From a blue to white to yellow emitter: a hexanuclear copper iodide nanocluster

Highly emissive copper( i ) halide nanoclusters showing thermally activated delayed fluorescence (TADF) have been paid much attention, but rarely reported so far. Herein, a hexanuclear copper( i ) iodide cluster containing a tridentate N∧P∧N ligand, [Cu 6 I 6 (ppda) 2 ] {ppda = 2-[2-(dimethylamino)phenyl(phenyl)phosphino]- N , N -dimethylaniline}, was synthesized. All six copper atoms are four-coordinate, including four CuPNI 2 and two CuI 4 units. This complex exhibits intense white emission in the powder state at room temperature and shows a peak at a wavelength of 535 nm ( Φ PL = 0.36) with a microsecond lifetime ( τ = 4.4 μs). Emission colors can be largely tuned from blue to white to yellow, from the crystal to powder to film state at 297 K. The emission of [Cu 6 I 6 (ppda) 2 ] originates from a combination of MLCT and XLCT transitions. This complex showed good thermal stability. A solution-processed, nondoped device of complex [Cu 6 I 6 (ppda) 2 ] exhibits stable yellow emission with the CIE coordinates ( x , y ) of (0.43, 0.51). [Cu 6 I 6 (ppda) 2 ] also shows reasonable photocatalytic H 2 evolution activity under visible-light irradiation. Emission colors can be largely tuned from blue to white to yellow, by changing the solid state from crystal to powder to film.