5-Fluoro­uracil–2,2,2-trifluoro­ethanol (1/1)

Hulme, A.T.; Tocher, D.A.

doi:10.1107/S1600536805032198

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 61| Part 11| November 2005| Pages o3661-o3663

https://doi.org/10.1107/S1600536805032198

5-Fluorouracil–2,2,2-trifluoroethanol (1/1)

Ashley T. Hulme ^a ^* and Derek A. Tocher ^a

^aChristopher Ingold Laboratory, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, England
^*Correspondence e-mail: a.hulme@ucl.ac.uk

(Received 3 October 2005; accepted 10 October 2005; online 15 October 2005)

The title compound, C₄H₃FN₂O₂·C₂H₃F₃O, crystallizes with one 5-fluorouracil and one 2,2,2-trifluoroethanol molecule in the asymmetric unit. The 5-fluorouracil molecules are linked into a chain primarily via N—H⋯O hydrogen bonds, with the 2,2,2-trifluoroethanol molecules attached to this via O—H⋯O hydrogen bonds.

Comment

The title compound, (I), is the fourth solvate of 5-fluorouracil obtained in the course of a polymorph screen. The previously published structures contained 1,4-dioxane (Hulme & Tocher, 2004a ), dimethylformamide (Hulme & Tocher, 2004b ) and dimethylsulfoxide (Hulme & Tocher, 2004c ).

One fluorouracil molecule and one 2,2,2-trifluoroethanol molecule are present in the asymmetric unit of (I) (Fig. 1). This structure bears no similarity to any of the previously reported solvate structures of 5-fluorouracil.

The 5-fluorouracil molecules of (I) form a ribbon propagated by the screw axis, with trifluoroethanol molecules attached to the outer edges of the ribbon. Each 5-fluorouracil molecule forms two R₂²(8) hydrogen bonds with adjacent 5-fluorouracil molecules, as shown in Fig. 2; details are given in Table 1. A further hydrogen bond joins the 5-fluorouracil carbonyl O atom, unused in forming the ribbon, with the hydroxyl group of the trifluoroethanol molecule (Fig. 2 and Table 1).

The ribbons stack upon one another parallel to [001] (Fig. 3). Close F⋯F contacts are an interesting feature present in this structure. There is a short F⋯F contact within the ribbon, F9⋯F12^iv [2.891 (2) Å; symmetry code: (iv) x, y + 1, z], which acts as a weak stabilizing interaction for the ribbon motif. A short contact is also present between trifluoromethyl groups in ribbons of adjacent layers, viz. F12⋯F13^v [3.001 (2) Å; symmetry code: (v) −x, y − $[{1\over 2}]$ , −z]. A third short F⋯F contact, F9⋯F13^vi [2.906 (2) Å; symmetry code: (vi) 1 − x, $[{1\over 2}]$ + y, −z], also links ribbons in adjacent layers. These interlayer F⋯F contacts are the only interactions between the layers.

Figure 1
A view of the asymmetric unit of (I)

. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The structure of the ribbon, showing R₂²(8) hydrogen-bonded dimers and the hydrogen bonds (dotted lines) between 5-fluorouracil and 2,2,2-trifluoroethanol.

Figure 3
The stacking of the ribbons side-by-side into layers. Hydrogen bonds are shown as dotted lines.

Experimental

Typically, crystals of length 2–5 mm were grown from a solution of 5-fluorouracil in 2,2,2-trifluoroethanol by solvent evaporation. Attempts to cut crystals to a suitable size for X-ray diffraction led to shattering. Consequently, a large crystal with a longest dimension of 1.49 mm was mounted and used for the experiment.

Crystal data

C₄H₃FN₂O₂·C₂H₃F₃O
M_r = 230.13
Monoclinic, P 2₁
a = 5.3976 (6) Å
b = 6.7062 (8) Å
c = 12.1098 (14) Å
β = 102.807 (2)°
V = 427.44 (9) Å³
Z = 2
D_x = 1.788 Mg m⁻³
Mo Kα radiation
Cell parameters from 2027 reflections
θ = 3.5–28.1°
μ = 0.19 mm⁻¹
T = 150 (2) K
Lath, colourless
1.49 × 0.34 × 0.17 mm

Data collection

Bruker SMART APEX diffractometer
ω rotation scans with narrow frames
Absorption correction: multi-scan(SADABS; Sheldrick, 1996 )T_min = 0.760, T_max = 0.968
2634 measured reflections
1090 independent reflections
1060 reflections with I > 2σ(I)
R_int = 0.017
θ_max = 28.2°
h = −7 → 6
k = −8 → 8
l = −15 → 15

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.028
wR(F²) = 0.074
S = 1.04
1090 reflections
160 parameters
All H-atom parameters refined
w = 1/[σ²(F_o²) + (0.0503P)² + 0.0688P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3⋯O7ⁱ	0.87 (3)	1.92 (3)	2.786 (2)	173 (2)
N1—H1⋯O7ⁱⁱ	0.82 (3)	2.20 (3)	2.924 (2)	147 (2)
N1—H1⋯O11ⁱⁱⁱ	0.82 (3)	2.43 (3)	3.037 (2)	132 (2)
O11—H11⋯O8	0.76 (3)	2.00 (3)	2.7507 (19)	171 (3)
Symmetry codes: (i) $[-x+3, y-{\script{1\over 2}}, -z+1]$ ; (ii) $[-x+3, y+{\script{1\over 2}}, -z+1]$ ; (iii) x+1, y+1, z.

