Crystal structure of C17H20FN3O 3 2+ ?cuBr4 2- ?h 2O

Article abstract of DOI:10.1134/S0022476611040251

A new compound C₁₇H₂₀FN₃O ₃ ²⁺ ?CuBr ₄ ^2- ?H₂O is synthesized in the crystal form, where C₁₇H₁₈FN ₃O₃ (CfH, ciprofloxacin) is 4-oxo-7-(1-piperazinyl)-6- fluoro-1-cyclopropyl-1,4-dihydroquinoline-3-carboxylic acid. Crystallographic data of ciprofloxacinium tetrabromocuprate(II) monohydrate, C₁₇H ₂₂Br₄CuFN₃O₄: a = 8.214(1) A, b = 10.781(2) A, c = 13.703(2) A, α = 85.144(2)°, β = 79.119(2)°, γ = 84.018(2)°, V = 1182.5(4) A³, P 1 space group, Z = 2. Supramolecular architecture of the crystal differs from that established for C₁₇H₂₀FN₃O ₃ ²⁺ ?CuCl ₄ ^2- ?H₂O by the absence of π-π interactions of the aromatic rings of CfH ₃ ²⁺ ions and also the structural motifs formed by intermolecular hydrogen bonds.

Full text of DOI:10.1134/S0022476611040251

Journal of Structural Chemistry. Vol. 52, No. 4, pp. 809-812, 2011
Original Russian Text Copyright © 2011 by A. D. Vasiliev and N. N. Golovnev
2+
2−
4
CRYSTAL STRUCTURE OF C17H20FN3O ⋅CuBr ⋅H2O
3
© A. D. Vasiliev and N. N. Golovnev
UDC 548.737
2+
2−
A new compound C H FN O ⋅CuBr ⋅H O is synthesized in the crystal form, where C H FN O
17 20 3 2 17 18 3 3
3
4
(CfH, ciprofloxacin) is 4-oxo-7-(1-piperazinyl)-6-fluoro-1-cyclopropyl-1,4-dihydroquinoline-3-carboxylic
acid. Crystallographic data of ciprofloxacinium tetrabromocuprate(II) monohydrate, C H Br CuFN O :
17 22
4
3
4
a = 8.214(1) Å, b = 10.781(2) Å, с = 13.703(2) Å, α = 85.144(2)°, β = 79.119(2)°, γ = 84.018(2)°, V =
3
1182.5(4) Å , P1 space group, Z = 2. Supramolecular architecture of the crystal differs from that
2+
2−
established for C H FN O ⋅CuCl ⋅H O by the absence of π–π interactions of the aromatic rings of
17 20 3 2
3
4
2+
CfH ions and also the structural motifs formed by intermolecular hydrogen bonds.
3
Keywords: fluoroquinolones, ciprofloxacin, bromide, copper(II), crystal structure, hydrogen bonds.
Fluoroquinolones have recently aroused considerable interest of the scientific society because of practical and
fundamental aspects. In crystal design, hydrogen bonds are considered as key supramolecular interactions. The development
of the concept of supramolecular synthons allows the crystals to be classified and presented in the form of supramolecular
units [1, 2]. Intermolecular π–π interactions of aromatic rings can also play an important role in the antibacterial activity of
fluoroquinolones. One of the most effective representatives of fluoroquinolones is ciprofloxacin (CfH), C H FN O —
17 18
3
3
4-oxo-7-(1-piperazinyl)-6-fluoro-1-cyclopropyl-1,4-dihydroquinoline-3-carboxylic acid, which determines its comprehensive
2+
study [3]. The structures of ionic ciprofloxacin compounds containing the CfH cation are the least studied [4]. We have
3
2+
2−
previously established the structure of C H FN O ⋅CuCl ⋅H O [5]. In order to systematically investigate the effect of the
17 20 3 2
3
4
2+
2−
nature of a halide ligand on crystal packing and its structural motifs, a new compound C H FN O ⋅CuBr ⋅H O (I) was
17 20 3 2
3
4
synthesized (C H CuBr FN O , ciprofloxacinium tetrabromocuprate(II) monohydrate — CfH [CuBr ]⋅H O) and its crystal
18 22 4 3 3 2
4
4
and molecular structure was determined.
Experimental. CfH in the form of white powder was isolated on storing or heating in air of an ammonia solution of
ciprofloxacinium chloride monohydrate CfH⋅HCl⋅H O (Ranbaxia, India) with pH 11-12 to pH 8. It was filtered off, several
2
times washed with distilled water and dried in air to constant weight.
Synthesis of C H FN O ⋅CuBr2− ⋅H O. 0.30 g of ciprofloxacin were dissolved in 3 ml of 7M HBr; then to the
2+
17 20
3
2
3
4
obtained solution CuO (chemically pure) was slowly added to the molar ratio CuO:CfH = 2:1. Black crystals of the
compound were isolated on evaporation of the solution. When selecting the medium acidity, we were guided by the data on
CfH protonation in strongly acidic solutions [6].
For the structural study we chose a crystal with the dimensions of 0.36×0.18×0.08 mm. Reflection intensities were
measured on a single crystal X-ray SMART APEX II diffractometer equipped with a CCD detector (Bruker AXS), MoK
α
radiation. Experimental absorption corrections were taken into account in the SADABS program [7] by the multi-scan
Siberian Federal University, Krasnoyarsk; ngolovnev@sfu-kras.ru. Translated from Zhurnal Strukturnoi Khimii,
Vol. 52, No. 4, pp. 829-832, July-August, 2011. Original article submitted October 29, 2010.
0022-4766/11/5204-0809
809

