Effects of hydrogen bonding between pyrrole-2-carboxaldehyde and nearest polar and nonpolar environment.

The present paper represents dominant effects of hydrogen bonding on the existence of different molecular aggregates in one of the heterocyclic pyrrole system: pyrrole-2-carboxaldehyde (PCL). Theoretical and experimental Raman spectral evidence verifies the existence of different molecular aggregates like dimeric, monomeric, hydrated complex states in PCL. Atoms in molecules (AIMs) analysis and fluorescence decay profile provide a strong signature of intermolecular hydrogen bonding (IHB) as the possible reason for the existence of cis form of dimeric (X) molecular aggregates. The high remnant polarization of 3.13μCcm and smaller dielectric loss in solid form of PCL arise due to in X by ordering of dipoles as a result of IHB. A remarkable high ferroelectric response in solid phase makes PCL a desirable candidate to be used as raw material for energy storage devices. For solution phase, in presence of external hydroxylic environment, PCL reacts with external water molecules through weak IHB and creates different hydrated PCL/(HO) complexes by creating water bridge with number of water molecules from 1 to n. An increasing number of water molecules helps to form stronger hydrated complex by separation of charges by lowering the transferring energy barrier.