ЖУРНАЛ НЕОРГАНИЧЕСКОЕ ХИМИИ, 2011, том 56, № 9, с. 1469-1474
КООРДИНАЦИОННЫЕ СОЕДИНЕНИЯ
УДК 541.49
SYNTHESIS, SPECTROSCOPIC STUDIES AND BIOLOGICAL SCREENING OF 18-MEMBERED OCTAAZAMACROCYCLIC COMPLEXES DERIVED FROM ACETONYLACETONE AND THIOCARBOHYDRAZIDE
© 2011 г. D. P. Singh*1, Monika Kamboj*, Krishan Kumar*, Kiran Jain**, Chetan Sharma***, K. R. Aneja***
*Department of Chemistry, National Institute of Technology, Kurukshetra-136119, India **Department of Chemistry, M.L.N. College, Yamunanagar-135001, India ***Department of Microbiology, Kurukshetra university, Kurukshetra-136119, India E-mail: dpsinghchem@yahoo.co.in Поступила в редакцию 15.03.2010 г.
A series of the macrocyclic complexes is synthesized by condensation of acetonylacetone and thiocarbohy-drazide in the presence of divalent metal salts in the methanolic medium. The complexes are of the type: [M(TML)X2] where, M= Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X=Cl- NO- , CH3COO- and TML is a tetradentate macrocyclic ligand. The complexes have been characterized with the help of various physico-chemical techniques like elemental analyses, conductance measurements, magnetic measurements, NMR, infrared and electronic spectral studies. The low value of molar conductance indicates them to be non-electrolyte. On the basis of various studies a distorted octahedral geometry may be proposed for all the complexes. All the synthesized metal complexes were also tested for their in vitro antibacterial activities against some bacterial strains. The results obtained were compared with standard antibiotic: Ciprofloxacin. Some of the tested complexes shows good antibacterial activities against some bacterial strains.
Keywords: Antibacterial activity; thiocarbohydrazide; macrocyclic complexes; MIC.
INTRODUCTION
The design and study of well-arranged metal-containing macrocycles is an interesting field of chemistry [1]. Several numbers of synthetic and natural macro-cyclic compounds have been investigated [2]. The chemistry of macrocyclic complexes has attracted the interest of both inorganic and bioinorganic chemists in recent years [3]. The field of macrocyclic chemistry of metals is developing very rapidly because of its importance in the area of coordination chemistry [4]. Macrocyclic compounds and their derivatives are interesting ligand-system because they are good hosts for metal anions, neutral molecules and organic cation guests [5]. The metal-ion and host-guest chemistry of macrocyclic compounds are very useful in fundamental studies e.g. in phase transfer catalysis and biological studies [6]. The family of complexes with aza-macro-cyclic ligands has remained a focus of scientific attention for many decades [7]. In-situ one pot template condensation reactions lie at the heart of the macrocyclic chemistry [8]. Therefore template reactions have been widely used for the synthesis of macrocyclic
1 Author for correspondence. Tel.+91 1744 233512 Fax+91 1744 238050.
complexes [9], where generally the transition metal ions are used as templating agent [10]. The metal ions direct the reaction preferentially towards cyclic rather than oligomeric or polymeric product [11]. Synthetic macrocyclic complexes mimic some naturally occurring macrocycles because of their resemblance with many natural macrocycles like metalloproteins, porphyrins and cobalamine [12, 13]. Transition metal macrocyclic complexes have received a great attention because of their biological activities, including antiviral, anticarcinogenic [13] antifertile [14] antibacterial and antifungal [15]. Macrocyclic metal complexes of lanthanides e.g. Gd3+ are used as MRI contrast agents [16]. Prompted by these, in the present paper template synthesis and characterization of macrocyclic complexes of cobalt(II), nickel(II) copper(II) zinc(II) and cadmium(II) derived from acetonylacetone and thio-carbahydrazide has been reported. Besides the characterization of complexes by physicochemical technique like IR, NMR, elemental analyses, magnetic susceptibility and conductance measurements, the biological activities of the synthesized complexes have been examined against some bacterial strains Staphylococcus aureus (MTCC 96), Bacillus subtilis (MTCC 121) (Gram positive), Escherichia coli (MTCC 1652) and
Pseudomonas aeruginosa (MTCC 741) (Gram negative). The results obtained were compared with standard antibiotics Ciprofloxacin.
EXPERIMENTAL
Isolation of complexes: Several attempts to isolate the free macrocyclic ligand were unsuccessful. Therefore, all the complexes were obtained by template synthesis. To a hot, well stirred methanolic solution (—50 cm3) of thio-carbohydrazide (10 mmol) was added divalent cobalt,
nickel, copper, zinc and cadmium salt (Cl-, NO3, CH3COO-) (5 mmol) dissolved in minimum quantity of methanol (20 cm2). The resulting solution was refluxed for 0.5 h. After that, acetonylacetone (10 mmol) dissolved in ~20 cm3 methanol was added in the refluxing mixture and refluxing continued for 6-8 h. The mixture was concentrated to half of its volume and kept in desiccators for overnight. The complexes were then filtered, washed with methanol, acetone and diethyl-ether and dried in vacuo; Yield obtained is ~40-60%. The complexes were found soluble in DMF and DM-SO. They were thermally stable up to ~250°C. The template syntheses of the macrocyclic complexes may be shown by the following scheme:
S
O
O
2H2NHNCNHNH2 + 2H3CCCH2CH2CCH3 +
+ MX
MeOH
26-8 h
[ M( TML) X2 ] + 4H2O,
where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X = Cl-, NO- , CH3COO- and TML = Tetradentate Macrocyclic Ligand.
