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Papers by Richard Mampa

Research paper thumbnail of Decarbonylated bis-phosphine complexes bearing a Fe-Sn bond: NMR spectroscopy, X-ray structures, hirshfeld surface analysis, and DFT calculations

Journal of Molecular Structure

Research paper thumbnail of CCDC 1533685: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973685: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973681: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973679: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973678: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973677: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973676: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973675: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1906917: Experimental Crystal Structure Determination

Research paper thumbnail of Synthesis and spectroscopic studies of oximes derived from 2-aryl-1,2,3,4-tetrahydro-1,4-benzoheterazepin-5(4H)-ones

The synthesis and spectroscopic studies ofnovel 2-aryl-1,4-benzoheterazepin-5(4H)-ones with poten... more The synthesis and spectroscopic studies ofnovel 2-aryl-1,4-benzoheterazepin-5(4H)-ones with potential biological activity are discussed. A combination of NMR, IR and mass spectroscopic techniques is used to characterize the prepared compounds.

Research paper thumbnail of Synthesis, in vitro cytotoxic, anti-Mycobacterium tuberculosis and molecular docking studies of 4-pyridylamino- and 4-(ethynylpyridine)quinazolines

Journal of Molecular Structure, 2021

Abstract A series of 4-(pyridylamino)- and 4-(ethynylpyridine)quinazolines were successfully prep... more Abstract A series of 4-(pyridylamino)- and 4-(ethynylpyridine)quinazolines were successfully prepared via Sonogashira cross-coupling and dechloroamination reactions on the C(4)-Cl position of the requisite 2-(p-phenyl)-4-chloroquinazolines. The prepared compounds were characterized by means of 1H- and 13C-NMR, FT-IR and mass spectrometry techniques. The structure of 2-(4-chlorophenyl)-4-(2-(pyridin-4-yl) ethynyl) quinazoline from the 4-(ethynylpyridine) series was confirmed by single crystal X-ray analysis which indicates monoclinic crystal system and P21/c space group. Compounds from the 4-chloro-, 4-(pyridylamino)- and 4-(ethynylpyridine)-quinazoline series were evaluated for anti-Mycobacterium tuberculosis (Mtb) properties in vitro employing rifampicin as a reference drug. The results from the Alamar Blue assay (Mtb H37Rv strain) revealed promising MIC90 ranging from 125 µM. The cytotoxicity of the synthesised compounds was tested against the Raw 264.7 microphage cell line at a maximum concentration of 50 µM. The possible mode of interaction against the Mtb was theoretically explained through molecular 3ZXR protein and the more prominent hydrogen bond is observed between the nitrogen of the pyridine ring moiety of the 5 and 6 series with OH group of SER280. Also, a metal coordination between the methoxy benzene moiety of compound 6e and Mg2+ is also observed, explaining the SAR of these compounds to MtGS.

Research paper thumbnail of Sequential Extraction and Risk Assessment of Potentially Toxic Elements in River Sediments

Minerals, 2021

In this study, the sequential extraction method was applied to extract selected potentially toxic... more In this study, the sequential extraction method was applied to extract selected potentially toxic elements (PTEs) (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in river sediments collected from the Blood River situated in Seshego area, Limpopo Province, South Africa. The study aimed to assess a possible trend of mobilisation of these elements from sediment to water. The accuracy of the sequential extraction method was confirmed by analysing sediment-certified reference material, and quantitative percentage recoveries ranging from 86 to 119%, 81 to 111% and 77 to 119% were achieved for exchangeable, reducible and oxidisable fractions, respectively. The potential risk of the PTEs in sediments was evaluated. The calculated values of contamination factor (CF) as well as risk assessment code (RAC) for Cd, Cu, Ni and Pb revealed the mobility of these elements. The PTEs in river sediments are at a high toxicity-risk level and could therefore cause a threat to organisms dwelling in sediments and humans v...

Research paper thumbnail of Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State

Crystals, 2019

The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in ... more The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated...

Research paper thumbnail of Reactions and effect of N-sulfonylpyrrole yielding metal complexes: Crystal structural studies

Research paper thumbnail of Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides

Molecules (Basel, Switzerland), Jan 4, 2017

The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characte... more The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar-NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor si...

Research paper thumbnail of Synthesis, reactions and multinuclear NMR spectroscopic studies of organo bimetallic and trimetallic compounds

Research paper thumbnail of Correction: A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines

Organic & biomolecular chemistry, Jan 19, 2016

Correction for 'A convenient domino Ferrier rearrangement-intramolecular cyclization for the ... more Correction for 'A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines' by Paseka T. Moshapo et al., Org. Biomol. Chem., 2016, DOI: 10.1039/c5ob02536b.

Research paper thumbnail of A Convenient Domino Ferrier Rearrangement-Intramolecular Cyclization for the Synthesis of Novel Benzopyran-fused Pyranoquinolines

Org. Biomol. Chem., 2016

Lewis acid-mediated three component coupling of salicyladehydes, anilines and gylcals provided no... more Lewis acid-mediated three component coupling of salicyladehydes, anilines and gylcals provided novel benzopyran-fused pyranoquinolines stereoselectively, in moderate to high yields.

