3-Hydroxy-2-naphthoate Complexes of Transition Metals with Hydrazine-Preparation , Spectroscopic and Thermal Studies

Reaction of hydrazine and 3-hydroxy-2-naphthoic acid with some transition metal ions forms two types of complexes: (i) [M(N2H4){C10H6(3O)(2-COO)(H2O)2] where M=Ni, Co, Cd and Zn, at pH 9 and (ii) [M(N2H5)2{C10H6(3-O)(2-COO)}2].xH2O where M=Ni & x =1; M=Co, Cd, Mn & x=3; and M=Zn, Cu & x =0 at pH 4. Analytical data confirms the compositions of the complexes. The acid shows dianionic nature in these complexes. The magnetic moments and electronic spectra suggest the geometry of the complexes. IR data indicates the nature of hydrazine and presence of water in the complexes. Simultaneous TG-DTA studies shows different thermal degradation patterns for the two types of complexes. The first type shows formation of no stable intermediates whereas the second type shows the respective metal hydroxy naphthoate intermediates. The final products in both the types are found to be metal oxides of nano size. XRD patterns show isomorphism among the complexes with similar molecular formulae.


Introduction
Hydrazine complexes of the first row transition metal ions with a variety of carboxylic acids have been reported in the literature.These include simple aliphatic mono and dicarboxylic acids 1,2 , aromatic mono and di carboxylic acids 3,4 and heterocyclic carboxylic acids 5 .The hydrazinium metal carboxylates 6 and their hydrates are crystalline solids and mostly water soluble but hydrazine complexes are amorphous powder and are insoluble in water.Many bis-hydrazine and hydrazinium metal carboxylates are used as precursors for metal oxides and mixed metal oxides such as ferrites, cobaltites, chromites etc 7,8 .
3-Hydroxy-2-naphthoic acid is one example of a naphthalene derivative that has been frequently used as the chelating agent.Bin Liu et al. prepared Cr(III) complex with this chelating agent 9 .Fluorescence property and stability constant have been studied 10 .In this paper we report the preparation, characterization and thermal decomposition of some new hydrazine and hydrazinium complexes with this acid.

Experimental
The solvents were distilled prior to use and double distilled water was used for the preparation and chemical analyses.All the chemicals used were of AR grade received from Fluka Chemicals.The hydrazine hydrate was used as such as received.
The above solution mixtures which appeared cloudy at first, turned out to be a micro crystalline solid on digestion when kept over a hot water bath at 90 ºC for 20 minutes.It was cooled, filtered and washed with distilled water, ethanol and then with ether.The crystals were dried in a desiccator over anhydrous CaCl 2 .

and M= Zn &Cu, x =0
A similar procedure was adopted for the preparation of these complexes, with a molar ratio of acid: base: metal ion = 1:2:2, in 60 mL of water-alcohol (1:1) mixture at 60 °C.Cadmium complex was formed with 1:1:4 ratio.The micro crystalline precipitate was formed immediately and the mixture was kept in water bath for 20 min.It was cooled, filtered and washed with distilled water, ethanol and then with ether.The precipitate was dried in a desiccator over anhydrous CaCl 2 .

Physicochemical techniques
The compositions of the complexes were fixed by chemical analysis and confirmed by micro elemental analysis.Hydrazine content was determined by titrating against standard KIO 3 (0.025 mol L -1 ) under Andrew's conditions.Metal contents were determined by titrating with EDTA (0.01 mol L -1 ) after decomposing the complexes with 1:1 nitric acid 11 .
IR spectra of the complexes in the region 4000-400 cm -1 were recorded as KBr pellets using a Perkin Elmer 597 spectrophotometer.Electronic reflectance spectra for the solid state complexes were obtained using a Varian, Cary 5000 recording spectrophotometer.The magnetic susceptibility of the complexes was measured using a vibrating sample magnetometer, VSM EG&G Model 155 at room temperature and the data were corrected for diamagnetism.
The X-ray powder patterns of the complexes were recorded using a Philips X-ray diffractometer (model PW 1050/70) employing Cu-Kα radiation with a nickel filter.The simultaneous TG-DTA experiments were carried out using SDT Q600 V8.3 instrument and Stanton 781 simultaneous thermal analyzer.Thermal analyses were carried out in air at the heating rate of 10 °C min -1 using 5 to 10 mg of the samples.Platinum cups were employed as sample holders and alumina as reference.The temperature range was ambient to 700 °C.

S415
The SEM images of the residual oxides were recorded using a Cambridge Scanning Electron Microscope with EDAX attachment (CF).

