SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATIONS OF MANGANESE(II), IRON(III), COPPER(II) AND ZINC(II) HYDRAZINE COMPLEXES AS CATALYTIC ACTIVITY AGENTS

ABSTRACT. This article deals with the preparation and coordination of NH2—NH2 hydrazine molecule compounds. The hydrazine sulfate complexes of Mn(II), Fe(III), Cu(II), and Zn(II) were prepared. These complexes were characterized by elemental, infrared, conduction, electron absorption spectroscopy, magnetic susceptibility, thermogravimetric analyses, X-ray powder diffraction (XRD) patterns and atomic force microscopy (AFM) studies. The magnetic measurements were confirmed that the Mn(II), Fe(III), Cu(II), and Zn(II) hydrazine complexes have an octahedral geometric structure. Thermogravimetric and its differential thermogravimetric analysis referred that all complexes passed through two-to-three thermal degradation steps with solid metal sulfate as a residual product. The infrared spectra inferred that the NH2—NH2 ligand forms complexes through nitrogen atoms of the—NH2 moiety, while the elemental analysis indicates [M(NH2—NH2)3]SO4 (where M = Mn(II), Cu(II), and Zn(II)) while the iron(III) complexes have the [Fe2(NH2—NH2)4(SO4)2]SO4 formula of coordination compounds, NH2—NH2 acts as a double bond. Both XRD and AFM analysis deduced that the synthesized hydrazine metal complexes were found to be in nano scale range 10—30 nm.


INTRODUCTION
Many important properties of coordination compounds embrace the nature of ligand donor, hydrazides being one of the best suited types of ligands to enhance the metal some important properties [1]. As a result of their antimicrobial, antifungal and antibacterial properties [1][2][3], hydrazides are of great biological importance. The formation of mineral complexes plays an important role in the growth of their biological activity [4][5][6][7][8]. Also, the simple organic molecule hydrazine has been widely used as a reducing agent for the synthesis of some metal nanoparticles due to its pH and temperature dependent reducing ability of hydrazine which makes controlling the rate of reduction easy. Hydrazine is basic and the chemically active free ion is the hydrazium cation. The standard reduction potential of a hydrazine ion is −0.23 eV in acidic solution, but in basic medium the standard reduction potential of hydrazine is −1.16 eV [9,10]. Narrowly distributed nickel micropowders were prepared from the reduction of hydrazine complexes in aqueous solution at 60 °C. It was found that the phase and composition of the hydrazine compound used as a precursor depends on the structural state. Pure hydrazine complexes, [Ni(N2H4)3]Cl2 with the molar ratio of N2H4:Ni 2+ = 3:1 [11] were prepared, while fine nickel powders with controllable particle sizes were synthesized by reducing the precursor of the nickel hydrazine complex in aqueous solution. The mechanism of formation of nickel-metal powders examines the reduction of nickel hydroxide by hydrazine released from the ligand exchange reaction between a nickel-hydrazine compound and NaOH. Compared with the method of preparing nickel powders from nickel salts, the method of making nickel powders by reducing the precursor of the hydrazine compound from nickel shows the advantages of using half a dose of hydrazine to completely reduce the nickel ions in the solution, and the obtained nickel particles show less agglomeration and better dispersion. Moreover, the average particle size of nickel powders can be controlled from 180 to 260 nm by adjusting the reaction molar ratio and concentration [12]. One of the bonds found in the primary explosive format is hydrazine. A research team in China prepared and studied a compound commonly referred to as NHN -nickel hydrazinium nitrate [13]. In this paper, we report the preparation of hydrazine manganese(II), iron(III), copper(II) and zinc(II) complexes as catalytic activity agents.

Elemental analysis and molar conductance studies
Elemental analysis data of hydrazine complexes of Mn(II), Fe(III), Cu(II), and Zn(II) complexes are very close to the theoretical values as shown in Table 1 Table 1, conductance data show that the metal complexes are electrolyte indicating the sulfate ions are located outside the coordination sphere and are directly acts as an ionic statement outside the coordination sphere. The cations and anions were estimated by using typical analytical procedure [14].

Electronic spectroscopy and magnetic susceptibility studies
All the complexes have magnetic susceptibilities except Zn(II) diamagnetic complex [15]. Manganese(II) complex has magnetic moment value of 5.56 B.M. suggesting octahedral environment. The electronic spectra of Mn(II) complex registers electronic bands at 450 nm and 550 nm, which can be assigned to 6 A1g→ 4 T2g (G) and 6 A1g→ 4 T1g (G) transitions of Mn(II) ion in a spin free d 5 configuration confirming to octahedral arrangement [15]. The electronic spectrum of diiron complex [Fe2(NH2-NH2)4(SO4)2]SO4 exhibit three absorption bands at 520, 430, and 390 nm, which may be assigned to transitions 6 A1g→ 4 T1g, 6 A1g→ 4 T2g, 6 A1g→ 4 A1g, 4 Eg, respectively [16] and suggests octahedral geometry. The magnetic moment of iron(III) complex obtained 5.86 B.M. is in good agreement for six-coordinated dinuclear iron(III) system and consistent with the presence of a five-unpaired electrons [17]. The spectrum of copper(II) complex showed an absorption band at 735 nm. This band appears due to 2Eg→ 2 Tg transition in an octahedral field. The copper (II) complex has magnetic moment of 1.82 B.M., which is usually observed for octahedral Cu(II) complex [15,17].

