Interplay of Supramolecular Organization, Metallophilic Interactions, Phase Changes, and Luminescence in Four Polymorphs of Ir^I(CO)₂(OC(CH₃)CHC(CH₃)N(<i>p</i>-tol))

Four polymorphs of IrI(CO)2(OC(CH3)CHC(CH3)N(p-tol)) have been characterized by single crystal X-ray crystallography. While all contain the same molecular unit with no significant structural variations within the molecules, all show different degrees of metallophilic interactions between the planar molecules. Three of these (the amber, the pale yellow, and the orange forms) are stable at room temperature, while the fourth, the L. T. orange form, is only obtained by cooling the orange polymorph. At 77 K, the amber, pale yellow, and L. T. orange polymorphs show intense luminescence. The variations in the luminescence among the polymorphs are considered in the context of the structural differences between them and the nature of the metallophilic interactions between the iridium centers. These results demonstrate how subtle variations in molecular organization can affect the physical properties of planar d8 transition metal compounds, which are an important class of lumiphores.