Synthesis, characterization, and crystal structure of three cobalt(II) complexes with Schiff bases derived from rimantadine

Article abstract of DOI:10.1080/00958972.2014.885509

By condensation of rimantadine and substituted salicylaldehyde, three new Schiff bases, HL¹, HL² and HL³, were synthesized. Then, a mixture of one of the new ligands and cobalt(II) chloride hexahydrate in ethanol led to 1, 2, and 3, respectively. These complexes were characterized by melting point, elemental analysis, infrared spectra, molar conductance, thermal analysis, and single-crystal X-ray diffraction analysis. X-ray diffraction analysis reveals that 1 crystallizes in the orthorhombic system, Pbcn space group; each asymmetric unit consists of one cobalt(II) ion, two deprotonated ligands, and one lattice water. The central cobalt is four coordinate via two nitrogens and two oxygens from the corresponding Schiff base ligand, forming a distorted tetrahedral geometry. Complexes 2 and 3 crystallize in the monoclinic system, P₂₁/c space group; each asymmetric unit consists of one cobalt(II), two corresponding deprotonated ligands, one lattice water, and one methanol. The central cobalt is also four-coordinate via two nitrogens and two oxygens from the corresponding Schiff base ligand, forming a distorted tetrahedral geometry. 2014

Full text of DOI:10.1080/00958972.2014.885509

Journal of Coordination Chemistry, 2014
Vol. 67, No. 2, 352–362, http://dx.doi.org/10.1080/00958972.2014.885509
Synthesis, characterization, and crystal structure of three
cobalt(II) complexes with Schiff bases derived from
rimantadine
CHONG XU†, XIAO-CHEN LIU†, XU-DONG JIN*†, QI YANG†,
GUANG-CHAO HAN†, YU-CHEN GANG‡ and HAI-HONG HU§
†College of Chemistry, Liaoning University, Shenyang, PR China
‡College of Agriculture and Biotechnology, China Agricultural University, Beijing, PR China
§Liaoning Shangyu Bidding Ltd, Shenyang, PR China
(Received 4 November 2013; accepted 30 December 2013)
By condensation of rimantadine and substituted salicylaldehyde, three new Schiff bases, HL1, HL2
and HL3, were synthesized. Then, a mixture of one of the new ligands and cobalt(II) chloride hexa-
hydrate in ethanol led to 1, 2, and 3, respectively. These complexes were characterized by melting
point, elemental analysis, infrared spectra, molar conductance, thermal analysis, and single-crystal
X-ray diffraction analysis. X-ray diffraction analysis reveals that 1 crystallizes in the orthorhombic
system, Pbcn space group; each asymmetric unit consists of one cobalt(II) ion, two deprotonated
ligands, and one lattice water. The central cobalt is four coordinate via two nitrogens and two
oxygens from the corresponding Schiff base ligand, forming a distorted tetrahedral geometry.
Complexes 2 and 3 crystallize in the monoclinic system, P21/c space group; each asymmetric unit
consists of one cobalt(II), two corresponding deprotonated ligands, one lattice water, and one
methanol. The central cobalt is also four-coordinate via two nitrogens and two oxygens from the
corresponding Schiff base ligand, forming a distorted tetrahedral geometry.
Keywords: Cobalt(II) complexes; Rimantadine; Schiff bases; Synthesis; Crystal structures
1. Introduction
Metal Schiff base complexes have been studied as reagents for oxygen separation and trans-
port [1], as models for biological dioxygen carriers [2], metalloenzymes [3], or used in cata-
lytic reactions [4]. In particular, Schiff bases and complexes containing sulfur and nitrogen
*Corresponding author. Email: hgxy@lnu.edu.cn
© 2014 Taylor & Francis

