Optical, third order non-linear optical and electrochemical properties of dipolar, centrosymmetric and organoimido polyoxometalate derivatives

• Published in: Physical chemistry chemical physics : PCCP 2021-05, Vol.23 (2), p.1187-11817
• Main Authors: Al-Yasari, Ahmed, El Moll, Hani, Purdy, Ryan, Vincent, Kevin B, Spence, Philip, Malval, Jean-Pierre, Fielden, John
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp06610a

A family comprising seven arylimido-polyoxometalate (POM) hybrid chromophores (three of which are new), with linear dipolar, C 2v 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. Arylimido Lindqvist polyoxometalates (POMs) are shown to be effective acceptors for two-photon absorption. In bis-POM systems the geometry-centrosymmetric or V-shaped-strongly influences optical and non-linear optical properties.