Mechanochemical synthesis and characterization of 2,4-dinitrophenyl hydrazine metal complexes.Introduction
2,4-dinitrophenylhydrazine is an analogue of hydrazine hydrazine (hī`drəzēn'), chemical compound, formula NH2NH2, m.p. 1.4°C;, b.p. 113.5°C;, specific gravity 1.011 at 15°C;. It is very soluble in water and soluble in alcohol. and an important class of drugs.
Recently, there has been a considerable interest in the chemistry of hydrazine compounds because of their potential pharmacological applications . Several reports on synthesis of metal complexes of hydrazine by the use of organic solvents under reflux and their biological properties have already been published. [2,3]. More so, these methods suffer several drawbacks such as long reaction time, an excess of organic solvent, lower products yield and harsh refluxing conditions. Therefore, it is necessary to develop more efficient and versatile method for the preparation of metal complexes of 2,4-dinitrophenylhydrazine and the progress in this area is remarkable, including the use of mechanochemical mech·a·no·chem·i·cal
Of or relating to conversion of chemical energy into mechanical work. method. This method is a solvent-free reaction which leads to new environmentally benign procedures that save resources and energy . The mechanochemical reaction promises to be an essential facet of "Green Chemistry" and is of high interest from both the economical and synthetic point of view. Solvent-free reactions possess some advantages over traditional reactions in organic solvents, for example they not only reduce the burden of organic solvent disposal, but also enhance the rate of many inorganic reactions.
Mechanochemical synthesis is the use of a mortal and a pestle pestle /pes·tle/ (pes´'l) an implement for pounding drugs in a mortar.
A club-shaped, hand-held tool for grinding or mashing substances in a mortar. or the more reproducible use of a ball-mill to grind the starting material in order to generate a complex series of structural transformations due to the vibrational effects caused by grinding of the reactants (two solid substances) [5,6]. Recent reports on the usefulness of mechanochemical synthesis was described by Kaupp et al.  via grinding a schiff base derived from benzaldehyde benzaldehyde (bĕnzăl`dəhīd) or benzenecarbonal (bĕn'zēnkär`bənəl), C6H5CHO, colorless liquid aldehyde with a characteristic almond odor. and sulphonamide sulphonamide or US sulfonamide
Pharmacol any of a class of organic compounds that prevent the growth of bacteria with metal salts of Cu(II), Ni(II) and Co(II) to give neutral complexes of configuration [M[(L).sub.2].[([H.sub.2]O).sub.2]].C[L.sub.2]. Braga et al  reported the use of mechanochemical method for the synthesis of Cu(INA)2 by grinding of copper acetate and isonicotinic acid. Pichon and James  synthesized cis-Pt[Cl.sub.2](P[Ph.sub.3]) by mechanochemical method. The reaction was carried out by grinding Pt[Cl.sub.2] and P[Ph.sub.3] in a ball mill for one hour. Nichols et al  described that simple, manual grinding of divalent divalent /di·va·lent/ (di-va´lent) bivalent; carrying a valence of two.
di·va first-row halides or nitrates with phenanthroline resulted in clear color changes of the [[M[(Phen).sub.3]].sup.2+] such as red [[Ni[(Phen).sub.3]].sup.2+] within two minutes. Braga et al  reported the synthesis of Zn(II) and Cu(II) neuroleptic neuroleptic /neu·ro·lep·tic/ (-lep´tik) originally, referring to the effects on cognition and behavior of the first antipsychotic agents: a state of apathy, lack of initiative, and limited range of emotion, and in psychotic patients, drug (Gabapentin) without the use of Solvent.
Due to our interest in green chemistry, we reported the synthesis of 2,4-dinitrophenyl hydrazine metal complexes in an attempt to examine the modes of binding in solid state solvent-free mechanochemical.
