Synthesis, structures, luminescence and thermal stability of Visible/NIR emitting binuclear azomethine-Zn(II) complexes

• Main Authors: Sarwar, Aziza, Saharin, Siti Munirah, Bahron, Hadariah, Alias, Yatimah
• Format: Article
• Published: Elsevier 2020
• Subjects: Q Science (General); QD Chemistry
• Online Access: http://eprints.um.edu.my/25123/; https://doi.org/10.1016/j.jlumin.2020.117227

A series of binuclear azomethine-Zn(II) complexes was successfully synthesized from 4,4-diaminodiphenylsulphide derived Schiff bases, N,N-bis-(3,4-dihydroxybenzaldehyde)-4,4-diaminodiphenylsulphide (L1), N,N-bis-(5-nitrosalicylidene)-4,4-diaminodiphenylsulphide (L2), N,N-bis-(5-chlorosalicylidene)-4,4-diaminodiphenylsulphide (L3). The compounds were characterized through single crystal X-ray diffraction analysis, FT-IR, 1H NMR,13C NMR, energy dispersive X-ray diffraction (EDX), UV–Visible and photoluminescence spectroscopy. Single crystal X-ray diffraction analysis manifested that in the binuclear ZnL3 complex, two zinc ions bridge two Schiff bases with each metal centre adopting a distorted tetrahedral geometry, through coordination with two phenolate oxygen atoms and two azomethine nitrogen atoms. Each L3 ligand bonds two Zn(II) centres on different sides of the metals where the ligand flipped over to the opposite side around the S atom creating a twist. Photophysical properties of the synthesized compounds were explored in solid and solution states at room temperature. In solid state, the complexes revealed emissive properties in the visible and near infra-red (NIR) regions, with large Stoke's shift (Δλ) of 260–385 nm with respect to absorption, exhibiting emission in visible region (585 nm) both for ZnL2 and ZnL3 and dual emissive peaks in the NIR region (710 nm, 1199 nm) for ZnL1. Whereas, emissions in solution state (DMF) with lower intensity occurred at 465–545 nm. All complexes were subjected to thermogravimetric analysis with ZnL2 showing the highest thermal stability of up to 342 °C before undergoing decomposition. The good solid state emission properties illustrated that the complexes featured their potential as promising cost effective solid state photoactive materials. © 2020 Elsevier B.V.