Results and Discussion
Electronic spectra, magnetic susceptibility and ESR spectra A band appears in the range 19890-20350 cm -1 and is assigned to the 4 T 1g (P) → 4 T 1g transition of typical six coordinated Co(II) hydrazine complexes.The corresponding nickel complexes show two bands in the region 10480-10790 and 17370-17690 cm -1 which are ascribable to 3 A 2g → 2 T 2g , 3 A 2g → 2 T 1g (F) transitions, respectively, of octahedral Ni(II).The magnetic moment values obtained for the nickel and cobalt complexes, 3.2 and 4.8 BM respectively, confirm the high spin octahedral structures.
The cobalt complexes of hydrazinium transition metal complexes register a band in the regions of 18300 and 20080 cm -1 due to transitions 3 T 1g (F) 4 A 2g (F) and 3 T 1g (F) 4 T 1g (P) of typical six coordinated Co(II) complexes.The corresponding nickel complexes show bands in the regions 16200, 18210 and 26370 cm -1 which are ascribable to transition 3 A 2g 3 T 1g (F) and the copper complex shows bands in the regions 13610 and 18620 cm -1 assigned to 2 B 1g 2 A 2g and 2 B 1g 2 B 2g transitions, respectively, evidence the octahedral geometry of the complexes 12 .The magnetic moment values obtained for the nickel, cobalt, copper and manganous complexes, 3.35, 4.97, 1.83 and 5.8 BM respectively, confirm the high spin octahedral structures.
The axial ESR spectrum for copper complex shown in Figure 1 has features at g ║ = 2.1 and g ┴ =1.9 which indicate that the copper(II) ion geometry is that of a distorted octahedron.

IR spectra of complexes
The IR spectral data of the complexes are summarized in Table .All the compounds show moderately strong bands in the region 3180-3299 cm -1 due to N-H stretching.The asymmetric and symmetric stretching frequencies of carboxylate ions are seen in the range 1600-1654 and 1326-1396cm -1 , respectively with a (ν asy -ν sy ) separation of 245-286 cm -1 indicating the monodentate linkage of both the carboxylate group.

Thermal analysis
The thermal data of the complexes are listed in Table 2.The compositions of the intermediates and the final products are those, which fit with the observed mass losses in TG.Thermogravimetric results are in good agreement with the DTA data.The metal oxides formed after the incineration of the complexes at their decomposition points found from DTA, followed by sintering at the same temperature for about 3-4 h were found to be pure and uniform in nano scale (20-25 nm) as found from XRD using Scherer's formula 14 , D = Kλ / B cosθ where λ is the X-ray wavelength, B is the full width of height maximum (FWHM) of a diffraction peak, θ is the diffraction angle and K is the Scherrer's constant of the order of 0.8.The SEM image of MnO 2 from hydrazinium complex is shown as representative example (Figure 3).

Intensity Gauss Table 1 .
Analytical and IR data of the complexes.
complexes, except zinc and copper in hydrazinium complexes, display a medium broad peak centered on 3440 cm -1 , indicating the O-H stretch of water molecules.An additional sharp peak in the region 838-841 cm -1 is observed which may be due to the presence of coordinated water molecules in [M(N 2 H 4 ){C 10 H 6(3-O)(2-COO)}(H 2 O) 2 ] and sharp peak in the region 517-596 cm -1 is due to presence of lattice water in [M(N 2 H 5 ) 2 {C 10 H 6 (3-O)(2-COO)} 2 ].xH 2 O. Infrared technique serves as finger print technique and the presence of bidentate N 2 H 4 in [M(N 2 H 4 ){C 10 H 6 (3-O)(2-COO)(H 2 O) 2 ] is indicated by the characteristic N-N frequency in the range 960-981 cm -1 .The presence of coordinated hydrazinium cation in [M(N 2 H 5 ) 2 {C 10 H 6 (3-O)(2-COO)} 2 ].xH 2 O has been indicated by the presence of ν N-N in the region 1014-1016 cm

Table 3 .
X ray powder diffraction data of 3-hydroxy -2-naphthoic acid complexes (d spacings in A° and relative intensities in parentheses).-raypowderdiffractiondata of the complexes are summarized in Table3.It is found that the diffraction patterns of hydrazine complexes of Ni, Co, Cd & Zn, hydrazinium complexes of Co, Cd & Mn and hydrazinium complexes of Zn &Cu show similarity among the individuals in each set implying isomorphismConclusionTransition metal ions such as Ni(II), Co(II), Cd(II), Mn(II), Zn(II) &Cu(II) react with 3-hydroxy-2-naphthoic acid and hydrazine hydrate yield hydrazine metal naphthoates at pH 9 and hydrazinium metal naphthoates at pH 4. The magnetic moment and electronic spectra suggest the high-spin octahedral nature of the complexes.Infrared spectra indicate the monodentate nature of carboxylate ions, bidentate bridged nature of hydrazine in bis-hydrazine complexes and coordinated hydrazinium cation in hydrazinium complexes.TG-DTA studies shows different thermal degradation patterns for the two types of complexes.The first type shows formation of no stable intermediates whereas the second type shows the respective metal hydroxy naphthoate intermediates.During the last step of decomposition all the complexes undergo oxidative decomposition to form corresponding metal oxides as final product.Because of the evolution of various gases during decomposition (N 2 , H 2 and CO 2) , the metal oxides formed are fine particles probably with nano size 20-25 nm. X