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Search Results: 1 - 10 of 148486 matches for " Peter T. Ndifon "
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A Chiral Three Dimensional Potassium(I)/Strontium(II)/Chromium(III) Oxalato-Bridged Coordination Polymer: Synthesis, Characterization and Thermal Analysis  [PDF]
Justin Nenwa, Issoufou Kaboré, Yves A. Mbiangué, Patrick L. Djonwouo, Peter T. Ndifon
Crystal Structure Theory and Applications (CSTA) , 2014, DOI: 10.4236/csta.2014.34008
Abstract: A new compound of general formula {[(H2O)2K(μ-H2O)Sr]@[Cr(C2O4)3]}n (1) has been synthesized in water and characterized by elemental and thermal analyses, EDX, IR and UV-Vis spectroscopies and by single crystal X-ray structure determination. Compound 1 crystallizes in the chiral space group Fdd2 of orthorhombic system with a = 14.110 (4) ?, b = 36.074 (11)?, c =11.034 (3)? and Z = 16. Compound 1 is a coordination polymer in which the three-dimensional lattice framework is realized by the interconnectivity between K+ cations, Sr2+ cations, aqua ligands and [Cr(C2O4)3]3 complex anions. The asymmetric unit of 1 consists of one cationic motif formally written [(H2O)2K(μ-H2O)Sr]3+ and one anionic entity, [Cr(C2O4)3]3. The K+ and Sr2+ ions in the cationic motif are both eight-coordinate while the Cr3+ ions in the anionic complex are six-coordinate in a distorted octahedral geometry. Coulombic interactions between the ionic motifs and the three-dimensional H-bonding involving aqua ligands help to consolidate the bulk structure. Thermogra-vimetric analysis (TGA) shows that compound 1 is stable to heat up to ca. 80.
Synthesis and Characterisation of a Biolubricant from Cameroon Palm Kernel Seed Oil Using a Locally Produced Base Catalyst from Plantain Peelings  [PDF]
Michael Bong Alang, Maurice Kor Ndikontar, Yahaya Muhammad Sani, Peter T. Ndifon
Green and Sustainable Chemistry (GSC) , 2018, DOI: 10.4236/gsc.2018.83018
Abstract: Biolubricant was synthesized from Cameroon palm kernel oil (PKO) by double transesterification, producing methyl esters in the first stage which were then transesterified with trimethylolpropane (TMP) to give the PKO biolubricant in the presence of a base catalyst obtained from plantain peelings (municipal waste). The yields from both catalysts were significantly similar (48% for the locally produced and 51% for the conventional) showing that the locally produced catalyst could be valorized. The synthesized biolubricant was characterized by measuring its physical and chemical properties. The specific gravity of 1.2, ASTM color of 1.5, cloud point of 0°C, pour point of -9°C, viscosities at 40°C of 509.80 cSt and at 100°C of 30.80 cSt, viscosity index of 120, flash point greater than 210°C and a fire point greater than 220°C were obtained. This synthesized biolubricant was found to be comparable to commercial T-46 petroleum lubricant sample produced industrially from mineral sources. We have therefore used local materials to produce a biolubricant using a cheap base catalyst produced from municipal waste.
Synthesis, Characterization and Antimicrobial Studies of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of (E)-2-(4-Dimethylbenzydimino)-Glycylglycine, (Glygly-DAB) a Schiff Base Derived from 4-Dimethylaminobenzaldehyde and Glycylglycine  [PDF]
Maurice Kuate, Mariam Asseng Conde, Katia N. Nchimi, Awawou G. Paboudam, Sally-Judith E. Ntum, Peter T. Ndifon
International Journal of Organic Chemistry (IJOC) , 2018, DOI: 10.4236/ijoc.2018.83022
Abstract: A tridentate Schiff base ligand, (E)-2-(4-dimethylbenzydimino) glycylglycine (glygly-DAB), derived from the condensation of 4-Dimethylaminobenzaldehyde (DAB) and glycylglycine (glygly) together with its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized and characterized using various physico-chemical methods including C,H,N elemental analysis, melting point determination, molar conductivity measurement, IR, 1H NMR and UV-Vis. The ligand and metal complexes were screened in vitro for antimicrobial and antifungal activities on four bacterial strains (Staphylococcus aureus, Escherichia coli, Salmonella thyphi and Pseudomonas aeruginosa) and two fungal strains (Candida albicans and Cryptococcus neoformans). glygly-DAB showed remarkable antifungal activities on all the fungal strains and antibacterial activities on one bacterial strain.
Synthesis and characterisation of some metal complexes of hybrid phosphorus-nitrogenligands: the crystal structure of 1-(diphenylphosphino)-2-(2-pyridyl)ethane cobalt(II) chloride
Peter T. Ndifon, Moise O. Agwara, Yoshihito Hayashi, Akira Uehara
Bulletin of the Chemical Society of Ethiopia , 2008,
Abstract: Some iron(II), cobalt(II) and copper(II) complexes of the hybrid ligand 1-(diphenylphosphino)-2-(2-pyridyl)ethane (dppe) and diphenyl-2-pyridylphosphine (dppp) have been synthesised and characterised. Analyses suggest tetrahedral structures in which the metal atoms are bonded to two chlorine atoms and to both phosphorus and nitrogen atoms for 1-(diphenylphosphino)-2-(2-pyridyl)ethane on one hand and on the other hand, bonding is through the nitrogen atoms of two molecules of diphenyl-2-pyridylphosphine, which acts as a monodentate ligand. The crystal structure of 1-(diphenylphosphino)-2-(2-pyridyl)ethane cobalt(II) chloride shows a pseudo-tetrahedral structure in which the aminophosphine is bonded to the cobalt centre through both the phosphorus and nitrogen atoms, forming a 6-membered ring. KEY WORDS: Aminophosphines, Metal complexes, Cobalt(II) complex, Crystal structure Bull. Chem. Soc. Ethiop. 2008, 22(2), 253-260.
Synthesis and characterisation of some metal complexes of hybrid phosphorus-nitrogen ligands: the crystal structure of 1-(diphenylphosphino)-2-(2-pyridyl)ethane cobalt(II) chloride
Peter T. Ndifon,Moise O. Agwara,Yoshihito Hayashi,Akira Uehara
Bulletin of the Chemical Society of Ethiopia , 2008,
Abstract: Some iron(II), cobalt(II) and copper(II) complexes of the hybrid ligand 1-(diphenylphosphino)-2-(2-pyridyl)ethane (dppe) and diphenyl-2-pyridylphosphine (dppp) have been synthesised and characterised. Analyses suggest tetrahedral structures in which the metal atoms are bonded to two chlorine atoms and to both phosphorus and nitrogen atoms for 1-(diphenylphosphino)-2-(2-pyridyl)ethane on one hand and on the other hand, bonding is through the nitrogen atoms of two molecules of diphenyl-2-pyridylphosphine, which acts as a monodentate ligand. The crystal structure of 1-(diphenylphosphino)-2-(2-pyridyl)ethane cobalt(II) chloride shows a pseudo-tetrahedral structure in which the aminophosphine is bonded to the cobalt centre through both the phosphorus and nitrogen atoms, forming a 6-membered ring.
A Novel Mixed Ligand Dinuclear Complex of Cobalt (II): Synthesis, Characterization and Magnetic Studies  [PDF]
Emmanuel N. Nfor, Luke L. Keenan, Justin Nenwa, Peter T. Ndifon, Romanus N. Njong, Christelle N. T. Dzesse, Offiong E. Offiong
Crystal Structure Theory and Applications (CSTA) , 2014, DOI: 10.4236/csta.2014.31003
Abstract:

A novel dinuclear complex [Co2(atr)3(mal)2(H2O)2]·4H2O(1) (atr = 4-amino-1,2,4-triazole and mal = malonic acid) containing mixed N and O-donor atoms has been prepared and structurally characterized. The structure is made up of the symmetrically 1, 2, 4-triazole bridged [Co2(atr)3(mal)2(H2O)2] moiety and four lattice water molecules. The single crystal X-ray analysis reveals that the complex has a distorted octahedral structure. Magnetic susceptibility measurements reveals that antiferromagnetic interactions exists between the high spin Co(II) ions within the dinuclear unit.

