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Synthesis and spectroscopic characterization of new ligand and its Pd(II), Cu(II) metal complexes.

1. INTRODUCTION

Development in inorganic and organometallic chemistry has result in a significantly increased understanding of the bonding, structure and reactivity of coordination compounds, These developments have been applied fruitfully to design of model system that shed light on the behavior of metal ions in biological processes and ultimately to look more closely in those processes themselves [1].

The presence of both hard nitrogen and soft sulphur donor atoms permits coordination with a wide range of transition and non-transition metal ions yielding stable and extremely coloured metal complexes, some of which have exhibited interesting physico-chemical [2-4] and potentially beneficial chemotherapeutic properties [5-8].

On the other side a large number of metal containing therapeutical agents and other biologically active complexes have been prepared and proven to be of great effectiveness in this respect [9].

The importance of metal ions in the living system diver the interest of a large number of researchers in pure inorganic chemistry toward the field of bioinorganic chemistry. Bioinorganic chemistry is a rapidly developing field and there is enormous potential for application in medicine.

Medicinal inorganic chemistry offers real possibities to pharmaceutical industries, which have traditionally been dominated by organic chemistry alone, for the discovery of truly novel drugs with new mechanism of action [10].

A novel Schiff base, 1, 4 dithiane-2, 3-diamine (TAIT) was synthesized by the reaction of thioamide (TA) with imidothioic acid (IT). Tow novel transition metal complexes containing this Schiff base were synthesized by reacting with Pd (II) and Cu (II), It is expected that this study would shed some light on the coordinating properties and future biological activities to the Schiff base and its metal complexes. of alkaloids ephedra and (3) and (4) of the Cinchona [8] (Figure 1) have been used frequently and conducted at good results in terms of stereoselectivity, especially when the substituents in the quaternary nitrogen are bulky.

Although chiral ethers-crown are more resistant to decomposition and have been used successfully, for example, in asymmetric Michael addition reactions, their high cost makes impracticable their use in industrial scale [8].

2. MATERIAL AND METHODS

2.1 Instrumental

The infrared spectra of the prepared compound were recorded using FT-IR (8300) Fourier Transform Infrared spectrophotometer of SHIMADZU Company as potassium bromide (KBr) discs in wave number range of 4000-400 [cm.sup.-1]. The electronic spectra of the complexes were obtained using SHIMADZU UV-Vis 160A Ultra-Violet spectrophotometer at room temperature using quartz cell of 1.0 cm length and using ethanol or DMSO as solvent, in the range of wavelength 200-1100 nm. The magnetic susceptibility values for the prepared complexes were obtained at room temperature using Magnetic susceptibility balance of Johnson Mattey Catalytic System Division, England. The metal content of the prepared complexes was measured using atomic absorption technique by PERKIN-ELMER-5000 atomic absorption spectrophotometer. The molar conductivity measurements were obtained using Corning conductivity 220 apparatus. Gallenkamp M.F.B 60001 of melting point apparatus was used to measure the melting points of all the prepared compounds.

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Synthesis of 2,3-dimine-1,4-dithiarine (LI): 0.92 g (0.02 mol) of KOH was added to ethanolic solution of dithiooxamide 1.202 g (0.01mol) under heating for 5 min until all diothiooxamide was reacted. A 1 mL (0.01 mol) of 1,2- dibromoethane was then added and the mixture was refluxed for 25 min until a golden brown precipitate was formed which was turned to a slight yellow precipitate. The precipitate was finally recrystallized using ethanol then dried under vacuum. Scheme 1 shows the synthesis equation of the new Schiffbase.

Preparation palladium(II)) complex: Dichloro (2,3-dimine-1,4-dithiarine)palladium (II) was prepared by the addition of a solution of 0.145 mmol of palladium chloride dissolved in a sufficient quantity of hot ethanol to the resulting yellow solution (0.290 mmol) of (TATI). The mixture was refluxed for 2 hours and cooled. The resulting deep-brown precipitate was filtered and washed with diethyl ether several times and dried under vacuum. Scheme 2 shows the synthesis equation of square planner Pd (II) complex.

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Preparation copper (II)) complex: This complex was prepared by dissolving 2 mmol of TATI in warm ethanol which was then added 1 mmol of Cu[Cl.sub.2]. 2H2O dissolving in ethanol the mixture was refluxed with stirring yielding greenish-blue color precipitate which was filtered and washed with diethyl ether and dried in vacuum for 3 hours (Scheme 3).