Analytical and physical measurements: The microanalyses of C, H, and N were carried out at Sophisticated Analytical Instrument Facility, CDRI, Luc-know. The metal contents were determined by standard EDTA methods. Electronic spectra (DMF) were recorded on Cary 14 spectrophotometer. The magnetic susceptibility measurements were carried at IIT Ro-orkee. The IR spectra were recorded on Infrared spectrophotometer in the range 4000-200cm-1 using Nu-jol Mull. The NMR spectra were recorded on Bruker NMR spectrometer (300 MHz).The conductivity was measured on digital conductivity meter (HPG System, G-3001).
RESULTS AND DISCUSSION
Chemistry: The analytical data show the formula for macrocyclic complexes as: [M(C14H24N8S2)X2]; where M = Co(II), Ni(II),Cu(II) Zn(II) and Cd(II)
and X=Cl-, NO-, CH3COO-. The tests for anions are positive only after decomposing the complexes, in-
dicating their presence inside the coordination sphere. Conductivity measurement in DMSO indicated them to be non-electrolyte [17] (10-20 ohm-1cm2 mol-1). Various attempts such as crystallization using mixtures of solvents, low temperature crystallization were unsuccessful to obtain a single crystal suitable for X-ray crystallography. However, the analytical, spectroscop-ic and magnetic data enable us to predict the possible structure of the synthesized complexes. All complexes give satisfactory elemental analyses results as shown in Table 1.
IR Spectra: The presence of single medium intensity bands in the region ~3240-3300 cm-1 in the complexes may be assigned due to N-H stretching vibrations [18]. It was noted that a pair of bands corresponding to v(NH2) stretching frequency appeared at -3280-3308 cm-1 in the IR spectrum of thiocarbohy-drazide but are absent in the IR spectra of all the metal complexes. Further, no strong absorption band was observed near 1700 cm-1 indicating the absence of >C=O of acetonylacetone and thus, confirming the condensation of carbonyl group of acetonylacetone and amino group of thiocarbohydrazide [19]. These results provide strong evidence for the formation of macrocyclic frame [20]. A strong absorption band in the region -1615-1640 cm-1 may be assigned to (C=N) stretching vibrations [21]. The lower values of v(C=N) may be explained on the basis of drift of lone pair density of azomethine nitrogen towards metal atom [22]. The absorption band near ~ 835 cm-1 in the IR spectra of thiocarbohydrazide, also present in all the metal complexes which indicate that sulphur is not coordinated to the central metal atom [23]. The absence of bands near 2550 cm-1 (characteristic of thiol group) rule out the possibility of thione-thiol tautomer-ism [24]. The presence of the absorption bands in the region 1410-1430, 1280-1320 and 1010-1045 cm-1, in the IR spectra of all the nitrate complexes suggest that both the nitrate groups are coordinated to the central metal ion in a unidentate fashion [23]. The IR spectra of the acetate complexes show an absorption bands in the region 1650-1685 cm-1 that is assigned to v(COO-)as asymmetric stretching vibrations of acetate ion and another in the region 1258-1295 cm-1 that can be assigned to v(COO-)s symmetric stretching vibration of acetate ion. A difference between (vas-vs) is around 390-370 cm-1 which is greater than 144 cm-1 indicates the unidentate coordination of the acetate ion with the central metal ion [23].
The far infrared spectra show bands in the region ~425-460 cm-1 corresponding to v(M-N) vibrations [25]. The presence of these bands gives an idea about the coordination of azomethine nitrogen [26]. The bands present at 305-310 cm-1 may be assigned due to v(M-Cl) vibrations [25]. The bands present at 230250 cm-1 in all nitrate complexes are assigned due to v(M-O) stretching vibrations [25].
SYNTHESIS, SPECTROSCOPIC STUDIES AND BIOLOGICAL SCREENING 1471
Table 1. Analytical data of divalent Co, Ni, Cu, Zn and Cd complexes derived from thiocarbohydrazide and acetonylacetone
No. Complexes Found (Calcd.) % Colour Mol. Wt.
M C H N
(1) [Co(CMH24N8S2)Cl2] 11.52(11.84) 33.39(33.73) 4.26(4.82) 22.28(22.49) Brown 498
(2) [Co((CMH24N8S2)(OAc)2] 10.76(10.82) 39.15(39.63) 6.01(5.50) 20.32(20.55) Blackish green 545
(3) [Ni(CMH24N8S2)Cl2] 11.61(11.67) 33.21(33.80) 4.19(4.82) 22.21(22.53) Yllowish brown 497
(4) [N^C^N^XNO^] 10.40(10.54) 30.42(30.54) 4.24(4.36) 25.10(2
Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.