Mechanochemical Synthesis and Physicochemical Characterization of a Nickel (II)–Ethylenediamine Coordination Compound

Abstract

A nickel(II)–ethylenediamine coordination compound (Ni–EDA CC) was synthesized via a 
solvent-free mechanochemical approach as a sustainable alternative to conventional 
solvothermal and solution-based synthetic routes. Stoichiometric quantities of nickel(II) 
chloride hexahydrate and ethylenediamine were subjected to mechanical grinding, with a 
minimal amount of methanol employed as a liquid-assisted grinding (LAG) agent to facilitate 
coordination and enhance product formation. The reaction was accompanied by a distinct color 
transformation from pale green to violet-purple, providing preliminary evidence for the 
formation of a new nickel(II) coordination compound. The synthesized material was 
comprehensively characterized using Fourier transform infrared (FTIR) spectroscopy, 
powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive 
X-ray (EDX) spectroscopy. FTIR analysis revealed characteristic shifts in the N–H stretching 
vibrations together with significant changes within the fingerprint region, confirming 
coordination between the nickel(II) center and ethylenediamine ligand. Powder XRD patterns 
indicated the formation of a predominantly microcrystalline phase, demonstrating successful 
crystallization of the coordination compound under mechanochemical conditions. SEM 
micrographs showed agglomerated microcrystalline particles with irregular morphology, 
reflecting the solid-state nature of the synthesis process. Elemental composition determined 
by EDX confirmed the presence of nickel, nitrogen, carbon, and residual chlorine within the 
synthesized product, supporting the proposed chemical composition while indicating 
incomplete removal or incorporation of chloride species. Overall, the findings demonstrate 
that mechanochemical synthesis represents an efficient, environmentally benign, and energyconscious strategy for producing nickel(II)–ethylenediamine coordination materials. 
Nevertheless, the relatively high residual chlorine content detected by EDX warrants further 
investigation to optimize reaction conditions, improve product purity, and better understand 
the coordination environment and composition of the resulting material.