Two new fluorescent Zn²⁺ sensors exhibiting different sensing mode with subtle structural changes

Abstract

Two novel receptors HL-1 and HL-2 without and with hydroxyl groups were designed and synthesised. Both receptors showed highly selective coordination towards Zn²⁺ and exhibited diverse sensing behaviour due to the structural variations. HL-1 showed monotonous ‘turn-on’ response towards Zn²⁺ while HL-2 displayed highly Zn²⁺ sensitive ‘turn on’ and ‘ratiometric’ properties. Detailed Job plot experiment, single crystal data, ¹H NMR, ESI-MS, UV–vis and density functional theory calculation studies were conducted to understand the binding modes of HL-1 and HL-2 with Zn²⁺. These results revealed the binding stoichiometric ratio between receptors and Zn²⁺ were 1:1 with low detection limits and high binding constants.

Two novel receptors HL-1 and HL-2 without and with hydroxyl groups were designed and synthesised via TCR reaction. Both of them showed selective coordination to Zn²⁺ ions but exhibited incongruent sensing mode due to structural variations. HL-1 showed monotonous ‘turn-on’ whereas HL-2 displayed highly sensitive ‘turn on’ and ‘ratiometric’ properties towards Zn²⁺.

Keywords:

• Fluorescence
• chemosensor
• recognition
• zinc
• conformation

Acknowledgements

The authors are grateful for financial support from the National Natural Science Foundation of China (NO.21206016) and the Fundamental Research Funds for the Central Universities (DUT14LK08).