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Published on: June 10, 2021
Excited state behavior of pyrrole 2-carboxyldehyde: theoretical and experimental study
Nidhi Singla1, Rakesh Kumar, Anirban Pathak
1Department of Physics and Materials Science & Engineering, Jaypee Institute of Information Technology, Noida, Uttar Pradesh 201 307, India.
Abstract:
Photophysical and photochemical dynamics of excited state proton transfer reaction have been reported for Pyrrole 2-carboxyldehyde (PCL). Experimental and theoretical observations yield all possible signatures of intramolecular and intermolecular proton transfer in an excited state. Dual emission (~325 nm, ~375 nm) on photo excitation indicates the existence of more than one species in an excited state. Computed reaction pathway and two-dimensional potential energy profile in the ground state reveals a single minimum corresponding to normal form (E). Dual minima in excited state energy profile shows the existence of two species, one normal and other zwitterionic (Z*) species. A large Stokes shifted emission at ~375 nm in hydrocarbon medium reveals the existence of zwitterionic species due to Excited state intramolecular proton transfer (ESI(ra)PT). Excited State Intermolecular proton transfer (ESI(er)PT) is observed in a hydroxylic environment around 430-490 nm. pH variation in hydroxylic medium suggests the formation of anion (A((-))) from Z*.
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