Convenient synthesis of tridentate 2,6-di(pyrazol-1-yl)-4-carboxypyridine and tetradentate 6,6′-di(pyrazol-1-yl)-4,4′-dicarboxy-2,2′-bipyridine ligands

• Published in: Tetrahedron letters Vol. 52; no. 5; pp. 584 - 587
• Main Authors: Klein, Cédric, Baranoff, Etienne, Grätzel, Michael, Nazeeruddin, Md. Khaja
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 02.02.2011; Elsevier
• Subjects: Bipyridine; Chemistry; Chemistry, Organic; Dye-sensitized solar cells; Physical Sciences; Pyrazole; Science & Technology; Terdentate ligands; Tetradentate ligands; Dye-sensitized solar cells; Tetradentate ligands; Terdentate ligands; Bipyridine; Pyrazole; SOLAR-CELLS; RUTHENIUM(II); COMPLEXES; SENSITIZERS; 2,2'/6',2''-TERPYRIDINES; TERPYRIDINE ANALOGS
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2010.12.001

Citrazinic acid is used as a convenient starting material for both tridentate 2,6-di(pyrazol-1-yl)-pyridine and tetradentate 6,6′-di(pyrazol-1-yl)-2,2′-bipyridine ligands containing carboxylic groups useful for further anchoring of sensitizer on TiO2 for dye-sensitized solar cells. Citrazinic acid is used as a convenient starting material for both tridentate 2,6-di(pyrazol-1-yl)-pyridine and tetradentate 6,6′-di(pyrazol-1-yl)-2,2′-bipyridine ligands containing carboxylic groups useful for further anchoring of sensitizer on TiO2 for dye-sensitized solar cells (DSCs). Using 2,6-dichloro-4-carboxypyridine, the synthesis of the terdentate ligands was improved compared to previously used 2,6-dibromo-4-carboxypyridine or 2,6-dichloro-4-ethylcarboxylate pyridine. Controlling the reaction conditions, it is possible to efficiently obtain the monosubstituted 2-chloro-6-pyrazol-1-yl-4-carboxypyridine, a key intermediate for the preparation of tetradentate 6,6′-di(pyrazol-1-yl)-4,4′-dicarboxy-2,2′-bipyridine ligand.