Cobalt(II) complexes with rimantadine
353
donors have demonstrated significant antifungal [5], antibacterial, anticancer, and catalytic
activities [6–11]. Cobalt is a vital element in organisms with important enzyme active sites;
it can stimulate the hematopoietic system, prompting the synthesis of hemoglobin and red
blood cells [12–15]. In many countries, amantadine (SymmetrelTM) and rimantadine
(FlumadineTM) have been widely used to treat or prevent seasonal influenza as efficacious
remedies [16–19]. However, the incidence of side effects to the central nervous system was
higher with amantadine [20]. Salicylaldehyde and its derivatives, especially with one or
more halogens in the aromatic ring, have antibacterial and antiviral activity and were used
to produce efficient herbicides, insecticides and fungicides [21–23]. As an extension of our
previous work on zinc(II) complexes with a Schiff base derived from amantadine, we
designed and synthesized three cobalt(II) complexes with three different Schiff bases
derived from rimantadine and three substituted salicylaldehydes (o-vanillin-salicylaldehyde,
5-chloro-salicylaldehyde, and 5-bromo-salicylaldehyde). The coordination behaviors of the
ligands towards cobalt(II) were investigated and their absolute structures were determined
by single-crystal X-ray diffraction analyses.
2. Experimental
2.1. Materials and methods
All chemicals and solvents were analytical grade and used as received. Elementa1 analyses
for ligands and complexes were carried out on a Perkin Elmer Flash EA 1112. Infrared
spectra (IR) were scanned from 4000 to 400 cm−1 with KBr pellets on a Nicolet NEXUS
FT-IR 5700 spectrophotometer. Thermal analyses were carried out on a METTLER
TOLEDO TGA/SDTA851e. Melting points were measured on a WRS-1B micro-melting
point apparatus and are not corrected. The molar conductance of the complexes in DMF
(1.0 × 10−3 M L−1) was measured on a DDS-11A conductometer.
2.2. Synthesis of the ligands
Three ligands (figure 1) were prepared by an improved method based on the literature [24].
Rimantadine hydrochloride (432 mg, 2.0 mM) and KOH (112 mg, 2.0 mM) in 50 mL
anhydrous ethanol were stirred for 1 h. White precipitate (KCl) was filtered out and the
transparent liquid was added dropwise to a solution of substituted salicylaldehyde (2.0 mM)
in 20 mL anhydrous ethanol. The resulting solution was refluxed for 1 h at 60 °C and cooled
to room temperature; a yellow Schiff base precipitate was obtained after one week under
slow solvent evaporation.
HL1: 420 mg, yield 67%. Yellowish powder. m.p. 98.5–99.6 °C. IR (KBr): 3442(w),
2993(w), 2930(s), 2848(m), 1633(s), 1589(w), 1466(s), 1420(m), 1383(w), 1360(w), 1348
(w), 1330(w), 1312(w), 1273(m), 1246(s), 1189(w), 1171(w), 1154(w), 1117(w), 1084(w),
1026(w), 973(m), 934(w) 920(w), 876(w), 827(m), 779(w), 737(s), 705(w), 634(w), 557
(w), 520(w). Anal. Calcd for C20H27NO2 (313.43):C, 76.64; H, 8.68; N, 4.47. Found: C,
76.12; H, 8.59; N, 4.57.
HL2: 445 mg, yield 70%. Yellow powder. m.p. 74.9–75.5 °C. IR (KBr): 3433(m), 2905
(s), 2849(m), 1632(m), 1578(w), 1481(m), 1450(w), 1380(w), 1346(w), 1317(w), 1279(w),
1193(w), 1151(w), 1094(w), 973(w), 823(m), 787(w), 721(w), 686(w), 647(w), 625(w),

