Optical Limiting Characteristics of Dendrons and Dendrimers Incorporating Dithienylpolyene Moieties

Abstract

Over the past decade there has been considerable progress in the design of new chromophores for potential optical limiting applications. Most of the focus has been centered on molecules that are capable of efficient excited state absorptions whose cross-sections are larger than the original π-π* excitation cross-section, usually referred to as reverse saturable absorbers (RSAs). The vast majority of chromophores having RSA characteristics depend on efficient intersystem crossing from the excited state singlet (S₁) to a highly absorbing and relatively long-lived triplet state (T₁). However, much less attention has been paid to alternative excited state absorptions, particularly from charge states such as polaronic radical-ions and bipolaronic diions. In this presentation, we propose that monodisperse dendrimers based on dendron coupling to core molecules such as bisphenol A are potential optical limiting materials based on photo-generation of such charge states in the dendron-attached chromophores, such as dithienylpolyenes. The design and syntheses of these dendrons and dendrimers are presented, and the absorption characteristics of the most likely charge states discussed from an optical limiting perspective.