2+
2–
and CuBr ions with
Fig. 1. CfH
Fig. 2. Hydrogen bonds
Fig. 3. Hydrogen bonds of the
3
4
2+
2−
atom numbering. Hydrogen bonds are
shown by dashed lines.
of the CfH
ion.
are
CuBr ion.
4
3
Oxygen
atoms
denoted by bold circles;
hydrogen atoms not
involved in the bonds are
omitted. (i) 2–x, –y, 1–z;
(ii) 1+x, y, z; (iii) x–1,
1+y, z; (iv) x, 1+y, z.
method. The structure model was determined by direct methods (SHELXS [8]) and refined using the SHELXL program
package [9]. the positions of hydrogen atoms in ciprofloxacinium cations were found from electron density difference
syntheses and then refined in the idealized form. Table 1 lists the experimental parameters and structure refinement results.
The CIF file containing full information on the studied structure was deposited in CCDC under No. 795546, from
where it can be obtained on request at the following site: www.ccdc.cam.ac.uk/data_request/cif.
2+ 2−
Results and discussion. The molecular structure of I contains CfH and CuBr ions (Fig. 1). The latter are
3
4
strongly distorted tetrahedra. Though all Cu–Br distances fall within a narrow range of 2.361 Å to 2.391(1) Å; Br–Cu–Br
angles vary from 96.93° to 132.09(4)°.
2+
2−
The lengths of C–O, C–N, C–F, and C–C bonds coincid with those obtained for C H FN O ⋅CuCl ⋅H O [5]
17 20 3 2
3
4
2+
(II). Molecular С5–C6–C7–C8–C9–C10 (cycle 1) and N1–C2–C3–C4–C10–C9 (cycle 2) cycles in CfH are planar, while
3
the N2–C14–C15–N3–C16–C17 cycle has a chair conformation (Figs. 1-3). The terminal N3 nitrogen atom is protonated.
Hydrogen is bonded to the О1 atom that makes an intramolecular hydrogen bond with the О2 carbonyl oxygen of the
carboxylic group. The intramolecular hydrogen bond involving fluorine atoms forms another six-membered ring. Two
intramolecular motifs (synthons) S(6) correspond to them, which are typical of the ionic compounds of fluoroquinolones. The
parameters of intramolecular hydrogen bonds coincide within the error limits in compounds I and II.
Supramolecular motifs in I differ from those found previously in II (Figs. 2 and 3). The Br3 atoms of the
2−
neighboring CuBr ions are bound by intermolecular hydrogen bonds with two crystallization water molecules at once.
4
Consequently, an 8-membered cycle forms consists of two Br3 atoms and two H O molecules, to which the supramolecular
2
2
motif (synthon) R (8) corresponds. In compound II, intermolecular hydrogen bonds organize a 12-membered cycle of Cu,
2
4
Cl2, Cl4 atoms and H O molecules (plus centrosymmetric) [5], which corresponds to the motif (synthon) R (12). In I, Br2
4
2
810

