Polymorphism and structural variability of Ni(II)-water complexes derived from a compartmental Schiff base ligand

The Ni(II) complexes were synthesized using a flexible compartmental ligand, and their crystal structures were successfully determined by X-ray single-crystal analysis. IR spectroscopy results indicate the involvement of the nitrogen donor atoms of azomethine (νC=N) and phenolic oxygen atoms in coordinating with the Ni(II) ions. The Ni(II)-water complex crystallizes in the monoclinic system with space groups P2₁/n , P2₁/c , and P2₁ , and Z = 4. However, nickel(II)–water compound exhibits structural variability and lacks a predominant structure at 273 K and 313 K (Circular dichroism spectroscopy (CD)). Paramagnetic 1 H NMR spectroscopy shows that the peaks for nickel(II)–water complex is significantly broadened due to paramagnetic resonance effects. The optical properties of nickel(II)–water complex exhibits significant shifts in their UV–Vis absorption spectrum in both solution and solid states. UV–Vis spectra recorded in various solvents, considering their coordinating and non-coordinating properties, revealed notable changes in all cases.