Crystal structures and photophysical properties of mono- and dinuclear Zn^II complexes flanked by triethylammonium

Two new zinc(II) complexes, tri-ethyl-ammonium di-chlorido-[2-(4-nitro-phen-yl)-4-phenyl-quinolin-8-olato]zinc(II), (C₆H₁₆N){Zn(C₂₁H₁₃N₂O₃)Cl₂] (<b>ZnOQ</b>), and bis-(tri-ethyl-ammonium) {2,2'-[1,4-phenyl-enebis(nitrilo-methyl-idyne)]diphenolato}bis-[di-chlorido-zinc(II)], (C₆H₁₆N)₂[Zn₂(C₂₀H₁₄N₂O₂)Cl₄] (<b>ZnBS</b>), 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-nitro-phen-yl)-4-phenyl-quinolin-8-ol (<b>HOQ</b>) and <i>N</i>,<i>N</i>'-bis-(2-hy-droxy-benzyl-idene)benzene-1,4-di-amine (<b>H₂BS</b>) were deprotonated by tri-ethyl-amine, forming the counter-ion Et₃NH⁺, which inter-acts <i>via</i> an N-H⋯O hydrogen bond with the ligand. The Zn^II atoms have a distorted trigonal-pyramidal (<b>ZnOQ</b>) and distorted tetra-hedral (<b>ZnBS</b>) geometries with a coord-ination number of four, coordinating with the ligands <i>via</i> N and O atoms. The N atoms coordinating with Zn^II correspond to the heterocyclic nitro-gen for the <b>HOQ</b> ligand, while for the <b>H₂BS</b> ligand, it is the nitro-gen of the imine (CH=N). The crystal packing of <b>ZnOQ</b> is characterized by C-H⋯π inter-actions, while that of <b>ZnBS</b> by C-H⋯Cl inter-actions. The emission spectra showed that <b>ZnBS</b> complex exhibits green fluorescence in the solid state with a small band-gap energy, and the <b>ZnOQ</b> complex does exhibit non-fluorescence.