Materials and Instrumentation: All reagents and chemicals were of analytical grade and used as obtained from Aldrich. The ligand used is 2,4-dinitrophenylhydrazine. The metal salts used include copper acetate [Cu[(C[H.sub.3]COO).sub.2] x 4[H.sub.2]O], nickel acetate [Ni[(C[H.sub.3]COO).sub.2] x 4[H.sub.2]O], cobalt acetate [Co[(C[H.sub.3]COO).sub.2] x 4[H.sub.2]O], and zinc acetate [Zn[(C[H.sub.3]COO).sub.2] x 4[H.sub.2]O]. IR spectra of the samples in KBr pellsets were obtained in the ranges of 4000-400 [cm.sup.-1] using FTIR FTIR Fourier Transform Infrared (spectroscopy)
FTIR Frustrated Total Internal Reflection
FTIR Fourier Transfer Ir spectrometer. Metal Analyses were determined by atomic absorption spectroscopy In analytical chemistry, Atomic absorption spectroscopy is a technique for determining the concentration of a particular metal element in a sample. Atomic absorption spectroscopy can be used to analyse the concentration of over 62 different metals in a solution. with Perkin-Elmer Spectrometer, model 3110. UV-Vis spectra were obtained on Aquamate v4.60 spectrophotometer spectrophotometer, instrument for measuring and comparing the intensities of common spectral lines in the spectra of two different sources of light. See photometry; spectroscope; spectrum. . Powder XRD XRD X-Ray Diffraction
XRD X-Ray Diode analysis was prformed on a Syntag PADS diffractometer A Diffractometer (Main Entry: dif·frac·tom·e·ter Pronunciation: di-"frak-'tä-m&-t&r Function: noun) is a measuring instrument for analyzing the structure of a usually crystalline substance from the scattering pattern produced when a beam of radiation or particles (as X rays or at 294K using Cu K[alpha] radiation ([lambda] = 1,54059 [Angstrom]).
Synthesis of the complex:
The methods described by Pichon and James  were modified and adopted for the synthesis of all the metal complexes by mechanochemical method.
Synthesis of [Cu[(DNPH DNPH 2,4-Dinitrophenylhydrazine ).sub.2][(C[H.sub.3]COO).sub.2]] complex
(2mmol, 0.396g) of 2,4-dintrophenyl hydrazine and (lmmol, 0.182g) of copper acetate were weighed carefully into a mortar. The two reactants were crushed (ground) for fifteen (15) minutes to obtain a lemon powder. The powder was removed from the mortar and stored in a desiccator des·ic·cate
v. des·ic·cat·ed, des·ic·cat·ing, des·ic·cates
1. To dry out thoroughly.
2. To preserve (foods) by removing the moisture. See Synonyms at dry.
Synthesis of [Zn[(DNPH).sub.2][(C[H.sub.3]COO).sub.2]] complex
(2mmol, 0.396g) of 2,4-dinitrophenylhydrazine and (lmmol, 0.220g) of Zinc acetate were weighed carefully into a mortar. The two reactants were then crushed (ground) for fifteen (15) minutes to obtain an orange powder. The powder was removed from the mortar and stored in a desiccator.
Synthesis of [Ni[(DNPH).sub.2][(C[H.sub.3]COO).sub.2]] complex
(2mmol, 0.396g) of 2,4-dinitrophenyl hydrazine and (lmmol, 0.249g) of nickel acetate and weighed were carefully into a mortar. The two reactants were crushed (ground) for fifteen (15) minutes to obtain an orange powder. The powder was removed from the mortar and stored in a desiccator.
Synthesis of [Co[(DNPH).sub.2][(C[H.sub.3]COO).sub.2]] complex
(2mmol, 0.396g) of 2,4-dinitrophenylhydrazine and (lmmol, 0.396g) of cobalt acetate were carefully weighed into a mortar. The two reactants were then crushed (ground) for fifteen (15) minutes to obtain an orange powder. The powder was removed from the mortar and stored in a desiccator.
