The selective binding of ⁹⁹Tc pertechnetate (⁹⁹TcO₄ ⁻) in water is a big challenge. Recently, our group reported on the p-xylyl aza-cryptand, as the first molecular receptor for ⁹⁹TcO₄ ⁻ in aqueous solution. Here, we show that the introduction of a fluorescent unit in the azacryptand's framework leads to a new molecular system, able to selectively recognize and sense the pertechnetate anion at μM concentration. In water at pH 2, where the cage is in the hexaprotonated form, pertechnetate recognition is signalled by the quenching of the receptor's emission. Noticeably, environmentally ubiquitous anions, such as chloride, nitrate and sulfate do not interfere in the sensing, as they have no effect on our chemo-sensor's fluorescence. These unprecedented results are promising for the development of simple and smart devices for the recovery of ⁹⁹TcO₄ ⁻ from contaminated aqueous solutions.

Bis-arene complexes of technetium represent a fundamental class of organometallic compounds. Due to complex synthetic routes, no detailed insights into their properties have been reported so far. Reacting [⁹⁹TcO₄]⁻ with arenes in the exclusive presence of AlCl₃ gives highly stable [⁹⁹Tc(arene)₂]⁺ in good yields. These complexes have extraordinarily high stabilities, where oxidation is found to occur at potentials higher than +1.3 V and reduction at potentials below −2 V vs. Fc/Fc⁺. The ^99mTc analogues are similarly synthesised by applying a novel ionic liquid extraction pathway. Complexes of ^99mTc with suitably functionalized arenes will represent new building blocks for bioorganometallic pharmaceuticals in molecular imaging.