Research paper thumbnail of X-ray and NMR spectropscopic studies of selected heterocyclic compounds of phosphorus and nitrogen

Research paper thumbnail of Decarbonylated bis-phosphine complexes bearing a Fe-Sn bond: NMR spectroscopy, X-ray structures, hirshfeld surface analysis, and DFT calculations

Journal of Molecular Structure

Research paper thumbnail of CCDC 1533685: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973685: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973681: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973679: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973678: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973677: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973676: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 973675: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1906917: Experimental Crystal Structure Determination

Research paper thumbnail of Synthesis and spectroscopic studies of oximes derived from 2-aryl-1,2,3,4-tetrahydro-1,4-benzoheterazepin-5(4H)-ones

The synthesis and spectroscopic studies ofnovel 2-aryl-1,4-benzoheterazepin-5(4H)-ones with poten... more The synthesis and spectroscopic studies ofnovel 2-aryl-1,4-benzoheterazepin-5(4H)-ones with potential biological activity are discussed. A combination of NMR, IR and mass spectroscopic techniques is used to characterize the prepared compounds.

Research paper thumbnail of Synthesis, in vitro cytotoxic, anti-Mycobacterium tuberculosis and molecular docking studies of 4-pyridylamino- and 4-(ethynylpyridine)quinazolines

Journal of Molecular Structure, 2021

Abstract A series of 4-(pyridylamino)- and 4-(ethynylpyridine)quinazolines were successfully prep... more Abstract A series of 4-(pyridylamino)- and 4-(ethynylpyridine)quinazolines were successfully prepared via Sonogashira cross-coupling and dechloroamination reactions on the C(4)-Cl position of the requisite 2-(p-phenyl)-4-chloroquinazolines. The prepared compounds were characterized by means of 1H- and 13C-NMR, FT-IR and mass spectrometry techniques. The structure of 2-(4-chlorophenyl)-4-(2-(pyridin-4-yl) ethynyl) quinazoline from the 4-(ethynylpyridine) series was confirmed by single crystal X-ray analysis which indicates monoclinic crystal system and P21/c space group. Compounds from the 4-chloro-, 4-(pyridylamino)- and 4-(ethynylpyridine)-quinazoline series were evaluated for anti-Mycobacterium tuberculosis (Mtb) properties in vitro employing rifampicin as a reference drug. The results from the Alamar Blue assay (Mtb H37Rv strain) revealed promising MIC90 ranging from 125 µM. The cytotoxicity of the synthesised compounds was tested against the Raw 264.7 microphage cell line at a maximum concentration of 50 µM. The possible mode of interaction against the Mtb was theoretically explained through molecular 3ZXR protein and the more prominent hydrogen bond is observed between the nitrogen of the pyridine ring moiety of the 5 and 6 series with OH group of SER280. Also, a metal coordination between the methoxy benzene moiety of compound 6e and Mg2+ is also observed, explaining the SAR of these compounds to MtGS.

Research paper thumbnail of Sequential Extraction and Risk Assessment of Potentially Toxic Elements in River Sediments

Minerals, 2021

In this study, the sequential extraction method was applied to extract selected potentially toxic... more In this study, the sequential extraction method was applied to extract selected potentially toxic elements (PTEs) (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in river sediments collected from the Blood River situated in Seshego area, Limpopo Province, South Africa. The study aimed to assess a possible trend of mobilisation of these elements from sediment to water. The accuracy of the sequential extraction method was confirmed by analysing sediment-certified reference material, and quantitative percentage recoveries ranging from 86 to 119%, 81 to 111% and 77 to 119% were achieved for exchangeable, reducible and oxidisable fractions, respectively. The potential risk of the PTEs in sediments was evaluated. The calculated values of contamination factor (CF) as well as risk assessment code (RAC) for Cd, Cu, Ni and Pb revealed the mobility of these elements. The PTEs in river sediments are at a high toxicity-risk level and could therefore cause a threat to organisms dwelling in sediments and humans v...

Research paper thumbnail of Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State

Crystals, 2019

The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in ... more The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated...

Research paper thumbnail of Reactions and effect of N-sulfonylpyrrole yielding metal complexes: Crystal structural studies

Research paper thumbnail of Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides

Molecules (Basel, Switzerland), Jan 4, 2017

The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characte... more The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar-NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor si...

Research paper thumbnail of Synthesis, reactions and multinuclear NMR spectroscopic studies of organo bimetallic and trimetallic compounds

Research paper thumbnail of Correction: A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines

Organic & biomolecular chemistry, Jan 19, 2016

Correction for 'A convenient domino Ferrier rearrangement-intramolecular cyclization for the ... more Correction for 'A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines' by Paseka T. Moshapo et al., Org. Biomol. Chem., 2016, DOI: 10.1039/c5ob02536b.

Research paper thumbnail of A Convenient Domino Ferrier Rearrangement-Intramolecular Cyclization for the Synthesis of Novel Benzopyran-fused Pyranoquinolines

Org. Biomol. Chem., 2016

Lewis acid-mediated three component coupling of salicyladehydes, anilines and gylcals provided no... more Lewis acid-mediated three component coupling of salicyladehydes, anilines and gylcals provided novel benzopyran-fused pyranoquinolines stereoselectively, in moderate to high yields.

Research paper thumbnail of X-ray and NMR spectropscopic studies of selected heterocyclic compounds of phosphorus and nitrogen