Copper(i) halide polymers derived from tris[2-(pyridin-2-yl)ethyl]phosphine: halogen-tunable colorful luminescence spanning from deep blue to green

A series of isostructural 1D coordination polymers (CPs), [Cu4X4(L)2]n where X = Cl (1), Br (2), I (3), have been synthesized via the reaction of Cu(I) halides with tris[2-(pyridin-2-yl)ethyl]phosphine (L). 1D chains of these CPs are built up by alternating stair-step [Cu4X4] modules bridged by “PyCH2CH2P” ligand arms. At ambient temperature, the titled polymers exhibit strong luminescence, the color of which is tuned by the halogen atoms spanning from deep-blue (λmax = 448 nm, for X = I) to green (λmax = 520 nm, for Cl) through cyan (λmax = 490 nm, for Br). The emission lifetimes fall close to the 13–24 μs region at 300 K, and PL quantum yields (45–62%) are the highest among yet known emitters bearing stair-step [Cu4X4] units. A combination of spectral studies and (TD)DFT computations suggests that the emission of the CPs represents phosphorescence stemmed from the 3(M + X)LCT excited states.