The 2,2'-bipyridine ligand has been extensively used as a metal chelating ligand due to its robust redox stability and ease of functionalization. In contrast to other ligands, such as catechol, which is dianionic, and derivatives of the acetylacetonate ion, which are monoanionic, 2,2'-bipyridine is a neutral ligand. It thus forms charged complexes with metal cations, and this property has been exploited in the design and synthesis of metal-bipyridine complexes.
Ligands containing two or more 2,2'-bipyridine units can in principle be used as bridges to interconnect metal centers in a well-defined spatial arrangement. The uses of such ligands as precursors for helical assembly, chiral molecular recognition, luminescent devices, and other applications in photonics and optoelectronics and electrochemistry have been studying extensively.
UCHEM has been focusing on development of symmetric and unsymmetric 2,2’-bipyridine for around 10 years. Currently, there are around 60 derivatives of 2,2’-bipyridine available from warehouse. Most of them are supplied in kilograms, such as
2,2’-Bipyridine CAS: 366-18-7
2,2’-biquinoline CAS: 119-91-5
2,2'-biquinoline-4,4'-dicarboxylic acid CAS：1245-13-2
4,4'-Dinonyl-2,2'-bipyridine CAS: 142646-58-0
2,2'-Bipyridine-4,4'-dicarboxylic acid CAS:6813-38-3
2,2'-Dipyridyl N,N'-dioxide CAS: 7275-43-6
4,4’-Dimethoxy-2,2’-bipyridine CAS: 17217-57-1
5,5'-Dimethyl-2,2'-bipyridine CAS: 1762-34-1
2,2'-Bipyridine-5,5'-dicarboxylic acid CAS:1802-30-8
6,6'-Dimethyl-2,2'-bipyridine CAS: 4411-80-7
2,2'-Bipyridyl-3,3'-dicarboxylic acid CAS:4433-01-6
All the above are available in kilograms. They also provide special 2,2’-bipyridines under 1Kg as the following:
2,2'-Bipyridine-4,4'-diylbis-boronic acid CAS:159614-36-5
4,4'-Diethyl ester phosphonate-2,2'-bipyridine CAS: 174397-53-6
2,2'-Bipyridine-4,4'-bis(phosphonic acid) CAS: 194800-56-1
4-Methyl-2,2'-bipyridine-4'-carboxylic acid CAS: 103946-54-9
4-Ethenyl-4'-methyl-2,2'-bipyridine CAS: 74173-48-1
4-(4'-Methyl-2,2'-bipyridin-4-yl)butyric acidCAS: 114527-28-5
2,2'-Bipyridine-4,4'-dicarboxylic acid, 6,6'-dimethyl-dimethyl ester CAS:117330-40-2
4-Bromo-2,2'-bipyridine CAS: 14162-95-9
4-(Thiophen-2-yl)-2,2'-bipyridine CAS: 210363-85-2
4-Methyl-2,2'-bipyridine CAS: 56100-19-7
2,2'-Bipyridine-4-carboxylic acid CAS:1748-89-6
2,2'-Bipyridine-5-carboxylic acid CAS: 1970-80-5
2,2'-Bipyridine-6-carboxylic acid CAS: 4392-87-4
UCHEM also do customer synthesis for special 2,2’-bipyridine derivative.
2-(2-Pyridyl)pyridine is colorless to off-white crystal powder, an important isomer of the bipyridine family. It is a bidentate chelating ligand, forming complexes with many transition metals. For example, the complex of Fe(II) ion with 2,2’-bipyridine CAS: 366-18-7 is used for colorimetric analysis; N719 dye CAS:207347-46-4 is complex of Ru(II) with 2,2’-bipyridine-4,4’-dicarboxylic acid CAS: 6813-38-3, used for dye-sensitized solar cell (DSSC) with very high light to electricity conversion efficiency over 10%.
2-(2-Pyridyl)pyridine is prepared by the dehydrogenation of pyridine using Raney nickel
2C5H5N → (C5H4N)2 + H2
Although uncoordinated bipyridine is often drawn with its nitrogen atoms in cis conformation, the lowest energy conformation both in solid state and in solution is in fact coplanar, with nitrogen atoms in trans position. Protonated bipyridine adopts a cis conformation. Upon binding to metal ions the related N,N-heterocyclic ligand phenanthroline does not incur an enthalpic and entropic penalty, and thus its complexes tend to be more stable.
Reflecting the popularity of this ligand design, many substituted variants of bipy have been described.
Bipyridine complexes absorb intensely in the visible part of the spectrum. The electronic transitions are attributed to metal-to-ligand charge transfer (MLCT). In the "tris(bipy) complexes" three bipyridine molecules coordinate to a metal ion, written as [M(bipy)3]n+ (M = metal ion; Cr, Fe, Co, Ru, Rh and so on; bipy = 2,2′-bipyridine). These complexes have six-coordinated, octahedral structures and two enantiomers as follows: