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A family comprising seven arylimido-polyoxometalate (POM) hybrid chromophores (three of which are new), with linear dipolar, C2v 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. [ABSTRACT FROM AUTHOR]

The readily available complex 1,1-dibromo-2-ferrocenylethyleneprovides a convenient entry point for the preparation of a wide rangeof cross-conjugated 1,1-bis(alkynyl)-2-ferrocenylethenes through simplePd(0)/Cu(I)-mediated cross-coupling reactions with 1-alkynes. Theferrocene moiety in compounds of the general form FcCHC(CCR)2is essentially electronically isolated from the cross-conjugatedπ system, as evidenced by IR and UV–vis spectroelectrochemicalexperiments and quantum chemical calculations. In contrast to theother examples which give stable ferrocenium derivatives upon electrochemicaloxidation, the aniline derivatives [FcCHC(CCC6H4NH2-4)2]+and[FcCHC(CCC6H4NMe2-4)2]+proved to be unstable on the time scaleof the spectroelectrochemical experiments, leading to passivationof the electrode surface over time. There is no significant thermodynamicstabilization of the radical anion [FcCHC(CCC6H4NO2-4)2]−relative to the neutral and dianionic analogues, although the dianion[FcCHC(CCC6H4NO2-4)2]2–could be studied as a relatively chemicallystable species and is well described in terms of two linked nitrophenylradicals. The capacity to introduce a relatively isolated point chargeat the periphery of the cross-conjugated π system appears tomake these complexes useful templates for the construction of electrochemicallygated quantum interference transistors. [ABSTRACT FROM AUTHOR]

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.