КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 9, с. 550-558
УДК 541.49
SYNTHESIS, CHARACTERIZATION, AND ANTIBACTERIAL ACTIVITY OF TWO ZINC(II) COMPLEXES WITH SCHIFF BASES FROM HALOGENATED SALICYLALDEHYDE AND AMANTADINE
© 2014 Q. Yang1, C. Xu1, G. C. Han1, X. C. Liu1, X. D. Jin1, *, B. X. Wang1, D. L. Liu1, and H. H. Hu2
1College of Chemistry, Liaoning University, Shenyang, 110036 P.R. China 2Liaoning Shangyu Bidding Ltd., Shenyang, 110031 P.R. China *E-mail: jinxudong@lnu.edu.cn Received January 17, 2014
By a condensation reaction of halogenated salicylaldehyde and amantadine, two new Schiff base ligands (HL1 and HL2) were synthesized, respectively. A followed mixture of the ligands and zinc(II) chloride in the
presence of NaOH in an alcoholic medium brought out two novel complexes (ZnL2) (I) and (ZnL2) (II). These two complexes were characterized by the means of melting point, elemental analysis, IR, UV-Vis, 1H NMR, molar conductance and single-crystal X-ray diffraction analysis. X-ray diffraction analysis reveals that I crystallizes in monoclinic system, P21/c space group, a = 9.7812(5), b = 25.6198(12), c = 27.7381(18) A, в = 105.881(4), F(000) = 1416, R1 = 0.0731, wR2 = 0.1147; II crystallizes in orthorhombic system, Pbca space group, a = 11.1717(10), b = 20.5888(15), c = 27.7381(18) A, F(000) = 2976, R1 = 0.1341, wR2 = 0.1410. Both in I and II, the central zinc(II) atom is four-coordinated via two nitrogen atoms and two oxygen atoms from the corresponding Schiff base ligands, forming a distorted tetrahedral geometry.
DOI: 10.7868/S0132344X14080131
INTRODUCTION
Schiff-bases are a large class of organic compounds with imino (—HC= N-) group and simple structures [1— 3]. Transition metal complexes of Schiff bases have been amongst the most widely studied coordination compounds in the past few years, since they are found to be of importance as biochemical, analytical and antimicrobial reagents [4, 5]. Zinc is a vital element in the life and an important enzyme active site [6, 7]. The Zn(II) complexes of Schiff bases are also biologically active and they exhibit enhanced activities as compared to the free Schiff bases [8]. Tricyclo [3.3.1.1(3,7)] decane-1-amine (amantadine) is an antivirotic drug that has been used to treat influenza and Parkinson disease [9—11]. Salicylaldehyde derivatives, with one or more halo-atoms in the aromatic ring, showed variety of biological activities such as antibacterial and antifungal activities [12, 13]. In view ofthese points above, in this paper, two zinc(II) complexes with Schiff bases from halogenated salicylaldehyde and amantadine, which are ¿¿s,(2-(1-adamantyliminom-ethyl)-4-chlorophenolato-N,O)-zinc(II) (I) and bis(2-(1-adamantyliminomethyl)-4-bromophenolato-N,O)-zinc(II) (II), were designed and synthesized in the presence of NaOH. Their structures were characterized by the means of IR, UV-VIS, 1H NMR, elemental analysis and molar conductance. More over, the coordination behaviors of the ligands towards zinc(II) ion were also in-
vestigated and their absolute structures were determined by a single-crystal X-ray diffraction analysis. The antibacterial activities of complexes against two bacteria Escherichia coli and Bacillus subtilis were simultaneously investigated.
EXPERIMENTAL
Materials and methods. All chemicals and solvents were of analytical grade and used as received. Elemental analysis was carried out on Perkin Elmer Flash EA 1112. Chemical shifts (8) for 1H NMR spectra were recorded at 300 MHz on a Varian Mercury-Vx300 spectrometer in CDCl3 solvent containing TMS as an internal standard. IR spectra were scanned in the range 4000 to 400 cm-1 with KBr pellets on a Nicolet NEXUS FT-IR 5700 spectrophotometer. UV-Vis spectrum was measured on a Perkin Elmer Lambda 25 spectrophotometer. Melting points were measured on a WRS-1B micro melting point apparatus which were uncorrected. The molar conductance of the complexes in DMF (1.0 x 10-3 mol L-1) at room temperature was measured on a DDS-11A con-ductormeter.
Synthesis of ligands. Two Schiff base ligands, 2- ((E) - (-adamantan-1 -ylimino)methyl) -4-chlorophe-nol (HL1) and 2-((E)-(-adamantan-1-ylimino)meth-yl)-4-bromophenol (HL2), were prepared analogously to the literatures [14-17]. The synthetic route in this work was shown below:
Amantadine hydrochloride (0.375 g, 2.0 mmol) and KOH (0.112 g, 2.0 mmol) in 50 mL anhydrous alcohol were stirred for 1 h. The produced white precipitates (KCl) were filtered out and the transparent liquid was added dropwise to aldehyde (2.0 mmol) in 30 mL anhydrous alcohol under constant stirring. The resulting solution was refluxed for ~1 h, concentrated to about 20 mL through reduced pressure distillation and then stood at room temperature. A yellow solid appeared after 2—3 days with the solvent evaporation. The solid was filtered off and washed with anhydrous alcohol three times and air-dried.
