ALBERT OFORI
@ucc.edu.gh
CHEMISTRY
University of Cape Coast
RESEARCH, TEACHING, or OTHER INTERESTS
General Chemistry, Inorganic Chemistry, Physical and Theoretical Chemistry, Multidisciplinary
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Charity Owusu, Albert Ofori, Frank Adusei-Mensah, David Kwesi Dodoo, and David K. Essumang
Elsevier BV
Charity Owusu, Albert Ofori, Frank Adusei-Mensah, Joseph Kweku Adjei, George Yaw Hadzi, John Kwesi Bentum, Reginald Quansah, and David K Essumang
SAGE Publications
Occupational exposure to smoke and polycyclic aromatic hydrocarbons (PAHs) poses significant health risks, especially for commercial fish smokers who are regularly exposed to high levels of smoke and particulate matter. This study aimed to evaluate the exposure levels and assess the health risks associated with PAHs, phenols, phthalates, and substituted benzenes among 155 fish smokers in Ghana. A total of 155 urine samples from fish smokers across selected coastal regions in Ghana were collected and analyzed. The sample preparation was conducted using the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERs) method, as standardized by the Association of Official Analytical Chemists (A.O.A.C.). Analysis was performed utilizing the Shimadzu GC-MS QP 2020. The type of firewood used by fish smokers significantly influenced the levels of PAHs detected in the urine samples. Hardwoods such as odum, acacia, and cocoa, with their dense structures and combustion characteristics, were found to produce higher levels of PAHs. In contrast, softer woods like sugar cane and palm kernel released lower PAH levels during combustion. The findings indicate that fish smokers utilizing various wood types and unfiltered ovens, specifically the “Chorkor Oven,” are exposed to elevated levels of PAHs, phenols, phthalates, and substituted benzenes through inhalation during work hours. Cancer risk assessments revealed risk levels for PAHs ranging from 6.00E−04 to 4.14E−01, phenols from 0.00E+00 to 3.70E−01, substituted benzenes from 9.04E−08 to 1.99E−01, and phthalates from 3E−04 to 2.09E+04. These values exceed the limits by the U.S. Environmental Protection Agency (U.S.E.P.A.) of 10E−06. Furthermore, the estimated non-cancer hazard quotient values for hydrocarbons ranged from 8.42E+00 to 1.99E+01, all exceeding the threshold of 1, as outlined by both the U.S.E.P.A. and the World Health Organization (WHO), indicating substantial potential health risks for commercial fish smokers.
Pipsa Hirva, Sirpa Jääskeläinen, Meeri Ollikainen, Albert Ofori, and Igor O. Koshevoy
Wiley
AbstractThe octahedral complex [RhCl2(ppkoH)(ppko)] (1) was obtained from the reaction between RhCl3 and phenyl 2‐pyridyl ketoxime (ppkoH). Attempts to prepare the corresponding octahedral platinum compound from K2PtCl6 gave instead the square planar [Pt2+(ppko)2] (2), but when the halogen was changed to bromine, the octahedral [Pt4+Br2(ppko)2] (3) was formed. The crystal structures were determined by X‐Ray crystallography. All the compounds have two N,N‐chelating oxime ligands. In 1, one of them is deprotonated, while in 2 and 3 both ligands are deprotonated. Compounds 1 and 3 have two halogen ligands in trans position. In 1 the oxime groups are situated mutually in cis position with an intramolecular hydrogen bond between the two N−O(H) groups. The formation of 2 involves reduction of the platinum metal and the complex has oximes in trans position to each other. Compound 3 has an all‐trans geometry. Since octahedral and square planar compounds have a possibility to isomerism, we studied the relative stability of different geometries by DFT calculations. A mixture of isomers is likely to be formed in the reactions, but the most stable form was found to crystallize. The properties of the electron density in the preferred isomers were also investigated via QTAIM methods.
Samuel Tetteh, A. Ofori, A. Quashie, S. Jääskeläinen and S. Suvanto
Abstract Natural clay extracted from the Central Region of Ghana was used for this study. Energy dispersive X-ray and powder X-ray diffraction analysis showed the composition of the clay to be 67.5% kaolinite and 32.5% muscovite. The samples were successfully modified by H2SO4 and NaOH activation. They were also characterized by scanning electron microscopic and Fourier transformed-infrared spectrophotometric techniques. Batch adsorption studies revealed that the samples are effective adsorbents for the removal of Pb(II) ions from aqueous media. Factors studied include contact time, pH, effect of ionic strength and the mass of adsorbent. Generally, the alkali activated samples had the highest adsorptive capacity followed by the acid activated clay. The kinetics of the adsorption process fitted the pseudo-second order model and the adsorption isotherm conformed to the Langmuir as well as the Freundlich models. All the experiments were carried out at room temperature (303 K).
Samuel Tetteh and A. Ofori
Abstract The M–Ccarbene bond in metal (M) complexes involving the imidazol-2-ylidene (Im) ligand has largely been described using the σ-donor only model with donation of σ electrons from the sp-hybridized orbital of the carbene carbon into vacant orbitals on the metal centre. Analyses of the M–Ccarbene bond in a series of group IA, IIA and IIIA main group metal complexes show that the M-Im interactions are mostly electrostatic with the M–Ccarbene bond distances greater than the sum of the respective covalent radii. Estimation of the binding energies of a series of metal hydride/fluoride/chloride imidazol-2-ylidene complexes revealed that the stability of the M–Ccarbene bond in these complexes is not always commensurate with the σ-only electrostatic model. Further natural bond orbital (NBO) analyses at the DFT/B3LYP level of theory revealed substantial covalency in the M–Ccarbene bond with minor delocalization of electron density from the lone pair electrons on the halide ligands into antibonding molecular orbitals on the Im ligand. Calculation of the thermodynamic stability of the M–Ccarbene bond showed that these interactions are mostly endothermic in the gas phase with reduced entropies giving an overall ΔG > 0.
