Di-nuclear Cu(II) complex bearing guanidinium arms for sensing pyrophosphate and monitoring the activity of PPase

In this work, we reported a di-nuclear Cu(II) complex bearing double guanidinium arms for sensing pyrophosphate (PPi) with high selectivity and sensitivity. Using pyrocatechol violet (PV) and esculetine as colorimetric and fluorescent indicators respectively, the copper complex-indicator ensemble exhibited remarkable colorimetric and fluorescent changes upon addition of PPi in the aqueous solution. Comparing to the di-nuclear Cu(II) complex without guanidinium arms, the introduction of positively-charged guanidinium groups lead to 2.6 × 10⁴-fold enhancement on the binding affinity toward pyrophosphate (PPi). The ensemble containing copper complex and PV was further used to monitor the hydrolysis of PPi catalyzed by pyrophosphatase (PPase).