Syntheses of complexes I and II were carried out in a similar procedure with NaOH, the corresponding Schiff base ligand and zinc(II) chloride in appropriate solvents, respectively. 20 mL ethanolic NaOH (0.080 g, 2.0 mmol) was added to a solution of ligand (2.0 mmol) in 20 mL anhydrous ethanol. After the solution was stirred for ten minutes, zinc(II) chloride (0.136 g, 1.0 mmol) in 20 mL anhydrous ethanol was added and the mixture was re-fluxed for another 2 h at 60° C. Then the solution was kept at room temperature overnight and yellowish complex precipitates were filtered off and dried. The yields were 58% (I) and 61% (II).
For C34H38N2O2Cl2Zn ■ CH3OH (I)
anal. calcd., %: C, 63.51; H, 5.96; N, 4.36.
Found, %: C, 63.30; H, 6.00; N, 4.21.
For C34H38N2O2Br2Zn (II)
anal. calcd., %: C, 55.80; H, 5.23; N, 3.83. Found, %: C, 55.75; H, 5.21; N, 4.05.
The molar conductance values (A,M) are 1.95 and 2.03 S cm2 mol-1 for I and II. It was concluded from the results that complexes were non-electrolytic in nature [18].
Proposed structures of complexes are the following:
X
I: X = Cl; II: X = Br
X-ray structure determination. The crystals of complexes suitable for X-ray analysis were obtained after about one week with a solvent CH2Cl2/MeOH (1 : 1 v/v) slow evaporation. The crystallographic data collections for complexes I and II were conducted on a Bruker Smart Apex II CCD with graphite monochromated MoKa radiation (X = 0.71073 A) at 296(2) K using the «-scan technique. The data were integrated by using the SAINT program, which also did the intensities corrected for Lorentz and polarization effect [19]. An empirical absorption correction was applied using the SADABS program [20]. The structures were solved by direct methods using the program SHELXS-97 and all non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares technique using the SHELXL-97 crystallographic software package [21]. The hydrogen atoms were generated geometrically. All calculations were performed on a personal computer with the SHELXL-97 crystallographic software package. The details of the crystal parameters, data collection and refinement for I and II are summarized in Table 1. Selected bond lengths and angles with their estimated standard deviations are given in Table 2. X-ray structures of two complexes are shown in Fig. 1; they were visualized by Diamond [22].
Supplementary material for structures I and II has been deposited with the Cambridge Crystallographic Data Centre (no. 893297 (I), 893298 (II); deposit@ ccdc.cam.ac.uk or http://www. ccdc.cam. ac .uk).
RESULTS AND DISCUSSION
In IR spectra of ligands, broad and intensity absorptions at 3443 and 3463 cm-1 for HL1 and HL2 can be identified as OH stretching vibration. Free OH stretching vibration is generally observed at 3500-3600 cm-1; the
Table 1. Crystal data and structure refinement information for compounds I and II
Parameter Value
I II
Formula weight 674.98 731.85
Crystal size, mm 0.43 x 0.34 x 0.28 0.41 x 0.31 x 0.23
Crystal system Monoclinic Orthorhombic
Space group P21/c Pbca
a, A 9.7812(5) 11.1717(10)
b, A 25.6198(12) 20.5888(15)
c, A 13.5526(6) 27.7381(18)
P, deg 105.881(4) 90
V, A3 3266.6(3) 6380.1(8)
Z 4 8
Ccalcd g cm-3 1.372 1.524
F(000) 1416 2976
mm-1 0.953 3.308
9 Range, deg 2.56-28.13 2.46-25.00
Index ranges -11 < h < 8, -30 < k < 22, -11< l < 16 -13 < h < 8, -24 < k < 15, -32 < l < 21
Reflections collected/unique 12102/5746 14936/5619
Rint 0.0250 0.0625
Data/restraints/parameters 5746/0/472 5619/0/452
GOOF 1.028 1.033
R1/WR2 (I> 2ct(T))* 0.0458/0.0982 0.0585/0.1077
R1/wR2 (all data) 0.0731/0.1147 0.1341/0.1410
Absorption correction Empirical
Refinement method Full-matrix least-squares on F2
^max^mi^ e A-3 0.586 /-0.324 0.922/-0.594
* R1 = S||F0| - |Fc||/|F0|; = [^F - Fc2)2/1 w(F^)2]1'2.
observed lower value is due to intramolecular hydrogen bonding. This band is absent in I and II, illustrating deprotonation of phenolic OH group occurs prior to the coordination. A band assigned to C=N stretching vibration 1629 cm-1 in HL1 and 1626 cm-1 in HL2 moves to lower wavenumber 1612 cm-1 in I and 1611 cm-1 in II, implying a coordination of the Schiff bases through azomethine nitrogen to Zn(II) in I and II. The spectra of HL1 and HL2 displays similar strong bands exactly at 1279 cm-1, which are fairly certain to C-O stretching vibration; these bands occur in I and II at lower frequency 1162 cm-1. In the low frequency regions, the presence of absorptions at 500 and 495 cm-1 for I and II reveals that there exists Zn-O vibration, indicating that oxygen of the Schiff bases is coordinated to Zn(II).
The main UV-Vis data for two complexes are showed in Table 3. These two complexes exhibited similar pattern in the ultraviolet spectra but significant changes in the visible spectra compared to their ligands. There exist obvious absorption bands at 382 nm in the complexes, which are not found in the ligands. This change indicates that these zinc(II) chloride
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