Synthesis and Crystal Structure of N-(2-Pyridylmethyl)-L-Alanine) Isothiocyanate Cobalt(III)  [PDF]
Sally-Judith E. Ntum, Awawou G Paboudam, Asseng M. Conde, Linda D. Nyamen, Aminou Mohamadou, James Raftery, Peter T. Ndifon
Crystal Structure Theory and Applications (CSTA) , 2017, DOI: 10.4236/csta.2017.63004
Abstract: The title compound, [N-(2-pyridylmethyl)-(L)-alanine]Co(III) thiocyanate (1) was obtained from the reaction of Co(OOCH3)2·H2O with the tridentate reduced Schiff base ligand, N-(2-pyridylmethyl)-(L)-alanine (L) and NH4SCN and characterized by elemental analysis, IR, UV-visible, TGA and single- crystal X-ray diffraction. Structural and spectroscopic analyses reveal [Co(L)2)]SCN to be monomeric with Cobalt(III) adopting a pseudo-octahedral geometry, coordinating to two reduce Schiff base ligands. In the crystal lattice, the thiocyanate anion forms an intermolecular SCN···HNamine hydrogen bond, while adjacent monomers are linked by intermolecular Ocarboxyl···HNamine···H-bonds to form a supramolecular network. This work is therefore undertaken in an
Solution Studies on Co(II), Ni(II), Cu(II), and Zn(II) Complexes of Hexamethylenetetramine in Aqueous and Non-Aqueous Solvents
Awawou G. Paboudam,Christian Gérard,Aminou Mohamadou,Moise O. Agwara,Mariam A. Conde,Peter T. Ndifon
International Journal of Inorganic Chemistry , 2014, DOI: 10.1155/2014/397132
Abstract: Potentiometric studies in aqueous medium and spectrophotometric study in non-aqueous medium were used to understand the behavior of hexamethylenetetramine (HMTA) complexes. The protometric studies of HMTA enabled us to confirm that only one basic site of this ligand is protonated in acidic medium and this ligand is decomposed in acidic medium. In aqueous medium, only hexa-aqua complexes in which HMTA is present in the second coordination sphere forming H-bonds with hydrogen atoms of coordinated and uncoordinated water molecules are obtained. In non-aqueous solvents, HMTA coordinates to metal ions displaying diversity in the structures of the resulting complexes in which HMTA can either be monodentate, bridged bidentate, tridentate, or tetradentate. 1. Introduction Hexamethylenetetramine (HMTA) is a heterocyclic ligand with four nitrogen donor atoms, having three rings merged in a chair conformation as shown in Figure 1. Figure 1: Structure of hexamethylenetetramine. HMTA can therefore form various metal complexes possessing interesting structural features and applications [1–5]. Hexamethylenetetramine as a ligand can bind either in a monodentate manner to a metal [6, 7], acting as bridging ligand linking two, three, or four metals [8–11], or bind to metal-containing species through the formation of hydrogen bonding [5, 12–16]. The combination of both covalent and hydrogen bonding in certain complexes of hexamethylenetetramine leads to the formation of three-dimensional structures that easily decompose by thermal treatment to give thin films of metal oxides [15, 16]. The formation of covalently bonded and hydrogen-bonded compounds of hexamethylenetetramine is influenced by several factors such as the nature of the solvent, steric hindrance of the counter ion, and the pH of the solution [17]. When water is used as the solvent during synthesis, metal-aqua complexes are obtained which bind to HMTA through H-bonds, forming ionic species [18]. When non-aqueous solvents are used for synthesis, metal-HMTA covalent species are formed [10, 15]. Recently, we reported the isolation of metal-HMTA covalently bonded species isolated from ethanol [19]. Metal-H2O-HMTA ionic species involving H-bonds isolated from ethanol/water mixture have also been reported [5, 12–16, 20]. We report here the results of the study on the influence of solvent on the electronic and structural properties of metal-HMTA complexes in aqueous and non-aqueous solvents. 2. Experimental 2.1. Chemicals All solvents were purified by conventional procedures [21] and distilled prior to use. All the
Conservation of MAP kinase activity and MSP genes in parthenogenetic nematodes
