Phenanthroline Ligands

Phenanthroline is 1,10-phenanthroline. A phenanthroline ligand refers to a ligand having a phenanthroline ring in its molecular structure. 1,10-phenanthroline has a planar rigid structure and plays an important role in coordination chemistry; its two adjacent atoms can form a feedback bond with many transition metals, resulting in a stable complex, which is important in many fields. For example, in analytical chemistry and homogeneous catalysis, complexes of phenanthroline with metals can be used as important chelating agents, and many complexes have been used as important electron transporters and chemical nucleases in life science research. Phenanthroline is an excellent electron acceptor with good coordination ability for transition metal ions, especially for low-valent metal ions. The introduction of the second ligand phenanthroline in the multi-component complex not only increases the stability of the complex, but also may result in novel materials with novel properties and structures. Many novel ligands can be obtained by introducing a substituent and a functional group at different positions of phenanthroline by nucleophilic substitution or electrophilic substitution. The introduction of these novel ligands into supramolecular systems such as calixarenes, crown ethers, fullerenes and cyclodextrins has revealed many novel structures and properties. Many novel complexes show good electrochemical, catalytic and photochemical properties, and also show good application prospects in antitumor activity.

Figure 1. Phenanthroline ligand

Applications:

Due to the specificity of its structure, phenanthroline ligands have broad applications in optical materials, organic chemistry and biomedicine.

• Optical material: The complex of phenanthroline ligand has good photothermal stability, high oxidation-reduction potential which makes it suitable to excite state lifetime and abundant luminescence signal, so it can form a strong MLCT transition state after absorbing ultraviolet or visible light. The formation of the MLCT transition state allows the metal complex of the phenanthroline ligand to have unique photochemical and photophysical properties. Therefore, the complex formed by the phenanthroline ligand and the metal is widely used in the fields of solar energy conversion colorimetric analysis, supramolecular assembly, optical information storage, and photoluminescence probes in vivo. Especially phenanthroline and hydrazine as a photoluminescence probe, the complex has excellent sensitivity and selectivity, and can detect physiologically active small molecules such as HClO and NO. In addition, complexes of phenanthroline with metals can also be used to make sensors such as pH sensors and oxygen sensor.
• Organic synthesis: Some complexes formed by phenanthroline ligands and transition metals have catalytic properties and also play a role in the field of organic synthesis. The types of reactions catalyzed include cycloaddition reactions, cross-coupling reactions, and decarboxylation coupling reactions. Moreover, the phenanthroline transition metal complex has no significant loss of activity after use and can be used continuously.
• Biology and medicine: The heterocyclic compound phenanthroline has a strong affinity with biomolecules such as DNA and RNA, and the rare earth ion has a strong penetrating effect on cells. The complex formed by the phenanthroline and the rare earth element enters the cell through the cell membrane, and has catalytic cleavage effect on DNA and RNA. It can efficiently cut the phosphodiester bond in DNA and RNA, and then hydrolyze and cut it into different sizes. The complex can efficiently cleave the phosphodiester bond in DNA and RNA, and then hydrolyze and cleave it into fragments of different sizes, which can cause cell DNA repair failure and activate apoptotic genes, leading to cell apoptosis. Therefore, the complex formed by phenanthroline and rare earth metal can be antibacterial and antitumor, and plays a role in the fields of biology, medicine and pesticides.

References

1. Nbili, Wijdene. (2018). "A Hirshfeld surface analysis, crystal structure, and physicochemical studies of a new Cu(II) complex with the 1,10-phenanthroline ligand." Journal of Coordination Chemistry 71(16) 2526-2539.
2. Pomeranc D. (2001). "Octahedral Fe(II) and Ru(II) complexes based on a new bis 1,10-phenanthroline ligandthat imposes a well defined axis."Journal of the American Chemical Society 123(49),12215-21.
3. Cunningham C T. (2000), " Structural and photophysical studies of Cu(NN)2+ systems in the solid state. Emission at last from complexes with simple 1,10-Phenanthroline ligands." Inorganic Chemistry 39(16), 3638-44.