Counteranion-driven self-assembly of di- and tetra-nuclear Zn(II) single‐armed salamo‐type complexes

Abstract

Di- and tetra-nuclear Zn(II) complexes, [Zn2(L)(µ-OAc)(CH3OH)]·CH3OH (1) and [Zn4(L)2(OMe)2]·2CH3COCH3·CH3OH (2) have been successfully self-assembled by the reaction of a single‐armed salamo‐type ligand (H3L), Zn(OAc)2·2H2O and Zn(NO3)2·6H2O, respectively. In the ligand H3L, tetradentate N2O2 donor part of pocket I and NO2 donor part of pocket II are designed to bond Zn(II) atoms, then unusually structural complexes were obtained by counteranion-driven self-assembled. Both complexes 1 and 2 are characterized by elemental analyses, IR spectra, UV-Vis spectra and single crystal X-ray diffraction. All of the Zn(II) atoms in complexes 1 and 2 are penta-coordinated, but highly distinct configurations are obtained because of the introduction of two kinds of counter-anions. In complex 1, μ-OAc− counter-anion connects the two Zn(II) atoms in one ligand. In complex 2, μ-OMe− counter-anions link the Zn(II) atoms within two ligand molecules and the structure of complex 2 is more complicated. What's more, in complex 1, all Zn(II) atoms have the geometries of distorted trigonal bipyramid, while in complex 2, all Zn(II) atoms have the geometries of distorted square pyramid. There are obvious π···π stacking interactions existing in complexes 1 and 2, which are quantitatively valued by Hirshfeld surfaces analyses. Fluorescence properties are also investigated.