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The synthesis, characterization and antimicrobial activity of Cu(II) complexes of some p-substituted aniline Schiff base ligands have been carried out. The Schiff bases were obtained from salicylaldehyde and o-vanillin. The Cu(II) complexes have been characterized by elemental analysis, conductivity measurement, infrared and electronic spectral data. The complexes were obtained either as metal chelates [Cu(L)2] or Schiff base adducts (CuCl2.2LH).xH2O. The metal chelates were non-electrolytes while the Schiff base adducts exhibited 1:1 or 2:1 electrolytes in methanol. The Cu(II) complexes exhibited slight antimicrobial activity against Escherichia coli ATCC® 8739™*, Staphylococcus aureus subsp. aureus ATCC® 6538™*, Bacillus subtilis subsp. spizizenii ATCC® 6633™* and Candida albicans ATCC® 2091™*. The complexes exhibited significant antifungal activity. KEY WORDS: Metal Chelates, Schiff bases, Adducts, Cu(II) complexes, Salicylaldimines Bull. Chem. Soc. Ethiop. 2021, 35(1), 33-42. DOI: https://dx.doi.org/10.4314/bcse.v35i1.3

Herein, we report the encapsulation and release of antimalarial drug quinine (QN) using three nanocarriers, including MCM-41 (1), and its 3-aminopropyl silane (aMCM-41 (2)) and 3-phenylpropyl silane (pMCM-41 (3)) surface functionalized derivatives. The pH and thermal optimization effects on QN adsorption and release from 1, 2 and 3 were investigated.

Biometal coordination bearing active donor atoms of medicinal plant extracts or herbal isolates (phytochemicals) in the recent approach of biomedical sciences is a new and advanced chemotherapeutics for combating antibiotics resistance. Stereochemistry of central metal ions around active plant molecules can give rise to robust solid state 3D metal complexes of antibiotics aiding better biological performance/affinity without any side effect compared with the parent biomolecules (organic ligands). This review therefore focuses on the applications of medicinal plant extracts as antibiotics. Structural systems of metal complexes of flavonoids, curcumins, alkaloids, carotenoids and coumarins from aloe vera, acalypha and henna leaf (AAH) are also described with a view to achieving the rationale for functional bioactive antibiotic drugs

Antimicrobial resistance (AMR) endangers the effective management of an increasing range of bacterial and fungal infections, alternative antimicrobial drugs are thus, expedient. In this study, Quaternary Trimethyl Chitosan (QTMC) was prepared by improved two step reductive methylation of Chitosan (CTS) employed as a capping agent for the synthesis of silver nanoparticles (QTMC-AgNPs). The hydrophilic QTMC and QTMC-AgNPs were characterized using various analytical and spectroscopic techniques. The Proton Nuclear Magnetic Resonance ( 1 HNMR) was used to determine the degree of quaternization (DQ) and degree of dimethylation (DT) of QTMC as 63.33 and 11.75 % respectively. The Ultraviolet-Visible (Uv-Vis), Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), X-ray Diffraction (XRD), Energy Dispersive X-ray (EDS) and X-ray Photoelectron (XPS) Spectroscopic results evidently indicated high degree of quaternization of CTS and configured QTMC-AgNPs. Thermogravimetric Analysis/Derivative Thermogravimetry (TGA/DTG) were used to study the decomposition process of QTMC and QTMC-AgNPs. The surface morphological difference of QTMC and QTMC-AgNPs was explored via Scanning Electron and High-Resolution Transmission Electron Microscopies (SEM and HR-TEM) whereas particle size distribution was analyzed using Dynamic Light Scattering. Furthermore, HR-TEM indicated QTMC stabilized AgNPs with average nanoparticulate size of 10 nm while DLS revealed 12.5 nm. This well-tailored QTMC-AgNPs exhibited strong antibacterial and antifungal activities against the tested bacteria and fungi infections.

