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

Abstract

Reactions of hydrated zinc(II) trifluoroacetate and sodium azide with two tridentate Schiff bases HL 1 (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-chlorophenol) and HL 2 (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-bromophenol) under the same reaction conditions yielded two dinuclear isostructural zinc(II) complexes, [Zn(L 1 )(N 3 )] 2 (1) and [Zn(L 2 )(N 3 )] 2 (2), respectively. The complexes were characterized systematically by elemental analysis, UV-Vis, FT-IR and 1 H NMR spectroscopic methods. Single crystal X-ray diffraction studies reveal that each of the dinuclear complexes consists of two crystallographically independent zinc(II) ions connected by double bridging phenoxides. All zinc(II) ions in 1 and 2 are surrounded by similar donor sets and display distorted square pyramidal coordination geometries. The ligands and complexes reveal intra-ligand 1 (π→π*) flourescence. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates their potential to serve as photoactive materials.

The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review

“…In 2016, Shyamapada Shit and coworkers [104] presented two tridentate salen Schiff base ligands with two different halogen substituents in combination with azide as auxiliary ligands (Figure 6). The structure-property relationships of the coordination complexes were examined.…”

Anion Effect on the Formation of Zinc‐Salicyaldimine Compounds in Neutral and Anionic Complex Forms: Synthesis, Characterization, 1H NMR Studies, and Photophysical Properties

“…This property shows similarity with other salicyaldimine derivatives and can be interpreted by a photoinduced electron transfer (PET) process due to the presence of lone pair of electrons of the donor atom in the salicyaldimine ligand, thus quenching the fluorescence of the salicyaldimine compounds. [36][37][38] On the other hand, zinc-salicyaldimine compounds 1 and 2 emitted strong blue-light (λ em = 472 nm, Φ PL = 0.255) and green-light (λ em = 504 nm, Φ PL = 0.385) fluorescence, respectively, in solid-state (Figures 6b-6d), which are tentatively ascribed to ILCT emission of the compounds [31,36,39] due to that divalent zinc ion with stable d 10 electronic configuration is redox-inert to prevent metal-based charge transfers. [40] In comparison to Hsal-3-PhCN, the fluorescence emissions for 1 and 2 are blue-shifted by 82 and 50 nm, respectively, in wavelength and enhanced by about 2.7 and 4.0 times, respectively, in quantum yield.…”

“…Upon complexation, an excitate state centered on the bonded salicyaldimine ligand might be lowering in energy, resulting in a qualitative blue shift of the fluorescence emission maximum. [20,21,39] Meanwhile, complex formation with the chelation of azomethine nitrogen and phenolate oxygen atoms causes chelation enhanced fluorescence (CHEF) effect [38,41,42] and inhibits the C=N isomerization. [43][44][45][46] This significantly not only reduces the PET quenching effect but also increases structure rigidity to reduce the probability of non-radiative relaxation process by vibrational and rotational decay.…”

Design, preparation, physicochemical characterization, structural conformational, biological evaluation, and DNA interaction for some new benzimidazole complexes

“…Design as well as the development of pyrimidine and imidazole derivatives through several donor atoms is a green field toward the growth of inorganic chemistry 1,2 . The choice of proper amines as well as exchanged aromatic groups for the preparation of the studied ligand is related to the formation of several features like electronic, steric, catalytic as well as biomedical potential 3–5 . Their acceptance is devised from the simplicity with which they can be prepared, their adaptability as well as their chelation ability through metal ions.…”