2,2'-Biquinoline is an organic compound consisting of two quinoline units linked at the 2-position. It is a pale yellow to yellow crystalline solid with a molecular formula of C18H12N2. This compound is a classic chelating ligand, particularly known for forming intensely colored complexes with various metal ions, most notably the orange-red complex with cuprous ion (Cu(I)), which has been historically used in analytical chemistry for the colorimetric determination of copper. The primary and significant application of 2,2'-biquinoline is in the field of materials science, specifically in the development of organic light-emitting diodes (OLEDs) and other organic electronic devices. It serves as a crucial building block or precursor for synthesizing more complex organic semiconductors, electron-transporting materials (ETMs), and host materials due to its rigid, planar, and conjugated structure which facilitates charge transport. Its derivatives are explored for use in the emissive or charge-transport layers of OLEDs. From a synthetic chemistry perspective, 2,2'-biquinoline is also a valuable heterocyclic building block. Its structure provides a platform for further functionalization, making it useful in the preparation of more elaborate ligands for catalysis or advanced organic materials. It is commercially available and handled as a standard laboratory chemical for research purposes.