Chitosan functionalized methyl orange (CFMO) nanocomposites of iron (CFMO-FeNPs) and copper (CFMO-CuNPs) were successfully prepared as simple and selective chemosensors for CN − and AsO 4 3 − anions in aqueous solution. The initially synthesized chitosan-dye-metal complexes (CFMO-Fe(II) and CFMO-Cu(II) were nanosized via chemical reduction methods. The imminent IR bands shift especially of ν C − C aromatic rings and CFMO azo bond suggest the formation of cyclometaled metal-azo complexes. Plasmon resonance bands at 473 and 469 nm were observed for the nanocomposites of Fe and Cu respectively indicating successful nano reduction of the metal ions. The semi-crystalline nature of the composites was revealed from the XRD analysis which ranged from broad to sharp peaks. More so, the varying linear orientation to monodispersed distribution of the nanoparticles on the biopolymeric substrate was displayed in the SEM micrographs. The electrostatic attraction between the metal induced cationic N,N-dimethylbenzenamine end and the test anions provides remarkable colorimetric responses with high selectivity for the test anions in an aqueous solution with LOD of 1.0 and 2.0 μ g/mL for CN − and AsO 4 3 − respectively. Consequently, the obvious selective color changes can be exploited for real time and on site applications.

The synthesis and characterization of novel transition Metal (Cu(II), Co(II), Ni(II) and Zn (II)) complexes of 2,5-diamino-2-(difluoromethyl) pentanoic acid hydrochloride hydrate (DPH) have been described. The ligand and metal complexes were characterized by Melting point, Conductivity measurement, Elemental analysis, Fourier Transform infrared (FTIR) spectroscopy, Electronic spectroscopy, Magnetic susceptibility measurement and Electrospray Ionization Mass Spectrometry (ESI-MS). The FTIR spectral data suggests that the ligand behaves as a bidentate ligand coordinates to the metal ions through an oxygen atom of the carboxylate and a nitrogen atom of amino group. The terminal amino group of the ligand is protonated to form NH3+ while the carboxylic moiety is deprotonated forming zwitterionic complexes. Electronic spectral and magnetic studies data suggest that the complexes of Cu(II), Co(II) and Ni(II) have octahedral geometry around metal ions while tetrahedral geometry was proposed Zn (II) ion. In vitro anti-bacterial activities of the ligand and metal complexes were carried out using agar diffusion method against two gram-positive bacteria (Staphylococcus aureus, Bacillus substilis) and two gram-negative bacteria (Escherichia coli, Klebsiella pneumonia). The results obtained revealed that the metal complexes showed enhanced antibacterial activities against the four micro-organisms with lowest minimum inhibitory concentration (MIC) when compared to parent compound. DOI: http://dx.doi.org/10.17807/orbital.v10i5.962

The use of nanocarriers in drug delivery is a breakeven research and has received a clarion call in biomedicine globally. Herein, two newly nano-biomaterials: MCM-41 encapsulated quinine (MCM-41 ⊃ QN) (1) and 3-phenylpropyl silane functionalized MCM-41 loaded QN (pMCM-41 ⊃ QN) (2) were synthesized and well characterized. 1 and 2 along with our two already reported nano-antimalarial drugs (MCM-41 ⊃ ATS) (3) and 3-aminopropyl silane functionalized MCM-41 contained ATS (aMCM-41 ⊃ ATS) (4) were screened in vitro for their activity against P. falciparium W2 strain, cytotoxicity against BGM cells and in vivo for their activity against Plasmodium bergheiNK65. 1 has the highest antimalarial activity in vivo against P. berghei NK65, (ED50: 1) stands very useful and effective in delivering the drug to the target cells compared to other delivery systems and therefore, this encapsulated drug may be considered for rational drug design.

Chitosan was used as a stabilizer to synthesize chitosan cobalt(II) [Chit–Co(II)] and its zerovalentcobalt nanobiocomposite via chemical reduction. The complex and Chit–ZVCo were used to polymerize vinylacetate in aqueous Na2SO3. The Chit–Co(II) and Chit–ZVCo were characterized by spectroscopic (FT-IR and UV–Visible), XRD and SEM techniques. Application of these biomaterials for the polymerization of VAc afforded polyvinylacetate with improved yield. Comparing the reactivity of Chit–Co(II) and Chit–ZVCo, it was evident that Chit–ZVCo performed as better heterogeneous catalyst based on the synergic effect of interaction of cobalt nanoparticles and chitosan at the nanometric scale.