Results and Discussion
The Ni (II), Cu(II), Co(II) and Ni(II) complexes of 2,4-dinitrophenylhydrazine were synthesized by reaction of metal salts with 2,4-dinitrophenylhydrazine. The complexes were characterized by AAS, Conductivity, TLC TLC total lung capacity; thin-layer chromatography.
1. thin-layer chromatography
2. , infrared, UV-Vis spectroscopy and XRPD XRPD X-Ray Powder Diffraction . The complexes are generally soluble in methanol, DMSO DMSO dimethyl sulfoxide.
Dimethyl sulfoxide; a colorless hygroscopic liquid obtained from lignin, used as a penetrant to convey medications into the tissues.
n. but insoluble in non-polar organic solvent. The physical properties of the various complexes are shown in Table 1. All the complexes synthesized were coloured ranging from their parent ligand colours of lemon to orange and light pink. The complexes are also non-hygroscopic solids with different melting point ranging from 156 to 206[degrees]C. All complexes have melting points higher than their respective parent drug probably due to complexation. The molar conductance values measured in DMSO solution ([10.sup.-3] M) for these complexes are in 98-132 [[OMEGA].sup.-1] [mol.sup.-1] [cm.sup.2] range (Table 1). According to these results, the complexes are electrolytes. Determination of stoichiometric stoi·chi·om·e·try
1. Calculation of the quantities of reactants and products in a chemical reaction.
2. The quantitative relationship between reactants and products in a chemical reaction. ratio using job's method suggested mole ratio 1:2 metal to ligand stoichiometry stoichiometry
Determination of the proportions (by weight or number of molecules) in which elements or compounds react with one another. The rules for determining stoichiometric relationships are based on the laws of conservation (see for the complexes. The proposed structures of the complexes are shown in figures 3 and 4.
Since the retention factor, [R.sub.f] value (0.90, 0.54, 0.65, 0.50, 0.83) of the ligands and mixtures different from one another respectively; it shows that a new product might have been formed. Also, since only spot is present, the complexes formed are pure.
UV-Visible Spectrometry Results
The UV-VIS. Spectra of 2,4-diphenylhydrazine and its complexes in methanol present two absorption bands maxima at 256 and 296 nm assigned to [pi] [right arrow] [[pi].sup.*] and [pi] [right arrow] [pi]* transitions within the organic ligand. The cobalt (II) complex exhibits 3 bands at 455, 510 and 678nm assigned to [sup.4][T.sub.1g] [right arrow] [sup.4][T.sub.1g](P), [sup.4][T.sub.1g] [right arrow] [sup.4][A.sub.2g] and [sup.4][T.sub.1g] [right arrow] [sup.4][T.sub.2g]. Nickel(II) complex also shows 3 bands centered at 434, 645 and 767 nm which corresponds to [sup.3][A.sub.2g] [right arrow] [sup.3][T.sub.1g](P), [sup.3][A.sub.2g] [right arrow] [sup.3][T.sub.1g] and [sup.3][A.sub.2g] [right arrow] [sup.3][T.sub.2g]. The zinc(II) complex with no d-d transition shows two bands at 285 and 352nm assigned to [pi][right arrow] [[pi].sup.*] and MLCT MLCT Metal-to-Ligand Charge-Transfer . The copper(II) complex exhibits a broad band centered around 821nm which corresponds to [sup.2][E.sub.g] [right arrow] [sup.2][T.sub.2g]. All these characteristic bands observed in the UV-VIS. Spectra confirm octahedral oc·ta·he·dral
Having eight plane surfaces.
octa·hedral·ly adv. configuration for all the complexes .