J. Adjei, Albert Ofori, H. K. Megbenu, Thomas Ahenguah, A. Boateng, George Adjei, J. K. Bentum and D. Essumang
Adnana Zaulet, F. Teixidor, P. Bauduin, O. Diat, P. Hirva, Albert Ofori and C. Viňas
F. Estevan, P. Hirva, Albert Ofori, M. Sanaú, T. Špec and M. Úbeda
The versatility of pyrazole/pyrazolate as ligands has allowed the synthesis and the structural characterization of four different types of new orthometalated palladium compounds, for which DFT calculations have been performed in order to investigate their relative stabilities. [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz)}2] (R = R' = H, 2a; R = Br, R' = H, 2b; R = CH3, R' = H, 2c; R = H, R' = CH3, 2d; R = Br, R' = CH3, 2e) compounds with exo-bidentate pyrazolatos are the first paddlewheel dinuclear palladium(II) compounds with pyrazolato bridging ligands described and characterized in the literature. In the process of the synthesis of 2a, a new tetranuclear intermediate compound, [Pd4{μ-(C6H4)PPh2}4(μ-pz)2(μ-OH)2] (3a), has been isolated and structurally characterized. Compounds of the general formula [Pd2{μ-(C6H4)PPh2}2Br2(R,R'2pzH)2] (R = R' = H, 4a; R = Br; R' = H, 4b; R = CH3; R' = H, 4c; R = H; R' = CH3, 4d; R = Br; R' = CH3, 4e) with pyrazoles as monodentate ligands have also been obtained, in which, according to the QTAIM analysis, additional Br···HNpz weak interactions stabilize their structure. The tetranuclear Pd2Ag2 compounds, [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz-Ag-R,R'2pz)}2] (R = R' = H, 5a; R = Br; R' = H, 5b; R = CH3, R' = H, 5c), showed a distorted tetrahedron disposition of the metal atoms. The QTAIM analysis revealed an enhanced stability because of additional metal-metal interactions. New palladium(III) compounds, [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz)}2Cl2] (R = R' = H, 6a; R = Br, R' = H, 6b) were also synthesized by oxidation of compounds 2 with PhICl2. DFT calculations highlighted their greater stability compared to that of similar compounds with N,N-donor ligands, such as formamidinatos and triazenidos.
Albert Ofori, Sonja Suvanto, S. Jääskeläinen, L. Koskinen, I. Koshevoy and P. Hirva
Silver imidazolecarbaldehyde oxime complexes [Ag(1-methyl-1H-imidazole-2-carbaldehyde oxime)2][NO3] (1), [Ag(1-methyl-1H-imidazole-2-carbaldehyde oxime)2][ClO3] (2), [Ag(1H-5-methylimidazole-4-carbaldehyde oxime)]2[NO3]2 (3), [Ag(1H-imidazole-2-carbaldehyde oxime)]n[NO3]n (4), [Ag(1H-4-methylimidazole-5-carbaldehyde oxime)]n[ClO3]n (5), and [Ag(N-hydroxy-1-methyl-1H-imidazole-2-carboximidamide)2]2[CF3SO3]2 (6) were structurally and computationally analyzed. Weak intramolecular interactions were found to play the main role in determining the most favorable structure of the free ligands, therefore controlling the final coordination mode, and the nuclearity of the complexes. Further information on the nature of the intra- and intermolecular interactions were provided utilizing computational density functional theory calculations and topological charge density analysis according to the Quantum Theory of Atoms in Molecules. The efficient control of the structure of the complexes also results in a better contro...
F. Estevan, S. Ibáñez, Albert Ofori, P. Hirva, M. Sanaú and M. Úbeda
Wiley
AbstractNew palladium(III) compounds of formula Pd2[(C6H4)PPh2]2[OXC(C6H5)]2Cl2[3a(X = O);3b(X = S)] were obtained by the oxidation of the analogous palladium(II) ones with PhICl2and were characterized by31P,1H, and13C NMR spectroscopy at 223 K. Compound3awas also structurally characterized by single‐crystal X‐ray diffraction methods, which revealed a Pd–Pd distance of 2.5212(10) Å. DFT calculations were conducted to study the stability of all of these new palladium(III) and ‐(II) compounds with focus on the influence of the O↔S substitution of the donor atom in the ligand. The palladium(II) compounds Pd2[(C6H4)PPh2]2[OXC(C6H5)]2[2a(X = O),2b(X = S)] were also tested as precatalyst in two reactions: (1) the acetoxylation of 2‐phenylpyridine and (2) the room‐temperature 2‐phenylation of indoles. Compound2bis a better precatalyst than2ain the first reaction (4 h; isolated yield, 67.5 vs. 50.4 %). In the second catalytic reaction, isolated yields of 97 (10 h, substrate: 1‐methylindole) and 99 % (24 h, substrate: indole) were obtained with2aas the precatalyst, whereas2bgave low or no conversion.