A range of d-block transition metals complexes of mixed amodiaquine and citric acid have been synthesized and characterised using microanalytical technique, elemental analysis, FT-IR spectroscopy and magnetic measurement. The results of the analytical and spectroscopic data revealed that both amodiaquine and citric acid acted as bidentate ligands in their mode of coordination with the metal ions.The citric acid bound through the carbonyl (C=O) and hydroxyl groups to the metal ions while, amodiaquine coordinated through the nitrogen atom of the amine and oxygen donor atom of hydroxyl group; resulted in structures with octahedral geometry. Percentage composition and magnetic Bohr moment data indicated that all metal complexes were paramagnetic. Molar conductance measurement indicates that the complexes are non-electrolytes in nature. The antimicrobial activity of the ligands and their mixed complexes was carried out against g(+)Pseudomonas aeruginosa, g(+) E. coli , g(+) Klebsiella pneumonia , g(+) Staphylococcus aureus and g(+)Candida using Muller Hinton diffusion method. The citric acid and amodiaquine result showed low or moderate value from (0.6-0.8) for all the metal complexes with the exception of the Cu (II) complex having inhibitory zones ranging from 1-0-1.3, 0.7-0.9 at 200 ppm respectively. Moreover, the free ligands were found being less active compared with their mixed complexes. Keywords: Citric acid, Amodiaquine, Complexes, Antimicrobial studies

An antimalarial drug artesunate (ATS) was encapsulated in both functionalized MCM-41 and ordinary MCM-41 with an excellent loading capacity and sustained release behavior for possible biomedical applications.

Four d-orbital metal complexes with mixed ligands derived from 8-hydroxyquinoline (HQ) and amino acids (AA): l -alanine and methionine have been synthesized through a mild reflux in alkaline solution and characterized by elemental analyses, infrared, electronic transition, and temperature dependant magnetic susceptibility. The IR spectroscopy revealed that iron and copper ions coordinated through carbonyl (C O), hydroxyl group (O H) of the amino acids, N-pyridine ring of hydroxyquinoline. The elemental analysis measurement with other obtained data suggested an octahedral geometry for the iron(III) complexes and tetrahedral geometry for the copper(II) complexes. From the molar magnetic susceptibility measurement, the iron(III) system ( S = 5/2) d 5 (non-degenerate 6 A 1 ) with χ m T = 0.38 cm 3 Kmol −1 showed an antiferromagnetic while Cu 2+ ions system ( S = ½) ( 2 T 2g ) has χ m T = 4.77 cm 3 Kmol −1 described as paramagnetic behaviour. In vitro antimicrobial investigations of the metal complexes against standard bacteria species gave significant inhibition with, copper complex showing highest inhibitions against Pseudomonas aeruginosa (ATCC27853) of 43 mm at 10 μg/ml signalling its potential as pharmaceutical or chemotherapeutic agents.

Temperature dependent dielectric constant changes for salicylideneaniline (SA) were observed before and after light irradiation. The dielectric constant for a non-illuminated sample is higher than that for an illuminated one. It was considered that this fascinating observation might reflect dynamic chromophoric structural changes within the tautomers of SA.

Self-assembled hybrid supramolecular architectures formed between amphiphilic anions and long alkylated cationic cobalt(II) complexes of type [Co(Cn-terpy)2](C12-Glu)2 (n = 15–20) have been synthesized and characterized by TEM, PXRD and magnetic susceptibility measurements. The hybrids display wire or rolled sheet supramolecular arrangements with odd and even alkyl chain dependence, with the cobalt(II) centres exhibiting gradual spin-crossover behaviours.

Iron(III) compounds with long alkyl chains, [Fe(Cn-pap)2]ClO4 (Cn-pap: alkoxy-2-(2-pyridylmethyleneamino)phenol, n = 8 (1), 10 (2), 12 (3), 14 (4), 16 (5)) have been synthesized. The compounds were characterized by single crystal X-ray structure analysis and temperature dependent magnetic susceptibility in order to research the relationship between magnetic properties and the presence of long alkyl chains in soft molecules of the present type. The compounds 1, 2, 3 and 4 are in the high-spin (HS) state over the temperature range of 5 to 400 K. On the other hand, compound 5 is low-spin (LS) showing that the difference in magnetic properties depends on the length of the alkyl chain in the respective compounds.

Complexes of Fe(III) and Mn(II) with bithiourea were synthesized and characterised by elemental analysis, magnetic measurements, infrared spectroscopy, UV/visible, thin layer chromatography, and conductance measurements. The IR showed that the ligand coordinates through C=S and N–H donor atoms and hence a bidentate. The antimicrobial activity of the complexes formed has been tested and compared with bithiourea at different concentrations in order to obtain some quantitative information about their biological activity towards microorganism. Metal complexes were found to show better activities as compared to the ligand and the standard drug used as control.In vivotoxicological studies showed that the complexes were not toxic at the dosage level administered.

Zerovalent cobalt 2,6-Pyridinedicarboxylic acid crosslinked chitosan (ZVCo-PDCA-CHIT) nanocomposite, which was obtained by chemical reduction of cobalt (II) ion chelated nanocomposite with NaBH4, was tested for bromate reduction in water. 2,6-pyridinedicarboxylic acid (PDCA) was used for intramolecular crosslinking of the chitosan linear chains. The products were characterized by FT-IR, XRD and SEM. The FT-IR analyses revealed the presence of coordinating –NH2 and –OH functional groups in chitosan while crosslinked chitosan showed –COOH absorption peaks. The XRD spectrum revealed a typical fingerprint of semi-crystalline chitosan which disappeared in crosslinked chitosan due to disruption of the interpolymer bonds. SEM image revealed a smooth surface for the Chitosan while large pores were observed for the PDCAcrosslinked Chitosan (PDCA-CHIT). ZVCo-PDCA-CHIT nanocomposite showed significant morphological changes with the surface structure being smooth with the disappearance of the holes observed in the cr...

Metal coordination of bioorganic compounds from both natural and synthetic products is not only gaining recognition in drug design and medicinal inorganic chemistry research, also they are being considered in the improvement of the bioactivity of drugs. What is done in this paper is a review of recent advances in the study of coordination-driven drug delivery, i.e., metal-based drugs (MBDs). The role of some late first row transition metal ions namely Fe, Cu and Zn in the biological activities of metallodrugs such as antimalarials and antimicrobials are highlighted. It was revealed that the interaction between these bio-essential transition metal ions and the organic drugs could enhance the diagnostic and therapeutic potentials of such formed drugs. This is because such interactions were proved to have improved the stability, bioavailability and cell delivery functions of the metallodrugs. Emphasizing on the challenge of metal ions toxicity, the researchers concluded on the need for the development of MBDs to combat drug resistant parasites without causing injury to normal cells. This would be of significance in addressing the concern World Health Organisation of ameliorating the increasing mortality rate in developing countries.

Background : Metal ions play a vital role in the design of more biologically active drugs. Aim : The paper reviewed the antimicrobial, toxicological and DNA cleavage studies of some synthesized metal complexes of fluoroquinolone antibiotics. Materials and Methods : Literature searches were done using scientific databases. Results : Computer search was used to reveal elevant studies. Spectrophotometric and X-ray analyses of the metal complexes have revealed the bi-dentate coordination of fluoroquinolone ligand to the metal through the ring carbonyl and one of the carboxylic oxygen atoms. Most of the metal complexes showed comparable activities and in some cases greater activity against tested organisms. On the toxicological tests carried out, some of the metal complexes had less adverse effect on the body tissues studied compared to the parent drugs. The DNA cleavage studies revealed the possibility of the metal-fluoroquinolone complexes destabilizing linear double stranded DNA. Conclusion : The reviewed metal complexes of fluoroquinolones have the potential of being used as drugs. Keywords : Ciprofloxacin, fluoroquinolone, metal, antimicrobial, toxicology

Antibacterial behavior of chitosan-bivalent metal chelates (Co and Ni) was investigated in vitro against standard bacteria, Staphylococcus aureus ATCC 4533, S. faecalis ATCC 8043 and Escherichia coli ATCC 25923. The chitosan-metal chelates were prepared by varying the molar ratio of metal ions to a fixed amount of chitosan. The metal ion contents, structural properties and morphology of the chelates were respectively determined using ICP-OES, FT-IR and SEM. All the chitosan-metal chelates showed wide spectrum of effective antibacterial activities better than free chitosan and the individual metal ions. The results indicated that inhibitory effects of the chelates were dependent not only on the property of the coordinated metal ion, but also on the molar ratio of the metal ion. Consequently, the ideal inhibitory effects could be obtained with metal ion of high charge intensity and when the molar ratio of chitosan to metal was above 1:1. These chelates are promising materials for novel antibacterial agents.

