TEMPLATE SYNTHESIS AND CHARACTERIZATION OF NI(II) COMPLEX DERIVED FROM 4- PHENOXY-2,6-DICHLORO-S-TRAIZINE AND 2,4-DINITROPHENYLHYDRAZINE

Dejene Disasa Irge. New Ni(II) complex was synthesized from 4-phenoxy-2,6-dichloro-straizine and 2,4-dinitrophenylhydrazine in the presence of hydrated metal salt, NiCl2.6H2O in 1,4-dioxane-methanol medium. Before the synthesis of the complex, 4-phenoxy-2,6-dichloro-s-traizine was prepared according to the procedure reported. The complex synthesized was characterized on the bases of chemical analysis, magnetic susceptibility, uv-vis spectroscopy and conductivity data. Based on the data obtained octahedral geometry is proposed.

reactivity of the three chlorine atoms in cyanuric chloride towards nucleophilic reagents decreases as substitution reaction proceeds. The first substitution occurs between -15 0C to 5 0C. The 2nd substitution occurs at 30 0C to 50 0C and the 3rd substitution occurs 90 0C to 100 0C. The stepwise substitution with increasing temperature is due to decreasing electrophilicity of the centers by inductive electron releasing through the bonds (E.M. Smolin and L-Rapport, 1959). The different nucleophilic substitution of cyanuric chloride is depicted In scheme 1 below (Fritz and Vogel, 1994].

Scheme 1:-Nucleophilic substitution of chlorine in cyanuric chloride.
Different derivatives of cyanuric chloride are used to synthesize dyes, herbicides, insecticides, fungicides, pesticides, pharmaceuticals, polymers, biological molecules. Cyanuric chloride can also be used as an intermediate for manufacturing optical brighteners, tanning agents and softening agents (Kishan P.Haval, 2006).

Metal Complexes of S-triazine Based Ligands:-
Chemical substances that are formed by the linkage of metallic species with electron donating ligands are termed as metal complexes. Those that are derived from biologically active organic compounds have important applications in view of enhanced lipo-solubility and reorganized electron density distribution. The coordinating centers and structures of the metal complexes play a vital role in almost all biological activities. It is reasonable to expect suppression or enhancement of herbicide activity when active heterocyclic centers are bound to metal ions (V.J.T. .
Several compounds of S-triazines like atrazine, simazine, prometryn, aziprotryn, e.t.c. have gained worldwide recognition for their outstanding herbicidal properties. However, the wide utilization of these herbicides in the crop management has created a challenging problem in terms of residual herbicides.
They are remnant herbicides in the agricultural products which are causing serious symptoms of illness in animal and human consumers. Two approaches are currently validated in the detoxification of remnant herbicides. One of them is derivatization of the herbicides to less harmful compounds after crop development while the other is the metal ion associated degradation or deactivation of the herbicides. Studies have shown that metal ions can show remarkable effect in catalyzing the decomposition of herbicides (Worku Dinku, 2003). Due to the electronegativity difference between nitrogen and carbon, the electrons in the ring S-triazines are located in the vicinity of nitrogen centers that enable coordination to metal ions (Smolin E. and Rappot L., 1959). Literature survey also reveals the growing interest on synthesis, structure and application of transition and nontransition metal complexes of substituted S-triazine. Complexes of Ca 2+ , Sr 2+ , and Ba 2+ with tri mercapto triazine, and those of Pb 2+ , Ni 2+ , Cu 2+ , and Co 2+ with 2, 4, 6-tris-(2-pyradyl)-1, 3, 5-triazine have been reported(Worku Assefa, 2004). A one dimensional chain [Fe (1, 3, 5-triazine -2, 4, 6-tricarboxylate)[H2O]n nwith hepta coordinate Fe(II) center was prepared by reacting 1, 3, 5-S-triazine-2, 4, 6-tricarboxylate with ferric ions in water and investigated for its magnetic properties(Jose Ramin;. The stereochemical aspects and electrochemical properties of Rh(III), Os(III), Ru(III), and Re(III) metal complexes with tris-(Pyridyl)-1, 3, 5-triazine were reported (Primal Paul, 2002). Co (II), Ni(II), Cu(II), and Zn(II) complexes with 2, 4, 6-tris-(hydrazino) -S -triazine were reported (Belete Kebede;]. The study on the bonding modes of the potentially multidentate ligands provides various synthetic routes for synthesizing magnetic materials, catalysts and biological model compounds. Ligands containing both nitrogen and oxygen exhibit versatile coordination chemistry and are capable of forming polymeric and molecular metal complexes having fascinating structural and magnetic properties. Organotransition metal complexes with O-and N-donor ligands have recently been attracting considerable attention, because they often show structures, reactivities, and physicochemical properties significantly different from those of the complexes with other donor ligands. From the perspective of coordination chemistry, the benefit of using transition metal ions is that the shape of the coordination-building unit can be controlled by choosing the coordination geometries of the metal ions properly. A more specific geometry can then be obtained by thoughtfully bonding suitable functional substituents to the ligands, which will act as intraand/or intermolecular connectors. Thus, inorganic-organic hybrid supramolecular assemblies with unusual network topologies should be accessible through non-covalent interactions, i.e. Hbonding and π-interactions (Young J. Park, 2002).
The chemistry of 2,4-Dinitrophenylhydrazine:-2,4-Dinitrophenylhydrazine (DNPH) also called Brady's reagent is chemical compound C 6 H 3 (NO 2 ) 2 NHNH 2 ). It is relatively sensitive to shock and friction. It is a red to orange solid, usually supplied wet to reduce its explosive hazard. It is a substituted hydrazine, and is often used to qualitatively test carbonyl groups associated with aldehydes and ketons. 2, 4-Dinitrophenylhydrazine can be prepared by the reaction of hydrazine sulfate with 2,4dinitrochlorobenzene.

