Molecular Suppression of the Pimerization of Viologens (=4,4′‐Bipyridinium Derivatives) Attached to Nanocrystalline Titanium Dioxide Thin‐Film Electrodes

Twelve viologens, i.e., 4,4′‐bipyridinium derivatives 1 – 12 , were examined for their use as electrochromic material when attached to nanocrystalline titanium dioxide thin‐film electrodes. Eight of these ( 1 – 4 , 7 – 8 , 10 , and 12 ) are new, and their synthesis is included. The modifier compounds consist of one to four bipyridinium subunits with linear or dendritic architecture, equipped with one to three TiO₂‐anchoring phosphonate groups. They are tailored for high electrochromic dynamics (large absorbance change upon reduction) and low extent of pimerization (=charge‐transfer (CT) complexation of viologen cation radicals). A new graphical method is presented for the discrimination of simple dilution phenomena and more complex structural effects on the extent of pimerization in the surface‐attached viologen layer.     

1,7-Disubstituted boron dipyrromethene (BODIPY) dyes: synthesis and spectroscopic properties

1,7-Dihalogenated boron dipyrromethene dyes were successfully synthesized and substituted, thus providing an entry to the final, elusive reactivity pattern. The spectroscopic properties of 1,7-disubstituted BODIPY dyes were studied and are discussed as a function of their structure.     

Inference for nonstationary time series of counts with application to change-point problems

Annals of the Institute of Statistical Mathematics - We consider an integer-valued time series $$(Y_t)_{t\in {\mathbb {Z}}}$$ where the model after a time $$k^*$$ is Poisson autoregressive with the...