Some transition metal complexes of nicotinamide have been prepared and characterized using melting point, conductivity measurement, infrared, electronic, HNMR and atomic absorption spectroscopic methods. . The antibacterial and antifungal studies of the metal complexes and the ligand have been evaluated against Escherichia coli , Staphylococcus and Bacillus subtilis , Aspergillus flavus, Aspergillus niger and penicillum species. It was found that nicotinamide formed stable metal complexes with these metal ions. The analysis of the spectroscopic data shows that nicotinamide act as monodentate, coordinating through the nitrogen atom of the pyridine ring. All the complexes exhibit 4- coordinate geometry. The results of the antimicrobial studies showed that the metal complexes have higher inhibitory activity than the original nicotinamide against the tested bacteria and fungi species. Keywords : Synthesis, Metal complexes, Nicotinamide, Antibacterial, Antifungal

Chemical reduction of nitrate using metal nanoparticles has received increasing interest due to over-dependence on groundwater and consequence health hazard of the nitrate ion. One major drawback of this technique is the agglomeration of nanoparticles leading to the formation of large flocs. A low cost biopolymeric material, poly [beta-(1-->4)-2-amino-2-deoxy-D-glucopyranose] (beta-PADG) obtained from deacetylated chitin was used as stabilizer to synthesize zero valent nickel (ZVNi) nanoparticles. The beta-PADG-ZVNi nanocomposite was characterized using infra red (IR), UV-Vis spectrophotometric techniques and Scanning Electron Microscope (SEM). The morphology of the composite showed that beta-PADG stabilized-ZVNi nanoparticles were present as discrete particles. The mean particle size was estimated to be (7.76 +/- 2.98) nm and surface area of 87.10 m2/g. The stabilized-ZVNi nanoparticles exhibited markedly greater reactivity for reduction of nitrate in water with 100% conversion within-2 hr contact owing to less agglomeration. Varying the beta-PADG-to-ZVNi ratio and the ZVNi-to-nitrate molar ratio generally led to a faster nitrate reduction. About 3.4-fold difference in the specific reaction rate constant suggests that the application of the beta-PADG-stabilizer not only increased the specific surface area of the resultant nanoparticles, but also greatly enhanced the surface reactivity of the nanoparticles per unit area.

The present study aimed at synthesizing copper(II) and zinc(II) complexes of mixed ascorbic acid and nicotinamide and physiochemically characterize by solubility test, melting point, conductivity test, infrared, electronic and proton nuclear magnetic resonance techniques. The result of the physiochemical studies indicated 1:1 stoichiometry and were supported by the spectroscopic data. The antimicrobial activities of the mixed complexes were carried out against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Penicillum, spp Aspergillus flavus and Aspergillus niger. The result of the infrared data showed that ascorbic acid coordinates through the oxygen of the carbonyl group and that of enolic C-2 hydroxyl group, while nicotinamide coordinates through the nitrogen atom of the pyridine ring. The result of the antimicrobial studies showed that the mixed complexes have higher inhibitory activity than the original ligands against the tested bacteria and fungi species. KEY WORDS : Ascorbic acid, Nicotinamide, Synthesis, Antimicrobial, Complexes.

A series of chromium(iii) complexes ligated by N^N^N tridentate 2-quinoxalinyl-6-iminopyridine were synthesized and characterized by elemental analysis and infrared spectroscopy. Single-crystal X-ray diffraction analysis for the structure of complex C3 reveals a distorted octahedral geometry. When methylaluminoxane was employed as the co-catalyst, the chromium complexes showed high activities for ethylene oligomerization and polymerization. The distribution of oligomers obtained followed Schulz–Flory rules with high selectivity for α-olefins. Both steric and electronic effects of coordinated ligands affected the catalytic activities as well as the properties of the catalytic products. The parameters of the reaction conditions were also investigated to explore the optimum catalytic potentials of these complexes.