All H atoms were located in a difference map and were refined isotropically, with C—H distances between 0.89 (3) and 0.97 (2) Å. See Table 1 for N—H and O—H bond distances.

Data collection: SMART (Bruker, 1998 ); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536805032198/tk6270sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536805032198/tk6270Isup2.hkl

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: SHELXL97.

5-fluorouracil–2,2,2-trifluoroethanol (1/1) top

Crystal data top

C₄H₃FN₂O₂·C₂H₃F₃O	F(000) = 232
M_r = 230.13	D_x = 1.788 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P2yb	Cell parameters from 2027 reflections
a = 5.3976 (6) Å	θ = 3.5–28.1°
b = 6.7062 (8) Å	µ = 0.19 mm⁻¹
c = 12.1098 (14) Å	T = 150 K
β = 102.807 (2)°	Plate, colourless
V = 427.44 (9) Å³	1.49 × 0.34 × 0.17 mm
Z = 2

Data collection top

Bruker SMART APEX diffractometer	1090 independent reflections
Radiation source: fine-focus sealed tube	1060 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.017
ω rotation with narrow frames scans	θ_max = 28.2°, θ_min = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→6
T_min = 0.760, T_max = 0.968	k = −8→8
2634 measured reflections	l = −15→15

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.028	Hydrogen site location: difference Fourier map
wR(F²) = 0.074	All H-atom parameters refined
S = 1.04	w = 1/[σ²(F_o²) + (0.0503P)² + 0.0688P] where P = (F_o² + 2F_c²)/3
1090 reflections	(Δ/σ)_max < 0.001
160 parameters	Δρ_max = 0.31 e Å⁻³
1 restraint	Δρ_min = −0.24 e Å⁻³

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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 (Å²) top

	x	y	z	U_iso*/U_eq
F9	0.57881 (18)	0.57165 (18)	0.24396 (9)	0.0274 (3)
O7	1.5295 (2)	0.59410 (19)	0.49255 (11)	0.0208 (3)
O8	0.8249 (2)	0.2336 (2)	0.34213 (11)	0.0248 (3)
N1	1.1899 (3)	0.7582 (2)	0.38580 (12)	0.0209 (3)
H1	1.271 (5)	0.862 (5)	0.393 (2)	0.037 (7)*
N3	1.1724 (3)	0.4198 (2)	0.41781 (12)	0.0191 (3)
H3	1.254 (4)	0.313 (4)	0.446 (2)	0.020 (5)*
C2	1.3099 (3)	0.5927 (3)	0.43551 (13)	0.0176 (3)
C4	0.9293 (3)	0.3969 (3)	0.35374 (13)	0.0186 (3)
C5	0.8192 (3)	0.5820 (3)	0.30489 (14)	0.0200 (3)
C6	0.9461 (3)	0.7542 (3)	0.32056 (14)	0.0216 (3)
H6	0.881 (4)	0.870 (4)	0.2910 (18)	0.017 (5)*
F11	0.5628 (3)	−0.0249 (3)	0.08309 (13)	0.0571 (5)
F12	0.2214 (3)	−0.1821 (2)	0.08921 (13)	0.0506 (4)
F13	0.2185 (3)	0.0332 (3)	−0.04178 (11)	0.0533 (4)
O11	0.3333 (3)	0.1118 (2)	0.25622 (11)	0.0299 (3)
H11	0.466 (5)	0.155 (5)	0.275 (2)	0.033 (7)*
C11	0.2408 (4)	0.1569 (3)	0.14144 (16)	0.0289 (4)
H12	0.056 (5)	0.155 (4)	0.126 (2)	0.030 (6)*
H13	0.316 (5)	0.277 (5)	0.121 (2)	0.041 (7)*
C12	0.3116 (4)	−0.0040 (4)	0.06811 (17)	0.0323 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
F9	0.0195 (5)	0.0296 (6)	0.0290 (5)	0.0011 (5)	−0.0037 (4)	0.0016 (5)
O7	0.0193 (5)	0.0154 (5)	0.0257 (6)	−0.0009 (5)	0.0005 (4)	−0.0018 (5)
O8	0.0202 (6)	0.0184 (6)	0.0335 (6)	−0.0034 (5)	0.0009 (5)	−0.0011 (5)
N1	0.0224 (7)	0.0126 (7)	0.0267 (7)	−0.0009 (6)	0.0034 (5)	0.0009 (6)
N3	0.0192 (6)	0.0140 (6)	0.0226 (6)	0.0014 (5)	0.0015 (5)	0.0019 (6)
C2	0.0199 (7)	0.0144 (7)	0.0181 (7)	−0.0015 (7)	0.0038 (5)	−0.0022 (6)
C4	0.0189 (7)	0.0174 (8)	0.0192 (7)	−0.0004 (6)	0.0036 (6)	−0.0015 (6)
C5	0.0179 (7)	0.0217 (8)	0.0194 (7)	0.0020 (7)	0.0020 (6)	0.0005 (6)
C6	0.0226 (8)	0.0187 (8)	0.0227 (7)	0.0041 (7)	0.0031 (6)	0.0042 (7)
F11	0.0388 (7)	0.0803 (13)	0.0542 (9)	0.0108 (8)	0.0149 (6)	−0.0146 (8)
F12	0.0700 (10)	0.0305 (7)	0.0444 (8)	−0.0085 (7)	−0.0023 (7)	−0.0050 (6)
F13	0.0697 (9)	0.0655 (11)	0.0216 (6)	−0.0002 (8)	0.0032 (6)	−0.0015 (6)
O11	0.0266 (6)	0.0391 (8)	0.0227 (6)	−0.0110 (6)	0.0026 (5)	−0.0024 (6)
C11	0.0284 (8)	0.0287 (10)	0.0270 (8)	0.0003 (8)	0.0003 (7)	0.0012 (8)
C12	0.0347 (9)	0.0361 (10)	0.0242 (8)	0.0000 (9)	0.0025 (7)	−0.0022 (8)

