Synthesis Characterization, X‐ray Structures, and Solution Studies of Dinuclear Zinc(II) Complexes of Acyclic Schiff Base Ligands

Abstract

Dizinc(II) complexes of two acyclic Schiff‐base ligands L1– and L2– were synthesized by Schiff base condensation of 2‐[3‐(2‐formylphenoxy)‐2‐hydroxypropoxy]benzaldehyde (PL) with 1,2‐diaminopropane and 1,2‐diaminoethane, respectively, in the presence of zinc(II) salts. The isolation of a selection of 2:1 (metal:ligand) complexes of zinc(II) was carried out and conductance measurements, IR, UV/Vis absorption, and fluorescence emission spectroscopy, as well as X‐ray diffraction were employed to probe the nature of the respective complexes in both solid and solution states. The molecular structure of [Zn2L1(NO3)3] (1) complex consists of two six‐coordinate atoms, which are bridged by the deprotonated hydroxy group and one 1,3‐bridging nitrate anion. The structure of [Zn2L2(NO3)(H2O)2](NO3)2·CH3OH (3) consists of a dizinc cation and two nitrate anions as counterions. In compound 3, each zinc atom is bound to water instead of a terminal nitrate anion in a distorted octahedral arrangement. The intermetallic separation distance of Zn···Zn in 3 (3.376 Å) is slightly smaller than 1 (3.403 Å) and is similar to that found in zinc phosphotriesterase (3.5 Å). The π–π interactions between the benzene rings of adjacent molecules in 3 are stronger than in 1.

Synthesis, crystal structure and fluorescence properties of two dinuclear zinc(II) complexes incorporating tridentate (NNO) Schiff bases

“…In low coordinate complexes, zinc(II) shows Lewis acid character and is kinetically labile, thus, inter-conversion between 4, 5 and 6-coordination geometries can be fast [29,30], providing good catalytic behavior to its complexes. Zinc(II)-Schiff base complexes comprising N, O-donor sets can serve as potential biological model systems [31,32]. Moreover, these complexes have gained significant attention due to their intriguing structural features and potential applications [33].…”