Optical, third order non-linear optical and electrochemical properties of dipolar, centrosymmetric and<i>C</i><sub>2v</sub>organoimido polyoxometalate derivatives
Ahmed Al‐Yasari, Hani El Moll, Ryan Purdy, Kevin B. Vincent, Philip Spence, Jean‐Pierre Malval, John Fielden
Abstract
and linear centrosymmetric geometries have been synthesised and studied by electronic absorption spectroscopy, electrochemistry, Z-scans (two photon absorption, TPA) and computation (DFT/TD-DFT). These reveal that POM acceptor units are an effective basis for TPA materials: the centrosymmetric bis-POM chromophores produce significant cross sections (δ up to 82 GM) from a single aryl bridge, a similar performance to larger dipolar π-systems combining carbazole or diphenylamino donors with the imido-POM acceptor. DFT/TD-DFT calculations indicate strong communication between POM and organic components is responsible for the linear and non-linear optical behaviour of these compounds, while electrochemical measurements reveal class II mixed valence behaviour resulting from an interplay of through-bond and through-space effects.