Infrared and Raman studies
Hydrazine (H2N-NH2) coordinates to a metal ion as a unidentate or a bridging bidentate ligand. According to Nicholls and Swindells [18], the complexes of the former type exhibit the ν(N-N) near 930 cm -1 , whereas those of the latter type show it near 970 cm -1 . The IR spectra of hydrazine complexes of M(II) (M = Ni, Co, Zn, Cd) [19], Os(II) [20], and Ln(III) (Ln = Pr, Nd, Sm) [21] have been reported. In these compounds, hydrazine acts as a unidentate or bridging bidentate ligand. Characterization of most of the hydrazine complexes in the literature has relied heavily upon IR spectroscopy and as a result, the proposed structures are still not unambiguous. It has been claimed from IR studies that the position of ν(N-N) in monodentate hydrazine complexes occurs at 928-937cm -1 whereas for complexes which contain bidentate or bridging hydrazine ν(N-N) occurs at 948-980 cm -1 . These bands are all at higher frequency than free hydrazine (875 cm -1 ) [22]. The location of the N-N stretching frequency has been widely used [23] as a criterion for determining the mode of the bonding between hydrazine and metal ions. Thus, a band in the 930 cm -1 region is attributed to ν(N-N) in unidentate hydrazine while a band around 970 cm -1 is attributed to ν(N-N) in bidentate hydrazine. In hydrazine itself there is disagreement about the assignment of ν(N-N) (as well as of other fundamentals); Durig et al. [23] assigning ν(N-N) in N2H4 to a band at 1126 cm -1 while other workers [18][19][20][21][22] assign a band in the 880 cm -1 region to this mode.    (Table 2 and Figure  1), that confirmed the coordination of hydrazine ligand towards metal ions through both nitrogen atoms as a bidentate (Figure 2). Accordingly, bidentate chelating and bridging sulfato groups belong to the lower symmetry C2V. However, the vibrations of the bidentate sulphate group in this complex [Fe2(NH2-NH2)4(SO4)2]SO4, can be assigned for the various SO4 -2 modes [24]. Two bands with strong intensities occur in the region above 1000 cm -1 at 1132, 1051 and 896 cm -1 are assigned to the different symmetric and antisymmetric bond vibrations, n(SO4) 2-, while the bending motion of (SO4) 2is assigned to the band at 630 cm -1 .  Table 3. All the complexes start losing NH2-NH2 molecules from 115 ºC and this subsequent decomposition seems to be a continuous process with endotherms at temperature ranging from 115-450 ºC associated with hydrazine removal with no distinct intermediate formation.
The end residual products were analyzed to be MnSO4, Fe2(SO4)2, CuSO4 and ZnSO4 for Mn(II), Fe(III), Cu(II), and Zn(II) complexes, respectively, confirmed by FTIR of residues and comparison with commercial metal sulfate salts.   303RT where a is the fraction reacted in time (t), T is temperature in K, A is the pre-exponential factor in min -1 , φ is the heating rate, E is the activation energy in kJ/mol and R is the gas constant. Plotting Y vs. 1/T gives a straight line for a parameter, n where Y = 1 -(1 -α) n-1 /(1-n)T 2 . The activation energy E can be calculated from the slope and the A factor from the intercept. Kinetic studies reveal that all the complexes follow same mechanism of decomposition as inferred from their computed E values. The activation energy for decomposition of the complexes is found to almost similar in the range of 6.79-1.30 J/mol -1 . Table 4 shows the computed kinetic parameters and the decomposition steps for all the metal complexes.  Table 5 and display in Figure 4. The X-ray powder diffraction data of the complexes show similarity among the individuals in each set, implying isomorphism. Also, these complexes were found to be pure and uniform in nano scale range (10-26 nm) as found from XRD using Scherer's formula [26], D = Kλ/β cos θ where λ is the X-ray wavelength, β 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 0.89. For accurate particle size calculations and morphological properties of [Zn(NH2-NH2)3]SO4 complex surface, AFM-microscopy tapping mode was applied on the solid powder to evaluate nano-metric features of the resultant materials. Figure 5 shows the threedimensional image for [Zn(NH2-NH2)3]SO4 complex through tapping mode, it was observed that movement of the tip through the z-axis not similar which means that the up and down zones of the surface is not homogeneous through the scanned area which is too small (0.5 x 0.5 µm). The analysis of the XRD and AFM indicated that the average particle size for [Zn(NH2-NH2)3]SO4 complex sample is ranged ~ 15 nm which confirm that [Zn(NH2-NH2)3]SO4 complex synthesis technique yields to nano-product.

CONCLUSIONS
In the present study, we reported the synthesis, and characterization of Mn(II), Fe(III), Cu(II) and Zn(II) hydrazine adducts. The empirical formula of hydrazine complexes agrees with the elemental, infrared, conduction, electron absorption spectroscopy, magnetic susceptibility, thermogravimetric analyses, XRD patterns and atomic force microscopy (AFM). Results of various spectroscopic characterization of ligand and its complexes revealed that both are stable at room temperature and soluble in DMF and DMSO solvents and ligands were effectively coordinate with metal ions via the two nitrogens atoms of hydrazine moiety and developed into a coloured hexacoordinate stable [M(NH2-NH2)3]SO4 (M = Mn(II), Cu(II), and Zn(II)) and [Fe2(NH2-NH2)4(SO4)2]SO4complexes.