Scheme 3:-synthesis of DNPH.
Brady's reagent is prepared by dissolving 2,4-dinitrophenylhydrazine in a solution containing methanol and some concentrated sulfuric acid to qualitatively detect the carbonyl functionality of a ketone or aldehyde. A positive test is signalled by formation of a yellow or red product. If the carbonyl compound is aromatic, then the precipitate will be red; if aliphatic, then the precipitate will have a yellow color.
Dinitrophenylhydrazine does not react with other carbonyl-containing functional groups such as carboxylic acid, amids, and esters. For carboxylic acid, amides, and esters, there is resonance associated stability as a lone-pair of electrons interact with the p-orbital of the carbonyl carbon resulting in increased delocalization in the molecule. This stability would be lost by addition of a reagent to the carbonyl group. Hence, these compounds are more resistant to addition reactions (G. Bhagavannarayanad, 2010). Many hydrazides and hydrazones exhibit biological activities. They are also used as metal extracting agents. The hydrazone derivatives are used as fungicides, and in the treatment of diseases such as tuberculosis, leprosy and mental disorders. The complexes of various hydrazones are reported to act as inhibitors of enzymes. Many substituted hydrazides are employed in the treatment of psychotic and psychoneurotic conditions. Carboxylic acid hydrazides are known to exhibit strong antibacterial activities which are enhanced by complexation with metal ions (Avaji PG;).
Two spin-forbidden transitions are also possible, 3 A 2g → 1 E g and 3 A 2g → 1 T 2g . For the case that there are two unpaired electrons, magnetic moments are ranging from 2.9 to 3.4 B.M depending on the magnitude of the orbital contribution. For regular or nearly regular tetrahedral complexes there are characteristic spectraland magnetic properties. In Td symmetry the d8 configuration give rise to a 3 T 1 (F) ground state. The transition from this to the 3 T 1 (P) state occurs in the visible region(15000cm-1) and is relatively strong(ε ≈102) compared to the corresponding 3 A 2g → 3 T 1g transition in octahedral complexes. Thus, tetrahedral complexes are generally strongly colored and tend to be blue or green unless the ligand also has absorption bands in the visible region. Because the ground state, 3 T 1 (F), has much inherent orbital angular momentum, the magnetic moment of truly tetrahedral Ni(II) should be about 4.2 B.M. at room temperature. However, even slight distortions reduce this markedly (by splitting the orbitals degeneracy). Thus fairly regular tetrahedral complexes have magnetic moments in the range of 3.5-4 B.M; for the more distorted ones the moments are 3.0-3.5BM. For the majority of four coordinate nickel two complex, planar geometry is preferred. This is a natural consequence of the d8 configuration, since the planar ligand set causes one of the d-orbitals(dx 2 -y 2 ) to be uniquely high in energy and the eight electrons can occupy the other four d-orbitals but leave this strongly antibonding one vacant. Planar complexes of Ni(II) are thus invariably diamagnetic. They are frequently red, yellow or brown owing to the presence of an absorption band of medium intensity (ε ≈60) in the range 450-600nm but other colors do occur when additional absorption bands are present. Square planar nickel (II) complexes do not have any absorption band below 10000cm-1, due to large crystal field splitting. Hence they can be clearly distinguished from octahedral and tetrahedral complexes (Sathish BP;.
Template method of complex synthesis:-Synthesis of the metal-ligand complex can be carried out in two methods. Synthesizing the full ligand from different precursors accompanied by introduction of the metallic species of interest constitutes one of these methods. In the other method, the different precursors and the metallic species or one of the precursor along with the metallic substance followed by addition of another precursor after some times are allowed to undergo complex formation. This method is known as the template method.
In template method, the reaction is fundamentally enhanced by a particular geometrical orientation that is imposed by metal coordination. The effect recognizes molecular organization because it involves organization of an assembly of atoms with respect to one or more geometrical positions so as to achieve a particular linkage between atoms. A template can be called either positive or negative. In a positive template, two reactive parts of a single molecule can be brought together while negative template keeps the reactive groups apart, thus, suppressing the desired reaction and favoring the intermolecular one.
Metal-template reactions offer simple ways to obtain organic molecules which otherwise involve complicated organic routes, high amount of solvents, small yields and high costs. In such cases, organic molecules act as ligands and the high stability of the complex allows the reaction at the coordinated ligands without complex distraction (F. Albert Cotton and G. Wilkinson, 1988) General Objectives of the Present Investigation:-S-triazine derivatives and their metal complexes have a wide range of applications in agriculture, pharmaceutical, analytical fields, polymer chemistry, and catalysis (Kishan P Haval, 2006]. In addition S-triazine complexes of different metals were studied and reported (Primal Paul, 2002). The s-triazine derivatives in which the chloro group of cyanuric chloride is replaced by nucelophilic functions such as hydrazine derivatives which are electron rich (having better stabilization effect on electron deficient s-triazine ring) are of interest. In view of the wide range of potential application of triazine derivatives, the present investigation is aimed at the synthesis and structural studies on the metal complex synthesized from traizine derivative. The aim is to synthesis 4-phenoxy-2,6-dichloro-Straizine starting from cyanuric chloride and the Ni2+ complex from 4-phenoxy-2,6-dichloro-S-traizine and 2,4dinitrophenyl hydrazine through template method and characterization of the complex using conductivity, magnetic studies and spectroscopic techniques. The synthesis of the 4-phenoxy -2,6-dichloro-S-traizine is already reported (Otilia Costisor and W. Linert, 2004) Experimental part:-Chemicals and solvents:-All chemicals used were of Analar grade. The reagents and solvents are listed below

