Phosphorescent cyanide sensor based on a 2-phenylpyridine(ppy)-type cyclometalated Ir(III) complex bearing dimesitylboron group with concentration distinguishing ability

With a 2-phenylpyridine(ppy)-type cyclometalated Ir(III) complex with –B(Mes)₂ group Ir–B, the CN^¯ ions can bind effectively with the boron atom in the –B(Mes)₂ group to furnish CN^¯ sensing ability through inducing phosphorescence changing of the concerned Ir(III) complex. Uniquely, with increasing the added amount of CN^¯ ions, loose and tight binding between CN^¯ and boron atom in the –B(Mes)₂ group of Ir–B can occur in sequence to destabilize metal-to-ligand charge transfer (MLCT) excited states and then form new MLCT excited states in Ir–B. Accompanying this process, the red phosphorescence of Ir–B can be effectively quenched by adding CN^¯ ions, while new yellow and green emission bands can appear in sequent with increasing the amount of added CN^¯ ions, showing CN^¯ sensing behavior with unique concentration distinguishing ability. In addition, the new phosphorescent CN^¯ sensor can possess detection limit (DL) as low as 4.3 × 10⁻⁶ M and good selectivity to the CN^¯ ions. Clearly, these results can provide important information for developing new CN^¯ sensors with high performances.