Peter Heger, Michael Kroiher, Nsah Ndifon, Einhard Schierenberg
BMC Developmental Biology , 2010, DOI: 10.1186/1471-213x-10-51
Abstract: We investigated two key elements of oocyte-to-embryo transition, MSP expression and MAP kinase signaling, in two parthenogenetic nematodes and their close hermaphroditic relatives. While activated MAP kinase is present in all analysed nematodes irrespective of the reproductive mode, MSP expression differs. In contrast to hermaphroditic or bisexual species, we do not find MSP expression at the protein level in parthenogenetic nematodes. However, genomic sequence analysis indicates that functional MSP genes are present in several parthenogenetic species.We present three alternative interpretations to explain our findings. (1) MSP has lost its function as a trigger of MAP kinase activation and is not expressed in parthenogenetic nematodes. Activation of the MAP kinase pathway is achieved by another, unknown mechanism. Functional MSP genes are required for occasionally emerging males found in some parthenogenetic species. (2) Because of long-term disadvantages, parthenogenesis is of recent origin. MSP genes remained intact during this short intervall although they are useless. As in the first scenario, an unknown mechanism is responsible for MAP kinase activation. (3) The molecular machinery regulating oocyte-to-embryo transition in parthenogenetic nematodes is conserved with respect to C. elegans, thus requiring intact MSP genes. However, MSP expression has been shifted to non-sperm cells and is reduced below the detection limits, but is still sufficient to trigger MAP kinase activation and embryogenesis.Throughout the animal kingdom, female gametes interrupt their development during oogenesis at various stages of meiosis. In response to external stimuli, this arrest is released, and oocyte maturation can take place. Then oocytes resume meiotic divisions, ovulate and get competent for fertilisation.An important step during oocyte maturation of all animals is MAP kinase activation (reviewed in [1-3]). MAP kinases are ubiquitous serine-threonine protein kinases expressed
The Debris Flow of 1st August 2012 in Kakpenyi-Tinta (Akwaya Sub Division) Southwest Cameroon—I: Event Description, Causes and Impacts  [PDF]
Romaric Ntchantcho, Linus Nche Anye, Festus Tongwa Aka, Boniface Kankeu, Gaston Wung Buh, Peter Teke Ndifon, Joseph Metuk Nnange, Joseph Victor Hell
Open Journal of Geology (OJG) , 2017, DOI: 10.4236/ojg.2017.79089
Abstract: Compared to large-scale infrequent disasters like volcanic eruptions, earthquakes, and gas explosions from volcanic (maar) lakes, most small-scale everyday disasters (e.g., landslides and floods) are not well reported and documented in Cameroon, despite the fact that cumulatively, they cause the most casualties and distress to the people affected. This paper documents a debris flow that occurred on the 1st of August 2012 in Kakpenyi, a quarter found in Tinta, one of the villages of Akwaya Sub Division in Manyu Division of the Southwest Region of Cameroon. The event started from the western slope (06°14.350'N & 09°31.475'E) of a hogback in the settlement, and mobilized ca 3.47 × 106 m3 of material over a ca 1 km distance. The material was made up of a chaotic mix of mud, rock fragments, boulders, twigs, tree logs, trunks, and roots. Its distal part dammed river Kakpenyi forming a 10 m deep lake which eventually safely emptied itself. No casualties were recorded but 20 people got injured and 21 people lost farmland. The debris flow was not caused by earthquake shaking. Instead, inappropriate land use acted as a remote cause to predispose the steep slope, while heavy rainfall triggered the flow. Verbal reports talk of a similar event 40 years ago in the area. This shows that Kakpenyi is vulnerable to this kind of hazard, requiring that major infrastructural development projects like roads and bridges in the area be preceded by detailed hazard and vulnerability assessments.
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