Authors: K.A. Nguyen and R. Pachter
Affilation: Air Force Research Laboratory, United States
Pages: 57 - 60
Keywords: modeling and simulation of optical limiting materials, ab initio electronic structure, porphyrin derivatives, electronic spectra, molecular structures
Ab initio electronic structure theory has been applied to predict the structures and electronic spectra of free-base porphyrin (PH2) and its meso-tetrahalogenated derivatives (m-PX8H2, X = F, Cl, Br). Structures, singlet-triplet energy gaps, and electronic spectra are predicted using the B3LYP method in conjunction with the 6-31G(d) basis set and the effective core potentials/basis sets of Stevens et al. Minimum energy structures of the lowest triplet excited states (T1) were found to retain D2h symmetry with stretched Cb-Cb and Cb-Cm bond distances. We found that halogenation at the four meso-positions significantly changes the ground state excitation energies and the singlet-triplet gap for the free-base parent compound.