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C. Xu et al.
Figure 1. The formation of the Schiff bases.
569(w), 551(w), 530(w), 511(w), 492(w), 471(w), 450(w). Anal. Calcd for C19H24ClNO
(317.85):C, 71.80; H, 7.61; N, 4.41. Found: C, 71.64; H, 7.65; N, 4.43.
HL3: 565 mg, yield 78%. Yellowish powder. m.p. 102.9–103.4 °C. IR (KBr): 3441(m),
2973(m), 2908(s), 2849(m), 1630(m), 1571(m), 1477(m), 1377(m), 1279(m), 1191(w),
1086(w), 976(w), 921(w), 821(m), 681(w), 624(m). Anal. Calcd for C19H24BrNO (362.30):
C, 62.99; H, 6.68; N, 3.87. Found: C, 62.95; H, 6.65; N, 4.90.
2.3. Synthesis of the complexes
Complexes 1–3 were prepared in a similar procedure starting from their corresponding
Schiff base, NaOH, and cobalt(II) chloride hexahydrate in anhydrous methanol (figure 2).
To a solution of ligand (2.0 mM) in anhydrous methanol (20 mL) was added a solution of
NaOH (80 mg, 2.0 mM) in anhydrous methanol (20 mL) followed by addition of cobalt(II)
chloride hexahydrate (238 mg, 1.0 mM) in anhydrous methanol (20 mL). The mixture was
refluxed for 2 h and then concentrated until a large amount of precipitate was observed. The
red solid was suction filtered, washed with cold water, and dried to afford a complex.
Complex 1: 424 mg, yield 62%. Bright red powder. m.p. 244.3–246.1 °C. IR (KBr):
3465(m), 3053(w), 2972(w), 2901(s), 2845(m), 1655(w), 1603(s), 1547(m), 1465(s), 1448
(s), 1420(m), 1381(w), 1341(m), 1243(s), 1215(s), 1169(w), 1153(w), 1083(m), 1003(w),
982(w), 856(w), 742(m), 635(w), 586(w). Anal. Calcd for C40H52CoN2O4 (683.79):C,
70.20; H, 7.60; N, 4.09. Found: C, 70.26; H, 7.67; N, 4.10.
Complex 2: 402 mg, yield 58%. Bright red powder. m.p. 258.3–260.7 °C. IR (KBr):
3438(m), 2899(s), 2847(m), 1600(s), 1520(m), 1453(s), 1391(s), 1314(m), 1169(m), 1083
(m), 979(w), 870(w), 815(w), 708(m), 657(w), 498(m), 456(m). Anal. Calcd for
C38H46Cl2CoN2O2 (692.60):C, 65.90; H, 6.64; N, 4.04. Found: C, 65.85; H, 6.65; N, 4.00.
Complex 3: 508 mg, yield 65%. Bright red powder. m.p. 264.3–265.6 °C. IR (KBr): 3428
(m), 2902(s), 2847(m), 1599(s), 1518(m), 1455(s), 1391(s), 1310(m), 1170(m), 1133(w),
Figure 2. Proposed structures of 1–3.

