Crystal structures and photophysical properties of mono- and dinuclear ZnII complexes flanked by tri­ethyl­ammonium

Two new zinc(II) complexes, C₂₁H₁₃Cl₂N₂O₃Zn·C₆H₁₆N (ZnOQ) and C₂₀H₁₄Cl₄N₂O₂Zn·2C₆H₁₆N (ZnBS), were synthesized and their structures were determined using ESI–MS spectrometry, ¹H NMR spectroscopy, and single-crystal X-ray diffraction.

Two new zinc(II) complexes, tri­ethyl­ammonium di­chlorido­[2-(4-nitro­phen­yl)-4-phenyl­quinolin-8-olato]zinc(II), (C₆H₁₆N){Zn(C₂₁H₁₃N₂O₃)Cl₂] (ZnOQ), and bis­(tri­ethyl­ammonium) {2,2′-[1,4-phenyl­enebis(nitrilo­methyl­idyne)]diphenolato}bis­[di­chlorido­zinc(II)], (C₆H₁₆N)₂[Zn₂(C₂₀H₁₄N₂O₂)Cl₄] (ZnBS), were synthesized and their structures were determined using ESI–MS spectrometry, ¹H NMR spectroscopy, and single-crystal X-ray diffraction. The results showed that the ligands 2-(4-nitro­phen­yl)-4-phenyl­quinolin-8-ol (HOQ) and N,N′-bis­(2-hy­droxy­benzyl­idene)benzene-1,4-di­amine (H₂BS) were deprotonated by tri­ethyl-amine, forming the counter-ion Et₃NH⁺, which inter­acts via an N—H⋯O hydrogen bond with the ligand. The Zn^II atoms have a distorted trigonal–pyramidal (ZnOQ) and distorted tetra­hedral (ZnBS) geometries with a coord­ination number of four, coordinating with the ligands via N and O atoms. The N atoms coordinating with Zn^II correspond to the heterocyclic nitro­gen for the HOQ ligand, while for the H₂BS ligand, it is the nitro­gen of the imine (CH=N). The crystal packing of ZnOQ is characterized by C—H⋯π inter­actions, while that of ZnBS by C—H⋯Cl inter­actions. The emission spectra showed that ZnBS complex exhibits green fluorescence in the solid state with a small band-gap energy, and the ZnOQ complex does exhibit non-fluorescence.