Knuts, Soeren et al. published their research in Journal of Molecular Structure: THEOCHEM in 1994 | CAS: 253-50-9

2,6-Naphthyridine (cas: 253-50-9) belongs to naphthyridine derivatives. Six naphthyridine isomers are white solids with a surprisingly wide span of melting points: 1,6-Naphthyridine’s is the lowest at <40 ºC; 2,6-naphthyridine’s is the highest at 114–115 ºC. Very few metal complexes of naphthyridines other than 1,8-naphthyridine have been described.Application of 253-50-9

Phosphorescence of aromatic molecules was written by Knuts, Soeren;Agren, Hans;Minaev, Boris F.. And the article was included in Journal of Molecular Structure: THEOCHEM in 1994.Application of 253-50-9 This article mentions the following:

Quadratic response theory for singlet and triplet operators (O. Vahtras et al., 1992) was recently applied to series of small mols. as well as to several aromatic compounds A comparative anal. of the results of such calculations on the phosphorescence effect in benzene, naphthalene and various azabenzenes and azanaphthalenes is presented. The information gained from such calculations concerns polarization directions, oscillator strengths, radiative lifetimes and excitation energies for the triplet states. These quantities either refer to values averaged over the triplet states or to the specific triplet state spin sublevels. The vibronically induced phosphorescence problem, with specific reference to benzene phosphorescence which is forbidden both by spin and orbital symmetry and only allowed through the coupling of nuclear and electronic motions is also discussed. Results are compared with vapor phase data concerning total radiative lifetimes, and with data from phosphorescence microwave double resonance measurements of matrix isolated samples concerning the spin sublevel rates. In the experiment, the researchers used many compounds, for example, 2,6-Naphthyridine (cas: 253-50-9Application of 253-50-9).

2,6-Naphthyridine (cas: 253-50-9) belongs to naphthyridine derivatives. Six naphthyridine isomers are white solids with a surprisingly wide span of melting points: 1,6-Naphthyridine’s is the lowest at <40 ºC; 2,6-naphthyridine’s is the highest at 114–115 ºC. Very few metal complexes of naphthyridines other than 1,8-naphthyridine have been described.Application of 253-50-9

Referemce:
1,8-Naphthyridine – Wikipedia,
1,8-Naphthyridine | C8H6N2 – PubChem