Geometric parameters (Å, º) top

F9—C5	1.3448 (19)	C5—C6	1.335 (3)
O7—C2	1.233 (2)	C6—H6	0.89 (3)
O8—C4	1.225 (2)	F11—C12	1.335 (3)
N1—C2	1.357 (2)	F12—C12	1.336 (3)
N1—C6	1.377 (2)	F13—C12	1.338 (2)
N1—H1	0.82 (3)	O11—C11	1.402 (2)
N3—C2	1.368 (2)	O11—H11	0.76 (3)
N3—C4	1.377 (2)	C11—C12	1.500 (3)
N3—H3	0.87 (3)	C11—H12	0.97 (2)
C4—C5	1.445 (2)	C11—H13	0.96 (3)

C2—N1—C6	122.69 (16)	C5—C6—H6	123.5 (14)
C2—N1—H1	118 (2)	N1—C6—H6	116.9 (14)
C6—N1—H1	119.7 (19)	C11—O11—H11	108 (2)
C2—N3—C4	126.78 (15)	O11—C11—C12	110.50 (17)
C2—N3—H3	115.3 (16)	O11—C11—H12	108.0 (15)
C4—N3—H3	117.7 (16)	C12—C11—H12	105.2 (16)
O7—C2—N1	123.20 (16)	O11—C11—H13	111.0 (17)
O7—C2—N3	121.01 (16)	C12—C11—H13	106.0 (18)
N1—C2—N3	115.79 (14)	H12—C11—H13	116 (2)
O8—C4—N3	121.37 (16)	F11—C12—F12	106.4 (2)
O8—C4—C5	125.73 (15)	F11—C12—F13	107.51 (17)
N3—C4—C5	112.90 (15)	F12—C12—F13	106.53 (18)
C6—C5—F9	121.65 (16)	F11—C12—C11	112.29 (18)
C6—C5—C4	122.26 (14)	F12—C12—C11	112.26 (17)
F9—C5—C4	116.08 (15)	F13—C12—C11	111.48 (18)
C5—C6—N1	119.57 (16)

C6—N1—C2—O7	178.79 (15)	O8—C4—C5—F9	1.7 (2)
C6—N1—C2—N3	−0.6 (2)	N3—C4—C5—F9	−178.07 (13)
C4—N3—C2—O7	−178.17 (15)	F9—C5—C6—N1	178.49 (14)
C4—N3—C2—N1	1.2 (2)	C4—C5—C6—N1	−0.4 (2)
C2—N3—C4—O8	178.87 (15)	C2—N1—C6—C5	0.2 (2)
C2—N3—C4—C5	−1.3 (2)	O11—C11—C12—F11	−61.2 (2)
O8—C4—C5—C6	−179.36 (17)	O11—C11—C12—F12	58.7 (2)
N3—C4—C5—C6	0.8 (2)	O11—C11—C12—F13	178.12 (16)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···O7ⁱ	0.87 (3)	1.92 (3)	2.786 (2)	173 (2)
N1—H1···O7ⁱⁱ	0.82 (3)	2.20 (3)	2.924 (2)	147 (2)
N1—H1···O11ⁱⁱⁱ	0.82 (3)	2.43 (3)	3.037 (2)	132 (2)
O11—H11···O8	0.76 (3)	2.00 (3)	2.7507 (19)	171 (3)

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

Acknowledgements

The authors acknowledge the EPSRC's UK Basic Technology Programme for supporting `Control and Prediction of the Organic Solid State'.

References

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