Cobalt(II) complexes with rimantadine
355
1080(w), 975(w), 871(w), 824(w), 799(w), 684(m), 648(m), 496(m), 460(m). Anal. Calcd for
C38H46Br2CoN2O2 (781.52):C, 58.35; H, 5.89; N, 3.58. Found: C, 58.40; H, 5.87; N, 3.55.
2.4. X-ray crystallography
Crystals of the complexes suitable for X-ray analysis developed from a solution of CH3OH/
CH2Cl2/H2O (4 : 4 : 1 v/v/v) through slow evaporation. The crystallographic data collections
were conducted on a Bruker Smart Apex II CCD with graphite-monochromated Mo-Kα
radiation (λ = 0.71073 Å) at 298(2) K using the ω-scan technique. The data were integrated
using SAINT, which also corrected the intensities for Lorentz and polarization effects [25].
An empirical absorption correction was applied using SADABS [26]. The structures were
solved by direct methods using SHELXS-97 and all non-hydrogen atoms were refined
anisotropically on F2 by full-matrix least-squares using the SHELXL-97 crystallographic
software package [27]. Hydrogens were generated geometrically. All calculations were
performed on a personal computer with the SHELXL-97 crystallographic software package.
The crystal parameters, data collection, and refinement are summarized in table 1. Selected
bond lengths and angles with their estimated standard deviations are given in table 2.
Table 1. Crystallographic data for 1–3.
Empirical formula C40H52CoN2O4·H2O C38H46Cl2CoN2O2·H2O·CH3OH C38H46Br2CoN2O2·H2O·CH3OH
(1)
(2)
(3)
Formula weight
(g M−1
701.78
742.60
831.52
)
Crystal size (mm)
Crystal system
Color
Space group
a (Å)
b (Å)
c (Å)
α (°)
0.33 × 0.27 × 0.19
Orthorhombic
Bright red
Pbcn
10.9176(18)
13.088(2)
25.228(4)
90.00
0.40 × 0.30 × 0.20
Monoclinic
Bright red
P21/c
9.2609(3)
19.2802(5)
21.3356(6)
90
0.30 × 0.20 × 0.10
Monoclinic
Bright red
P21/c
9.3452(6)
19.3896(14)
21.2518(17)
90.00
β (°)
90.00
90.00
3604.8(10)
4
98.987(3)
90
3762.75(19)
4
99.125(6)
90.00
3802.1(5)
4
γ (°)
V (Å3)
Z
θ Range (°)
Index ranges
1.26–28
2.35–24.2
−11 ≤ h ≤ 9,
−22 ≤ k ≤ 22,
−25 ≤ l ≤ 25
1.223
2.56–26.47
−11 ≤ h ≤ 11,
−23 ≤ k ≤ 14,
−25 ≤ l ≤ 23
1.365
−14 ≤ h ≤ 12,
−16 ≤ k ≤ 14,
−30 ≤ l ≤ 32
1.293
ρ (g cm−3
μ (mm−1
)
)
0.522
0.631
2.586
Reflections
collected/
unique
12792/4113
[R(int) = 0.0575]
14275/6600
[R(int) = 0.0252]
14904/6680
[R(int) = 0.0521]
Data/restraints/
parameters
Goodness-of-fit
(GoF)
4133/186/339
1.001
6600/0/408
1.058
6680/0/406
0.924
F (0 0 0)
T/K
1500
298(2)
1460
298(2)
0.0413/0.1002
0.0589/0.1081
1604
298(2)
0.0551/0.1011
0.1183/0.1205
R1a/wR2b(I > 2σ(I)) 0.0540/0.1254
R1/wR2 (all data)
0.1233/0.1563
aR1 = Σ||Fo| – |Fc||/|Fo|.
bwR2 = [Σw(Fo2 – Fc2)2/Σw(Fo2)2]1/2
.

