A study on the spectroscopy and photophysics of N-phenyl pyrrole and N-phenyl pyrazole

Comprehensive spectroscopic and photophysical studies of N-phenyl pyrrole (PPr) and N-phenyl pyrazole (PPz) in different solvents show that a new emission band appears due to aggregation of PPr in water. The presence of β-cyclodextrin (β-CD) in aqueous solution of PPr causes deaggregation but the twisted intramolecular charge transfer emission ceases due to the cavity effect. In PPz, aggregation and TICT emission are absent. Protonation in PPz is restricted to a single site only at very high acid concentration. Both the molecules are planar in the ground state.