The concentration of Cu²⁺ in blood is altered by many diseases. A noninvasive method for detecting Cu²⁺ would be useful to study its metabolism and understand its biological role.

Shin Aoki, Tokyo University of Science, Japan, and colleagues developed ¹¹B NMR probes for the detection of d-block metal ions. They synthesized a nido–o-carborane compound that contains a chelator unit, TriMEDA (pictured). As the affinity of TriMEDA for Cu²⁺ is higher than its affinity for Mn²⁺, Fe²⁺, or Zn²⁺, the Cu²⁺-promoted decomposition of nido–o-carborane to release B(OH)₃ is accelerated considerably even at room temperature and under physiological conditions.

The released B(OH)₃ can be easily and selectively detected by ¹¹B NMR spectroscopy and magnetic resonance imaging (MRI). The cellular uptake of the nido–o-carborane compound is very low, which makes it suitable for this method. Moreover, even catalytic amounts of Cu²⁺ (0.1 equiv.) can be detected.

• ¹¹B NMR/MRI Sensing of Copper(II) Ions In Vitro by the Decomposition of a Hybrid Compound of a nido–o-Carborane and a Metal Chelator,
  Tomohiro Tanaka, Rikita Araki, Takaomi Saido, Ryo Abe, Shin Aoki,
  Eur. J. Inorg. Chem. 2016.
  DOI: 10.1002/ejic.201600346