A Bis-heteroleptic Imidazolium-bipyridine Functionalized Iridium(III) Complex for Fluorescence Lifetime-based Recognition and Sensing of Phosphates.

A new Ir III based 3,3'-([2,2'-bipyridine]-5,5'-diylbis(methylene))bis(1-ethyl-1H-imidazol-3-ium) functionalized receptor Ir-1 has been synthesized for selective recognition, sensing and as a lifetime based sensor for H 2 PO 4 - and HP 2 O 7 3- in acetonitrile. An increase in the lifetime (τ) from 0.03543 μs to 0.2736 μs and 0.1323 μs in the presence of H 2 PO 4 - and HP 2 O 7 3- , respectively, among all other competitive anions establishes Ir-1 as a simple lifetime-based sensor. Furthermore, 13.7- and 8.5-fold enhancement in PL intensities of Ir-1 along with blue-shifting is seen with H 2 PO 4 - and HP 2 O 7 3- , respectively. High selectivity of Ir-1 for these two ions even in the presence of a large excess of other anions also displayed sensitive detection (LOD=0.035 μM for HP 2 O 7 3- and 0.040 μM for H 2 PO 4 - ). NMR data further suggest that the recognition of phosphates by Ir-1 is occurring through C-H⋅⋅⋅phosphate hydrogen bond (HB) interaction.