| Abstract
| - The synthesis, electrochemical, electronic, and cation sensing properties of the ruthenocene-terminated2-aza-1,3-butadiene 2, linear ferrocene−ruthenocene dyads 3 and 5, and the new structural motifs diaza[4.4]ruthenocenophane 7 and mixed ferrocene and ruthenocene metallocenophanes 8 and 10 are presented.The properties of these compounds have been systematically varied by introducing the ferrocene andruthenocene moieties at the 1- or 4-position of the unsymmetrical 2-aza-1,3-butadiene bridge.Spectroelectrochemical studies of compounds 3 and 8, in which the ruthenocene unit appended at the1-position of the bridge exhibits a rather unusual electrochemical behavior, revealed the presence oflow-energy bands in the near-infrared (NIR) region in the partially oxidized forms, at 1070 and 1163nm, respectively, which indicate the existence of intramolecular charge transfer between the iron and theruthenium centers. The electrochemical and intermetallic charge-transfer (MMCT) studies (HAB, λ and αparameters) indicate that the 3•+ and 8•+ systems belong to the Class II classification for a mixed-valencecompound. In addition, the low-energy (LE) band of the absorption spectra of all compounds prepared,except compound 10, are red-shifted by complexation with divalent Mg2+, Zn2+, Cd2+, Hg2+, and Ni2+metal ions. For open dyads, biruthenocene compound 2 exhibited the higher red-shift by 92 nm, whereasfor closed compounds the [4.4]ruthenocenoferrocenophane 8 displayed a remarkable red-shift by about180 nm for Zn2+, Cd2+, Hg2+, and Ni2+ metal ions and by about 146 nm for Mg2+ cation. The changesin the absorption spectra are accompanied by dramatic color changes which allow the potential for “nakedeye” detection. The experimental data and conclusions are supported by DFT computations.
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