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3. RESULTS AND DISCUSSION

3.1. Physico-chemical data

The physical characterizations of all complexes are shown in Table 1. It also indicates that both metal complexes were in a ratio of 2:1 (Schiff base: metal complex). The melting points of the Schiff base and metal complexes obtained were sharp indicating the purity of the synthesized compounds.

3.2. FTIR Data for the Schiff base and its metal complexes

The thiamine bands of (TAIT) have been fully discussed previously. Where the four bands have been assigned as follows, band (I) is due to u(C=N) (major) +5(N-H) (major), band (II) is due to u(C=N) and u(C=S), band (III) and (IV) are due to u(N-C-S) and u(C-S) frequencies respectively [11, 12].

Table 2 gives the diagnostic frequencies of the TAIT and it metal complexes. In this ligand, the most characteristic band is the aliphatic u(C- H) band at 2859 [cm.sup.-1], beside the four-thioamide bands. Pd (II) and Cu (II) complexes showed a similar spectral changes and as follows; band (I) which appeared as a doublet at 1690 [cm.sup.-1] and 1631[cm.sup.-1], shows itself as a single band at a lower frequency (1645 for Pd (II) complex and 1640 [cm.sup.-1] for Cu complex) upon the complexation with the two ions. Band (II) also shifted to lower frequency upon the complexation appearing at 1512 [cm.sup.-1] for Pd (II) but cupper complex shifted to higher frequency at 1517 [cm.sup.-1], indicating the coordination of these ions through the nitrogen atom of this ligand, another indication for the coordination through only nitrogen atom (and not from the sulfur atom) is that band (III) and (IV) so not change. In the spectra of the two complexes, v M-N band were found at 482 and 528 [cm.sup.-1] for Pd (II), and Cu (II) complexes respectively, as shown in Table 2 and in figures 1, 2 and 3 (See Supplementary Information).

3.3. UV-Vis, magnetic susceptibility and molar conductivity analysis

The UV-Vis spectra of the transition metal with partially filled d-orbital are generally characterized by charge-transfer (CT) bands which involve an electron transfer from M to L during optical excitation by which the oxidation number of central ion is changed by on, while the ligand field bands correspond to the same oxidation number in the excited and the ground state [12, 13]. These redox process bands are strong and their wave numbers decreases (or wavelength increases), the more oxidizing the central ion and the more reducing the ligand. The Pd (II) ion is considered to be weaker as oxidizing as and more stable than their tetravalent states. The first strong band in the spectra of the Pd (II) complexes is assigned as L-MCT band.

The analysis of the UV-Vis spectra of the prepared Pd (II) complex shows the existence of a band in 25,125 [cm.sup.-1] which might be assigned to the transition 1 A1g--1B1g, this came in accordance with the published data for square Pd (II) complexes [13, 14].

Cu (II) compounds are blue or green because of single broad an absorption band in the region (15,432) [cm.sup.-1] [13]. The d9 ion is characterized by large distortion from octahedral symmetry and the band is unsymmetrical, being the result of a number of transitions, which are by no means easy to assign unambiguously (Table 3).

The new Schiff base and its Cu (II) and Pd (II) complexes were synthesized and characterized successfully, these new complexes could be used as bioactive complexes as the SN complexes was used [15, 16].

4. REFERENCES AND NOTES

[1] Hughes, M. N.; Inorganic Chemistry of Biological Processes, 2nd ed. New York: John Wiley and Son, 1988.

[2] Crouse, K. A.; Chew, K. B.; Tarafder, M. T. H.; Kasbollah, A.; Ali, A. M.; Yamin, B. M.; Fun, H. K. Polyhedron 2004, 23, 161. [CrossRef]

[3] Liu, Z. H.; Duan, C.Y.; Hu, J. Inorg. Chem. 1999, 38, 1719. [CrossRef]

[4] Tian, Y. P.; Duan, C. Y.; You, X. Z.; Mak, T. C. W.; Luo, Q.; Zhou, J. Y. Trans. Met. Chem. 1998 23, 17. [CrossRef]

