КООРДИНАЦИОННАЯ ХИМИЯ, 2011, том 37, № 7, с. 522-526
УДК 541.49
SYNTHESIS AND CRYSTAL STRUCTURE OF A NEW SCHIFF BASE LIGAND
AND ITS COBALT(II) COMPLEX © 2011 Y. G. Li, X. W. Dong, R. Ai, X.L. Xu, and H. L. Zhu*
College of Chemical Engineering, Engineering Research Center for Clean Production of Textile Printing, Ministry of Education,
Wuhan Textile University, Wuhan 430073, P.R. China *E-mail: hlzhu@wtu.edu.cn Received September 13, 2010
The crystal structures of cobalt(II) Schiff base complex (CoIIL2 ■ H2O) and Schiff base ligand 3,5-dichloro-salicylidene-2-chlorophenylmethylamine (HL) have been determined by single-crystal X-ray analysis. The geometry around cobalt in CoIIL2 ■ H2O is distorted tetrahedral. CoIIL2 ■ H2O crystallizes in the monoclinic system, in space group C2/c, with crystallographic parameters: a = 12.9143(16), b = 8.8326(16), c = = 25.115(3) А, в = 92.791(10)°, V = 2861.4(7) A3, Z = 4, F(000) = 1420, and the final R indices (I> 2ct(I)) are Rj = 0.0440, wR2 = 0.1272. HL crystallizes in the monoclinic system, in space group P2j/c, with crystallographic parameters: a = 11.9764(15), b = 8.2331(10), c = 14.2211(17) А, в = 98.723(6)°, V= 1386.0(3) A3, Z = 4, F(000) = 640, and the final R indices (I> 2ct(I)) are R1 = 0.0397, wR2 = 0.1018.
INTRODUCTION
Among the important coordinating systems of Schiff base ligands, salen-type Schiff bases become the hot topic of contemporary research [1—4]. They may act as the bidentate N,O [5], tridentate, and polydentate N,O,O donor ligands [6—10] to form Schiffbase metal complexes with the fascinating structures and various properties. A number of salen-type Schiff base complexes have extensively been investigated in the past decades [11—14]. The use foreground ofsuch metal complexes is promising such as acting as single-molecule magnets (SMMs) [15—17], luminescent probes [18, 19], and catalysts for specific DNA [20] and RNA [21] cleavage reactions. In addition, transition metal complexes of Schiff bases as inhibitors were investigated in prostate cancer [22] and tumor cells [23].
Recently, our group reported that some salen-type Schiff base complexes possess well inhibitory activities against xanthine oxidase and excellent antibacterial activities [24, 25]. We have also reported some J-transition metal complexes (M = Cu, Co, Ni, etc.) with Schiff base ligands derived from the condensation of salicylaldehyde with various primary amines, showing potent inhibitory activities against urease [26—29]. Interestingly, mononuclear metal complexes of Schiff base ligands show stronger abilities to inhibit urease. In order to extend our earlier work, we reported here the synthesis and crystal structure of Schiff base compound, 3,5-dichlorosali-cylidene-2-chlorophenylmethylamine (HL), and its co-balt(II) compound (CoIIL2 ■ H2O) (I).
Aldrich and used without further purication. Elemental analyses for C, H, and N were carried out on a PerkinElmer 2400 analyzer. X-ray crystallography was carried out using a Bruker Smart Apex II CCD diffractometer.
Synthesis of HL. 3,5-Dichlorosalicylaldehyde (191 mg, 1 mmol) and 2-chlorobenzylamine (141 mg, 1 mmol) were dissolved in methanol (10 ml). The mixture was stirred at room temperature for 2 h to give a clear orange solution of HL. After allowing the solution to stand in air for 8 days, yellow block-shaped crystals were formed on slow evaporation of the solvent. The yield is about 89%.
For C14H10NO Cl3
anal. calcd., %: C, 53.45; H, 3.20; N, 4.45. Found, %: C, 53.00; H, 3.50; N, 4.48.
