Copper(I) Iodide Complexes Derived from <i>N</i>-Alkyl-1,3,5-triaza-7-phosphaadamantanes: Synthesis, Crystal Structures, Photoluminescence, and Identification of the Unprecedented {Cu₃I₅}²⁻ Cluster

The new luminescent mononuclear [CuI(PTA-Me)3](I)3 (1) and [CuI(PTA-Et)3](I)3 (2) and trinuclear [Cu3I2(μ-I)(μ3-I)2(PTA-Pr)2] (3) copper(I) complexes have been easily prepared, in aqueous medium and at ambient conditions, from copper(II) nitrate and N-methyl-, N-ethyl-, and N-propyl-1,3,5-triaza-7-phosphaadamantane iodides [PTA-R]I (R = Me, Et, nPr), respectively. They have been fully characterized by IR, 1H and 31P NMR spectroscopies, FAB-MS+, and elemental and single-crystal X-ray diffraction analyses, the latter featuring a novel type of tricopper iodide {Cu3I2(μ-I)(μ3-I)2}2− cluster. Compounds 1, 2, and 3 exhibit distinct photoluminescence in the solid state, DMSO solution, and frozen glass, thus extending to copper centers the application (previously limited to only Au complexes) of 1,3,5-triaza-7-phosphaadamantane (PTA) or any of its derivatives toward the preparation of luminescent organometallic materials. In addition, complex 3 widens the cluster chemistry of PTA, providing the first example of a metal halide cluster bearing a cage-like PTA core.