Infrared Spectroscopy Results
The vibration bands at 3319[cm.sup.-1], 3092 [cm.sup.-1] assigned to vN[H.sub.2] in the ligand shifted to higher wave number in all the complexes except [Co[(DNPH).sub.2][(C[H.sub.3]C[O.sub.2]).sub.2]]; this is probably due to coordination of metal via Nitrogen of N[H.sub.2] group. The characteristic hyrazinic band (vN-N) appeared at 972 [cm.sup.-1] in the free ligand. This hydrazinic nitrogen is observed in accordance with those reported [1, 13]. It can be observed that the absorption frequency of this band has increased to 1034-1050 [cm.sup.-1] . The principle behind this phenomenon is due to the donation of the unpaired electrons from one of the nitrogen ones to the metal(II) ion, incidentally deflating the repulsion force subsequently, shifting the absorption frequency to a higher value [14,15]. The vN-H bending at 1623[cm.sup.-1] in the ligand shifted to lower frequency 1511-1578[cm.sup.-1], this also supported the involvement of hydrazinic nitrogen in coordination. The presence of acetate in the coordination sphere of the metal confirmed by the vas(C[O.sub.2]) at 1434-1424 [cm.sup.-1] and vs(C[O.sub.2]) at 1310-1350 [cm.sup.-1] this indicates the possible coordination of carboxylate carboxylate,
n a carboxylic acid salt, ester, or ion. group to metal . The new bands within 515-548 [cm.sup.-1] and 670-690 [cm.sup.-1] are assigned to v(M-O) and v(M-N). These bands confirmed the coordination of 2,4 diphenylhydrazine to the metal(II) ion [16,17]. Spectral data shows that all the complexes are octahedral. The ligand 2,4 diphenylhydrazine is bidentate bi·den·tate
Having two teeth or toothlike parts.
Adj. 1. bidentate - having toothlike projections that are themselves toothed
rough - of the margin of a leaf shape; having the edge cut or fringed or scalloped . Each metal ion coordinating to the nitrogen of N[H.sub.2], nitrogen of the Hydrazinic band and oxygen atom from each of two acetate ions to complete the octahedral structure.
Results of the X-Ray Powder Diffraction
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
The X-ray powder diffraction patterns (Figures 1 and 2) of the mixture of 2,4-DNPH and copper acetate was compared with that of DNPH and there was difference in the diffraction patterns of both. The peaks observed for the ligand (2,4-DNPH) are 2[??][degrees]: (23.19, 30.01, 46.07, 57.13, and 60.86). The peaks present in the mixture-[Co [(DNPH).sub.2][(C[H.sub.3]COO).sub.2]][).sub.2]] complex are 2[theta] : (19.21, 30.42, 46.55, 57.91, 60.00). In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke"
put differently , some values observed for the ligand are absent in the [Co[(DNPH).sub.2][(C[H.sub.3]COO).sub.2]]] complex which shows that complexation of 2,4-DNPH and copper acetate might have occurred.
Proposed Structures of 2,4-DNPH metal complexes:
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
Cu(II), Co(II), Zn(II) and Ni(II) of 2,4-dinitrophenyl hydrazine complexes were synthesized in the absence of solvent. They were characterized by AAS, Conductivity, TLC, Infrared, UV-Vis spectroscopy and X-ray powder diffraction. The modes of binding in solid state solvent-free mechanochemical of all the complexes formed involve the ligand coordination with the metal ion through the Nitrogen of the N[H.sub.2] group and nitrogren of hydrazinic band and oxygen atom from each of the two acetate ions to complete octahedral geometry. The ligand is bidentate in nature. Mechanochemical method represents an ideal method of synthesizing compounds with no environmental pollution on the order of several minutes when compared to the solvent based that lead to the environmental pollution and takes longer period of time
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Adedibu Clement Tella *, Aaron Yissa Isaac and Rihanat Adeola Adeniran
Department of Chemistry, P.M.B. 1515, University of Ilorin, Nigeria
* Corresponding Author E-mail: email@example.com
Table 1. Analytical data for 2,4-dinitrophenylhydrazine and its complexes Ligand/mixture Colour Melting point [degrees]C DNPH(ligand) Brick red 192 [Cu[(DNPH).sub.2] Lemon 156 [(CH3COO).sub.2]] [Co[(DNPH).sub.2] Orange 200 [(C[H.sub.3]COO).sub.2]] [Ni[(DNPH).sub.2] Light Pink 188 [(C[H.sub.3]COO).sub.2]] [Zn[(DNPH).sub.2] Orange 206 [(C[H.sub.3]COO).sub.2]] Ligand/mixture Conductivity TLC % [[OMEGA].sup.-1] Metal [mol.sup.-1] [cm.sup.2] DNPH(ligand) - 0.90 - [Cu[(DNPH).sub.2] 105 0.54 11.34 [(CH3COO).sub.2]] [Co[(DNPH).sub.2] 111 0.65 10.95 [(C[H.sub.3]COO).sub.2]] [Ni[(DNPH).sub.2] 98 0.50 10.55 [(C[H.sub.3]COO).sub.2]] [Zn[(DNPH).sub.2] 132 0.83 11.87 [(C[H.sub.3]COO).sub.2]] Table 2: UV-Visible spectra 2,4-dinitrophenylhydrazine metal complexes. Complexes/ligand Wavelength(nm) Energies DNPH 256 39063 296 33784 [[Co DNPH).sub.2] 455 21978 [(C[H.sub.3]COO).sub.2]] 510 19608 678 14749 Ni[(DNPH).sub.2] 434 23041 [(C[H.sub.3]COO).sub.2]] 645 15504 767 13038 [Cu[(DNPH).sub.2] 821 12180 [(C[H.sub.3]COO).sub.2]] [Zn[(DNPH).sub.2] 285 35088 [(C[H.sub.3]COO).sub.2]] 352 28409 Complexes/ligand Energies Assignment DNPH 256 [pi][right arrow][[pi].sup.*] 296 n[right arrow][[pi].sup.*] [[Co DNPH).sub.2] 455 [sup.4][T.sub.1g][right arrow] [(C[H.sub.3]COO).sub.2]] [sup.4][T.sub.1g](P) 510 [sup.4][T.sub.1g][right arrow] [sup.4][A.sub.2g] 678 [sup.4][T.sub.1g][right arrow] [sup.4][T.sub.2g] Ni[(DNPH).sub.2] 434 [sup.3][A.sub.2g][right arrow] [(C[H.sub.3]COO).sub.2]] [T.sub.1g](P) 645 [sup.3][A.sub.2g][right arrow] [T.sub.1g] 767 [sup.3][A.sub.2g][right arrow] [T.sub.2g] [Cu[(DNPH).sub.2] 821 [sup.2][E.sub.g][right arrow] [(C[H.sub.3]COO).sub.2]] [sup.2][T.sub.2g] [Zn[(DNPH).sub.2] 285 [pi][right arrow][[pi].sup.*] [(C[H.sub.3]COO).sub.2]] 352 MLCT Table 3: Infrared spectra result for DNPH metal complexes. Ligand/Complex v(N[H.sub.2]) v(N-H) v(N-N) DNPH (Ligand) 3319, 3092 1623 972 [Zn[(DNPH).sub.2] 3460,3108 1578 1034 [(C[H.sub.3]COO).sub.2]] [Co[(DNPH).sub.2] 3321,3091 1580 1045 [(C[H.sub.3]COO).sub.2]] [Ni[(DNPH).sub.2] 3475, 3108 1511 1048 [(C[H.sub.3]COO).sub.2]] [Cu[(DNPH).sub.2] 3476,3091 1512 1050 [(C[H.sub.3]COO).sub.2]] Ligand/Complex vas(COO) vs(COO) DNPH (Ligand) - - [Zn[(DNPH).sub.2] 1434 1350 [(C[H.sub.3]COO).sub.2]] [Co[(DNPH).sub.2] 1424 1312 [(C[H.sub.3]COO).sub.2]] [Ni[(DNPH).sub.2] 1424 1311 [(C[H.sub.3]COO).sub.2]] [Cu[(DNPH).sub.2] 1427 1312 [(C[H.sub.3]COO).sub.2]]