  Interstellar Polycyclic Aromatic Hydrocarbon (PAH) molecules exist in diverse
forms depending on the local physical environment. Formation of ionized PAHs
(anions and cations) is favourable in the extreme conditions of the ISM.
Besides in their pure form, PAHs are also likely to exist in substituted forms;
for example, PAHs with functional groups, dehydrogenated PAHs etc. A
dehydrogenated PAH molecule might subsequently form fullerenes in the ISM as a
result of ongoing chemical processes. This work presents a Density Functional
Theory (DFT) calculation on dehydrogenated PAH anions to explore the infrared
emission spectra of these molecules and discuss any possible contribution
towards observed IR features in the ISM. The results suggest that
dehydrogenated PAH anions might be significantly contributing to the 3.3 {\mu}m
region. Spectroscopic features unique to dehydrogenated PAH anions are
highlighted that may be used for their possible identification in the ISM. A
comparison has also been made to see the size effect on spectra of these PAHs.
