The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Infrared spectra of 2,9-dimethyl-1,10-phenanthroline, its hydrates and acid perchlorate》. Authors are Grigg, E. C. M.; Hall, J. R.; Plowman, R. A..The article about the compound:2,9-Dimethyl-1,10-phenanthroline hemihydratecas:34302-69-7,SMILESS:CC1=CC=C2C=CC3=CC=C(C)N=C3C2=N1.[H]O[H].CC4=CC=C5C=CC6=CC=C(C)N=C6C5=N4).Formula: C28H26N4O. Through the article, more information about this compound (cas:34302-69-7) is conveyed.
Bands, 1610-1545 cm.-1, are attributed to stretching vibrations within the phenanthroline ring system. The in-phase out-of-plane motion of the ring H atoms is associated with intense absorption at 845 cm.-1 There is a strong band at 728 cm.-1, not due to out-of-plane CH deformation. The strongest bonds are shifted in the perchlorate spectrum.
Although many compounds look similar to this compound(34302-69-7)Formula: C28H26N4O, numerous studies have shown that this compound(SMILES:CC1=CC=C2C=CC3=CC=C(C)N=C3C2=N1.[H]O[H].CC4=CC=C5C=CC6=CC=C(C)N=C6C5=N4), has unique advantages. If you want to know more about similar compounds, you can read my other articles.
Reference:
Nitrile – Wikipedia,
Nitriles – Chemistry LibreTexts