Browsing by Author "Naimhwaka, Johannes"

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    Photophysical, electrochemical, and DFT studies of the novel azacrownbridged dinuclear ruthenium dye sensitizers for solar cells
    (University of Namibia, 2019) Uahengo, Veikko; Cai, Ping; Naimhwaka, Johannes; Rahman, Ateeq; Daniel, Likius S.; Bhakhoa, Hanusha; Rhyman, Lydia; Ramasani, Ponnadurai
    A dinuclear ruthenium bipyridyl complex with 1,10-diaza-18-crown-6 bridging ligand was synthesized and characterized. Its photophysical and electrochemical properties were also studied. DFT computations were performed to complement the experimental investigations. Analysis of the results indicates that the path in which charges move from one metal center to the other is significant for effective electronic coupling. However, electron transfer between the two ruthenium centers is hindered by the azacrown bridging ligand, compared to the smooth electronic transfer reported for a related dye involving an azo bridging ligand.
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    A ruthenium bipyridyl molecular dye sensitizer and an excited‑state intermolecular proton transfer‑active colorimetric probe for anions, with high affinity towards CN− in DMSO
    (Springer, 2021) Naimhwaka, Johannes
    A ruthenium bipyridyl-dye sensitizer (N) based on the naphthyl-thiazole anchoring-ancillary ligand was synthesized and characterized using spectroscopic methods of UV–Vis, 1H NMR, FTIR and fluorescence. The functional properties of N were investigated through its photoinduced and intramolecular based charge transfer mechanisms. Subsequently, N displayed interesting charge transfer-based properties (ESIPT) that are complementary to molecular photovoltaic and chemosensing properties. The properties were investigated and studied in dimethyl sulfoxide (DMSO), due to its polar nature and solubility of the dye. Dye sensitizer exhibitions were investigated through solvatochromism effect on the optoelectronic properties, while chemosensing abilities were inspected through colorimetric activities, upon molar addition of anions. Thus, it was established that a dual functional N is a potential dye sensitizer with optoelectronic properties displaying high molar extinction coefficients in acetone. In addition, it was found that N is a colorimetric and fluorometric probe selective and sensitive to biologically important anions of CN−, F−, OH− and AcO− through fluorescence enhancement, as a result of hydrogenbonding leading to deprotonation. The sensing probe, however, displayed more strongly association with CN−.