Solvents:-
The solvents used were distilled water, deionized water, methanol, ethanol, dichloromethane, DMSO, n hexane, acetonitrile, chloroform, deuterated chloroform, THF, DMF, dioxane, benzene Reagents:-Cyanuric chloride, phenol, sodium hydroxide, calsium chloride, 2,4-dinitrophenyl hydrazine, nickel chloride hexahydrated Instrumentation:-Determinations of melting points or decomposition temperatures of the products were done with Stuart SMP3 Digital Melting Point apparatus. The metal quantity in the complex was estimated by BUCK MODEL SCIENTIFIC 210 VGB flame atomic absorption spectrophotometer. The carbon, hydrogen, and nitrogen elemental analysis of were carried out using Flash EA 1112 elemental analyzer. The electronic spectra were recorded on Genesys 2PC (200-850 nm) spectrophotometr. Conductivity was measured using EC 214 Bench conductivity meter. Measurement of magnetic susceptibility of the complexes was carried out by MSB Auto, Sherwood. Several other common laboratory equipments were also used during the investigation.

Synthesis of 4-phenoxy-2,6-dichloro-S-traizine(PDST):-
A suspension of cyanuric chloride (5g, 0.027mol) in 50ml dichloromethane in 250ml round bottom flask, equipped with a magnetic stirrer, was cooled in ice bath. A solution of phenol(2.55g, 0.027mol) and sodium hydroxide(1.08g, 0.027mol) in 20ml water was added drop wise to the suspension over a period of 15 minutes, keeping the reaction in an ice bath wile stirring. The reaction mixture was then stirred continuously for 3hrs at room temperature. The undissolved particles were separated by filtration which results in two different phase solutions (organic and aqueous). The organic phase which contains the sample of interest was then separated by separatory funnel. Calcium chloride was used for drying purpose. The organic solvent, dichloromethane, was separated by rotary vapor which is accompanied by the formation of white product. Recrystalization from chloroform -n-hexane (1:3) mixture was used to obtain a pure product (Otilia Costisor, W. Linert

Synthesis of the complex through template method:-
The metal complex was synthesized from the metal salt (NiCl 2 .6H 2 O) and precursors with same mole ratios; a one to one mole ratio of PDST, synthesized above, 2,4-dinitrophenyl hydrazine(DNPH) and hydrated metal salt(NiCl 2 .6H 2 O). DNPH(0.012mole, 2.45g) dissolved in 30ml of 1,4-dioxane and the metal salt(0.012mol, 2.86g) dissolved in 15ml methanol were mixed and refluxed for two hours, followed by the addition of PDST(0.012mole, 3g) dissolved in 20ml 1,4-dioxane. At this stage the mole ratio of DNP: NiCl 2 : PDST was 1:1:1. The mixture was refluxed for 24 hours. The product obtained was cooled, washed with dioxane and THF, and dried. Results and discussions:- Proposed Reaction mechanism for the preparation of the precursor and the complex:-It is a nucleophilic substitution reaction in which the chloride of the cyanuric chloride is displaced by the oxygen of the phenol. The sodium hydroxide used provides OH-that deprotonate the phenol group. Chloride and water are the leaving group.

