Theoretical Investigation of the Electronic and Geometric Structures and Nonlinear Optical Properties of 2H-Pyrrole Derivatives

We present Hartree-Fock ab initio extended basis Set. calculations on the geometric and electronic structures and static first-order (α) and second-order (β) polarizabilities of a series of 2-methylene-2H molecules, substituted by amino and nitro groups. We observe a dramatic evolution of the 2H-pyrrole ring geometry as a function of the nature and location of the substituent. This geometry evolution affects the first-order polarizabilities only to a very slight extent but exerts a marked influence on the second-order polarizability values, β significantly decreasing with increasing aromatic character. the 2-(nitromethylene)-5-amino-2H-pyrrole derivative is calculated to possess a β_vec value as large as that of p-nitroaniline.