Bidentate metal chelating ligand. Prepn from pyridine: H. Meyer, A. Hofmann-Meyer, J. Prakt. Chem. Chem.-Ztg. 102, 287 (1921); C. R. Smith, J. Am. Chem. Soc. 46, 414 (1924); using Raney Ni: W. H. F. Sasse, Org. Synth. coll. vol. V, 102 (1973). Manuf: P. F. H. Freeman, R. Ghosh, US 2962502 (1960 to I.C.I.). Absorption spectrum: P. Krumholz, J. Am. Chem. Soc. 73, 3487 (1951). Crystal structure: L. L. Merritt, Jr., E. D. Schroeder, Acta Crystallogr. 9, 801 (1956). Pharmacologic study: P. Bass et al., J. Pharmacol. Exp. Ther. 152, 104 (1966). Review of chemistry of complex formation: E. K"onig, Coord. Chem. Rev. 3, 471-495 (1968); of properties of metal complexes: G. Nord, Comments Inorg. Chem. 4, 193-212 (1985); of ligands containing multiple 2,2′-bipyridine units: C. Kaes et al., Chem. Rev. 100, 3553-3590 (2000); of synthesis methods: G. R. Newkome et al., Eur. J. Org. Chem. 2004, 235-254.