Synthesis of compound I. Schiff base ligand HL (63 mg, 0.2 mmol) was dissolved in methanol (5 ml). The mixture was stirred for 30 min to give a brown solution, which was added to a stirred methanolic solution of CoCl2 • 6H2O (24 mg, 0.1 mmol, 2 ml). The mixture was stirred for another 10 min at room temperature and then filtered. The filtrate was kept in air for 7 days, forming brown block-shaped crystals of cobalt(II) Schiff base compound, CoIIL2 • H2O. The crystals were isolated, washed three times with distilled water, and dried in vacuum desiccator containing anhydrous CaCl2. The yield is 67%.
EXPERIMENTAL
Materials and measurements. 3,5-Dichlorosalicylal-dehyde and 2-chlorobenzylamine were purchased from
For C2SH2oN2O3Cl6Co (I)
anal. calcd., %: C, 47.76; H, 2.86; N, 3.98. Found, %: C, 47.71; H, 2.55; N, 3.81.
Table 1. Crystallographic data and experimental details for complexes HL and I
Parameter Value
HL I
Molecular weight 314.58 704.09
Crystal system Monoclinic Monoclinic
Space group P2i/c C2/c
a, Â 11.9764(15) 12.9143(16)
b, Â 8.2331(10) 8.8326(16)
c, Â 14.2211(17) 25.115(3)
P, deg 98.723(6) 92.791(10)
V, Â3 1386.0(3) 2861.4(7)
Z 4 4
Pcalcd g cm-3 1.508 1.634
/(000) 640 1420
^(MoJa), mm-1 0.650 1.195
Crystal size, mm 0.42 x 0.22 x 0.21 0.35 x 0.20 x 0.12
9 Range for data collection 1.72-26.00 1.62-24.98
Index range h, k, l -14/10, -10/9, -17/17 -15/9, -10/10, -29/27
Type of scan Multiscan Multiscan
Data/restraint/parameters 2717/0/174 2523/0/182
Rint 0.0261 0.0405
Goodness-of-fit on F2 1.007 1.057
Final R1, wR2 (I>2ct(I)) 0.0397, 0.1018 0.0440, 0.1272
Apmax and Apmim « Â"3 0.294, -0.290 0.551, -0.550
X-ray structure determinations [30]. X-ray crystallographic data were collected on a Bruker Smart Apex II CCD diffractometer using graphite-monochromated Mo^a (k = 0.71073 A) radiation. The collected data were reduced using the SAINT program, and empirical absorption corrections were performed using the SADABS program. The structures were solved by direct methods and refined against F2 by full-matrix least-squares methods using the SHELXTL version 5.1. All of the non-hydrogen atoms were refined anisotropically. All other hydrogen atoms were placed in geometrically ideal positions and constrained to ride on their parent atoms. The crystallographic data for compounds HL and I are summarized in Table 1. Selected bond lengths and angles are given in Table 2.
The atomic coordinates and other parameters of structure have been deposited with the Cambridge Crystallographic Data Centre (nos. 756159 (HL) and 756160 (I); deposit@ccdc.cam.ac.uk or http://www. ccdc.cam. ac.uk).
