We synthesized a new compound C17H22FN3O32ꢁ CuCl42ꢀ (pefloxacindium tetrachlorocuprate (II)), C17H20FN3O3 is
1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-methyl-1-piperazinyl)-3-quinoline carboxylic acid (PefH, pefloxacin) and
determined its crystal structure.
Experimental. PefH, used in the synthesis, in the form of a white powder was isolated in air from the solution
obtained by dissolving PefH
CH3SO3H
2H2O pefloxacin methanesulfonate dihydrate (Nakoda Chemicals Ltd., India) in
excess of 0.1 M ammonia solution.
Synthesis of C17H22FN3O32+
CuCl42ꢀ
.
In 4 ml of 6 M hydrochloric acid 0.30 g of pefloxacin was dissolved. Then
an equimolar amount of CuCl
were isolated in the form of thin needles on slow cooling or evaporating of the solution.
The selected crimson crystal with linear dimensions of 0.12 mm 0.13 mm 0.42 mm was placed into the goniometer
of an X-ray SMART APEX II (Bruker) autodiffractometer with a two-dimensional CCD-detector (MoKD radiation, graphite
monochromator). At 295 K by scanning in a range to 2 = 56 19825 reflections were measured, 5304 out of them being
independent (Rint = 0.025). Crystallographic characteristics are as follows: = 14.055(1) Å, = 12.136(1) Å, = 12.922(1) Å,
= 94.040(1) 21/ space group,
= 2198.7(3) Å3, = 4, dcalc = 1.633 g/cm3. Absorption corrections were introduced using
22H2O was gradually added to the solution under heating. Crimson crystals of the compound
u
u
Z–
M
T
q
a
b
c
E
q,
V
P
ɫ
Z
the SADABS program [7] that employs repeated measurements of the same reflections at different crystal orientations. The
structural model was solved by direct methods and refined in the anisotropic approximation of thermal vibrations of non-
hydrogen atoms using the SHELXTL program package [8]. Hydrogen atoms were located from electron density difference
syntheses. The hydrogen atoms bonded to carbon atoms were refined with reference to the corresponding atoms; coordinates
of the others were refined freely. Isotropic thermal parameters of all ɇ were 1.2 of the Ueq value of the bonded atom. Hence,
the maximum and minimum values of the difference electron density were 0.38 e/Å3 and –0.38 e/Å3,
4399 | | > 4 ) and 0.038 over all independent reflections); wR2 = 0.076; GOOF = 1.035.
CIF file containing full information on the studied structure was deposited with CCDC, No. 714683, where it is
R1 = 0.028 (against
F
V(F
Results and discussion. Fig. 1 shows the molecular structure of C17H22FN3O32ꢁ CuCl42ꢀ (molecular weight is
540.74). The lengths of C–O, C–N, C–F, and ɋ–ɋ bonds within errors coincided with those found previously for other
pefloxacin compounds: (PefH2ꢁ )PtCl24ꢀ 2H2O, (PefHꢁ2 )CH3SO3ꢀ 2H2O, (PefH2ꢁ )CH3SO3ꢀ 0.1H2O, and Ag(H2O)Pef
3H2O [9]. The corresponding bond angles were also slightly different. The crystal of the compound contains PefH32ꢁ and
CuCl24ꢀ ions. The latter ion represents a distorted tetrahedron {
}, while the PefH32ꢁ ion is a planar fragment composed of aromatic rings with side chains (non-hydrogen atoms
are out of the plane not more than by 0.068(2) Å, except ɋ12 with an outrun of 0.121(2) Å) and the piperazine ring with chair
conformation, whose parameters, in accordance with [10], are as follows: = 0.578(2) Å, = 4.5(2) = 16(2) (Fig. 1).
d
(Cu–Cl) = 2.2029(6)-2.2984(5) Å, CliCuClj = 100.93(2)-
127.94(2)
q
Q
T
q
,
M
q
The terminal N3 atom is protonated. To the carbonyl Ɉ1 atom ɇ1 hydrogen is also bonded, which forms an intramolecular
hydrogen bond with Ɉ2 of the carboxyl group: O1–H1…O2. Another intramolecular bond C14–H14A…F also closing the
six-membered ring binds F and ɋ14 atoms. The C14–H14A protons are acidic, as compared to other ɋ–ɇ protons, due to the
inductive effect of the nearest N2 atom, and therefore they form hydrogen bonds [4]. Table 1 lists the parameters of hydrogen
bonds.
In the crystal, pefloxacin molecules form pairs (Fig. 2) bound by the S–S interaction between the aromatic rings of
molecules. Table 2 presents the calculated geometric parameters of this interaction [11]. The presence of complex CuCl42ꢀ
ions in the structure results in the formation of hydrogen bonds involving chlorine atoms that form zigzag chains of
alternating pefloxacin molecules and CuCl24ꢀ ions with the [2 0 –1] axial direction. These chains are linked with each other
by the described above
178
S–S interaction so that two pefloxacin molecules successive in the chain are bonded to different