Ru(II) and Co(II) complexes of bis(pyrazolyl)pyridine and pyridine-2,6-dicarboxylic acid: Synthesis, photo physical studies and evaluation of solar cell conversion efficiencies
Department of Chemistry, University of Fort Hare, Private Bag X1314, Alice, South Africa
Motaung, M.P., Department of Chemistry, University of Fort Hare, Private Bag X1314, Alice, South Africa; Ajibade, P.A., Department of Chemistry, University of Fort Hare, Private Bag X1314, Alice, South Africa
We report the synthesis of two nitrogen chelating ligands: 2,6-bis(pyrazolyl)pyridine (L1); 2,6-bis(3,5-dimethylpyrazolyl)pyridine (L2) and their corresponding ruthenium(II) and cobalt(II) complexes formulated as [RuL1L(NCS)2] (C1), [RuL2L(NCS)2] (C2), [CoL1L(NCS)2] (C3) and [CoL2L(NCS)2] (C4) where L= pyridine-2,6-dicarboxylic acid. The synthesis of the ligands were confirmed by 1HNMR spectroscopy and FTIR spectra studies confirmed the bonding of the Ru and Co ions to the ligands via the nitrogen atoms. Electronic absorption spectra indicates the geometries around the metal ions are six coordinate octahedral in which L1 or L2 acts as tridentate chelating ligands. In the cyclic voltammetry, cobalt(II) complexes exhibited lager redox potentials as compared to the ruthenium(II) complexes. The conversion efficiencies of the fabricated solar cells using the complexes as sensitizers showed that [RuL2L(NCS)2], C2 on TiO2 semiconductor produced the highest open-circuit photovoltage (Voc) of 87.3 × 10-3 mV, short-circuit photocurrent (Jsc) of 0.022 mA/cm-2 and the solar conversion efficiency was 101 × 10-5 %. © 2015 The Authors.