RESULTS AND DISCUSSION
In this paper, Schiff base ligand HL was prepared by the reaction of 3,5-dichlorosalicylaldehyde with 2-chlo-robenzylamine in 93% yield in an absolute MeOH solution. HL is a yellow crystallite stable in air at room temperature. It is easily soluble in common polar organic solvents, such as DMSO, DMF, MeOH, EtOH, MeCN, Me2CO, etc., but is poorly soluble in water and Me2O. Cobalt(II) compound CoIIL2 • H2O (I) was obtained
Table 2. Selected bond lengths and angles for structures HL and I*
Bond d, A Bond d, A
HL
Cl(1)-C(3) 1.727(2) N(1)-C(8) 1.463(3)
Cl(2)-C(5) 1.731(2) O(1)-C(2) 1.341(2)
Cl(3)-C(10) 1.738(2) C(1)-C(7) 1.457(3)
N(1)-C(7) 1.269(3) C(8)-C(9) 1.508(3)
CoIIL2
Co(1)-O(1) 1.919(2) N(1)-C(7) 1.285(4)
Co(1)-N(1) 1.990(3) N(1)-C(8) 1.489(4)
Cl(1)-C(3) 1.728(3) O(1)-C(2) 1.305(3)
Cl(2)-C(1) 1.742(3) C(1)-C(7) 1.447(4)
Cl(3)-C(10) 1.731(4) C(8)-C(9) 1.493(5)
Angle ro, deg Angle ro, deg
HL
C(7)N(1)C(8) 118.6(2) N(1)C(7)C(1) 121.4(2)
C(7)C(1)C(2) 120.75(19) N(1)C(8)C(9) 109.78(17)
CoIIL2
O(1)aCo(1)O(1) 104.98(13) C(7)N(1)C(8) 116.1(3)
O(1)Co(1)N(1) 94.94(10) C(7)N(1)Co(1) 122.2(2)
O(1)Co(1)N(1)a 124.24(10) C(8)N(1)Co(1) 121.6(2)
N(1)Co(1)N(1)a 115.60(16) C(2)O(1)Co(1) 124.52(19)
* Symmetry codes: a 2 — x, y, 3/2 — z.
from the reaction of HL with CoCl2 ■ 6H2O in MeOH. The elemental analysis is in good agreement with the chemical formula proposed for compounds HL and I.
The crystal structure of HL is shown in Fig. 1a. All bond lengths are within normal ranges [31]. The torsion angle C(7)—N(1)—C(8)—C(9) is -113.1(2)°. The dihedral angle between the phenyl rings C(1)C(2)C(3)C(4)C(5)C(6) and C(9)C(10)C(11)C(12)C(13)C(14) is 73.3(2)°. The C(7)=N(1) bond length of1.269(3) A is slightly longer than the corresponding value of 1.264(3) A observed in a similar Schiff base compound, 5-chlorosalicylidene-4-fluo-rophenylmethylamine [32]. An intramolecular
O(1)-H(1)-N(1) (O-N 2.592(2) A) hydrogen bond is formed between atoms O(1) and N(1) (Fig. 1a). In the crystal packing, the molecules are linked by the weak intermolecular Cl-Cl (3.318(2) A) interactions as shown in Fig. 2a.
In contrast, the crystal structure of cobalt(II) Schiff base complex consists of the mononuclear CoIIL2 units and the lattice water molecules. As shown in Fig. 1b, the Co(II) atom, lying on an inversion center (symmetry codes: 2 - x, y, 3/2 - z), has a distorted tetrahedral coordination by two N atom and two O atoms from two Schiff base ligands (L). The dihedral angle between the two
KOOP^HH^HOHHAtf XHMH3 TOM 37 № 7 2011
Cl(2) C(5)
C(4)
(a)
(a)
C(13)
C(12) C(11)
Fig. 1. ORTEP diagrams showing the molecular structure of HL (a) and CoIIL2 (b). Thermal ellipsoids are shown at the 30% probability level and some H atoms are omitted for clarity.
O(1)—Co(1)—N(1) planes of the molecule is equal to 78.12°. Dihedral angles of 0° and 90° would be expected for planar and pseudotetrahedral geometries, respectively [33]. The present geometry strongly reduces the steric hindrance and, therefore, the conformation of the L entities is close to that of the free ligand. The bond distances of Co(1)—O and Co(1)—N (1.919(2) and 1.990(3) Á) are slightly longer that the corresponding values of 1.859(5) and 1.983(6) Á, respectively, observed in analogous tetra-hedral Co(II) species reported in the literature [34]. The angles subtended at the cobalt(II) ion of the distorted tetrahedral geometry (CoN2O2) is in the range 94.94(10)°—124.24(10)°. In the crystal packing, two Schiff base ligands L of CoIIL2 were linked by intermolecular O(2)-H(LS)-O(1) (O-O 2.954(5) Á) and O(2)-H(1Q-O(L4) (O-O 2.954(5) Á) hydrogen bonds. The mononuclear CoIIL2 units are furthe
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