Copper(I) bromide organic-inorganic zwitterionic coordination compound with new type of core: structure, luminescence properties, and DFT calculations
A new organic-inorganic Cu(I) bromide complex based on the triple protonated tris(2-pyridyl)phosphine (HPy)3P, [(HPy)3PCu2Br5] (1), has been synthesized by a straightforward reaction in solution or by modification of the [Cu2Br2(Py3P)2] complex using the hydrobromic acid. At 77 K, the solid complex 1 exhibits the near infra-red photoluminescence with λmax = 680 nm related to 3(M+X)LCT. The emission of 1 rapidly decreases with the temperature increasing and is absent already at 200 K due to the thermal quenching with the small energy barrier ∆E ≈ 590 cm-1. The photophysical results are in good agreement with TD-DFT calculations showing that in the ground state the cuprophilic interaction between copper ions is absent in spite of the short Cu…Cu distance. After annealing of the complex 1 at 120 °C, the photoluminescence is appeared with λmax = 640 nm at 300 K. The complex 1 has a luminescence response on the ammonia gas consisting in the appearance of the luminescence with λmax = 520 nm followed by the gradually enhancement of the luminescence intensity.