356
C. Xu et al.
Hydrogen bond geometry of 1 is listed in table 3. The molecular structures of 1–3 are
shown in figures 3–5, as visualized by Diamond [28].
3. Results and discussion
3.1. Elemental analysis and molar conductance
From the analysis, the C, H, and N contents suggest that 1–3 consist of one cobalt(II) and
two deprotonated ligands. Although all compounds are soluble in dichloromethane and
Table 2. Selected bond lengths (Å) and angles (°) in 1–3.
1
Co1–O1
1.910(2)
1.910(2)
Co1–N1
1.856(9)
1.856(9)
Co1–O1i
Co1–N1i
N1–C8
O1–C1
1.457(9)
1.305(4)
N1–C9
O2–C7
1.547(13)
1.427(4)
O1–Co1–O1i
O1i–Co1–N1
O1i –Co1–N1i
O1–C1–C6
N1–C8–C2
C8–N1–C9
C1–O1–Co1
2
98.68(12)
122.45(4)
99.80(4)
118.99(3)
125.71(6)
93.97(6)
O1–Co1–N1
O1–Co1–N1i
N1–Co1–N1i
O1–C1–C2
N1–C9–C10
C8–N1–Co1
C9–N1–Co1
99.80(2)
122.45(4)
114.30(8)
124.13(3)
109.71(10)
119.22(14)
146.36(6)
125.79(19)
Co1–O1
Co1–O2
N1–C7
1.907(17)
1.915(16)
1.280(3)
Co1–N1
Co1–N2
N1–C8
2.016(18)
2.019(19)
1.489(3)
N2–C26
1.287(3)
N2–C28
1.497(3)
O1–C1
1.309(3)
O2–C20
1.312(3)
O1–Co1–O2
O1–Co1–N1
O1–Co1–N2
O1–C1–C6
O2–C20–C25
N1–C7–C6
N1–C8–C9
N2–C27–C28
C1–O1–Co1
C7–N1–Co1
C26–N2–Co1
3
108.25(7)
94.16(7)
120.30(7)
123.6(2)
123.8(2)
128.1(2)
108.67(19)
108.2(6)
124.1(5)
119.23(15)
119.49(15)
O2–Co1–N2
O2–Co1–N1
N2–Co1–N1
O1–C1–C2
O2–C20–C21
N1–C8–C10
N2–C28–C29
N2–C28–C30
C20–O2–Co1
C8–N1–Co1
C28–N2–Co1
95.28(7)
117.79(7)
122.03(8)
119.16(7)
118.9(2)
111.50(18)
108.73(9)
112.21(18)
125.02(15)
123.97(15)
124.43(15)
Co1–O1
Co1–O2
N1–C7
N2–C26
1.915(3)
1.912(3)
1.304(6)
1.281(5)
1.320(5)
107.27(15)
95.63(15)
120.62(15)
118.7(4)
123.9(4)
128.0(5)
113.3(4)
127.5(5)
125.0(3)
119.5(3)
119.1(3)
Co1–N1
Co1–N2
N1–C8
N2–C27
2.005(4)
2.006 (4)
1.489(6)
1.480(6)
1.302(5)
117.16 (15)
94.42(15)
122.43(16)
123.5(5)
119. 1(5)
107.4(4)
112.0(4)
108.7(4)
124.5(3)
125.6(3)
124.6(3)
O1–C1
O2–C20
O1–Co1–O2
O1–Co1–N1
O2–Co1–N1
O1–C1–C2
O2–C20–C25
N1–C7–C6
N1–C8–C10
N2–C26–C25
C1–O1–Co1
C7–N1–Co1
C26–N2–Co1
O1–Co1–N2
O2–Co1–N2
N2–Co1–N1
O1–C1–C6
O2–C20–C21
N1–C8–C9
N2–C27–C29
N2–C27–C28
C20–O2–Co1
C8–N1–Co1
C27–N2–Co1
Symmetry code: (i) −x + 1, y, −z + 1/2.

Cobalt(II) complexes with rimantadine
Table 3. Hydrogen bond geometry (Å, °) in 1.
357
D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A
O1w–H1w⋯O1
O1w–H2w⋯O1i
0.851
0.849
2.302
2.231
2.892
2.892
126.73
134.67
Symmetry code: (i) −x + 1, y, −z + 1/2.
Figure 3. Molecular structure of 1. Hydrogens are omitted for clarity.
chloroform, the complexes are less soluble than the ligands in other solvents such as etha-
nol, THF, benzene, and ethyl acetate. The molar conductance values (ΛM) for 1–3 are 2.26,
2.08, and 2.56 S cm2 M−1, indicating non-electrolytes [29].
3.2. IR spectra
The main IR data for 1–3 are presented in table 4, with data for ligands provided for com-
parison. IR spectra of ligands show bands at 3442, 3443, and 3441 cm−1 attributed to OH
stretch. Free OH stretching vibrations are generally at 3500–3600 cm−1; the observed lower
value is due to intramolecular hydrogen bonding. These bands are absent in complexes,
indicating deprotonated phenolic OH. Bands at 1633, 1632, and 1629 cm−1 in ligands are
assigned to C=N stretches, shifted to lower wave number (1603, 1600, and 1599 cm−1) in
1–3, implying coordination of azomethine nitrogen to Co(II). The spectra of ligands display
strong bands at 1246–1279 cm−1, which are C–O stretches; these bands occur in complexes
at 1169–1243 cm−1. In the low frequency region, absorptions at 456–586 cm−1 for com-
plexes reveals Co–O vibration, indicating that oxygen of the Schiff base is coordinated to
Co(II).