TABLE 1. Experimental Data and Refinement Parameters for the Structure of I
Formula
Molecular weight
Temperature, K
Space group
Z
C H Br CuFN O
17 22 4 3 4
734.54
298
P 1
2
50
2θ , deg
max
a, b, c, Å
8.214(1), 10.781(2), 13.703(2)
85.144(2), 79.119(2), 84.018(2)
α, β, γ, deg
3
V, Å
1182.5(4)
3
2.063
ρ
calc
, g/cm
–1
7.718
μ, mm
Total number of measured reflections
Independent reflections
8780
4158
2435
Number of reflections with F > 4σ
F
h, k, l ranges
–9 ≤ h ≤ 9, –12 ≤ k ≤ 12, –16 ≤ l ≤ 16
Refinement results
2 2
W = [σ + (0,0244P) ] where P = (F + 2F )/3
2
2 –1
2
Weight refinement against F
0
c
Number of refined parameters
297
0.0424
0.0924
0.999
0.576
–0.516
0.008
R1 [F > 4σ(F )]
0 0
wR2
GOOF
3
(Δρ) , e/Å
max
3
(Δρ) , e/Å
min
(Δ/σ)
max
TABLE 2. Geometric Characteristics of D–H…A Hydrogen Bonds (bond lengths d, Å, angles, deg) and
Shortest Contacts in the Structure of I
А atom
D–H
d(D–H)
d(H…A)
d(D…A)
A
∠DHA
transformation
0.80(7)
1.0(1)
0.97
1.77(7)
1.8(1)
2.22(6)
2.9(1)
2.72(7)
2.49(7)
2.67(7)
2.71(7)
2.83
166(7)
142(8)
122(6)
117(6)
130(5)
166(7)
147(6)
156(7)
140
2.558(8)
2.624(7)
2.859(7)
3.471(4)
3.373(7)
3.369(7)
3.460(6)
3.553(6)
3.627(7)
3.724(7)
3.532(7)
Ow
O2
O3–H3
O1–H1
F
C14–H14A
O1–H1
Br3
Br2
Br4
Br3
Br3
Br2
Br1
Br1
1–x, –y, 1–z
x–1, 1+y, z
x, 1+y, z
1.0(1)
0.90(7)
0.90(7)
0.90(6)
0.90(6)
0.97
N3–H3A
N3–H3B
Ow–Hw1
Ow–Hw2
C13–H13A
C14–H14B
C16–H16B
2–x, –y, 1–z
1+x, y, z
x–1, 1+y, z
0.97
2.83
153
1–x, 1–y, –z
0.97
2.79
134
and Br4 atoms are hydrogen bonded to the N3 nitrogen atoms of two ciprofloxacin molecules, whereas Br1 and Br2 have
shortened distances to the hydrogen atoms at carbon atoms (Table 2, Fig. 3). Here yet another 8-membered cycle is formed,
2
which contains Cu, Br2, N3, H3A, C15, C14, H14B, and Br1 atoms (R (8)). According to [1, p.500], the hydrogen bond
2
formation should be taken into account already at d(D…A) ≤ 4 Å.
811

2+
Molecular CfH ions are related by inversion into pairs with a parallel arrangement of planar cycles 1 and 2.
3
However, according to [10], their shift with respect to each other is substantially larger (the minimum distance between the
centroids of the cycles of two molecules is 4.6 Å) than that in compound II (3.8 Å), which allows us to suppose the absence
2−
of the π–π interaction between them. This difference can be due to the packing features and larger sizes of CuBr as
4
2− 2−
compared to CuCl . The degree of distortion of the CuX tetrahedron (X = Cl, Br) is almost identical in compounds I and
4
4
II, which is consistent with the conclusion about the determining effect of the outer-sphere organic cation type on it [11].
Thus, the parameters of intramolecular hydrogen bonds in compounds I and II almost coincide, while the character
of the intermolecular interaction is different. Hydrogen bonds involving bromine are weaker that those in the case of a better
acceptor of the hydrogen bond such as chlorine. An important feature of the supramolecular packing of I is the absence of the
π–π stacking interaction.
REFERENCES
1. J. W. Steed and J. L. Atwood, Supramolecular Chemistry, J. Wiley, Chichester (2000).
2. P. Kavuru, D. Aboarayes, K. K. Arora, et al., Cryst. Growth Des., 10, No. 8, 3568-3584 (2010).
3. L. A. Mitsher, Chem. Rev., 105, No. 2, 559-585 (2005).
4. Cambridge Structural Database, Version 5.29, University of Cambridge. UK (2007).
5. A. D. Vasiliev, N. N. Golovnev, M. S. Molokeev, et al., J. Struct. Chem., 46, No. 2, 363-370 (2005).
6. N. N. Golovnev, A. I. Petrov, N. V. Dorokhova, et al., Zh. Sibir. Fed. Univ., Ser. Khim., 3, No. 1, 58-63 (2010).
7. G. M. Sheldrick, SADABS, Version 2.01, Bruker AXS Inc. Madison, Wisconsin, USA (2004).
8. G. M. Sheldrick, SHELX-97, A Software Package for the Solutions and Refinement of X-ray Data, Univ. Göttingen,
Germany (1997).
9. G. M. Sheldrick, SHELXTL, Version 6.10, Bruker AXS Inc. Madison, Wisconsin, USA (2004).
10. PLATON-A Multipurpose Crystallographic Tool, Utrecht University, Utrecht, The Netherlands (2008).
11. O. V. Koval’chukova, S. B. Strashnova, A. I. Stash, et al., Koordinats. Khim., 35, No. 7, 505-512 (2009).
812