Optical limiting with soluble two-photon absorbing quadrupoles: Structure–property relationships

The optical power limiting in the visible region of a series of two-photon absorbing quadrupoles built from conjugated backbones bearing electro-active peripheral groups was investigated. Nonlinear absorption experiments demonstrate that these molecules show marked nonlinear behaviour for short pulses (3 ns) in the ns regime. Structure–property relationships could be derived, emphasizing the role of the conjugated connectors and of the end-groups for improving the optical limiting efficiency. Push–push systems are more efficient than pull–pull systems, but at the expense of reduced transparency. Pyridine-N-oxides, terminal moieties which act in synergy as both donor and acceptor end-groups, lead to improved efficiency/transparency trade-off.