358
C. Xu et al.
Figure 4. Molecular structure of 2. Hydrogens are omitted for clarity.
3.3. Crystal structures of complexes
The crystallographic analysis reveals that 1 crystallizes in the orthorhombic system, Pbcn
space group; each asymmetric unit comprises one cobalt(II) complex and one lattice water.
Complexes 2 and 3 crystallize in the monoclinic system, P21/c space group; each asymmet-
ric unit comprises one cobalt(II) complex, one lattice water, and one lattice methanol. The
central cobalt(II) in 1–3 lies on a twofold rotation axis and is bonded to oxygen and
nitrogen donors of the two bidentate ligands in a trans-arrangement. In general, the coordi-
nation of these cobalt(II) complexes is close to a zinc(II) complex we reported [30]. The
geometry around cobalt(II) in 1–3 is intermediate between square planar and tetrahedral,
where the dihedral angle between the two coordination planes defined by O1–Co1–N1 and
O1i–Co1–N1i is 76.55° for 1, by O1–Co1–N1 and O2–Co1–N2 is 86.01° for 2, and by
O1–Co1–N1 and O2–Co1–N2 is 85.76° for 3 [31]. The two phenyl rings are in intersecting
planes with a dihedral angle of 83.07° for 1, 85.11° for 2, and 83.90° for 3. Bond
angles also show that the coordination geometry of cobalt in 1 is distorted tetrahedral (τ4 =
[360 − (α + β)]/141° = 0.82) [32], with N1–Co1–O1i (α) and O1–Co1–N1i (β) angles of
122.45(4)° and 122.45(4)°, respectively. Complex 2 is a distorted tetrahedral (τ4 = [360 −
(α + β)]/141° = 0.83), with N1–Co1–N2 (α) and O1–Co1–N2 (β) angles of 122.03(8)° and
120.30(7)°, respectively. Complex 3 is also a distorted tetrahedral (τ4 = [360 − (α + β)]/
141° = 0.83), with N1–Co1–N2 (α) and O2–Co1–N1 (β) angles of 122.43(16)° and 120.62
(15)°, respectively. The τ4 parameters for these complexes are close to 1.00 and the dis-
tances between two adamantane cages from two ligands in 1–3 are relatively far, which

Cobalt(II) complexes with rimantadine
359
Figure 5. Molecular structure of 3. Hydrogens are omitted for clarity.
Table 4. Main IR data for ligands and complexes (cm−1).
Compound
υC=N
υC–O
tCH2
υO–H
υM–O
HL1
1
1633(s)
1603(s)
1632(m)
1600(s)
1629(m)
1599(s)
1246(s)
1243(s)
1279(w)
1169(m)
1279(m)
1170(m)
2848(s)
2845(m)
2849(m)
2847(m)
2849(m)
2902(s)
3442(w)
–
–
586(w)
–
456(m)
HL2
2
3433(m)
–
3441(m)
–
HL3
3
460(m)
Notes: s – strong; m – medium; and w – weak.
suggests a trans-coordination of two ligands to cobalt, expected for a typical Schiff base
ligand (containing a short C=N bond distance of 1.297 Å for 1, 1.287 Å for 2, and 1.304
Å for 3) coordinated to a metal center, where the imine form is predominant. The dis-
tinctly shortened Co1–O1 and Co1–N1 bonds in 1 are 1.910 and 1.857 Å, respectively
(the normal bond lengths are 1.940 and 1.960 Å), so the coordination geometry around
the Co(II) ion reflects the Jahn–Teller effect [33]. The distinctly shortened Co1–O1 and
slightly elongated Co1–N1 bonds in 2 and 3 are 1.907 Å/1.915 Å and 2.015 Å/2.005 Å,
respectively, which also reflects the Jahn–Teller effect. The distances of two neighboring

