Fabrication of metal–organic salts with heterogeneous conformations of a ligand as dual-functional urease and nitrification inhibitors

Abstract

Urease inhibitors (UIs) and nitrification inhibitors (NIs) can greatly reduce nitrogen loss in agriculture soil. However, design and synthesis of an efficient and environmentally friendly dual-functional inhibitor is still a great challenge. Herein, four metal–organic salts (MOSs) based on heterogeneous conformations of the ligand N¹,N¹,N²,N²-tetrakis(2-fluorobenzyl)ethane-1,2-diamine (L), namely, [2HL]²⁺·[MCl₄]²⁻ (M = Cu, Zn, Cd, and Co), have been synthesized by the “second sphere” coordination method and structurally characterized in detail. Single crystal X-ray diffraction (SCXRD) analyses reveal that the four MOSs are 0D supramolecular structures containing [2HL]²⁺ and [MCl₄]²⁻, which are connected through non-covalent bonds. Furthermore, the urease and nitrification inhibitory activities of MOSs are evaluated, showing excellent nitrification inhibitory activity with the nitrification inhibitory rate as high as 70.57% on the 28^th day in soil cultivation experiment. In particular, MOS 1 shows significant urease inhibitory activity with half maximal inhibitory concentration (IC₅₀) values of 0.89 ± 0.01 μM (0.5 h) and 1.87 ± 0.01 μM (3 h), which can serve as a dual-functional inhibitor.