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

Abstract

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 = 4.3 × 10 M 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.

Thiourea and Guanidine Compounds and Their Iridium Complexes in Drug‐Resistant Cancer Cell Lines: Structure‐Activity Relationships and Direct Luminescent Imaging

“…We have shown that the seemingly minor change of an S to NH can have significant effects upon the biological action of the molecules. This may relate to changes in conformation of the molecules due to intramolecular hydrogen bond formation . In the case of the iridium complexes, the toxicity trend was reversed, but we were able to observe a dramatic difference in subcellular distribution of the complexes according to the S/NH substitution.…”

“…We are currently investigating guanidine‐ and thiourea‐based molecules as components in advanced organic LED materials through formation of luminescent iridium complexes . Iridium complexes themselves are of great interest as potential cancer therapeutics because they generate a 3D scaffold, enabling structural diversity beyond the ‘flatter’ organic molecules or platinum complexes used in cancer therapy; they offer an opportunity for simultaneous imaging due to their rich and tunable luminescence properties; and they offer an opportunity for photogeneration of singlet oxygen within cells .…”

“…Portions of these compounds were converted to the corresponding guanidines by reaction with mercury(II) oxide and methanolic ammonia in chloroform to give 1N to 4N in 40–65 % yield . Two iridium complexes based on these systems were previously prepared by reacting 2S and 2N separately with [Ir(ppy) 2 Cl] 2 in toluene in the presence of potassium carbonate, giving bright yellow powders Ir ‐ 2S and Ir ‐ 2N in 53 % and 44 % yield respectively as racemates (confirmed for Ir ‐ 2N by single crystal X‐ray diffraction) . All new compounds were characterised by 1 H and 13 C NMR, EI‐MS, and elemental analysis (see Supporting Information).…”

RuII and IrIII Complexes Containing ADA and DAD Triple Hydrogen Bonding Motifs: Potential Tectons for the Assembly of Functional Materials

“…In particular, studies on Ru II and Os II ‐containing bpy ligands derivatized by nucleobases have been shown to form triple hydrogen bonded heterosynthons within which the emission of the ruthenium center is quenched by the osmium center . Triple hydrogen bonding interactions have also been shown very recently to be able to non‐covalently tune the emission properties of an Ir III ‐based system . Another recent report has also highlighted the ability of hydrogen bonding to facilitate photocatalysis reactions in Ir III complexes .…”

“…[10] Triple hydrogen bonding interactions have also been shown very recently to be ablet o non-covalently tune the emission properties of an Ir III -based system. [11] Another recentr eport has also highlighted the ability of hydrogen bonding to facilitate photocatalysis reactions in Ir III complexes. [12] There are fewer reports concerning the incorporation of such centers into functional materials.…”