DFT Studies of Electronic and UV-Vis Properties of Pyrrole-Based Oligomers

Density functional theory (DFT) calculations were performed to examine the electronic and vibrational characteristics of three pyrrole-based monomers, linear pyrrole dimers and tetramers, and cyclic pyrrole tetramers, porphyrin and HTPP, using the B3LYP/6-31+G(d,p). Charge redistribution is responsible for porphyrin's notable decrease from 2.91 eV in its singlet ground state (S0) to 1.38 eV in its triplet state (T1), according to the molecular orbital investigations. Porphyrin's strong absorption in the visible spectrum is the result of an increase in conjugation across the series, as seen by UV-Vis spectroscopy. Increased vibrational activity in the dimers and distinctive vibrational modes in porphyrin, are highlighted by IR spectroscopy analysis. By clearly establishing the connection between molecular structure, conjugation, and photophysical characteristics, these results offer important information about the electronic and photophysical behavior of porphyrin and pyrrole derivatives.