Synthesis of soluble polyketones via a palladium-catalyzed polymerization reaction and the synthesis and study of new two-photon absorbing chromophores

A new route for the synthesis of soluble polyketones was developed through the cross-coupling reaction of an aryl dihalide and a diketone in the presence of a palladium complex and a bulky phosphine. The solubility of the polymers can be tuned by the α-substituent, which is next to the carbonyl group. Chemical modification of the carbonyl group, a versatile precursor for other functional groups, provided new classes of polymers and/or new routes to other important macromolecular architectures. The first soluble main-chain chiral polyketones have been synthesized through this condensation polymerization reaction. Reducing the steric hindrance of the substituents in the monomers increased the reactivity of the polymerization. The synthesized chiral polymers exhibited large optical rotations. CD spectra of the polymers are similar to those of the monomers suggesting little formation of secondary chiral configurations, and that polymers retain their original rigidities.; We have investigated in detail the structure-property relationships for two-photon absorbing chromophores and have confirmed that symmetry, conjugation length, and electron density are important factors for a large two-photon absorption cross-section. A number of new two-photon absorbing chromophores were synthesized and their optical properties were studied. When the molecules are large enough, it is possible that they are somewhat distorted so that the symmetry is lowered, and both one-photon and two-photon transitions are allowed between the same two states. For branched/dendritic molecules, there is a cooperative enhancement of the two-photon absorption so it is possible to increase the two-photon absorption cross-section by increasing the chromophore number density without causing aggregation.