Strong, Low-Energy Two-Photon Absorption in Extended Amine-Terminated Cyano-Substituted Phenylenevinylene Oligomers

Three quadrupolar oligophenylenevinylenes with five rings in the conjugated backbone, terminal donor groups, and various acceptors and/or donors along the backbone were synthesized and their two-photon spectroscopic properties investigated. These chromophores exhibit large two-photon absorption cross sections over a wide wavelength range and two distinct peaks, the strongest of which (δmax > 3600 GM) is observed at 960−970 nm, a wavelength close to twice the value of the linear absorption maximum (2λ(1)max). The findings on these chromophores are compared with those for analogous molecules with shorter conjugation length, for which the main two-photon band is at significantly shorter wavelength than 2λ(1)max.