Bipyridines also known as bipyridyls, dipyridyls, and dipyridines, are a family of chemical compounds with the formula (C5H4N)2, which are formed by the coupling of two pyridine rings. They are aromatic nitrogen heterocycles that form complexes with most transition metals. They interact with metals via both σ-donating nitrogen atoms and π-accepting molecular orbitals. Bipyridines figure prominently in studies of electron and energy transfer, supramolecular and materials chemistry, and catalysis.
Six isomers of bipyridine exist, but two isomers are prominent: 2,2'-bipyridine is a popular ligand in coordination chemistry and 4,4'-bipyridine is a precursor to the herbicide paraquat. The bipyridines are colourless solids, which are soluble in organic solvents and slightly soluble in water.
The 3,4'-Bipyridine derivatives inamrinone and milrinone are used occasionally for short term treatment of congestive heart failure. They inhibit phosphodiesterase and thus increasing cAMP, exerting positive inotropy and causing vasodilation. Inamrinone causes thrombocytopenia. Milrinone decreases survival in heart failure.
2,2'-Bipyridine (bipy or bpy (pronounced "bip-ee")) is an organic compound with the formula (C10H8N2). This colorless solid is an important isomer of the bipyridine family. It is a bidentate chelating ligand, forming complexes with many transition metals. Ruthenium complex and platinum complexes of bipy exhibit intense luminescence, which may have practical applications.
It is prepared by the dehydrogenation of pyridine using Raney nickel:
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.
4,4'-Bipyridine (4,4'-bipy) is a bipyridine which is mainly used as a precursor to N,N'-dimethyl-4,4'-bipyridinium [(C5H4NCH3)2]2+, known as paraquat. This species is electroactive, and its toxicity arises from the ability of this dication to interrupt biological electron transfer. Because of its structure, 4,4'-bipyridine can bridge between metal centres to give coordination polymers. 4,4'-bpy can also mediate electronic effects between two paramagnetic metal centers.
The fearful struggle's ended now and peace smiles on
our land,
And though we've yielded we have proved ourselves a
faithful band.
We fought them long, we fought them well, we fought
them night and day,
And bravely struggled for our rights while wearing of
the gray.
And now that we have ceased to fight and pledged our
sacred word,
That we against the Union's might no more will draw the
sword,
We feel despite the sneers of those who never smelt the
fray,
That we've a manly, honest right to wearing of the
gray.
Our cause is lost the more we fight 'gainst
o'erwhelming power,
All wearied are our limbs and drenched with many a
battle shower.
We feign we rest for want of strength in yielding up
the day,
And lower the flag so proudly born while wearing of the
gray.
Defeat is not dishonor, our honor not bereft,
We thank God that in our hearts this priceless boon was
left.
And though we weep just for those braves who stood in
proud array,
Beneath our flag and nobly died while wearing of the
gray.
When in the ranks of war we stood and faced the deadly
hail,
Our simple suits of gray composed our only coats of
mail.
And on the awful hours that marked the bloody battle
day,
In memories we'll still be seen wearing of the gray.
Oh! should we reach that glorious place where waits a
sparklin' crown,
For everyone who for the right his soldier life lay
down.
God grant to us the privilege upon that happy day,
Of claspin' hands with those who fell while wearing of