Abstract

The condensation reaction of phenylhydrazine and dinitrophenylhydrazine with 4-acetyl and 4-benzoyl pyrazolone precipitated air-stable acetyldinitrophenylhydrazone Ampp-Dh, benzoylphenylhydrazone Bmpp-Ph and benzoyldinitrophenylhydrazone Bmpp-Dh in their keto imine form; a study inspired by the burning interest for the development of new bioactive materials with novel properties that may become alternative therapeutic agents. Elemental analysis, FTIR, 1H, and 13C NMR, and mass spectroscopy have been used to justify their proposed chemical structures, which were in agreement with the single crystal structure of Bmpp-Dh earlier reported according to X-ray crystallography. The single crystal structure of 4-acetyl-3-methyl-1-phenyl--pyrazoline-5-one phenylhydrazone Ampp-Ph, which crystallizes in a triclinic crystal system with a P-1 (No. 2) space group is presented. Octahedral Mn(II), Ni(II), Co(II), and Cu(II) complexes of these respective ligands with two molecules each of the bidentate Schiff base, coordinating to the metal ion through the azomethine nitrogen C=N and the keto oxygen C=O, which were afforded by the reaction of aqueous solutions of the corresponding metal salts with the ligands are also reported. Their identity and proposed structures were according to elemental analysis, FTIR spectroscopy, UV-VIS spectrophotometry (electronic spectra) and Bohr magnetic moments, as well as thermogravimetric analysis (TGA) results. A look at the antibacterial and antioxidant activities of synthesized compounds using the methods of the disc diffusion against some selected bacterial isolates and 1,1-diphenyl-2-picryl-hydrazil (DPPH) respectively, showed biological activities in relation to employed standard medicinal drugs.

Highlights

  • Schiff bases can be said to be one of the most researched group of chemical molecules by scientists, the reasons being their versatility, selectivity, sensitivity, stability, and ease of synthesis, just to mention but a few, which have resulted in their wide applications [1,2,3]

  • The prominent peaks at 100% observed in the mass spectra of acetyl-3-methyl-1-phenyl-2-pyrazolin-5-one dinitrophenylhydrazone (Ampp-Dh), benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one dinitrophenylhydrazone (Bmpp-Dh), and beenzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one phenylhydrazone (Bmpp-Ph) correspond to the molecular ion M+ at m/z 397, m/z 459, and m/z 369, respectively (Figure 7)

  • The ketone carbonyl ν(C=O) group was observed at 1498, 1501, and 1501 cm1 in Ampp-Dh, Bmpp-Dh, and Bmpp-Ph, respectively, which was absent in the FTIR spectra of the metal complexes by way of forming –C–O–M bonds, an evidence of the coordination of the metal ion through the oxygen of the carbonyl ketone [34]

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Summary

Introduction

Schiff bases can be said to be one of the most researched group of chemical molecules by scientists, the reasons being their versatility, selectivity, sensitivity, stability, and ease of synthesis, just to mention but a few, which have resulted in their wide applications [1,2,3]. TThhee ppeerrcceennttaaggee ccoommppoossiittiioonn ooff CCHHNN eelleemmeennttaall aannaallyyssiiss iinn AAmmpppp--DDhh,, BBmmpppp--DDhh,, BBmmpppp--PPhh aanndd tthheeiirrTmmheettpaallercccooemmntppallgeeexxeecssomffoopuuonnsddit,,iowwneeroreef CiinnHaaNggrreeeleeemmmeeennntttawwl iiattnhhacclyaasllccisuulliaantteeAddmvvpaaplluu-Deessh,((rrBeemffeeprr pttoo-Dtthh,eeBeemxxpppeeprr-iiPmmheeannnttaadll tssheececttiirioomnn))e..taOOl cccttoaamhheepddlrreaaxllesmmfoeettuaanll dcc,oowmmepprelleexixneessagoorffeettmhheeenbbtiiwddeeinnthttaacttaeelcSSucclhhaiitffeffdbbvaaassleeusseshh(aarvveeeferbbteeoeennthepprreooxpppooessreeimdd..enTTthhaeel scceoocmmtipponllee)xx. Two broad peaks resonating downfield at around 12.2 and 9.5 ppm integrating for approximately one proton each are assigned to the hydrogen atoms of the –NH and the C=NH azomethine group, respectively. Two broad peaks resonating downfield at around 12.2 and 9.5 ppm integrating for approximately one proton each are assigned to the hydrogen atoms of the –NH and the C=NH. NMR NMR ssppeeccttrruummooffBBmmpppp-D-Dhh; a; nadnd(I(II)I1)3C13NCMNRMsRpescpteructmruomf Bomf Bpmp-pPhp.-Ph. A signal due to pyrazolone methyl carbon resonates at 15.8 ppm in the Bmpp-Ph 13C NMR specAtrusimgnaanlddutheetroespoynraanzcoelosnigenamlsetahty1l6c8a.0rbpopnmremsoaynabtesaasstig1n5e.8d ptopmtheincathrbeonByml pcpar-bPohn1o3Cf thNeMR sppeycrtarzuomlonaenCd=tOh.eArdedsoitnioannaclley,stihgensailgsnatl a1t6186.05.5pppmmmisadyubeetoatshseiganzeodmetothtinhee ccaarrbboonnaytol mcaCrb=oNn[2o9f]the pyarnadzothloenpeyCra=zOol.oAneddmiteitohnyallclya,rbthoenssiiggnnaallartes1o6n5a.5tepdpamt 1i5s.d8 upepmto.the azomethine carbon atom C=N [29]. The molecular ions observed in the Schiff base ligands confirm the calculated theoretical molar mass plus a proton [M + H]+

Mass Spectroscopy
Infrared Spectroscopy
UV-VIS Spectroscopy and Magnetic Moments
Synthesis of Phenylhydrazones
Synthesis of Phenylhydrazones Metal Complexes
Antibacterial Studies
Conclusions
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