 (8)
C8	0.0373 (11)	0.0395 (11)	0.0280 (10)	−0.0023 (9)	0.0055 (9)	−0.0032 (8)
C9	0.0291 (14)	0.0280 (13)	0.0257 (13)	0.000	0.0051 (11)	0.000
C10	0.0509 (14)	0.0456 (13)	0.0329 (11)	−0.0144 (11)	0.0133 (10)	−0.0106 (9)

Geometric parameters (Å, º)

F1—C10	1.342 (3)	C1—C2	1.500 (3)
F2—C10	1.326 (3)	C2—C3	1.381 (3)
F3—C10	1.335 (2)	C2—C7	1.391 (3)
O1—C1	1.202 (2)	C3—C4	1.384 (3)
O2—C1	1.309 (2)	C3—H3A	0.9300
O2—H2B	0.8200	C4—C5	1.386 (3)
O3—C8	1.202 (2)	C4—H4A	0.9300
O4—C8	1.306 (2)	C5—C6	1.388 (3)
O4—H4B	0.8200	C5—C9	1.543 (2)
O5—H1	0.8210	C6—C7	1.392 (3)
O5—H2	0.8211	C6—H6A	0.9300
O6—H3	0.8211	C7—C8	1.490 (3)
O6—H4	0.8211	C9—C10	1.538 (3)
O7—H5	0.8210	C9—C10^i	1.538 (3)
O7—H6	0.8209	C9—C5^i	1.543 (2)
C1—O2—H2B	109.5	C5—C6—H6A	119.5
C8—O4—H4B	109.5	C7—C6—H6A	119.5
H1—O5—H2	109.5	C2—C7—C6	119.88 (17)
H3—O6—H4	100.5	C2—C7—C8	119.15 (16)
H5—O7—H6	104.8	C6—C7—C8	120.85 (17)
O1—C1—O2	124.38 (19)	O3—C8—O4	123.50 (19)
O1—C1—C2	121.95 (18)	O3—C8—C7	122.02 (19)
O2—C1—C2	113.47 (17)	O4—C8—C7	114.45 (16)
C3—C2—C7	119.11 (17)	C10—C9—C10^i	108.3 (2)
C3—C2—C1	118.38 (18)	C10—C9—C5	112.12 (11)
C7—C2—C1	122.32 (17)	C10^i—C9—C5	106.50 (11)
C2—C3—C4	120.70 (18)	C10—C9—C5^i	106.50 (11)
C2—C3—H3A	119.7	C10^i—C9—C5^i	112.12 (11)
C4—C3—H3A	119.7	C5—C9—C5^i	111.3 (2)
C3—C4—C5	120.77 (18)	F2—C10—F3	106.93 (19)
C3—C4—H4A	119.6	F2—C10—F1	107.12 (18)
C5—C4—H4A	119.6	F3—C10—F1	106.41 (18)
C4—C5—C6	118.48 (17)	F2—C10—C9	111.25 (18)
C4—C5—C9	118.04 (16)	F3—C10—C9	111.63 (16)
C6—C5—C9	123.43 (16)	F1—C10—C9	113.13 (18)
C5—C6—C7	120.93 (17)

Symmetry code: (i) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2B···O7^ii	0.82	1.74	2.554 (2)	171
O4—H4B···O6	0.82	1.81	2.629 (2)	173
O5—H1···O3^iii	0.82	1.99	2.806 (2)	170
O5—H2···O2^iv	0.82	2.10	2.913 (2)	173
O6—H3···O1^v	0.82	1.95	2.773 (2)	178
O6—H4···O5	0.82	1.95	2.760 (2)	169
O7—H5···O5	0.82	1.99	2.806 (2)	176
O7—H6···O6^vi	0.82	2.07	2.884 (2)	174

Symmetry codes: (ii) −x+3/2, y−1/2, z; (iii) x+1/2, −y+1/2, −z; (iv) x+1, y, z; (v) −x+3/2, y+1/2, z; (vi) −x+2, −y+1, −z.