An Iridium Complex as Bidentate Halogen Bond‐Based Anion Receptor Featuring an IncreasedOptical Response

We present a luminescent Ir(III) complex featuring a bidentate halogen bond donor site capable of strong anion binding. The tailor-made Ir(III)(L)₂ moiety offers a significantly higher emission quantum yield (8.4 %) compared to previous Ir(III)-based chemo-sensors (2.5 %). The successful binding of chloride, bromide and acetate is demonstrated using emission titrations. These experiments reveal association constants of up to 1.6×10⁵ M^-1. Furthermore, a new approach to evaluate the association constant by utilizing the shift of the emission was used for the first time. The experimentally observed characteristics are supported by quantum chemical simulations.