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

摘要

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) complexesformulated 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 by1 HNMR spectroscopy and FTIR spectra studies confirmed the bonding of the Ru and Co ions to theligands via the nitrogen atoms. Electronic absorption spectra indicates the geometries around the metalions are six coordinate octahedral in which L1 or L2 acts as tridentate chelating ligands. In the cyclicvoltammetry, 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 sensitizersshowed that [RuL2L(NCS)2], C2 on TiO2 semiconductor produced the highest open-circuit-3 -2 photovoltage (Voc) of 87.3 10 mV, short-circuit photocurrent (Jsc) of 0.022 mA/cm and the solar-5conversion efficiency was 101 10 %.