A Dual-emission Strategy for a Wide-range Phosphorescent Color-tuning of a Crystalline-state Molecular Cluster [Cu4I4(2-Bzpy)4] (2-Bzpy = 2-Benzylpyridine)

We demonstrate herein a novel molecular strategy for crystalline-state luminescence color tuning in the entire visible region by adopting thermochromic dual phosphorescence of coordination complexes. As crystals, a new cubane-type tetranuclear copper(I)-idodido complex with 2-benzylpyridine N-donor ligands 1 shows a sequential phosphorescence color change from yellow (298 K) to red and finally to blue (78 K) in the crystalline state across the color space area, in which relative intensity ratio of the triplet cluster-centered (3CC) and triplet charge transfer (3CT) bands in the dual-emission is reversibly controlled with temperature.