No abstract

[Ni( salen)] complexes bearing different crown ether receptors were electropolymerized to give films whose voltammetric signatures responded to Ba2+. In line with DFT calculations, X-ray absorption spectroscopy (XAS) near the Ni K-edge showed the nickel local environment in the monomers and their corresponding polymers (in the presence or absence of barium) to be identical. However, the expectation of crown size-dependent barium local environment (based on geometry and donor atom availability) was not found. XAS near the Ba K-edge showed that Ba2+ in the films coordinated to only two oxygen donors, irrespective of crown size. This surprisingly low coordination number (compared to solution species) is accompanied by a higher barium/crown ratio than the anticipated 1:1 stoichiometry. The implications of these effects for design and performance of sensors based on metal ion recognition chemistry are discussed.

The latter values correspond to less than 10 % of the overall magnitude of the third-order susceptibility, |χ 3 |, which is the result of the absence of electronic transitions near λ inc = 1064 nm. For the group of Ni II complexes, the highest n 2 I values are exhibited by the complexes with aromatic diimine bridges and large