Scheme 5:
proposed reaction mechanism for the complex synthesis.
The metal ion is chelated by the 2,4-dinitrophenylhydrazine during the first reflux time. Addition of the 4-phenoxy-2,6-dichloro-s-triazine is followed by nucleophilic attack at one of the chloride substituents. H 2 O, can also potentially replaces the remaining chloride substituents nucleophilically. Because chloride test shows its absence, and the complex was found to be electrolyte, probably the counter anion is the hydroxide ion where also the chlorides were removed as HCl.
Analytical studies:-Qualitative Test:-Thin Layer Chromatography (TLC):-TLC was used to check purity of the compounds. For that matter, 3x5 cm silica coated aluminum plates were used in chloroform and mixture of chloroform and DMF for PDST and the Ni +2 -complex respectively to check their purity. A single spot was observed in both samples that shows purity.
Chloride Test:-0.1gm of the sample complex was dissolved in 10ml concentrated nitric acid and heated repeatedly to decompose organic contents until 2 to 3 drops are left. To the digested solution 0.1N of AgNO 3 was added, and allowed to stand overnight. No precipitate was formed which confirms absence of chlorine in the complex.

Quantitative determination of the metal content:-
The metal contents of the complexes were determined spectroscopically using atomic absorption spectrophotometer. A metal percentage was used to arrive at the metal to ligand ratio in the complexes. A 20 mg of the metal complex dissolved in 10 ml of concentrated nitric acid was digested with gradual and repeated addition of 10 ml portions of the acid until the organic content of the complexes decomposes. After the decomposition, the metal ions remain in the container. The residue was diluted to 50 ml using deionized water and subjectedto AAS analysis. The experimental percentage of metal in the complex was obtained from the AAS data as: Mass of the sample taken x 1000 The result obtained was corrected by the blank measurements taken as a control.

Molar conductance measurement:-
The molar conductance was determined at 24 0 C of temperature by taking 0.02gm of the complex in 50ml of deionized water, a 10-3M solution, and the molar conductance was found as follows:  The result indicates that the complex is a conductor (an electrolyte) and it is in the range of three ions.

Magnetic Susceptibility measurement:-
The gram susceptibility (χg) for the samples has been measured at 240C temperature. The following calculations were made to arrive at the magnetic moments.
Where: χg-Is gram susceptibility χm-Is molar susceptibility χm-is subjected to diamagnetic correction to obtain corrected molar magnetic susceptibility (χmcorr.), from which the magnetic moment is finally calculated in Bhor magneto The Ni(II)-L complex has a magnetic moment of 2.99BM. The value is slightly greater than spin only value for d 8 systems with two unpaired electrons which may be due to orbital contribution.

Magnetic moment (eff ) == 2.828(Xm corr x T)1/2(BM)
Electronic spectrum:-Electronic absorption spectra are often very helpful in the evaluation of results furnished by other methods of structure investigation. The electronic spectral measurements were used for assigning the stereochemistry of metal ions in the complexes based on the positions and numbers of d-d transition bands. The electronic spectra of the precursors, PDST and DNPH, were recorded in acetonitrileand THF respectively while for Ni-L, it was recorded in water. The UV-vis spectral data of the precursors and the complex are given in table 6. Even if both PDST and DNPH are already characterized and reported, to determine the shift of bandswhen complex is formed, their uv-vis spectrum were recorded in this particular study. Electronic absorption spectral bands of PDST were observed in the two main UV regions: 236 and 250(appendix1). These bands may be attributed to π→π* transitions of C=C and C=N respectively. Similarly, in DNPH two absorption bands were observed at 261 and 351nm (appendix2) that may be due to π→π* transitions of C=C and O=N respectively. On complexation, the second bands of both precursors (250nm and 351nm respectively) were affected which may be due to coordination of 'O' of DNPH and 'N' of PDST to the metal (appendix3). Both π→π* transition of C=N and O=N shows a shift to longer wave length (250 nm to 260 nm and 351 nm to 359 nm respectively). Beside these, to look for a d-d transition for the metal ion of the complex, a resolution has been done and characteristic bands in visible region which are assignable to d-d transition are observed. Three bands are clearly observed around 720, 660, and 565 nm which are assignable to transitions 3A2→3T2, 3A2→ 3T1(P) and 3A2→3T2(F) respectively. Based on the data presented in table 6 along with assignment of transitions, octahedral geometry has been proposed for Ni-L complex.