Cobaltocenium-porphyrin receptors

A tetra-cobaltocenium receptor 4 has been synthesised that is supported by a porphyrin skeleton [9]. This exhibits parallel photo- and electrochemical sensing of anions with a trend in selectivity of Cl >Br NOg. Proton NMR titrations in CD3CN showed chloride and bromide to be bound in 1 1 stoichiometry with stability constants of 860 and 820 M"1, respectively, whereas nitrate exhibited weaker binding with K=190 M"1. In the UV-vis spectrum of 4 in acetonitrile solution the Soret band (Amax=425 nm) of the porphyrin was signif-... 

Receptor 93 incorporates a zinc porphyrin backbone with four ferrocene amides [65]. This shares the design of the cobaltocenium receptor 4, except that now a zinc atom occupies the centre of the porphyrin. The Lewis acid metal centre provides an additional binding site for anion recognition. In dichloro-methane solution no significant anion-induced shifts in the lH NMR signals of the amide protons were seen in the free-base precursor of 93, whereas the... 

Studies of synthetic porphyrin-based anion receptors should form the basis for more effective sensors. Metallocene-substituted porphyrins examined by Beer and coworkers have proven successful in the solution-phase binding of ions such as chloride, bromide and nitrate." The cobaltocenium-substituted and ferrocene-substituted porphyrins (Figure 134) bind ions in solution, as shown by H NMR and electrochemical studies. The latter measurements reveal that the porphyrin and ferrocene redox... 

A new class of ferrocene (also cobaltocenium) receptors which sense anions both spectrally and electrochemically, is based upon attachment of metallocene moieties to a porphyrin skeleton. The porphyrin fragment can be simultaneously complexed by zinc [120]. 

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