Cu(I) complexes designed on 2-pyrimidylphosphine and 1,4-dicyanobenzene: Synthesis and thermally activated delayed fluorescence

Abstract

One-dimensional coordination polymer [Cu2L3(DCB)]n(PF6)2n (1) and dinuclear complex [Cu2L6(DCB)](PF6)2 (2) have been synthesized through three-component reaction between [Cu(MeCN)4]PF6, diphenyl(2-pyrimidyl)phosphine (L) and 1,4-dicyanobenzene (DCB). The DCB ligand within these products acts as a N,N’-linker connecting two [CuL3]+ cations in 2, and assembling the alternating [Cu2L3]2+ units of 1 into a 1D chain. At ambient temperature, both 1 and 2 emit green and turquoise luminescence, respectively, with quantum yields of 16 and 71%. At 300 K, the emission lifetimes of 1 and 2 are 21 and 14 μs, and upon cooling to 77 K, they increase to 600 and 1420 μs, accordingly. Basing on temperature-dependent photophysical data and DFT computations, the emission of the title complexes is tentatively ascribed to thermally activated delayed fluorescence. The Δ(S1–T1) energy gaps for 1 and 2 are estimated to be 670 and 1250 cm−1.