Influencing the Optoelectronic Properties of a Heteroleptic Iridium Complex by Second-Sphere H-Bonding Interactions

The use of a new second-sphere coordination methodology for emission color tuning of iridium complexes is presented. We demonstrate that a complementary H-bonding guest molecule binding through contiguous triple H-bonding interactions can induce a shift in the emission of the iridium complex from green to blue without the need to alter the ligand structure around the metal center, while simultaneously increasing the photoluminescence quantum yield in solution. The association constant for this host-guest interaction was determined to be K_a = 4.3 × 10³ M^-1 in a solution of 2% dimethyl sulfoxide in chloroform by UV-vis titration analysis and the impact of the hydrogen bonding interaction further probed by photoluminescence, electrochemical, and computational methods. Our findings suggest that directed self-assemblies are an effective approach to influencing emission properties of phosphorescent iridium(III) complexes.