Naphthalidine, also named as dinaonaphthalene, is a heterogeneous heterocyclic system formed by the combination of two pyridine rings. There are six isomers owing to the distinct location of nitrogen atoms in the structure of naphthalidine. Among these isomers, 1,6-naphthyridne and 1,8-naphthyridine have roused more interest due to special structures. 1,6-naphthalidine derivatives are widely distributed in nature and functional 1,6-naphthyridine derivatives exhibit a wide range of biological activities, such as anti-cancer, anti-AIDS, anti-microbial infection, etc. 1,8-naphthalidine and its derivatives can not only recognize many kinds of metal ions and form metal complexes, they are widely used in the study of metal ions, but also specifically recognize small molecules and nucleic acids.
Fig. 1 the structures of naphthyridine isomers
A large number of naphthalidine derivatives are not only good fluorescent substances, but also have good antibacterial activity, so naphthalidine derivatives have gradually become the focus of scientific research since the new century due to their diversified properties and increasing applications in medicine, biology, materials and other disciplines.
Photochemistry: In terms of photochemistry, naphthalidine derivatives have special electromagnetic and optical properties, and have been used in new energy conversion, optoelectronic storage, signal display, new optoelectronic materials, optoelectronic components, rare earth ions and as luminous probes in the human body. Moreover, naphthalidine compounds have attracted the attention of many scientists who study naphthalidine derivatives because of their good physical and chemical properties and broad application prospects.
Medicine: Naphthalidine derivatives have good antibacterial activity and bactericidal effect, and can be used as anti-tumor drugs, antimalarials, cystatin, etc. Some researchers have studied the pharmacology and development prospect of naphthalidine derivatives and found that many 1, 6-naphthalidine derivatives have good antibacterial activity. Therefore, the research on effects of naphthyridine compounds in the pharmacological properties, antibacterial activities and DNA, has gradually become a focus of scientific research and development.
DNA/RNA Recognition: Naphthalidine derivatives have been widely studied for their biological activities. Among these compounds, 1, 8-naphthyridine derivatives, which have been shown to have good biological activity, such as anticancer, anti-inflammatory, and anti-tuberculous activities, have attracted the interest of researchers. The research showed that the anticancer activity of these 1, 8-naphthyridine derivatives was caused by their insertion into DNA. The anticancer activity of these compounds combined with DNA prompted the researchers to make new drugs.
Fig. 2 Recognition of a single guanine bulge by 1,8-nahthyridine derivative (Journal of the American Chemical Society 2003, 125, 8972-8973)
Molecular Recognition: In the naphthalidine structure, the two nitrogen atoms on the naphthalidine ring have a spacing of about 2.307 Angstrom, which can well meet the needs of rigid coordination. At the same time, the addition of hydrogen bond donors with active amino groups can enable the derivatives to form single-tooth, double-tooth or two-nuclear bridged ligands with recognized molecules and form complexes with a variety of metal ions.