Three zinc iodide complexes based on phosphane ligands: syntheses,structures, optical properties and TD–DFT calculations

Three zinc iodide complexes based on phosphane ligands, namely diiodidobis(triphenylphosphane‐κP)zinc(II), ZnI₂(C₁₈H₁₅P₂)₂], ( 1 ), diiodidobistris(4‐methylphenyl)phosphane‐κP]zinc(II), ZnI₂(C₂₁H₂₁P₂)₂], ( 2 ), and bis(diphenylphosphoryl)methane‐κ²O,O′]zinc(II) tetraiodidozinc(II), Zn(C₂₅H₂₂O₂P₂)₃]ZnI₄], ( 3 ), have been synthesized and characterized. Single‐crystal X‐ray diffraction revealed that the structures of ( 1 ) and ( 2 ) are both mononuclear four‐coordinated ZnI₂ complexes containing two monodentate phosphane ligands, respectively. Surprisingly, ( 2 ) spontaneously forms an acentric structure, suggesting it might be a potential second‐order NLO material. The crystal structure of complex ( 3 ) is composed of two parts, namely a Zn(dppmO₂)₃]²⁺ cation dppmO₂ is bis(diphenylphosphoryl)methane] and a ZnI₄]^2? anion. The UV–Vis absorption spectra, thermal stabilities and photoluminescence spectra of the title complexes have also been studied. Time‐dependent density functional theory (TD–DFT) calculations reveal that the low‐energy UV absorption and the corresponding light emission both result from halide‐ligand charge‐transfer (XLCT) excited states.