Abstract
M.Sc. (Chemistry)
Despite the greener prospects associated with solar cell technology, low conversion efficiencies due to spectral mismatch remains a major concern. A possible technique to limit spectral mismatch involves the adaptation of the solar spectrum to the solar cell via the implementation of a spectral converter.
Although the lanthanides offer promising spectral converting capabilities, they do not possess strong luminescence as a consequence of Laporte selection rules. Nevertheless, these rules may be relaxed via the indirect “antenna effect” sensitization of the lanthanide using light harvesting ligands (chromophores) to form lanthanide complexes, capable of behaving as spectral converters to improve the conversion efficiency of ruthenium-based dye-sensitized solar cells.
Our research interest into spectral converters led us to a compound, dating back a century, the ammonium salt of nitrosophenylhydroxylamine, better known as cupferron due to its ability to precipitate iron (ferrate) and copper (cuprate) ions in quantitative analysis. The research interest into this compound and its analogues for this study stemmed from Kolthoff’s conductivity studies on cupferron which revealed its light-sensitive nature as it decomposed upon prolonged exposure to light. Furthermore, light sensitivity studies performed by Ela and Abou on cupferron to determine the mean life times of the excited states indicated that an n→π* transition of the nitroso group produced an absorbance band at 700 nm. Considering the work done by Kolthoff, Ela and Abou and to the best of our knowledge, literature had revealed very little work was performed using these compounds over the last three decades with respect to their evaluation as potential chromophores. As a direct result of this gap observed in the literature, our research interest into the study of these compounds was realized.
The findings of this study showed cupferron type compounds and their respective lanthanide complexes was successfully characterized using techniques such as 1H NMR, FT-IR, CHN elemental analysis, HRMS and melting point determination studies. The 1H NMR and FT-IR analysis supported the coordination of the cup-type ligands to the respective Ln elements. CHN elemental analysis proposed the coordination of the cup-type ligands to Er, Ho, Nd, Eu and Dy led to 1:2 Ln: ligand complexes which all contained coordinated nitrates in addition to the water molecules of the hydrated salts and was later confirmed using HRMS studies.