Optical limiting properties of D-π-A BODIPY dyes in the presence and absence of methyl groups at the 1,7-positions

The optical limiting properties of three meso-pentafluorophenylstyryIBODIPY dyes are investigated in the presence and absence of methyl groups at the 1,7-positions that hinder free rotation of the meso-aryl group. Pentafluorophenyl groups are introduced at the meso-position, while 4-diethylaminostyryl groups are introduced at the 3- and/or 5-positions to form dyes with strong donor-pi-acceptor (D-pi-A) properties to enhance the dipole moment of the molecule. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability value obtained for a monostyryl dye with no methyl groups at the 1,7-position. Bromination at the 2,6-positions of a 1,7-methyl substituted dye is found to result in second-order hyperpolarizability that is an order of magnitude lower than that calculated for the analogous non-halogenated dye.