360
C. Xu et al.
cobalt along the b-axis are 8.522 Å in 1, 10.636 Å in 2, and 13.080 Å in 3. The bidentate
coordination inhibits forming intramolecular hydrogen bonds because of the deprotonated
ligands, but there also exist two six-membered rings through a cobalt ion, two oxygens,
and two nitrogens in 1–3 [34]. The organic molecules alternate with crystallization water
molecules forming O–H⋯O intermolecular hydrogen bonds between water and two phenol
oxygens from two ligands in 1 (figure 6). The distances between two O are 2.892 Å and
the hydrogen bond angles O–H⋯O are 126.73° and 134.67° (see table 3). The same num-
ber and configuration of lattice water and methanol were found in crystals of 2 and 3,
which occupied the interspaces of the organic molecules, implying that 2 has the similar
spatial arrangement as 3 (figures 7 and 8).
Specifically, in complex 1, C9 and C9A are chiral centers, however, the centrosymmetric
crystal represents a racemate, with the other stereoisomer being within the lattice. The
situations of C8 and C27 for 2 and 3 are similar.
3.4. Thermal analyses of 1–3
Thermal stability and the mechanism of decomposition for 1–3 were investigated by TG–
DTG measurements and with a heating rate of 20 °C min−1 under N2 from 25 to 900 °C.
The TG–DTG curves are provided in Supplementary material (see online supplemental
material at http://dx.doi.org/10.1080/00958972.2014.885509). The thermal decompositions
were observed with three stages for 1–3. The starting decomposition and weight losses for
1–3 were approximately 100 °C corresponding to loss of one lattice water for 1, and one
lattice water and one lattice methanol for 2 and 3, indicating that solvents were not coordi-
nated. The second rapid weight loss stages took place at 330 °C and the third degradation
stages occurred at 400 °C. When the complexes were heated above 700 °C for 1 and 900 °C
for 2 and 3, the residues were deduced as oxides.
Figure 6. The packing diagram of 1 viewed along the a-axis.

Cobalt(II) complexes with rimantadine
361
Figure 7. The packing diagram of 2 viewed along the a-axis.
Figure 8. The packing diagram of 3 viewed along the a-axis.
4. Conclusion
Three Schiff base ligands and their corresponding cobalt(II) complexes have been prepared
and characterized by melting point, elemental analysis, IR, molar conductance, thermal anal-
ysis, and single-crystal X-ray diffraction analysis. Their single-crystal structures reveal that in
1–3 each Schiff base serves as a bidentate ligand coordinating through an oxygen and nitro-
gen. The geometry around cobalt is intermediate between square planar and tetrahedral.
Supplementary material
Supplementary X-ray crystallographic data for 1 (CCDC 893305), 2 (CCDC 969173), and
3 (CCDC 969172) can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retriev-
ing.html (or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge
CB2 1EZ, UK; Fax: (+44) 1223-336-033 or E-mail: deposit@ccdc.cam.ac.uk).

362
C. Xu et al.
Funding
This work was financially supported by Foundation of Liaoning Provincial Department of Education
Innovation Team Projects [grant number LT2012001]; the Cause of Public Welfare Scientific Research
Fund [grant number 2012004001]; Shenyang Science and Technology Plan Project [grant number
130496]; Liaoning University Foundation of 211 Project for Innovative Talents Training, and the
Technology Major Projects Research Foundation [grant number 2011ZX09102–007-02], China.
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