Synthesis, structure and blue-light emission of a zero-dimensional zinc halide with the 4-(4-chlorophenyl)pyridinium cation

Exploring blue emission lead-free halides with high photoluminescence quantum yields (PLQYs) is a significant and challenging issue for luminescent materials. Herein, a zero-dimensional (0D) organic-inorganic hybrid halide, namely, bis[4-(4-chlorophenyl)pyridinium] tetrabromidozincate, (C₁₁H₉ClN)₂[ZnBr₄] or [HCPP]₂[ZnBr₄] [CPP is 4-(4-chlorophenyl)pyridine], was synthesized through acid solution evaporation. The compound crystallizes in the monoclinic space group C2/c. The asymmetric unit consists of a [ZnBr₄]^2- dianion cluster and two monoprotonated [HCPP]⁺ cations. The [ZnBr₄]^2- unit presents an almost undistorted tetrahedral geometry. The [HCPP]⁺ cations adopt nearly coplanar conformations with small dihedral angles of 5.05 (3)°; there are relatively strong π-π interactions between adjacent [HCPP]⁺ cations due to slipped parallel packing, with a distance of 3.81 (1) Å. Significantly, this halide exhibits highly efficient blue-light emission (385-500 nm) with a PLQY of 56.35%.