[5] Abu-Raqabah, A.; Davies, G.; El-Sayed, M. A.; El Toukhy, A.; Shaikh, S. N.; Zubieta, J. Inorg. Chim. Acta. 1992, 193, 43. [CrossRef]

[6] West, D. X, Liberta, A. E.; Padhye, S. B.; Chikate, R. C.; Sonawane, P. B.; Kumbhar, A. S.; Yerande, R. G. Coord. Chem. Rev. 1993,123, 49. [CrossRef]

[7] Kasuga, N. C.; Sekino, K.; Ishikawa, M.; Honda, A.; Yokoyama, M.; Nakano, S.; Shimada, N.; Koumo, C.; Nomiya, K. J. Inorg. Biochem. 2003, 96, 298. [CrossRef]

[8] Liberta, A. E.; West, D. X. BioMetals. 1992, 5, 121. [CrossRef][PubMed]

[9] Jassim, A. H. Ph.D. Thesis, AL-Nahrain University, 1993, Iraq.

[10] Davidson, G. Group theory for Chemist 1St ed. London: MacMillan, 1991.

[11] Stewart, J. S. J. Chem. Phys. 1957, 26, 248. [CrossRef]

[12] Jensen, K. A.; Neilsen, P. H. Acta Chem. 1966, 20, 597. [CrossRef]

[13] Lever, A. B. P. Inorganic Electronic Spectroscopy. London, New York:Elsevier publishing Company, 1968.

[14] Huheey, J. E. Inorganic chemistry, principles of structure and reactivity. New Yoork:Cd. Horpar and Row, 1998, p.422-425.

[15] Al-Karkhi, I. H. T. J. Basic Edu. 2012. 18, 1.

[16] Gao, E.; Guan, F.; Gao, X.; Zhu, M.; Liu. L.; Wang C.; Zhang, W.; Sun, Y. J. Biol. Inorg. Chem. 2012, 17, 263.[CrossRef]

Hamsa T. Sadiq (a), Isam H. T. Al-Karkhi (b) * and Ayad H. Jassim (a)

(a) Al-Nahrayn University, Al-Jadreya, Baghdad-Iraq.

(b) Department of Basic Science, College of Dentistry, UniversityofBaghdad, Bab Al-Mozam, Baghdad-Iraq.

* Corresponding author. E-mail: isamhtk@hotmail.com

Article history: Received: 19 April 2013; revised: 31 May 2013; accepted: 15 June 2013. Available online: 10 July 2013.
Table 1. Physical characterization of the synthesized
complexes.

Symbol              Color     ([degrees]C)   Yield   Metal content (%)
                                              (%)

                                                     Calc   Found

TAIT                Golden        198         89      --     --
                    brown
Pd                  Deep-         275         71     29.6   29.02
  [(TAIT).sub.2]    Brown
Cu                 Greenish       125         79     13.8   12.8
  [(TAIT).sub.2]     blue

Table 2. The FT-IR spectral bands the Schiff base,
the metal complexes.

Compound              v C=H     Thioamide   Thioamide
                    Aliphatic   Band (I)    Band (II)
                       N-H         C=N         C=S

TAIT                  2895        1690        1515
                                  1631
Pd [(TAIT).sub.2]     2925        1645        1512
Cu [(TAIT).sub.2]     2931        1640        1517

Compound            Thioamide    Thioamide   M-N
                    Band (III)   Band (IV)
                       NCS          C-S

TAIT                   1021         780      --

Pd [(TAIT).sub.2]      1022         780      482
Cu [(TAIT).sub.2]      1021         781      528

Table 3. Electric spectra, magnetic properties, conductivity
and suggested structures for Pd (II) complexes.

Symbol              Absorption     Magnetic
                    [cm.sup.-1]   properties

Pd [(TAIT).sub.2]   25,125(398)   Diamagnetic
Cu [(TAIT).sub.2]   15,432(648)      1.89

Symbol              Conductivity in DMSO,     Suggested
                     [[micro]sem.sup.-1]      structure

Pd [(TAIT).sub.2]            15             Square-planar
Cu [(TAIT).sub.2]            10              Octahedral
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Title Annotation:Full Paper
Author:Sadiq, Hamsa T.; Karkhi, Isam H.T. Al-; Jassim, Ayad H.
Publication:Orbital: The Electronic Journal of Chemistry
Article Type:Report
Date:Apr 1, 2013
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