An Ab initio Investigation of Pyrene Electronic Structure

Document Type : Research Paper




Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds consisting of more than two
benzene rings fused in a linear, angular, or clustered arrangement and do not contain hetero atoms
or carry subsistent. PAHs originate from various sources. They are primarily formed by
incomplete combustion of carbon-containing fuels such as wood, coal, diesel, fat, or tobacco. The
present study reports an investigation of the electronic structure of Pyrene by use of different
model chemistries. We also made a comparison between different model chemistries. Linear
relationship between the energy and Z-matrix of the structure were found. The energy diagrams
vs. the number of primitive Gaussian wave functions and vs. distance matrix shows the energy
variations in model chemistries HF/6-31G*, HF/6-31++G**, MP2/6-31G, MP2/6-31++G**,
BLYP/6-31G, BLYP/6-31++G**, B3LYP/6-31G and B3LYP6-31-HEG**, as well. High symmetry
of the Pyrene molecules makes four regions in the study of the NMR shielding tensors. The
isotropic and anisotropic tensors of the Pyrene structure, calculated with different model
chemistries, too. The results show that only the C and D part of the Pyrene structure are affected
by the magnetic field.